Chromosome numbers and their evolutionary meaning in the Sapindales order: an overview

Sapindales consists of six larger families (Anacardiaceae, Burseraceae, Meliaceae, Rutaceae, Sapindaceae, and Simaroubaceae), and three smaller ones (Biebersteiniaceae, Kirkiaceae, and Nitrariaceae). It is monophyletic, but there are controversies in inter- and intra-family relations and no consensus regarding the basic chromosome number of the order and its families. We aim to detect the level of knowledge about chromosome numbers and discuss the evolution in Sapindales. We searched the literature for the available chromosome numbers, accounting for data for 214 genera and 805 species, corresponding to only about 46% of the genera and 15% of the species. Globally, among the six largest families, we observed the highest percentages of species with chromosome counts in Rutaceae (18%) and Sapindaceae (15.5%), contrasting with Burseraceae (3.5%). Chromosome numbers ranged from 2n = 10 in Biebersteiniaceae species to 2n = 360 in Trichilia dregeana Sond. (Meliaceae). We found a great diversity of chromosome numbers in each family, especially in Rutaceae, Sapindaceae, and Meliaceae. A low percentage of species of Sapindales of the Brazilian flora have their chromosome numbers known, mainly in Burseraceae (2.6%) and Meliaceae (14.9%). We confirm the importance of numerical chromosome changes in the diversification of families and genera. Polyploidy was very important in the origin of large families and later in their diversification, especially in Meliaceae and Rutaceae. Dysploidy is very frequent in the diversification of the large families. We discussed the basic chromosome numbers (x) for Sapindales and its families, based on the literature. Inconclusive results on x occur in Meliaceae and Simaroubaceae.