Sistema reprodutivo e polinização de Senna multijuga (Fabaceae) em Mata Atlântica Montana

Abstract

ResumoO conhecimento da biologia reprodutiva e polinização de árvores neotropicais vêm aumentando nas últimas décadas. No entanto, ainda é incipiente para a Mata Atlântica e muitas questões persistem, por exemplo, sobre a prevalência de autoincompatibilidade. A biologia floral, o sistema reprodutivo e os visitantes florais de Senna multijuga foram estudados, com o objetivo de verificar a ocorrência de autoincompatibilidade e determinar seus polinizadores. A espécie apresenta características florais típicas do gênero, como flores assimétricas, enantiostilia, heteranteria e deiscência poricida. A antese é diurna e a viabilidade do pólen não diferiu entre os morfos de anteras. Os polinizadores foram abelhas dos gêneros Bombus, Epicharis, Centris e Xylocopa e abelhas menores atuaram como pilhadores de pólen. A reprodução sexual em S. multijuga depende da transferência de pólen pelos polinizadores, pois não foram formados frutos por apomixia ou autopolinização. Este último resultado pode ser devido à depressão por endogamia ou a um mecanismo de autoincompatibilidade de ação tardia, uma vez que houve aborto uniforme de pistilos e penetração de tubos polínicos nos óvulos após autopolinização. Diferença na fecundidade após polinização manual e em condições naturais indica que a limitação polínica afeta o sucesso reprodutivo feminino, assim como a disponibilidade de recursos. Palavras-chave: autoincompatibilidade de ação tardia, depressão por endogamia, flor de pólen, polinização. AbstractKnowledge of reproductive biology and pollination of Neotropical tree species has been increasing in recent decades. However, this is still incipient in the Atlantic Forest, and many questions remain, for instance, about the prevalence of self-incompatibility. We studied the floral biology, breeding system and floral visitors of Senna multijuga in order to verify the occurrence of self-incompatibility and determine its pollinators. This species bears the typical floral traits of the genus, such as asymmetry, enantiostily, heteranthery and poricid anthers. Anthesis is diurnal and pollen viability did not differ among the morphs of anthers. Pollinators were bees of the genera Bombus, Epicharis, Centris and Xylocopa and smaller bees acted as pollen thieves. Sexual reproduction of Senna multijuga depends on the transfer of pollen by pollinators, as no fruit was formed by either apomixis or self-pollination. The latter result may be due to inbreeding depression or by a mechanism of late-acting selfincompatibility, as we observed after self-pollination both penetration of pollen tubes in the ovules and uniform abortion of pistils. Differences on fertility after manual crossings and under natural conditions indicate that female fitness is affected by pollen limitation, as well as by the availability of resources.

The Influence of Fire and Deforestation on the Floral Symmetry and Fitness of Adenocalymma nodosun (Bignoniaceae)

“…We also detected a significantly higher concentration of sugar in the nectar of less asymmetric plants in burned area. Several studies have shown that FA may be featured as a quantitative and quality indicator of available resources of flowers pollinators (Wignall et al, 2006;Marazzi & Endress, 2008;Wolowski & Freitas, 2010;Potts, 2015). With more symmetrical flowers in the same species as a reliable sign of good quality resources to its visitors (Wignall et al 2006).…”

Breeding systems of enantiostylous Cassiinae species (Fabaceae, Caesalpinioideae)

“…This assumption is reinforced by the large number of fruits aborted early during fruit development observed for all of the treatments evaluated in this study. Cases of late self-incompatibility were recorded in Fabaceae species and interpreted as the main cause of fruit abortion (Gibbs and Sassaki, 1998;Rodriguez-Riaño et al, 1999;Freitas and Oliveira, 2002;Leite and Machado, 2010;Wolowski and Freitas, 2010). The effects of this type of incompatibility may be confounded with those of inbreeding depression; the main difference between these two mechanisms is that fruit abscission occurs synchronically in the first, and gradually in the latter (Seavey and Bawa, 1986).…”

“…(Carvalho and Oliveira, 2003;Leite and Machado, 2010;Wolowski and Freitas, 2010) and Cassia L. (Bahadur et al, 1979). In the Caesalpinioideae, self-incompatibility is more commonly recorded in tree species with flowers that are characterized by a humid stigma (Arroyo, 1981;Owens and Lewis, 1989), and it is not known if this incompatibility is related to the occurrence of enantiostyly (Bahadur et al, 1979;Carvalho and Oliveira, 2003;Leite and Machado, 2010).…”

Pollination biology of melittophilous legume tree species in the Atlantic Forest in Southeast Brazil

“…Self-incompatibility has been suggested as prevalent in tropical trees (Bawa 1974;Bawa et al 1985b). In fact, several tropical Leguminosae tree species, such as Swartzia pickelli (Lopes & Machado 1996) and Swartzia apetala (Moço & Pinheiro 1999) in the north-eastern Atlantic rainforest, Pseudopiptadenia contorta (Prata-deAssis-Pires & Freitas 2008) and S. multijuga (Wolowski & Freitas 2010) in a montane Atlantic rainforest, Senna silvestris (Carvalho & Oliveira 2003) and Copaifera langsdorffi (Freitas & Oliveira 2002), both in the Brazilian savanna, and Caesalpinia calycina (Lewis & Gibbs 1999) in the caatinga, have been demonstrated as self-incompatible. However, since the number of treated flowers and individuals in this study was low, more experiments are necessary to detect the mating-system of these species.…”

“…The absence of this kind of study is mainly due to difficulties in reaching the flowers in the canopy (Prata-de-Assis-Pires & Freitas 2008;Rocca & Sazima 2008). To our knowledge, only a few studies to date have described the pollinators of some ornithophilous species in the canopy (Rocca et al 2006;Rocca & Sazima 2008), as well as the pollinators and reproductive biology of some melittophilous legume tree species (Borges et al 2008;Prata-de-Assis-Pires & Freitas 2008;Wolowski & Freitas 2010;Amorim et al 2013Amorim et al , Ávila et al 2015, and the bee visitors of some mass flowering tree species (Ramalho 2004;Brito & Sazima 2012).…”