Geographic Variation in Morphology and Allozymes Within Tree Squirrels, Sciurus Niger and S. Carolinensis, of the Lower Mississippi River Valley.

Geographic variation was studied in fox squirrels, Sciurus niger, and gray squirrels, S. carolinensis, by comparing patterns of differentiation within and between these two sympatric species. Patterns of variation were examined in light of the lower Mississippi River as a potential barrier to dispersal and gene flow in these squirrels. Differences within and between species were analyzed using morphologic (15 cranial and mandibular measurements) and allozymic (35 presumptive gene loci) characters. Geographic patterns of variation among populations were apparent in the morphology and allozymes of both species; patterns of differentiation in morphologic and allozymic characters are similar between species; however, morphologic variation is not congruent with allozymic variation within either species. Fox squirrels and gray squirrels each vary morphologically so that, within each species, individuals that inhabit the Mississippi River floodplain and delta region are smaller than animals from adjacent regions. This size variation may be a nongenetic response to environmental factors, or it may reflect regional differences in selective regimes, and thus may represent genetic variation among populations. Available data are insufficient to distinguish between these two causal mechanisms. Allozymically, fox squirrels and gray squirrels exhibit similar patterns of differentiation; within each species, there are differences among eastern and western populations, as defined by their geographic location relative to the present Mississippi River channel. Thus, the Mississippi River and associated habitats may have been (and may still be) a barrier to gene flow in these species. This study provides considerable evidence that the lower Mississippi River has influenced morphologic differentiation in fox and gray squirrels and that the river has impeded (and may still impede) gene flow in these species. The role of the river as a barrier to dispersal and gene flow may have resulted from direct effects; the Mississippi River may be a substantial physical barrier to tree squirrels. It is also highly likely that the river has affected dispersal and gene flow in tree squirrels indirectly due to environmental and vegetational shifts that occurred in the alluvial valley of the Mississippi River during the late Quaternary

Virginia’s Land Mammals: Past and Present, With Some Thoughts About Their Possible Future

Mammals encountered today in Virginia’s forests and fields include native and nonnative species, feral populations, and free-ranging pets. We examine factors that have influenced Virginia’s terrestrial mammal fauna since the arrival of European colonists in the 1600s and some of the factors that are shaping the fauna today. We look in depth at changes since Handley and Patton’s (1947) first complete monograph on Virginia mammals and augment Linzey’s (1998) book, The Mammals of Virginia. We include current nomenclature, baseline information, and references to comprehensive literature. We discuss some of the current and developing anthropogenic factors that have impacted, or that likely will impact, our native land mammals as well as factors that bode well for many species, especially in areas of conservation of habitat

Multiple origins of melanism in two species of North American tree squirrel ( Sciurus )

Abstract: Background: While our understanding of the genetic basis of convergent evolution has improved there are still many uncertainties. Here we investigate the repeated evolution of dark colouration (melanism) in eastern fox squirrels (Sciurus niger; hereafter “fox squirrels”) and eastern gray squirrels (S. carolinensis; hereafter “gray squirrels”). Results: We show that convergent evolution of melanism has arisen by independent genetic mechanisms in two populations of the fox squirrel. In a western population, melanism is associated with a 24 bp deletion in the melanocortin-1-receptor gene (MC1RΔ24 allele), whereas in a south-eastern population, melanism is associated with a point substitution in the agouti signalling protein gene causing a Gly121Cys mutation. The MC1R∆24 allele is also associated with melanism in gray squirrels, and, remarkably, all the MC1R∆24 haplotypes are identical in the two species. Evolutionary analyses show that the MC1R∆24 haplotype is more closely related to other MC1R haplotypes in the fox squirrel than in the gray squirrel. Modelling supports the possibility of gene flow between the two species. Conclusions: The presence of the MC1R∆24 allele and melanism in gray squirrels is likely due to introgression from fox squirrels, although we cannot completely rule out alternative hypotheses including introgression from gray squirrels to fox squirrels, or an ancestral polymorphism. Convergent melanism in these two species of tree squirrels has evolved by at least two and probably three different evolutionary routes

Systematic Revision of the Northern Short-tailed Shrew, \u3ci\u3eBlarina brevicauda\u3c/i\u3e (Say)

