Chromosomal evolution in Mediterranean species of Ophrys sect. Pseudophrys (Orchidaceae): An analysis of karyotypes and polyploidy

In an effort to clarify the patterns of chromosome evolution in Ophrys sect. Pseudophrys (Orchidaceae), chromosome counts were made of 18 O. sect. Pseudophrys taxa from the central-western Mediterranean Basin (Iberian Peninsula and North Africa). The present results provide, for the first time, the chromosome numbers of O. algarvensis, O. arnoldii, O. bilunulata and O. dianica; four other taxa (O. atlantica, O. lupercalis, O. fusca, O. sicula) yielded chromosome numbers not previously reported for the Iberian Peninsula. The results support the idea that the basic plesiomorphic number of Ophrys is x = 18, with 2n = 36 in most species. About 40% of the specimens were polyploids. Karyomorphological data do not support classification of the investigated species into groups. However, the data reveal some geographical differentiation and suggest a possible direction of chromosomal evolution in Ophrys sect. Pseudophrys.