Landscape and demographic history shape current leopard cat
population structure in Taiwan
Our analysis of colonization history revealed a divergence between the
Northern and Southern populations 800 years ago, followed by a secondary
contact 200 years ago. We infer that this secondary contact generated
the diversity hotspot and the pattern of admixture observed in the
Central population. Although the exact cause of this secondary contact
remains unclear, historical climate fluctuations and human activities
are likely contributing factors. Similar demographic changes in other
mammals have been attributed to climate variations and human
disturbances (Ding et al., 2011; Haffer, 1969; Lavretsky et al., 2020;
Perry et al., 2001). We also found evidence of bottleneck events in the
past 200 years, coinciding with rapid human development in Central
Taiwan (Barclay, 2015; Wu, 2004). Habitat loss, deforestation, and
changes in land cover to residential or commercial use have negatively
impacted several species in Taiwan, including leopard cats (Chang et
al., 2012; Hwang et al., 2010; Karczmarski et al., 2017). Consequently,
the distribution of leopard cats has significantly declined, with their
occurrence now limited to central Taiwan (Chen, 1956; Horikawa, 1931).
Our genetic analyses support the notion that intense anthropogenic
impacts have contributed to the reduction in effective population sizes
of the island’s leopard cats.
In landscape genetic studies, it is challenging to interpret how
contemporary landscapes and historical demographic processes influence
genetic structure and gene flow due to the time lag problem (Bolliger,
Lander, & Balkenhol, 2014; Epps & Keyghobadi, 2015). Various molecular
markers and approaches have been used to assess the effects of
contemporary landscapes and historical events on genetic structures at
different timescales (Epps & Keyghobadi, 2015), with one such approach
being to combine genetic markers displaying different mutation rates
(Pérez-Espona, McLeod, & Franks, 2012). Although our mtDNA data could
not provide insights into historical events, we were able to apply a
variety of statistical techniques on the nuclear loci, combining
landscape genetic analyses and coalescent methods (Epps & Keyghobadi,
2015). By doing so, we revealed associations between current landscape
features and population structures, with historical evolutionary events
also contributing to the genetic profile of leopard cats. Nevertheless,
quantifying and distinguishing the relative importance of historical and
contemporary factors in shaping genetic structure is difficult,
especially when multiple potential explanations are correlated or
non-exclusive (Shirk, Landguth, & Cushman, 2018). However, the high
mutation rates of microsatellite markers can still effectively reflect
barriers or fragmentation caused by current landscapes or anthropogenic
constructions, particularly when the focal species has a short
generation time and the barriers have existed for a long time (Epps &
Keyghobadi, 2015; Shirk, Landguth, & Cushman, 2018; Wang, 2011).