Diverse host-parasite interactions mediate seasonal ecosystem linkages

Nematomorph parasites manipulate terrestrial arthropods, such as crickets
and ground beetles, to enter streams where the parasites reproduce. These
manipulated arthropods become a substantial prey subsidy for stream
salmonids, causing cross-ecosystem energy flow. Diverse
nematomorph-arthropod interactions are known to underlie the energy flow.
However, whether and how they can mediate the magnitude and temporal
attributes of energy flow remains largely unknown. Here, we investigated
whether distinct species or phylogenetic groups of nematomorphs
respectively manipulate different arthropod hosts, and how the diverse
nematomorph-arthropod interactions, if any, mediate seasonal prey subsidy
for stream salmonids. We found that distinct phylogenetic groups of
Gordionus and Gordius nematomorphs infected ground beetle and orthopteran
hosts, respectively. The Gordionus nematomorphs led their ground beetle
hosts to enter streams in spring, subsidizing salmonid individuals during
that season. By contrast, the Gordius nematomorphs manipulated
orthopterans in autumn, causing the prey subsidy for salmonid individuals
during that time. Maintaining the two distinct nematomorph-arthropod
interactions, thus, resulted in the parasite-mediated prey subsidy in both
spring and autumn in the study streams. Manipulative parasites are common,
and they often associate with a range of host lineages, suggesting that
similar effects of diverse host-parasite interactions on energy flow might
be widespread in nature.