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In many gynodioecious species, gender differences have been documented. Previous studies on populations of Lobelia spicata consistently documented hermaphrodites having larger corollas than females, but inconsistencies as to whether females had higher fruit set or not. In this study we expanded the data set on floral morphology, and to relate morphological differences to potential reproductive output we recorded stigma pollen loads and pollen tube growth to the ovary for both genders from four populations. Also, individuals were bagged to determine if and how much self-pollen deposition occurred on stigmas. Because this species is self-compatible but protandrous, it was thought unlikely to be able to self-fertilize through autogamy. Hermaphroditic flowers were larger than female flowers in four out of the six flower traits analyzed. Overall, hermaphroditic flowers had larger corollas and stigma–nectary distance, but female flowers had longer and wider stigmas and more ovules. Open-pollinated hermaphroditic flowers received more pollen grains on the stigma than female flowers. Positive correlations were found between floral morphological traits and stigma pollen load, but only for hermaphrodites. Pollen was found on the stigmas of all hermaphroditic bagged individuals and on a few female bagged individuals, though pollen tube growth was quite limited. Lastly, population differences were found. This study has identified several floral morphological traits and pollen grain/tube differences between genders and among populations for Lobelia spicata, supporting overall patterns identified in other gynodioecious species and adding a more detailed description of differences between the reproductive biology of each gender for this particular species. |
