Integrative taxonomy supports the recognition of four taxa in the Notholaena trichomanoides complex (Pteridaceae) in Cuba

Abstract

Abstract With nearly 40 species, the fern genus Notholaena has its evolutionary centre in the deserts of Mexico and the southwestern United States. Previous studies have focused on assessing the monophyly of the genus and the patterns of farina evolution, but little attention has been given to species complexes. Notholaena trichomanoides s.l. is endemic to the Greater Antilles, growing on all four islands. Although at least two varieties have been described, many authors have hesitated to recognize them and have treated this complex as only one taxon. A multivariate morphometric analysis including 80 representatives of N. trichomanoides from the Greater Antilles allowed us to recognize four morphological groups. Twenty individuals from seven populations representing all these morphological groups were sampled in Cuba. Differences among the four lineages were supported by molecular phylogenetics (including three plastid and two nuclear markers), molecular species delimitation, morphology and geological preferences. Ploidy levels inferred using spore sizes calibrated by chromosome counts revealed the existence of diploid and tetraploid lineages within the complex. Time-calibrated trees suggest that the divergence of the common ancestral populations of N. trichomanoides s.l. and those of its sister taxon N. ekmanii occurred between the Middle Miocene and the Miocene–Pliocene boundary followed by a recent diversification within the complex, ranging between the Middle Pliocene and the Middle Pleistocene.