Demographic and genetic structure of a severely fragmented population of the endangered hog deer (Axis porcinus) in the Indo-Burma biodiversity hotspot

The overall population structure indicated a higher number of females compared with males, juveniles and fawns, which may contribute in limiting the population size. High propor- tion of females in the population can also be attributed to several natural and anthropogenic factors. With the declining thickness of phumdis, the floating vegetation can barely support the weight of adult male hog deer, subsequently affecting the survival rate of male individuals. The antlers of the males occasionally get entangled in the thick vegetation that dominates the habi- tat, resulting in high male mortality. In addition, traditional hunting practiced by the local communities using snares occasionally entraps the antlers, contributing to increased male mortality. Targeted poaching of male individuals for the aesthetic value of their antlers and trophies may also be a reason for the low male counts. Instances of male mortality due to these factors were recorded at times during the study period. The reduced numbers of fawns to female ratio in the park can be attributed to predation by dogs and wild boar, which has been observed during the course of the study and also from other reports (e.g. [55]). The present study suggest an initial declining trend in the population in the park and subsequent increase from 2013–2018, which may be a consequence of active conservation measures. The consequences of habitat fragmentation on the genetic structure and variability are still not well-studied [56]. However, several studies have pointed out that fragmented and isolated

population such as the hog deer in KLNP may be susceptible to the increase in population dif- ferentiation caused by loss of heterozygosity, genetic drift and inbreeding depression [9, 10, 57, 58]. Long term survival of a species with small and declining population is not only limited by genetic diversity but is also vulnerable to natural catastrophes and demographic and envi- ronmental stochasticity [59]. With respect to the hog deer population in KLNP, the loss of genetic diversity may not have acute effect on short term population growth, however it may restrict the evolutionary potential of the species by limiting the selection flexibility in the long run [60, 61]. High levels of genetic diversity in a population is also essential to adapt to the changing environment because it increases the probability of individuals in a population to retain varia- tions of alleles which in turn will enable the population to persist for more generations [62]. In our study, the He of the hog deer population was 0.51 ± 0.03, close to the mean He of 0.559 of sika deer in China but much higher than the mean He of the Sichuan sika deer (0.477). It was slightly lower than the mean He of Przewalski’s gazelle (Procapra przewalskii) (He = 0.552) [63], Manchurian sika deer (0.584) and South China sika deer (Jiangxi, 0.585; Zhejiang, 0.589) [64]. Compared with other ungulates, such as the red deer (Cervus elaphus) (He = 0.78 [65]; He = 0.804 [66]; He = 0.62–0.85 [67]), forest musk deer (Moschus berezovskii) (He = 0.8–0.9)

[68] and Mongolian wild ass (Equus hemionus hemionus) (He = 0.83) [69], the hog deer had a relatively low He value and was equivalent to the milu (Elaphurus davidianus) (He = 0.46– 0.54) [70]. In our study, the PIC values of eight of the 23 microsatellite loci were higher than 0.5, indicating high polymorphism. The heterozygosity and PIC indicated that the hog deer in KLNP had moderate levels of genetic diversity (Table 3). Hartl and Clark [71] considered that population deviations from the HWE are mainly due to small populations, non-random mating, gene mutation, migration or other factors. No devi- ation from the HWE was observed in the selected loci. In addition, due to the relatively closed geographical position of KLNP, i.e., the lack of connectivity with the surrounding areas, very few hog deer were distributed in its periphery [72]. This indicates that the moderate level of genetic variation in KLNP population compared to other hog deer populations in India [12] may be due to the geographical isolation of the population and lack of connectivity with the adjacent landscape. The gene pool is restricted, and little genetic exchange with other popula- tions is happening due to the unique island-like geography of the area, coupled with dense human habitation around the park. In the present study, the Ho values of selected markers Demographic and genetic structure of hog deer in the Indo-Burma biodiversity hotspot PLOS ONE | https://doi.org/10.1371/journal.pone.0210382 February 6, 2020 11 / 16