Experimental insights on the function of ancillary pollen and stigma polymorphisms in plants with heteromorphic incompatibility

Most heterostylous plants possess a reciprocal arrangement of stigmas and anthers (reciprocal herkogamy), heteromorphic self-incompatibility and ancillary polymorphisms of pollen and stigmas. The topographical complementarity hypothesis proposes that ancillary polymorphisms function in the rejection of incompatible pollen thus promoting disassortative pollination. Here, we test this hypothesis by investigating patterns of pollen transfer and capture in populations of dimorphic Armeria maritima and A. pubigera and distylous Limonium vulgare (Plumbaginaceae), and by studying pollen adherence and germination patterns in A. maritima following controlled hand-pollinations. Armeria lacks reciprocal herkogamy allowing the evaluation of the extent to which ancillary polymorphisms affect the composition of pollen loads. We compared the amounts of compatible and incompatible pollen on stigmas in natural populations and calculated the proficiencies of pollen transfer for each mating type. We detec...