Rare and widespread: integrating Bayesian MCMC approaches, Sanger sequencing and Hyb-Seq phylogenomics to reconstruct the origin of the enigmatic Rand Flora genus Camptoloma

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Culshaw, Victoria and Villaverde, Tamara and Mairal Pisa, Mario and Olsson, Sanna and Sanmartín, Isabel (2021) Rare and widespread: integrating Bayesian MCMC approaches, Sanger sequencing and Hyb-Seq phylogenomics to reconstruct the origin of the enigmatic Rand Flora genus Camptoloma. American Journal of Botany, 108 (9). pp. 1673-1691. ISSN 0002-9122, ESSN: 1537-2197

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Official URL: https://doi.org/10.1002/ajb2.1727



Abstract

Premise
Genera that are widespread, with geographically discontinuous distributions and represented by few species, are intriguing. Is their achieved disjunct distribution recent or ancient in origin? Why are they species-poor? The Rand Flora is a continental-scale pattern in which closely related species appear codistributed in isolated regions over the continental margins of Africa. Genus Camptoloma (Scrophulariaceae) is the most notable example, comprising three species isolated from each other on the northwest, eastern, and southwest Africa.

Methods
We employed Sanger sequencing of nuclear and plastid markers, together with genomic target sequencing of 2190 low-copy nuclear genes, to infer interspecies relationships and the position of Camptoloma within Scrophulariaceae by using supermatrix and multispecies-coalescent approaches. Lineage divergence times and ancestral ranges were inferred with Bayesian Markov chain Monte Carlo (MCMC) approaches. The population history was estimated with phylogeographic coalescent methods.

Results
Camptoloma rotundifolium, restricted to Southern Africa, was shown to be a sister species to the disjunct clade formed by C. canariense, endemic to the Canary Islands, and C. lyperiiflorum, distributed in the Horn of Africa–Southern Arabia. Camptoloma was inferred to be sister to the mostly South African tribes Teedieae and Buddlejeae. Stem divergence was dated in the Late Miocene, while the origin of the extant disjunction was inferred as Early Pliocene.

Conclusions
The current disjunct distribution of Camptoloma across Africa was likely the result of fragmentation and extinction and/or population bottlenecking events associated with historical aridification cycles during the Neogene; the pattern of species divergence, from south to north, is consistent with the “climatic refugia” Rand Flora hypothesis.


Item Type:Article
Uncontrolled Keywords:aridification; biogeographic disjunctions; climate change; extinction; relict species; Scrophulariaceae
Subjects:Medical sciences > Biology > Botany
Medical sciences > Biology > Evolution
Medical sciences > Biology > Genetics
ID Code:72117
Deposited On:05 May 2022 15:10
Last Modified:06 May 2022 07:17

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