Cryptic phylogeographic history sheds light on the generation of species diversity in sky‐island mountains

Abstract

Aim The aim of this study was to conduct comprehensive phylogeographic and demographic analyses to examine the degree to which topographic and climatic conditions have affected the patterns of diversification and migration in a strictly montane inhabitant, the montane long‐tailed mole (Scaptonyx fusicaudus). Location The mountains of south‐western China and adjacent mountains including Mts. Bashan, Dalou and Qinling also known as the sky islands in south‐western China. Taxon The long‐tailed mole (S. fusicaudus), a semi‐fossorial mammal distributed in the sky islands of south‐western China, is a relict species and the sole representative of the tribe Scaptonychini. Methods We sequenced one mitochondrial and six nuclear genes from 113 samples across the species’ range. We estimated phylogenetic relationships and divergence times, conducted genetic structuring and species delimitation using multiple approaches and used Approximate Bayesian Computation to test potential gene flow. We conducted ecological niche modelling to predict the species’ potential distribution in the present, the last glacial maximum and the last interglacial (LIG). Results The species comprises a minimum of 17 operational taxonomic units which are isolated in different mountain ranges. The lowlands and large rivers act as barriers to dispersal, and have isolated evolutionary lineages for up to 11 million years. Long‐distance dispersal is evident among a few discrete montane archipelagos. Suitable climatic conditions during the LIG are limited to only a few sites, thus geographically restricting climatic stable areas across geological periods (from the LIG to the present). Main conclusions For low‐vagility species, the complex topography of the sky islands has promoted exceptional diversification through a combination of eco‐environmental stability as well as geographic fragmentation. The mountains have acted as a buffer against climate change, and have provided continuously suitable habitats for S. fusicaudus since the early Late Miocene, supporting the hypothesis that the sky islands constitute “museums” of ancient lineages. Lowlands and river valleys have acted as barriers preventing gene flow, while the montane archipelagos could have provided stepping stones to facilitate dispersal.

Climatic Refugia and Geographical Isolation Contribute to the Speciation and Genetic Divergence in Himalayan-Hengduan Tree Peonies (Paeonia delavayi and Paeonia ludlowii)

“…However, when the divergence pace of lineage and niche exhibits consistency, ecological niche divergence may also have contributed to speciation, regardless of the geographical mode of speciation (Hua and Wiens, 2013 ). During the last decades, genetic effects of vicariant events induced by topographical change are well-documented in phylogeographic studies, highlighting the existence of cryptic diversity in many species such as yews, oaks, moles, and white pine distributed in HHM (Liu et al, 2013 , 2019 ; Du et al, 2017 ; He et al, 2019 ). However, comparatively little is known about the potential role of ecological factors in the process of species or lineage diversification, and ecology-driven genetic divergence has seldom been examined (Meng et al, 2015 ; Zhao et al, 2016 ; Gao et al, 2019 ).…”

Ring distribution patterns—diversification or speciation? Comparative phylogeography of two small mammals in the mountains surrounding the Sichuan Basin

“…The great difference in elevation leads to landscape heterogeneity between the basin and the surrounding mountains, resulting in a "soft" barrier for the dispersal of some species, especially for the montane species He et al, 2019). The barrier effect of the Sichuan Basin was also inferred through developing a generalized model and using the known examples to evaluate the potential geographical barriers (Monahan et al, 2012).…”

“…These mountains (except for the Eastern Himalaya Mountains and the southern part of the Hengduan Mountains) form an approximate ring surrounding the Sichuan Basin, which is mainly a lowland plain with an elevational range of 250–750 m (Liu et al, 2012). The great difference in elevation leads to landscape heterogeneity between the basin and the surrounding mountains, resulting in a “soft” barrier for the dispersal of some species, especially for the montane species (Bennett & Provan, 2008; He et al, 2019). The barrier effect of the Sichuan Basin was also inferred through developing a generalized model and using the known examples to evaluate the potential geographical barriers (Monahan et al, 2012).…”

Local-scale dispersal constraints promote spatial structure and arthropod diversity within a tropical sky-island

“…Second, coupling altitudinal gradients with tropical latitudes allows populations within tropical mountains to persist relatively in situ despite global climate fluctuations (Mastretta-Yanes, et al, 2018;Rahbek, et al, 2019a;Rahbek, et al, 2019b). These processes of isolation and long-term persistence have been widely used to explain diversification among tropical mountain peaks across the world (e.g., Fjeldså et al, 2012;He et al, 2019;Knowles, 2001;Mastretta-Yanes et al, 2018;McCormack et al, 2009;Uscanga et al in review ). However, recent evidence suggests that neutral processes within a single mountain could also play an important role in generating endemism (Bray & Bocak, 2016), but diversification at the single mountain scale and short geographic distances has seldom been explored.…”