Larval dispersal drives trophic structure across Pacific coral reefs

Abstract

Top predators are a critical part of healthy ecosystems. Yet, these species are often absent from spatially isolated habitats leading to the pervasive view that fragmented ecological communities collapse from the top down. Here we study reef fish from coral reef communities across the Pacific Ocean. Our analysis shows that species richness of reef fish top predators is relatively stable across habitats that vary widely in spatial isolation and total species richness. In contrast, species richness of prey reef fish declines rapidly with increasing isolation. By consequence, species-poor communities from isolated islands have three times as many predator species per prey species as near-shore communities. We develop and test a colonization-extinction model to reveal how larval dispersal patterns shape this ocean-scale gradient in trophic structure.

A process‐based model supports an association between dispersal and the prevalence of species traits in tropical reef fish assemblages

“…Thus, larger-bodied species should be found in higher proportion in distant and less stable reef habitats (Luiz et al 2012, Stier et al 2014, Barneche et al 2019). Thus, larger-bodied species should be found in higher proportion in distant and less stable reef habitats (Luiz et al 2012, Stier et al 2014, Barneche et al 2019).…”

“…Longer PLDs imply a longer period of movement after emigration, increasing chances of colonization of remote and isolated reefs (Stier et al 2014). Longer PLDs imply a longer period of movement after emigration, increasing chances of colonization of remote and isolated reefs (Stier et al 2014).…”

“…Further, we expect a greater proportion of small-bodied species to be found in the less isolated reef habitats such as those of the Indo-Australian Archipelago and the Caribbean regions (Stier et al 2014, Barneche et al 2019). Further, we expect a greater proportion of small-bodied species to be found in the less isolated reef habitats such as those of the Indo-Australian Archipelago and the Caribbean regions (Stier et al 2014, Barneche et al 2019).…”

“…Limited dispersal ability in animal and plants resulting from a combination of traits is thought to prevent the persistence of gene flow among populations (Loveless and Hamrick 1984, Bradbury et al 2008, Huyghe and Kochzius 2017 and ultimately lead to speciation (Kisel and Barraclough 2010, Riginos 2014, Tedesco et al 2017. Due to these processes, species-poor areas that have been historically disturbed or isolated for a long time should display a higher proportion of species with high dispersal ability (Stier et al 2014, Ottimofiore et al 2017. Lastly, when new remote habitats are made available, such as oceanic islands (Cowie and Holland 2006), high dispersal facilitates their colonisation (Luiz et al 2013, Alzate et al 2019a).…”

A test of trophic cascade theory: fish and benthic assemblages across a predator density gradient on coral reefs

“…Consequently, coral reefs may deviate from the linear trophic chains that classical trophic cascade theory assumes. Moreover, primary productivity, consumption rates, and the dispersal of larvae or predators among reefs may mediate top-down control at the reef scale (Stier et al 2014). Further, experimental manipulations are not feasible across whole reef and large spatial scales, so coral reef ecologists instead must utilize natural experiments.…”