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We synthesize observations from 1979 to 2016 of a contact zone involving two subspecies of pocket gophers (Thomomys bottae connectens and T. b. opulentus) and their respective chewing lice (Geomydoecus aurei and G. centralis) along the Río Grande Valley in New Mexico, U.S.A., to test predictions about the dynamics of the zone. Historically, the natural flood cycle of the Rio Grande prevented contact between the two subspecies of pocket gophers. Flood control measures completed in the 1930s permitted contact, thus establishing the hybrid zone between the pocket gophers and the contact zone between their lice (without hybridization). Since that time, the pocket gopher hybrid zone has stabilized, whereas the northern chewing louse species has replaced the southern louse species at a consistent rate of ~150 m/year. The 0.2–0.8 width of the replacement zone has remained constant, reflecting the constant rate of chewing louse species turnover on a single gopher and within a local pocket gopher population. In contrast, the full width of the replacement zone (northernmost G. centralis to southernmost G. aurei) has increased annually. By employing a variety of metrics of the species replacement zone, we are better able to understand the dynamics of interactions between and among the chewing lice and their pocket gopher hosts. This research provides an opportunity to observe active species replacement and resulting distributional shifts in a parasitic organism in its natural setting. [ABSTRACT FROM AUTHOR]

The author reflects on biologist Alfred Russel Wallace and his work related to biogeography. He states that his discoveries at Malay Archipelago was remarkable, where he apart from providing description of biotic transition, speculated geological history. He mentions that Wallace studied biological diversity here which helped to give insight to the process of evolutionary diversification. He highlights that he used to rely on mammalian fossil to interpret ecological impact of mammalian biota.

Historically, a large number of taxonomic forms has been recognized within Nearctic pikas (Lagomorpha: Ochotonidae; Ochotona), including up to 13 species and 37 subspecies. After 1965, 2 species and 37 forms have been recognized: the monotypic O. collaris of Alaska, British Columbia, Yukon, and Northwest Territories, and O. princeps, with 36 subspecies spread throughout western Canada and the western United States. The 36 subspecies of O. princeps have been distinguished by subtle differences, particularly in pelage coloration and body size, within the highly fragmented distribution of the species on isolated "islands" of cool, rocky habitat. However, molecular phylogenetic studies (allozyme electrophoresis and sequencing of both mitochondrial and nuclear genomes) indicate the existence of 5 phylogenetic lineages within O. princeps. The cohesiveness of each lineage has been reinforced during glacial stages by introgressive hybridization among currently isolated populations within each lineage. In contrast, the low level of cranial variation and lack of consistent differentiation in cranial characters, pelage coloration, or body size among the 5 lineages indicates idiosyncratic interlocality variation due to high inbreeding within highly isolated populations, genetic drift, and possibly selection for common traits. Examination of allozymic, morphological, and nuclear DNA data indicates previous introgressive hybridization among several of the lineages, probably associated with contact during the Last Glacial Maximum. Herein we characterize morphometric variation between and among O. collaris (n = 164) and O. princeps (n = 1,999) and revise the subspecific taxonomy of O. princeps to 5 subspecies based on molecular phylogenetic lineages, at least 3 of which are known to possess a unique dialect in the short call: O. p. princeps (Northern Rocky Mountains), O. p. fenisex (Coast Mountains and Cascade Range), O. p. saxatilis (Southern Rocky Mountains), O. p. schisticeps (Sierra Nevada and Great Basin), and O. p. uinta (Uinta Mountains and Wasatch Range of central Utah). These 5 subspecies represent evolutionarily meaningful units for consideration of possible management applications if populations of O. princeps are imperiled by human activities. [ABSTRACT FROM AUTHOR]

