Cryptic diversity of limestone karst inhabiting land snails (Cyclophorus spp.) in northern Vietnam, their evolutionary history and the description of four new species.

Katharina C M Von Oheimb,Jonathan Ablett,Sang Van Pham,Hao Van Luong,Tu Van Do,Takahiro Hirano,Parm Viktor Von Oheimb,Fred Naggs

doi:10.1371/journal.pone.0222163

Katharina C M Von Oheimb, Jonathan Ablett + Show 6 more

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https://doi.org/10.1371/journal.pone.0222163

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Abstract

Limestone karsts can form terrestrial habitat islands for calcium-dependent organisms. In Vietnam, many karst habitats are threatened, while their rich biodiversity is still far from being thoroughly explored. Given that conservation of karst biota strongly relies on correct species identification, the presence of undetected cryptic species can pose severe problems. The present study focuses on cryptic diversity among karst-inhabiting land snails of the genus Cyclophorus in northern Vietnam, where specimens with a similar shell morphology have been reported from various regions. In order to examine the diversity and evolutionary history of this “widespread morphotype”, we generated a Bayesian phylogeny based on DNA sequence data. Automatic Barcode Gap Discovery (ABGD) and the Bayesian implementation of the Poisson tree processes model (bPTP) contributed to species delimitation and analyses of shell shape and size aided the morphological characterisation of individual species. We found that the examined specimens of the widespread morphotype did not form a single monophyletic group in the phylogeny but clustered into several different clades. We delimited nine different species that develop the widespread morphotype and described four of them as new. Processes of convergent evolution were probably involved in the origin of the delimited species, while their generally allopatric distribution could result from interspecific competition. Our findings indicate ongoing processes of speciation and a potential case of morphological character displacement. The high degree of morphological overlap found among the species underlines the importance of DNA sequence data for species delimitation and description in the genus Cyclophorus. Given the findings of the present study and the high potential that as yet undiscovered cryptic taxa have also evolved in other groups of karst-inhabiting organisms, we argue for a systematic and efficient detection and description of Vietnam’s karst biodiversity to provide a solid basis for future conservation planning.

Highlights

Tropical and subtropical limestone karsts, such as those in Southeast Asia, can form terrestrial habitat islands for plant and animal taxa that depend on a calcium-rich environment
The Bayesian phylogeny (Fig 1) revealed five major clades of Cyclophorus spp. (A–E; named following [6]). These clades were supported with Bayesian posterior probabilities (BPP) of 1.00, except of major clade E, which comprised only a single haplotype
The third one, was regarded as a clade that develops the widespread morphotype because shells of assumed conspecifics of the sequenced specimen with this morphology were found at the same sampling locality

Summary

Introduction

Tropical and subtropical limestone karsts, such as those in Southeast Asia, can form terrestrial habitat islands for plant and animal taxa that depend on a calcium-rich environment. Such limestone-associated organisms can occur in high abundances on karsts, while the often acidic soil in the surroundings can isolate individual populations [1,2,3]. Logging and agriculture can lead to dramatic changes in these habitats by increasing solar radiation influx and desiccation [4,7] Such changes can alter species communities, for example by causing the decline of less drought tolerant taxa [7]. The destruction of entire karst habitats can result in the loss of unique species communities and in the extinction of site-endemic taxa [7,11]

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