Padrão espacial da chuva de sementes gerada por aves dispersoras de uma palmeira tropical
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Data
2021-08-04
Autores
Winter, Mariana Giuliatti [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A diversidade de espécies em florestas tropicais é fortemente moldada por interações mutualistas entre as plantas e os animais que se alimentam de frutos e que dispersam sementes. Compreender os processos subjacentes à dispersão de sementes é importante para entender como e onde se inicia o ciclo de vida das plantas, influenciando a manutenção populacional e moldando as respostas às mudanças globais. Este trabalho teve como objetivo investigar o padrão espacial da chuva de sementes de uma palmeira considerada uma espécie chave, Euterpe edulis. Nossas três hipóteses são: (1) a chuva de sementes é agregada e espacialmente associada a plantas coespecíficas frutificando; (2) a chuva de sementes é agregada e espacialmente associada a plantas heteroespecíficas zoocóricas; e (3) terrenos com desnível mais baixo acumulam maior chuva de sementes. Usamos a localização geográfica das palmeiras reprodutivas e coletamos e georreferenciamos 455 sementes recém-dispersas em uma parcela de 1 ha no Parque Estadual da Serra do Mar (núcleo Santa Virgínia) em São Paulo. Utilizamos as análises de padrões de pontos uni- e bivariados para caracterizar a distribuição espacial da chuva de sementes. Os resultados foram baseados em 455 sementes, 186 palmeiras adultas e 911 indivíduos arbóreos de espécies zoocóricas que se reproduzem no mesmo período da espécie modelo. As análises de padrão de pontos indicaram que as sementes estão espacialmente agregadas e espacialmente associadas às palmeiras reprodutivas. Porém, não corroboramos a hipótese sobre as heterospecíficas, já que as sementes apresentaram independência espacial em relação às árvores zoocóricas heteroespecíficas. A hipótese três foi corroborada, já que observamos uma maior intensidade de padrão de pontos (sementes) em terrenos mais baixos. Este estudo foi realizado em uma das reservas mais preservadas da Mata Atlântica. Portanto, o padrão de dispersão que observamos representa o resultado de interações biodiversas, em seu melhor cenário. Sabemos que a defaunação, por ocasionar a extirpação de grandes animais e frugívoros, pode afetar a quantidade e padrão de dispersão de sementes. Então é importante conhecer o sistema em um local preservado para entendermos o que estamos perdendo em ambientes fragmentados, que é o que mais sobrou da Mata Atlântica.
Species diversity in tropical forests is strongly shaped by mutualistic interactions between fruit- eating and seed-dispersing plants and animals. Understanding the processes underlying seed dispersal is important to understand how and where the plant life cycle begins, influencing population maintenance and shaping responses to global change. This work aimed to investigate the spatial pattern of seed rain of a palm tree considered a key species, Euterpe edulis. Our three hypotheses are: (1) the seed rain is aggregated and spatially associated with conspecific plants bearing fruits; (2) the seed rain is aggregated and spatially associated with heterospecific zoochoric plants; and (3) terrain with lower slopes accumulate more seed rain. We used the geographic location of the reproductive palms and collected and georeferenced 455 newly dispersed seeds in a 1 ha plot in Serra do Mar State Park in São Paulo. We used univariate and bivariate point pattern analyses to characterize the spatial distribution of the seed rain. The results were based on 455 seeds, 186 adult palms and 911 arboreal species of zoochoric species that reproduce in the same period as the model species. Point pattern analysis indicated that seeds are spatially aggregated and spatially associated with reproductive palms. However, the hypothesis about heterospecific trees was not supported, as seeds were spatially independent in relation to heterospecific zoochoric trees. The third hypothesis was corroborated, as we observed a higher point pattern intensity in lower terrain. This study was carried out in one of the most preserved reserves in the Atlantic Forest. Therefore, the dispersal pattern we observe represents the result of biodiverse interactions, in their best case. We know that defaunation, by causing the extirpation of large animals and frugivores, can affect the quantity and pattern of seed dispersal. So, it is important to know the system in a preserved area to understand what we are missing in fragmented environments, which is what's most left of the Atlantic Forest.
Species diversity in tropical forests is strongly shaped by mutualistic interactions between fruit- eating and seed-dispersing plants and animals. Understanding the processes underlying seed dispersal is important to understand how and where the plant life cycle begins, influencing population maintenance and shaping responses to global change. This work aimed to investigate the spatial pattern of seed rain of a palm tree considered a key species, Euterpe edulis. Our three hypotheses are: (1) the seed rain is aggregated and spatially associated with conspecific plants bearing fruits; (2) the seed rain is aggregated and spatially associated with heterospecific zoochoric plants; and (3) terrain with lower slopes accumulate more seed rain. We used the geographic location of the reproductive palms and collected and georeferenced 455 newly dispersed seeds in a 1 ha plot in Serra do Mar State Park in São Paulo. We used univariate and bivariate point pattern analyses to characterize the spatial distribution of the seed rain. The results were based on 455 seeds, 186 adult palms and 911 arboreal species of zoochoric species that reproduce in the same period as the model species. Point pattern analysis indicated that seeds are spatially aggregated and spatially associated with reproductive palms. However, the hypothesis about heterospecific trees was not supported, as seeds were spatially independent in relation to heterospecific zoochoric trees. The third hypothesis was corroborated, as we observed a higher point pattern intensity in lower terrain. This study was carried out in one of the most preserved reserves in the Atlantic Forest. Therefore, the dispersal pattern we observe represents the result of biodiverse interactions, in their best case. We know that defaunation, by causing the extirpation of large animals and frugivores, can affect the quantity and pattern of seed dispersal. So, it is important to know the system in a preserved area to understand what we are missing in fragmented environments, which is what's most left of the Atlantic Forest.
Descrição
Palavras-chave
Euterpe edulis, Tropical, Mata Atlântica, Análise espacial em padrão de pontos, Dispersão de sementes, Atlantic forest, Point pattern analysis, Seed dispersal