Taxonomic revision of the genus Vincetoxicum wolf (Apocynaceae-Asclepiadoideae) in Turkey

In this study, all Turkish Vincetoxicum Wolf (Apocynaceae) taxa were investigated by means of morphological, anatomical, palynological, cytological and molecular features in detail for the first time. The examined taxa were also evaluated by numerical and phylogenetic analyses and relationships amongst taxa were determined in terms of the identified characteristics. In morphological studies, a comprehensive diagnostic key for Turkish Vincetoxicum taxa and amended descriptions of each examined taxon including detailed morphological photographs and drawings, habitat features, distribution maps and threat categories were presented. Indumentum of stem, leaf and fruit, length of peduncle, color, shape and indumentum of corolla, shape of corona and anther were found to be important morphological characteristics in explaining relationships among the examined taxa. In addition, threat categories of endemic taxa to Turkey were re-evaluated as LC (V. fuscatum Rchb.f. subsp. boissieri (Kusnezov) Browicz) and VU (V. parviflorum Decne.). Anatomical observations indicated that mesophyll tissue and stomata features are taxonomically important characteristics. It was determined that the examined Vincetoxicum taxa have 5 pollinaria; corpusculum is ovate or oblong in shape, pollinium is elliptical, clavate, ovate or obovate in shape with a rugulate or gemmate surface. It was observed that periclinal walls on the seed surface exhibit ruminate/smooth or verrucose/granulate ornamentation. The chromosome number of the investigated Vincetoxicum taxa was found to be 2n=22 (diploid) or 2n=44 (tetraploid). Molecular analyses showed that ITS sequences with the lenght of 617-618 bp provide important contributions in distinguishing the examined taxa while trnT-trnL sequences, 804 bp in lenght, are not taxonomically distinctive.