Competition matters: Determining the drivers of land snail community assembly among limestone karst areas in northern Vietnam

Abstract

The insular limestone karsts of northern Vietnam harbor a very rich biodiversity. Many taxa are strongly associated with these environments, and individual species communities can differ considerably among karst areas. The exact processes that have shaped the biotic composition of these habitats, however, remain largely unknown. In this study, the role of two major processes for the assembly of snail communities on limestone karsts was investigated, interspecific competition and filtering of taxa due to geographical factors. Communities of operculate land snails of the genus Cyclophorus were studied using the dry and fluid‐preserved specimen collections of the Natural History Museum, London. Phylogenetic distances (based on a Bayesian analysis using DNA sequence data) and shell characters (based on 200 semilandmarks) were used as proxies for ecological similarity and were analyzed to reveal patterns of overdispersion (indicating competition) or clustering (indicating filtering) in observed communities compared to random communities. Among the seven studied karst areas, a total of 15 Cyclophorus lineages were found. Unique communities were present in each area. The analyses revealed phylogenetic overdispersion in six and morphological overdispersion in four of seven karst areas. The pattern of frequent phylogenetic overdispersion indicated that competition among lineages is the major process shaping the Cyclophorus communities studied. The Coastal Area, which was phylogenetically overdispersed, showed a clear morphological clustering, which could have been caused by similar ecological adaptations among taxa in this environment. Only the community in the Cuc Phuong Area showed a pattern of phylogenetic clustering, which was partly caused by an absence of a certain, phylogenetically very distinct group in this region. Filtering due to geographical factors could have been involved here. This study shows how museum collections can be used to examine community assembly and contributes to the understanding of the processes that have shaped karst communities in Vietnam.

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

“…observation; see also [1] for the Malay Peninsula). Many Cyclophorus species differ considerably from each other in shell morphology and have relatively small distribution ranges [6,47]. However, representatives of this genus with a very similar shell morphology, to which we refer as the “widespread morphotype” in the present study, have been reported from large parts of Vietnam (including a number of national parks and nature reserves).…”

“…This material is part of the land snail collections of the Natural History Museum in London, which currently holds one of the largest scientific collections of Vietnamese Cyclophorus spp. [6]. The Cyclophorus material in the Natural History Museum’s collections comprises both, ethanol-preserved specimens and dry shells, partly with separate ethanol-preserved frozen tissue samples and/or viable cell preparations.…”

“…PCR conditions for COI were: 120 s at 94°C, 36 cycles (30 s at 94°C, 120 s at 42°C, 120 s at 72°C), and 300 s at 72°C [47]. PCR conditions for 16S and 28S were: 300 s at 94°C, 29 cycles (30 s at 95°C, 30 s at 52°C, 30 s at 72°C), and 300 s at 72°C [6]. Bi-directional DNA sequencing was carried out with an AB 3730XL DNA Analyzer (Applied Biosystems, Waltham, USA) using the BigDye Terminator v3.1 Cycle Sequencing Kit (Applied Biosystems, Waltham, USA).…”

“…Such limestone-associated organisms can occur in high abundances on karsts, while the often acidic soil in the surroundings can isolate individual populations [1–3]. Karst habitats in Southeast Asia harbour a rich biodiversity, which includes various site-endemic taxa [4], and individual species communities on different karsts in the same overall region can differ from each other considerably [1,5,6].…”

“…volvulus are also in use for morphologically similar members of the genus from other Asian countries [55–59]. The molecular phylogeny of Oheimb et al [6], however, recently provided evidence that snails of the widespread morphotype from different limestone karst areas in northern Vietnam belong to several distantly related Cyclophorus clades with none of them being closely related to C . fulguratus ( sensu [55]) and C .…”