Human-mediated introduction of introgressed deer across Wallace's line: Historical biogeography of Rusa unicolor and R. timorensis.

Renata F Martins,Andreas Wilting,Dorina Lenz,Joerns Fickel,Anke Schmidt

doi:10.1002/ece3.3754

Renata F Martins, Andreas Wilting + Show 3 more

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https://doi.org/10.1002/ece3.3754

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Abstract

In this study we compared the phylogeographic patterns of two Rusa species, Rusa unicolor and Rusa timorensis, in order to understand what drove and maintained differentiation between these two geographically and genetically close species and investigated the route of introduction of individuals to the islands outside of the Sunda Shelf. We analyzed full mitogenomes from 56 archival samples from the distribution areas of the two species and 18 microsatellite loci in a subset of 16 individuals to generate the phylogeographic patterns of both species. Bayesian inference with fossil calibration was used to estimate the age of each species and major divergence events. Our results indicated that the split between the two species took place during the Pleistocene, ~1.8 Mya, possibly driven by adaptations of R. timorensis to the drier climate found on Java compared to the other islands of Sundaland. Although both markers identified two well‐differentiated clades, there was a largely discrepant pattern between mitochondrial and nuclear markers. While nDNA separated the individuals into the two species, largely in agreement with their museum label, mtDNA revealed that all R. timorensis sampled to the east of the Sunda shelf carried haplotypes from R. unicolor and one Rusa unicolor from South Sumatra carried a R. timorensis haplotype. Our results show that hybridization occurred between these two sister species in Sundaland during the Late Pleistocene and resulted in human‐mediated introduction of hybrid descendants in all islands outside Sundaland.

Highlights

Introduction of Javan deer toTimor seems to have occurred only once and, presumably, with very few founders because of the lack of mtDNA diversity found among all individuals
We sampled 110 individuals labeled as Rusa unicolor (RUN) and Rusa timorensis (RTI) from European museums, aged between 180 and 61 years old
More intensive and extensive sampling of R. timorensis on their native range is necessary to discern whether pure RTI populations still remain in Java and Bali or whether they are composed in their majority by hybrid individuals

Summary

| MATERIALS AND METHODS

We sampled 110 individuals labeled as Rusa unicolor (RUN) and Rusa timorensis (RTI) from European museums, aged between 180 and 61 years old. We estimated genetic differentiation through FST as implemented in ARLEQUIN v.3.5.12 (Excoffier, Laval, & Schneider, 2005) For this analysis, we created two datasets: (1) two populations corresponding to species as determined by the museum identification and (2) populations corresponding to major haplotype clades. The smaller clade comprised six individuals from Java, Bali, Moluccas, and South Sumatra (Figure 2) of which four had been labeled in the museum collections as R. timorensis (Javan deer, RTI) and two as R. unicolor (sambar, RUN; RUN41: South Sumatra; RUN37: Moluccas, see above). The second major clade comprised all other samples, including samples labeled as RTI from Java and from the introduction range of Javan deer (Lesser Sunda Islands, Sulawesi, and the Moluccas) Both ML and BI tree topologies were concordant with the overall pattern recovered by the haplotypic network, revealing the existence of two well-differentiated clades (Figure 3). Population differentiation (FST) was always significant between the two species, independent of the grouping method (museum assignments or STRUCTURE analyses, Table 2)

Findings

| DISCUSSION

| CONCLUSION