Fine‐scale demographic processes resulting from multiple overseas colonization events of the Japanese stream tree frog, Buergeria japonica

Abstract

Aim Amphibians are considered poor transoceanic dispersers because of their permeable skin. However, overseas dispersal of amphibian species has been revealed by recent phylogeographical studies and the role of overseas colonization of amphibians on their evolution and diversification has also been highlighted. However, no studies have investigated in detail the demographic processes related to these overseas colonization events. To clarify how amphibians achieve overseas colonization, we estimated the demographic history of the Japanese stream tree frog, Buergeria japonica, which is distributed on Amami Island and four northern neighbouring islands of the Tokara Archipelago, Japan. Location South‐western islands of Japan and Taiwan. Methods We analysed the mitochondrial cytb gene and 20 microsatellite loci, and constructed phylogenetic trees based on these data. We also performed demographic analyses by applying approximate Bayesian computation (ABC) method and an isolation‐with‐migration model. Results Phylogenetic and demographic analyses based on cytb and 20 microsatellite genotype data revealed that divergence among island populations took place recently, mostly within the last few thousand years. Populations from the northern islands had reduced genetic diversity compared with southern islands, and ABC analyses supported the hypothesis that the species colonized islands from south to north. Main conclusions Given that the islands are separated from each other by deep sea, the recent divergences observed indicate overseas colonization events among the five islands. ABC analyses support the hypothesis that B. japonica underwent a stepping‐stone overseas colonization from southern to northern neighbouring islands during the past few thousand years accompanied by multiple founder effects. These results support the hypothesis that overseas colonization could have had a substantial impact on amphibian evolution and diversification.

Geographical and temporal origins of terrestrial vertebrates endemic to Taiwan

“…Despite the lack of empirical evidence, several Taiwanese reptiles have been posited to colonize from the Malay Archipelago by oversea dispersal (Hsiang et al, 2009). Evidence from the Taiwan-Ryukyu Islands (Komaki et al, 2017;Yang et al, 2018) and the Taiwan-Luzon Islands (Esselstyn & Oliveros, 2010) has also supported oversea dispersal as a potential mechanism for the geographical origin of insular vertebrates. Accordingly, we suggest that prior to the emergence of the Pleistocene land bridge; Taiwan might have provided virgin habitat such as newly formed oceanic islands for the pioneers derived from the mainland via oversea dispersal.…”

“…Brown et al, 2013;Crottini et al, 2012;de Bruyn et al, 2014;Stelbrink, Albrecht, Hall, & von Rintelen, 2012). Nevertheless, studies on East Asian islands are comparatively limited, and due to the distinct geological contexts, the biogeographical patterns on East Asian islands are rather distinct (Li, Fu, & Lei, 2011;Komaki et al, 2017;Su, Brown, Chang, Lin, & Tso, 2016;Yang, Komaki, Brown, & Lin, 2018).…”

Parallel evolution of an alpine type ecomorph in a scorpionfly: Independent adaptation to high‐altitude environments in multiple mountain locations

“…The identification of factors leading to speciation and elucidation of the associated mechanisms generating biodiversity are considered to be important tasks by evolutionary biologists (Schluter & Pennell, ). Previous studies targeting various taxa demonstrated that the origins of genetic diversity, evolution and speciation are the results of complex interactions among geographical history, random genetic drift, the environment, biological factors, and stochastic processes (Hoskin, Higgie, Mcdonald, & Moritz, ; Kano, Nishida, & Nakajima, ; Komaki et al, ; Saito & Tojo, ; Schoville, Uchifune, & Machida, ; Su, Wang, & Villanueva, ; Suzuki, Kitano, & Tojo, ). In particular, the fragmentation of populations is one of the major factors driving diversification and speciation often as the result of (a) climate changes within habitats and (b) changes in the environmental conditions between habitats thereby promoting divergent adaptation (Cole et al, ; Jensen et al, ; Schoville & Roderick, ; Shi, Ji, Liu, Wang, & Zhang, ; Stewart, Lister, Barnes, & Dalén, ; Tojo et al, ).…”

Transoceanic Disperse of the White-lipped Island Pit Viper (Cryptelytrops insularis; Kramer,1997) from Sundaland to Lesser Sunda, Indonesia

“…Komaki et al suggested that there are two possibilities for terrestrial animal transoceanic dispersal, ocean flow or carry by other animals with high dispersal ability (birds or human) [41]. However, at that time (around 4 mya) humans did not exist yet [42].…”

“…Zoologists explained that insects, mammals, and reptiles have been demonstrated the transoceanic dispersal by rafting [43][44][45]. Some floating stuff such as macroalgae, pumice, wood, and vegetation could be a substrate for the snake to hold up [41,46]. The ocean drift usually following the ocean throughflow and winds [46].…”