Data from: Interspecific interactions through 2 million years: are competitive outcomes predictable?

Ecological interactions affect the survival and reproduction of individuals. However, ecological interactions are notoriously difficult to measure in extinct populations, hindering our understanding of how the outcomes of interactions such as competition vary in time and influence long-term evolutionary changes. Here, the outcomes of spatial competition in a temporally continuous community over evolutionary time scales are presented for the first time. Our research domain is encrusting cheilostome bryozoans from the Wanganui Basin of New Zealand over a c. 2 million year time period (Pleistocene to Recent). We find that a subset of species can be identified as consistent winners and others, as consistent losers in the sense that they win or lose interspecific competitive encounters statistically more often than the null hypothesis of 50%. Most species do not improve or worsen in their competitive abilities through the 2 million year period, but a minority of species are winners in some intervals and losers in others. We found that conspecifics tend to cluster spatially and interact more often than expected under a null hypothesis: most of these are standoff interactions where the two colonies involved stopped growing at edges of encounter. Counter-intuitively, competitive ability has no bearing on ecological dominance.