Interactions of gall-formers and leaf-chewers on a tropical tree fern: evidence for non-repulsion and co-occurrence between insect guilds.

Host plant selection by herbivores is driven by a complex array of cues, including leaf traits and previous leaf damage. Herbivore-associated cues to host selection at the plant and leaf scale aid understanding of mechanisms responsible for host preference that might translate into increased performance, as well as processes structuring herbivore populations mediated by interactions. We investigated how changes induced by a galling insect in the tropical fern Cyathea phalerata act as repellent or attractant cues for sawfly feeding and the effects of leaf size on herbivory levels. We recorded gall abundance, damage by chewers, leaf size, plant nutritional quality, phenolic concentration and leaf anatomical traits between galled and non-galled leaf samples. Galled samples contained less N, higher levels of phenolics and higher C/N ratio. However, leaf-chewing damage did not differ between galled and non-galled leaves. The gall structure was avoided by chewers, as it had high concentrations of phenolics, lignification and suberization. Larger leaves sustained higher gall abundance, but leaf size did not have a significant effect on chewer damage. A co-occurrence index calculated for both guilds indicated that galls and chewers exhibited a distribution that did not differ from random, reinforcing that the two guilds on C. phalerata do not show patterns of repulsion such as those maintained by interspecific competition. Sawflies dismissing chemical cues indicate that the increase in phenolics caused by galling insects does not generate increased protection of the galled pinnules. Our results highlight ferns as key resources for herbivores and as a potential plant group to study new research avenues on plant-insect interactions.

Abiotic factors drives floristic variations of fern's metacommunity in an Atlantic Forest remnant / Fatores abióticos regulam as variações florísticas na metacomunidade de samambaias em um remanescente de Floresta Atlântica

Abstract We analyzed floristic variations in fern's metacommunity at the local scale and their relationship with abiotic factors in an Atlantic Forest remnant of northeastern Brazil. Floristic and environmental variations were accessed on ten plots of 10 × 20 m. We performed cluster analyses, based on Bray-Curtis dissimilarity index to establish the floristic relationship. The influence of abiotic factors: luminosity, temperature, relative air humidity and relative soil moisture was evaluated from a redundancy analysis. We found 24 species belonging to 20 genera and 12 families. The fern's flora showed high floristic heterogeneity (>75% for most of the plot's associations). The fern's metacommunity was structured along an abiotic gradient modulated by temperature, luminosity, and relative soil moisture.

Resumo Analisamos as variações florísticas na metacomunidade de samambaias em escala local e sua relação com fatores abióticos em um remanescente de Floresta Atlântica no Nordeste do Brasil. Variações florísticas e ambientais foram acessadas a partir de dez parcelas de 10 × 20 m. Realizamos análises de cluster, baseado no índice de similaridade de Bray-Curtis para estabelecer relações florísticas. A influência de fatores abióticos: luminosidade, temperatura, umidade relativa do ar e umidade relativa do solo foram avaliadas a partir da análise de redundância. Encontramos 24 espécies pertencentes a 20 gêneros e 12 famílias. A flora de samambaias exibiu uma elevada heterogeneidade florística (>75% para a maioria das associações entre plots). Observou-se que a metacomunidade de samambaias estava estruturada ao longo de um gradiente abiótico modulado pela temperatura, luminosidade e umidade relativa do solo.

Abiotic factors drives floristic variations of fern's metacommunity in an Atlantic Forest remnant.

We analyzed floristic variations in fern's metacommunity at the local scale and their relationship with abiotic factors in an Atlantic Forest remnant of northeastern Brazil. Floristic and environmental variations were accessed on ten plots of 10 × 20 m. We performed cluster analyses, based on Bray-Curtis dissimilarity index to establish the floristic relationship. The influence of abiotic factors: luminosity, temperature, relative air humidity and relative soil moisture was evaluated from a redundancy analysis. We found 24 species belonging to 20 genera and 12 families. The fern's flora showed high floristic heterogeneity (>75% for most of the plot's associations). The fern's metacommunity was structured along an abiotic gradient modulated by temperature, luminosity, and relative soil moisture.