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 timescales are presented for the first time. Our research domain is encrusting cheilostome bryozoans from the Wanganui Basin of New Zealand over a ca 2 Myr 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 Myr 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 stand-off interactions where the two colonies involved stopped growing at edges of encounter. Counterintuitively, competitive ability has no bearing on ecological dominance.

生态相互作用影响个体的存活与繁殖。然而，众所周知，已灭绝种群中的生态相互作用难以被精准测定，这一困境极大阻碍了我们理解竞争等相互作用的结果如何随时间动态变化，并进而影响长期演化进程。本研究首次报道了演化时间尺度下时间连续群落中的空间竞争结果。本次研究的对象为新西兰旺阿努伊盆地（Wanganui Basin）中，距今约2百万年（更新世至现代）的附着型唇口目苔藓动物（encrusting cheilostome bryozoans）。研究发现，可将部分物种界定为持续获胜者，其余则为持续失败者：相较于50%的零假设概率，这些物种在种间竞争遭遇事件中获胜或失败的频率在统计学上显著偏高。在这2百万年的时间跨度内，多数物种的竞争能力未出现显著提升或衰退，但少数物种在部分时段表现为获胜者，在其他时段则沦为失败者。研究还观察到，同种个体倾向于在空间上聚集，且其交互频率高于零假设下的预期水平；其中多数交互为对峙型交互——当两个群体接触到彼此生长边缘时，双方均停止生长。与直觉相悖的是，物种的竞争能力与其生态主导地位并无关联。