Abstract
Climate change is often assumed to be a major driver of biodiversity loss. However, it can also set the stage for novel diversification in lineages with the evolutionary ability to colonize new environments. Here we tested if the extraordinary evolutionary success of the genus Pelargonium was related to the ability of its species to capitalize on the climate niche variation produced by the historical changes in southern Africa. We evaluated the relationship between rates of climate niche evolution and diversification rates in the main Pelargonium lineages and disentangled the roles of deep and recent historical events in the modification of species niches. Pelargonium clades exhibiting higher ecological differentiation along summer precipitation (SPP) gradients also experienced higher diversification rates. Faster rates of niche differentiation in spatially structured variables, along with lower levels of niche overlap among closely related species, suggest recent modification in species niches (e.g. dispersal or range shift) and niche lability. We suggest that highly structured SPP gradients established during the aridification process within southern Africa, in concert with niche lability and low niche overlap, contributed to species divergence. These factors are likely to be responsible for the extensive diversification of other lineages in this diversity hot spot.
Highlights
Patterns of species diversification associated with past climate shifts can offer insights into the processes generating biological diversity and may provide information on how lineages are likely to respond to future climate change
Lineages with rapidly evolving climatic preferences may have higher diversification success [1] because they are more likely to colonize and spread into new climate zones [2]. We know that this capacity is mainly determined by the extent to which their climate niche is evolutionarily conserved [3], so that if phylogenetic niche conservatism is strong, species will probably fail to adapt and experience greater risks of extinction if the new environments are different from their ancestral state
We showed that rapidly evolving climate preferences were mainly driven by spatial rather than phylogenetic variation
Summary
Patterns of species diversification associated with past climate shifts can offer insights into the processes generating biological diversity and may provide information on how lineages are likely to respond to future climate change. Phylogenetic niche conservatism among closely related species originates due to phylogenetic [5,8] or spatial constraints [8,9] or a combination of both. This is because both, inherited environmental preferences due to common ancestry or dispersal constraints in relation to the ancestral range, can shape the opportunities for adaptation to new environments [8]. Cooper et al [10] found that the large spatial component of mammal niche variation could be mostly explained by a modification in species niches that evolved in response to recent environmental changes - possibly related to dispersal or shifts in geographical ranges
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