Molluskan species richness and endemism on New Caledonian seamounts: Are they enhanced compared to adjacent slopes?

Seamounts were often considered as ‘hotspots of diversity’ and ‘centers of endemism’, but recently this opinion has been challenged. After 25 years of exploration and the work of numerous taxonomists, the Norfolk Ridge (Southwest Pacific) is probably one of the best-studied seamount chains worldwide...

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Bibliographic Details
Published in:Deep-sea research. Part I, Oceanographic research papers Oceanographic research papers, 2011-06, Vol.58 (6), p.637-646
Main Authors: Castelin, Magalie, Puillandre, Nicolas, Lozouet, Pierre, Sysoev, Alexander, de Forges, Bertrand Richer, Samadi, Sarah
Format: Article
Language:eng ; rus
Subjects:
Biological diversity
Deep sea
Dispersal
Diversity
Endemism
Estimates
Estimating techniques
Marine
Mollusks
New Caledonia
Ridges
Sampling
Seamount
Seamounts
Shells
Slopes
Species richness
Taxonomy
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Summary:Seamounts were often considered as ‘hotspots of diversity’ and ‘centers of endemism’, but recently this opinion has been challenged. After 25 years of exploration and the work of numerous taxonomists, the Norfolk Ridge (Southwest Pacific) is probably one of the best-studied seamount chains worldwide. However, even in this intensively explored area, the richness and the geographic patterns of diversity are still poorly characterized. Among the benthic organisms, the post-mortem remains of mollusks can supplement live records to comprehensively document geographical distributions. Moreover, the accretionary growth of mollusk shells informs us about the life span of the pelagic larva. To compare diversity and level of endemism between the Norfolk Ridge seamounts and the continental slopes of New Caledonia we used species occurrence data drawn from (i) the taxonomic literature on mollusks and (ii) a raw dataset of mainly undescribed deep-sea species of the hyperdiverse Turridae. Patterns of endemism and species richness were analyzed through quantitative indices of endemism and species richness estimator metrics. To date, 403 gastropods and bivalves species have been recorded on the Norfolk Ridge seamounts. Of these, at least 38 species (∼10%) are potentially endemic to the seamounts and nearly all of 38 species have protoconchs indicating lecithotrophic larval development. Overall, our results suggest that estimates of species richness and endemism, when sampling effort is taken into account, were not significantly different between slopes and seamounts. By including in our analyses 347 undescribed morphospecies from the Norfolk Ridge, our results also demonstrate the influence of taxonomic bias on our estimates of species richness and endemism. ► We analyze mollusk diversity on the Norfolk seamounts and New Caledonia slopes. ► We examine the effect of dispersal on the endemism between seamounts and slopes. ► Endemism and species richness are not significantly higher on seamounts. ► Most endemic species have protoconchs indicating lecithotrophic larval development. ► Endemism estimates on seamounts are biased because of sampling and taxonomic biases.
ISSN:0967-0637
1879-0119
DOI:10.1016/j.dsr.2011.03.008