A new insight into Serjania Mill. (Sapindaceae, Paullinieae) infrageneric classification: a cytogenetic approach

Abstract

Serjania (Sapindaceae, Paullinieae) comprises about 230 species, and currently two infrageneric classifications have been proposed but both are difficult to apply. This work tested which infrageneric classification fitted better in relation to cytogenetic traits added to the main morphological features used by the authors of the subgenus arrangements to gain an insight into the evolutionary karyotype relationships. In order to test the relationship between karyotypes and the systematics of this genus, the karyotypes of five species of Serjania belonging to five different sections (sensu Radlkofer) were described. Known karyological information on 26 species was used to complement the results. With these data, a cluster analysis was set up to test which infrageneric classification fitted better. In addition, a principal component analysis (PCA) was performed to examine the relevance of the traits in the subgenus classification. All the karyotypes analyzed (including new as well as previous records) had 2n = 24 chromosomes, and the karyotypes were asymmetrical: submetacentric and metacentric chromosomes were common, whereas telocentric chromosomes were rare. The PCA revealed seven principal components, the first two explained 52 % of the total variation, and the last ones were related to all the karyotypic features studied. The phenogram obtained reflected a scarce fitting into both infrageneric classifications, with only 3 sections of the 12 proposed by Radlkofer and two of the six sections proposed by Acevedo-Rodriguez being represented. Finally, regarding karyotype evolution, the constancy of chromosome number and the variation in the length of the complement suggest that structural chromosome changes would have played a leading role.