TY - JOUR

T1 - Afro-alpine flagships revisited

T2 - Parallel adaptation, intermountain admixture and shallow genetic structuring in the giant senecios (Dendrosenecio)

AU - Tusiime, Felly Mugizi

AU - Gizaw, Abel

AU - Gussarova, Galina

AU - Nemomissa, Sileshi

AU - Popp, Magnus

AU - Masao, Catherine Aloyce

AU - Wondimu, Tigist

AU - Abdi, Ahmed Abdikadir

AU - Mirré, Virginia

AU - Muwanika, Vincent

AU - Eilu, Gerald

AU - Brochmann, Christian

PY - 2020

Y1 - 2020

N2 - Distantly related lineages of the enigmatic giant rosette plants of tropical alpine environments provide classical examples of convergent adaptation. For the giant senecios (Dendrosenecio), the endemic landmarks of the East African sky islands, it has also been suggested that parallel adaptation has been important for within-lineage differentiation. To test this hypothesis and to address potential gene flow and hybridization among the isolated sky islands, we organized field expeditions to all major mountains. We sampled all currently accepted species and all but one subspecies and genotyped 460 plants representing 109 populations. We tested whether genetic structuring corresponds to geography, as predicted by a parallel adaptation hypothesis, or to altitudinal belt and habitat rather than mountains, as predicted by a hypothesis of a single origin of adaptations. Bayesian and Neighbor-Net analyses showed that the main genetic structure is shallow and largely corresponds to geography, supporting a hypothesis of recent, rapid radiation via parallel altitude/habitat adaptation on different mountains. We also found evidence for intermountain admixture, suggesting several long-distance dispersals by wind across vast areas of unsuitable habitat. The combination of parallel adaptation, secondary contact, and hybridization may explain the complex patterns of morphological variation and the contradicting taxonomic treatments of these rare enigmatic giants, supporting the use of wide taxonomic concepts. Notably, the within-population genetic diversity was very low and calls for increased conservation efforts.

AB - Distantly related lineages of the enigmatic giant rosette plants of tropical alpine environments provide classical examples of convergent adaptation. For the giant senecios (Dendrosenecio), the endemic landmarks of the East African sky islands, it has also been suggested that parallel adaptation has been important for within-lineage differentiation. To test this hypothesis and to address potential gene flow and hybridization among the isolated sky islands, we organized field expeditions to all major mountains. We sampled all currently accepted species and all but one subspecies and genotyped 460 plants representing 109 populations. We tested whether genetic structuring corresponds to geography, as predicted by a parallel adaptation hypothesis, or to altitudinal belt and habitat rather than mountains, as predicted by a hypothesis of a single origin of adaptations. Bayesian and Neighbor-Net analyses showed that the main genetic structure is shallow and largely corresponds to geography, supporting a hypothesis of recent, rapid radiation via parallel altitude/habitat adaptation on different mountains. We also found evidence for intermountain admixture, suggesting several long-distance dispersals by wind across vast areas of unsuitable habitat. The combination of parallel adaptation, secondary contact, and hybridization may explain the complex patterns of morphological variation and the contradicting taxonomic treatments of these rare enigmatic giants, supporting the use of wide taxonomic concepts. Notably, the within-population genetic diversity was very low and calls for increased conservation efforts.

KW - Adaptation, Biological

KW - Africa, Eastern

KW - Amplified Fragment Length Polymorphism Analysis/methods

KW - DNA, Plant/genetics

KW - Gene Flow

KW - Genotyping Techniques

KW - Hybridization, Genetic

KW - Phylogeny

KW - Phylogeography

KW - Senecio/anatomy & histology

UR - http://www.scopus.com/inward/record.url?scp=85081788266&partnerID=8YFLogxK

UR - https://journals.plos.org/plosone/article/comments?id=10.1371/journal.pone.0228979

UR - https://pubmed.ncbi.nlm.nih.gov/32187202/

U2 - 10.1371/journal.pone.0228979

DO - 10.1371/journal.pone.0228979

M3 - Article

C2 - 32187202

AN - SCOPUS:85081788266

VL - 15

JO - PLoS ONE

JF - PLoS ONE

SN - 1932-6203

IS - 3

M1 - e0228979

ER -