Evolutionary conservatism will limit responses to climate change in the tropics

Abstract

Rapid species turnover in tropical mountains has fascinated biologists for centuries. A popular explanation for this heightened beta diversity is that climatic stability at low latitudes promotes the evolution of narrow thermal tolerance ranges, leading to local adaptation, evolutionary divergence and parapatric speciation along elevational gradients. However, an emerging consensus from research spanning phylogenetics, biogeography and behavioural ecology is that this process rarely, if ever, occurs. Instead, closely related species typically occupy a similar elevational niche, while species with divergent elevational niches tend to be more distantly related. These results suggest populations have responded to past environmental change not by adapting and diverging in place, but instead by shifting their distributions to tightly track climate over time. We argue that tropical species are likely to respond similarly to ongoing and future climate warming, an inference supported by evidence from recent range shifts. In the absence of widespread in situ adaptation to new climate regimes by tropical taxa, conservation planning should prioritize protecting large swaths of habitat to facilitate movement.

Evolutionary and Ecological Explanations for the Elevational Flexibility of Several East African Bird Species Complexes

“…The flexibility in elevational distributions of birds in East Africa is quite distinct from what is described for avifaunas of larger and more connected montane regions at low latitudes, such as the Sino-Himalayan Mountains (Päckert et al, 2012) or the South American Andes, where lineages tend to evolve through geographical isolation within narrow elevational bands, with segregation into different ecological zones coming secondarily, by ecological segregation of independent and competing species (e.g., Cadena et al, 2012;Cadena and Cespedes, 2020;Linck et al, 2021).…”

Functional diversity of Himalayan bat communities declines at high elevation without the loss of phylogenetic diversity

“…Most importantly, these data hold relevance in understanding the impacts of range-shifts of vertebrate communities, driven by climate change. Studies on the speciation of tropical montane vertebrates show that many species are adapted to live within a narrow range of temperatures 64 . Not surprisingly, tropical species are shifting their elevational ranges faster than temperate species.…”

Nest architecture is linked with ecological success in songbirds

“…An alternative hypothesis for the reduced range of species that build domed nests is that these species have physiologically narrower thermal tolerances, which could result in both, selection for well-insulated nests, and narrower niches. Tropical species are suggested to have narrower thermal tolerances (Linck et al, 2021), and domed nests are common there. However, even within the tropics, species with open and cavity nests have broader ranges than domenesting species (Table S10).…”