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Nonbiting midges (family Chironomidae) are found throughout the world in a diverse array of aquatic and terrestrial habitats, can often tolerate harsh conditions such as hypoxia or desiccation, and have consistently compact genomes. Yet we know little about the shared molecular basis for these attributes and how they have evolved across the family. Here, we address these questions by first creating high-quality, annotated reference assemblies for Tanytarsus gracilentus (subfamily Chironominae, tribe Tanytarsini) and Parochlus steinenii (subfamily Podonominae). Using these and other publicly available assemblies, we created a time-calibrated phylogenomic tree for family Chironomidae with outgroups from order Diptera. We used this phylogeny to test for features associated with compact genomes, as well as examining patterns of gene family evolution and positive selection that may underlie chironomid habitat tolerances. Our results suggest that compact genomes evolved in the common ancestor of Chironomidae and Ceratopogonidae and that this occurred mainly through reductions in noncoding regions (introns, intergenic sequences, and repeat elements). Significantly expanded gene families in Chironomidae included biological processes that may relate to tolerance of stressful environments, such as temperature homeostasis, carbohydrate transport, melanization defense response, and trehalose transport. We identified several positively selected genes in Chironomidae, notably sulfonylurea receptor, CREB-binding protein, and protein kinase D. Our results improve our understanding of the evolution of small genomes and extreme habitat use in this widely distributed group. [ABSTRACT FROM AUTHOR]

The wolverine (Gulo gulo) is a Holarctic species found in North America primarily across the boreal forest, the subarctic, and along the Pacific coast, including Vancouver Island (VI), British Columbia. While wolverines on VI are rare and possibly extirpated, they have been previously described as a unique subspecies, G. g. vancouverensis , distinct from G. g. luscus from the mainland of North America. However, the validity of the VI subspecies is contentious, with conflicting results from studies of skull morphology. Here, we used molecular analyses to characterize the genetic diversity of the VI population and resolve this taxonomic debate to assist with conservation priorities. Historical DNA of VI wolverines was obtained from museum specimens, amplified at 16 nuclear microsatellite loci, and sequenced at the mitochondrial D-loop control region to compare with wolverines from mainland British Columbia. The VI population had lower allelic richness and was fixed for a single common mtDNA haplotype. Bayesian and non-Bayesian assignments using microsatellites generally revealed admixture across populations, implying allele frequencies between the VI and mainland populations were not significantly different. Hence, both types of genetic markers showed little evolutionary divergence between VI and the mainland population. Combined, these results do not provide evidence of significant genetic distinction for VI wolverines, nor support the subspecific classification. Immediate conservation efforts should focus on estimating population size, while future conservation planning can assume VI wolverines likely are not a unique genetic population and there remains the potential for natural recolonization of wolverines to VI. [ABSTRACT FROM AUTHOR]

The widespread occurrence of alternative reproductive tactics (ARTs) highlights the diverse ways in which sexual selection can operate within a population. We studied ARTs in Columbian ground squirrels (Urocitellus columbianus), evaluating paternity, lifetime reproductive success, and life histories. Reproductively mature male Columbian ground squirrels displayed either a territorial or satellite (nonterritorial) tactic. Territorial males secured a higher proportion of copulations, were more likely to mate at earlier positions in females' mating sequences, and sired more offspring than satellite males. The tactic males adopted were largely a function of weight, age, and experience, with larger, older, and more experienced males displaying the territorial tactic. At 2 years of age, males adopted the satellite tactic or deferred breeding for the season. Two-year-old satellite males were heavier than males that deferred breeding, but by age 3, there was no difference between their weights. Males that deferred breeding either adopted the satellite or territorial tactic in the following year, with the lighter males displaying the satellite tactic. The ARTs that males adopted at 2 and 3 years of age led to alternative life history pathways. Males that deferred breeding and only adopted the territorial tactic during their lifetime had twice the number of lifetime offspring compared with males that adopted the satellite tactic and then switched to territorial behavior in following years, although this difference was not statistically significant. Our findings show that the satellite tactic results in lower reproductive output both within a single year, except at age 2, and over their lifetime. [ABSTRACT FROM AUTHOR]

