A CLADISTIC-ANALYSIS OF THE SUBTRIBE SICYINAE (CUCURBITACEAE)

The subtribe Sicyinae includes six genera (Microsechium, Parasicyos, S echiopsis, Sechium, Sicyos, and Sicyosperma). In this paper, monophyly of this subtribe and phylcgenetic relationships among its genera are explored by means of a cladistic analysis. Twenty nine morphological a nd palynological characters, and 22 taxa representative of all genera of subtribe Sicyinae were included in the analysis, The taxa used as o utgroup were the genera Cyclantheri and Echinopepon, two members of th e subtribe Cyclantherinae, the sister group of Sicyinae according to t he current classification of the family Cucurbitaceae. Two equally mos t parsimonious cladograms (L = 78, CI = 0.615, RI = 0.764, HI = 0.564) were obtained. In both cladograms, the members of the subtribe Sicyin ae were clustered as a monophyletic group. However, the monophyly of M icrosechium, Parasicyos and Sicyos was not clearly supported, and thei r relationships could not be defined. In contrast, Sechiopsis and Sech ium formed a monophyletic group supported by the presence of defined f loral nectaries at the base of the receptacle. The results confirm the strong relationships between these two genera suggested in previous p apers. However, while the monophyly of Sechiopsis was clearly supporte d by the presence of winged fruits, no synapomorphy was found either f or the whole genus Sechium or for its two currently accepted sections. Nevertheless, the results also revealed that there is not any evidenc e to place the members of Sechium in three different genera (Sechium, Frantzia and Polakowskia) as has been proposed by other authors.