Abstract
New Caledonia is a biodiversity hotspot, with an extremely high number of endemic species with narrow distribution ranges that are at high risk of extinction due to open-cast nickel mining, invasive species and seasonal man-induced fires. Mentions of micro-endemism permeate the literature on the biota of this archipelago. However, so far there has been no research comparing distribution range in different animal groups. The aim of this study is to examine the implication of different sampling effort variables in order to distinguish micro-endemicity from data deficiency, and evaluate the distribution range, frequency, and extent to which micro-endemism is common to several groups of organisms. We compiled a dataset derived from publications in Zoologia Neocaledonica, comprising 1,149 species, of which 86% are endemic to New Caledonia. We found that the sampling effort variables that were best correlated with distribution range were the number of sampling dates and the number of collectors per species. The median value of sampling dates was used to establish a cut-off point for defining adequately sampled species. We showed that, although only 52% of species were sampled adequately enough to determine their distribution range, the number of species with a very narrow distribution range was still high. Among endemics from New Caledonia, 12% (116 species) have ranges ≤5.2km2 and 3.9% (38 species) have ranges between 23 and 100 km2. Surprisingly, a similar trend was observed in non-endemic species: 22% occurred in areas ≤ 5.2 km2, and 8% in areas 23–100 km2, suggesting that environmental dissimilarity may play an important role in the distribution of these species. Micro-endemic species were predominant in 18 out of 20 orders. These results will contribute to a re-assessment of the IUCN red list of species in this archipelago, indicating that at least 116 species are probably critically endangered.
Highlights
We defined different distribution range classes for New Caledonia and explored (1) the frequency of species in these classes, (2) a set of sampling effort variables in order to find the ones that were more likely to have implications in determining a species distribution range; and (3) we investigated whether micro-endemism significantly occurred in a set of well-sampled species from diverse taxonomic groups
New Caledonia is an oceanic archipelago in the Pacific Ocean located between 18 ̊–23 ̊ S and 163 ̊–169 ̊ E
Micro-endemicity has frequently been reported in researches for different groups of the New Caledonian fauna [10, 14, 16, 23, 26,27, 31], the present study is the first to be designed to quantify its distribution range, estimate its frequency, and determine the extent to which these findings are common to several taxonomic groups
Summary
The aim of this study is to examine the implication of different sampling effort variables in order to distinguish microendemicity from data deficiency, and evaluate the distribution range, frequency, and extent to which micro-endemism is common to several groups of organisms
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