MORALES Carolina Laura
congresos y reuniones científicas
Functional significance of sterile flowers in Muscari comosun
Palma de Mallorca, España
Simposio; The Evolutionary Ecology of Plant Animal Interactions-From Genes to Communities; 2008
Institución organizadora:
Asociacion Española de Ecología Terrestre
The evolution of inflorescence structures has been a major topic in the disciplines of floral and reproductive biology. Flowers represent the basic reproductive structure of angiosperms. Therefore, the evolution of sterile or non-fertile flowers in different lineages has been always challenging. Among the various hypothesis that have been constructed to explain the maintenance of sterile flowers in inflorescences, the hypothesis that sterile flowers enhance the attractiveness at the inflorescence level, increasing the chance of pollination of fertile flowers within the inflorescence.                 We tested this hypothesis in the perennial herb Muscari comosum (Hyacinthaceae). This plant species bears a single erect inflorescence, composed by fertile greenish flowers at the base, and violet-bluish sterile flowers at the top. Sterile flowers do not produce nectar, and apparently they do not produce any perceived odor.                     In a large M. comosum population (>200 individuals) located in the Salbufera Natural Reserve (Mallorca, Spain), we compared visitation frequency, fruit set and seed set in fertile flowers of inflorescences with sterile flowers (control), and inflorescences without sterile flowers (removal). In addition, we evaluated the influence of sterile flowers on fertile flowers pollination above the individual level, by relating the visitation frequency, seed set and fruit set of fertile flowers in removal treatments with the distance to the nearest inflorescence bearing sterile flowers, and with the density of inflorescences with sterile flowers at a small spatial scale (flowering patch). Finally we hand-pollinated flowers with pollen of the same individual (self-pollination), or with pollen of other individuals (cross-pollination) in order to know the level of self-compatibility. Other flowers were isolated from pollinators to evaluate the level of autogamous self-pollination, to estimate the degree of dependence on pollinators for reproduction.                 Muscari comosum main flower visitor was a solitary bee of the genus Anthophora, who visited flowers for nectar and seems to be an effective pollinator. Flower visitor behavior was influenced by the presence of sterile flowers. The presence of sterile flowers significantly increased the number of bees approaching the inflorescence and the flower visitation rate. As a consequence, fertile flowers in control treatment set more fruits than flowers in removal treatment. The attraction of sterile flowers to flower visitors was beyond the individual level, influencing the chances of neighboring flowers of removal treatment of receiving a visit. Flower visitors were attracted to mixed patches with control and removal inflorescences, by inflorescences with sterile flowers, which had more chances to receive the first visit in a foraging bout than inflorescences without sterile flowers. Hand self- and cross-pollination suggest that this species is highly self-incompatible and autogamy is very low.  Thus, fruit set relays mostly on Anthophora pollination.                 This study demonstrates that no fertile flowers might play a key role in the pollination success of fertile flowers at the inflorescence level, due to influencing flower visitor attraction both at the individual and flowering patch level.  The lack of bright, bee attractive color in fertile flowers in this species, seems consistent with the hypothesis that at the individual level, flower visitor attraction relays on sterile flowers. (Modalidad: poster)