Population genomics reveals differences in genetic structure between two endemic arboreal rodent species in threatened cloud forest habitat

Genomic tools are now commonly used to assess the genetic diversity and genetic structure of species and populations, and they provide the ability to describe and address the negative effects of population declines and fragmentation. However, such studies are lacking for arboreal mammals despite their contribution to various ecosystem services, especially in uncommon and critically endangered ecosystems such as cloud forests. The aim of this work was to evaluate and compare the genetic diversity and population structure of two endemic arboreal mice from Mexican cloud forests that are associated with areas with different levels of impacts from human activities. We performed genotyping-by-sequencing in 47 Habromys schmidlyi and 17 Reithrodontomys wagneri individuals to evaluate genetic diversity and differentiation. In both species, the genetic diversity was low compared to other cricetid species, and we observed different population structure patterns, potentially linked to the different ecological associations. We detected two genetic groups in H. schmidlyi, that is a territorial species present in areas of low incline, while a single genetic group was found in R. wagneri, which forms family groups in areas with steep slopes. Overall, these results highlight how species’ genetic diversity can be differentially impacted depending on differential ecological associations within the same ecosystem. This information is essential for the development of the adequate conservation and management of these species.

Assessment differentiation degree cryptic species of the genus Apodemus in the Northern Caucasus based on non-metric cranial characters

A phenetic analysis of non-metric cranial traits of two genetically identified cryptic species of the genus Apodemus in different ecological conditions of the North Caucasus was carried out. The maximum distance obtained between cryptic species did not exceed the level of subspecies differences. The phenetic distance between A. uralensis and A. flavicollis, which inhabit symbiotopically and sympatrically in the Western Caucasus, is almost 2 times lower. The smaller value of phenetic differences is probably related to the habitat of both species in similar land-scapebiotopic and climatic conditions, which contributes to the development of phenotypic similarity. In general, the obtained results indicate weak morphological differentiation of the studied species according to the studied phenetic characters (cranial foramen), although according to the results of molecular genetic analysis of the cyt b gene site, the genetic distance between the studied taxa is 10% and corresponds to the level of interspecific differences. Based on the above, reliable diagnosis of the studied species in the Caucasus is possible only by molecular genetic methods.

Is genetic structure of the southern pygmy mouse Baiomys musculus (Cricetidae) related to human-induced spatial landscape heterogeneity in a tropical dry forest?

Tropical dry forests are biologically important biomes sustaining a high rate of endemic species. However, these forests are highly threatened by human activities that negatively impact them on distinct levels, including the genetic diversity. Within the framework of landscape genetics (that seeks to evaluate the relation of characteristics of the environmental matrix with population genetics), we used ISSR markers to evaluate the relationship between the alteration of tropical dry forest by human-induced activities (conserved vs. disturbed) with the genetic structure of four breeding sites of the southern pygmy mouse Baiomys musculus. Averaging among the 105 loci used, the unbiased heterozygosis per population (0.247-0.305) was statistically similar among the four sites, as well as between conserved and disturbed conditions (2-way ANOVA F ((3,16)) = 1.47, P = 0.1984). The genetic differentiation among the four breeding sites was high (F (ST) = 0.1122; 95 % CI 0.082-0.146) considering the geographical scale evaluated (ca. 4 km). Both, a factorial correspondence analysis and a model-based clustering analysis showed the existence of four genetic groups (one per breeding site). However, no association of genetic structure with disturbance conditions was revealed by these analyses. The absence of differences in mean genetic diversity and the lack of association of genetic structure with habitat transformation suggest that B. musculus has enough behavioral plasticity and enough genetic diversity to respond to environmental heterogeneity caused by human activities. We discussed conditions in which habitat transformation could indeed favor B. musculus.