Potential Geographical Barriers Research Articles

Substrate specialisation drives an unexpectedly diverse radiation in barking geckos (Ptenopus: Gekkonidae)

Barking geckos (genus Ptenopus) are terrestrial, burrowing lizards endemic to southern Africa, currently with three recognised species. Two species are range-restricted (P. kochi and P. carpi) and display clear differences in substrate preference (soft sand vs. hard gravel). The third and most widespread species, P. garrulus, occurs on a variety of substrates of differing hardness, across potential geographic barriers, and over a steep climatic gradient. Variations in morphology and advertisement calls indicates that P. garrulus may be a species complex. Two subspecies of P. garrulus are currently recognised: P. g. maculatus and P. g. garrulus. To investigate species boundaries, we produced the first comprehensive phylogeny for the genus. We used a novel application of multiple regression on matrices models to assess multiple environmental drivers of diversification, as contrasted to isolation by distance. We show that P. kochi, P. carpi, and P. g. garrulus are valid species, but that P. g. maculatus is a paraphyletic complex of five previously unrecognised taxa. Specialisation onto different substrates was likely the main driver of divergence, with parapatric occurrence of two to four clades occurring at each of the three substrate transition zones identified a priori. The region encompasses diverse bioclimatic regions and potential geographic barriers, and these likely played a role in some divergence events.

Geography and past climate changes have shaped the evolution of a widespread lizard in arid Central Asia

The complex orogenic history and structure of Central Asia, coupled with Pleistocene glacial cycles have generated its stepwise aridification. Such events would have significantly influenced the evolution of many mid-latitude species in arid Central Asia (ACA). In this study, we employed two mitochondrial genes (CO1 and ND2) and genome-wide SNPs, coupled with ecological niche modeling, to investigate the lineage diversification and historical demography within a widespread lizard Phrynocephalus helioscopus, and their associations with geography and past climate change. We obtained the mtDNA dataset for 300 individuals from 96 localities within the known range of the lizard, among which 51 individuals from 27 localities were selected for generating the SNP dataset via the genotyping-by-sequencing approach. Phylogenetic analyses of the concatenated mtDNA dataset revealed eight geographically correlated lineages that diverged by 4.21–10.41% for the CO1 gene, which were estimated to have coalesced ∼4.47 million years ago. However, we observed mito-nuclear discordance pattern regarding the population of Clade V (P. helioscopus sergeevi) from Tajikistan. Ancestral area estimations suggested that P. helioscopus originated from the Fergana Valley and then dispersed into the adjacent areas in ACA along with a history of multiple allopatric divergence processes, suggesting that Fergana may have been the cradle of diversification of P. helioscopus. The intensification of aridification across Central Asia during the Late Pliocene may have facilitated the rapid radiation of this arid-adapted lizard throughout this vast territory. Subsequently, the geological events (e.g., uplift of the Hissar-Alay, transgressions of the Caspian Sea) and geographic barriers (e.g., Amu Darya River, Zeravshan River) during the Pleistocene triggered the progressive diversification of P. helioscopus. Interestingly, Clade VIII (P. helioscopus varius) experienced rapid population growth coupled with range expansion while Clade IV (P. helioscopus cameranoi) underwent drastic population expansion associated with range contraction during the Last Glacial Maximum. In Clade IV, but not in Clade VIII, environmental turnover contributes more to mitochondrial genetic distinctiveness than geographic distance. Overall, the SNP dataset demonstrates that geographic distance plays a greater role than environmental distance. Both the mtDNA dataset and the SNP dataset suggest local-scale genetic differentiation in Clade IV and Clade VIII, revealing potential geographic barriers in the Ili River Valley and the Junggar Basin, respectively. Twenty-seven outlier SNPs associated with environmental factors (precipitation and temperature) were identified, which supports the signature of local adaptation to the arid desert environment. Finally, our finding suggests taxonomic implications, such as support for full species status for P. saidalievi (Clade II) and P. meridionalis (Clade I). Future analyses based on further evidence and increased taxon and geographic sampling should be carried out to corroborate our findings.

Actual status and future directions of cardiac telerehabilitation.

