Species diversity patterns within a big neotropical genus: recent radiations in Philodendron (Araceae) in Central...

Philodendron is one of the largest genera in the Neotropics with well over 600 species in three subgenera (Meconostigma, Philodendron and Pteromischum). Following an early Oligocene origin, it was considered to have colonized Central America only late, in the Pliocene. However, molecular phylogenetic trees so far were short in species from Central America, which is now recognized as the second center of diversity. We aimed at elucidating the evolutionary origin of Philodendron diversity in this area, exploring relationships between Central and South American species, and assessing the role of the Isthmus of Panama in their diversification.

Fieldwork was conducted across Mexico, Costa Rica, Panama, and Colombia. To maximize coverage of tree space, 319 new samples were added to an existing alignment of three plastid regions (petD, rpl16, and trnK/matK). Phylogenetic trees from a total of 302 taxa were inferred using Maximum Likelihood approaches. Divergence times were estimated with BEAST, and diversification dynamics were assessed with BAMM.

Philodendron and its three subgenera were monophyletic, with the largest subgenus Philodendron comprising 15 major lineages. Two significant diversification rate shifts within subgenus Philodendron associated with the uplift of the Northern Andes and the emergence of montane cloud forests in southern Central America were observed. Most of the diversification events of Central American lineages apparently aligns with the last phases of the Isthmus and the formation of Talamanca mountain range. South American ancestors highlight the role of the Isthmus as a biogeographic corridor that enabled migrations of Philodendron into Central America.

The diversification of Philodendron in Central America aligns with major geological events and the emergence of novel habitats. Compared to previous studies, our findings highlight the importance of a geographically and taxonomically comprehensive sampling for accurately reconstructing the evolutionary history of large plant genera.