Messing about on the river: the role of geographic barriers in shaping the genetic structure of Bornean small mammals in a fragmented landscape

Abstract

Landscape features may restricting dispersal and gene flow, and increase demographic isolation among sub-populations. In addition, landscape features may represent potential dispersal barriers depending on species vagility. To predict the persistence of populations and to formulate adequate conservation measures it is essential to understand the ability of species to transverse landscape barriers. Using population genetic techniques we assessed the importance of physical barriers along the Kinabatangan River for a suite of non-volant small mammals. Cytochrome b sequence variation was examined for each of the 19 species sampled across both riverbanks. Haplotype networks and molecular variance analyses indicated contrasting patterns of genetic isolation between riversides for different taxa. Genetic isolation between riversides ranged from moderate to complete in tree shrews and squirrels, whereas no isolating effect could be detected in murids and gymnures. Although genetic divergence between forest fragments on the same side of the river could only be studied in a subset of six species, the results suggest an additional dispersal barrier for two of these studied species. While barrier effects of a paved road and tributaries could not be verified, large oil palm plantations seem to have disrupted gene flow in these species. Furthermore, the findings suggest higher genetic connectivity on the more continuously forested compared to the more fragmented riverside, and underline the importance of forest corridors as essential conservation measures to maintain genetic diversity in a fragmented landscape such as that along the Kinabatangan River.

Dispersal and genetic structure in a tropical small mammal, the Bornean tree shrew (Tupaia longipes), in a fragmented landscape along the Kinabatangan River, Sabah, Malaysia

“…The present study corroborates some findings of Brunke et al [19] and confirms the river as an important barrier to gene flow in T. longipes. For example, when ignoring the river by pooling the northern and southern samples, a significant excess of homozygosity was visible in the whole dataset, most likely a result of the Wahlund effect [40].…”

“…Nowadays, oil palm plantations dominate the landscape along the river and forest is restricted to isolated patches. Despite this extensive land conversion in the Kinabatangan floodplain, a highly diverse small mammal community remains in the forest remnants along the Kinabatangan River [19]. Diverse responses to landscape features along the Kinabatangan River itself have recently been reported for a suite of small mammals in this anthropogenically modified region [19].…”

“…Despite this extensive land conversion in the Kinabatangan floodplain, a highly diverse small mammal community remains in the forest remnants along the Kinabatangan River [19]. Diverse responses to landscape features along the Kinabatangan River itself have recently been reported for a suite of small mammals in this anthropogenically modified region [19]. Dispersal and gene flow have been shown to be limited by the Kinabatangan River predominantly in squirrels and tree shrews.…”

“…The Bornean tree shrew (Tupaia longipes Thomas 1893, Scandentia, Tupaiidae) is endemic to Borneo, is widespread throughout the island and is known to inhabit fragmented forest patches such as those along the Kinabatangan River [19]. Although listed by the IUCN as Least Concern [24], T. longipes has a declining population trend throughout its range due to deforestation and habitat degradation, and is therefore listed in CITES Appendix II [25].…”

Predicting disease risk areas through co-production of spatial models: The example of Kyasanur Forest Disease in India’s forest landscapes

“…wildlife hosts for tick vectors and KFD, and in turn, to epidemic spread [47,48]. The LULC map is based on 30 m resolution Landsat data, thus only detects water-bodies of larger than 30m.…”