Two distinct host-parasite associations mediate seasonal ecosystem linkages

Area of Science:

• Ecology
• Parasitology
• Evolutionary Biology

Background:

• Nematomorph parasites manipulate terrestrial arthropods, driving them into aquatic ecosystems.
• This process creates a significant prey subsidy for stream salmonids, facilitating cross-ecosystem energy transfer.
• The diversity of nematomorph-arthropod interactions suggests potential mediation of energy flow magnitude and timing.

Purpose of the Study:

• Investigate if distinct nematomorph phylogenetic groups utilize different arthropod hosts.
• Determine if these associations mediate seasonal prey subsidies for stream salmonids.
• Understand the role of host-parasite specificity in cross-ecosystem energy flow.

Main Methods:

• Molecular-based diagnoses to identify nematomorph species and their hosts.
• Field observations to link host types to seasonal salmonid prey availability.
• Phylogenetic analysis of nematomorph-arthropod associations.

Main Results:

• Molecular diagnoses revealed *Gordionus* infecting ground beetles and *Gordius* infecting orthopterans.
• Ground beetle hosts provided a prey subsidy in spring; orthopteran hosts provided one in autumn.
• Two distinct nematomorph-arthropod associations ensure a year-round parasite-mediated prey subsidy.

Conclusions:

• Phylogenetic variation in nematomorph-arthropod associations influences the seasonality of cross-ecosystem energy subsidies.
• Parasite manipulation of distinct host groups can sustain energy flow across seasons.
• This mechanism highlights the widespread ecological importance of host-parasite specificity in mediating ecosystem dynamics.