COMPETITIVE INTERACTIONS AND THEIR TAPHONOMIC CONSEQUENCES AMONG THE ENCRUSTER GUILD
To solve this question, overgrowth interactions were used to compare between two encrusting strategies: that of obligate versus facultative encrusters occupying hermitted shells. McKinney's overgrowth equation (McKinney, 1995, Palaios 10: 279-282) was developed to determine relative rates of interactions among modular organisms on hard substrata, taking into account time averaging. As he stated, if hard substrates remain available for settlement for several seasons, then taphonomic processes should provide for a conservative estimate of overgrowth relationships and competitive superiority. Using modern hermit-crab inhabited shells from Sapelo Island, Georgia, McKinney's overgrowth equation was used to test whether two obligate encrusters were statistically more likely to have more overgrowth relationships than facultative encrusters, and were thus competitively superior. Evolutionary predictions suggest that the obligate encrusters would be competitively superior, having evolved for millions of years (see Walker, 1992, Journal of Paleontology 66: 535-558) with their symbiotic host (the hermit crab) while the facultative species would be least competitive. Results will be presented in relation to the taphonomic and biotic factors (i.e. shell species encrusted, hermit crab species) that affect the competitive outcomes for obligate versus facultative modular encrusters.