Mountain treeshrews
Treeshrews are small-bodied mammals in the order Scandentia native to South and Southeast Asia. The most comprehensive subordinal molecular phylogeny of treeshrews to date showed that Borneo is a center of treeshrew diversity, with 9 of 20 extant species including both widespread and endemic lineages (Roberts, Lanier, Sargis, & Olson, 2011).
The mountain treeshrew is the only montane Tupaia species endemic to Borneo. Its distribution includes montane regions of Sabah and Sarawak (Figure 1 inset) (Payne and Phillipps 2016; Hawkins, 2019). The species diverged from its sister lineage, the ruddy treeshrew (T. splendidula ), ca. 4–7 Mya (Roberts et al., 2011). The ruddy treeshrew and other closely related species occupy lowland forest, potentially indicating elevational niche partitioning (Han, Sheldon, & Stuebing, 2000). On MK, the mountain treeshrew’s range spans from ca. 900 to 3200 masl, encompassing four vegetation zones following Kitayama (1992): lowland (<1200 masl), lower montane (1200–2350 masl), upper montane (2350–2800 masl), and subalpine (2800–3400 masl). On MT, the species spans from ca. 900 masl to the summit and three vegetation zones (Camacho-Sanchez et al., 2019; Phillipps & Phillipps, 2016). The ecology, behavior, and evolution of this species are poorly known. The most comprehensive ecological study to date was conducted by Emmons (2000), who tracked individuals for one month at Poring Hot Spring, MK (900 masl). Emmons (2000) suggests that the mountain treeshrew has small home ranges compared to other Tupaia species, at only 2.5 hectares. Despite the lack of ecological information, the mountain treeshrew’s broad elevational distribution permits hypothesis testing regarding the effects of environmental heterogeneity on population genetic structure.