Influence of Environmental Heterogeneity on the Species Composition, Species Richness and Species Abundances Unevenness in Reef-associated Conus Communities (Neogastropoda) from Papua New-Guinea

To what extent differences in species composition, species richness and species abundance unevenness between marine communities are attributable to heterogeneities of the surrounding environment and/or to inter-community distance is a fundamental issue to be addressed, in order to more deeply understand the functioning of marine ecosystems. A comparison between six reef-associated Conus communities, differing more or less in both their surrounding environment and their mutual geographical distance, offers a relevant opportunity to address these questions.

As expected, environmental heterogeneities prove having a significant influence on the dissimilarity in species composition, whereas distance-decay in similarity reveals comparatively negligible, at least within the investigated range of distances, up to 60 km. Less expectedly, more homogeneous surrounding environments between communities tend, here, to increase the dissimilarity in species richness. At last, here, difference in species abundance unevenness between communities seems unrelated to either environmental heterogeneity or inter-community distance.

From a methodological point of view, these results could not have been reliably established without the prior implementation of a least-biased procedure of numerical extrapolation applied to the available incomplete samplings. Also, the relevant assessment of dissimilarity in species composition required using a modified Jaccard index, rendered insensitive to bias-induced differences in communities species richness.