Patterns of variation in distylous traits and reproductive consequences in Erythroxylum species and populations

Raphael Matias, Rocio Perez-Barrales, Hélder Consolaro

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Premise of the study: Distylous species possess two floral morphs with reciprocal positioning of stigmas and anthers that is hypothesized to promote disassortative pollination. Theoretical models predict equal morph frequencies, but many populations depart from the expected 1:1 ratio, a pattern that often correlates with asymmetric mating between morphs and/or presence of weak incompatibility system. Variation in reciprocity can also affect the likelihood of disassortative pollination, and hence reproductive fitness.

Methods: We described variation in incompatibility systems and morph ratio in four Erythroxylum species to test if greater deviations from 1:1 ratios occur in populations of self-compatible species. We used adaptive inaccuracy and described upper and lower organ reciprocity in species and populations, and assessed the relationship of reciprocity to population means and coefficients of variation for fruit set to test if reciprocity could predict female reproductive success.

Key results: Morphs occurred in 1:1 ratios in most populations of three Erythroxylum species with distylous self-incompatibility. In self-compatible E. campestre populations showed an excess of the long-styled morph, the short-styled morph, or were monomorphic for the short-styled morph. We detected deviations from reciprocity, with total inaccuracy ranging between 9.39% and 42.94%, and inaccuracy values were lowest in low organs. Across populations, we found a positive relationship between inaccuracy and the coefficient of variation of fruit set.

Conclusions: Erythroxylum species showed variation in the distylous syndrome, with changes in the incompatibility system that corresponded with deviations from 1:1 morph ratio, and variation in reciprocity that correlated with variation in female reproductive fitness.
Original languageEnglish
Pages (from-to)910-922
JournalAmerican Journal of Botany
Issue number6
Early online date28 May 2020
Publication statusPublished - Jun 2020


  • breeding systems
  • Cerrado
  • disassortative mating
  • Erythroxylaceae
  • heterostyly
  • isoplethy
  • monomorphism
  • morph bias
  • reciprocal herkogamy
  • sex polymorphism


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