Contrasting fundamental and realized niches: two fishes with similar thermal performance curves occupy different thermal habitats

Allen-Ankins, Slade, and Stoffels, Rick J. (2017) Contrasting fundamental and realized niches: two fishes with similar thermal performance curves occupy different thermal habitats. Freshwater science, 36 (3). pp. 635-652.

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Human alteration of thermal regimes of freshwater ecosystems is creating an urgent need to understand how freshwater ectotherms will fare under different thermal futures. Two key questions are: 1) how well do the fundamental thermal niches of ectotherms map to their realized thermal niches, and 2) which axes of the fundamental thermal niche must be modeled to predict temperature-dependent fitness in real ecosystems? The first question is particularly challenging in riverine systems, where gradients in temperature are strongly confounded by gradients in other biotic and abiotic drivers. To address these questions, we compared the realized and fundamental thermal niches of 2 congeneric riverine fish: Gadopsis marmoratus and Gadopsis bispinosus. We characterized their realized thermal niches by examining their distributions in relation to environmental temperature at multiple scales. We characterized their fundamental thermal niches by doing laboratory experiments on the thermal sensitivity of swimming performance and metabolic rates, particularly aerobic scope. The distributions of the 2 species supported the idea that they have different realized thermal niches, with G. bispinosus occupying cooler habitats than G. marmoratus. Despite this, we detected no significant differences in the shapes of thermal performance curves defining 2 axes of their fundamental niches: swimming performance and aerobic scope. Our results suggest that either the distributions of these 2 species are driven by factors other than temperature or that swimming performance and aerobic scope were not suitable proxies of their fundamental thermal niches. Our study shows that modeling the thermal niches of ectotherms along the river continuum is not straightforward. If we are to forecast effects of thermal futures effectively and efficiently, we must do more to decipher the relative influence of temperature and other abiotic drivers on the fitness of riverine ectotherms.

Item ID: 59064
Item Type: Article (Research - C1)
ISSN: 2161-9565
Keywords: climate change, critical swimming velocity, freshwater fish, mechanistic niche modeling, streams, temperature
Copyright Information: © 2017 by The Society for Freshwater Science.
Funders: VCF Holsworth Local Heritage Trust, CSIRO Water for a Healthy Country Flagship
Date Deposited: 15 Nov 2019 02:12
FoR Codes: 31 BIOLOGICAL SCIENCES > 3103 Ecology > 310304 Freshwater ecology @ 60%
41 ENVIRONMENTAL SCIENCES > 4101 Climate change impacts and adaptation > 410102 Ecological impacts of climate change and ecological adaptation @ 20%
31 BIOLOGICAL SCIENCES > 3109 Zoology > 310907 Animal physiological ecology @ 20%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970106 Expanding Knowledge in the Biological Sciences @ 100%
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