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Freshwater zooplankter Brachionus plicatilis is able to inhabit different habitats and locally adapt to their environmental conditions. It also shows a high degree of population structuring in small geographical regions. Here we try to shed light on the evolution of reproductive isolation in populations of B. plicatilis with presumptive gene flow among locally adapted populations. We have conducted laboratory experiments on admixed pairwise populations that differ in predictability of the water regime. We have assessed the potential for within-population reproductive preferences as a deviation of genotypes from Hardy–Weinberg equilibrium in diapausing eggs, a product of sexual reproduction. We expected heterozygote deficit to increase with environmental distance. We have found signs for incipient reproductive isolation in one third of our admixed populations, however no correlation with environmental distance was found, nor with genetic or geographic predictor variables. The overall inbreeding coefficient showed a tendency for within-population crosses preferences to decrease over time. [ABSTRACT FROM AUTHOR]

Differences in migratory behavior have been suggested to drive speciation, but the genetics underlying this process remain unknown. Identification and study of migratory divides can help us understand how differential migration can lead to reproductive isolation. Here, we genotyped Willow Warblers Phylloscopus trochilus, from the Åland islands, located in between the ranges of the differentially migrating subspecies P. t. trochilus and P. t. acredula. We found that Willow Warblers on the Åland islands were genetically intermediate to allopatric populations of both parental subspecies, providing evidence that the islands constitute a previously unknown hybrid swarm, likely to be a migratory divide. [ABSTRACT FROM AUTHOR]

Animals have a deep evolutionary relationship with microbial symbionts, such that individual microbes or an entire microbial community can diverge alongside the host. Here, we explore these host-microbe relationships in Echinometra, a sea urchin genus that speciated with the Isthmus of Panama and throughout the Indo-West Pacific. We find that the eggs from five Echinometra species generally associate with a species-specific bacterial community and that the relatedness of these communities is largely congruent with host phylogeny. Microbiome divergence per million years was higher in more recent speciation events than in older ones. We, however, did not find any bacterial groups that displayed co-phylogeny with Echinometra. Together, these findings suggest that the evolutionary relationship between Echinometra and their microbiota operates at the community level. We find no evidence suggesting that the associated microbiota is the evolutionary driver of Echinometra speciation. Instead, divergence between Echinometra and their microbiota is likely the byproduct of ecological, geographic, and reproductive isolations. [ABSTRACT FROM AUTHOR]

Trophic polymorphism and temporal reproductive isolation are the drivers of sympatric differentiation in many fish taxa. We present a new case of ecologically based diversification of Arctic charr in a Transbaikalian mountain lake inhabited by reproductively isolated dwarf and normal forms. These forms differ in size, diets and morphology and breed, respectively, in April–May and in September–October representing a rare example of sympatric spring- and autumn-spawning charr pair. Microsatellite analysis reveals clear-cut genetic differences and low-level hybridization between them. Dwarf form charr are planktivorous and manifest uniform slow growth. Normal form charr, though genetically homogeneous, are highly heterogeneous in size-at-age. They are subdivided into omnivorous small-size and piscivorous large-size groups, which can be considered as incipient forms at an early divergence stage. As evidenced by back-calculated growth data, their size-at-age heterogeneity results from highly variable individual growth patterns, which include different combinations of slow and fast growth periods presumably associated with spawning and non-spawning years. Growth acceleration in late ontogeny may result in the transformation of some normal charr from the smaller into the larger group during their lifetime. [ABSTRACT FROM AUTHOR]

The β′-component, a major allergen found in fish roe, is synthesized in the liver of female fish as part of the precursor of the egg yolk protein vitellogenin (Vg). Vg is distributed through the bloodstream and contributes to ovary development. In the present study, β′-component, present in Vg fragments, was detected in the muscles and internal organs of mature female salmon, with concentrations exceeding the recommended labeling level under Japan's food allergy labeling system. Additionally, total protein extracted from tissues of female salmon reacted with immunoglobulin E antibody against the salmon roe β′-component. No β′-component was detected in the tissues of mature male fish in the absence of sex hormone stimulation from females nor in immature salmon without sexual differentiation, but excess stimulation of the female sex hormone induced Vg synthesis containing the β′-component in the male fish. These findings suggest that taking into account fish sex, maturity, and sexual isolation of mature male fish could improve the safety of salmon meat for individuals with salmon roe allergy. [ABSTRACT FROM AUTHOR]

Bacterial species often comprise well-separated lineages, likely emerged and maintained by genetic isolation and/or ecological divergence. How these two evolutionary actors interact in the shaping of bacterial population structure is currently not fully understood. In this study, we investigate the genetic and ecological drivers underlying the evolution of Serratia marcescens, an opportunistic pathogen with high genomic flexibility and able to colonise diverse environments. Comparative genomic analyses reveal a population structure composed of five deeply-demarcated genetic clusters with open pan-genome but limited inter-cluster gene flow, partially explained by Restriction-Modification (R-M) systems incompatibility. Furthermore, a large-scale research on hundred-thousands metagenomic datasets reveals only a partial habitat separation of the clusters. Globally, two clusters only show a separate gene composition coherent with ecological adaptations. These results suggest that genetic isolation has preceded ecological adaptations in the shaping of the species diversity, an evolutionary scenario coherent with the Evolutionary Extended Synthesis. A large comparative genomics study reveals that Serratia marcescens is composed of five main phylogenetic clusters, isolated by genetic barriers but not clearly separated by ecological specialisations. This results provides insights into the bacterial diversification process. [ABSTRACT FROM AUTHOR]

Key message: Pollen tubes from closely related species and mutants lacking pollen tube MYB transcription factors are able to initiate FER/LRE-dependent synergid cell calcium oscillations. Reproductive isolation leads to the evolution of new species; however, the molecular mechanisms that maintain reproductive barriers between sympatric species are not well defined. In flowering plants, sperm cells are immotile and are delivered to female gametes by the pollen grain. After landing on the stigmatic surface, the pollen grain germinates a polarized extension, the pollen tube, into floral tissue. After growing via polar extension to the female gametes and shuttling its cargo of sperm cells through its cytoplasm, the pollen tube signals its arrival and identity to synergid cells that flank the egg. If signaling is successful, the pollen tube and receptive synergid cell burst, and sperm cells are released for fusion with female gametes. To better understand cell–cell recognition during reproduction and how reproductive barriers are maintained between closely related species, pollen tube-initiated synergid cell calcium ion dynamics were examined during interspecific crosses. It was observed that interspecific pollen tubes successfully trigger synergid cell calcium oscillations—a hallmark of reproductive success—but signaling fails downstream of key signaling genes and sperm are not released. This work further defines pollen tube–synergid cell signaling as a critical block to interspecific hybridization and suggests that the FERONIA/LORELEI signaling mechanism plays multiple parallel roles during pollen tube reception. [ABSTRACT FROM AUTHOR]

The cytogeography of the polyploid complex Bassia prostrata s. l. was studied by flow cytometry (FCM) on material from 39 populations in Armenia, Kazakhstan, and Russia. On the basis of the determination of the DNA content in the nuclei (2C-value), three cytotypes were identified: diploid (2n = 18), tetraploid (2n = 36), and hexaploid (2n = 54). Verification of the ploidy level determined by DNA content was carried out by parallel direct counting of the chromosome number. Most of the studied populations are represented by a single cytotype; in three populations, mixed ploidy is noted, when tetraploids or hexaploids are found along with diploids. The genetic isolation of chloroplast DNA of diploid and polyploid cytotypes was revealed. Presumable variants of the evolutionary relationship of cytotypes are shown on the basis of cpDNA restriction spectra. [ABSTRACT FROM AUTHOR]

