Diferenciação intraespecífica na reprodução e interações planta-polinizador em populações naturais de Trembleya laniflora (Melastomataceae)
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Data
2017-11-13
Autores
Soares, Natalia Costa [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Indivíduos coespecíficos utilizam de forma diferente os recursos do nicho disponíveis às suas populações, e essas variações intraespecíficas (inter e intrapopulacionais) influenciam muitos processos ecológicos, principalmente as interações planta-animal. Em plantas com polinização biótica, a floração (época e intensidade) é uma importante adaptação aos períodos de maior abundância dos vetores de pólen, e está relacionada à atratividade aos polinizadores. A relação evolutiva entre polinizadores e caracteres florais das espécies e, ocorrência das “Síndromes de polinização” vem sendo historicamente testada, e geralmente, é confirmada a existência de uma relação direta entre um conjunto de caracteres florais e os polinizadores principais das espécies. Neste contexto, utilizando como modelo de estudo Trembleya laniflora Cong., uma espécie de Melastomataceae endêmica dos campos rupestres da porção sul da Cadeia do Espinhaço, Minas Gerais (Brasil), com populações naturalmente isoladas em afloramentos rochosos, e que apresenta características florais (flores grandes e brancas) que diferem do padrão observado para a família, tivemos como objetivo deste trabalho: (i) entender a importância ecológica e evolutiva dos distintos caracteres florais de Trembleya laniflora para a sua polinização e sucesso reprodutivo; (ii) avaliar a ocorrência de variação intraespecífica interpopulacional na ecologia reprodutiva da espécie, testando os fatores bióticos e abióticos que determinam tais diferenças e sua relevância para o sucesso reprodutivo populacional; e (iii) avaliar a variação intraespecífica interpopulacional na fenologia de floração e nas interações planta-polinizador, acessando como a especialização no nível individual e populacional afetam o sucesso reprodutivo. Para isso, observamos a fenologia reprodutiva (floração e frutificação), biologia floral, visitantes florais e polinizadores, e testamos o sistema reprodutivo da espécie; observamos e testamos as variações da fenologia reprodutiva, biologia floral e ecologia da polinização entre três populações localizadas em áreas de distintas altitudes da Serra do Cipó, MG (Cedro, 1101m; Pedra do Elefante, 1255m; Quadrante 16, 1303m), avaliando quais fatores bióticos e/ou abióticos melhor explicam o sucesso reprodutivo populacional; e avaliamos os efeitos da generalização/especialização no uso dos recursos dos nichos fenológico (tempo) e de polinização (interações indivíduo de planta-espécie de polinizador) para o sucesso reprodutivo individual e populacional. Características florais e de biologia reprodutiva (antese noturna) de T. laniflora foram associadas a um sistema de polinização especializado mediado por abelhas grandes, vibradoras, com comportamento de forrageio crepuscular. Populações espacialmente isoladas e sob distintas condições microclimáticas diferiram em sua biologia reprodutiva (inícios e picos fenológicos, hora da antese, longevidade floral, e frequência de visitas legítimas) e sucesso reprodutivo. Fatores abióticos, principalmente a temperatura, determinaram as diferenças nas datas fenológicas entre as populações, enquanto que fatores bióticos, relacionados às interações planta-polinizador, influenciaram na produção de frutos maduros e no sucesso reprodutivo. Finalmente, populações compostas por indivíduos mais generalistas em suas interações com polinizadores e sincrônicos em sua atividade de floração (época, duração e intensidade) apresentaram maior sucesso reprodutivo. No nível individual, plantas mais centrais e generalistas em suas interações com os polinizadores também apresentaram maior sucesso. Portanto, a generalização e baixo grau de especialização no uso dos recursos, tempo de floração e polinizadores, pelos indivíduos de Trembleya exerce um papel fundamental para a conservação das interações planta-polinizador e, positivamente, afetam o sucesso reprodutivo desta espécie altamente especializada para seu sistema de polinização.