Aim We studied the history of colonization, diversification and introgression among major phylogroups in the American pika, Ochotona princeps (Lagomorpha), using comparative and statistical phylogeographic methods. Our goal was to understand how Pleistocene climatic fluctuations have shaped the distribution of diversity at mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) loci in this alpine specialist. Location North America’s Intermountain West. Methods We accumulated mtDNA sequence data ( c. 560–1700 bp) from 232 pikas representing 64 localities, and sequenced two nuclear introns (mast cell growth factor, c. 550 bp, n = 148; protein kinase C iota, c. 660 bp, n = 139) from a subset of individuals. To determine the distribution of major mtDNA lineages, we conducted a phylogenetic analysis on the mtDNA sequence data, and we calculated divergence times among the lineages using a Bayesian Markov chain Monte Carlo approach. Relationships among nuclear alleles were explored with minimum spanning networks. Finally, we conducted coalescent simulations of alternative models of population history to test for congruence between nDNA and mtDNA responses to Pleistocene glacial cycles. Results We found that: (1) all individuals could be assigned to one of five allopatric mtDNA lineages; (2) lineages are associated with separate mountain provinces; (3) lineages originated from at least two rounds of differentiation; (4) nDNA and mtDNA markers exhibited overall phylogeographic congruence; and (5) introgression among phylogroups has occurred at nuclear loci since their initial isolation. Main conclusions Pika populations associated with different mountain systems have followed separate but not completely independent evolutionary trajectories through multiple glacial cycles. Range expansion associated with climate cooling (i.e. glaciations) promoted genetic admixture among populations within mountain ranges. It also permitted periodic contact and introgression between phylogroups associated with different mountain systems, the record of which is retained at nDNA but not mtDNA loci. Evidence for different histories at nuclear and mtDNA loci (i.e. periodic introgression versus deep isolation, respectively) emphasizes the importance of multilocus perspectives for reconstructing complete population histories. [ABSTRACT FROM AUTHOR]

Aim The Mohave ground squirrel ( Xerospermophilus mohavensis) is one of a few endemic species of the Mojave Desert of south-western North America. We describe phylogeographic patterns within this species and its sister taxon ( Xerospermophilus tereticaudus) and test hypotheses concerning their biogeographical history using genetic signatures of stable versus expanding populations. We compare these patterns with those of other Mojave species to evaluate the role of vicariance in producing phylogeographic structure during the assembly of the Mojave Desert biota. Location The Mojave Desert and adjacent desert regions of south-western North America. Methods Complete cytochrome b gene sequences of X. mohavensis (46 individuals representing 11 localities) and X. tereticaudus (38 individuals representing 14 localities) were analysed using Bayesian methods to infer phylogenetic relationships. Genetic signals of stable or expanding populations were examined based on the distribution of recent mutations and pairwise differences, as well as with a coalescent-based approach. Results The two species are reciprocally monophyletic and may have diverged in response to the late Pliocene–early Pleistocene uplift of the Transverse Ranges and Mojave block. Little phylogeographic structure is evident within X. mohavensis, but there is a signature of northern expansion from a presumably full-pluvial refugium in the Mojave River basin. Four geographic subgroups are evident within X. tereticaudus, and there is a signature of northern expansion from a presumably full-pluvial refugium in the Sonoran coastal plains. Roughly congruent phylogeographic patterns are found within five arid-adapted taxa, indicating a strong element of vicariance during the assembly of the generally transitional Mojave Desert biota. Main conclusions We present a preliminary model for the historical assembly of the Mojave Desert biota that indicates a strong vicariant element producing autochthonous lineages (including X. mohavensis) that diverged during the major geological and climatic events of the last 5 Myr. Phylogeographic partitioning within the Mojave Desert underscores the necessity of immediate conservation measures for this unique and fragile arid ecosystem that is locked between two large metropolitan population centres and is the target of continued adverse environmental impact. [ABSTRACT FROM AUTHOR]

The genetic consequences of climate-driven range fluctuation during the Pleistocene have been well studied for temperate species, but cold-adapted (e.g., alpine, arctic) species that may have responded uniquely to past climatic events have received less attention. In particular, we have no a priori expectation for long-term evolutionary consequences of elevation shifts into and out of sky islands by species adapted to alpine habitats. Here, we examined the influence of elevation shifts on genetic differentiation and historical demography in an alpine specialist, the American pika ( Ochotona princeps). Pika populations are divided into five genetic lineages that evolved in association with separate mountain systems, rather than lineages that reflect individual sky islands. This suggests a role for glacial-period elevation shifts in promoting gene flow among high-elevation populations and maintaining regional cohesion of genetic lineages. We detected a signature of recent demographic decline in all lineages, consistent with the expectation that Holocene climate warming has driven range retraction in southern lineages, but unexpected for northern populations that presumably represent postglacial expansion. An ecological niche model of past and future pika distributions highlights the influence of climate on species range and indicates that the distribution of genetic diversity may change dramatically with continued climate warming. [ABSTRACT FROM AUTHOR]

