New pan-Indian study of elephant genetics reveals surprises

Herd of elephants in Terai Arc Landscape

Asian elephants were once widely distributed in India, but are now restricted to four widely separated regions: the north-western (NW), north-eastern (NE), east-central (ECI), and the southern India (SI). When you undertake the population genetics study of a wildlife species, the quality of the result is related to the design of the field sampling protocol. This is to ensure that the sampling is extensive covering different areas to avoid over-sampling of more accessible populations. When we started our population genetics study of the Asian elephant (Elephas maximus L.), we planned to collect fresh elephant dung samples from across the beats and various ranges of protected forests in India. This of course often involved traversing through inhospitable and difficult terrain with a forest staff in attendance. The first problem were the elephants themselves. To get fresh dung, one had to go close to elephants for collecting samples. This often did not go down too well with some individuals who responded to the invasion by a determined charge. We were fortunate not to have suffered any mishaps and ultimately it worked out well and we were able to collate an impressive database of elephant dung samples.


Habitat loss and fragmentation afflicts elephant habitats which can result in loss of genetic variation and reduction in gene flow that could impact their fitness and survival over the long term. Assessing genetic diversity and on-going gene flow between and within these sub-populations can provide insights into how these populations can be conserved. Rahul De, the first author carried out the DNA analyses using 14 microsatellite markers to genetically characterise 169 faecal samples collected by the various co-authors. With the guidance and technical help of Dr. S. P. Goyal, his supervisor and Dr. Reeta Sharma he identified three distinct genetic clusters: the NW, NE and the ECI-SI. This last cluster suggests that these now disjunct elephant populations of the southern and Eastern-Central ranges were once contiguous. However, within each cluster there was significant genetic structuring at finer scales which could be attributed mostly to recent anthropogenic land use changes. Also, elephants being highly intelligent with complex sociality, could prefer mating with populations that are further apart, than close by, thereby creating genetic differentiation at local scales, as we had found in certain cases.

Another lone male

Our study shows that the main concerns are the ongoing genetic differentiation indicating increasing population discontinuity, and the moderate levels of genetic diversity. This shows that although India supports around 60% of the global population of Asian elephants, the risk of further fragmentation and loss of habitat, and the impact of climate change, could affect the long-term viability of elephants in India. Therefore, management interventions to maintain intact and connected habitats to enable population growth and movement could help ameliorate these effects.

Mother-calf pair at Dooars (Northern West-Bengal)

References:
De R, Sharma R, Davidar P, Arumugam N, Sedhupathy A, Puyravaud JP, Parida J, Digal DK, Kanagaraj R, Kakati K, Nigam P, Williams AC, Habib B, Goyal SP. (2021) Pan-India population genetics signifies the importance of habitat connectivity for wild Asian elephant conservation. Global Ecology and Conservation, vol. 32. Doi: 10.1016/j.gecco.2021. e01888.

Mongabay article Corridors with high human activity may not ease elephant connectivity: study

Kanagaraj R, Araujo MB, Barman R, Davidar P, De R, Digal DK, Gopi GV, Johnsingh AJ, Kakati K, Kramer‐Schadt S, Lamichhane BR. (2019) Predicting range shifts of Asian elephants under global change. Diversity and Distributions. ;25(5):822-38.

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