The chromosomal evolution and analyses of Turkish Cousinia species

Abstract

: In this study, Turkish Cousinia species were examined in point of chromosome number and morphology. To our knowledge, this work is the first comprehensive chromosomal study regarding Turkish Cousinia as a whole, especially for endemics. As consistent with previous reports, the chromosome numbers are mostly 2 n = 26 and have been determined also as 2 n = 24 for only the members of Cynaroideae and Sphaerocephalae sections. An interesting result of this paper is that there is not any polyploid species in this taxonomic group and all of them are diploids. Concerning the chromosome evolution of the Cousinia species, we concluded that merely dysploidy is effective within the genus and evolutionally a unipolar reduction goes on in the basic chromosome number in speciation (from 13 to 12). In terms of general chromosomal information, the chromosomes of the genus consist of metacentric and submetacentric types and they could be categorized in small category according to Lima De Faria classification (0.67–3.43). According to chromosomal indices used in this paper, while most species have symmetrical chromosomes, fewer have asymmetrical ones. From this point, it could be said that Cousinia stapfiana could be assessed as the most evolved taxa in karyomorphology according to the average of all indexes used in here. Besides, Cousinia bicolor , Cousinia birandiana , and Cousinia sintenisii are species having the most primitive chromosome within the genus.