Chromosome variation and species relationships in the scale-leaved triggerplants (Stylidium section Squamosae)

Abstract

Karyotypes for 15 of the 16 species in the scale-leaved triggerplants (Stylidium section Squamosae) are reported. Extensive changes in chromosome structure and number have occurred in association with the evolution of species in this section. Distribution patterns and ecological data demonstrate that in most cases speciation can also be associated with restriction to quite specific eco-geographic regions in the south-west of Western Australia. Parapatric or sympatric species which are known on morphological criteria to be very closely related generally have different chromosome numbers. Breeding system studies show that 10 of the 11 species investigated in the section have lethal factors which eliminate the products.of self pollination, the exception being S. sp. 1 in the Stylidium caricifolium species complex.