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Trophic structure in a seabird host-parasite food web: insights from stable isotope analyses.

Gómez-Díaz E, González-Solís J - PLoS ONE (2010)

Bottom Line: All ectoparasite species showed a significant enrichment in delta(15)N relatively to the host tissue consumed (discrimination factors ranged from 2 to 5 per thousand depending on the species).Our findings illustrate the influence of both ectoparasite and host trophic ecology in the isotopic structuring of the Calonectris ectoparasite community.This study highlights the potential of stable isotope analyses in disentangling the nature and complexity of trophic relationships in symbiotic systems.

View Article: PubMed Central - PubMed

Affiliation: Institut de Recerca de la Biodiversitat i Departament Biologia Animal (Vertebrats), Universitat de Barcelona, Barcelona, Spain. elegomez@ub.edu

ABSTRACT
Ecological studies on food webs rarely include parasites, partly due to the complexity and dimensionality of host-parasite interaction networks. Multiple co-occurring parasites can show different feeding strategies and thus lead to complex and cryptic trophic relationships, which are often difficult to disentangle by traditional methods. We analyzed stable isotope ratios of C ((13)C/(12)C, delta(13)C) and N ((15)N/(14)N, delta(15)N) of host and ectoparasite tissues to investigate trophic structure in 4 co-occurring ectoparasites: three lice and one flea species, on two closely related and spatially segregated seabird hosts (Calonectris shearwaters). delta(13)C isotopic signatures confirmed feathers as the main food resource for the three lice species and blood for the flea species. All ectoparasite species showed a significant enrichment in delta(15)N relatively to the host tissue consumed (discrimination factors ranged from 2 to 5 per thousand depending on the species). Isotopic differences were consistent across multiple host-ectoparasite locations, despite of some geographic variability in baseline isotopic levels. Our findings illustrate the influence of both ectoparasite and host trophic ecology in the isotopic structuring of the Calonectris ectoparasite community. This study highlights the potential of stable isotope analyses in disentangling the nature and complexity of trophic relationships in symbiotic systems.

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Isotopic enrichment in Calonectris ectoparasites.Mean Δ15N and Δ13C discrimination factors among ectoparasite tissues and host tissues (mean colony values ± Standard Error).
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pone-0010454-g002: Isotopic enrichment in Calonectris ectoparasites.Mean Δ15N and Δ13C discrimination factors among ectoparasite tissues and host tissues (mean colony values ± Standard Error).

Mentions: Finally we examined the enrichment, as indicated by the discrimination factor of each ectoparasite species relative to the host tissue consumed (i.e., mean values across multiple breeding sites) (Fig. 2, Table 1). All ectoparasite species were significantly enriched in both carbon and nitrogen isotope values relative to the host tissue consumed (t-test, all P<0.001). Nitrogen discrimination factors ranged from 2 to 5 ‰ depending on the ectoparasite species, host tissue type and breeding locality (Table 1), but was generally greater for lice (Δ15Nfeather-Ha = 4.12±1.49, Δ15Nfeather-Ae = 3.10±1.01, Δ15Nfeather-Sp = 3.81±1.11, Δ15Nblood-Xg: 2.69±0.62). On the contrary, lice appeared relatively low carbon enriched (0.45–0.75 ‰) compared to the flea species, which showed the greatest carbon discrimination factor (Δ13Cblood-Xg: 1.02±0.51) (Table 1). Overall, carbon and nitrogen discrimination factors differed among ectoparasite species (Δ15N: F3,37 = 3.45, P = 0.027; Δ13C: F3,37 = 2.73, P = 0.059) (Fig. 2). However, post-hoc Bonferroni tests indicated significant differences only among some lice and the flea species (pairwise comparisons: Δ15N Ha-Δ15N Xg: D = 1.43, P = 0.006; Δ13C Ae-Δ13C Xg: D = −0.57, P = 0.068).


