Leaf miner and plant galler species richness on Acacia: relative importance of plant traits and climate.
ABSTRACT Diversity patterns of herbivores have been related to climate, host plant traits, host plant distribution and evolutionary relationships individually. However, few studies have assessed the relative contributions of a range of variables to explain these diversity patterns across large geographical and host plant species gradients. Here we assess the relative influence that climate and host plant traits have on endophagous species (leaf miners and plant gallers) diversity across a suite of host species from a genus that is widely distributed and morphologically variable. Forty-six species of Acacia were sampled to encapsulate the diversity of species across four taxonomic sections and a range of habitats along a 950 km climatic gradient: from subtropical forest habitats to semi-arid habitats. Plant traits, climatic variables, leaf miner and plant galler diversity were all quantified on each plant species. In total, 97 leaf mining species and 84 plant galling species were recorded from all host plants. Factors that best explained leaf miner richness across the climatic gradient (using AIC model selection) included specific leaf area (SLA), foliage thickness and mean annual rainfall. The factor that best explained plant galler richness across the climatic gradient was C:N ratio. In terms of the influence of plant and climatic traits on species composition, leaf miner assemblages were best explained by SLA, foliage thickness, mean minimum temperature and mean annual rainfall, whilst plant gall assemblages were explained by C:N ratio, %P, foliage thickness, mean minimum temperature and mean annual rainfall. This work is the first to assess diversity and structure across a broad environmental gradient and a wide range of potential key climatic and plant trait determinants simultaneously. Such methods provide key insights into endophage diversity and provide a solid basis for assessing their responses to a changing climate.
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ABSTRACT: The availability and quality of resources for herbivores in tropical dry forests (TDFs) vary in time and space, affecting herbivore guilds differently across spatial scales (both horizontally and vertically), with consequences to the distribution of leaf damage in these forests. We attempted to elucidate the distribution patterns of herbivorous insect guilds and leaf damage throughout the secondary succession and vertical stratification along the rainy season in a Brazilian TDF. With the advance of the succession, a greater richness and abundance of herbivorous insects were found, resulting in higher leaf damage in intermediate and late stages. This pattern, however, was not observed for the frequency of leaf miners. At a smaller spatial scale, the host tree height positively affected the richness and abundance of insects. The higher leaf damage was found in canopy, which also harbored a greater richness and abundance of chewing herbivores compared to the understory at both the beginning and the end of the rainy season. Although for sap-sucking insects, this was only true at the beginning of the season. We detected a decrease in insect richness and abundance at the end of the rainy season, probably due to a synchronization of insect activity with the availability of young, highly nutritious plant tissues. These results are consistent with other studies that found a general trend of increasing richness and abundance of herbivorous insects and leaf damage throughout the secondary succession (early to late stages) and between vertical strata (understory to canopy), suggesting that forest complexity positively affects herbivores. Resumo Em florestas tropicais secas (FTSs), a disponibilidade e qualidade de recursos para herbívoros variam no tempo e espaço, afetando as guildas de herbívoros de forma diferente dependendo da escala espacial (tanto horizontal como verticalmente), com consequências para a distribuição do dano foliar nesses ecossistemas. No presente estudo foram testadas hipóteses ecológicas que tentam elucidar os padrões de distribuição de insetos herbívoros e dano foliar causado por distintas guildas de insetos ao longo da sucessão secundária, estratificação vertical e da estação chuvosa em uma FTS brasileira. De maneira geral, estágios de sucessão avançados (intermediário e tardio) abrigaram uma maior riqueza e abundância de insetos herbívoros de vida livre, resultando em maior porcentagem de área foliar removida por planta nesses estágios. Porém, esse padrão não foi verificado para insetos minadores. Em uma escala espacial menor, verificamos que a altura da árvore afetou positivamente a riqueza e abundância de insetos herbívoros. Os maiores níveis de herbivoria foram encontrados no dossel, onde também foi detectada maior riqueza e abundância de herbívoros mastigadores tanto no início quanto no final da estação chuvosa. Entretanto, para insetos sugadores o mesmo só foi observado no início dessa estação. Por fim, observamos uma redução na riqueza e abundância de insetos herbívoros no final da estação chuvosa, provavelmente devido à sincronização da atividade dos insetos com a produção de folhas novas e de melhor qualidade nutricional. Nossos resultados corroboram outros estudos que observaram uma tendência geral de aumento da riqueza e abundância de insetos herbívoros e dano foliar ao longo da sucessão secundária e entre estratos verticais, sugerindo um efeito positivo da complexidade florestal sobre os herbívoros.Biotropica 10/2013; · 2.35 Impact Factor
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ABSTRACT: The fossil record demonstrates that past climate changes and extinctions significantly affected the diversity of insect leaf-feeding damage, implying that the richness of damage types reflects that of the unsampled damage makers, and that the two are correlated through time. However, this relationship has not been quantified for living leaf-chewing insects, whose richness and mouthpart convergence have obscured their value for understanding past and present herbivore diversity. We hypothesized that the correlation of leaf-chewing damage types (DTs) and damage maker richness is directly observable in living forests. Using canopy access cranes at two lowland tropical rainforest sites in Panamá to survey 24 host-plant species, we found significant correlations between the numbers of leaf chewing insect species collected and the numbers of DTs observed to be made by the same species in feeding experiments, strongly supporting our hypothesis. Damage type richness was largely driven by insect species that make multiple DTs. Also, the rank-order abundances of DTs recorded at the Panamá sites and across a set of latest Cretaceous to middle Eocene fossil floras were highly correlated, indicating remarkable consistency of feeding-mode distributions through time. Most fossil and modern host-plant pairs displayed high similarity indices for their leaf-chewing DTs, but informative differences and trends in fossil damage composition became apparent when endophytic damage was included. Our results greatly expand the potential of insect-mediated leaf damage for interpreting insect herbivore richness and compositional heterogeneity from fossil floras and, equally promisingly, in living forests.PLoS ONE 01/2014; 9(5):e94950. · 3.53 Impact Factor
Dataset: Neves et al. (2014) Biotropica