Exceptional biodiversity of the cryptofaunal decapods in the Chagos Archipelago, central Indian Ocean

Catherine E.I Head,Michael B Bonsall,Tom L Jenkins,Heather Koldewey,Morgan S Pratchett,Michelle L Taylor,Alex D Rogers

doi:10.1016/j.marpolbul.2018.07.063

Abstract

The Chagos Archipelago is geographically remote and isolated from most direct anthropogenic pressures. Here, we quantify the abundance and diversity of decapod crustaceans inhabiting dead coral colonies, representing a standardised microhabitat, across the Archipelago. Using morphological and molecular techniques we recorded 1868 decapods from 164 nominal species within 54 dead coral colonies, but total species estimates (Chao1 estimator) calculate at least 217 species. Galatheids were the most dominant taxa, though alpheids and hippolytids were also very abundant. 32% of species were rare, and 46% of species were found at only one atoll. This prevalence of rarer species has been reported in other cryptofauna studies, suggesting these assemblages maybe comprised of low-abundance species. This study provides the first estimate of diversity for reef cryptofauna in Chagos, which will serve as a useful baseline for global comparisons of coral reef biodiversity.

Highlights

There have been various predictions regarding the number of marine species on Earth, spanning several orders of magnitude (Grassel and Maciolek, 1992; May, 1994)
A total of 1868 individual decapods were recorded from 54 coral heads sampled across 25 sites at six atolls and islands in the Chagos Archipelago (Table 1)
At least 164 species of decapod crustaceans were recorded from dead coral colonies (n = 54 colonies) in the Chagos Archipelago

Summary

Introduction

There have been various predictions regarding the number of marine species on Earth, spanning several orders of magnitude (Grassel and Maciolek, 1992; May, 1994). Coral reef invertebrate species richness, described to date, is estimated at 168,000 species (Ruppert et al, 2004; Stella et al, 2011a), far surpassing the number of fish species (~5000 species; Bellwood et al, 2012) and reef-building corals (700 species; Veron, 2000). The majority of these reef invertebrates are small and cryptic, often referred to as the cryptofauna, and live within the reef framework itself (Reaka-Kudla, 1997; Plaisance et al, 2011). In recent years there have been several large-scale initiatives undertaken, such as the Census of Marine Life (http://www.creefs.org) and the Moorea Biocode Project (http://bscit.berkeley.edu/biocode), which have emphasised the importance of documentation of small and understudied organisms such as invertebrate and microbial species

Methods

Results

Conclusion