Telerehabilitation (TR) was developed to achieve the same results as would be achieved by the standard rehabilitation process and to overcome potential geographical barriers and staff deficiencies. This is especially relevant in periodic crisis situations, including the recent COVID-19 pandemic. Proper execution of TR strategy requires both well-educated staff and dedicated equipment. Various studies have shown that TR may have similar effects to traditional rehabilitation in terms of clinical outcomes and may also reduce total healthcare costs per participant, including rehospitalization costs. However, as with any method, TR has its advantages and disadvantages, including a lack of direct contact or prerequisite, rudimentary ability of the patients to handle mobile devices, among other competencies. Herein, is a discussion of the current status of TR, focusing primarily on cardiac TR, describing some technical/organizational and legal aspects, highlighting the indications, examining cost-effectiveness, as well as outlining possible future directions.

ROLE OF SOCIAL MEDIA IN COVID PANDEMIC; A BOON OR BANE ???

The Covid-19 pandemic has struck at a moment when the natural world is more intertwined than ever before. It's the rst pandemic of the digital era, and never before has it been possible to communicate and stay connected so swiftly during a pandemic.Though physical connectivity has hastened the disease's spread over the globe due to extensive travel, social media connectivity is a tool that, when utilised properly and judiciously, can inuence people's behaviour and enhance individual’s and global health.These social media portals may be used to quickly broadcast signicant new information, relevant new scientic results, discuss diagnosis, treatment, and follow-up protocols, and evaluate alternative techniques globally, removing potential geographic barriers. Simultaneously, a massive volume of potentially harmful misinformation is spreading at a faster rate via social media than the disease itself. As a result, it is vital to give timely, reliable, and trustworthy information addressing critical infection control issues. In this review, we present the most signicant facts on the impact, benets, and drawbacks of using social networks during the COVID-19 pandemic .

King or royal family? Testing for species boundaries in the King Cobra, Ophiophagus hannah (Cantor, 1836), using morphology and multilocus DNA analyses

In widespread species, the diverse ecological conditions in which the populations occur, and the presence of many potential geographical barriers through their range are expected to have created ample opportunities for the evolution of distinct, often cryptic lineages. In this work, we tested for species boundaries in one such widespread species, the king cobra, Ophiophagus hannah (Cantor, 1836), a largely tropical elapid snake distributed across the Oriental realm. Based on extensive geographical sampling across most of the range of the species, we initially tested for candidate species (CS) using Maximum-Likelihood analysis of mitochondrial genes. We then tested the resulting CS using both morphological data and sequences of three single-copy nuclear genes. We used snapclust to determine the optimal number of clusters in the nuclear dataset, and Bayesian Phylogenetics and Phylogeography (BPP) to test for likely species status. We used non-metric multidimensional scaling (nMDS) analysis for discerning morphological separation. We recovered four independently evolving, geographically separated lineages that we consider Confirmed Candidate Species: (1) Western Ghats lineage; (2) Indo-Chinese lineage (3) Indo-Malayan lineage; (4) Luzon Island lineage, in the Philippine Archipelago. We discuss patterns of lineage divergence, particularly in the context of low morphological divergence, and the conservation implications of recognizing several endemic king cobra lineages.

Changes in species composition of Haploniscidae (Crustacea: Isopoda) across potential barriers to dispersal in the Northwest Pacific

Speciation processes as drivers of biodiversity in the deep sea are still not fully understood. One potential driver for species diversification might be allopatry caused by geographical barriers, such as ridges or trenches, or physiological barriers associated with depth. We analyzed biodiversity and biogeography of 21 morphospecies of the deep-sea isopod family Haploniscidae to investigate barrier effects to species dispersal in the Kuril-Kamchatka Trench (KKT) area in the Northwest (NW) Pacific. Our study is based on 2652 specimens from three genera, which were collected during the German-Russian KuramBio I (2012) and II (2016) expeditions as well as the Russian-German SokhoBio (2015) campaign. The sampling area covered two potential geographical barriers (the Kuril Island archipelago and the Kuril-Kamchatka Trench), as well as three depth zones (bathyal, abyssal, hadal). We found significant differences in relative species abundance between abyssal and hadal depths. Haploniscus belyaevi Birstein, 1963 was the dominant species at abyssal stations while H. hydroniscoides Birstein, 1963 was prevalent in the hadal. Species composition also differed significantly across geographical barriers. While H. hydroniscoides was the most abundant species in the open NW Pacific, not a single specimen of this species was found in the Sea of Okhotsk, which is separated from the Pacific basin by the Kuril Islands. Furthermore, H. belyaevi and two morphologically highly similar morphospecies were the only species found in samples from the Sea of Okhotsk, meaning that the other 18 species, which we identified from our samples, did not occur west of the Kuril Islands. In this study, haploniscid species show very diverse patterns in geographic distribution between geographic areas and with depth. Therefore, the KKT might have an isolating effect on both the bathymetric as well as geographic distribution of some haploniscid species from the NW Pacific into the Sea of Okhotsk and from the western to the eastern abyssal margin of the KKT.

