Karyology, chorology and bioecology of the genus Limonium (Plumbaginaceae) in Sardinia

Abstract

The genus Limonium is very differentiated in Sardinia. Thirty‐eight prevalently endemic (76%) species are known at present. Most of them (21 species) are triploid with a basic number x = 9; some species are widely distributed and, because of their scarce morphological affinities, presumably ancient; others have a more or less restricted distribution area, are weakly differentiated and probably of recent origin. There is also a diploid group with 2n = 18, which occurs in coastal areas, represented generally by obliged allogamous species (14) with an incompatible pollen/stigma heteromorphic system sometimes associated with heterostyly. The diploids have developed coastal belt vicariant species, territorially associated with the system of triploids. Part of the triploids of recent origin is clearly derived from a process of allotriploidy, i.e. hybridisation between a diploid and a triploid living next to each other. In Corsica and Sardinia, due to scarcity of tetraploids, the genus Limonium is characterised by a high diploid/triploid ratio. The same is true, though less clearly, also in other Mediterranean territories. The coexistence of amphimictic diploids of gradual geographic differentiation with, in part, weakly differentiated apomictic triploids poses the taxonomic problem of the contemporaneous adoption of two distinct concepts of species.