Hybridization between species and the establishment of hybridization barriers can influence the diversification of species. Antarctic notothenioid fishes represent a prime example of marine adaptive radiation that diversified in the icy waters of Antarctica from an ancestral population that innovated antifreeze glycoproteins. The processes by which Antarctic notothenioid species evolved, however, remain elusive, and interspecific hybridization or the establishment of hybridization barriers between lineages may have influenced species diversification. To evaluate the current hybridization potential of notothenioids, we performed an experimental in vitro fertilization cross between two sympatric and congeneric notothen species using oocytes from the bullhead notothen Notothenia coriiceps and sperm from the marbled notothen N. rossii. Resulting embryos developed to late gastrula/early neurula stages and then suddenly died. Genetic analyses of embryos and parents demonstrated that the embryos lacked detectable paternal DNA and were thus gynogenetic. While premating barriers are likely to exist between the two species, this experiment suggests a strong postmating, prezygotic reproductive barrier preventing hybridization between the sister species due to gametic incompatibility in this directional cross. Our study provides novel information on mechanisms that may have contributed to the divergence and maintenance of these two ecologically important congeneric species. [ABSTRACT FROM AUTHOR]

The process of speciation generates biodiversity. According to the null model of speciation, barriers between populations arise in allopatry, where, prior to biology, geography imposes barriers to gene flow. On the other hand, sympatric speciation requires that the process of speciation happen in the absence of a geographical barrier, where the members of the population have no spatial, temporal barriers. Several attempts have been made to theoretically identify the conditions in which speciation can occur in sympatry. However, these efforts suffer from several limitations. We propose a model for sympatric speciation based on adaptation for resource utilization. We use a genetics-based model to investigate the relative roles of prezygotic and postzygotic barriers, from the context of ecological disruptive selection, sexual selection, and genetic architecture, in causing and maintaining sympatric speciation. Our results show that sexual selection that acts on secondary sexual traits does not play any role in the process of speciation in sympatry and that assortative mating based on an ecologically relevant trait forces the population to show an adaptive response. We also demonstrate that understanding the genetic architecture of the trait under ecological selection is very important and that it is not required for the strength of ecological disruptive selection to be very high in order for speciation to occur in sympatry. Our results provide an insight into the kind of scenarios in which sympatric speciation can be demonstrated in the lab. [ABSTRACT FROM AUTHOR]

Several barriers contribute to reproductive isolation between plant species, which can be classified as pre- or post-pollination. Understanding the strength of these barriers could clarify the factors that maintain reproductive isolation and thus species integrity. In this study, we quantified reproductive isolation between two bat-pollinated co-occurring Bauhinia species (B. acuruana and B. pentandra) with similar flower morphology. Over the course of 18 months, we assessed reproductive isolation between these two Bauhinia species by quantifying the individual strengths and absolute contributions of five pre- and post- pollination barriers. Our data showed that both species are completely isolated in their reproduction by a combination of several barriers. Although they co-occur in a few populations, we found a high degree of geographic isolation between them. And although their flowering periods overlap, there is a significant difference in flowering peaks. Both species have the same pollinating bats, but the interspecific transfer of pollen between the plant species may be reduced due to the different length of the flower stamens, resulting in different pollen deposition on the bats' bodies. We have documented complete incompatibility between taxa and conclude that pre- and post-pollination barriers are important factors in preventing gene flow, even in contact zones between these two species of Bauhinia. We highlight that our work is the first study to use methods to estimate the strength of reproductive isolation barriers between bat-pollinated species. [ABSTRACT FROM AUTHOR]

The South American Tern Sterna hirundinacea is a poorly known migratory seabird distributed along South American marine coasts, including the Falkland Islands (Malvinas). The species presents allochronic isolation (i.e., separation of populations by breeding time), with different populations occupying different environmental spaces during the reproductive periods. Additionally, southern populations appear to undertake long-distance directional migration, but there is limited knowledge of the migratory behaviour of northern populations. In spite of these temporal and spatial segregative behaviour, limited population structure has been inferred from genetic assessments, although only a few localities have been investigated. Morphological variation is also poorly known. Whether intrinsic, environmental, or anthropogenic factors are causing isolation and differentiation between populations is unknown. Here, we first characterize sexual morphological dimorphism in the South American Tern, and then evaluate morphological variation along the species range, using only measurements that did not respond to sexual dimorphism and with a representative number of specimens. We also evaluate genetic variation along the South American Tern distribution to test for population differentiation and estimate the demographic history and diversification time for the species. Overall, we found limited population structure in both morphological and genetic data, but with some differentiation in measurements assessed for specimens from the Southeastern Pacific. A trend for demographic stability after a population expansion was estimated for the species. The connectivity among species' colonies, followed by its likely non-philopatric behaviour, seems to maintain gene flow between South American Tern populations. However, genetic differentiation might still be undetected, given the estimated recent origin and demographic expansion for the species. Although the South American Tern is not considered globally threatened, it is regionally threatened, and conservation implications of our findings are considered. [ABSTRACT FROM AUTHOR]

Using 11 microsatellite markers (OarCP49, INRA063, HSC, OarAE129, MAF214, OarFCB11, INRA005, SPS113, INRA23, MAF65, and McM527), data on the level of variability and degree of differentiation of 24 populations (1140 specimens) of Tuvan coarse-wooled short fat-tailed sheep from different regions of the Republic of Tyva and 24 sheep breeds (721 specimens) of different origin from the main sheep-raising regions of the Russian Federation, were obtained. The analysis revealed the high level of genetic isolation and variability of Tuvan sheep. Moreover, in the general structure of Russian sheep breeds, pronounced genetic divergence into two large groups was revealed, with one of these groups uniting fine-fleeced and semi-fine-fleeced sheep, and the other group consisting of indigenous coarse-wooled breeds of North Caucasian and Asian origin. [ABSTRACT FROM AUTHOR]

The genetic and morphological variability of the southern form of the European chromosomal variety of the Ural field mouse Apodemus (Sylvaemus) uralensis (Pallas, 1811) in the North Caucasus was studied. The results of the sequence analysis of the cytochrome b gene fragment from nine geographical samples from the western, central, and eastern parts of the North Caucasus indicate a low degree of their genetic isolation with a relatively high diversity of haplotypes. Analysis of the morphological variability revealed high variety: three morphological groups were identified. Representatives of all three or two groups were found in the same geographical samples, but their distribution did not conform to the hypothesis of random occurrence. Based on indirect evidence, hypotheses about possible causes of the observed features of regional Ural field mouse biodiversity are formulated, which require verification in the course of future studies. In particular, we hypothesized that in the Late Pleistocene (130 000–11 700 cal years BP) there were several isolated populations in the region that could have been sources of species diversity in the Holocene. [ABSTRACT FROM AUTHOR]

