Abstract
The conservation and sustainable management of Annona coriacea requires knowledge of its floral and reproductive biology, and of its main pollinators and their life cycles. In this work, we analyzed these aspects in detail. Floral biology was assessed by observing flowers from the beginning of anthesis to senescence. The visiting hours and behavior of floral visitors in the floral chamber were recorded, as were the sites of oviposition. Excavations were undertaken around specimens of A. coriacea to determine the location of immature pollinators. Anthesis was nocturnal, starting at sunset, and lasted for 52–56 h. The flowers were bisexual, protogynous and emitted a strong scent similar to the plant´s own ripe fruit. There was pronounced synchrony among all floral events (the period and duration of stigmatic receptivity, release of odor, pollen release and drooping flowers) in different individuals, but no synchrony in the same individuals. All of the flowers monitored were visited by beetle species of the genera Cyclocephala and Arriguttia. Beetles arrived at the flowers with their bodies covered in pollen and these pollen grains were transferred to the stigmata while foraging on nutritious tissues at the base of the petals. With dehiscence of the stamens and retention within the floral chamber, the bodies of the floral visitors were again covered with pollen which they carried to newly opened flowers, thus promoting the cycle of pollination. After leaving the flowers, female beetles often excavated holes in the soil to lay eggs. Larvae were found between the leaf litter and the first layer of soil under specimens of A. coriacea. Cyclocephala beetles were the main pollinators of A. coriacea, but Arriguttia brevissima was also considered a pollinator and is the first species of this genus to be observed in Annonaceae flowers. Annona coriacea was found to be self-compatible with a low reproductive efficiency in the area studied. The results of this investigation provide ecological data that should contribute to the conservation and economic exploitation of A. coriacea.
Highlights
The pollination ecology allows the understanding of the structure of natural plant communities [1,2,3,4] and provides information about the shape of the flowers, which makes it possible to characterize the mechanisms of pollination and adaptation of visitors to the flower [5]
The commencement of anthesis in A. coriacea was characterized by a slight separation between the apices of the outer petals, when it is possible to see part of the inner petals
At the beginning of the observations, the flower buds were in advanced stages of development, and kept the outer petals joined to each other (Fig 1A)
Summary
The pollination ecology allows the understanding of the structure of natural plant communities [1,2,3,4] and provides information about the shape of the flowers, which makes it possible to characterize the mechanisms of pollination and adaptation of visitors to the flower [5]. There is flowering and temperature rise in anthesis, accompanied by the production of odor [2, 19,20,21,22,23,24,25,26,27] with consequent volatilization and attraction of pollinating beetles These penetrate the flower forcing entry through the petals, and remain inside for a period ranging from hours to a few days, feeding on pollen and/or nutritional tissues of the petals, at the same time, using the flower as a place of shelter and a copula. This whole set of strategies, including morphological and physiological adaptations that Annona flowers have for visitors, gives them greater chances of pollination success [2, 20, 21, 23]
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