Trophic structure in a seabird host-parasite food web: insights from stable isotope analyses.

Gómez-Díaz E, González-Solís J - PLoS ONE (2010)

Isotopic enrichment in Calonectris ectoparasites.Mean Δ15N and Δ13C discrimination factors among ectoparasite tissues and host tissues (mean colony values ± Standard Error).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2864259&req=5

pone-0010454-g002: Isotopic enrichment in Calonectris ectoparasites.Mean Δ15N and Δ13C discrimination factors among ectoparasite tissues and host tissues (mean colony values ± Standard Error).
Mentions: Finally we examined the enrichment, as indicated by the discrimination factor of each ectoparasite species relative to the host tissue consumed (i.e., mean values across multiple breeding sites) (Fig. 2, Table 1). All ectoparasite species were significantly enriched in both carbon and nitrogen isotope values relative to the host tissue consumed (t-test, all P<0.001). Nitrogen discrimination factors ranged from 2 to 5 ‰ depending on the ectoparasite species, host tissue type and breeding locality (Table 1), but was generally greater for lice (Δ15Nfeather-Ha = 4.12±1.49, Δ15Nfeather-Ae = 3.10±1.01, Δ15Nfeather-Sp = 3.81±1.11, Δ15Nblood-Xg: 2.69±0.62). On the contrary, lice appeared relatively low carbon enriched (0.45–0.75 ‰) compared to the flea species, which showed the greatest carbon discrimination factor (Δ13Cblood-Xg: 1.02±0.51) (Table 1). Overall, carbon and nitrogen discrimination factors differed among ectoparasite species (Δ15N: F3,37 = 3.45, P = 0.027; Δ13C: F3,37 = 2.73, P = 0.059) (Fig. 2). However, post-hoc Bonferroni tests indicated significant differences only among some lice and the flea species (pairwise comparisons: Δ15N Ha-Δ15N Xg: D = 1.43, P = 0.006; Δ13C Ae-Δ13C Xg: D = −0.57, P = 0.068).

Bottom Line: All ectoparasite species showed a significant enrichment in delta(15)N relatively to the host tissue consumed (discrimination factors ranged from 2 to 5 per thousand depending on the species).Our findings illustrate the influence of both ectoparasite and host trophic ecology in the isotopic structuring of the Calonectris ectoparasite community.This study highlights the potential of stable isotope analyses in disentangling the nature and complexity of trophic relationships in symbiotic systems.

View Article: PubMed Central - PubMed

Affiliation: Institut de Recerca de la Biodiversitat i Departament Biologia Animal (Vertebrats), Universitat de Barcelona, Barcelona, Spain. elegomez@ub.edu

ABSTRACT
Ecological studies on food webs rarely include parasites, partly due to the complexity and dimensionality of host-parasite interaction networks. Multiple co-occurring parasites can show different feeding strategies and thus lead to complex and cryptic trophic relationships, which are often difficult to disentangle by traditional methods. We analyzed stable isotope ratios of C ((13)C/(12)C, delta(13)C) and N ((15)N/(14)N, delta(15)N) of host and ectoparasite tissues to investigate trophic structure in 4 co-occurring ectoparasites: three lice and one flea species, on two closely related and spatially segregated seabird hosts (Calonectris shearwaters). delta(13)C isotopic signatures confirmed feathers as the main food resource for the three lice species and blood for the flea species. All ectoparasite species showed a significant enrichment in delta(15)N relatively to the host tissue consumed (discrimination factors ranged from 2 to 5 per thousand depending on the species). Isotopic differences were consistent across multiple host-ectoparasite locations, despite of some geographic variability in baseline isotopic levels. Our findings illustrate the influence of both ectoparasite and host trophic ecology in the isotopic structuring of the Calonectris ectoparasite community. This study highlights the potential of stable isotope analyses in disentangling the nature and complexity of trophic relationships in symbiotic systems.

Show MeSH
Related in: MedlinePlus