Testing biodiversity theory using species richness of reef-building corals across a depth gradient

TY - JOUR

T1 - Testing biodiversity theory using species richness of reef-building corals across a depth gradient

AU - Roberts, T. Edward

AU - Keith, Sally A.

AU - Rahbek, Carsten

AU - Bridge, Tom C.L.

AU - Caley, M. Julian

AU - Baird, Andrew H.

PY - 2019/10/1

Y1 - 2019/10/1

N2 - Natural environmental gradients encompass systematic variation in abiotic factors that can be exploited to test competing explanations of biodiversity patterns. The species–energy (SE) hypothesis attempts to explain species richness gradients as a function of energy availability. However, limited empirical support for SE is often attributed to idiosyncratic, local-scale processes distorting the underlying SE relationship. Meanwhile, studies are also often confounded by factors such as sampling biases, dispersal boundaries and unclear definitions of energy availability. Here, we used spatially structured observations of 8460 colonies of photo-symbiotic reef-building corals and a null-model to test whether energy can explain observed coral species richness over depth. Species richness was left-skewed, hump-shaped and unrelated to energy availability. While local-scale processes were evident, their influence on species richness was insufficient to reconcile observations with model predictions. Therefore, energy availability, either in isolation or in combination with local deterministic processes, was unable to explain coral species richness across depth. Our results demonstrate that local-scale processes do not necessarily explain deviations in species richness from theoretical models, and that the use of idiosyncratic small-scale factors to explain large-scale ecological patterns requires the utmost caution.

AB - Natural environmental gradients encompass systematic variation in abiotic factors that can be exploited to test competing explanations of biodiversity patterns. The species–energy (SE) hypothesis attempts to explain species richness gradients as a function of energy availability. However, limited empirical support for SE is often attributed to idiosyncratic, local-scale processes distorting the underlying SE relationship. Meanwhile, studies are also often confounded by factors such as sampling biases, dispersal boundaries and unclear definitions of energy availability. Here, we used spatially structured observations of 8460 colonies of photo-symbiotic reef-building corals and a null-model to test whether energy can explain observed coral species richness over depth. Species richness was left-skewed, hump-shaped and unrelated to energy availability. While local-scale processes were evident, their influence on species richness was insufficient to reconcile observations with model predictions. Therefore, energy availability, either in isolation or in combination with local deterministic processes, was unable to explain coral species richness across depth. Our results demonstrate that local-scale processes do not necessarily explain deviations in species richness from theoretical models, and that the use of idiosyncratic small-scale factors to explain large-scale ecological patterns requires the utmost caution.

KW - Biodiversity

KW - Community assembly processes

KW - Corals

KW - Depth

KW - Species richness gradients

KW - Species–energy hypothesis

UR - http://www.scopus.com/inward/record.url?scp=85074298850&partnerID=8YFLogxK

U2 - 10.1098/rsbl.2019.0493

DO - 10.1098/rsbl.2019.0493

M3 - Letter

C2 - 31662067

AN - SCOPUS:85074298850

SN - 1744-9561

VL - 15

JO - Biology Letters

JF - Biology Letters

IS - 10

M1 - 20190493

ER -