The measure and mismeasure of reciprocity in heterostylous flowers

What is it about?

Darwin was among the first to study heterostylous flowers; these occur as two or more complementary morphs on different plants. Plants of one morph can usually only be fertilized by pollen from the opposite (or complementary) morph. The reciprocity index is meant to capture deviation from the perfect correspondence in position of anthers and stigmas of complementary morphs, thus measuring the departure from optimal morphology in terms of efficiency of pollination with compatible pollen. (The heights of the anthers and stigmas are assumed to determine the location of pollen placement on, and stigma contact with, the pollinator, respectively.) Previous indices have lacked a theoretical basis and not been mathematically justified in any explicit fashion. Here we propose and index based on adaptive accuracy theory. Our approach is computationally simple and has explicit connections to models of reproductive fitness.

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