Integrative taxonomy of Ceratozamia mexicana Brongn. (Zamiaceae) complex
from a phylogeographic perspective
In recent years, there has been a growing interest in research on
Ceratozamia cycads, which has resulted in a significant increase in our
understanding of their diversity. However, species complexes that have
been tackled through integrative methodologies have exhibited a bias
towards morphology over genealogy. Thus, there arises the necessity to
reevaluate the Ceratozamia mexicana species complex using
phylogeographic tools. For this purpose, we have employed the
integrative taxonomic protocol Schlick-Steiner et al. (2010) put forth.
This protocol delineates species as testable hypotheses, incorporating
lines of evidence within a reproducible and falsifiable framework. The
evaluated data encompassed (i) phylogenetic and molecular variance
analyses, (ii) multivariate morphometric analyses, and (iii) analysis of
climatic niches. Out of the 196 individuals from 13 studied populations,
seven monophyletic groups were recovered. These groups were
substantiated by multivariate morphometric analysis, revealing
significant differences, and were further validated by niche divergence.
These results underscore a ‘whole agreement’ across the three
disciplines, thus providing robust support for acknowledging the species
as distinct lineages. The species delimited by these lineages,
encompassing phylogenetic, morphological, and environmental factors,
correspond to C. brevifrons, C. delucana, C. decumbens, C. mexicana, C.
moretti, C. tenuis, and a novel cryptic species, sister to the latter.
Finally, this genealogical characterization will offer utility in the
future for uncovering the genetic identity of the holotype of the type
species within the Ceratozamia genus.