Abstract
The sponge Leucetta chagosensis Dendy (1913) has a wide distribution throughout the Indo-Pacific (IP) region, with previous studies focussing primarily on the western Pacific Ocean. To increase our knowledge of the spatial variation of genetic diversity throughout the IP, we constructed a phylogeny for L. chagosensis for the IP to assess the evolutionary patterns for this species. We generated 188 sequences of L. chagosensis and constructed maximum likelihood and Bayesian inference trees, using concatenated mitochondrial cytochrome oxidase subunit 3 gene (cox3) and nuclear ribosomal RNA gene (28S) markers for the first time. The spatial variation of genetic diversity of L. chagosensis was assessed using a phylogeographic approach. Leucetta chagosensis is composed of five cryptic lineages confined to different biogeographic regions with the specimens found in the Indian Ocean differing significantly from those found in the rest of the IP region. Genetic divergence was particularly high for the cox3 marker, with a low nucleotide diversity but high haplotype diversity for most lineages. This study highlights the need for a sustained effort in studying sponge diversity, boosted by the ongoing discovery of hidden biodiversity among this ecologically important taxon.
Highlights
Phylogeography has provided numerous insights into the distribution of genetic variation in terrestrial and aquatic ecosystems
The separate Maximum likelihood (ML) (Supplementals S3 and S4) and Bayesian inference (BI)-based phylogenetic reconstructions for the cox3 and 28S markers were different, with the phylogeny estimated from cox3 having higher support based on bootstrap and posterior probability values
We unravelled the phylogeographic relationships of L. chagosensis lineages across the known biogeographic range, using a combination of nuclear and mitochondrial DNA markers
Summary
Phylogeography has provided numerous insights into the distribution of genetic variation in terrestrial and aquatic ecosystems. Phylogeographical studies have the potential to support effective conservation strategies [5], especially for threatened marine environments like the Indian Ocean [6,7]. The IO has been neglected from a bio- and phylogeographical standpoint, compared to the rest of the Indo-Pacific (IP) region [11]. This lack of information is concerning because baseline biodiversity information is essential for any conservation plan that aims to mitigate climate change impacts [12,13,14,15] and over-exploitation [16,17,18].
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