Separation of realized ecological niche axes among sympatric tilefishes provides insight into potential drivers of co‐occurrence in the NW Atlantic. Issue 19 (22nd September 2020)

• Record Type: Journal Article
• Authors: Olin, Jill A.; Shipley, Oliver N.; Cerrato, Robert M.; Nitschke, Paul; Magen, Cédric; Frisk, Michael G.
• Is Part Of: Ecology and evolution. Volume 10:Issue 19(2020)
• Page Start: 10886
• Page End: 10898
• Publication Date: 2020-09-22
• Subjects: Caulolatilus microps -- continental shelf -- habitat segregation -- Lopholatilus chamaeleonticeps -- resource use -- spatial variability -- stable isotope ratios; Ecology -- Periodicals; Evolution -- Periodicals; 577.05
• DOI: 10.1002/ece3.6745
• Languages: English
• ISSNs: 2045-7758

Abstract

Abstract: Golden and Blueline Tilefish ( Lopholatilus chamaeleonticeps and Caulolatilus microps ) are keystone taxa in northwest (NW) Atlantic continental shelf‐edge environments due to their biotic (trophic‐mediated) and abiotic (ecosystem engineering) functional roles combined with high‐value fisheries. Despite this importance, the ecological niche dynamics (i.e., those relating to trophic behavior and food‐web interactions) of these sympatric species are poorly understood, knowledge of which may be consequential for maintaining both ecosystem function and fishery sustainability. We used stable isotope ratios of carbon (δ 13 C) and nitrogen (δ 15 N) to build realized ecological niche hypervolumes to serve as proxies for diet and production use patterns of L . chamaeleonticeps and C. microps . We hypothesized that: (a) species exhibit ontogenetic shifts in diet and use of production sources; (b) species acquire energy from spatially distinct resource pools that reflect a sedentary life‐history and differential use of the continental shelf‐edge; and (c) species exhibit differentiation in one or more measured niche axes. We found evidence for ontogenetic shifts in diet (δ 15 N) but not production source (δ 13 C) in both species, suggesting a subtle expansion of measured ecological niche axes. Spatial interpolation of stable isotope ratios showed distinct latitudinal gradients; for example, individuals were 13 C enriched in northern and 15 N enriched in southern regions, supporting the assertion that tilefish species acquire energy from regional resource pools. High isotopic overlap was observed among species (≥82%); however, when hypervolumes included depth and region of capture, overlap among species substantially decreased to overlap estimates of 15%–77%. This suggests that spatial segregation could alleviate potential competition for resources among tilefish species inhabiting continental shelf‐edge environments. Importantly, our results question the consensus interpretation of isotopic overlap estimates as representative of direct competition among species for shared resources or habitats, instead identifying habitat segregation as a possible mechanism for coexistence of tilefish species in the NW Atlantic. Abstract : We combine stable isotope ratios of carbon and nitrogen with environmental data to evaluate ecological niche dynamics of two ecologically and economically important deep‐water tilefish species. Through sampling individuals across much of their geographic range, we find evidence for limited movement of tilefish, as well as subtle niche expansion through ontogeny. Additionally, we find that tilefish use similar prey resource pools, but separate on fine‐scale depth preferences; a potential mechanism to alleviate interspecific competition in resource‐limited systems. Our analyses provide insight into the potential drivers of tilefish co‐occurrence, knowledge that may be consequential for maintaining both ecosystem function and fishery sustainability.