Abstract

CANCHE-COLLI, César  and  CANTO, Azucena. Distylous traits in Cordia dodecandra and Cordia sebestena (Boraginaceae) from the Yucatan Peninsula. Bot. sci [online]. 2014, vol.92, n.2, pp.289-297. ISSN 2007-4476.

Distyly is a genetically-controlled polymorphism with two floral morphs exhibiting spatial, reciprocal separation between stigmas and anthers; one morph presents styles above anthers, and the other styles below anthers. Distyly is usually linked to a self-incompatibility system that prevents self-pollination and crosses between plants of the same morph, thereby ensuring symmetrical mating and equal morph ratios within populations. This study is the first description of distylous traits in the tropical tree species Cordia dodecandra and C. sebestena from the Yucatan Peninsula. Principal components analysis of flower morphological traits identified segregation into two groups with characteristically distylous morphology. Estimation of reciprocal herkogamy using indices showed almost perfect reciprocity in the distance between long and short sexual organs in the two flower morphs of both species. Reciprocity between organs was lower in C. dodecandra, suggesting less accuracy in pollen transference between morphs. Self-incompatibility was observed for C. dodecandra, but could not be confirmed for C. sebestena. However, a 1:1 floral morph ratio within the sampled C. sebestena populations suggests the existence of a distylous, self-incompatibility system in this species. Morph distribution in C. dodecandra did not follow a typically distylous distribution, suggesting a disruption in population processes such as seed dispersion and seedling establishment in this species. The reported data confirm the existence of the distyly syndrome in the two Cordia species.

Keywords : distyly; morph ratio; reciprocal herkogamy; self-incompatibility.

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