The advent of molecular techniques has resulted in the discovery of previously unknown cryptic species in many organisms, including rotifers, allowing researchers to perform detailed tests on reproductive barriers between closely related taxa. Here, we review the available literature about molecular techniques implemented for detecting cryptic diversity in rotifers and delimiting species, and discuss the potential mechanisms of reproductive isolation among rotifer cryptic species. Half of the evaluated studies used quantitative statistical approaches for species delimitation. Species boundaries defined by molecular approaches were also examined by conducting mating experiments. Those mating experiments were used to test various reproductive barriers. Most (75%) studies that identified reproductive isolation mechanisms provided evidence of prezygotic barriers. The available literatures suggest that behavioral reproductive isolation may have a more important role than other prezygotic barriers in facilitating reproductive isolation. Postzygotic barriers such as hybrid unviability or sterility and female mortality also contribute to reproductive isolation among rotifer cryptic species. The prevalence of prezygotic barriers in our assessment may stem from the difficulty of studying postzygotic barriers, which can require long-term maintaining and monitoring of rotifer populations. Sequencing tools, including whole genome sequencing, could be implemented to investigate the molecular basis of reproductive isolation in rotifers. [ABSTRACT FROM AUTHOR]

In this paper, we present the first results of complex geological and geophysical studies of active tectonics in the northeast of Taymyr that were carried out during the expedition of the Northern Fleet and the Russian Geographical Society in 2020. At the foot of the Byrranga Mountains, a wide zone of active fault-folded tectonic deformations was identified and studied. The general kinematics of displacements is reverse-thrust with signs of shear. The structural style of young tectonic deformations bears a direct resemblance to well-studied structural analogues of the Central Asian seismic belt. The Taymyr seismotectonic zone reveals both spatial and genetic isolation. It has an individual model of the Late Cenozoic geodynamic evolution and modern seismotectonic regime, which differs sharply from the Laptev Sea rift zone adjacent to the east. A complex of geological and geophysical methods showed the high efficiency of application in the Arctic to identify young fault-fold structures, which are potential sources of strong earthquakes. [ABSTRACT FROM AUTHOR]

Quantifying patterns of gene flow is critical for predicting the future resilience of local marine communities. Brooding species may be particularly susceptible to extirpation, as the lack of a pelagic larval phase may limit dispersal capacity and increase the risk of local extinction. Here, we investigate the population genetic structure of Leptasterias sp., a brooding sea star and important intertidal predator. Dispersal in this genus occurs primarily by crawling, but some have suggested that occasional "rafting" events can move individuals long distances. We used microsatellite markers to estimate genotypic variation across six collection sites of varying distances apart along the Oregon coast. We found evidence of strong population structure at the level of capes, and especially high divergence between two sites within Cape Blanco. Although cape-level genetic structure is broadly consistent with isolation-by-distance, additional mechanisms may be required to explain the elevated magnitude of genetic divergence on a finer scale. We propose that a known offshore water jet off Cape Blanco may act as phylogeographic barrier, hindering transport of rafting individuals from neighboring sites. This pattern suggests, indirectly, that rafting may be more important than previously appreciated in generating long-term genetic isolation between nearby sites. Our findings suggest that even for a sessile brooding species, connectivity and genetic structure can vary on a fine spatial scale and may be subject to environmental and oceanographic forces. [ABSTRACT FROM AUTHOR]

Ecological diversification of Sebastes rockfishes has been mainly driven by depth and resource availability. Both ecological parameters exert selective pressures in colouration, communication systems, body, otolith shape, and prey–predation interactions. Accordingly, we hypothesized that ecomorphological divergences found in these components can reflect reduced interspecific competition among three rockfishes from the same species complex with sympatric occurrence in Seto Inland Sea (Japan). The narrower body shape and golden-brown colouration in Sebastes cheni suggest a more pelagic lifestyle than the other two species. Larger eye and otolith relative sizes, deeper body shape and red colouration suggest a deeper distribution for Sebastes inermis, in concordance with longer pectoral fins and dorsal spines to deal with increased foraging difficulty and predation risk because of its colouration. Meanwhile, smaller upper jaws, higher number of gill rakers, and black colouration of Sebastes ventricosus indicate a shallower distribution than S. inermis and preference for planktonic preys. Differences in colouration, eye size, and otolith descriptors support species-specific communication systems that are crucial to maintaining reproductive isolation. Therefore, the morphological divergences among these rockfishes reflect specific ecological divergences that allow their coexistence in sympatry and can ease their morphological identification. [ABSTRACT FROM AUTHOR]

Hybridization—the interbreeding of different species—plays an integral role in the evolution of numerous bird species. However, it remains unclear how widespread this phenomenon is within and across different bird groups. Estimating the incidence of hybridization in different bird lineages can inform comparative analyses to uncover the evolutionary and ecological forces that promote or prevent the formation of hybrids. Estimates on a species level have varied from about 10% to almost 20% of hybridizing bird species. The variation among the latest estimates largely depends on the choice of global species checklists with differing decisions on the taxonomic status of certain (sub)species. However, the hybrid records in these estimates have generally been taken at face value. Detailed assessments of these records revealed that some cases are unreliable or incorrect. Removing of these faulty records and discovery of novel hybrids will result in a fluctuating percentage of hybridizing species that can best be captured in a living document (e.g., a regularly updated website or checklist). Estimating hybridization on an individual level is more challenging. A first attempt, using citizen science data from the eBird project, reported 0.064% hybrid individuals in the United States. This percentage is probably an underestimate due to underreporting of hybrids by birdwatchers and remains to be finetuned by considering other confounding factors, such as spatial and temporal variation in hybridization dynamics. Future efforts in estimating avian hybridization will need to rely on a combination of data sources and techniques, such as genetics, museum specimens, and citizen science. [ABSTRACT FROM AUTHOR]

Annual killifish have an annual life cycle unique among vertebrates. Adults lay desiccation-resistant eggs in the soil of the temporary pools they inhabit. Courtship behavior of some Neotropical killifish consists of a series of displays performed by males and females that ends in the total or partial burial of the couple. However, little information exists on their reproductive isolation mechanisms, including a detailed analysis of courtship signals. In this study, we analyzed the courtship behavior of a Neotropical annual killifish (Austrolebias nigripinnis) within a comparative frame. The most frequent units in males were lateral (44%) and sigmoid displays (26%), where males exhibit morphological and color patterns to females. Females showed a high frequency (44%) of quiescence, suggesting that this unit may have an evaluative role during courtship. Behavioral units recognized in this species show some differences with other related species (i.e., Austrolebias affinis), mainly in frequency and duration, but also in sequence. Although the results of this work cannot determine if these differences constitute reproductive isolation mechanisms, it provides fundamental elements to try to establish kinship relationships and solve the complexity implicit in the definition of species. [ABSTRACT FROM AUTHOR]

This article examines how isolation and the seasonality of employment both constrain and enable agricultural guest workers' contact with outsiders. While the H-2A visa program can render foreign workers invisible and immobile—and thus more easily exploited and mistreated—a group of temporary Mexican apple pickers in northwest Virginia generated resources, transportation, and assistance well beyond what was provided by the company or mandated by visa protocol. The conditions and processes highlighted in this study provide a framework for identifying factors that may diminish—or enhance—the relative autonomy of guest workers. In this case, a history of return migration and the presence of co-ethnics in the settled population generated an unexpected flow of activity in and out of the remote camp. While not automatic or without limitations, these connections provided a more open and dynamic guest-worker experience than what a singular focus on isolation and exclusion would otherwise suggest. [ABSTRACT FROM AUTHOR]

