Biotic interactions shape trait assembly of marine communities across time and latitude

Abstract

Assembly processes are highly dynamic with biotic filters operating more intensely at local scales, yet the strength of biotic interactions can vary across time and latitude. Predation, for example, can be stronger at lower latitudes, while competition can intensify at later stages of assembly due to resource limitation. Since biotic filters act upon functional traits of organisms, we explored trait-mediated community assembly in diverse marine assemblages from four regions along the Pacific coast of North and Central America. Using predator exclusion experiments and two assembly stages, we tested the hypotheses that non-random trait patterns would emerge during late assembly at all regions due to competition and at lower latitude regions regardless of assembly stage due to predation. As expected, trait divergence occurred in late assembly but only at higher latitude regions, while in tropical Panama, relaxed predation caused trait divergence during late assembly. Moreover, colonizing trait strategies were common during early assembly while competitive strategies were favoured during late assembly at higher latitude regions. Predation-resistant traits were only favoured in Panama during both assembly stages. Our large-scale manipulative study demonstrates that different biotic interactions across time and latitude can have important consequences for trait assembly.

Distribution of functionally distinct native and non‐indigenous species within marine urban habitats

“…In particular, plot‐ or site‐specific filtering associated with predation over assembly may be reflected by trade‐offs in growth forms and types of defence, among others, in the functional structure (second axis in PCoA, Figure 3b). Along with others (Boyé et al, 2019; López & Freestone, 2022), our results encourage further development of trait‐based approaches to explore assembly processes at varying scales.…”

Speed and degree of functional and compositional recovery varies with latitude and community age

“…The markedly lower, and highly seasonal, recruitment rates, greater open space, and lower biomass at early assembly that characterized subarctic Alaska point to very different dynamics of recruitment and growth that collectively contribute to the slower functional recovery in this region. While higher net primary productivity can increase growth rates (Pregitzer & Euskirchen, 2004) and productivity is important in determining resilience (Palumbi et al, 2008), faster biomass and space recovery could also be explained by the abundance of fast-growing traits at lower latitudes (L opez & Freestone, 2022;L opez et al, unpublished manuscript). In addition, lower-latitude communities, particularly in tropical and subtropical latitudes, experience more stable climates and longer growing seasons (Hillebrand, 2004b), factors that further facilitate growth and, therefore, the potential for functional recovery.…”

“…Further, these low-latitude regions where predation is known to be strong also harbor more diverse species pools (e.g., Hillebrand, 2004a). Tropical and subtropical species pools are likely to have both a higher diversity and redundancy of traits (L opez & Freestone, 2022;McLean et al, 2019), providing the building blocks for fast functional recovery in these systems. In terms of composition, species pools in the tropics can also be both spatially and temporally variable, and individuals removed by disturbance may not be replaced by individuals of the same species as the composition of available propagules changes (Freestone & Inouye, 2015).…”