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

Joseph J. Milton, Matthias Affenzeller, Richard Abbott*, Hans P. Comes

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)
5 Downloads (Pure)

Abstract

Background: Parapatric (or ‘budding’) speciation is increasingly recognised as an important phenomenon in plant evolution but its role in extreme (e.g. desert) environments is poorly documented.


Aims: To test this speciation model in a hypothesised sister pair, the Southwest – North African disjunct Senecio flavus and its putative progenitor, the Namibian Desert endemic S. englerianus.


Methods: Phylogenetic inferences were combined with niche divergence tests, morphometrics, and experimental-genetic approaches. We also evaluated the potential role of an African Dry Corridor (ADC) in promoting the hypothesised northward expansion of S. flavus (from Namibia), using palaeodistribution models.


Results: Belonging to an isolated (potential ‘relict’) clade, the two morphologically distinct species showed pronounced niche divergence in Namibia and signs of digenic-epistatic hybrid incompatibility (based on F2 pollen fertility). The presence of ‘connate-fluked’ pappus hairs in S. flavus, likely increasing dispersal ability, is controlled by a single gene locus.


Conclusions: Our results provide evidence for a possible (and rare) example of ‘budding’ speciation in which a wider-ranged derivative (S. flavus) originated at the periphery of a smaller-ranged progenitor (S. englerianus) in the Namib Desert region. The Southwest – North African disjunction of S. flavus could have been established by dispersal across intermediate ADC areas during periods of (Late) Pleistocene aridification.
Original languageEnglish
Pages (from-to)329-353
Number of pages25
JournalPlant Ecology & Diversity
Volume15
Issue number5-6
Early online date12 Nov 2022
DOIs
Publication statusPublished - 12 Nov 2022

Keywords

  • African Dry Corridor
  • Budding speciation
  • Dispersal
  • Namib Desert
  • Niche differentiation
  • Phylogenetic relicts
  • Reproductive isolation barriers
  • Senecio

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