Résumé
The role of speciation processes in shaping current biodiversity patterns
represents a major scientific question for ecologists and biogeographers.
Hence, numerous methods have been developed to determine the geography of
speciation based on co-occurrence between sister-species. Most of these
methods rely on the correlation between divergence time and several
metrics based on the geographic ranges of sister-taxa (i.e. overlap,
asymmetry). The relationship between divergence time and these metrics has
scarcely been examined in a spatial context beyond regression curves.
Mapping this relationship across spatial grids, however, may unravel how
speciation processes have shaped current biodiversity patterns through
space and time. This can be particularly relevant for coral reef fishes of
the Indo-Pacific since the origin of the exceptional concentration of
biodiversity in the Indo-Australian Archipelago (IAA) has been actively
debated, with several alternative hypotheses involving species
diversification and dispersal. We reconstructed the phylogenetic
relationships between three species-rich families of coral reef fish
(Chaetodontidae, Labridae, Pomacentridae) and calculated co-occurrence
metrics between closely related lineages of those families. We
demonstrated that repeated biogeographic processes can be identified in
present-day species distribution by projecting co-occurrence metrics
between related lineages in a geographical context. Our study also
evidence that sister-species do not co-occur randomly across the
Indo-Pacific, but tend to overlap their range within the IAA. We
identified the imprint of two important biogeographic processes that
caused this pattern in 48% of the sister-taxa considered: speciation
events within the IAA and repeated divergence between the Indian and
Pacific Ocean, with subsequent secondary contact in the IAA.