The diversification of Caribbean Buxus in time and space: elevated speciation rates in lineages that accumulate nickel and spreading to other islands from Cuba in non-obligate ultramafic species.

Pedro A González Gutiérrez, Susy Fuentes-Bazan, Vanessa Di Vincenzo, Rosalina Berazaín-Iturralde, Thomas Borsch

Annals of botany 2023 Aug 25

filter terms:

The genus Buxus has high levels of endemism in the Caribbean flora, with ~50 taxa. In Cuba, 82 % grow on ultramafic substrates and 59 % are nickel (Ni) accumulators or Ni hyperaccumulators. Hence it is an ideal model group to study if this diversification could be related to adaptation to ultramafic substrates and to Ni hyperaccumulation. We generated a well-resolved molecular phylogeny, including nearly all of the Neotropical and Caribbean Buxus taxa. To obtain robust divergence times we tested for the effects of different calibration scenarios, and we reconstructed ancestral areas and ancestral character states. Phylogenetic trees were examined for trait-independent shifts in diversification rates and we used multi-state models to test for state-dependent speciation and extinction rates. Storms could have contributed to Cuba acting as a species pump and to Buxus reaching other Caribbean islands and northern South America'. We found a Caribbean Buxus clade with Mexican ancestors, encompassing three major subclades, which started to radiate during the middle Miocene (13.25 Mya). Other Caribbean islands and northern South America were reached from ~3 Mya onwards. An evolutionary scenario is evident in which Buxus plants able to grow on ultramafic substrates by exaptation became ultramafic substrate endemics and evolved stepwise from Ni tolerance through Ni accumulation to Ni hyperaccumulation, which has triggered species diversification of Buxus in Cuba. Storms could have contributed to Cuba acting as a species pump and to Buxus reaching other Caribbean islands and northern South America'. © The Author(s) 2023. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Citation

Pedro A González Gutiérrez, Susy Fuentes-Bazan, Vanessa Di Vincenzo, Rosalina Berazaín-Iturralde, Thomas Borsch. The diversification of Caribbean Buxus in time and space: elevated speciation rates in lineages that accumulate nickel and spreading to other islands from Cuba in non-obligate ultramafic species. Annals of botany. 2023 Aug 25;131(7):1133-1147