Conspecific individuals vary in their use of available resources within the population, and intraspecific variations (inter and intrapopulation) in species traits play a fundamental role in many ecological processes, primarily the plant-animal interactions. The flowering activity (time and intensity) is an important adaptation to the periods of larger abundance of pollen vectors, enhancing the plant attractiveness to pollinators. The evolutionary relationship between pollinators and floral traits and the occurrence of "Pollination Syndromes" has been historically tested, and the existence of a direct relationship between a set of floral traits and the main pollinators has been generally confirmed. In this context, using as study model Trembleya laniflora Cong. (Melastomataceae), an endemic species, naturally isolated on rock outcrops from the rupestrian grasslands of South Espinhaço Range, Minas Gerais (Brazil), presenting floral characteristics (large and white flowers) that differ from the pattern observed for the family, we aimed: (i) to investigate the ecological and evolutionary importance of the distinct floral traits of Trembleya laniflora for its pollination and reproductive success; (ii) to observe and evaluate the occurrence of interpopulational intraspecific variation in the reproductive ecology of the species, testing the biotic and abiotic drivers for their reproductive success; and (iii) to evaluate intrapopulational intraspecific variation in flowering phenology and plant-pollinator interactions, accessing as specialization at individual and population levels are related to reproductive success. For this, (i) we observed the reproductive phenology (flowering and fruiting), floral biology, flower visitors and pollination, and test the reproductive system of the species; (ii) we tested for differences in the reproductive phenology, floral biology and pollination ecology among three populations located at different altitudes of Serra do Cipó, MG (Cedro, 1101m; Pedra do Elefante, 1255m; Quadrante 16, 1303m), and tested which biotic and abiotic factors explain the reproductive success of the populations; and (iii) we evaluated the effects of generalization or specialization in the use of temporal (flowering phenology) and pollination (individual pollinator-plant interactions) resources for individual and population reproductive success. Floral traits and reproductive biology (nocturnal anthesis) of T. laniflora were associated to a specialized pollination system mediated by large bees with crepuscular foraging behavior. The spatially isolated populations were under different microclimatic conditions, and differed in their reproductive biology (onset and peaks of flowering and fruiting, floral biology (anthesis, longevity, and frequency of legitimate visits) and therefore, reproductive success. Abiotic factors, mainly temperature, drove the observed differences in phenological dates, while biotic factors related to plant-pollinator interactions directly influenced the production of mature fruits and differences on populations reproductive success. Finally, populations composed of more generalist individuals in their interactions with pollinators and more synchronic in their flowering activity (season, duration and intensity) showed greater reproductive success. At the individual level, more central and generalist plants in their interactions with the main pollinators were also more successful. Therefore, generalization and low specialization in the resources use, flowering time and pollinators played a key role in the conservation of plant-pollinator interactions of Trembleya, positively affecting the reproductive success of this species presenting a highly specialized pollination system.
Conspecific individuals vary in their use of available resources within the population, and intraspecific variations (inter and intrapopulation) in species traits play a fundamental role in many ecological processes, primarily the plant-animal interactions. The flowering activity (time and intensity) is an important adaptation to the periods of larger abundance of pollen vectors, enhancing the plant attractiveness to pollinators. The evolutionary relationship between pollinators and floral traits and the occurrence of "Pollination Syndromes" has been historically tested, and the existence of a direct relationship between a set of floral traits and the main pollinators has been generally confirmed. In this context, using as study model Trembleya laniflora Cong. (Melastomataceae), an endemic species, naturally isolated on rock outcrops from the rupestrian grasslands of South Espinhaço Range, Minas Gerais (Brazil), presenting floral characteristics (large and white flowers) that differ from the pattern observed for the family, we aimed: (i) to investigate the ecological and evolutionary importance of the distinct floral traits of Trembleya laniflora for its pollination and reproductive success; (ii) to observe and evaluate the occurrence of interpopulational intraspecific variation in the reproductive ecology of the species, testing the biotic and abiotic drivers for their reproductive success; and (iii) to evaluate intrapopulational intraspecific variation in flowering phenology and plant-pollinator interactions, accessing as specialization at individual and population levels are related to reproductive success. For this, (i) we observed the reproductive phenology (flowering and fruiting), floral biology, flower visitors and pollination, and test the reproductive system of the species; (ii) we tested for differences in the reproductive phenology, floral biology and pollination ecology among three populations located at different altitudes of Serra do Cipó, MG (Cedro, 1101m; Pedra do Elefante, 1255m; Quadrante 16, 1303m), and tested which biotic and abiotic factors explain the reproductive success of the populations; and (iii) we evaluated the effects of generalization or specialization in the use of temporal (flowering phenology) and pollination (individual pollinator-plant interactions) resources for individual and population reproductive success. Floral traits and reproductive biology (nocturnal anthesis) of T. laniflora were associated to a specialized pollination system mediated by large bees with crepuscular foraging behavior. The spatially isolated populations were under different microclimatic conditions, and differed in their reproductive biology (onset and peaks of flowering and fruiting, floral biology (anthesis, longevity, and frequency of legitimate visits) and therefore, reproductive success. Abiotic factors, mainly temperature, drove the observed differences in phenological dates, while biotic factors related to plant-pollinator interactions directly influenced the production of mature fruits and differences on populations reproductive success. Finally, populations composed of more generalist individuals in their interactions with pollinators and more synchronic in their flowering activity (season, duration and intensity) showed greater reproductive success. At the individual level, more central and generalist plants in their interactions with the main pollinators were also more successful. Therefore, generalization and low specialization in the resources use, flowering time and pollinators played a key role in the conservation of plant-pollinator interactions of Trembleya, positively affecting the reproductive success of this species presenting a highly specialized pollination system.
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Palavras-chave
Crepuscular bees, Campo rupestre, Floral traits, Plant Phenology, Individual specialization, Caracteres florais, Fenologia vegetal