Host plant associated genetic differentiation is a common phenomenon in phytophagous insects, but the degree to which such associations sequentially drive diversification at higher trophic levels is not as well understood. A recent study examining neutral molecular markers in Hyalopterus aphids revealed that genetic structure in this genus is strongly determined by primary host plant use (Prunus spp.). In this paper, we take a similar approach to determine whether this host plant specificity has affected genetic structure in the parasitoid Aphidius transcaspicus, an important natural enemy of Hyalopterus spp. in the Mediterranean. Mitochondrial DNA (428 bp) and seven microsatellite loci were examined in parasitoids collected from aphid populations on almond, apricot, peach and plum trees from Spain and Greece. In contrast to the previous findings for Hyalopterus from the same regions, here we find no evidence for host associated diversification in A. transcaspicus at the species level or below, though geographic structure between regional populations is exceptionally high. These findings have several implications for our understanding of the ecology and evolution of A. transcaspicus as well as for its use as a biological control agent for Hyalopterus, suggesting that a consideration of host plant specificity may be less critical than factors such as climatic suitability or geographic origins of invasive populations.

The Mediterranean parasitoid Aphidius transcaspicus is currently under investigation as a potential biological control agent for the mealy plum aphid, Hyalopterus pruni, in California. To better understand the biology of this parasitoid, including the potential existence of distinct strains or geographic races, we have developed a set of nine di‐ and trinucleotide repeat microsatellite markers. These markers were examined for variability in individuals from throughout the geographic distribution of A. transcaspicus, and we found between three and 19 alleles per locus. These are the first loci developed for A. transcaspicus and they will be of value in studying the population structure of this potential biocontrol agent and for future diagnostics.

We developed 31 novel, polymorphic microsatellite loci in the marbled murrelet (Brachyramphus marmoratus), a critically endangered seabird. Variability was tested on 15 individuals from the Santa Cruz, California population, with each locus characterized by two to 12 alleles. Observed levels of heterozygosity ranged from 0.13 to 0.93. These loci provide a valuable means of assessing the population structure and demographic parameters of this species, which may be critical to its conservation across a fragmented habitat.

Hyalopterus pruni is an invasive aphid pest in California. To study the population biology of this pest both in California and its native Mediterranean region, we have developed 11 di‐ and tri‐nucleotide repeat microsatellite markers. Each locus amplified in individuals representing the full range of geographical regions and host plants where Hyalopterus is found. Polymorphism was high, ranging from six to 22 alleles per locus in the individuals screened. These loci represent the first microsatellites developed for Hyalopterus and they should be of great value in studying the invasion biology and population structure of this insect pest.