Phylogeny and circumscription of Sapindaceae revisited: molecular sequence data, morphology and biogeography support recognition of a new family, Xanthoceraceae

Abstract

Background and aims -Recent studies have adopted a broad definition of Sapindaceae that includes taxa traditionally placed in Aceraceae and Hippocastanaceae, achieving monophyly but yielding a family difficult to characterize and for which no obvious morphological synapomorphy exists. This expanded circumscription was necessitated by the finding that the monotypic, temperate Asian genus Xanthoceras, historically placed in Sapindaceae tribe Harpullieae, is basal within the group. Here we seek to clarify the relationships of Xanthoceras based on phylogenetic analyses using a dataset encompassing nearly ¾ of sapindaceous genera, comparing the results with information from morphology and biogeography, in particular with respect to the other taxa placed in Harpullieae. We then re-examine the appropriateness of maintaining the current broad, morphologically heterogeneous definition of Sapindaceae and explore the advantages of an alternative family circumscription. Methods -Using 243 samples representing 104 of the 142 currently recognized genera of Sapindaceae s. lat. (including all in Harpullieae), sequence data were analyzed for nuclear (ITS) and plastid (matK, rpoB, trnD-trnT, trnK-matK, trnL-trnF and trnS-trnG) markers, adopting the methodology of a recent familywide study, performing single-gene and total evidence analyses based on maximum likelihood (ML) and maximum parsimony (MP) criteria, and applying heuristic searches developed for large datasets, viz. a new strategy implemented in RAxML (for ML) and the parsimony ratchet (for MP). Bootstrap analyses were performed for each method to test for congruence between markers. Key results -Our findings support earlier suggestions that Harpullieae are polyphyletic: Xanthoceras is confirmed as sister to all other sampled taxa of Sapindaceae s. lat.; the remaining members belong to three other clades within Sapindaceae s. lat., two of which correspond respectively to the groups traditionally treated as Aceraceae and Hippocastanaceae, together forming a clade sister to the largely tropical Sapindaceae s. str., which is monophyletic and morphologically coherent provided Xanthoceras is excluded. Conclusion -To overcome the difficulties of a broadly circumscribed Sapindaceae, we resurrect the historically recognized temperate families Aceraceae and Hippocastanaceae, and describe a new family, Xanthoceraceae, thus adopting a monophyletic and easily characterized circumscription of Sapindaceae nearly identical to that used for over a century.

Cardiospermum bahianum (Sapindaceae: Paullinieae), a New Species from Bahia, Brazil

“…Sapindus oligophyllus clearly groups (MLBP = 100) with Lepisanthes, an affiliation proposed by Xia and Gadek (2007) who transferred S. oligophyllus to Lepisanthes. Therefore, the anomalous position of this taxon within the Paullinia group by Buerki et al (2009Buerki et al ( , 2010Buerki et al ( , 2013) is due to the misidentification of their sample, which is likely a species of Allophylus.…”

“…Analyses of eight DNA sequence regions from the plastid and nuclear genomes by Buerki et al (2009Buerki et al ( , 2010Buerki et al ( , 2011 recovered a "Paullinia group" of genera assignable to the Paullinieae and Thouinieae. Following the conclusions suggested in Acevedo-Rodríguez (1993) and Buerki et al (2009), AcevedoRodríguez et al (2011) placed the genera of Thouinieae in a newly circumscribed Paullinieae, which encompassed 12 genera.…”

“…& Chun, proposed by Buerki et al (2009Buerki et al ( , 2010Buerki et al ( , 2011 as a member of their Paullinia group. Balsas was described to account for a species considered closely related to Paullinia, but which is distinguished by its exarillate seeds and hemi-tricolporate pollen grains.…”

Sapindaceae em um remanescente de Floresta Estacional Semidecidual no município de Engenheiro Paulo de Frontin, RJ, Brasil

“…Sapindaceae é uma família monofilética (Gadek et al 1996, Harrington et al 2005, Buerki et al 2010 e predominantemente distribuída nas regiões tropical e subtropical (Buerki et al 2010, AcevedoRodríguez et al 2011. No Brasil, ocorrem 28 gêneros e 418 espécies (Somner et al 2015).…”

Sapindaceae na Serra do Cipó, Minas Gerais, Brasil

“…Bibliografia básica: Acevedo-Rodríguez (1993), Acevedo-Rodríguez et al (2011), Barkley (1957, Buerki et al (2009Buerki et al ( , 2010, Croat (1976, , , Radlkofer (1892Radlkofer ( , 1931Radlkofer ( -1934, Reitz (1980), , Somner et al (2010).…”