Comprehending bacterial genomic variation linked to distinct environments can yield novel insights into mechanisms underlying differential adaptation and transmission of microbes across environments. Gaining such insights is particularly crucial for pathogens as it benefits public health surveillance. However, the understanding of bacterial genomic variation is limited by a scarcity of investigations in genomic variation coupled with different ecological contexts. To address this limitation, we focused on Listeria, an important bacterial genus for food safety that includes the human pathogen L. monocytogenes, and analyzed a large-scale genomic dataset collected by us from natural and food-associated environments across the United States. Through comparative genomics analyses on 449 isolates from the soil and 390 isolates from agricultural water and produce processing facilities representing L. monocytogenes, L. seeligeri, L. innocua, and L. welshimeri, we find that the genomic profiles strongly differ by environments within each species. This is supported by the environment-associated subclades and differential presence of plasmids, stress islands, and accessory genes involved in cell envelope biogenesis and carbohydrate transport and metabolism. Core genomes of Listeria species are also strongly associated with environments and can accurately predict isolation sources at the lineage level in L. monocytogenes using machine learning. We find that the large environment-associated genomic variation in Listeria appears to be jointly driven by soil property, climate, land use, and accompanying bacterial species, chiefly representing Actinobacteria and Proteobacteria. Collectively, our data suggest that populations of Listeria species have genetically adapted to different environments, which may limit their transmission from natural to food-associated environments. [ABSTRACT FROM AUTHOR]

We studied an aggregation of Apis laboriosa colonies in northern Vietnam where the species is sympatric with Apis dorsata. We video-recorded four colonies on 2 days to quantify drone flights and other colony behaviors. We observed > 90% of drones between 16:10 and 18:10 h ICT, with the maximum numbers between ~ 17:10 and 18:00 h. Drone flight timing did not differ between days or between colonies. Aggressive worker behavior toward some arriving drones suggests considerable drifting of drones between nests. Massed flight activity, a colony behavior in which a high proportion of bees temporarily leaves the comb, occurred in several colonies between 14:00 and 16:40 h. We also documented absconding by one colony. A. laboriosa drones ended their mating flights before the typical mating flight time of Apis dorsata at evening twilight. We conclude that allochrony of mating is a likely reproductive isolating mechanism between these two species of giant honey bees. [ABSTRACT FROM AUTHOR]

Hybrid zones can be used to identify traits that maintain reproductive isolation and contribute to speciation. Cognitive traits may serve as post-mating reproductive isolating barriers, reducing the fitness of hybrids if, for example, misexpression occurs in hybrids and disrupts important neurological mechanisms. We tested this hypothesis in a hybrid zone between two subspecies of Swainson's thrushes (Catharus ustulatus) using two cognitive tests—an associative learning spatial test and neophobia test. We included comparisons across the sexes and seasons (spring migration and winter), testing if hybrid females performed worse than males (as per Haldane's rule) and if birds (regardless of ancestry or sex) performed better during migration, when they are building navigational maps and encountering new environments. We documented reduced cognitive abilities in hybrids, but this result was limited to males and winter. Hybrid females did not perform worse than males in either season. Although season was a significant predictor of performance, contrary to our prediction, all birds learned faster during the winter. The hypothesis that cognitive traits could serve as post-mating isolating barriers is relatively new; this is one of the first tests in a natural hybrid zone and non-food-caching species. We also provide one of the first comparisons of cognitive abilities between seasons. Future neurostructural and neurophysiological work should be used to examine mechanisms underlying our behavioral observations. [ABSTRACT FROM AUTHOR]

Hybridization between milky stork (Mycteria cinerea) and painted stork (M. leucocephala) occurs frequently in captivity. Dusit Zoo is a captive breeding facility where storks with phenotypically ambiguous patterns have recently been observed, and their status remaining inconclusive. Here, we used a combination of phenotypic characters and genetic markers (cytochrome b and 14 microsatellite markers) to distinguish and identify hybrids from the two parental species (n = 114). Haplotype analysis revealed asymmetric mtDNA introgression from M. cinerea to M. leucocephala, with twelve morphologically classified M. leucocephala individuals carrying heterospecific mtDNA. Comprehensive biparental genetic assessments identified 33% of all three genetic clusters as admixed individuals, of which most were either F2 hybrids, backcrosses with M. leucocephala, or hybrids of unknown generation, implying weak premating isolation with the absence of intrinsic postzygotic isolation between parentals. Morphological analysis demonstrated that the absence or indistinctness of a black bar across the breast is the most noticeable trait to identify these hybrids. The endangered M. cinerea was found to have genomic contamination from M. leucocephala and vice versa, with at least 41 hybrid individuals being identified. These findings provide critical information for detecting hybrids and identifying suitable breeding stocks with genetic purity for future reintroduction and conservation management. [ABSTRACT FROM AUTHOR]

The systematics of the Old World Spiranthes sinensis (Pers.) Ames species complex (Orchidaceae) has been complicated by its wide distribution and morphological variations. Within the species complex, S. australis Lindl. has been generally accepted as the only Spiranthes Rich. species distributed on the Japanese mainland. The present study provides morphological, phylogenetic, and ecological evidence for the recognition of S. hachijoensis Suetsugu as a new species of the S. sinensis species complex on the Japanese mainland. Spiranthes hachijoensis is morphologically similar to S. hongkongensis S.Y. Hu & Barretto and S. nivea T.P. Lin & W.M. Lin, sharing a degenerated rostellum, pollinia without a viscidium, and distinctly trilobed stigma. However, the taxon can be morphologically distinguished from S. hongkongensis by its glabrous rachis, ovaries, and sepals, and from S. nivea by its papillate labellum disc, larger papillate basal labellum callosities, and glabrous rachis, ovaries, and sepals. The autogamy and flowering phenology (i.e., earlier flowering) of S. hachijoensis are most likely responsible for premating isolation from the sympatric S. australis. A MIG-seq-based high-throughput molecular analysis indicated that the genetic difference between S. hachijoensis and its putative sister species S. sinensis is comparable to, or even greater than, the genetic difference between pairs of other species within the S. sinensis species complex. Our multifaceted approach strongly supports the recognition of S. hachijoensis as a morphologically, phenologically, phylogenetically, and ecologically distinct species. [ABSTRACT FROM AUTHOR]

In angiosperms, intraspecific variation of flowering phenology may affect reproductive isolation and, consequently, speciation. This study focused on Impatiens noli-tangere (Balsaminaceae), which is distributed over broad latitudinal and altitudinal ranges in Japan. We aimed to reveal the phenotypic mixture of two ecotypes of I. noli-tangere with different flowering phenology and morphological traits in a narrow contact zone. Previous studies have shown that I. noli-tangere has early- and late-flowering types. The early-flowering type makes buds in June and is distributed at high-elevation sites. The late-flowering type makes buds in July and is distributed at low-elevation sites. In this study, we analyzed the flowering phenology of individuals at an intermediate elevation site where the early- and late-flowering types grow in sympatry (contact zone). We found no individuals showing intermediate flowering phenology at the contact zone, and early- and late-flowering types were clearly distinguishable. We also found that the differences in many other phenotypic traits between the early- and late-flowering types were maintained, including the number of flowers produced (total number of chasmogamous and cleistogamous flowers), leaf morphology (aspect ratio, number of serrations), seed traits (aspect ratio), and flower bud formation positions on the plant. This study showed that these two flowering ecotypes maintain many different traits in sympatry. [ABSTRACT FROM AUTHOR]

