Progressive Recovery of a Marine Gastropod Community Following Atmospheric Nuclear Tests in French- Polynesia: A Socio-ecological Interpretation

Abstract

Aims: The way species-richness is accommodated and how species-abundance distribution is organized in a hierarchic pattern is central to community ecology. Yet, the process by which species-richness and species-abundances are progressively accommodated can hardly be monitored, in practice, at a sufficiently large spatial scale. Fortunately, the progressive recovery of marine communities, after their complete destruction by atmospheric nuclear tests, yet offered unique opportunity to monitor the full process of accommodation of increasing species-richness and the associated, transient development of strong interspecific competition, all along the process of recovery. Methods: Taking full advantage of such monitoring yet requires, first, to relevantly overcome two important practical issues: 1) achieving reliable numerical extrapolations of the usually unavoidably incomplete samplings in order to accurately estimate both the true species-richness and the completed distribution of species-abundances, including the abundance of undetected species and 2) disentangling (i) the positive contribution of improved niche-diversification to species-richness and species-abundance evenness from (ii) the negative contribution of increasing interspecific-competition, all along the recovery progress. This, indeed, is a rather tricky challenge, yet relevantly solved by using the newly developed “standardized unevenness index”, conceptually based upon MacArthur approach to interspecific-contest at niche overlaps. Results: Applying both tools above to the monitored recovery of a reef-associated Gastropod community, entirely wiped-out previously by severe nuclear blasts, had allowed a deeper understanding of the dynamic interplay between species-recruitment, niche-diversification and interspecific-competition in the regeneration of the community. In particular, along the recovery process, a transient, metastable phase – involving severe interspecific-competition at niche-overlaps – precedes a gradual return to dynamic stability, with the virtual extinction of interspecific competition