Weak Genetic Differentiation among Populations of the Andean Ground Beetle Pelmatellus columbianus (Reiche, 1843) (Coleoptera: Carabidae)

Paramo is a fragmented alpine ecosystem above the tree line in the Tropical Andes that is characterized by high species endemism. The genetic diversity of beetle populations present in paramo is poorly understood. I evaluated the effects of potential geographical barriers, genetic structure, and diversification rates on the genetic diversity of Pelmatellus columbianus (Reiche), a widely distributed ground beetle species, and examined if populations show any signs of becoming more restricted to higher elevations due to climate warming. To understand the distribution of genetic variation in P. columbianus, one nuclear and one mitochondrial gene from 87 individuals from eight paramo sites in the Ecuadorian Andes were analyzed using phylogenetics, population genetics, and ecological niche modeling (past and present). These analyses show weak genetic differentiation among populations of P. columbianus that have a high level of genetic connectivity across sites, with dominant haplotypes recorded across the species range. Results suggest that the ability of this species to disperse has limited its genetic differentiation in specialized paramo environments, consistent with records that indicate that P. columbianus is not restricted to paramo, but its distribution extends into inter-Andean valleys.

A population-based analysis of urban-rural disparities in advanced pancreatic cancer management and outcomes.

Given the significant morbidity burden associated with advanced pancreatic cancer (APC), its management is complex and frequently requires multidisciplinary care. Because of potential geographical barriers to healthcare access, we aimed to determine the effect of rurality on management and outcomes of APC patients. Patients diagnosed with APC from 2008 to 2015 and received Gemcitabine (Gem), Gemcitabine plus nab-Paclitaxel (Gem/Nab), or FOLFIRINOX at any 1 of 6 British Columbia cancer centers across the province were reviewed. Using postal codes, the Google Maps Distance Matrix determined the distance from each patient's residence to the closest cancer center. Rural and urban status were defined as patients living ≥ 100 and < 100km from the closest treatment site, respectively. Univariate and Cox regression analyses were applied to examine whether rurality resulted in variations in management and outcomes. In total, we identified 659 patients: median age 68 years, 54.3% men, and 76.6% metastatic disease. For treatment, 67.7, 9.2, and 23.0% received Gem, Gem/Nab, and FOLFIRINOX, respectively. However, there were no differences in baseline clinical characteristics between rural and urban patients (all p > 0.05). Also, there were no significant variations in treatment patterns. For example, time from diagnosis to oncology appointment and time from appointment to treatment were 31.5 and 29.5days for ruralpatients and 28.6 and 40.1days for urbanpatients, respectively (all p > 0.05). Use of Gem/Nab (10.1% vs 9.1%) and FOLFIRINOX (21.0% vs 23.5%) were similar regardless of rurality. In multivariate Cox regression, risk of death was similar between rural and urban groups (HR 0.864, 95% CI 0.619-1.206, p = 0.09). Our findings suggest that there is no correlation between rurality and outcomes in APC. The strategic and geographic allocation of cancer care delivery across the province of British Columbia may serve as a model for other jurisdictions that experience disparities in the outcomes of cancers that often require complex multidisciplinary care.

Phylogeography of the sandy beach amphipod Haustorioides japonicus along the Sea of Japan: Paleogeographical signatures of cryptic regional divergences

