Herbivore responses to nutrient enrichment and landscape heterogeneity in a mangrove ecosystem

Abstract

Complex gradients in forest structure across the landscape of oVshore mangrove islands in Belize are associated with nutrient deWciency and Xooding. While nutrient availability can aVect many ecological processes, here we investigate how N and P enrichment interact with forest structure in three distinct zones (fringe, transition, dwarf) to alter patterns of herbivory as a function of folivory, loss of yield, and tissue mining. The eVects of nutrient addition and zone varied by functional feeding group or speciWc herbivore. Folivory ranged from 0 to 0.4% leaf area damaged per month, but rates did not vary by either nutrient enrichment or zone. Leaf lifetime damage ranged from 3 to 10% of the total leaf area and was caused primarily by the omnivorous tree crab Aratus pisonii. We detected two distinct spatial scales of response by A. pisonii that were unrelated to nutrient treatment, i.e., most feeding damage occurred in the fringe zone and crabs fed primarily on the oldest leaves in the canopy. Loss of yield caused by the bud moth Ecdytolopha sp. varied by zone but not by nutrient treatment. A periderm-mining Marmara sp. responded positively to nutrient enrichment and closely mirrored the growth response by Rhizophora mangle across the tree height gradient. In contrast, a leaf-mining Marmara sp. was controlled by parasitoids and predators that killed >89% of its larvae. Thus, nutrient availability altered patterns of herbivory of some but not all mangrove herbivores. These Wndings support the hypothesis that landscape heterogeneity of the biotic and abiotic environment has species-speciWc eVects on community structure and trophic interactions. Predicting how herbivores respond to nutrient over-enrichment in mangrove ecosystems also requires an assessment of habitat heterogeneity coupled with feeding strategies and species-speciWc behavior measured on multiple scales of response.

Fitness-associated consequences of an omnivorous diet for the mangrove tree crab Aratus pisonii

“…This arboreal crab is abundant in neotropical mangrove systems (Beever et al 1979, Diaz & Conde 1988, Erickson et al 2003, where it is distinctive in that it forages on fresh leaf tissue in the canopy rather than on leaf litter. A. pisonii is the primary herbivore of the red mangrove Rhizophora mangle (Feller & Chamberlain 2007, Feller et al 2013, and its herbivory can account for over 40% of total leaf damage in monotypic red mangrove stands (Erickson et al 2003). As a result, these crabs provide a key link between mangrove primary production and the detrital food web, and contribute to both nutrient and biomass outwelling from mangrove systems (Beever et al 1979).…”

Inversión reproductiva de Aratus pisonii (Decapoda: Sesarmidae): diferencias entre hábitats y análisis de rutas

“…Sin embargo, otras variables no consideradas, pueden estar influyendo sobre la inversión reproductiva de A. pisonii, por ejemplo aspectos relacionados con la calidad del recurso, diferentes a la relación C/N foliar (no seleccionada por el modelo en el análisis de ruta), como el contenido de fibra cruda y de agua en las hojas (de Lacerda et al, 1986;Faraco, & Lana, 2004) o la disponibilidad de recursos alternativos (algas, frutos, flores, insectos) (Erickson et al, 2003;López, & Conde, 2013). También podría influir la dinámica de las mareas, o las interacciones de competencia, canibalismo y depredación (Wilson, 1989;Feller, & Chamberlain, 2007).…”

“…Se ha evidenciado recientemente, que las poblaciones de la vertiente del Pacífico pertenecen a una especie hermana A. pacificus Thiercelin & Schubart, 2014. A. pisonii habita en una amplia gama de ambientes, desde zonas estuarinas, pasando por ambientes marinos, hasta lagunas hipersalinas, en los cuales se asocia a varias especies de manglar: Rhizophora mangle L., Laguncularia racemosa (L.) Gaertn.f., Avicennia germinans (L.) Stearn (Conde, & Díaz, 1989a, b;Conde, 1990;Conde, et al, 2000;Erickson, Saltis, Bell, & Dawes, 2003;Feller, & Chamberlain, 2007;Colpo, Chacur, Guimarães, & Negreiros-Fransozo, 2011).…”

Coastal Habitats of the Gulf of Mexico

“…Increased inputs of nutrients to mangrove forests as a consequence of agriculture, urban sewage, and industrial effluents may have significant effects on forest structure and function by modifying net photosynthesis and other physiological processes (Lovelock et al 2004), rates of herbivory (Feller and Chamberlain 2007), production-decomposition rates , organic matter accumulation and contribution to soil elevation maintenance (McKee et al 2007a), or nutrient recycling McKee et al 2002;Whigham et al 2009). Much of the foregoing work has been conducted outside the northern GoM but the findings are relevant to understanding the general responses of mangroves to nutrient enrichment.…”