Facilitation cascades create a predation refuge for biodiversity in a novel connected habitat

Abstract

Communities structured via facilitation cascades whereby one habitat-forming species promotes a secondary habitat-forming species with synergistic effects on biodiversity are increasingly documented. Habitat-formers can also extend the realized niche of other habitat-forming species by facilitating their recruitment into novel environments across heterogeneous landscapes. However, further understanding of whether secondary habitat-formers in these novel environments differ in their structure or support different communities from those settled in their natal habitat is required. Here, we investigated whether abiotic and biotic conditions in a novel connected habitat influence biodiversity within a secondary habitat-former facilitated outside its natal habitat. We contrasted the morphology of the habitat-forming alga, Sirophysalis trinodis, and its associated fish and epifaunal community occurring on rocky reef (natal habitat) and on nearby a biogenic hard substrate, live clam shells (novel habitat) in soft sediments. The algae on clams had a different morphology to those on the rocky shore and supported increased abundance of some epifaunal species. A reciprocal transplant experiment of S. trinodis individuals among habitats found that differences in the abundance of epifauna were explained by the increased abundance and consumption rates of predatory fish on the reef habitat compared to soft-sediment habitats, and not by differences in algal morphology between habitats. We demonstrate that facilitation promotes a secondary habitat-former into a novel habitat, which then enhances the abundance of associated epifauna by providing a predation refuge. This study contributes to a small but growing body of research demonstrating landscape-scale effects of facilitation cascades, and that basal habitat-formers can extend the realized niche of secondary habitat-formers and their associated communities.

Indirect effects shape macroalgal epifaunal communities

“…Algae have frequently been shown to provide protection to epifauna against predation Bueno et al, 2020;Lanham et al, 2020;Ware et al, 2019), but in this system, we found no evidence of direct top-down control of epifaunal numbers by predators. On the contrary, we did find evidence of both top-down (grazing) and bottom-up (nutrient supply) effects on macroalgae, which had indirect effects on epifauna by modifying their habitat.…”

Playing to the Positives: Using Synergies to Enhance Kelp Forest Restoration

“…There is also some evidence that habitat-forming species can facilitate other spatially distant habitat-formers, that is, facilitation often occurs at larger, seascape scales (Gribben et al, 2019). For example, in soft-sediment environments, beds of mussels can promote the high abundances of other bivalves by altering hydrodynamic regimes at distances of 100s of meters away from the mussel beds (Donadi et al, 2013), and clams provide a hard substratum for fucoid settlement thus extending their distribution from their natal habitat (rocky shore) to a connected novel habitat (Lanham et al, 2020). Therefore, kelp restoration may only succeed if the habitat is made more amenable for growth by the presence of another habitat-forming species (e.g., another kelp species) in the local seascape.…”

Habitat‐setting affects biodiversity while predation determines oyster survival on experimental oyster reefs

“…To test if differences in predator communities among habitat‐settings explained differences in macroinvertebrate communities, we quantified predators in each habitat‐setting using un‐baited remote underwater video cameras (Lanham et al 2020; Martínez‐Baena et al 2022). During the first experiment, the reef units were filmed twice over 2 days in May–June 2021.…”