Recent findings of genetic breaks within apparently continuous marine populations challenge the traditional vicariance paradigm in population genetics. Such “invisible” boundaries are sometimes associated with potential geographic barriers that have forced divergence of an ancestral population, habitat discontinuities, biogeographic disjunctions due to environmental gradients, or a combination of these factors. To explore the factors that influence the genetic population structure of apparently continuous populations along the Sea of Japan, the sandy beach amphipod Haustorioides japonicus was examined. We sampled a total of 300 individuals of H. japonicus from the coast of Japan, and obtained partial sequences of the mitochondrial COI gene. The sequences from 19 local populations were clustered into five groups (Northwestern Pacific, Northern, Central, Southern Sea of Japan, and East China Sea) based on a spatial genetic mixture analysis and a minimum-spanning network. AMOVA and pairwise Fst tests further supported the significant divergence of the five groups. Phylogenetic analysis revealed the relationship among the haplotypes of H. japonicus and outgroups, which inferred the northward range expansion of the species. A relaxed molecular-clock Bayesian analysis inferred the early-to middle-Pleistocene divergence of the populations. Among the five clusters, the Central Sea of Japan showed the highest values for genetic diversity indices indicating the existence of a relatively stable and large population there. The hypothesis is also supported by Bayesian Skyline Plots that showed sudden population expansion for all the clusters except for Central Sea of Japan. The present study shows genetic boundaries between the Sea of Japan and the neighboring seas, probably due to geographic isolation during the Pleistocene glacial periods. We further found divergence between the populations along the apparently continuous coast of the Sea of Japan. Historical changes in the geographic range of H. japonicus in relation to sandy beach habitat availability, account for the genetic breaks among the three populations in the Sea of Japan. The present results infer that the past geographic events influenced the population formation of H. japonicus.

A population-based analysis of urban-rural disparities in advanced pancreatic cancer (APC) management and outcomes.

e18049 Background: The high morbidity burden associated with APC means that its management is complex and frequently requires multidisciplinary care. Because of potential geographical barriers to healthcare access, we aimed to determine the effect of rurality on management and outcomes of APC patients. Methods: Patients diagnosed with APC (locally advanced or metastatic disease) from 2008 to 2015 and received gemcitabine (gem), gem plus nabpaclitaxel (gem/nab), or FOLFIRINOX at any 1 of 6 British Columbia cancer centers were reviewed. Using postal codes, the Google Maps Distance Matrix determined the distance from each patient’s residence to the closest cancer center. Rural and urban status were defined as patients living &gt; / = 100 km and &lt; 100 km to the closest treatment site, respectively. Different cut points were used in sensitivity analyses. Patients were also stratified according to Canadian census population sizes. Univariate and Cox regression analyses were applied to examine whether rurality resulted in variations in management and outcomes. Results: In total, we identified 659 patients: median age 68 years, 54.3% men, and 45.7% metastatic disease. Among them, 19.3% lived rurally. For treatment, 67.7%, 9.2%, and 23.1% received gem, gem/nab, and FOLFIRINOX, respectively. There were no differences in baseline clinical characteristics between rural and urban patients (all p &gt; 0.05). Time from diagnosis to oncology appointment and time from appointment to treatment were 31.5 and 29.5 days for rural patients and 28.6 and 40.1 days for urban patients, respectively (all p &gt; 0.05). In multivariate Cox regression, risk of death was similar between rural and urban groups (HR 0.864, 95% CI 0.619-1.206, p = 0.390). Furthermore, regression analysis found that population size did not pose a signficiant impact on APC outcomes (all p &gt; 0.05). Conclusions: There was no correlation between rurality and outcomes in APC. The strategic and geographic allocation of cancer care delivery across 6 comprehensive treatment centers in British Columbia may serve as a model for other jurisdictions, particularly those that currently face outcome disparities in cancers that often require complex multidisciplinary care

A population-based analysis of urban-rural disparities in advanced pancreatic cancer (APC) management and outcomes.

