A test of the European Pleistocene refugial paradigm, using a Western Palaearctic endemic bird species

Abstract

Hewitt's paradigm for effects of Pleistocene glaciations on European populations assumes their isolation in peninsular refugia during glacial maxima, followed by re-colonization of broader Europe during interstadials. This paradigm is well supported by studies of poorly dispersing taxa, but highly dispersive birds have not been included. To test this paradigm, we use the dunnock ( Prunella modularis ), a Western Palaearctic endemic whose range includes all major European refugia. MtDNA gene tree, multilocus species tree and species delimitation analyses indicate the presence of three distinct lineages: one in the Iberian refugium, one in the Caucasus refugium, and one comprising the Italian and Balkan refugia and broader Europe. Our gene flow analysis suggests isolation of both the Iberian and Caucasus lineages but extensive exchange between Italy, the Balkans and broader Europe. Demographic stability could not be rejected for any refugial population, except the very recent expansion in the Caucasus. By contrast, northern European populations may have experienced two expansion periods. Iberia and Caucasus had much smaller historical populations than other populations. Although our results support the paradigm, in general, they also suggest that in highly dispersive taxa, isolation of neighbouring refugia was incomplete, resulting in large super-refugial populations.

Phylogeny of the Eurasian Wren Nannus troglodytes (Aves: Passeriformes: Troglodytidae) reveals deep and complex diversification patterns of Ibero-Maghrebian and Cyrenaican populations

“…A similar pattern of post-glacial range expansion has been inferred for the Dunnock, Prunella modularis [174]. In this species, northern Europe appears to have been colonised from Apennine and Balkan refugia, rather than from genetically distinct Iberian or Caucasian lineages.…”

Two ways to be endemic. Alps and Apennines are different functional refugia during climatic cycles

“…The continuous S‐shaped mountain‐hill system comprising the Alps and the Apennines (37° to 48° of latitude), encompasses the glacial refugium of the Italian Peninsula (Dapporto et al, 2019; Hewitt, 1999; Taberlet et al, 1998) and mountain areas covered by ice caps during glacial maxima (Figure 2a). Typically, the region is considered as a single biogeographic unit: the Italian refugium (Drovetski et al, 2018; Hewitt, 1999; Petit et al, 2003; Taberlet et al, 1998), but based on paleogeographic and paleoclimatic evidence (Figure 2a), we hypothesise that distinct EVOc and ECOc occur in this region. To test this, we (a) combined a massive data set of cytochrome c oxidase subunit 1 (COI) sequences and occurrence data to evaluate if different centres were recognisable by regionalisation analysis; (b) verified whether the endemics from the potential ECOc have stricter requirements in key ecological traits and encompass a lower phylogenetic diversity; and (c) verified whether endemics from potential EVOc show similar and shorter divergence times, being mostly represented by intraspecific genetic lineages.…”

“…However, the high endemic rate, mostly in ME of the Peninsula‐Sicily region indicates that northward shifts might be slowed down at least for many genetic lineages. The infrequent northward dispersal observed in Italian endemics is usually explained by the existence of the huge physical barrier of Alps (Drovetski et al, 2018; Hewitt, 1999). If so, we should find several endemics shared between the Apennines and the southern slopes of the Alps (pre‐Alps), a phenomenon which does not happen.…”

Phylogeography of a widespread Palaearctic forest bird species: The White‐backed Woodpecker (Aves, Picidae)

“…The Pleistocene has played a major role in the differentiation at the intraspecific and interspecific level of many temperate palaearctic organisms including forest and woodland birds (e.g. Brito, 2005; Drovetski et al., 2018; Hewitt, 2004; Kvist et al., 2004; Pons et al., 2011, 2015; Schmitt, 2007). Our genetic results support a mid‐Pleistocene divergence between lilfordi and leucotos .…”

“…The Western Palaearctic contains at least four primary areas that acted as refugia for forest birds: the Iberian Peninsula, Central Italy, the Balkans and the Caucasia (e.g. Drovetski et al., 2018; Hewitt, 2004). Under this scenario, we expect low genetic divergence, the sharing of mitochondrial haplotypes between leucotos and lilfordi and higher genetic diversity in lilfordi populations because it would have successfully persisted through Pleistocene climatic oscillations in one or several southern European refugia (Hewitt, 1996, 2000).…”