Combined mitochondrial and nuclear markers revealed a deep vicariant history for Leopoldamys neilli, a cave-dwelling rodent of Thailand

Isolation by geographical distance after release from Pleistocene refugia explains genetic and phenotypic variation in Xylotrupes siamensis (Coleoptera: Scarabaeidae)

Consistent and objective species delimitation is crucial to biodiversity studies, but challenges remain when conflicting taxonomic decisions have been made because different data sets and analytical methods were used to delineate species. In the rhinoceros beetle, Xylotrupes siamensis, the use of different morphological characters has resulted in taxonomic disagreement between studies. We used three molecular loci (mitochondrial CO1 and nuclear ITS2 and H3) to investigate the genetic divergence between populations exhibiting different male horn phenotypes. We also applied an approximate Bayesian computation approach to test alternative historical hypotheses that might explain the present genetic diversity among geographical populations. Furthermore, we used species distribution models to estimate the temporal variation in the geographical distribution of suitable habitats. The results show that the two phenotypic taxa within X. siamensis are not genetically structured and that their genetic structure can be explained using isolation by geographical distance. The emergence of the two phenotypic taxa might have been associated with historical isolation in separate refugia. However, spatial expansion and genetic interchange between populations might have gradually eroded the spatial genetic structure. We demonstrate that understanding the historical processes responsible for phenotypic divergence and genetic diversity among current populations could help with making evolutionarily coherent taxonomic decisions.

"Colonization routes and demographic history of Chirostoma humboldtianum in the central Mexican plateau"

In the present study we evaluate the population structure and potential colonization routes of the silverside Chirostoma humboldtianum through approximate Bayesian computations. Six microsatellite loci were amplified in a total of 288 individuals from six different locations covering the complete geographic distribution of the species. Additionally, two mitochondrial DNA markers, a D loop control region and cytochrome b were amplified in a subset of 107 individuals. The results found with microsatellites allow recovering well-structured populations that have experienced a drastic reduction in the effective population size. On the other hand, mtDNA sequences showed a moderate phylogeographic structure with shared haplotypes between geographic localities and signalsof a slight increase in the effective population size. Finally, the approximate Bayesian computation analysis performed with both datasets suggested a west-to-east colonization route for the species in Central Mexico.

Progress on research on rodents and rodent-borne zoonoses in South-east Asia

This review aims to synthesise knowledge regarding the taxonomy of South-east Asian murine rodents and the challenges associated with the identification of habitat preferences and associated rodent-borne diseases. Recent studies concerning the Rattini tribe have identified unclear species boundaries that would benefit from further investigation. The development of barcoding may allow more accurate identification of rodents, specifically for complex species. However, knowledge on the distribution and habitat specialisations of many common murine rodents is still scarce, particularly regarding the specific habitat preferences of most synanthropic rodent species (Rattus tanezumi or Rattus exulans). Several studies have analysed the prevalence of major rodent-borne diseases in South-east Asia and it appears that the greatest risk of rodent zoonoses are in the lowland rain-fed and irrigated landscapes, generally in and around rice fields.

The complete mitochondrial genome of the Leopoldamys edwardsi (Rodentia: Muridae)

The complete mitochondrial genome of L. edwardsi was first sequenced and characterized. The genome was 16,284 bases in length and the composition and arrangement of its genes are analogous to most other rodents. The nucleotide sequence date of 12 heavy-strand protein-coding genes of L. edwardsi and other 26 Muridae species were used for phylogenetic analyses. Trees constructed using Maximum Likelihood, Neighbor Joining and Minimum Evolution demonstrated that L. edwardsi was closer to the genus Niviventer than Rattus. Combing previous research, it suggests that Edward's long-tailed rat is more suitable to be classified into genus Leopoldamys and named as Leopoldamys edwardsi. This study suggested that R. edwardsi is inappropriate for the other name of L. edwardsi.

Helminth parasite species richness in rodents from Southeast Asia: role of host species and habitat

Southeast Asia is a biodiversity hotspot that harbours many species of rodents, including some that live in close contact with humans. They host helminth parasites, some of which are of zoonotic importance. It is therefore important to understand the factors that influence the richness of the helminths parasitizing rodents. The specific objectives of this study were to evaluate rodent species as a factor determining helminth richness in rodent assemblages, to identify the major rodent helminth reservoir species and to explore the influence of habitat on helminth richness. We estimated helminth species richness using a large dataset of 18 rodent species (1,651 individuals) originating from Southeast Asia and screened for helminth parasites. The use of an unbiased estimator shows that the helminth species richness varies substantially among rodent species and across habitats. We confirmed this pattern by investigating the number of helminth species per individual rodent in all rodent species, and specifically in the two mitochondrial lineages Rattus tanezumi and R. tanezumi R3, which were captured in all habitats.