Chromosomal studies and evolution in Sapindaceae

Abstract

Summary Chromosome numbers and chromosomal ideograms were obtained for the Sapindaceae forest climbers Serjania caracasana, S. fuscifolia, S. meridionalis and Urvillea laevis (tribe Paulliniae) and the cerrado shrub Talisia obovata (tribe Melicocceae). Cytological preparations were obtained by Giemsa technique. Serjania and Urvillea showed 2n = 24, with chromosome length varying from 1.2 to 6.3I1m, large in relation to other Sapindaceae genera. Most chromosomes were submetacentric in Serjania and met acentric in Urvillea. The literature shows no interspecific variation of chromosome number in the genus Serjania, but it did occur in Urvillea. Talisia obovata showed 2n = 32, with small chromosomes (1.0 to 2.1I1m). A revision of chromosome numbers in 40 genera and 122 species showed great variation between species of Sapindaceae (2n= 14 to 2n=96). There is a small overlap of chromosome number between climbers and shrubs/trees: 74% of climbers so far studied have 2n=20, 22 and 24, and 82% of non-climbers have 2n=28, 30 and 32. The numeric variation of chromosomes indicates that the disploidy may have played a major role in the evolution of the whole family of Sapindaceae. Although the data in literature were not enough for a deep analysis we noted a tendency between smaller chromosome length and greater chromosome number. We propose that the derivation of climber habit (tribe Paullinieae) from non-climber involved mostly reduction in chromosome number and increase in absolute chromosome length.