Origin and diversification of the California flora: re-examining classic hypotheses with molecular phylogenies

Lesley T Lancaster, Kathleen M Kay

Research output: Contribution to journalArticlepeer-review

76 Citations (Scopus)


The California Floristic Province exhibits one of the richest floras on the planet, with more than 5500 native plant species, approximately 40% of which are endemic. Despite its impressive diversity and the attention it has garnered from ecologists and evolutionary biologists, historical causes of species richness and endemism in California remain poorly understood. Using a phylogenetic analysis of 16 angiosperm clades, each containing California natives in addition to species found only outside California, we show that CA's current biodiversity primarily results from low extinction rates, as opposed to elevated speciation or immigration rates. Speciation rates in California were lowest among Arcto-Tertiary lineages (i.e., those colonizing California from the north, during the Tertiary), but extinction rates were universally low across California native plants of all historical, geographic origins. In contrast to long-accepted ideas, we find that California diversification rates were generally unaffected by the onset of the Mediterranean climate. However, the Mediterranean climate coincided with immigration of many desert species, validating one previous hypothesis regarding origins of CA's plant diversity. This study implicates topographic complexity and climatic buffering as key, long-standing features of CA's landscape favoring plant species persistence and diversification, and highlights California as an important refuge under changing climates.

Original languageEnglish
Pages (from-to)1041-54
Number of pages14
Issue number4
Early online date31 Jan 2013
Publication statusPublished - Apr 2013

Bibliographical note

ACKNOWLEDGMENTSWe thank Emma Goldberg and Helene Morlon for generous assistancewith analyses and scripts, and Ammon Corl, Emma Goldberg, SusanHarrison, Christy Hipsley, Justen Whittall, associate editor Luke Harmon,and three anonymous reviewers for comments on the article. This workwas conducted while L. T. Lancaster was a center fellow at the NationalCenter for Ecological Analysis and Synthesis, funded by National ScienceFoundation grant No. EF-0553768, The University of California, SantaBarbara, and the State of California.


  • Angiosperms
  • Biodiversity
  • California
  • Climate
  • Evolution, Molecular
  • Extinction, Biological
  • Genetic Speciation
  • Phylogeny
  • Phylogeography
  • Fossils
  • Biogeography
  • Macroevolution
  • Phylogenetics
  • Speciation


Dive into the research topics of 'Origin and diversification of the California flora: re-examining classic hypotheses with molecular phylogenies'. Together they form a unique fingerprint.

Cite this