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| Figure 1: Sampling localities (A) and Maximum likelihood (ML) tree obtained based on mtDNA data of Tylototriton s.l. and relatives (B). Sample number 1–108 refer to Table S1. Five clades (I, II, III, IV and V) of the genus were denoted as different colors. Bootstrap supports (bs) resulted from ML analyses and posterior probability (pp) resulted from Bayesian inference (BI) method were labeled on major nodes. Node supports ML1 and BI1 were resulted from analyses on mtDNA data, while ML2 and BI2 were from analyses on four-gene concatenated data. Black: bs > 70% or pp > 0.95, grey: bs = 50–70% or pp = 0.85–0.95, white: bs < 50% and pp < 0.85.
in Wang, Nishikawa, Matsui, et al., 2018.
DOI: 10.7717/peerj.4384
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Abstract
Global climatic transitions and Tibetan Plateau uplifts are hypothesized to have profoundly impacted biodiversity in southeastern Asia. To further test the hypotheses related to the impacts of these incidents, we investigated the diversification patterns of the newt genus Tylototriton sensu lato, distributed across the mountain ranges of southeastern Asia. Gene-tree and species-tree analyses of two mitochondrial genes and two nuclear genes revealed five major clades in the genus, and suggested several cryptic species. Dating estimates suggested that the genus originated in the early-to-middle Miocene. Under different species delimitating scenarios, diversification analyses with birth-death likelihood tests indicated that the genus held a higher diversification rate in the late Miocene-to-Pliocene era than that in the Pleistocene. Ancestral area reconstructions indicated that the genus originated from the northern Indochina Peninsula. Accordingly, we hypothesized that the Miocene Climatic Transition triggered the diversification of the genus, and the reinforcement of East Asian monsoons associated with the stepwise uplifts of the Tibetan Plateau promoted the radiation of the genus in southeastern Asia during the Miocene-to-Pliocene period. Quaternary glacial cycles likely had limited effects on speciation events in the genus, but mainly had contributions on their intraspecific differentiations.
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| Figure 1: Sampling localities (A) and Maximum likelihood (ML) tree obtained based on mtDNA data of Tylototriton s.l. and relatives (B). Sample number 1–108 refer to Table S1. Five clades (I, II, III, IV and V) of the genus were denoted as different colors. Bootstrap supports (bs) resulted from ML analyses and posterior probability (pp) resulted from Bayesian inference (BI) method were labeled on major nodes. Node supports ML1 and BI1 were resulted from analyses on mtDNA data, while ML2 and BI2 were from analyses on four-gene concatenated data. Black: bs > 70% or pp > 0.95, grey: bs = 50–70% or pp = 0.85–0.95, white: bs < 50% and pp < 0.85.
in Wang, Nishikawa, Matsui, et al., 2018.
DOI: 10.7717/peerj.4384
|
Conclusions:
Our findings provided evidence for the profound influences of historical climate shifts especially associated with the uplift of the Tibetan Plateau on the diversification of animals occurring in the southeastern Asia. The results basically confirmed the reports on plant lineages, such as Rheum (Sun et al., 2012), Lepisorus (Wang et al., 2012a; Wang et al., 2012b), Juniperus (Mao et al., 2010) and Isodon (Yu et al., 2014), and on animal groups, such as Chiastocheta Pokorny, 1889 (Anthomyiidae, Diptera, Insecta; Espíndola, Buerki & Alvarez, 2012) and spiny frogs (Dicroglossidae, Anura, Amphibia; Che et al., 2010). Yet the present study further supplied some other indications. Primarily, although diversification of the newt group was promoted by the climatic shifts, several factors, for example, niche limits and their intrinsic low dispersal capacity, might have contributed to their Pleistocene rate-slowdown diversification. In addition, this study provided a putative “complete” species tree for Tylototriton s.l. to date. The inclusion of many putative cryptic species in the diversification analyses seems to be effective in finding diversification models of the group. But at present, wild populations of Tylototriton s.l. show a significant decline due to many reasons, such as climate changes, human capture and habitat deterioration. Further deep investigations of undetected cryptic lineages might supply the basic requirement for disclosing “true” diversification history of the taxa.
Bin Wang, Kanto Nishikawa, Masafumi Matsui, Truong Quang Nguyen, Feng Xie, Cheng Li, Janak Raj Khatiwada, Baowei Zhang, Dajie Gong, Yunming Mo, Gang Wei, Xiaohong Chen, Youhui Shen, Daode Yang, Rongchuan Xiong and Jianping Jiang. 2018. Phylogenetic Surveys on the Newt Genus Tylototriton sensu lato (Salamandridae, Caudata) reveal Cryptic Diversity and Novel Diversification Promoted by Historical Climatic Shifts. PeerJ. 6:e4384. DOI: 10.7717/peerj.4384