High gene flow across heterogeneous tropical montane environments in a
Bornean endemic small mammal
Abstract
Rapid shifts in environmental variables associated with elevational
changes in montane ecosystems provide opportunities to test hypotheses
regarding the effects of environmental heterogeneity on gene flow and
genetic structure. In tropical mountains, spatial environmental
heterogeneity combined with seasonal environmental stability is
predicted to result in low dispersal across elevations. Few studies have
investigated the genetic consequences of elevational environmental
heterogeneity in tropical montane mammals. Here, we use a population
genomics approach to test the hypothesis that mountain treeshrews
(Tupaia montana) exhibit limited gene flow across elevational
gradients and between two neighboring peaks within Kinabalu National
Park (KNP) in Borneo. We sampled 83 individuals across elevations on Mt.
Tambuyukon (MT) and Mt. Kinabalu (MK) and sequenced mitogenomes and
4,106 ultraconserved elements containing an average of 1.9 single
nucleotide polymorphisms per locus. We detected high gene flow across
elevations and between peaks. We found greater genetic differentiation
on MT than MK despite its lower elevation and associated environmental
variation. This implies that, contrary to our hypothesis, genetic
structure in this system is not primarily shaped by elevation. We
propose that this pattern may instead be the result of colonization
history combined with restricted upslope gene flow on MT due to unique
plant communities associated with its upper montane habitats. Our
results serve as a foundation to identify and mitigate future effects of
climate change on mountain treeshrews in KNP. Given predictions for 2100
CE, we predict that mountain treeshrews will maintain genetic
connectivity in KNP, making it an important conservation stronghold.