Phylogeny and palaeoecology of Polyommatus blue butterflies show Beringia was a climate-regulated gateway to the New World

Abstract

Transcontinental dispersals by organisms usually represent improbable events that constitute a major challenge for biogeographers. By integrating molecular phylogeny, historical biogeography and palaeoecology, we test a bold hypothesis proposed by Vladimir Nabokov regarding the origin of Neotropical Polyommatus blue butterflies, and show that Beringia has served as a biological corridor for the dispersal of these insects from Asia into the New World. We present a novel method to estimate ancestral temperature tolerances using distribution range limits of extant organisms, and find that climatic conditions in Beringia acted as a decisive filter in determining which taxa crossed into the New World during five separate invasions over the past 11 Myr. Our results reveal a marked effect of the Miocene–Pleistocene global cooling, and demonstrate that palaeoclimatic conditions left a strong signal on the ecology of present-day taxa in the New World. The phylogenetic conservatism in thermal tolerances that we have identified may permit the reconstruction of the palaeoecology of ancestral organisms, especially mobile taxa that can easily escape from hostile environments rather than adapt to them.

Diversification of the cold-adapted butterfly genus Oeneis related to Holarctic biogeography and climatic niche shifts

“…Vila et al, 2011;Condamine et al, 2012;Bentley et al, 2014). A clade is rarely the pure product of allopatry (Muller and Beharegaray, 2010;Imada et al, 2011).…”

“…Distributions of Holarctic organisms were shaped by climatic changes during the past 15 million years (Vila et al, 2011), the effect of which interacted with regional topographies (Todisco et al, 2012). Cold periods interconnected biota across the Holarctic by promoting lowland dispersal events (Schmitt and Haubrich, 2008;Todisco et al, 2012) and movements of Arctic assemblages to southern latitudes (Päckert et al, 2012;Eidesen et al, 2013) followed by in-situ speciation (Vila et al, 2011).…”

“…Cold periods interconnected biota across the Holarctic by promoting lowland dispersal events (Schmitt and Haubrich, 2008;Todisco et al, 2012) and movements of Arctic assemblages to southern latitudes (Päckert et al, 2012;Eidesen et al, 2013) followed by in-situ speciation (Vila et al, 2011). This connectivity was probably associated to species' ecological q This paper was edited by the Associate Editor Francesco Frati.…”

“…preferences (Vila et al, 2011). For instance, dry-adapted alpine species widely dispersed to lowlands (Schmitt and Hewitt, 2004), which had mainly an arid character, whereas alpine species not tolerant of dryness were restricted to more humid areas (e.g.…”

“…Butterflies show conservatism in their habitat affiliations (van Swaay et al, 2006) and thermal niches (cf. Vila et al, 2011;Kleckova et al, 2014), but this remains to be tested in the evolution of cold-adapted butterfly lineages. The butterfly genus Oeneis, Hübner, 1819 (Lepidoptera: Satyrinae) arose in the Miocene (Peña et al, 2011) and diversified into 30 species across the mountains and Arctic of the Holarctic region.…”