Turnera hermannioides

Turnera hermannioides is a distylous, diploid perennial restricted to open, sandy sites in northeastern Brazil. Four populations sampled in Sergipe contained equal proportions of long- and short-styled plants. The style and stamen dimorphism in floral morphs is associated with differences in pollen size and pollen production. In contrast, flower size, ovule number, and seed fertility of the morphs are not significantly different. A controlled pollination program demonstrated that individuals of T. hermannioides possess a self- and intra-morph incompatibility system. The only pollinations resulting in significant seed production were between the floral morphs. Populations of T. hermannioides grow intermingled with T. ulmifolia, a widespread polymorphic complex containing forms that resemble T. hermannioides. A crossing program between T. hermannioides and diploid and tetraploid varieties of T. ulmifolia revealed barriers to hybridization particularly in crosses at the diploid level. It is concluded that T. hermannioides is a restricted diploid species that is reproductively isolated from T. ulmifolia.