Once encompassing as many as 9 species of pocket gophers spread across most of the Mexican Altiplano, the genus Pappogeomys is now restricted to a single species, P. bulleri, occupying the mountains, tablelands, and coastal plains near the western end of the Trans-Mexican Volcanic Belt in west-central Mexico. Herein, we review the taxonomic history of Pappogeomys and examine relationships among populations of P. bulleri from throughout the geographic range of the species based on analyses of nonpreferentially stained karyotypes and mitochondrial and nuclear sequence data. Results of these analyses are concordant and reveal 3 major clades of P. bulleri that are separated by major physiographic features of the region, including the Sierra Madre del Sur and drainages of the Río Grande de Santiago, Río Ameca, Río Ayuquila, and Río Armería. We reduce the number of subspecies of P. bulleri from 9 to 5 valid forms and provide a revised synonymy of the species. [ABSTRACT FROM AUTHOR]

The Southern Coahuila Filter-Barrier (SCFB) effectively subdivides the mammalian fauna of the Mesa del Norte, the northern and most extensive section of the Mexican Altiplano. Pocket gophers of the genus Cratogeomys north and south of this filter-barrier have been informally recognized as 2 distinct species, C. castanops and C. goldmani, respectively. Support for species recognition derives from early morphological comparisons and recent chromosomal and ectoparasite studies. Contradictory conclusions based on the only comprehensive morphometric study have prevented formal recognition of C. goldmani. A morphometric reevaluation based on ratiotransformed data reveals that the previous analysis was unduly biased by size, an ecophenotypically plastic character. When this factor is removed, morphometric variation is fully concordant with chromosomal diploid number and sequence data of mitochondrial and nuclear DNA. We provide synonymies and descriptions for C. goldmani apart from C. castanops, and revise the number of subspecies from a total of 26 to 2 subspecies in each species. The SCFB is most effective in its central portion (Desierto Mayán), and least effective in its western portion (Río Nazas), which should be geographically broadened to include the neighboring Río Aguanaval. [ABSTRACT FROM AUTHOR]

Presents a study which examined evolutionary affinities of populations of Peromyscus mice from islands in the Sea of Cortez. Review of related literature; Information on the mammals; Materials and methods used; Findings and conclusions.

Evaluates the role of Late Miocene to Pleistocene geological history in the evolution of a distinct Baja California Peninsular Desert biota. Analyses of phylogeographic population structure across a suite of animal species; Comparative examination of phylogroup distributions; Evidence for the occurrence of vicariance events.

Species and their geographical distributions, tabulated either from regional faunal and floral monographs or directly from natural history collections, often are used as the basic units of analysis by ecologists and biogeographers. It has been argued that in order for species to be operationally useful units for evolutionary and ecological studies, they need to be recognizable and identifiable as distinct entities. A growing body of molecular phylogeographic studies demonstrates that currently recognized species often are unreliable in their approximation of fundamental evolutionary and geographical units, leading, for example, to proposed usage of molecular-based evolutionarily significant units in lieu of species in conservation biology. We argue that ecologists and biogeographers should likewise employ evolutionarily significant units as basic units of analysis when evidence clearly indicates that a formally recognized species either fails to convey important evolutionary and geographical information (i.e. includes multiple geographically distinct evolutionary lineages) or fails to delineate a natural entity (i.e. does not represent a monophyletic set of populations). We demonstrate the limitations of current species as evolutionary, geographical, and conservation units within the ecologically wellstudied North American desert rodent assemblage. We suggest that biotic surveys should be designed to allow the efficient assembly and dissemination of molecular phylogeographic data from ecologically and biogeographically representative systems. [ABSTRACT FROM AUTHOR]

Studies the historical biogeography of the least shrew or Cryptotis parva in the West. Dispersals in the east; Allozymic complement of populations at Bitter Lake along the Pecos River Valley; Cranial morphology.

Explores the major genetic units of the neararctic pika Ochotona princeps. Fragmentation into isolated montane refuge during subsequent interglacial; Contributing factors of low genetic variation.

