Population genetics and evolutionary history of the endangered Eld’s deer (Rucervus eldii) with implications for planning species recovery

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.

Extrapolating the susceptibility of Eld’s deer (Rucervus eldii thamin) to chronic wasting disease from prion protein gene (PRNP) polymorphisms

“…The taxonomic classification of Eld's deer has been a subject of discussion (Pitra et al, 2004;Heckeberg, 2020;Ghazi et al, 2021;Wong et al, 2021). Some sources assign Eld's deer to the distinct genus Panolia following the nomenclature used by John Edward Gray in 1843 (Gray, 1843).…”

“…This designation is followed by the Species Survival Commission of the IUCN, as well as the AZA; thus, we use it here. However, some recent molecular studies have included Eld's deer in the genus Cervus (Balakrishnan et al, 2003;Angom et al, 2017;Ghazi et al, 2021). The deer examined by the current study were exclusively from the subspecies R. e. thamin.…”

Review: The status of the endangered Eld’s deer (Rucervus eldii) and conservation actions in Thailand

“…Eld's deer belongs to the order Artiodactyla, family Cervidae, subfamily Cervinae and tribe cervini. Eld's deer share morphological resemblances with swamp deer (R. duvaucelii) and the extinct Schomburgk's deer (R. schomburgki) (Ghazi et al 2021). The species is classified in the genus Rucervus, which is currently adopted by the International Union for Conservation of Nature (Gray et al 2015).…”

“…The species is classified in the genus Rucervus, which is currently adopted by the International Union for Conservation of Nature (Gray et al 2015). However, Ghazi (2021) has suggested that the three species classified under the genus Rucervus (R. duvaucelii, R. schomburgki and R. eldii) are extremely different and the classification of Eld's deer in Rucervus is phylogenetically inappropriate. Contrary to different perspectives based on morphological and karyotypic classification, molecular studies based on mitochondrial and nuclear markers suggest that the placement of Eld's deer along with several other species, including Elaphurus davidianus, Przewalski albirostris and all species of the genus Rusa, to the genus Cervus is phylogenetically more appropriate (Hu et al 2019).…”

“…groups from the main phylogenetic lineage of the tribe cervini, which later radiated in the genus Cervus, Rusa, Elaphurus and Eld's deer (Heckeberg et al 2022). Based on its ancestral divergence, Eld's deer is phylogenetically more closely related to the genus Cervus than to Rucervus, and the morphological similarities with R. duvaucelii and R. schomburgki characterize convergence rather than phylogenetic relatedness (Ghazi et al 2021).…”