254 Background: Given the significant morbidity burden associated with APC, its management is complex and frequently requires multidisciplinary care. Because of potential geographical barriers to healthcare access, we aimed to determine the effect of rurality on management and outcomes of APC patients. Methods: Patients diagnosed with APC (locally advanced or metastatic disease) from 2008 to 2015 and received gemcitabine (gem), gem plus nab-paclitaxel (gem/nab), or FOLFIRINOX at any 1 of 6 British Columbia cancer centers across the province were reviewed. Using postal codes, the Google Maps Distance Matrix determined the distance from each patient’s residence to the closest cancer center. Rural and urban status were defined as patients living &gt;= 100 km and &lt; 100 km from the closest treatment site, respectively. Univariate and Cox regression analyses were applied to examine whether rurality resulted in variations in management and outcomes. Results: In total, we identified 667 patients: median age 68 years, 54.3% men, and 45.7% metastatic disease. Among them, 19.5% lived rurally and 80.5% resided in urban areas. For treatment, 67.8%, 9.4%, and 22.8% received gem, gem/nab, and FOLFIRINOX, respectively. However, there were no differences in baseline clinical characteristics between rural and urban patients (all p &gt; 0.05). Also, there were no significant variations in treatment patterns. For example, time from diagnosis to oncology appointment and time from appointment to treatment were 31.6 and 29.5 days for rural patients and 28.7 and 39.9 days for urban patients, respectively (all p &gt; 0.05). Use of gem/nab (9.8 vs 9.4%) and FOLFIRINOX (20.5 vs 23.3%) were similar regardless of rurality. In multivariate Cox regression, risk of death was similar between rural and urban groups (HR 1.34, 95% CI 0.95-1.87, p = 0.09). Conclusions: Our findings suggest that there is no correlation between rurality and outcomes in APC. The strategic and geographic allocation of cancer care delivery across the province of British Columbia may serve as a model for other jurisdictions that experience disparities in the outcomes of cancers that often require complex multidisciplinary care.

Cryptic diversity concealed in the Andean cloud forests: two new species of rainfrogs (Pristimantis) uncovered by molecular and bioacoustic data

Two new species of frogs previously confused with Pristimantis calcarulatus are identified using molecular phylogenetics and described using an integrative taxonomic approach. The species are distributed in montane cloud forests of the northwestern Ecuadorian Andes. Pristimantis pahuma n. sp. and Pristimantis cedros n. sp. differ from their closest relatives by strongly supported reciprocal monophyly in mitochondrial genetic data (16S). Additionally, the genetic distance among P. cedros n. sp., P. pahuma n. sp. and P. calcarulatus (sensu stricto) is 7.1–9.5%. The advertisement call of P. pahuma n. sp. also differs from that of P. calcarulatus; the former emits single-note calls irregularly, whereas P. calcarulatus always calls in a series of 8–24 notes (calls for P. cedros n. sp. not recorded). Morphologically, the three species are almost undistinguishable; however, P. cedros n. sp. differs in life by having an iris with more numerous and smaller black reticulations, whereas the other two species have larger and fewer reticulations. Biogeographically, P. cedros n. sp. is separated from P. pahuma n. sp. and P. calcarulatus by the climatically dry and low elevation Río Guayllabamba Valley, which acts as a strong barrier to dispersal in these frogs. The results of this and other studies suggest that the true species richness of Pristimantis in the Andes is vastly underestimated. This underestimation may lead to declining protection for such cryptic species, many of which have smaller ranges than previously assumed. Species distributed across potential geographic barriers should be studied to detect the existence of cryptic species.

Taxonomic revision of the Andean leaf-eared mouse, Phyllotis andium Thomas 1912 (Rodentia: Cricetidae), with the description of a new species.

The Andean Leaf-eared mouse, Phyllotis andium Thomas 1912, has been considered a widespread medium-size sigmodontine rodent (230 mm of total length and 35 grams approximately) that occurs from Tungurahua, Ecuador, through the Andes, to Lima, Peru. Previous studies performed on Phyllotis noted evidence of morphological geographical variation within the species, which is likely because of the several potential geographical barriers that exist within the distribution range of P. andium. We carried out a taxonomic revision of this species based on qualitative and quantitative morphological analyses of 330 specimens from 92 localities. This included appropriate comparisons with other species of the andium/amicus group and performed molecular analysis based on cytochrome b sequences. As a result, morphologic qualitative analysis suggested the recognition of three different taxa, which are supported by morphologic quantitative and molecular analyses. The three taxa here identified have allopatric distributional ranges separated by important geographic barriers. Following these identification criteria, P. andium is now recognized for the samples from Tungurahua, Ecuador to Huánuco, Peru, and includes melanius and fruticicolus as synonymous; the southern populations from the Ancash and Lima departments, in the western Peruvian Andes, are proposed to represent a new species; and we recognize P. stenops as a valid species with tamborum as a synonym. Finally, we postulate that the diversification of these three species is related to key events in the Andean orogeny.

Distribution of tolypeutes illiger, 1811 (xenarthra: cingulata) with comments on its biogeography and conservation.

