Context-dependent parasite infection affects trophic niche in populations of sympatric stickleback species

Abstract

How parasites alter host feeding ecology remains elusive in natural populations. A powerful approach to investigate the link between infection and feeding ecology is quantifying unique and shared responses to parasite infection in related host species within a common environment. Here, 9 pairs of sympatric populations of the three-spined and nine-spined stickleback fishes were sampled across a range of freshwater and brackish habitats to investigate how parasites alter host feeding ecology: (i) biotic and abiotic determinants of parasite community composition, and (ii) to what extent parasite infection correlates with trophic niche specialization of the 2 species, using stable isotope analyses (δ15N and δ13C). It was determined that parasite community composition and host parasite load varied among sites and species and were correlated with dissolved oxygen. It was also observed that the digenean Cyathocotyle sp.'s abundance, a common directly infecting parasite with a complex life cycle, correlated with host δ13C in a fish species-specific manner. In 6 sites, correlations were found between parasite abundance and their hosts' feeding ecology. These effects were location-specific and occasionally host species or host size-specific. Overall, the results suggest a relationship between parasite infection and host trophic niche which may be an important and largely overlooked ecological factor. The population specificity and variation in parasite communities also suggest this effect is multifarious and context-dependent.

Host habitat rather than evolutionary history explains gut microbiome diversity in sympatric stickleback species

“…This was also confirmed by the higher number of ASVs in the nine-spined stickleback ( Figure 2 ). Higher microbial diversity suggests broader niche use in the nine-spined stickleback, which is consistent with the observation that nine-spined stickleback occupies a slightly higher trophic position ( Thorburn et al, 2022 ). A comparable study by Fietz et al (2018) observed a similar alpha diversity pattern in sand lance fishes ( Ammodytes tobianus and Hyperoplus lanceolatus ) from the Baltic Sea, with higher alpha diversity in A. tobianus .…”

“…The three-spined stickleback ( Gasterosteus aculeatus Linnaeus, 1758) and the nine-spined stickleback ( Pungitius pungitius Linnaeus, 1758) are important model organisms for the study of natural selection and adaptive evolution ( Gibson, 2005 ; Raeymaekers et al, 2005 ; DeFaveri et al, 2012 ; Feulner et al, 2013 ; Merilä, 2013 ; Fang et al, 2021 ). Both species diverged around 26 million years ago ( Varadharajan et al, 2019 ), but have overlapping habitat requirements ( Zander, 1990 ), diet preferences ( Hart, 2003 ) and parasite communities ( Raeymaekers et al, 2008 ; Thorburn et al, 2022 ). Studies in three-spined stickleback have identified several environmental and host-specific factors that correlate with the diversity and community structure of the gut microbiota.…”

“…Three-spined and nine-spined stickleback populations in Belgium and Netherlands co-occur in a wide range of habitats, including estuaries, creeks, rivers, ditches, and ponds ( Raeymaekers et al, 2017 ; Bal et al, 2021 ; Thorburn et al, 2022 ). In this part of their distribution range, both species differ markedly in the strength and nature of local adaptation, where brackish water and freshwater populations show stronger morphological and genomic differentiation in the three-spined stickleback than in the nine-spined stickleback ( Raeymaekers et al, 2017 ; Bal et al, 2021 ).…”

Narrower isotopic niche size in fish infected by the intestinal parasitePomphorhynchussp. compared to uninfected ones

“…Interestingly, trophic niche use at the study sites showed different trends for infected and uninfected cohorts among chub populations. This suggests that parasite infection on niche specialization is context‐dependent (Thorburn et al ., 2022). There is mounting evidence that stress factors, other than parasite infection, can alter physiological performance and affect the interindividual variability of the isotopic signature (Karlson et al ., 2018).…”