Phylogeography at the crossroad: Pleistocene range expansion throughout the Mediterranean and back‐colonization from the Canary Islands in the legume Bituminaria bituminosa

Abstract

Aim Species with widespread distributions offer excellent opportunities for investigating recent biogeographical patterns across broad scales. Here, we tested the hypothesis that, due to its intermediate geographical location, NW Africa is pivotal in explaining the phylogeographical patterns of taxa with Mediterranean–Macaronesian distributions using a legume species with short generation times. Location Mediterranean, with a focus on NW Africa and the Canary Islands. Taxon Pitch trefoil (Bituminaria bituminosa). Methods We generated genetic data and performed phylogeographical and demographic analyses at two geographical scales: Mediterranean Basin (MB), using plastid sequences (115 individuals), and Macaronesia, using plastid sequences (182 individuals) and 10 nuclear microsatellite loci (220 individuals). We also performed a literature survey focusing on phylogeographical studies of other circum‐Mediterranean taxa. Results Northwest Africa was identified as a centre of genetic diversity (19 out of 38 haplotypes) and demographic expansion of B. bituminosa in the MB during the Pleistocene. Our literature review revealed two main phylogeographical patterns in widespread species: pre‐Mediterranean evergreen sclerophylls versus Pleistocene facultative‐deciduous (including Bituminaria) taxa, but on average, both functional groups show a similar, large genetic diversity (~40% of haplotypes) in NW Africa. At the Macaronesian scale, we found that Canarian Bituminaria is composed of two genetic sublineages that coexist and hybridize on the central islands and in the mainland Macaronesian enclave (Anti‐Atlas region). Demographic analyses rejected the progression rule as the model of island colonization but strongly suggested that Anti‐Atlas populations are the result of back‐colonization from the easternmost islands before the Last Glacial Maximum (LGM). Conclusions Bituminaria displays a pattern of Quaternary eastward expansion in the MB that appears to be paralleled by several members of its functional plant group. Thus, our study reveals a previously undescribed dual role of NW Africa in plant biogeography, acting both as a source of species expansion to the rest of the MB and a LGM refugium of plant populations with a Macaronesian island origin.

Drivers of genetic differentiation and recent evolutionary history of an Eurasian wild pea

“…A process that could still be ongoing. Such an eastward expansion from refugia was also observed in other pan-Mediterranean legumes like narrow-leafed lupin ( Lupinus angustifolius ; Mousavi-Derazmahalleh et al, 2018) and pitch trefoil ( Bituminaria bituminosa ; García-Verdugo et al, 2021). The main difference between the Lupinus and Bitumenaria cases and wild peas is that the center of diversity of narrow-leafed lupin and pitch trefoil is located in the western rather than the eastern Mediterranean.…”

Drivers of genetic differentiation and recent evolutionary history of an Eurasian wild pea

“…A process that could still be ongoing. Such an eastward expansion from refugia was also observed in other pan-Mediterranean legumes like Lupinus angustifolius (Mousavi-Derazmahalleh et al, 2018) and Bituminaria bituminosa (García-Verdugo et al, 2021). The main difference between the Lupinus and Bitumenaria cases and wild peas is that the centre of diversity of narrow-leafed lupin and pitch trefoil is located in the western rather than the eastern Mediterranean.…”

Genome-wide footprints in the carob tree (Ceratonia siliqua) unveil a new domestication pattern of fruit trees in the Mediterranean

“…Intense research on plant phylogenetics and phylogeography over the last two decades have allowed the discovery of several major biogeographical trends in the Mediterranean basin (Garcia-Verdugo et al, 2021) and renewed our understandings of plant domestication (Purugganan, 2019). Following an initial focus on biogeographic refugia, recent studies have revealed the genetic imprints of past expansions and migration processes, some involving the entire Mediterranean basin (see reviews in Medail and Diadema 2009;Nieto Feliner 2011;Nieto Feliner, 2014;Migliore et al, 2018;Vargas et al, 2018;Thompson, 2020;Garcia-Verdugo et al, 2021). Our study provides a better understanding of the phylogeography of Mediterranean plants by revealing a new historical scenario: the main gene pools of carob (i.e.…”

“…As for several crops, the Near East and the Eastern Mediterranean were initially proposed as the center of domestication for the carob tree (Zohary, 2002;Ramon-Laca and Mabberley, 2004). However, a recent multidisciplinary phylogeographic study based on wild and cultivated carob trees revealed the existence of four main genetic groups across the Mediterranean with a strong west-east structure (Viruel et al, 2020), which has also been documented for other Mediterranean plants (Désamoré et al 2011;Nieto Feliner 2014;Chen et al 2014;Migliore et al 2018;Garcia-Verdugo et al 2021). Using coalescent simulations based on microsatellite data, the estimated divergence times between these genetic groups pre-date the Neolithic origin of agriculture (Viruel et al, 2020).…”