Migratory diversity can promote population differentiation if sympatric phenotypes become temporally, spatially, or behaviorally segregated during breeding. In this study, the potential for spatiotemporal segregation was tested among three migratory phenotypes of lake sturgeon (Acipenser fulvescens) that spawn in the St. Clair River of North America's Laurentian Great Lakes but differ in how often they migrate into the river and in which direction they move after spawning. Acoustic telemetry over 9 years monitored use of two major spawning sites by lake sturgeon that moved north to overwinter in Lake Huron or south to overwinter in Lake St. Clair. Lake St. Clair migrants were further distinguished by whether they migrated into the St. Clair River each year (annual migrants) or intermittently (intermittent migrants). Social network analyses indicated lake sturgeon generally co-occurred with individuals of the same migratory phenotype more often than with different migratory phenotypes. A direct test for differences in space use revealed one site was almost exclusively visited by Lake St. Clair migrants whereas the other site was visited by Lake Huron migrants, intermittent Lake St. Clair migrants, and, to a lesser extent, annual Lake St. Clair migrants. Analysis of arrival and departure dates indicated opportunity for co-occurrence at the site visited by all phenotypes but showed Lake Huron migrants arrived approximately 2 weeks before Lake St. Clair migrants. Taken together, our results indicated partial spatiotemporal segregation of migratory phenotypes that may generate assortative mating and promote population differentiation. [ABSTRACT FROM AUTHOR]

The seven-spotted ladybug is a widespread species in the Palearctic, and also acclimated in the Nearctic. It has been classified into different species on the basis of certain morphological characteristics, the geographical origin, and the genitalia structure of both sexes. The morphotypes of North Africa and the Canary Islands are separated, under the name of Coccinella algerica Kovář, 1977, from the rest of the Palearctic and Nearctic populations of Coccinella septempunctata Linnaeus, 1758. In this study, we investigated, on one hand, whether potential reproductive barriers have been established during evolution between the geographically isolated North African and the European seven-spotted ladybugs by performing reciprocal crosses. On the other hand, we assessed their cuticular hydrocarbon (CHC) divergence by GC–MS. The 33 CHCs indentified are with a skeleton of 23 to 32 carbon atoms. These CHCs are linear alkanes (24.9 ± 3.6%) and methyl-branched alkanes (75.1 ± 3.6%) including monomethylalkanes (48.8 ± 2.4%), dimethylalkanes (24.6 ± 4.0%) and trimethylalkanes (2.0 ± 1.0%). Although all the CHC compounds identified are present in the two seven-spotted ladybugs and their F1 and F2 hybrids, their profiles diverged significantly. However, these chemical divergences have not altered the sexual communication to cause reproductive isolation. The two ladybugs interbreed and leave viable and fertile offspring, with even a heterosis effect on reproductive performances, without phenotypic degradation after the F1 generation. So, these chemical differences are just an intraspecific variability in response to heterogeneous environments. The two types of ladybugs can be considered as two different races of the same species with reduced genetic divergence. [ABSTRACT FROM AUTHOR]

Corunastylis species produce some of the smallest, fly-pollinated flowers of Australian orchids to offer liquid rewards. We observed and collected pollinarium vectors of four Corunastylis species (C. filiformis, C. fimbriata, C. rufa and C. ruppii) with overlapping flowering periods during the summer–autumn months at five sites in New South Wales (NSW), Australia. The most common pollinarium vectors of all species were females of a single morphotype in the genus Conioscinella (Diptera: Chloropidae). This morphotype was less than 3 mm in length and carried dorsal depositions of pollinaria on its thorax. A chloropid could carry as many as two pollinaria and 25–50% of attached pollinia showed erosion, suggesting previous contact with receptive stigmas. Bagging experiments on three species showed low rates of mechanical self-pollination and no fruit set in C. filiformis, C. fimbriata and C. ruppii. The conversion rate of insect-pollinated flowers into fruit varied from 35 to 91% among these three species in NSW versus C. ciliata in Victoria. Seed development also varied with > 42–70% of seeds in the three species in NSW containing fully developed embryos. High levels of reproductive success in these three species in NSW and C. ciliata in Victoria were the same as for fruit sets in other orchid species in other genera with nectar-secreting flowers. As flowering periods, distributions and primary pollinators of four Corunastylis species in NSW overlapped so broadly there appears to be a lack of pre-zygotic interspecific isolation mechanisms. This study provided important pollination and reproductive information towards future conservation management of these orchid species. [ABSTRACT FROM AUTHOR]

The genetic relatedness of yeasts in the Saccharomyces bayanus complex has been studied using the methods of molecular and classical genetics. A divergent population of S. bayanus has been found in New Zealand and Australia. The S. bayanus complex includes four genetic populations: S. bayanus var. bayanus, S. bayanus var. uvarum, S. eubayanus, and the New Zealand population. The strains of the New Zealand population differ significantly in the nucleotide sequences of the nuclear (FSY1, HIS3, MET2) and mitochondrial (FUN14, COX2) genes and form semi-sterile hybrids with other populations: the viability of ascospores is 6.2–23.3%. There is no complete interspecific postzygotic isolation among S. bayanus var. bayanus, S. bayanus var. uvarum, S. eubayanus, and the New Zealand populations: all hybrids showed regular meiotic segregation of the control auxotrophic markers. According to the results obtained, the four genetic populations belong to the same biological species with genomic divergence at the level of taxonomic varieties. [ABSTRACT FROM AUTHOR]

The paper is devoted to computational modeling of biophysical processes with factors of heterogeneous adaptation. Plasticity and variability is the basis of evolution in natural biophysical systems. The complex of behavioral and biochemical adaptations allows the ancient populations of the Caspian Sea to efficiently use the limited resources and withstand the competition. During long-term simultaneous evolution in populations of Caspian organisms, a specific adaptation has appeared that is the strategy of survival optimal for physical conditions of the Caspian Sea. Interference in the existing hydrological systems of the region instantaneously deteriorated the advantages of the evolution strategy. An important form of adaptation for the Caspian Sea is the formation of subpopulation reproductively isolated groups that become units of species formation, accumulating the differences because of the reproductive isolation. In the paper we describe the method for analyzing the intrapopulation structure, where the groups with different reproductive behavior arose in the population. This is an aspect of the technical problem of the method for their introduction. A modified method of antigen differentiation developed by Yu.N. Perevaryukha (patent for invention RU 2253970) allowed determining the belonging of animal units to one of the reproductive groups of marine sturgeons by the differences in their antigens in the blood serum. It was shown that biophysical adaptation to long-term life in sweet water reflects in the presence in blood of specific proteins called the antigen markers. Immunochemical technologies immunodiffusion and electrophoresis are applied to study the markers of reproductive groups of Caspian sturgeons. The knowledge about the character of life cycle of groups isolated by their reproductive behavior and optimal temperature is necessary for artificial recovery of the populations. The data on the presence of two reproductive groups in starry sturgeon Acipencer stellatus are used to model the reproductive activity of the population. The information about the degree of intrapopulation differentiation allows improving the hybrid computational structure for the model of biophysical processes requiring the animal unit introduction technology; this structure was earlier proposed by us in Technical Physics. The model scenario explains the low efficiency of artificial release of sturgeon fish in the Caspian Sea. The procedure for reintroduction of sturgeons into the Caspian Sea must take into account the reproductive peculiarities of groups with different behavior. The considered problem is topical not only for populations of the Volga basin, but also for local populations in southern waters of the Caspian Sea of Iran and Azerbaijan. [ABSTRACT FROM AUTHOR]

