![]() He found that several communities of birds, mammals and insects were mainly restricted to one side of a narrow geographical area while fewer were found evenly on both sides 4, 5. In a seminal paper, Alfred Russel Wallace 4 was the first to formalize the affinities of two distinct biotic regions separated by the deep Makassar Strait. One of the most prominent biogeographical barriers is Wallace’s line, demarcating two biogeographical realms: the Asian (Sunda) and the Australian (Sahul) biota. In its heart lie 14 biodiversity hotspots delineated by sharp biogeographical boundaries 2. Situated between the Indian and Pacific Oceans, the region hereafter referred to as the Indomalayan-Australasian Archipelago (IAA) represents the largest and arguably most complex assemblage of islands in the world, housing a substantial proportion of Earth’s biodiversity 2, 3. Preeminent among such groups are the diurnal Lepidoptera or Butterflies, whose extreme beauty and endless diversity have led to their having been assiduously collected in all parts of the world ” Alfred Russel Wallace 1. ![]() “ for the purpose of investigating the phenomena of geographical distribution and of local or general variation, several groups differ greatly in their value and importance. This also suggests that current global changes may represent a serious conservation threat to this flagship group. Since birdwings were extinction-prone during the Miocene (warmer temperatures and elevated sea levels), the cooling period after the mid-Miocene climatic optimum fostered birdwing diversification due to the release of extinction. We demonstrated a pattern of spatio-temporal habitat dynamics that continuously created or erased habitats suitable for birdwing biodiversity. Palaeo-environment diversification models also suggest that high extinction rates occurred during periods of elevated sea level and global warming. ![]() The combination of maximum likelihood analyses to estimate biogeographical history and diversification rates reveals that diversity-dependence processes drove the radiation of birdwings and that speciation was often associated with founder-events colonizing new islands, especially in Wallacea. Bayesian phylogenetics and dating analyses of the birdwings were conducted using mitochondrial and nuclear genes. We analysed the macroevolutionary mechanisms accounting for the temporal and geographical diversification of the charismatic birdwing butterflies (Papilionidae), a major focus of Wallace’s pioneering work. One hundred and fifty years after Alfred Wallace studied the geographical variation and species diversity of butterflies in the Indomalayan-Australasian Archipelago, the processes responsible for their biogeographical pattern remain equivocal. ![]()
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