The southern pocket gopher, Thomomys umbrinus, traditionally has been divided into as many as 5 genetically defined subclades based on chromosomal and allozymic data. Recent molecular analyses have resurrected 2 species from within these clades: 1 from the Pacific coastal lowlands (T. atrovarius), and another from the highlands of the Sierra Madre Occidental (T. sheldoni). In this study, multilocus genetic analyses of 3 mitochondrial and 5 nuclear genes reveal a previously unrecognized 3rd species apparently restricted to the Sierra del Nayar of northeastern Nayarit, Mexico. In addition to molecular and chromosomal studies of this new species, cranial morphology is analyzed to help distinguish it from its congeners. This taxon, T. nayarensis,i s described herein, and a key to distinguishing the 3 species of Thomomys in northeastern Nayarit is provided. [ABSTRACT FROM AUTHOR]

Thomomys sheldoni Bailey, 1915 is resurrected to recognize a genetically divergent clade of smooth-toothed pocket gophers that inhabits the high-elevation pine-oak forests of the Sierra Madre Occidental in Mexico from northwestern Chihuahua through Durango to western Zacatecas and northeastern Nayarit. Analyses of DNA sequences from 8 genes and genotype assignment tests for 21 allozyme loci establish this clade as a genetically isolated taxon within the T. umbrinus (sensu lato) complex. in addition to the T. sheldoni clade (diploid number of 2n = 76), 3 genetic clades within T. umbrinus (2n = 78) and 1 newly discovered clade (2n = 76) also were recovered in the phylogenetic analyses. individuals of T. sheldoni and T. umbrinus occur in close proximity with no evidence of gene flow and an average cytochrome-b genetic divergence of 15.6%. Analyses of cranial morphology reveal that skulls of T. sheldoni are, on average, broader and longer than skulls of T. umbrinus and T. atrovarius. We recognize and provide synonymies for 2 subspecies within T. sheldoni based on a weak genetic and morphological break that is coincident with a large, north-south gap in its distribution: T. s. sheldoni in the southern Sierra Madre Occidental, which includes specimens from the type locality and populations in Durango, Zacatecas, and Nayarit; and T. s. chihuahuae in the northern Sierra Madre Occidental, which is known only from Chihuahua. [ABSTRACT FROM AUTHOR]

The New World rodent family Heteromyidae shows a marvelous array of ecomorphological types, from bipedal, arid-adapted forms to scansorial, tropical-adapted forms. Although recent studies have resolved most of the phylogenetic relationships among heteromyids at the shallower taxonomic levels, fundamental questions at the deeper taxonomic levels remain unresolved. This study relies on DNA sequence information from 3 relatively slowly evolving mitochondrial genes, cytochrome c oxidase subunit I, 12S, and 16S, to examine basal patterns of phylogenesis in the Heteromyidae. Because slowly evolving mitochondrial genes evolve and coalesce more rapidly than most nuclear genes, they may be superior to nuclear genes for resolving short, basal branches. Our molecular data (2,381 base pairs for the 3-gene data set) affirm the monophyly of the family and resolve the major basal clades in the family. Alternative phylogenetic hypotheses of subfamilial relationships are examined statistically and the Perognathinae and Heteromyinae are found to represent sister clades relative to the Dipodomyinae. The 3 traditional subfamilial groupings are supported; the controversial placement of Microdipodops as a sister clade to Dipodomys in the Dipodomyinae is affirmed, Perognathus and Chaetodipus are distinct sister clades within the Perognathinae, and species of Liomys and Heteromys form the resolved clade Heteromyinae. However, Liomys is found to be paraphyletic relative to Heteromys and, given that this finding corroborates earlier studies, we present a formal taxonomy of Heteromys wherein we place Liomys in synonymy. Semiparametric and parametric methods are used to estimate divergence times from our molecular data and a chronogram of the Heteromyidae, calibrated by the oldest known fossils of Dipodomys and Perognathus, is presented. Our time estimates reveal subfamilial differentiation in the early Miocene (22.3-21.8 million years ago) and pose testable times of divergence for the basal heteromyid nodes. With the basal heteromyid clades resolved and cladogenic events positioned in a time framework, we review the major geological and paleoecological events of the Oligocene and Miocene associated with the early historical biogeography of the family. [ABSTRACT FROM AUTHOR]