Mitochondrial content has been reported outside of cells either within extracellular vesicles (EVs) or as free mitochondria. Mitochondrial EVs can potentially play multiple physiological and pathophysiological roles. To understand their functions, isolation protocols to separate mitochondrial EVs from other mitochondrial content need to be established. In the present work, we use a multiple reaction monitoring assay with isotope labeled internal standards to quantify 11 mitochondrial, 6 plasma membrane-specific, 4 endosomal membrane-specific, and 2 soluble proteins to evaluate the efficiency of chromatographic isolation of mitochondrial EVs. The isolation protocol includes ultracentrifugation, size exclusion chromatography, and chromatography on immobilized heparin. All protein concentrations were normalized to the concentration of ATP synthase alpha subunit to generate a ratio that allows comparison of different samples obtained during the isolation. We have shown that initial samples after ultracentrifugation are contaminated with non-EV mitochondrial content that cannot be separated from EVs using size exclusion chromatography, but can be efficiently separated from EVs on the column with immobilized heparin. [ABSTRACT FROM AUTHOR]

Natural hybrid zones provide powerful opportunities for identifying the mechanisms that facilitate and inhibit speciation. Documenting the extent of genomic admixture allows us to discern the architecture of reproductive isolation through the identification of isolating barriers. This approach is particularly powerful for characterizing the accumulation of isolating barriers in systems exhibiting varying levels of genomic divergence. Here, we use a hybrid zone between two species—the Baltimore (Icterus galbula) and Bullock's (I. bullockii) orioles—to investigate this architecture of reproductive isolation. We combine whole genome re-sequencing with data from an additional 313 individuals amplityped at ancestry-informative markers to characterize fine-scale patterns of admixture, and to quantify links between genes and the plumage traits. On a genome-wide scale, we document several putative barriers to reproduction, including elevated peaks of divergence above a generally high genomic baseline, a large putative inversion on the Z chromosome, and complex interactions between melanogenesis-pathway candidate genes. Concordant and coincident clines for these different genomic regions further suggest the coupling of pre- and post-mating barriers. Our findings of complex and coupled interactions between pre- and post-mating barriers suggest a relatively rapid accumulation of barriers between these species, and they demonstrate the complexities of the speciation process. Genome-wide analyses of admixture between two closely related and sympatric North American oriole species reveals longstanding barriers enforcing reproductive isolation. [ABSTRACT FROM AUTHOR]

The banded krait, Bungarusfasciatus is a widespread elapid snake, likely to comprise several distinct species in different geographic regions of Asia. Therefore, based on molecular phylogenetics and comparative morphology data, we present an overview of the systematic composition of the species to delimit potential biogeographic boundaries. Our phylogenetic analyses, based on four mitochondrial genes, reveal the existence of at least three evolutionary lineages within B.fasciatus, corresponding to Indo-Myanmar, Sundaic and eastern Asian lineages. We are convinced that there are at least three taxonomic entities within the nomen B.fasciatus and restrict the distribution of B.fasciatus sensu stricto to the Indo-Myanmar region. We also provide additional natural history data of the taxon from eastern India. Finally, we advocate further studies to establish the degree of reproductive isolation among these diverging evolutionary lineages and to reassess the systematic status of this species complex especially the Sundaic and eastern Asian lineages. [ABSTRACT FROM AUTHOR]

Divergence in floral traits attractive to different pollinators can promote reproductive isolation in related species. When isolation is incomplete, hybridization may occur, which offers the opportunity to explore mechanisms underlying reproductive isolation. Recent work suggests that divergence in floral scent may frequently contribute to reproductive barriers, although such divergence has seldom been examined in species with generalized pollination. Here, we used two closely related Penstemon species, P. newberryi and P. davidsonii, and their natural hybrids from an elevational gradient with pollinator communities that are predicted to vary in their reliance on floral scent (i.e., primarily hummingbirds at low elevation vs. bees at high elevation). The species vary in a suite of floral traits, but scent is uncharacterized. To address whether scent varies along elevation and potentially contributes to reproductive isolation, we genetically characterized individuals collected at field and identified whether they were parental species or hybrids. We then characterized scent amount and composition. Although the parental species had similar total emissions, some scent characteristics (i.e., scent composition, aromatic emission) diverged between them and may contribute to their isolation. However, the species emitted similar compound sets which could explain hybridization in the contact area. Hybrids were similar to the parents for most scent traits, suggesting that their floral scent would not provide a strong barrier to backcrossing. Our study suggests floral scent may be a trait contributing to species boundaries even in plants with generalized pollination, and reinforces the idea that evolutionary pollinator transitions may involve changes in multiple floral traits. [ABSTRACT FROM AUTHOR]

Due to their reduced morphology, non-photosynthetic plants have been one of the most challenging groups to delimit to species level. The mycoheterotrophic genus Monotropastrum, with the monotypic species M. humile, has been a particularly taxonomically challenging group, owing to its highly reduced vegetative and root morphology. Using integrative species delimitation, we have focused on Japanese Monotropastrum, with a special focus on an unknown taxon with rosy pink petals and sepals. We investigated its flowering phenology, morphology, molecular identity, and associated fungi. Detailed morphological investigation has indicated that it can be distinguished from M. humile by its rosy pink tepals and sepals that are generally more numerous, elliptic, and constantly appressed to the petals throughout its flowering period, and by its obscure root balls that are unified with the surrounding soil, with root tips that hardly protrude. Based on genome-wide single-nucleotide polymorphisms, molecular data has provided clear genetic differentiation between this unknown taxon and M. humile. Monotropastrum humile and this taxon are associated with different Russula lineages, even when they are sympatric. Based on this multifaceted evidence, we describe this unknown taxon as the new species M. kirishimense. Assortative mating resulting from phenological differences has likely contributed to the persistent sympatry between these two species, with distinct mycorrhizal specificity. [ABSTRACT FROM AUTHOR]

Divergence in sperm phenotype and female reproductive environment may be a common source of postmating prezygotic (PMPZ) isolation between species. However, compared to other reproductive barriers it has received much less attention. In this study, we examined sperm morphology and velocity in two hybridizing passerine species, the common nightingale (Luscinia megarhynchos) and thrush nightingale (L. luscinia). In addition, we for the first time characterized a passerine female reproductive tract fluid proteome. We demonstrate that spermatozoa of the common nightingale have significantly longer and wider midpiece (proximal part of the flagellum containing mitochondria) and longer tail compared to spermatozoa of thrush nightingale. On the other hand, they have significantly shorter and narrower acrosome. Importantly, these differences did not have any effect on sperm velocity. Furthermore, the fluid from the reproductive tract of common nightingale females did not differentially affect velocity of conspecific and heterospecific sperm. Our results indicate that the observed changes in the flagellum and acrosome size are unlikely to contribute to PMPZ isolation through differential sperm velocity of conspecific and heterospecific sperm in the female reproductive tract. However, they could affect other postcopulatory processes, which might be involved in PMPZ isolation, such as sperm storage, longevity or sperm-egg interaction. [ABSTRACT FROM AUTHOR]

