Pollen morphology of Dioscorea (Dioscoreaceae) from the Atlantic Forest in southeast Brazil (Sao Paulo) with a contribution to the systematics of Neotropical species

Dioscorea is a highly diverse genus in Brazil, particularly the south-eastern region, and most especially in the Atlantic Forest. Recent phylogenetic studies have helped clarify the intricate subgeneric classification of the genus, although some species remain to be sampled, and further studies are necessary to ascertain their systematic placement in the genus. Here, a palynological description of nine species occurring in a patch of Atlantic Forest, in the State of Sao Paulo, is provided. Three of these have not yet been sampled in molecular studies. The pollen of D. tauriglossum had never been characterised before. Dioscorea pollen are spheroidal to ellipsoidal, small to medium in size (the larger dimensions in D. dodecaneura and the smaller in D. amaranthoides), with disulculate aperture. The pollen wall ornamentation contributed to the segregation of two species - psilate-perforate (D. altissima, syn. D. choncrocarpa) and rugulate-perforate (D. monadelpha), as well as the separation of the other seven species in two groups - microreticulate (D. dodecaneura, D. multiflora, D. tauriglossum), and striate (D. amaranthoides, D. laxiflora, D. olfersiana, D. trilinguis). Systematic implications of the palynological variation found are discussed under the light of recent molecular phylogenetic studies.