Conservation Implications
Anthropogenic GCC is one of the most significant threats to Earth’s biodiversity (Elsen & Tingley, 2015; Bellard et al., 2014). Tropical montane species are predicted to suffer the greatest effects because they are likely to be endemic with restricted geographic ranges and narrow climatic tolerance (Williams, Jackson, & Kutzbach, 2007; La Sorte & Jetz, 2010). Several studies have documented upslope range shifts in response to GCC-associated temperature and precipitation changes (e.g. Freeman, Scholer, Ruiz-Gutierrez, & Fitzparick, 2018; Raxworthy et al., 2008b; Chen et al., 2009). These shifts can result in reduced or fragmented habitat, decreasing genetic diversity and making species vulnerable to extinction (Moritz et al., 2008; Williams et al., 2007). In addition, in the case of locally adapted, highly structured populations, increased dispersal and gene flow upslope could introduce maladaptive genes (Weiss-Lehman & Shaw, 2019). It is therefore imperative to understand how tropical montane populations are structured in order to predict, monitor, and mitigate the effects of GCC.
Here, we provide a foundational estimate of population structure, genetic diversity, and historical gene flow for mountain treeshrews in KNP. These data can be used to monitor GCC-induced population genetic changes over time. Montane communities in KNP could experience an upslope shift of ca. 490 m by 2100 CE (Still, 1999; Camacho et al., 2018), assuming mild Intergovernmental Panel on Climate Change scenarios (IPCC 2013, www.ipcc.ch/report/ar5/wg1/). Although the factors that limit the mountain treeshrew at its lower elevational boundary are unknown, assuming that the species tracks the predicted 490 m upslope shift - whether because of climatic limitations or ecological interactions with lowland species expanding upslope - we predict that it will experience range contraction. The species already occupies the upper elevational limits within KNP, so an upslope shift in the lower bound of its distribution could not be countered with expansion at its upper limit. The lack of strong population structure across elevations means that upslope dispersal of lower elevation mountain treeshrews on MK will likely not increase extinction risk by introducing maladaptive genetic diversity. However, reduction in available habitat could make the species vulnerable.
We also predict that mountain treeshrews would maintain connectivity between MK and MT. However, the Crocker Range has few peaks above 1400 masl, and connectivity between KNP and the rest of the Crocker Range could be severed (Figure 7). This highlights the importance of KNP as a future refugium for montane species, as it contains the highest peak in the region and the greatest high-elevation forested area. Conservation efforts should focus on protecting forest habitat at 900 masl to facilitate gene flow and preserve genetic diversity.