Evolutionary convergences and divergences in sympatric species: Morpho butterflies as a case study.

Abstract

How do closely related species interact in sympatry? And how do these interactions influence the evolution of their traits and the dynamics of species diversification? In this review, we show how recent research on the evolution of Morpho butterflies contributes to address these questions. We first show how sympatric species have colonized different vertical strata in the neotropical forest and how this divergence has produced cascading adaptive effects on behavioural (flight) but also morphological traits, including wing size, shape and coloration. We then focus on the evolution of peculiar dorsal blue coloration within the genus Morpho. During flight, the blue iridescence produces bright flashes that confuse predators and likely enhance the escape abilities of these butterflies. In turn, predators learn the association between such conspicuous coloration and escaping capacities. Such learning favours the locally abundant colour pattern and promotes the local convergence in sympatric species. However, this tight resemblance also induces sexual interference between mimetic species. Capture-Mark-Recapture data uncovered that mimetic species do not fly at the same hours: competition seems to have driven the divergence in the timing of flight activity between species. Overall, sympatry therefore promotes the intricated evolution of convergent and divergent traits among tightly related species, that jointly facilitate their coexistence. Whether ecological speciation was involved in this evolution is an intriguing open question. At the genomic level, analyses revealed a faster evolution of the sexual chromosome Z as compared to the autosomes, with extensive rearrangements and molecular signals of positive selection: these data thus suggest an important role for the Z chromosome in adaptive evolution in Morpho and possibly in speciation. Paving the way for future research, these various, multilevel studies show that Morpho are not just those showy butterflies in the box: they can also teach us much about evolutionary processes.