Abstract
Endemism, which is typically high on islands and in caves, has rarely been studied in the cave entrance ecotone. We investigated the endemism of the spider genus Uthina at cave entrances. Totally 212 spiders were sampled from 46 localities, from Seychelles across Southeast Asia to Fiji. They mostly occur at cave entrances but occasionally appear at various epigean environments. Phylogenetic analysis of DNA sequence data from COI and 28S genes suggested that Uthina was grouped into 13 well-supported clades. We used three methods, the Bayesian Poisson Tree Processes (bPTP) model, the Bayesian Phylogenetics and Phylogeography (BPP) method, and the general mixed Yule coalescent (GMYC) model, to investigate species boundaries. Both bPTP and BPP identified the 13 clades as 13 separate species, while GMYC identified 19 species. Furthermore, our results revealed high endemism at cave entrances. Of the 13 provisional species, twelve (one known and eleven new) are endemic to one or a cluster of caves, and all of them occurred only at cave entrances except for one population of one species. The only widely distributed species, U. luzonica, mostly occurred in epigean environments while three populations were found at cave entrances. Additionally, eleven new species of the genus are described.
Highlights
Endemism, which is typically high on islands and in caves, has rarely been studied in the cave entrance ecotone
Since its Bayesian inference (BI) tree topology was slightly different from its maximum likelihood (ML) tree, we conducted the same analysis based on the BI tree topology, and the analysis identified 14 provisional species
cytochrome oxidase I gene (COI) p-distances distribution (Fig. 3), and distance values between the majority of the 13 provisional species are above the gap (>8.3%)
Summary
Endemism, which is typically high on islands and in caves, has rarely been studied in the cave entrance ecotone. 212 spiders were sampled from 46 localities, from Seychelles across Southeast Asia to Fiji They mostly occur at cave entrances but occasionally appear at various epigean environments. The typical cave environment in the deep interior is usually considered climatically stable, possessing constant temperature and humidity, with complete darkness and scarce energy sources[9]. These extreme environmental conditions and the limited dispersal ability of cave-dwellers have been regarded as the primary factors of maintaining endemism within caves[10,11]. Cave entrances possess several unique traits that make them potentially areas of high endemism They represent the transition zones between epigean and hypogean environments. We predict that, similar to caves, the unique habitat conditions of cave entrances and the potentially reduced interchange between populations from geographically separate cave entrances likely promote the development of high endemism
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