A study of chromosomal variation in the Mexican pocket gopher Cratogeomys merriami revealed differences in diploid number that correspond to 3 major genetic and morphological clades within the species. Each of these 3 clades is diagnosable based on multiple characters, including chromosomal diploid number, quantitative and qualitative morphological characters, and mitochondrial DNA. Accordingly, we restrict the name C. merriami (Thomas) to include only pocket gophers of this genus from the states of México, México D.F., northern Morelos, and west-central Puebla. We resurrect the species name C. fulvescens Merriam to represent members of this genus from southern Tlaxcala, east-central Puebla, and parts of west-central Veracruz. Finally, we resurrect the species name C. perotensis Merriam to represent members of this genus from southern Hidalgo, northern Tlaxcala, north-central Puebla, and parts of west-central Veracruz. Based on the observation that differences in diploid number usually signal reproductive isolation between populations of pocket gophers, we hypothesize that C. merriami, C. fulvescens, and C. perotensis are reproductively incompatible. We provide synonymies and descriptions for these 3 species, along with a key to the C. castanops species group to which these species belong. [ABSTRACT FROM AUTHOR]

Presents a report to support evidence that a pocket gopher hybrid zone, which was thought to be approximately 10,000 year old, may only be closer to 50 years old. Findings gathered form historical flood records for the Rio Grande Valley of New Mexico; Information on the consistency of a five-year study of movement of the contact zone between the two species of chewing lice with the hypothesis of the previous origin of the zone.

Thomomys atrovarius is redescribed to include the smooth-toothed pocket gophers that inhabit dry, thornscrub vegetation along the Pacific versant of the Sierra Madre Occidental of Mexico from northern Sinaloa into western Durango, northwestern Jalisco, and western Nayarit. Molecular analyses of mitochondrial and nuclear DNA sequences (including historical samples from museum skins) show high levels of genetic differentiation between T. atrovarius and T. umbrinus of the Sierra Madre Occidental (15.4% cytochrome-b divergence) and Mexican Central Plateau (16.9% divergence). Roughly coincident morphometric and genetic gaps divide T. atrovarius into 2 subspecies, T. a. parviceps in the north and T. a. atrovarius in the south, with probable intergradation in between. Most specimens of T. atrovarius, especially those of the southern subspecies, are distinguished easily from specimens of T. bottae and T. umbrinus on the basis of fur texture, and an analysis of cranial morphometrics shows little overlap between T. atrovarius and other Thomomys clades in Mexico. An analysis of niche parameters shows significantly different climate envelopes for T. atrovarius compared with other species of Thomomys, and a biogeographical review suggests that T. atrovarius has ancestral affinities to the south of its current distribution. A synonymy of T. atrovarius and a key to the currently recognized species of Thomomys in mainland Mexico are provided. [ABSTRACT FROM AUTHOR]

The genus Cratogeomys, particularly members of the Cratogeomys gymnurus species group, account for much of the high species diversity of pocket gophers in the Trans-Mexican Volcanic Belt. Recent molecular studies of this species group have shown strong discordance between genetically defined clades and current species taxonomy. Accordingly, we investigated relationships among the 5 species in the C. gymnurus species group using mitochondrial and nuclear DNA, chromosomes, and morphological characters. Although quantitative morphometrics provided little discrimination among species or clades within this group, the molecular data sets were consistent in identifying 5 allopatric clades, none of which corresponded to any of the 5 currently recognized species. Four of these 5 genetically defined clades lack clear diagnosability, and so are grouped into the single polytypic species, C. fumosus. The fifth clade is diagnosable based on multiple characters, including nuclear genotype, chromosomal diploid number, parasite fauna, and qualitative morphological characters. Accordingly, we resurrect Merriam's (1895) species planiceps to represent members of this clade, which occurs in the Volcán de Toluca and Valle de Bravo regions of central Mexico. Based on the observation that differences in diploid number usually signal reproductive isolation between populations of pocket gophers, we hypothesize that C. fumosus and C. planiceps are reproductively incompatible. We provide synonymies and descriptions for these 2 species, along with a key to this species group, which is now called the C fumosus species group. [ABSTRACT FROM AUTHOR]