Cooperative breeding is a breeding system in which offspring receive care not only from their parents but also from other conspecific helpers. This helping behavior could potentially be costly to attendants; however, one of the means by which helpers can override these costs is through preferentially directing aid towards kin. Helping patterns might vary according to helper sex if sex-biased dispersal is present. Here, we examined how genetic relatedness and sex of helpers shaped their provisioning behavior in the noisy miner (Manorina melanocephala). This common Australian passerine lives year-round in large colonies that contain both related and unrelated individuals. There was a strong sex-bias in helper effort, with 93% of helpers being philopatric males that remain in natal colonies for life, even though males make up only 69% of the population. Females dispersed prior to breeding and rarely helped at the nest. Helpers varied in their level of relatedness to the breeders which positively predicted their provisioning rate and biomass delivered to the broods, with the majority of help provided by related helpers. These results show that there was a clear sex difference in helping behavior in this species; with related males, most likely retained offspring from previous years, being the main providers of aid among all helpers. Kinship and patterns of philopatry, therefore, appear to be important drivers of helping behavior in noisy miners, although given that unrelated helpers also provisioned young at substantial levels, other types of direct benefits may further play a role in maintaining cooperatively breeding in this species. [ABSTRACT FROM AUTHOR]

Abstract: Phenological shifts are the most widely reported ecological responses to climate change, but the requirements to distinguish their causes (i.e. phenotypic plasticity vs. microevolution) are rarely met. To do so, we analysed almost two decades of parturition data from a wild population of North American red squirrels (Tamiasciurus hudsonicus). Although an observed advance in parturition date during the first decade provided putative support for climate change‐driven microevolution, a closer look revealed a more complex pattern. Parturition date was heritable [h2 = 0.14 (0.07–0.21 (HPD interval)] and under phenotypic selection [β = −0.14 ± 0.06 (SE)] across the full study duration. However, the early advance reversed in the second decade. Further, selection did not act on the genetic contribution to variation in parturition date, and observed changes in predicted breeding values did not exceed those expected due to genetic drift. Instead, individuals responded plastically to environmental variation, and high food [white spruce (Picea glauca) seed] production in the first decade appears to have produced a plastic advance. In addition, there was little evidence of climate change affecting the advance, as there was neither a significant influence of spring temperature on parturition date or evidence of a change in spring temperatures across the study duration. Heritable traits not responding to selection in accordance with quantitative genetic predictions have long presented a puzzle to evolutionary ecologists. Our results on red squirrels provide empirical support for one potential solution: phenotypic selection arising from an environmental, as opposed to genetic, covariance between the phenotypic trait and annual fitness. [ABSTRACT FROM AUTHOR]

In many socially monogamous bird species, both sexes regularly engage in mating outside their pair bond. Although the benefits of extra-pair (EP) mating behavior are clear and well established for males, such as an increase in the number of sired offspring, the benefits of EP mating behavior to females are less clear. A dominant theory for the incidence of EP mating is that socially monogamous females can improve the genetic quality of their offspring and avoid the costs of inbreeding through EP mating. In addition, in cooperatively breeding species, the theory of "parental care" predicts that females obtain additional help for their offspring through EP matings. Here, we examined evidence for both the inbreeding avoidance and parental care hypotheses in the cooperatively breeding noisy miner (Manorina melanocephala). Overall, EP mating occurred in 27% of broods, with 14% of offspring sired by males other than the identified pair-bonded male. There was a strong tendency to avoid pairing with genetically related individuals, with 86% of breeding pairs being significantly less related to each other than the general population. The occurrence of EP paternity was independent of the degree of relatedness between the pair. Provisioning patterns in relation to EP mating was not consistent with the "parental care" hypothesis and EP males did not contribute to the care of broods. These results demonstrate that in this system, there is no evidence that EP mating might function as a mechanism to reduce the costs of inbreeding depression or to gain benefits of extra helpers. [ABSTRACT FROM AUTHOR]