Short-tailed shrews, genus Blarina, are common inhabitants of a variety of terrestrial habitats in most of eastern North America. Of the 4 species currently recognized, the northern short-tailed shrew, Blarina brevicauda (Say, 1823), is the most widely distributed, occurring from southern Canada southward to the central Great Plains and the Appalachian Mountains into Georgia and Alabama and along the East Coast as far south as southeastern North Carolina. It has been more than 65 years since geographic variation within this species has been studied. Accordingly, the objectives of this study were to examine geographic variation in Blarina brevicauda and to revise its intraspecific taxonomy as needed. A total of 12,390 Holocene specimens of Blarina brevicauda from throughout the geographic range of the species and the fossil material of Blarina fossilis, B. ozarkensis, and B. simplicidens were examined during the course of this study. Nine cranial and mandibular measurements were taken from 2,736 Holocene specimens, which were grouped into 114 operational taxonomic units (OTUs) for statistical analysis. We used a single classification ANOVA to test for significant differences among means of OTUs and a principal component analysis (PCA) to extract eigenvectors and generate a 2-dimensional plot of OTUs. Our analysis demonstrates that B. brevicauda consists of 7 well-defined subspecies. Two subspecies, the large-bodied B. b. brevicauda and the medium-sized B. b. talpoides, occupy almost the entire geographic range of the species, with restricted gene flow between these 2 subspecies where their geographic ranges abut in the vicinity of the Mississippi River and its valley. The other 5 subspecies occupy small to modest geographic ranges at the periphery of the range of the species and in isolated geographic areas—an undescribed subspecies on the Cumberland Plateau in Tennessee and adjacent Kentucky, B. b. knoxjonesi along the southeastern coast of North Carolina, another undescribed subspecies on the southern two-thirds of the Delmarva Peninsula, B. b. aloga on Martha’s Vineyard and Nantucket Island, and a third undescribed subspecies in the Kaw River Valley in northeastern Kansas. In each of these geographic areas, gene flow has been stopped or greatly restricted. We have chosen to recognize these 7 subspecies because we believe that each has begun to follow its own evolutionary path. These taxa are arranged in a geographic configuration that fits the pattern termed centrifugal speciation, or the development of small isolated peripheral and sometimes relictual populations as the parent taxon undergoes normal population expansion and contraction cycles. The fact that at least 3 of these peripheral populations are now partially in contact with the parental populations and have not been swamped out genetically indicates to us that they are adapting to their local conditions and are able to maintain their genetic identities. Our morphological data and mitochondrial DNA analyses by other workers indicate that these peripheral subspecies, with the possible exception of the 1 along the Kaw River valley, are derived from B. b. talpoides. These data also indicate that B. b. brevicauda and B. b. talpoides are semi-species. [87 pages

Mammal collections of the Western Hemisphere: A survey and directory of collections

As a periodic assessment of the mammal collection resource, the Systematic Collections Committee (SCC) of the American Society of Mammalogists undertakes decadal surveys of the collections held in the Western Hemisphere. The SCC surveyed 429 collections and compiled a directory of 395 active collections containing 5,275,155 catalogued specimens. Over the past decade, 43 collections have been lost or transferred and 38 new or unsurveyed collections were added. Growth in number of total specimens, expansion of genomic resource collections, and substantial gains in digitization and web accessibility were documented, as well as slight shifts in proportional representation of taxonomic groups owing to increasingly balanced geographic representation of collections relative to previous surveys. While we find the overall health of Western Hemisphere collections to be adequate in some areas, gaps in spatial and temporal coverage and clear threats to long-term growth and vitality of these resources have also been identified. Major expansion of the collective mammal collection resource along with a recommitment to appropriate levels of funding will be required to meet the challenges ahead for mammalogists and other users, and to ensure samples are broad and varied enough that unanticipated future needs can be powerfully addressed. © 2018 The Author(s)

Morphometric and Geographic relationships of Short-Tailed Shrews (Genus Blarina) in Kansas, Iowa, and Missouri

Shrews of the genus Blarina from Iowa, Kansas, and Missouri were studied morphometrically and karyologically. The ranges of the two species, B. brevicauda and B. hylophaga, were found to be sympatric in a broad zone across southern Iowa and northern Missouri. Morphometric analyses revealed an unexpectedly large amount of cranial variation in B. brevicauda, and confirmed the presence of that species in the Kansas River Valley of northeastern Kansas. Considerable mensural overlap was found in geographic areas in which B. hylophaga and B. brevicauda are sympatric, evincing the need for further karyotopic and morphometric studies in those areas

Multiple origins of melanism in two species of North American tree squirrel ( Sciurus )

