Climatic niche conservatism and ecological diversification in the Holarctic cold-dwelling butterfly genusErebia

Abstract

The evolution and distribution of alpine species have been modulated by their climatic niches. However, the relative roles of climatic niche conservatism promoting geographical speciation and of climatic niche diversification are poorly understood in diverse temperate groups. Here, we describe the evolution of climatic niche in a species rich butterfly genus, Erebia, which occurs across cold regions of the Holarctic and its diversity centre lies in European mountains. We inferred a nearly complete molecular phylogeny and modelled the climatic niche evolution using 25 thousand geo-referenced occurrence records. First, we reconstructed the evolution of the climatic niche. Second, we tested how the species' climatic niche width changes across the occupied climate gradient and compared the two main Erebia clades, the European and the Asian clade. Third, we explored climatic niche overlaps among species. We revealed that the evolution of Erebia has been shaped by climatic niche conservatism, supported by a strong phylogenetic signal and niche overlap in sister species, promoting allopatric speciation and by ecological speciation driven by specialization of climatic niches. However, the two main clades evolved their climatic niches toward different local optima. In addition, niche width decreases in extreme conditions of low and high temperatures and species in the diverse European clade have narrower niches compared to the Asian clade. This may be related to the gradient of climate seasonality, with lower European seasonality favouring the evolution of narrower niches. Our findings, coupled with declining diversification rates through time, support a diversity-dependent radiation scenario.

A macroevolutionary role for chromosomal fusion and fission inErebiabutterflies

“…The high karyotype diversity and associated high speciation rates of the tyndarus clade may in part be explained by their ecology. Species of the tyndarus clade occur almost exclusively in Alpine areas [ 22 ], whereas other Erebia clades are ecologically more diverse [ 23,51 ]. During glacial cycles, repeated range expansions and contractions across relatively small geographic areas, have caused population subdivisions of many Erebia species [e.g.…”

Body size, not species identity, drives body heating in alpineErebiabutterflies

“…To respond to local climatic conditions, butterfly species may evolve different physiological optima (MacLean et al, 2016), disperse to optimal climates (Konvicka et al, 2003) or change their thermoregulatory behaviour, e.g., by shifts of microhabitat use (Kirkpatrick & Sheldon, 2022; Wilson et al, 2015). Species-specific physiological optima evolved under the selection pressures exerted by the environment during the whole life cycle (Radchuk et al, 2013; Willmer, 1982), forming the species’ climatic niches (Klečková et al, 2022; Pitteloud et al, 2017). Ultimately, strong selection pressures of local conditions may result in local adaptation of adult thermoregulatory traits across climatic gradients, as has been reported in Melitaea cinxia butterflies (Advani et al, 2019; Mattila, 2015).…”