Spatial and temporal genetic structure at the fourth trophic level in a fragmented landscape

Abstract

A fragmented habitat becomes increasingly fragmented for species at higher trophic levels, such as parasitoids. To persist, these species are expected to possess life-history traits, such as high dispersal, that facilitate their ability to use resources that become scarce in fragmented landscapes. If a specialized parasitoid disperses widely to take advantage of a sparse host, then the parasitoid population should have lower genetic structure than the host. We investigated the temporal and spatial genetic structure of a hyperparasitoid (fourth trophic level) in a fragmented landscape over 50 Â 70 km, using microsatellite markers, and compared it with the known structures of its host parasitoid, and the butterfly host which lives as a classic metapopulation. We found that population genetic structure decreases with increasing trophic level. The hyperparasitoid has fewer genetic clusters (K ¼ 4), than its host parasitoid (K ¼ 15), which in turn is less structured than the host butterfly (K ¼ 27). The genetic structure of the hyperparasitoid also shows temporal variation, with genetic differentiation increasing due to reduction of the population size, which reduces the effective population size. Overall, our study confirms the idea that specialized species must be dispersive to use a fragmented host resource, but that this adaptation has limits.

The microbiome of theMelitaea cinxiabutterfly shows marked variation but is only little explained by the traits of the butterfly or its host plant

“…lanceolata ) and one specialist parasitoid species ( H . horticola ) (Nair et al ., ; Hanski et al ., ). The survey followed the general framework of the long‐term survey of the M .…”

Increased fluctuation in a butterfly metapopulation leads to diploid males and decline of a hyperparasitoid

“…The hyperparasitoid is dispersive [39] but individual wasps (approximately 6 mm in size) are dispersal limited and their distribution in the landscape is limited by the heterogeneity of host availability [35]. We estimated the butterfly larval abundances annually using the autumn survey [36] data from 2003 to 2016.…”

Wolbachiaincreases the susceptibility of a parasitoid wasp to hyperparasitism

“…stigmaticus is a specialist solitary parasitoid of endoparasitoids in M. cinxia caterpillars (Shaw et al, 2009). It is present throughout the Åland Islands, parasitizing 20-60% of H. horticola in many places (Nair et al, 2016). Extremely rarely it also parasitizes Cotesia melitaearum, which is the other specialist endoparasitoid of M. cinxia caterpillars (van Nouhuys and Hanski, 2005).…”

“…However, we know at least that wHho infects individuals throughout the wellmixed host population in Åland. It is found in the two mitotypes (less than 1% divergence between matrilines; Duplouy et al, 2015), across the different haplotypes of H. horticola (based on 14 microsatellite markers, A.D., unpublished observations), and across the landscape (Duplouy et al, 2015), where different haplotypes occur (Nair et al, 2016).…”