Remarkably rapid, recent diversification of Cochemiea and Mammillaria in the Baja California, Mexico region

Peter B. Breslin, Martin F. Wojciechowski, Lucas C. Majure

Research output: Contribution to journalArticlepeer-review

Abstract

Premise: The Cactaceae of northwestern Mexico and the southwestern United States constitute a major component of the angiosperm biodiversity of the region. The Mammilloid clade, (Cactaceae, tribe Cacteae), composed of the genera Cochemiea, Coryphantha, Cumarinia, Mammillaria, and Pelecyphora is especially species rich. We sought to understand the timing, geographical and climate influences correlated with expansion of the Mammilloid clade, through the Sonoran Desert into Baja California. Methods: We reconstructed the historical biogeography of the Mammilloid clade, using Bayesian and maximum likelihood methods, based on a strongly supported molecular phylogeny. We also estimated divergence times, the timing of emergence of key characters, and diversification rates and rate shifts of the Mammilloid clade. Results: We found that the most recent common ancestor of Cochemiea arrived in the Cape region of Baja California from the Sonoran Desert region approximately 5 million years ago, coinciding with the timing of peninsular rifting from the mainland, suggesting dispersal and vicariance as causes of species richness and endemism. The diversification rate for Cochemiea is estimated to be approximately 12 times that of the mean background diversification rate for angiosperms. Divergence time estimation shows that many of the extant taxa in Cochemiea and Baja California Mammillaria emerged from common ancestors 1 million to 200,000 years ago, having a mid-Pleistocene origin. Conclusions: Cochemiea and Mammillaria of the Baja California region are examples of recent, rapid diversification. Geological and climatic forces at multiple spatial and temporal scales are correlated with the western distributions of the Mammilloid clade.

Original languageEnglish (US)
Pages (from-to)1472-1487
Number of pages16
JournalAmerican Journal of Botany
Volume109
Issue number9
DOIs
StatePublished - Sep 2022
Externally publishedYes

Keywords

  • Baja California
  • Cactaceae
  • Mammilloid clade
  • Sonoran Desert
  • ancestral state reconstruction
  • biogeography
  • endemism
  • evolution
  • rapid diversification

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Genetics
  • Plant Science

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