The Black Rat (Rattus rattus) spread out of Asia to become one of the world's worst agricultural and urban pests, and a reservoir or vector of numerous zoonotic diseases, including the devastating plague. Despite the global scale and inestimable cost of their impacts on both human livelihoods and natural ecosystems, little is known of the global genetic diversity of Black Rats, the timing and directions of their historical dispersals, and the risks associated with contemporary movements. We surveyed mitochondrial DNA of Black Rats collected across their global range as a first step towards obtaining an historical genetic perspective on this socioeconomically important group of rodents. We found a strong phylogeographic pattern with well-differentiated lineages of Black Rats native to South Asia, the Himalayan region, southern Indochina, and northern Indochina to East Asia, and a diversification that probably commenced in the early Middle Pleistocene. We also identified two other currently recognised species of Rattus as potential derivatives of a paraphyletic R. rattus. Three of the four phylogenetic lineage units within R. rattus show clear genetic signatures of major population expansion in prehistoric times, and the distribution of particular haplogroups mirrors archaeologically and historically documented patterns of human dispersal and trade. Commensalism clearly arose multiple times in R. rattus and in widely separated geographic regions, and this may account for apparent regionalism in their associated pathogens. Our findings represent an important step towards deeper understanding the complex and influential relationship that has developed between Black Rats and humans, and invite a thorough re-examination of host-pathogen associations among Black Rats.
Phylogeographic reconstructions of codistributed taxa can help reveal the interplay between abiotic factors, such as altitude and climate, and species-specific attributes, in shaping patterns of population genetic structure. Recent studies also demonstrate the value of both rangewide sampling and species distribution modelling (SDM) in comparative phylogeography. Here, we combine these approaches to study the population histories of four phylogenetically related forest-dependent bat species. All are endemic to the mountainous island of Taiwan but show differences in their tolerance to altitude, with Murina gracilis considered to be a high-altitude specialist, M. recondita and Kerivoula sp. low-altitude specialists, and M. puta an altitudinal generalist. We tested the prediction that contrasting habitat preferences would impact on patterns of past and contemporary gene flow and found broad concordance between the results of population genetic analyses and species distribution models based on the Model for Interdisciplinary Research on Climate. Both lowland species showed evidence of genetic divergence between the east and west of the island, consistent with SDMs that indicated the Central Mountain Range (CMR) has presented a long-term and continuous barrier to gene flow since before the Last Glacial Maximum. In contrast, Murina gracilis and M. puta showed lower degrees of historical isolation and genetic differentiation associated with the CMR, reflecting greater gene flow, possibly coupled with past population growth in M. puta. Together our results highlight the usefulness of combining distribution models with phylogeographic analyses to understand the drivers of genetic structure.
With 3 plates and 2 figures in the text)We define the species boundaries of white-toothed shrews (genus Crocidura) in Taiwan using karyological and morphological characteristics. Ninety-nine animals were obtained from all over Taiwan at capture rates usually less than 10%. Three species are recognized by distinct cytotypes:Crociduru uttenuata tanakae 2n = 40, FN = 56; Crocidura suaveolens hoslefti 2n = 40, FN = 50; Crocidura kurodai 2n = 40, FN = 54. A suite of six morphological characters diagnose the three species: shape of skull, position of incisive foramina, shape of fourth upper premolar, shape of pinna, tail vibrissae, and foot pads. A species key and notes on the life history of each species are provided. Finally, we discuss chromosomal evolution and biogeography of Crociduru in East and South East Asia.
Crocidura tadae was ®rst reported as a new species from Orchid Island by Tokuda & Kano (1936). However, both C. tadae and C. kurodai from Taiwan were considered as subspecies of C. hors®eldii by subsequent researchers. In the present study, the karyotypic and morphological differences among the potential C. tadae specimens from Taiwan main island and two offshore islands (Orchid Island and Green Island) were examined. The results revealed that there is no signi®cant difference in the karyotypes of these shrews but that their karyotype is different from that of other Crocidura species. Therefore, the Tadae's shrew C. tadae Tokuda & Kano, 1936 should be a valid species. Furthermore, morphological variation in 25 external and cranial characters of 106 specimens were analysed using univariate statistics, and eight selected characters were used for multivariate analyses. Univariate statistical comparisons of the three insular samples revealed that shrews of the Green Island population were the largest in most measurements of characters and shrews of the Orchid Island population were the smallest. Multivariate analysis differentiated the Taiwan samples from the other two insular samples. Therefore, three subspecies of C. tadae are recognized: C. t. tadae (Orchid Island); C. t. kurodai (Taiwan) and C. t. lutaoensis subsp. nov (Green Island).
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