Examining the interglacial high‐elevation refugia scenario in East Asian subtropical mountain systems with the frog species Leptobrachium liui

Abstract

The effects of Quaternary climatic oscillations on the distributions of organisms in different parts of the world are not equally well understood, limiting the ability to understand the determinants of biodiversity. Compared with the mountain regions in southern Europe and southwestern North America, such effects on high‐elevation species in the East Asian subtropical mountain systems located in southern and southeastern China have seldom been addressed. In this study, using Leptobrachium liui (Megophryidae), we made one of the earliest attempts to examine the interglacial high‐elevation refugia scenario in these Asian mountains. Based on our current understanding of the study system, we formulated a hypothesis that these frogs of western origin were distributed more widely and continuously during glacial phases, allowing eastward dispersal, and that they are currently isolated in interglacial refugia at higher elevations. Microsatellite data and mitochondrial and nuclear sequence data were obtained with extensive sampling followed by the synthesis of phylogeographic and population genetic analyses and modeling of the species distribution. The analyses revealed a sequential eastward divergence of microsatellite clusters and gene lineages accompanied by a decline in genetic diversity. Molecular dating estimates revealed divergence events in the Pleistocene, and a reduction in local populations was inferred to have occurred at a time comparable to the end of the last glacial. Strong genetic isolation by distance reflecting a more continuous historical distribution was detected. Furthermore, environmental niche models inferred a wide planar distribution during the last glacial maximum, providing further support for the hypothesis.

Dynamics behind disjunct distribution, hotspot-edge refugia, and discordant RADseq/mtDNA variability: insights from the Emei mustache toad

“…In the present distribution of L. boringii, the South region (Fig. 1) is most close to the distribution or proposed ancestral range of the close relatives of the species [15,56,62,[76][77][78]. It may be not far away from the ancestral range of the species and, as suggested by the high and unique genetic variation estimates (Fig.…”

“…Five major mitochondrial lineages that diverged at approximately 3.7 to 2.3 mya were detected, including four corresponding exclusively to regions South (sites 1 and 2), East (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14), or West (21)(22)(23)(24)(25)(26)(27)(28). In the other major lineage, haplotypes from the Middle region (sites [15][16][17][18][19][20] were nested within East clades, and sequential branching events from approximately 0.8 to 0.1 mya were inferred from East through Middle to West.…”

“…The 745-bp nad1 fragment consisted of partial tRNA-Leu (16 bp) and NADH dehydrogenase subunit 1 genes; the D-loop fragment of~1080-1350 bp in length contained regions of the cytochrome b gene (78 bp) and a control region with the tRNA-Thr, tRNA-Pro, and tRNA-Trp genes between them. For the nad1 fragment, the primers Leu-1 L and Leu-5 L from Zheng et al [62] and ND1-6H from Zheng et al [15] were used in PCR and Sanger sequencing (ABI 3730). Sequences of this fragment for 19 individuals were also obtained from these two previous studies.…”

“…The protein-coding gene block contained mainly the nad1 gene sequence. Because suitable fossil calibrations were not available, an evolutionary rate of 0.69 ± 0.3% divergence per million years per lineage commonly used for the anuran nad1 gene was used to calibrate the tree [15,[104][105][106]. This approach required the protein-coding gene block to be constrained as one partition in analysis.…”

“…Regional biogeographic studies have often identified different major processes that shape the patterns of intraspecific genetic variability, for example, evolutionary melting pots [9,10], historical climate stability [11][12][13], and reduction of diversity during dispersal [14,15]. In relatively well-studied areas, commonalities may emerge regarding the relationship between the patterns of the distributional history and genetic diversity.…”