Slender lorises are one of the two genera of extreme nocturnal primates that inhabit India [
1]. They belong to the family Lorisidae, which also includes slow lorises, pottos, and angwantibos. Slender lorises are confined to India and Sri Lanka, where they inhabit dry to moist and lowland to montane forests [
2]. Slender lorises are characterized by their small size, long limbs, vestigial tail, large eyes, and slow locomotion. They are adapted for arboreal life, using their opposable thumbs and toes to grasp branches and their binocular vision to judge distances. They feed mainly on insects but also consume fruits, flowers, gums, and other plant materials [
3,
4]. They have a variety of vocalizations that may help them avoid predators and communicate with conspecifics [
5]. Slender lorises are divided into two species: the grey slender loris (
Loris lydekkerianus) found in southern India and Sri Lanka and the red slender loris (
Loris tardigradus) found only in Sri Lanka [
6]. Both species show high phenotypic variation in fur color, body size, and cranial morphology, leading to the recognition of several subspecies, most of which are refuted by molecular studies [
7]. The Mysore slender loris (
Loris lydekkerianus ssp. lydekkerianus) and the Malabar slender loris (
Loris lydekkerianus ssp. malabaricus), which live in the dry and wet forests of the Eastern and Western Ghats, respectively, are the two subspecies that have been recognized thus far in southern India [
8]. There are several regions in their distribution where slender lorises face serious threats to their existence such as habitat loss due to deforestation and urbanization, electrocution on live wires, road accidents, pet trade, and illegal poaching for traditional medicine and black magic [
9]. The IUCN Red List of Threatened Species classifies the Mysore Slender Loris [
10] and Malabar Slender Loris [
11] as "Near Threatened" and they are listed under Schedule I of the Indian Wild Life (Protection) Act, 1972. Recently, Tamil Nadu became the first Indian state to notify a sanctuary for slender lorises spanning 11,806 hectares which is crucial for protecting their habitat and ensuring the survival of this unique primate species.
The Mysore and Malabar subspecies of slender loris were delineated based on their geographic distribution and morphological differences [
6,
8]. The Mysore slender loris has a reddish-brown coat, a prominent white stripe on its forehead, compared to the Malabar slender loris, which has a greyish-brown coat, a less distinct forehead stripe [
6,
12]. The relative distribution of the two subspecies as well as their comparative densities and the extent of overlap between their distributions have been very well established [
8]. The Mysore slender loris is found in the Eastern Ghats and eastern foothills of the southern Western Ghats, while the Malabar slender loris is confined to the western slope of the entire Western Ghats [
8]. The Mysore slender loris prefers dry deciduous forests with moderate canopy cover and high tree density, while the Malabar slender loris prefers moist evergreen forests with high canopy cover and low tree density [
8]. Their distributions overlap along the southern ridges of the Western Ghats, where hybridization may occur. The Mysore slender loris is relatively larger (ca. 260 g) than Malabar slender loris (ca. 180 g) [
12]. The diet and feeding behavior of these subspecies varies depending on their habitat types and availability of food resources [
4]. The reproductive biology and social system of the Mysore subspecies is influenced by factors such as seasonality, food availability, predation risk, and population density. They also have a seasonal breeding cycle that coincides with periods of high food availability [
13]. But no such information on the reproductive biology of the Malabar subspecies is available. Behavioral studies on lorises have always been more challenging than on relatively large, diurnal, and group-living primates such as macaques and langurs because they are nocturnal, small in size, and mostly semi-gregarious. Considering these two subspecies geographically occupy two distinct landscapes and habitat conditions, and further very distinct in morphology and body size, understanding their evolutionary history and genetic difference becomes vital to address their conservation status and management issues.
Therefore, the main objective of this study is to investigate the phylogenetic relationship and genetic divergence between the Mysore and Malabar subspecies of slender loris in southern India. To achieve this, we sequenced and assembled the whole mitochondrial sequences from three representative samples. We aligned these sequences with the publicly available sequences of other lorises and constructed phylogenetic trees. We estimated the sequence divergence and divergence time between the two subspecies and found that the phylogenetic analysis supports the morphological and geographical delineation of the Malabar and Mysore slender lorises. The results of this study will contribute to the understanding of the biogeography and speciation processes of these threatened lorises and provide crucial insights for their conservation management.