Fundamental species traits across a latitudinal gradient: does the competition-colonization trade-off hold true?

One of the most common explanations for species coexistence is that trade-offs in species traits prevent any one species from excluding all others. The competition-colonization trade-off is a classic example, whereby species... [ view full abstract ]

One of the most common explanations for species coexistence is that trade-offs in species traits prevent any one species from excluding all others. The competition-colonization trade-off is a classic example, whereby species can spatially coexist if there is an inverse relationship between colonizing and competitive abilities. The strength of the trade-off is predicted to vary with latitude due to environmental and evolutionary gradients. In sessile invertebrates, patch size can be used as a tool to measure the strength of trade-off. This is because smaller patches are more difficult targets for larvae so are usually dominated by good colonizing species with high fecundity, whereas good competitors with lower fecundity can more easily find larger patches where they can grow and dominate. We measured the strength of trade-offs across 20 degrees of latitude by deploying patches of various sizes in the field. There was clear evidence for the trade-off, and the strength varied with latitude. Latitudinal variation was likely due to variation in the rate of ecological processes, particularly resource acquisition and competitive exclusion. Trade-offs were most evident at locations where resource limitation had been reached, indicating that the strength of the trade-off is mediated by resource availability.