Abstract
Ecological speciation – whereby an ancestral founder species diversifies to fill vacant niches – is a phenomenon characteristic of newly formed ecosystems. Despite such ubiquity, ecosystem-level effects of such divergence remain poorly understood. Here, we compared the trophic niche of European whitefish (Coregonus lavaretus) and their predators in a series of contrasting subarctic lakes where this species had either diversified into four ecomorphologically distinct morphs or instead formed monomorphic populations. We found that the trophic niche of whitefish was almost three times larger in the polymorphic than in the monomorphic lakes, due to an increase in intraspecific specialisation. This trophic niche expansion was mirrored in brown trout (Salmo trutta), a major predator of whitefish. This represents amongst the first evidence for ecological speciation directly altering the trophic niche of a predator. We suggest such mechanisms may be a common and important – though presently overlooked – factor regulating trophic interactions in diverse ecosystems globally.
Highlights
The integration of evolutionary biology and ecosystem science has recently been highlighted as one of the most underexplored areas in all of biology[1,2,3]
The isotopic niche of whitefish was considerably expanded in polymorphic systems, compared to monomorphic ones (Fig. 1), and proportional contributions of habitat-specific prey to the diet of the large sparsely-rakered (LSR) morph differed markedly between lake types (Fig. 2)
Increasing niche size was related to trophic diversification among morphs, which showed pronounced differences in terms of both mean littoral reliance, and mean trophic position across all three polymorphic lakes (Fig. 1). This was driven by increased individual specialization to specific littoral, pelagic or profundal habitats and associated diet in polymorphic populations (Fig. 1; Fig. 2; Table S4), rather than a greater inclusion of novel prey taxa, and the mean number of dietary items used by whitefish in both lake types was identical (14.67 in both cases; t4 = 0; p = 1)
Summary
The integration of evolutionary biology and ecosystem science has recently been highlighted as one of the most underexplored areas in all of biology[1,2,3]. The capacity for such processes to have ecosystem-level consequences is generally acknowledged, the potential for such effects to be obscured by natural complexity has been highlighted[5, 9, 11] Identifying how these eco-evolutionary mechanisms manifest across trophic levels is an important step towards explaining potential ecosystem-level responses. The capacity for bottom-up effects of ecological speciation in a secondary consumer has received little attention to date, in favour of a focus on top-down processes[8,9,10,11], but represents one of the major pathways by which evolutionary diversification may manifest within host ecosystems This is likely to be pronounced in relatively species-poor ecosystems, where predators have a limited selection of potential prey species. They are likely to show distinct, quantifiable responses to variability within their preferred prey, and may be prone to bottom-up influence in prey diversification
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
