Frequent colonization and little in situ speciation in Senecio in the tropical alpine‐like islands of eastern Africa

Abstract

PREMISE OF THE STUDY:Floras of continental habitat islands, like those of islands, originate mostly through colonization, which can be followed by in situ speciation. We here address the question of the relative importance of colonization and in situ diversification in the high‐altitude areas of the eastern African high mountains, the tropical Afroalpine Region, using the most species‐rich genus in the region, Senecio, as an example.METHODS:We expanded earlier Senecioneae phylogenies by adding more tropical African species and analyzed our phylogenetic tree biogeographically.KEY RESULTS:Senecio contains at least five clades with tropical African species, all of them containing tropical afroalpine species. Between four to 14 independent colonization events into the tropical Afroalpine most likely from montane regions in southern Africa were found. Additionally, relationships of tropical afroalpine species to Palearctic and South American taxa were identified. Although some in situ diversification occurred in Senecio in the tropical Afroalpine, the resulting number of species per clade is never higher than seven.CONCLUSION:Like other genera, Senecio colonized the tropical Afroalpine several times independently. Comparison with Mt. Kinabalu, a small tropical alpine‐like region in Southeast Asia, and alpine‐like regions in the Andes implies that rates of in situ speciation might be linked to area size.

Comparative genomics of 11 complete chloroplast genomes of Senecioneae (Asteraceae) species: DNA barcodes and phylogenetics

“…These findings were supported by results obtained from the DNA polymorphism test based on genus representatives, as same regions were noted to have high nucleotide variability (Pi). Some of these regions have previously been reported in chloroplast genomes of other species (Salih et al 2017; Wu et al 2018) and used in phylogenetic studies of numerous taxa including Senecio (Kandziora et al 2016). Non-coding regions in chloroplast genomes have shown high potential for use as molecular markers for phylogenetic studies at low taxonomic levels in Angiosperms (Shaw et al 2005).…”

Staying cool: preadaptation to temperate climates required for colonising tropical alpine-like environments

“…Most studies reflect a strong notion of (broad) climatic niche conservatism within genera. However, genera are a poor proxy for independent evolutionary lineages in the tropical alpine, as shown by the various African taxa derived from multiple independent colonisation events from Eurasia ( Assefa et al 2007 ; Gehrke and Linder 2009 ), Southern Africa ( Galley et al 2007 ' Kandziora et al 2016 ) or lower elevations ( Knox 2004 ; Galbany-Casals et al 2014 ). Prominent examples of these repeated colonisations of the Afroalpine are the giant lobelias and giant senecios, which have both been postulated to have originated by repeated upward adaptation to alpine-like environments ( Knox 2004 ).…”

On the Causes of Rapid Diversification in the Páramos: Isolation by Ecology and Genomic Divergence in Espeletia

“…2800–4700), that despite its small surface area (35,000 km 2 ), may contain over 3,000 plant species, many of which are found nowhere else on the planet (Luteyn, 1999; Hughes and Atchison, 2015). Plant groups that occupy these ‘sky islands’ (Sklenář et al, 2014) are therefore good candidates to explore ecological divergence because they are a likely product of unique adaptations to an extreme environment that evolved during the last five million years when the Andes reached an altitude that was capable of sustaining this type of vegetation (Antonelli et al, 2009; Hoorn et al, 2010; Madriñán et al, 2013). Three hypotheses have been proposed to explain the unparalleled diversification rate in the Páramo.…”