HOW DOES A WINNER EQUIP ITSELF? A TRAIT-BASED ANALYSIS OF COMPETITIVE OUTCOMES OVER 2 MILLION YEARS

A benthic community of encrusting organisms has lived and evolved side-by-side in coastal New Zealand over more than two million years. Everyday for the two million years, colonies of cheilostome bryozoans fought for space, without which they can neither feed nor reproduce. Because space is such a crucial resource for encrusting organisms, competition for territory is likely to have consequences for both short-term and long-term evolutionary outcomes. We studied both fossil and contemporary colonies of cheilostomes in the Wanganui Basin of North Island, New Zealand, to document patterns of competitive overgrowths. We ask the questions: which traits can predict overgrowth outcomes and whether some of those traits change over time and why. Using thousands of interactions, we show that zooid size is in important predictor in competitive overgrowths, together with other traits such as spines, avicularia and budding types, but that size also changes through time within a given species.