Reproductive success of four species of Eugenia L. (Myrtaceae)

Abstract

RESUMO -(Successo reprodutivo de quatro espécies de Eugenia L. (Myrtaceae)). Eugenia uniflora, E. punicifolia, E. neonitida e E. rotundifolia são espécies perenes, geralmente de porte arbustivo, que ocorrem na restinga do Parque Municipal Natural de Grumari, região oeste do Município do Rio de Janeiro, Brasil. Possuem flores-pólen do tipo Papaver, hermafroditas, polistêmones e polinizadas por abelhas. O sistema reprodutivo de cada espécie foi avaliado e os resultados mostraram que apenas E. uniflora e E. punicifolia são auto-compatíveis. De cada espécie foi avaliado o sistema de reprodução, as taxas fruto/flor, semente/óvulo e semente/fruto, além das taxas de predação de frutos e sementes e identificação dos seus agentes predadores. Com estes dados foram obtidos a taxa de fecundidade e o sucesso reprodutivo total de cada espécie. O sucesso reprodutivo total das quatro espécies foi muito baixo. Assim, para que no final do processo reprodutivo houvesse uma única semente viável e livre do ataque de herbívoros foi necessária a produção de 312,5 flores de E. uniflora, 9.090,9 de E. neonitida, 11.111,1 de E. punicifolia e 19.230,8 de E. rotundifolia. Em síntese, o sucesso reprodutivo total nas quatro espécies foi influenciado pelo sistema reprodutivo, pela razão semente/óvulo e, principalmente, pelas elevadas taxas de predação de frutos e sementes. A floração em massa destas espécies pode minimizar sua baixa eficiência reprodutiva, garantindo assim, a manutenção de sua dinâmica populacional. Palavras-chave:Eugenia, herbivoria de sementes, Myrtaceae, sistema de reprodução, sucesso reprodutivo ABSTRACT -(Reproductive success of four species of Eugenia L. (Myrtaceae)). Eugenia uniflora, E. punicifolia, E. neonitida and E. rotundifolia are perennial species, usually shrubs, which occur in the restinga of the Grumari Natural Municipal Park, in western Rio de Janeiro, Brazil. They have Papaver-type pollen-flowers that are hermaphrodite, polystemonous and pollinated mainly by bees. An assessment of the breeding systems showed that only E. uniflora and E. punicifolia are self-compatible. The fruit/flower, seed/ovule and seed/fruit ratios were calculated for each species. Fruit and seed predators were identified and predation rates were estimated. Total reproductive success for each species in the restinga was extremely low. In order to have one viable seed free from herbivore attack at the end of the reproductive process, the species would need to produce 312.5 E. uniflora, 9090.9 E. neonitida, 11111.1 E. punicifolia and 19230.8 E. rotundifolia flowers. In short, the reproductive success of the four species is affected by pollination efficiency, low seed/ ovule ratios and mainly, high predation rates. Mass flowering strategy in these species can minimize low reproductive efficiency, thus ensuring the maintenance of population dynamics.

The development of seedlings from fragments of monoembryonic seeds as an important survival strategy for Eugenia (Myrtaceae) tree species

“…These authors considered that any strategy for conservation and management must assure the preservation of several populations along the Atlantic coast, to maintain the majority of the intraspecific level of diversity. Additionally, Silva and Pinheiro (2009) found extremely low values for the total reproductive success for four Brazilian species of Eugenia with high frequencies of seed predation. Our data point out the importance of the regenerative capacity of each Eugenia seed when one considers the evolutionary investment in the intrapopulation variability and the high frequency of predation of these seeds.…”

“…E. cerasiflora seeds were intensely attacked by insect larvae. In fact, intense predation has also been verified for other Eugenia species, mainly due to the larval development of Coleoptera inside the seeds and fruits and, in Eugenia uniflora, by Tephritidae (Diptera) and Eurytidae (Hymenoptera) larvae (Silva and Pinheiro 2009). In the present study, although only small parts of these seeds were present due to the predation, they were able to germinate and produce normal seedlings, making it evident that originally they have a surplus of nutrient reserves.…”

“…Similar results were obtained by Masetto et al (2007) with infested seeds of Eugenia pleurantha that showed no germination. A failure to germinate due to predation was also assumed by Silva and Pinheiro (2009) for seeds of E. uniflora, E. neonitida, E. punicifolia and E. rotundifolia.…”

“…Therefore, this phenomenon could be related to the strategy developed by these species of investing more energy in seeds with qualities that favor their establishment and seedling survival than in those with qualities that favor their dispersal. According to Fenner (1985), this strategy is characteristic of plants inhabiting stable environments, as described by Silva and Pinheiro (2009) for E. uniflora, E. neonitida, E. rotundifolia and E. punicifolia, which displayed fruits containing few seeds with larger masses. This behavior should be considered for the development of species conservation strategies.…”

“…Moreover, various insects use seeds as their main food resources (Nakagawa et al 2003 and references therein), but seed predation can be a significant limiting factor for reproductive success, for example, in Eugenia species, because it has been shown that their seeds have high values of seed predation (Dirzo et al 2007;Silva and Pinheiro 2009;Côrtes et al 2009). …”