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

Abstract

RESUMO -(Florivoria e Razão Sexual em Annona dioica St. Hil. (Annonaceae) no Pantanal da Nhecolândia, Brazil). Annona dioica é uma espécie arbustiva de até dois metros de altura, amplamente distribuída nos cerrados. Esta espécie é conhecida por oferecer muitas flores, mas produzir poucos frutos. Enquadra-se como androdióica, possuindo indivíduos machos e hermafroditas na população. O objetivo deste estudo foi registrar a razão sexual e comparar a taxa de florivoria entre flores masculinas e hermafroditas. A coleta de dados ocorreu em campos de pastagem da Fazenda Nhumirim, consistindo na observação de arbustos floridos. Foram registrados 147 indivíduos masculinos e 71 hermafroditas, os quais apresentavam um total de 194 e 94 flores durante o período de estudo, respectivamente. A razão sexual observada foi de 2,07 indivíduos masculinos para cada hermafrodita, bem como 2,06 flores masculinas para cada flor hermafrodita. A taxa de florivoria foi significativamente maior em flores hermafroditas que em masculinas, com 33,0% (n = 31) e 25,7% (n = 50), respectivamente (G = 14,83; 1gl; p < 0,001). A média do peso fresco de 50 flores de ambos os sexos foi de 8,38 ± 2,40 g (0 ± EP; n = 50) para flores masculinas e de 6,93 ± 2,68 g (0 ± EP; n = 50) para hermafroditas, sendo significativamente diferentes (t = 2,479; df = 49; p = 0.017). Portanto, o baixo número de frutos encontrados nesta espécie pode ser explicado pela razão sexual, maior herbivoria em flores hermafroditas e provavelmente, pela ausência de polinizadores. Palavras-chave:Annona dioica, Annonaceae, Curculionidae, florivoria, razão sexual St. Hil. (Annonaceae) in the Pantanal at Nhecolândia, southwestern Brazil). 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. ABSTRACT -(Florivory and sex ratio in Annona ...

Among‐species variation in flower size determines florivory in the largest tropical wetland

“…Our results indicated that corolla was the most attacked flower part by florivores (96% of the cases), followed by reproductive organs (34%) and calyx (17%). In a previous study in the Pantanal, damage caused by florivorous beetles was also greater on the petals than on the reproductive organs of Annona dioica (58% vs. 42%, respectively; Neto and Teixeira 2006). In a temperate forest in Central Mexico, florivores preferentially attacked corollas (69%) of Solanum rostratum (Vega‐Polanco et al, 2020).…”

Effects of Florivory on Floral Visitors and Reproductive Success of Sagittaria lancifolia (Alismataceae) in a Mexican Wetland

“…Although there is variation in the incidence and intensity of florivory between environments and between terrestrial and aquatic species, no studies have evaluated these variables considering plant species with female and male flowers (dioecious or monoecious). Most studies have focused on species that have hermaphroditic flowers [ 2 ], and a few studies on gynodioecious species or plants with flowers of separate sexes (dioecious or monoecious) [ 6 , 9 , 40 ]. This suggests that future studies should focus on plant species with other sexual expressions, allowing us to identify patterns and differences among them.…”