Abstract: Background: While our understanding of the genetic basis of convergent evolution has improved there are still many uncertainties. Here we investigate the repeated evolution of dark colouration (melanism) in eastern fox squirrels (Sciurus niger; hereafter “fox squirrels”) and eastern gray squirrels (S. carolinensis; hereafter “gray squirrels”). Results: We show that convergent evolution of melanism has arisen by independent genetic mechanisms in two populations of the fox squirrel. In a western population, melanism is associated with a 24 bp deletion in the melanocortin-1-receptor gene (MC1RΔ24 allele), whereas in a south-eastern population, melanism is associated with a point substitution in the agouti signalling protein gene causing a Gly121Cys mutation. The MC1R∆24 allele is also associated with melanism in gray squirrels, and, remarkably, all the MC1R∆24 haplotypes are identical in the two species. Evolutionary analyses show that the MC1R∆24 haplotype is more closely related to other MC1R haplotypes in the fox squirrel than in the gray squirrel. Modelling supports the possibility of gene flow between the two species. Conclusions: The presence of the MC1R∆24 allele and melanism in gray squirrels is likely due to introgression from fox squirrels, although we cannot completely rule out alternative hypotheses including introgression from gray squirrels to fox squirrels, or an ancestral polymorphism. Convergent melanism in these two species of tree squirrels has evolved by at least two and probably three different evolutionary routes

Morphometric and Geographic Relationships of Short-Tailed Shrews (Genus \u3ci\u3eBlarina\u3c/i\u3e) in Kansas, Iowa, and Missouri

Shrews of the genus Blarina from Iowa, Kansas, and Missouri were studied morphometrically and karyologically. The ranges of two species, B. brevicauda and B. hylophaga, overlap in a broad zone across southern Iowa and northern Missouri. Morphometric analyses revealed an unexpectedly large amount of cranial variation in B. brevicauda, and confirmed the presence of that species in the Kansas River Valley of northeastern Kansas. Considerable mensural overlap was found in geographic areas in which B. hylophaga and B. brevicauda are sympatric, evincing the need for further karyotypic and morphometric studies in those areas. No formal taxonomic changes are proposed herein pending further study of these species

Cost-distance analysis of mesopredators as a tool for avian habitat restoration on a naturally fragmented landscape

Removal of mammalian mesopredators is a strategy frequently applied to problems of conservation management, such as protection of rare or endangered species. Effectiveness of predator removal is often dependent on the ease with which additional predators can immigrate into the removal area. We applied cost-distance analysis, coupled to a sensitivity analysis, and least-cost path analysis to raccoons (Procyon lotor) and red foxes (Vulpes vulpes) on the Virginia barrier islands to determine the landscape resistance (i.e., difficulty) for mesopredators to reach individual islands from both mainland and island sources, to assess the relative role of mainland versus island populations as sources of immigrants to unoccupied (or depopulated) islands, and to formulate strategies that focus management efforts on a few key predator sources. The minimum energetic resistances to immigration varied over 3 orders of magnitude, making some islands better targets for removal efforts than others. Additionally, because of differences in the distribution of resident populations on the islands, resistance to immigration to a typical island is at least 3 times less for raccoons than for red foxes. Landscape resistance to red fox immigration is typically lower from the mainland, whereas for raccoons inter-island movements are typically less costly. Empirical data from long-term field studies of raccoons and red foxes in this system support the resistance structure identified. Overwater transits made by marked and resighted raccoons all were relatively short and relatively low-cost. Similarly, islands that were recolonized following the removal of raccoons and red foxes all were characterized by very low resistance values. These results are used to identify specific islands for which predator removal efforts are most likely to be successful in aiding the recovery of beach-nesting and colonial waterbirds in this system. A similar approach may be applied in any landscape where there are distinct differences in the costs of traversing different elements of the landscape

Landscape Genetics of Raccoons (\u3cem\u3eProcyon lotor\u3c/em\u3e) in a Naturally Fragmented Coastal Landscape

We used mitochondrial (mtDNA) and nuclear DNA markers to identify past and present dispersal corridors of raccoons (Procyon lotor) on the Virginia barrier islands and adjacent Delmarva Peninsula mainland. We analyzed a 515-basepair fragment of mtDNA (containing the 3’-end of the cytochrome-b gene, the 5’-end of the d-loop, and the intervening tRNA gene) in 164 animals from 22 localities. We detected 8 unique mtDNA sequences and found north-south differentiation on the islands and on the mainland. To draw inferences about raccoon population dynamics and genetic connectivity, we genotyped 13 nuclear microsatellite loci in 314 individuals from 24 localities. We found complex patterns of spatial population structure and migration rates in this system. These patterns suggested nonequilbrium population-genetic dynamics, potentially caused by recent founding events on the islands and spatial variation in genetic connectivity within this system. Taken together, results of this study suggest that the metapopulation structure of raccoons on the Virginia barrier islands is highly dynamic, with most movement of raccoons occurring among groups of islands that are inter-connected by marsh and relatively shallow, narrow, open-water channels. These results are consistent with our direct observations of overwater movement by raccoons within this system. These genetic data also support predictions from our models based on cost-distance analysis of landscape resistance to movement by raccoons among islands and the mainland