Publication Date

2012-05-02

Availability

Embargoed

Embargo Period

2013-05-02

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Marine Biology and Fisheries (Marine)

Date of Defense

2011-11-30

First Committee Member

Diego Lirman

Second Committee Member

Margaret W. Miller

Third Committee Member

Douglas L. Crawford

Fourth Committee Member

Iliana B. Baums

Fifth Committee Member

Jack Fell

Abstract

As the resiliency of coral reefs is eroded by a variety of natural and anthropogenic stressors, corallivory is becoming an increasingly important factor affecting the structure and function of these important ecosystems. Yet, little is known about the mechanistic drivers of coral-corallivore dynamics in many regions, including the Caribbean. In this dissertation, I used an integrated approach to investigate the evolutionary ecology of the coral-eating gastropod, Coralliophila abbreviata, on the reefs of Florida and the Caribbean. Coralliophila abbreviata snails live and feed on most of the major reef-building corals in the region and cause substantial and chronic mortality of the threatened acroporid corals, Acropora palmata and A. cervicornis. The overall objective of this research was to elucidate feedback mechanisms between coral community structure and snail population structure and dynamics. In the first age-based analysis of C. abbreviata populations, I identified remarkable coral-host-associated variation in life-history traits of snails on Florida reefs. Based on estimates of fitness correlates such as growth, longevity, and female reproductive output, A. palmata appears to be a superior host for C. abbreviata compared to two other common coral taxa investigated (Diploria spp. and Montastraea spp.). However, host-specific life-history trade-offs may exist for individual snails that act to balance snail population fitness across hosts. I then developed a set of five polymorphic microsatellite loci that were used in conjunction with mitochondrial cytochrome b sequence data to assess the population genetic structure and demographic history of C. abbreviata from three coral host taxa (A. palmata, Montastraea spp., Mycetophyllia spp.) and six geographic locations spanning most of the species’ range. I found no evidence of genetic differentiation among the snail populations sampled. Demographic analyses of population genetic data support a scenario of a large population expansion during the Pleistocene, a time of major carbonate reef development in the region. These results indicate that C. abbreviata are successful generalist coral predators with unrestricted gene flow throughout the greater Caribbean. On a reef scale, the density and identity of neighboring corals indirectly affected predation pressure on focal A. cervicornis colonies in a manipulative field experiment. Snails exhibited a strong feeding preference for A. cervicornis during the experiment but the presence of the alternative prey, M. faveoloata, also contributed to predator abundance in the experimental plots. Thus, M. faveolata neighbors had a negative effect on A. cervicornis colonies through apparent competition. Overall, these results have implications for coral reef community structure and dynamics. Understanding these processes is necessary to develop effective conservation and management strategies for imperiled corals and predict how these communities will respond to further perturbations in the future.

Keywords

Caribbean coral reefs; Host associated variation; Acropora; corallivory; population genetics; apparent competition

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