Effects of Isolation on a Coral Reef MetacommunityEPA Grant Number: F5E11007
Title: Effects of Isolation on a Coral Reef Metacommunity
Investigators: Lee, Sarah C.
Institution: University of North Carolina at Chapel Hill
EPA Project Officer: Cobbs-Green, Gladys M.
Project Period: September 1, 2005 through August 31, 2008
Project Amount: $104,300
RFA: STAR Graduate Fellowships (2005) RFA Text | Recipients Lists
Research Category: Academic Fellowships
The proposed research focuses on the effects of increased patch isolation on extinction risk and metacommunity composition in a marine system. Specifically I will explore how increased isolation of habitat patches affect resident species richness and relative abundances, and what mechanism(s) control the effects of isolation on metacommunities. I will test hypotheses derived from competition-colonization trade-off (CCTO) and source-sink (SS) metacommunity models. Using empirically determined population parameters, I will determine which model best explains observed patterns of coexistence in natural communities.
Obligate commensal decapod crustaceans (primarily trapezeid crabs and alpheid shrimp) living in heads of the hard coral Pocillopora meandrina are ideal model systems because they are easily identified and their habitat occurs as discrete patches that are easily manipulated. With this model system I will address two main research questions:
Q1. How does increasing isolation affect commensal communities?
I will test the effects of isolation on community assembly of adult and juvenile decapods by transplanting defaunated (i.e. with all commensals removed) habitat patches (i.e. Pocillopora meandrina heads) in spatial arrays with different degrees of patch isolation from a source population. I will test hypotheses derived from CCTO and SS models, namely, that increased isolation decreases species richness and alters relative species abundances. Changes in relative species abundances in response to isolation will be analyzed using analysis of similarities.
Q2. What mechanisms control the response to increased isolation?
I will then determine mechanisms by which isolation affects commensal metacommunities (e.g. by mediating CCTO or SS dynamics). The parameters necessary to test existing CCTO and SS models will be quantified experimentally. Using these empirically determined values for dispersal ability, competitive strength and mortality, I will explore population trajectories and possible outcomes with parameterized values in existing models. By comparing model predictions with observed patterns of coexistence in natural and isolated communities, I will distinguish whether competitive trade offs or source-sink dynamics are likely mechanisms of meta-scale coexistence.
The proposed experiments will be among the first manipulative tests of multi-species metapopulation models and will provide a mechanistic understanding of how isolation can affect community composition. Although the specific data will describe a system with relatively small spatial scale, my results will identify a theoretical foundation upon which larger scale models can be based. The results will also be of particular relevance in designing marine reserves because this research will expand current metapopulation models to include multi-species patch networks.