Florivory and sex ratio in Annona dioica St. Hil. (Annonaceae) in the Pantanal at Nhecolândia, southwestern Brazil

Acta Botanica Brasilica

Hipólito Ferreira Paulino Neto²  Reinaldo Chaves Teixeira¹ 

[1] ,Universidade Estadual de Campinas Instituto de Biologia Campinas SP ,Brazil

关键词: Annona dioica;    Annonaceae;    Curculionidae;    florivory;    sex ratio;    Annona dioica;    Annonaceae;    Curculionidae;    florivoria;    razão sexual;   

DOI  :  10.1590/S0102-33062006000200015

来源: SciELO

【 摘 要 】

Annona dioica St. Hil. is a species that grows to approximately 2 m tall and is very widespread in the cerrados. Individual plants of this androdioecious species produce numerous hermaphroditic or male flowers, but few fruits. The aim of this study was to determine the sex ratio among the plants and to compare the frequency of herbivory between male and hermaphroditic flowers. The fieldwork was done by studying flowering plants in grasslands used as pasture for cattle at Fazenda Nhumirim. One hundred and forty-seven male plants and 71 hermaphroditic plants were examined and produced a total of 194 and 94 flowers, respectively, during the study period. The male:hermaphrodite sex ratio was 2.07:1, and was similar to the male:hermaphrodite flower ratio of 2.06:1. The frequency of florivory rate in hermaphrodites was significantly higher than in male flowers (33.0%, n = 31, and 25.7%, n = 50, respectively; G = 14.83; d.f. = 1; p < 0.001). The mean fresh weights of male and hermaphroditic flowers were significantly different (8.38 ± 2.40 g vs. 6.93 ± 2.68 g, respectively; 0 ± SEM; n = 50 each; t = 2.479; d.f. = 49; p = 0.017). These results indicate that the low fruit set in this species can be explained by the sex ratio, the greater herbivory of hermaphroditic flowers and the probable absence of pollinators.

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