From the Namib around the world: biogeography of the Inuleae–Plucheinae (Asteraceae)

Abstract

Aim We investigated the historical biogeography of the Inuleae-Plucheinae (Asteraceae), a group of arid-adapted plants with partly unresolved generic circumscriptions, in order to understand its origin and spatiotemporal evolutionary history in relation to the Cenozoic climate shifts.Location Global, with highest species diversity in the Southern Hemisphere.Methods The spatiotemporal biogeography of the Plucheinae was estimated by both a discrete method using a set of general distribution areas, and a relaxed random walk based on extant species distributions. The topology was time calibrated using a combination of secondary node ages and secondary derived rates for included loci.Results Our results indicate the median age of the Plucheinae to be approximately 15.4 Ma. The biogeographical analyses infer an ancestral origin in southern Africa, with the relaxed random walk analysis narrowing the uncertainty down to an area reaching from coastal Namibia to the western Kalahari. Africa was colonized in a (south)western-(north)eastern direction following the spread of arid habitats. Ancestral representatives of the Plucheinae colonized South America on at least three separate occasions (13.0-4.0, 4.3-3.1 and 4.1-3.7 Ma), with one subsequent spread to North America. Australia was colonized three times between 3.6 and 0.4 Ma. Madagascar and the Mascarenes were colonized at least seven times.Main conclusions The origin of the Plucheinae is estimated to the Namib region, with early speciations and radiations concurring with the timing of aridification of southern Africa, following the increase in strength of the Antarctic Circumpolar Current and subsequent formation of the Benguela Upwelling at c. 11.8 Ma. The current biogeographical distribution of the Plucheinae is best explained by several Neogene long-distance dispersal events from tropical Africa.

Species diversification in the Mediterranean genus Chiliadenus (Inuleae-Asteraceae)

“…3). The estimated ages found in the present study fit well within the age of the Inuleae recovered by earlier studies (Nylinder et al 2016). The ancestors of Chiliadenus and Dittrichia are estimated to have diverged around 5.45 Ma (3.25-8.55 Ma) somewhere in the area around continental southwestern Europe, Morocco, and northwestern Algeria (Fig.…”

Metapopulation Vicariance, Age of Island Taxa and Dispersal: A Case Study Using the Pacific Plant Genus Planchonella (Sapotaceae)

“…Ancestral areas were estimated by modeling geographic movements across a continuous landscape using a relaxed random walk (Lemey et al 2010), where locations are defined as coordinates in decimal grades for each accession. Random walk methods are preferable over the use of discrete areas, since they circumvent the need to define arbitrary operational areas, and this approach has been used on species-level phylogenies and is largely congruent with results from discrete methods (Nylinder et al 2014, 2016; Bengtson et al 2015; Johansson et al 2018). Therefore, we argue that the biogeographic history of a plant genus scattered across numerous islands in the Pacific and adjacent regions, is better captured by a method that does not restrict the analysis to movement between larger, simplified discrete areas.…”

Plant speciation in the Namib Desert: origin of a widespread derivative species from a narrow endemic

“…They also confirm earlier phylogenetic estimates (Pelser et al 2007) Nevertheless, our estimated stem age for this 'petiolate' clade remarkably coincides with the onset of cold north-bound currents along the southwestern coast of Africa (Benguela-Namib Upwelling, BNU) during the early Late Miocene (c. 12-10 Mya; due to an increase in strength of the Antarctic Circumpolar Current, ACC; c. 14 Mya), and which triggered (or intensified) arid or semi-arid conditions in today's Namib Desert region (e.g. Heinrich et al 2011;Rommerskirchen et al 2011;Nylinder et al 2016;Wan et al 2021). By contrast, the clade's much younger crown age slighty post-dates the strengthening and further (abrupt) cooling of the BNU system during the Early Pleistocene (c. 2.1 to 1.9 Mya; Marlow et al 2000; see also Berger et al 2002;Rommerskirchen et al 2011) combined with low (or heterogenous) rates of net diversification rather than high rates of extinction (Donoghue and Sanderson 2015).…”