Abstract
Describing and understanding the spatial distribution of biological diversity and the processes underlying it is the core of population genetics and community ecology. If these two scales of biological organization (populations and communities) are governed by analogous evolutionary processes (drift, dispersal, selection), the spatial patterns of intra- and interspecific diversity should covary. However, observations do not always confirm this expectation, so that spatial congruence between genetic diversity within species and species diversity within communities is context-dependent. This thesis aims to study the processes that generate and maintain tropical marine fish assemblages, while assessing the conditions under which a positive correlation between genetic and species diversity is observed. To this end, we analyze in parallel the species diversity patterns of tropical marine fish communities, with the genetic diversity patterns of an Indo-Pacific fish (Etelis coruscans), 20 coral reef fish species from the Indian Ocean, and 15 species from the Caribbean Sea. We highlight the central role of neutral dispersal processes in structuring tropical fish communities at both intra- and interspecific scales. When dispersal limitation is the main determinant of β-diversity patterns, we observe positive spatial covariation between genetic and species β-diversities. Specifically, we demonstrate that the β-diversity continuum is modulated by several factors, including community delimitation, species dispersal abilities, and seascape structure. We also provide a proof-of-concept of the potential of environmental DNA metabarcoding for the unified and standardized study of spatial patterns of intra- and interspecific diversity in the marine environment. By integrating data from different biological, spatial and taxonomic scales in tropical fish, this thesis contributes to a better understanding of the eco-evolutionary processes that link scales of biological organization together.