Kin recognition can facilitate kin selection and may have played a role in the evolution of sociality. Red squirrels (Tamiasciurus hudsonicus) defend territories using vocalizations known as rattles. They use rattles to discriminate kin, though the mechanism underlying this ability is unknown. Our objective was to distinguish between the mechanisms of prior association, where animals learn the phenotypes of kin they associate with early in life, and phenotype matching/recognition alleles, where animals use a template to match phenotypes, thereby allowing them to recognize kin without an association early in life. We used audio playbacks to measure the responses of squirrels to rattles from familiar kin, unfamiliar kin, and non-kin. Initial analyses revealed that red squirrels did not discriminate between familiar and unfamiliar kin, but also did not discriminate between kin and non-kin, despite previous evidence indicating this capability. Post hoc analyses showed that a squirrel's propensity to rattle in response to playback depended on an interaction between relatedness and how the playback stimuli had been recorded. Red squirrels discriminated between rattles from close kin (r = 0.5) and rattles from non-kin (r < 0.125) when the rattles were recorded from provoked squirrels. Squirrels did not exhibit kin discrimination in response to unsolicited rattles. Once we accounted for how the stimuli had been recorded, we found no difference in the responses to familiar and unfamiliar kin. Our study suggests that kin discrimination by red squirrels may be context dependent. [ABSTRACT FROM AUTHOR]

Extrinsic factors such as physical barriers play an important role in shaping population genetic structure. A reduction in gene flow leading to population structuring may ultimately lead to population divergence. These divergent populations are often considered subspecies. Because genetic differentiation may represent differences between subspecies, patterns of genetic structure should reflect subspecies groupings. In this study, we examine the contemporary population genetic structure of muskrat (n = 331) and assess the relevance of 4 geographically distinct subspecies designations across northern North America using 9 microsatellite loci. We predicted that patterns of gene flow and genetic structure would reflect the described subspecies. We found evidence of genetic differentiation between western and eastern regions, and muskrats from Newfoundland (NF) showed significantly lower genetic diversity than central regions. A strong isolation by distance pattern was also detected within the eastern cluster. Our results did not differentiate Ondatra zibethicus spatulus (northwest) from O. z. albus (central), but they suggest a distinction between O. z. obscurus (NF) and O. z. zibethicus (east). This study highlights the need for more phylogenetic studies in order to better understand intraspecific divergence and the genetic characterization of subspecies. [ABSTRACT FROM PUBLISHER]

Multiple mating by females is common in many mammalian species, often resulting in mixed paternity litters. In such mating systems, mating order, male age, and male body mass frequently play an important role in determining male reproductive success. We tested for these effects on male reproductive success in Columbian ground squirrels (Urocitellus columbianus). The mating activity of estrous females was observed, and the occurrence of sperm precedence was tested using microsatellites to determine paternity in a total of 147 litters (434 offspring), including 110 litters (334 offspring) where the mating position of individual males was determined. Females mated with up to 8 males per litter, whereas paternity analyses revealed that only the first 5 males to mate actually sired offspring. The number of offspring sired significantly decreased with position in the mating sequence, showing a strong first male advantage. The extent of this advantage diminished with an increasing number of male mating partners, indicating that sperm competition plays an important role. A male's position in the females' mating sequences was not consistent within and across seasons, suggesting that individual males did not follow distinct reproductive strategies. Rather, males of intermediate age were more successful than young and old males, when corrected for age effects; heavier males were more likely to mate first. We conclude that males gain the largest part of their seasonal reproductive output from mating first with a female due to a pronounced first male advantage but gain considerable additional fitness from mating with additional, already mated females. [ABSTRACT FROM PUBLISHER]

Background Despite the theoretical advantages of coating knitted grafts with a material designed to reduce blood loss, their performance has not been directly compared with woven grafts in a prospective randomized trial. The aim of this study was to compare the graft handling qualities and operative blood loss of the two types of arterial prosthesis, as well as complication rate and patient survival at 1 year. Methods A total of 267 consecutive patients having surgery for occlusive or aneurysmal disease of the aortoiliac arteries were randomized to receive woven (141 patients) or knitted collagen-impregnated Dacron (126 patients) grafts. Graft patency was assessed on discharge and at 1 year by duplex imaging. Results Mean(s.d.) intraoperative blood loss was statistically greater with woven grafts (1690(1424) ml) compared with knitted (1363(1172) ml) (P=0·049). An insignificant 1-year increase in mean(s.d.) graft diameter of 1·2(0·2) mm was found at the distal anastomosis in the knitted group. There was no difference in graft patency between the groups and only one graft became infected. Conclusion This study suggests that knitted and woven grafts have similar clinical performance and therefore the less expensive material (woven) should usually be selected unless haemorrhagic complications are anticipated. [ABSTRACT FROM AUTHOR]