Phylogenetics of Serjania (Sapindaceae-Paullinieae), with emphasis on fruit evolution and the description of a new species from Michoacán, Mexico

Abstract

Serjania is among the largest Neotropical genera of Sapindaceae and comprises ∼240 species. Traditionally, the genus has been defined by its schizocarpic fruits separating into three distally winged mericarps. However, recent phylogenetic studies have revealed that fruit type is not consistent within the genus and that it also includes a few species having capsular fruits that were previously placed in other genera. A phylogenetic analysis is presented based on nuclear ITS and chloroplast trnL-F sequences. The ingroup consisted of 48 species broadly sampled from across the geographic range and taxonomic spectrum of Serjania and focusing on species with atypical fruits. An ancestral character state reconstruction of fruit type was performed and demonstrated that the ancestral fruit type of the genus is strongly supported to be a schizocarp, but there are at least five independent derivations to capsular fruits and at least one transition back from capsules to schizocarps. Also, transitions from winged to wingless mericarps have occurred at least twice. Infrageneric classification is problematic and all of the sections that were represented by more than one species come out as poly- or paraphyletic. Our limited sample of taxa precludes the possibility of a new classification at present and a broader phylogenetic sample of the genus will be needed to understand relationships and determine which lineages warrant formal recognition. In addition to the phylogenetic study, Serjania frutescens, a new capsular-fruited species from Michoacán, Mexico, is described, illustrated, and compared with its putative closest relatives. A key is provided to differentiate this species from other Mexican Serjania with capsular fruits, and new synonymies and lectotypifications associated with capsular-fruited Serjania tortuosa and S. sonorensis are established. Phylogenetic results suggest that these two are cryptic species and at least superficially indistinguishable by morphology.

Key words:

• Balsas depression
• capsular fruit
• cryptic species
• ITS
• Mexican vascular flora
• molecular phylogeny
• trnL-F

Acknowledgements

We thank L. Simón for preparing the excellent illustration, W. Medina and G. Pieszko for digitalizing the images, R. Salas for help with the IUCN conservation status. Financial support was provided by a grant from the Myndel Botanical Foundation, for which we are profoundly grateful and by the National Council of Scientific and Technical Research, Argentina. We thank the following herbaria for access to their collections: A, ARIZ, BCMEX, BM, CTES, F, G, GH, K, M, MEXU, MO, NY, QMEX, RSA, SD, UC, US, and WU. Molecular work was done at the California Botanic Garden, and their assistance is greatly appreciated. The NSF grant DEB‐1557059 supported the third author’s postdoctoral position. The second author is also grateful to Rosalinda Medina Lemos for assistance during her stay in Mexico. Márgaro Lara Camacho and Yocupitzia Ramírez Amezcua assisted with fieldwork, and Jon Rebman provided material from Baja California, Mexico; Jaime Jiménez kindly supplied leaf material and the photos of Serjania guerrerensis, and Tom Wendt sent leaf material of Serjania dissecta. Damián Piña prepared the photo collages, and Martín Abraham Ornelas prepared the distribution map.

Disclosure statement

There are no potential conflicts of interest.

Supplemental material

Supplemental material for this article can be accessed here: https://doi.org/10.1080/14772000.2022.2030425.

Associate Editor: Dr Mark Carine