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Abstract

LIFE HISTORY AND MORPHOLOGICAL STRATEGIES OF SPONGES DRIVE COMMUNITY DYNAMICS ON MANGROVE ROOTS, WITH HELP FROM PREDATORS, COMPETITORS, AND PATHOGENS.

Janie L. Wulff
Florida State University
Bio

Descriptions of the rich sponge faunas inhabiting mangrove roots at various Caribbean sites are unanimous in pointing out the heterogeneity of species distribution and abundance patterns at all scales, from very local (e.g., adjacent roots) to regional. Abiotic factors have often been implicated by correlation, but the possibility that ecological interactions, and life history and morphological strategies of the sponges, also play key roles has not been examined comprehensively. I have been exploring the processes underlying these patterns by probing community dynamics with experimental manipulations and time-series censusing at sites in Belize (Twin Cays), Panama (near the Bocas del Toro station), and the Florida Keys (Long Key). Established communities on roots have been fully censused (by volume) yearly for 3 years, initially bare artificial roots (suspended pvc pipes) have been monitored for recruitment and subsequent community development for up to 5 years, and small, asexually generated (by razor blade) individuals of the 7 –9 most abundant sponge species have been placed on artificial roots and subsequent community dynamics monitored for up to 2 years. Patterns of community development on initially bare pvc pipes suggest that trade-offs between recruitment efficiency and competitive ability may be responsible for at least some among-root heterogeneity. Even though community dynamics on pipes to which individuals of the most abundant species had been added were not influenced by the stochastic effects of larval recruitment, heterogeneity of sponge distribution and abundance among pipes was still very high. When sponge species were sorted into categories defined by different morphological strategies for gaining and holding onto substratum space, it became clear that presence or absence of representatives of these morphological categories influenced community dynamics substantially. Interactions with predators, pathogens, and non-sponge spatial competitors played surprisingly important roles in creating differences among pipes that began with identical inhabitants.