Micro-endemic species of snails and amphipods show population genetic structure across very small geographic ranges.

Understanding variation in population genetic structure, even across small distances and for species with extremely limited ranges, is critical for conservation planning and the development of effective management strategies for imperiled species. Organisms that occupy the same geographic extent can maintain different population structures, ranging from highly diverged to panmictic. Such differences can result from differences in biological characteristics such as dispersal ability or demographic history. We used microsatellite loci to evaluate population genetic structure and variation of four desert spring invertebrates having high to low dispersal ability: the lung snail Physa acuta, two species of gilled snails (Juturnia kosteri and Pyrgulopsis roswellensis; family Hydrobiidae) and the amphipod Gammarus desperatus. The study location represents entire species ranges for the micro-endemic hydrobiids and G. desperatus, while P. acuta is ubiquitous throughout much of North America. We found little evidence of significant population genetic structure for P. acuta and J. kosteri, but much more for P. roswellensis and G. desperatus. Our results demonstrate differences in habitat preference and/or dispersal ability between the species. This information provides insight into how gene flow shapes varying population genetic structure between species across small spatial scales (<100 km2). Most importantly, our results suggest that conservation agencies should not consider these micro-endemic species to be composed of single populations, but rather, that management plans for such species should account for population genetic variation across the species' ranges.

Pliocene-Early Pleistocene Geological Events Structure Pacific Martens (Martes caurina).

The complex topography, climate, and geological history of Western North America have shaped contemporary patterns of biodiversity and species distributions in the region. Pacific martens (Martes caurina) are distributed along the northern Pacific Coast of North America with disjunct populations found throughout the Northwestern Forested Mountains and Marine West Coast Forest ecoregions of the West Coast. Martes in this region have been classified into subspecies; however, the subspecific designation has been extensively debated. In this study, we use genomic data to delineate conservation units of Pacific marten in the Sierra-Cascade-Coastal montane belt in the western United States. We analyzed the mitochondrial genome for 94 individuals to evaluate the spatial distribution and divergence times of major lineages. We further genotyped 401 individuals at 13 microsatellite loci to investigate major patterns of population structure. Both nuclear and mitochondrial DNA suggest substantial genetic substructure concordant with historical subspecies designations. Our results revealed that the region contains 2 distinct mitochondrial lineages: a Cascades/Sierra lineage that diverged from the Cascades/coastal lineage 2.23 (1.48-3.14 mya), consistent with orogeny of the Cascade Mountain chain. Interestingly, Pacific Martes share phylogeographic patterns similar with other sympatric taxa, suggesting that the complex geological history has shaped the biota of this region. The information is critical for conservation and management efforts, and further investigation of adaptive diversity is warranted following appropriate revision of conservation management designations.

Influence of atrazine on the scalation of Marcy's checkered gartersnake, Thamnophis m. marcianus (Baird and Girard, 1853).

Atrazine is one of the most commonly used herbicides in the United States. Despite the effectiveness of atrazine in eliminating broadleaf and grassy weeds, there has been growing concern over the potential impacts this chemical may have on non-target organisms. Little research has been conducted on the exposure of reptiles to this chemical. Our study examined the effects of environmentally relevant concentrations of atrazine on the scalation of Marcy's checkered gartersnake (Thamnophis m. marcianus). Our results indicate that atrazine exposure influences scalation, in particular, cranial scale counts. In addition, this alteration of morphology happens during embryological development as the result of the environment the mother was raised in. Further research on additional species and developmental exposure of atrazine and how it influences fitness of reptiles is required.