Unmatched tempo of evolution in Southern African semi-desert ice plants

Abstract

The Succulent Karoo is an arid region, situated along the west coast of southern Africa. Floristically this region is part of the Greater Cape Flora and is considered one of the Earth's 25 biodiversity hotspots. Of about 5,000 species occurring in this region, more than 40% are endemic. Aizoaceae (ice plants) dominate the Succulent Karoo both in terms of species numbers (1,750 species in 127 genera) and density of coverage. Here we show that a well-supported clade within the Aizoaceae, representing 1,563 species almost exclusively endemic to southern Africa, has diversified very recently and very rapidly. The estimated age for this radiation lies between 3.8 and 8.7 million years (Myr) ago, yielding a per-lineage diversification rate of 0.77-1.75 per million years. Both the number of species involved and the tempo of evolution far surpass those of any previously postulated continental or island plant radiation. Diversification of the group is closely associated with the origin of several morphological features and one anatomical feature. Because species-poor clades lacking these features occur over a very similar distribution area, we propose that these characteristics are key innovations that facilitated this radiation.

Evolution along the crassulacean acid metabolism continuum

“…Although a well-resolved and comprehensively sampled molecular phylogeny of the Aizoaceae exists (Klak et al 2003(Klak et al , 2004, the occurrence of CAM has not been mapped onto the available phylogenetic tree. Similarly, an incomplete molecular phylogeny has been established for about two-thirds of species within the Agavaceae (Good-Avila et al 2006); however, most of those species are expected to perform CAM.…”

Diverse Fossil Epacrids (Styphelioideae; Ericaceae) from Early Pleistocene Sediments at Stony Creek Basin, Victoria, Australia

“…Thus, there is evidence suggesting recent and very rapid radiation of dry-climate taxa in South Africa (Klak et al 2004). This ambiguity is expressed by Hopper and Gioia (2004), who argued that much of the massive radiation of scleromorphs in southwestern Australia probably occurred in response to the rapid climate cycles of the Pleistocene but that the scleromorphic flora also included much older components.…”

Explosive Pleistocene diversification and hemispheric expansion of a “great speciator”

“…D isparity in diversification rates among groups of organisms is well documented and provides unique opportunities for studying evolutionary processes underlying the genesis of biological diversity (1)(2)(3)(4)(5)(6)(7). A few groups of organisms that diversified recently and rapidly have contributed disproportionately to speciation theory by providing comparatively accessible opportunities to evaluate factors that drive speciation (1)(2)(3)(4).…”