This study reviews the data available on the distribution of three-banded armadillos of the genus Tolypeutes, identifying potential geographic barriers and evaluating possible biogeographic processes that may account for the present-day distribution of the species and its conservation status. The database was derived from published records, interviews, and voucher specimens, over a timescale ranging from the fossil record to specimens collected in 2013. A total of 236 localities were recorded, with 68 attributed to Tolypeutes matacus and 168 to Tolypeutes tricinctus. The vegetation within the range of the genus is predominantly a xerophytic mosaic of grassland, savannas, open woodland, and xeric thorn forest. The marine transgressions of the Miocene and the uplifting of the Brazilian Shield may have contributed to the vicariant separation of the ancestral populations of T. matacus, to the west and south, and T. tricinctus, to the north and east. The three-banded armadillo is possibly one of the most threatened of Brazilian mammals, considering the low number of recent records and the fact that it is hunted intensively throughout its range.

Seasonal Movement Patterns and Long-Range Dispersal of Asian Citrus Psyllid in Florida Citrus.

The Asian citrus psyllid, Diaphorina citri Kuwayama, is the vector of the bacterial pathogen, Candidatus Liberibacter asiaticus, which is the causal agent of huanglongbing (HLB) in the United States. Both short-range and long-range dispersal of D. citri adults affect the spread of HLB; however, little is known about the long-range dispersal capabilities of D. citri in the field or the seasonality of flight behavior. In the present study, an in situ protein marking technique was used to determine the dispersal of D. citri by trapping marked adults under natural field conditions. D. citri movement from abandoned citrus groves to adjacent managed citrus groves was greatest during the spring and summer months and decreased significantly during the colder months (September-March). D. citri were able to traverse potential geographic barriers such as roads and fallow fields. In an experiment conducted to determine long-range dispersal capacity in the absence of severe weather events, D. citri were able to disperse at least 2 km within 12 d. Wind direction was not correlated with the number of marked psyllids captured, indicating substantial flight capability by D. citri. Finally, the number of marked psyllids captured increased with the density of emerging young leaves on surrounding trees. The results confirm that abandoned citrus groves in Florida serve as reservoirs for D. citri, which can disperse across long distances despite geographical barriers.

Biogeographic patterns, origin and speciation of the endemic birds from eastern Brazilian mountaintops: a review

We review the main biogeographic and phylogenetic hypotheses about the origin and distribution of the endemic birds from Brazilian mountaintops, a heterogeneous group composed of hummingbirds and passerines living in high-altitude open habitats of campos rupestres, campos de altitude and campos sulinos from southern to north-eastern Brazilian mountaintops (Espinhaço Range, Serra do Mar, Serra da Mantiqueira and Serra Geral). Some authors consider that these birds are probably closely related to other species distributed in cooler areas of South America. We used ranges of these birds, spatial pattern and discontinuities in the distribution of phytophysiognomies to determine potential geographic barriers to dispersal and centres of origin and speciation. We reanalysed biogeographical hypotheses regarding the evolution of the endemic birds from Brazilian mountaintops and their habitats in the light of recent phylogenetic reconstructions that included some of these species. The evolutionary histories of the species Augastes scutatus, Augastes lumachella, Formicivora grantsaui, Polystictus superciliaris and Embernagra longicauda are difficult to assess due to lack of phylogenies that establish their systematic position. For Asthenes luizae, Asthenes moreirae, Cinclodes pabsti and C. espinhacensis, the phylogenies estimate also their lineage divergence times, which allows for inferences concerning connections between the biota of eastern Brazil, southern South America and the Andean mountains. We also identified 26 lowland regions between the mountains that were potentially barriers to dispersal. Phylogenetic relationships strongly highlight the importance of connecting paths and speciation through the south, especially in the cooler areas in South America. These patterns show that eastern Brazil, southern South America and the central and northern Andes are four important centres of origin and radiation for the endemic birds from the eastern Brazilian mountains.

Phylogeography of the Scaled Quail in the American Southwest

We used sequences from the mitochondrial control region to examine the phylogeography and historical demography of the Scaled Quail and to determine whether the geographic distributions of mtDNA genealogy were concordant with the distribution of the subspecies. Overall, the Scaled Quail exhibited lower haplotype and nucleotide diversity than other quail species. The highest levels of haplotype diversity were found in 3 Texas counties: Dimmit, La Salle, and Hudspeth. The Scaled Quail exhibited no phylogeographic structure among its 16 haplotypes, and the patterns of genetic variation were not congruent with potential geographic barriers or current subspecies taxonomy. The geographic distribution of haplotypes and partitioning of molecular variation suggested slight genetic differentiation between the chestnut-bellied subspecies of Scaled Quail and the 3 western subspecies. The low levels of genetic diversity and the evidence of demographic expansion suggest that the Scaled Quail has undergone population and range expansion from a Pleistocene refugium. The greater genetic diversity within the Chestnut-bellied Quail may indicate the geographic location of the refugium.

