Abstract

Sympatric species may partition resources to reduce competition and facilitate co‐existence. While spatial variation and specialization in feeding strategies may be prevalent among large marine predators, studies have focussed on sharks, birds, and marine mammals. We consider for the first time the isotopic niche partitioning of co‐occurring, teleost reef predators spanning multiple families. Using a novel tri‐isotope ellipsoid approach, we investigate the feeding strategies of seven of these species across an atoll seascape in the Maldives. We demonstrate substantial spatial variation in resource use of all predator populations. Furthermore, within each area, there was evidence of intraspecific variation in feeding behaviors that could not wholly be attributed to individual body size. Assessing species at the population level will mask these intraspecific differences in resource use. Knowledge of resource use is important for predicting how species will respond to environmental change and spatial variation should be considered when investigating trophic diversity.

Highlights

  • Trophic interactions are key regulators of community dynamics and ecosystem function

  • Food web and population dynamics are driven by resource availability, with sympatric species often in direct com‐ petition with each other (Schoener, 1983)

  • Often linked to body size or ontogeny (Werner & Gilliam, 1984), increasing evidence suggests that individuals may vary in their re‐ source usage compared with conspecifics of the same age and size (Araújo, Bolnick, & Layman, 2011)

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Summary

| INTRODUCTION

Trophic interactions are key regulators of community dynamics and ecosystem function. There is a lack of isotopic information on re‐ source partitioning among co‐occurring teleost predators (Matley, Tobin, Simpfendorfer, Fisk, & Heupel, 2017), in the trop‐ ics (Cameron et al, 2019) This is despite the fact that coral reefs often support a high biomass and diversity of sympatric teleost pred‐ ators (Friedlander, Sandin, DeMartini, & Sala, 2010; Stevenson et al, 2007), a factor thought to increase the occurrence of dietary spe‐ cialization (Araújo et al, 2011). Along with their predator populations, are currently experiencing unprecedented worldwide declines due to a range of anthropogenic and climate‐related stress‐ ors (Friedlander & DeMartini, 2002; Hughes et al, 2017) Given their potential stabilizing roles in food web dynamics, knowledge of sym‐ patric reef predator trophodynamics and resource partitioning is im‐ portant for predicting how reef communities will respond to change (Matich et al, 2011). We use a tri‐isotope ellipsoid approach to examine the isotopic niches of seven key teleost coral reef predator species to determine whether predator resource use varies 1) spatially and/or 2) intraspe‐ cifically, and 3) whether their isotopic niches overlap

| MATERIALS AND METHODS
| DISCUSSION
Findings
CONFLICT OF INTEREST
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