DOI: 10.5061/dryad.4gk50rc
title: Data from: Alternative functional strategies and altered carbon pathways facilitate broad depth ranges in coral-obligate reef fishes

description: Spatial refuges in peripheral habitats will become increasingly important
 for species persistence as climate change and other disturbances
 progressively impact habitat quality and assemblage compositions. However,
 the capacity for persistence will be determined in part by
 species‐specific abilities to absorb costs related to altered or decreased
 quantities and quality of resources at range peripheries. We compared
 variations in dietary strategies and energy acquisition trade‐offs along
 depth gradients in two obligate corallivores that differ in level of diet
 specialization. We also assessed depth‐related changes in energy pathways
 and energy content of their mixotrophic prey. We found no changes in
 feeding effort or total resource availability (total coral cover) towards
 deep range margins, but availability of the preferred resource (Acropora
 coral) decreased. While both species selectively targeted Acropora, the
 more specialized species (Chaetodon baronessa) exhibited limited feeding
 plasticity along the depth gradient. The degree of selectivity towards the
 preferred coral increased rather than decreased with depth, being 40 times
 greater than expected, given availability, at their range periphery. In
 contrast, the generalist's diet (Chaetodon octofasciatus) varied
 greatly in response to changes in resource availability with depth.
 Unexpectedly, the energy content of Acropora did not decline with depth,
 likely due to increased coral heterotrophy in deeper water, indicated by
 shifts in their molecular isotope geochemistry. This shift was accompanied
 by a 20% increase in plankton‐sourced carbon in the muscle tissue of
 deep‐resident fish, despite no observations of direct feeding on plankton
 food sources. Our results indicate that deep ranges in coral‐obligate reef
 fishes are supported by multiple mechanisms of trophic versatility in both
 the fish and corals. This nutritional plasticity likely serves a
 compensatory role in the resilience and eventual adaptation of organisms
 at their range peripheries. For species vulnerable to increasing
 anthropogenic impacts at range cores, variable and multi‐trophic
 functional responses can act to buffer against costs and increase the
 refuge potential of range peripheries. Specialist consumers may also be
 supported indirectly at range margins via trophic plasticity within their
 preferred prey.
description: AcroBSIABulk Stable Isotopes (13C, 15N) of shallow (&lt;5m) and deep (30-40m) corals from the genus Acropora and with Hispidose morphology.AcroLipidRPercent weight of lipids from coral tissues of the genus Acropora, collected along a depth gradients from 0-40m in Kimbe Bay, Papua New Guinea.ChaetAcroSelecFeeding selectivity data along a depth gradient from 0-30m for two obligate coral feeding butterflyfishes (Chaetodon baronessa and Chetodon octofasciatus) in Kimbe Bay, PNG.ChaetDietOverlapChristinesData on the among depth diet overlap of two obligate coral feeding butterflyfish species (Chaetodon baronessa and Chaetodon octofasciatus) on Christines Reef in Kimbe Bay, Papua New Guinea.ChristinesPreyCoralCover2015The percent cover of coral genera along a depth gradient from 0-30m on Christines Reef, Kimbe Bay, PNG.KimbeBayDepthCoralCover2013The percent cover of all hard corals and corals of the genus Acropora along a depth gradient from 0-40m and across nine reefs in Kimbe Bay, PNG.CSIAAAMixingModelDataData for mixing models of baseline carbon contributions to Acropora corals and Chaetodon baronessa in shallow (&lt;5m) and deep (20-40m) depths in Kimbe Bay, PNG. Compound Specific Stable Isotope Analyises of Amino Acids.