Rudyk, A. I. | bioRxiv Science

bioRxiv2024

Genetic diversity and fine-scale structure of two populations of a subterranean rodent, Ellobius talpinus

Subterranean rodents represent an interesting model system for molecular ecologists. Their lifestyle is associated with fragmented environments, limited dispersal ability, and low fecundity. These characteristics all are expected to increase inter- and intrapopulation differentiation and reduce intra- population genetic diversity, yet the published empirical data revealed the lack of generality of this pattern. This emphasizes the importance of accumulating more data on individual species to understand what factors shape the genetic dynamics of populations. This study represents the first characterization of the population genetic diversity and fine-scale genetic structure of a highly specialized subterranean vole, Ellobius talpinus. We used nine microsatellite loci and a fragment of the mitochondrial D-loop to investigate genetic patterns of two distant populations: the Novosibirsk population at the extreme northeastern edge of the species range, and the sub-peripheral Saratov population. As a result, the two populations exhibit distinct patterns of genetic structure. The Novosibirsk population showed a low nuclear diversity with an observed heterozygosity (Ho) of 0.34 and an unbiased expected heterozygosity (uHe) of 0.55. Mitochondrial D-loop was nearly monomorphic with over 90% of the observed haplotypes being identical, resulting in a haplotype diversity (Hd) of 0.14 and nucleotide diversity ({pi}) of 0.0004. In contrast, the Saratov population displayed moderate nuclear (Ho = 0.64; uHe = 0.76) and high mitochondrial variation (Hd = 0.83;{pi} = 0.034), compared to the surface-dwelling voles. Nine haplotypes representing four well-differentiated mitochondrial clades were found in the Saratov population. In a heterogeneous landscape, significant genetic differentiation was revealed at both intermediate (dozens of kilometers) and fine (several kilometers) scales. However, within the continuous suitable habitat, no fine-scale spatial structure was observed apart from that caused by kin clustering. The spatial genetic patterns revealed in E. talpinus appear to reflect a combination of effects of strong social structure, local natural and anthropogenic barriers limiting dispersal opportunities, and occasional long-distance dispersal.

zoology↗

bioRxiv2024

Dental radiography as a low-invasive field technique to estimate age in small rodents, with the mole voles (Ellobius) as an example

Most studies which deal with natural populations require a reliable and convenient way of age estimation. However, even rough aging of live individuals is often a real challenge. In this study, we develop a radiographic method of age estimation in Ellobius talpinus, a promising model species for population and behavioral ecology. Using a portable X-ray equipment, we radiographed wild, non-sedated animals from the population that had been subjected to extensive mark-recaptures for 3 years. Two molar metrics strongly dependent on age and easy to measure on radiographs were selected: the lengths of synclinal folds of the 1st upper and 1st lower molars. No influence of sex on the molar condition age dynamics was found. Discriminant function analysis based on molar condition and date of radiography in 86 animals of known age classes assigned X-ray images to three age classes (young of the year, yearlings, and 2 years or older) with an accuracy of 99%. Leave-one-out cross-validation yielded 97% of correct assignments. All age estimates for 52 repeatedly radiographed individuals were consistent across images. The analysis of the repeated X-ray images obtained from the same animals showed that 1st lower molars change faster in the first summer of life than later whereas the change rate of the 1st upper molars decreases little throughout life. We propose X-ray technique as a useful alternative to direct skull and dental morphometry for age estimation of wild small mammals, saving the investigators time and lives of animals.

zoology↗