Circumpolar variations in the size and shape of the skull in the Arctic fox Vulpes lagopus L. 1758 was studied based on 31 linear measurements of 326 specimens. The specimens were collected from the mainland parts of North America and Eurasia, as well as from several islands within the native range of the Arctic fox, namely, Greenland, Iceland, Svalbard, St. Lawrence Island, St. Matthew Island, Pribilof Islands (St. Paul Island and St. George Island), and Commander Islands (Bering Island and Mednyi Island). A specimen from the Arctic fox populations introduced to the Atka Island and Aleutian Islands was also included in the analysis. Morphological circumpolar variations in the skull of Arctic foxes observed in the present study were compared to the genetic variations reported in earlier studies. No significant differences were observed in cranial size and shape between Arctic foxes from the mainland (both North American and Eurasian populations) and those from St. Lawrence Island, St. Matthew Island, Svalbard, and Iceland. Although the Greenland foxes were significantly smaller than the mainland ones, their cranial shape was comparable. Based on the skull shape, the Commander Islands' Arctic foxes were the most distinct among all populations. An unsupervised model-based cluster analysis implemented in MCLUST showed that, based on cranial morphology, the Commander Islands' Arctic foxes could be differentiated from the other Arctic foxes with a high level of probability (p ≥ 0.95). The morphological specificity of the Commander Islands' Arctic foxes is congruous with their genetic isolation. The morphological specificity of Greenland and Pribilof Island Arctic foxes was greater than their genetic distinctiveness. A taxonomic revision of the study species was performed based on the data presented. The Arctic foxes from the mainland parts of North America and Eurasia, St. Lawrence Island, St. Matthew Island, Svalbard, and Iceland were classified under a single nominotypical subspecies, V. l. lagopus L. 1758, while the Greenland Arctic foxes belong to a separate small subspecies of the mainland Arctic fox, namely, V. l. groenlandicus Bechstein 1799. Similarly, the Pribilof Arctic foxes V. l. pribilofensis Merriam 1903 are subspecies of the mainland animal and further should be divided into two separate subspecies, one from St. Paul Island and another from St. George Island, taking into account the level of their morphological differences, Based on marked morphological and genetic differences, the Commander Islands' Arctic foxes were reclassified as a distinct species, V. beringensis Merriam 1902, as proposed by Ognev (1931), with two subspecies, namely, V. b. beringensis Merriam 1902 from Bering Island and V. b. semenovi Ognev 1931 from the Mednyi Island. The specimen from Atka Island was identified to the species from the Commander Islands, suggesting that the Arctic fox population on Atka Island must have been introduced from the Commander Islands. Given the declining population of the Arctic foxes on the Commander Islands, this data is important for the environmental and genetic conservation of the Commander Islands' Arctic fox [ABSTRACT FROM AUTHOR]

Zones of secondary contact provide a good opportunity to investigate the origin and dynamics of reproductive isolation between related populations. We analyzed genetic and phenotypic patterns and gene flow between two subspecies of the Eurasian magpie Pica pica s.l. which recently came into contact after presumably long periods of isolation. We describe the distribution of subspecies in a young contact zone at Argun' river basin in southern Siberia where populations occur in parapatry and an older hybrid population in eastern Mongolia. Based on genome-wide SNP data, we analyzed patterns and strength of gene flow between the subspecies. Our results indicate occasional hybridization with backcrossing and asymmetric introgression along a wide range in Transbaikalia and locally in eastern Mongolia. Males of P. p. jankowskii apparently exhibit higher dispersal ability towards the west compared to P. p. leucoptera (towards the east). The former occasionally migrates to eastern Mongolia and Transbaikalia where introgression of nuclear, but not mitochondrial DNA was evident. Bioacoustic investigations showed differences between the subspecies in speed and structure of vocalization. We discovered intermediate calls of hybrid magpies and bilingual birds alternating calls that are typical for the two taxa. Furthermore, we found dramatically decreased reproductive success in hybridogeneous populations. By complementing our results with established phylogeographic patterns of P. pica s.l. based on a mitochondrial marker sequence, and considering indications of sterility of hybrids in the contact zone, we propose to elevate the two corresponding subspecies to species level: P. pica for the western form and P. serica for the eastern form. [ABSTRACT FROM AUTHOR]

Appendicularian tunicates are some of the most abundant mesozooplankton organisms with key roles in marine trophic webs and global carbon flux. Like most appendicularians with cosmopolitan distributions, Oikopleura dioica Fol, 1872 is considered a single species worldwide based on morphological features that distinguish them from other appendicularians. Despite their abundance, however, there are still only ~ 70 described appendicularian species, compared to over 2800 ascidian tunicates. Here we perform a molecular phylogenetic, morphological, and reproductive assessment of O. dioica specimens collected from the Ryukyu Archipelago, mainland Japan, and Europe. The specimens are morphologically very similar, with only detailed examination of the oikoplastic epithelium and quantitative measurements revealing minor distinguishing characteristics. Phylogenetic analyses of the ribosomal gene loci and mitochondrial cytochrome oxidase I (COI) gene strongly indicate that they form three separate genetic clades despite their morphological similarities. Finally, in vitro crosses between the Ryukyu and mainland Japanese specimens show total prezygotic reproductive isolation. Our results reveal that the current taxonomic O. dioica classification likely hides multiple cryptic species, highlighting the genetic diversity and complexity of their population structures. Cryptic organisms are often hidden under a single species name because their morphological similarities make them difficult to distinguish and their correct identification is fundamental to understanding Earth's biodiversity. O. dioica is an attractive model to understand how morphological conservation can be maintained despite pronounced genetic divergence. [ABSTRACT FROM AUTHOR]

The blackfin tuna, Thunnus atlanticus, is a small tropical tuna exploited by recreational and commercial fisheries in various parts of its range. Information on stock structure is needed to develop management plans for this species but is currently lacking. In this work, 470 blackfin tuna from nine geographic populations were assayed at 13 homologous microsatellite markers to provide a first assessment of stock structure across the species range. The overall divergence among locality samples was very low (overall FST = 0.0004) indicating high connectivity of blackfin tuna across their range. No clear grouping of localities in differentiated units was inferred but structuring followed a weak isolation by distance pattern (r = 0.16, P = 0.032). Pairwise exact tests and spatial analysis of molecular variance suggested divergence of the sample collected offshore Baía Formosa (Brazil) possibly reflecting reproductive isolation of Brazilian populations from those in the Caribbean region and further north. Further study of the status of Brazilian populations and the transition between this region and the Caribbean is warranted. Cryptic subdivision within the Northern Hemisphere part of the range is possible and should be evaluated using increased marker density and a more comprehensive geographic coverage. [ABSTRACT FROM AUTHOR]

Omobranchus punctatus is native to the Indo-Pacific region and invasive in the Atlantic region, currently being considered one of the most widely distributed blenny species. However, recent molecular studies indicated that O. punctatus is a complex of species, with three divergent mtDNA lineages identified to date, stressing the need for a taxonomic revision. In this study, we used an integrative approach, combining morphological and genetic data, to shed light on the taxonomy and distribution of O. punctatus. Moreover, we provide the first genetic records of introduced populations in Brazil and discuss the introduction pattern of this species in this region. Morphological data shows that O. punctatus consists of at least five distinct and geographically restricted species: O. punctatus sensu stricto, O. dispar, O. sewalli, O. cf. kochi, and O. cf. japonicus. Species delimitation analyses performed using the mtDNA data available confirmed that O. punctatus sensu stricto, O. dispar and O. sewalli correspond to different species that started to diverge about 2.6 Mya. Furthermore, O. sewalli was identified as the invasive species colonizing Atlantic shores. The existence of historical oceanographic barriers, such as the emergence of the Sunda Shelf in the Eastern Indian Ocean during the Pleistocene, and the biological traits of these blennies are the most likely factors responsible for their genetic differentiation and subsequent speciation. [ABSTRACT FROM AUTHOR]