The role of chromosomal rearrangements and geographical barriers in the divergence of lineages in a South American subterranean rodent (Rodentia: Ctenomyidae: Ctenomys minutus)

Identifying factors and the extent of their roles in the differentiation of populations is of great importance for understanding the evolutionary process in which a species is involved. Ctenomys minutus is a highly karyotype-polymorphic subterranean rodent, with diploid numbers ranging from 42 to 50 and autosomal arm numbers (ANs) ranging from 68 to 80, comprising a total of 45 karyotypes described so far. This species inhabits the southern Brazilian coastal plain, which has a complex geological history, with several potential geographical barriers acting on different time scales. We assessed the geographical genetic structure of C. minutus, examining 340 individuals over the entire distributional range and using information from chromosomal rearrangements, mitochondrial DNA (mtDNA) sequences and 14 microsatellite loci. The mtDNA results revealed seven main haplogroups, with the most recent common ancestors dating from the Pleistocene, whereas clustering methods defined 12 populations. Some boundaries of mtDNA haplogroups and population clusters can be associated with potential geographical barriers to gene flow. The isolation-by-distance pattern also has an important role in fine-scale genetic differentiation, which is strengthened by the narrowness of the coastal plain and by common features of subterranean rodents (that is, small fragmented populations and low dispersal rates), which limit gene flow among populations. A step-by-step mechanism of chromosomal evolution can be suggested for this species, mainly associated with the metapopulation structure, genetic drift and the geographical features of the southern Brazilian coastal plain. However, chromosomal variations have no or very little role in the diversification of C. minutus populations.

Mitochondrial DNA Assessment of the Phylogeography of the Gopher Tortoise

Abstract Identifying geographic barriers that define genetic structure within a species is crucial in formulating an effective conservation plan. The identification of appropriate management units is critical for the protection and recovery of the gopher tortoise Gopherus polyphemus, which have declined across their entire range. Previous molecular work at various spatial scales has identified distinct population assemblages of the gopher tortoise. The goal of this study was to assess the genetic structure in gopher tortoises through a more complete sampling of the federally listed as threatened portion of the range and evaluate the extent of genetic isolation imposed by several potential geographic barriers. We sequenced a 712–base-pair portion of a mitochondrial gene (NADH dehydrogenase 4) for 322 individuals from 42 sites across the range. We found two major assemblages of haplotypes separated by a modest phylogenetic break (average uncorrected p distance = 0.015). The biogeographic barrier that best...

Inferences of selection and migration in the Danish house mouse hybrid zone

We analysed the patterns of allele frequency change for ten diagnostic autosomal allozyme loci in the hybrid zone between the house mouse subspecies Mus musculus domesticus and M. m. musculus in central Jutland. After determining the general orientation of the clines of allele frequencies, we analysed the dine shapes along the direction of maximum gradient. Eight of the ten clines are best described by steep central steps with coincident positions and an average width of 8.9 km (support limits 7.6-12.4) flanked by tails of introgression, indicating the existence of a barrier to gene flow and only weak selection on the loci studied. We derived estimates of migration from linkage disequilibrium in the centre of the zone, and by applying isolation by distance methods to microsatellite data from some of these populations. These give concordant estimates of σ = 0.5-0.8 km generation -1/2 . The barrier to gene flow is of the order of 20 km (support limits 14-28), and could be explained by selection of a few per cent at 43-120 under-dominant loci that reduces the mean fitness in the central populations to 0.45. Some of the clines appear symmetrical, whereas others are strongly asymmetrical, and two loci appear to have escaped the central barrier to gene flow, reflecting the differential action of selection on different parts of the genome. Asymmetry is always in the direction of more introgression into musculus, indicating either a general progression of domesticus into the musculus territory, possibly mediated by differential behaviour, or past movement of the hybrid zone in the opposite direction, impeded by potential geographical barriers to migration in domesticus territory.