Abstract
Eld's deer (Rucervus eldii) with three recognised subspecies (R. e. eldii, R. e. thamin, and R. e. siamensis) represents one of the most threatened cervids found in Southeast Asia. The species has experienced considerable range contractions and local extinctions owing to habitat loss and fragmentation, hunting, and illegal trade across its distribution range over the last century. Understanding the patterns of genetic variation is crucial for planning effective conservation strategies. This study investigated the phylogeography, divergence events and systematics of Eld's deer subspecies using the largest mtDNA dataset compiled to date. We also analysed the genetic structure and demographic history of R. e. eldii using 19 microsatellite markers. Our results showed that R. e. siamensis exhibits two divergent mtDNA lineages (mainland and Hainan Island), which diverged around 0.2 Mya (95% HPD 0.1–0.2), possibly driven by the fluctuating sea levels of the Early Holocene period. The divergence between R. e. eldii and R. e. siamensis occurred around 0.4 Mya (95% HPD 0.3–0.5), potentially associated with the adaptations to warm and humid climate with open grassland vegetation that predominated the region. Furthermore, R. e. eldii exhibits low levels of genetic diversity and small contemporary effective population size (median = 7, 4.7–10.8 at 95% CI) with widespread historical genetic bottlenecks which accentuates its vulnerability to inbreeding and extinction. Based on the observed significant evolutionary and systematic distance between Eld’s deer and other species of the genus Rucervus, we propose to classify Eld's deer (Cervus eldii) in the genus Cervus, which is in congruent with previous phylogenetic studies. This study provides important conservation implications required to direct the ongoing population recovery programs and planning future conservation strategies.
Highlights
Small populations are susceptible to loss of genetic diversity as a consequence of founder events, genetic bottlenecks, and inbreeding, accelerated by the cumulative impacts of natural and anthropogenic factors[1]
All the identified haplotypes in R. e. siamensis were unique to their respective populations with one haplotype (H2) observed in the Hainan Island, two haplotypes (H3 and H5) in Dusit Zoo, Thailand, and one haplotype (H4) in Paris Zoo, France
Demographic, environmental, and genetic factors profoundly affect the viability of p opulations[33]
Summary
Small populations are susceptible to loss of genetic diversity as a consequence of founder events, genetic bottlenecks, and inbreeding, accelerated by the cumulative impacts of natural and anthropogenic factors[1]. Thamin has witnessed severe range contractions and is considered extinct from Thailand This subspecies represents the largest population of Eld’s deer in the wild with localised populations in Myanmar and introduced populations in Thailand[7,15]. Evidence of faunal compressions and local extinctions due to the increased sea levels has been reported in the Isthmus of Kra region, which divides the Indochinese and Sundaic sub-regions[18,19] These changes together with dynamic climatological and vegetational conditions facilitated the diversification of many ruminant species[20,21,22,23] and would have influenced the patterns of genetic diversity, divergence and evolutionary history of Eld’s deer subspecies. All three species are currently classified together in the genus
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