The Australian dingo is a recent anthropogenic addition to the Australian fauna, which spread rapidly across the continent and has since widely interbred with modern dogs. Genetic studies of dingoes have given rise to speculation about their entry to the continent and subsequent biogeographic effects, but few studies of their contemporary population structure have been conducted. Here we investigated the dingo ancestry and population structure of free-living dogs in western Victoria and contrasted it with a wider southern Australian sample. We wished to determine whether their geographic isolation was mirrored in genetic isolation. To address this question, we analysed 34 microsatellite markers using Bayesian clustering and discriminant analysis of principal components, and summarised genetic diversity at the population and individual level. The broader southern Australia sample (n = 1138) comprised mostly hybrid animals, with 30% considered pure dingoes. All western Victorian individuals (n = 59) appeared to be hybrids with high dingo ancestry. The population showed no evidence of admixture with other populations and low genetic diversity on all measures tested. Based upon our characterisation of this unusual mainland population, we advise against assuming homogeneity of dingoes across the continent. [ABSTRACT FROM AUTHOR]

The syconium is the urn-shaped inflorescence shared by all species of the genus Ficus. The orifice at the apex of the syconium is called the ostiole, and it is covered by interlocking bracts. The ostiolar bracts can have different arrangements, which only allow the entry of mutualist wasps and promote reproductive isolation among Ficus species. Here, we analyze the ostiolar structures that could play a role as selective filter and therefore impact the fig-fig wasp mutualism in the neotropical Ficus sections Americanae and Pharmacosycea. Samples of syconia with pistillate flowers during the receptive phase of seven species of Ficus were examined using light and scanning electron microscopy. Tests for histolocalization of substances were employed to detect secretory activity throughout the ostiolar tissues. Our results indicated that the ostiole has two components: ostiolar bracts and the periostiolar zone. Interspecies variation in ostiolar bract arrangement in both sections studied was broader than previously reported. We report for the first time for Ficus: (i) two types of ostiolar osmophores (mesophyll and diffuse), that could be a source of volatile compounds for attracting fig wasps; (ii) colleters in the axil of ostiolar bracts, which probably lubricate and facilitate the entry of pollinating wasps into the syconial cavity; (iii) secretory trichomes around the ostiolar bracts, and (iv) syconium basal bracts (F. isophlebia) covering the ostiole, which are the first physical barrier that the fig wasps must overcome to access receptive pistillate flowers. We describe the zones that compose the ostiole, which support the hypothesis that the ostiole is a selective filter in the interactions of fig trees with Agaonidae fig wasps. We also suggest that ostiolar osmophores, colleters, the periostiolar zone, and the arrangements of the ostiolar bracts may be informative with respect to Ficus systematics. [ABSTRACT FROM AUTHOR]

Triatoma mexicana is an important vector of Trypanosoma cruzi—the etiological agent of Chagas disease. This triatomine species occurs in central Mexico, but little is known about its genetic variability. Using Cyt-b gene as a genetic marker, in this study, we determined the population genetic structure of T. mexicana collected from the States of Hidalgo, Guanajuato, and Queretaro where populations are largely peridomiciliary. A Bayesian approach was performed for the design of phylogenies, median-joining networks, and clustering among populations of T. mexicana. Our results show that the Hidalgo population was the most distinct, with the highest genetic and haplotypic variation (Hd = 0.963, π = 0.06129, and ɵ = 0.05469). Moderate gene flow (Nm) was determined among populations of Hidalgo and Queretaro. Populations from the three states showed differentiation (FST) values ranging from 0.22 to 0.3, suggesting an important genetic differentiation. The phylogenetic analysis showed the presence of five well-defined groups, as well as the haplotype network, where 24 haplotypes were observed forming five haplogroups with high mutational steps among them: 68 (Hgo-W2), 26 (Qto), 59 (Hgo-M), 44 (Hgo-W1), and 46 (Gto). Genetic isolation was apparently inferred in the Guanajuato population; however, the Mantel test did not show correlation between genetic (FST) and geographic (km) distances (p = 0.05). The STRUCTURE analyses showed seven genetic clusters and it was observed that a single cluster predominates in each sampled location. However, genetic admixture was detected in four localities. Our results show evidence that there are multiple species within the collected sampling area. [ABSTRACT FROM AUTHOR]

The genetic diversity and differentiation of four geographic populations of Neoschongastia gallinarum were evaluated using concatenated mitochondrial gene sequences (pCOI, pCOII, and pND5). Based on the results, the N. gallinarum populations had high genetic diversity and strong ecological adaptability. Genetic differentiation among paired populations calculated using concatenated mitochondrial gene sequences revealed that geographic isolation resulted in genetic differentiation among the populations of N. gallinarum, and gene flow between populations associated with human trade activities. Systematic development and molecular variance based on haplotypes revealed that genetic variation existed in different haplotypes; however, no clear rule related to geographic region was found. Further, genetic variation was mainly derived from individuals within the population. A neutral test based on concatenated mitochondrial gene sequences and nucleotide pair differences revealed that N. gallinarum did not experience an obvious population expansion in recent historical periods. Accordingly, the population size was relatively stable. [ABSTRACT FROM AUTHOR]

The emergence of reproductive isolation is key in maintaining within- and between-species diversity and one of the initial steps of speciation. In the Iberian Peninsula, the diverging populations of the Brachionus plicatilis rotifer create an ideal system to shed light on the mechanisms that give rise to the emergence of reproductive isolation. Herein, we quantify the degree of behavioural reproductive isolation in two groups of B. plicatilis populations, namely, neighbouring populations diverging by adaptation to the local environment and populations diverging in the absence of gene flow due to geographic distance. We conduct behavioural no-choice assays to test mating reproductive isolation between these populations. The analysis shows signatures of ongoing behavioural reproductive isolation in most of the population crosses, which is more pronounced in populations with a higher level of adaptive divergence, presumably under high migration rates. Overall, this study suggests that local adaptation is associated with mating behaviour resulting in reproductive isolation. [ABSTRACT FROM AUTHOR]

Postmating-prezygotic (PMPZ) reproductive isolation is hypothesized to result from divergent coevolutionary trajectories of sexual selection and/or sexual conflict in isolated populations. However, the genetic basis of PMPZ incompatibilities between species is poorly understood. Here, we use a comparative framework to compare global gene expression in con- and heterospecifically mated Drosophila mojavensis and D. arizonae female reproductive tracts. We find striking divergence between the species in the female postmating transcriptional response to conspecific mating, including differences in differential expression (DE), alternative splicing (AS), and intron retention (IR). As predicted, heterospecific matings produce disrupted transcriptional profiles, but the overall patterns of misregulation are different between the reciprocal crosses. Moreover, we find a positive correlation between postmating transcriptional divergence between species and levels of transcriptional disruption in heterospecific crosses. This result indicates that mating responsive genes that have diverged more in expression also have more disrupted transcriptional profiles in heterospecifically mated females. Overall, our results provide insights into the evolution of PMPZ isolation and lay the foundation for future studies aimed at identifying specific genes involved in PMPZ incompatibilities and the evolutionary forces that have contributed to their divergence in closely related species. Comparison of global gene expression patterns in con- and heterospecifically mated Drosophila mojavensis and Drosophila arizonae suggest that mating-responsive genes with divergent expression also exhibit more disrupted transcriptional profiles in heterospecifically mated females, providing further insight into the evolution of postmating-prezygotic reproductive isolation. [ABSTRACT FROM AUTHOR]