Climatic Niche Conservatism and Ecological Diversification in the Holarctic Cold-Dwelling Butterfly GenusErebia

Abstract

The diversification of alpine species has been modulated by their climatic niches interacting with changing climatic conditions. The relative roles of climatic niche conservatism promoting geographical speciation and of climatic niche diversification are poorly understood in diverse temperate groups. Here, we investigate the climatic niche evolution in a species rich butterfly genus, Erebia (Dalman, 1816). This Holarctic cold-dwelling genus reaches the highest diversity in European mountains. We generated a nearly complete molecular phylogeny and modeled the climatic niche evolution using geo-referenced occurrence records. We reconstructed the evolution of the climatic niche and tested how the species’ climatic niche width changes across the occupied climate gradient and compared two main Erebia clades, the European and the Asian clade. We further explored climatic niche overlaps among species. Our analyses 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, likely promoting allopatric speciation. The European and the Asian clades evolved their climatic niches toward different local optima. In addition, species in the European clade have narrower niches compared to the Asian clade. Contrasts among the clades may be related to regional climate differences, with lower climate seasonality in Europe compared to Central Asia favoring the evolution of narrower niches. Further, adaptive divergence could appear in other traits, such as habitat use, which can be reflected by narrower climatic niches detected in the European clade. Our study extends knowledge about the complexity of evolutionary drivers in temperate insects.

Asynchronous life cycles contribute to reproductive isolation between two Alpine butterflies

“…The apparent stable co-existence of both lineages at a narrow scale seems to have been maintained by temporal isolation through allochrony. The lack of broadscale coexistence between the two lineages is consistent with other Erebia species ( Augustijnen et al, 2022 ; Schmitt & Müller, 2007 ; Sonderegger, 2005 ) and E. euryale lineages ( Cupedo, 2014 ) and may suggest other mechanisms such as niche conservatism ( Klečková et al, 2022 ) or competitive exclusion through reproductive interference ( Vodă et al, 2015 ). Our studied lineages therefore fall within the “grey zone” of late-stage speciation ( Roux et al, 2016 ), where the level of genomic isolation is strong ( Figures 3 and 4 ) but reproductive isolation incomplete, preventing large-scale co-existence in sympatry.…”

Living on the edge—Genomic and ecological delineation of cryptic lineages in the high‐elevation specialist Erebia nivalis

“…This might result from habitat use differences between the Swiss and Austrian Alps at high elevations through niche conservatisms, or from environmental constraints. The availability of microhabitats also may differ across the range of this species so that habitat heterogeneity might contribute to persistence, as has been shown for other Erebia species (Klečková et al, 2023;Klečková & Klečka, 2016).…”

“…The genetic diversity of Erebia is often lower than that for other co-occurring butterflies, with little gene flow even between closely related species (Schmitt et al, 2016). Furthermore, the niches of Erebia are often narrow and conserved to their local optima and tend to become narrower with increasingly specialised living conditions (Klečková et al, 2023). The larval performance of several Erebia is similarly reduced when thermal conditions shift too far from their usual range, though some species seem to perform better under warmer conditions (Zografou et al, 2022).…”

A macroevolutionary role for chromosomal fusion and fission in Erebia butterflies

“…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 ( 23 ), whereas other Erebia clades are ecologically more diverse ( 24 , 53 ). During glacial cycles, repeated range expansions and contractions across relatively small geographic areas have caused population subdivisions of many Erebia species, e.g., ( 54 , 55 ), including the tyndarus clade ( 25 ).…”