Crossing incompatibility between Trichogramma minutum and T. platneri (Hymenoptera: Trichogrammatidae) : Implications for application in biological control

The two egg parasitoid species Trichogramma minutum Riley and T. platneri Nagarkatti are closely related. No morphological or molecular characters are known to distinguish them. Their treatment as distinct species rests on the absence of female offspring in between-species crosses. The current species definitions, which must be considered tentative, assume their natural ranges to differ, with T. minutum occurring east of the Rocky Mountains and T. platneri occurring to the west. Both species are used throughout North America for the biological control of moths in orchards and forests. They are available to growers and researchers through a large number of biological control suppliers. Because the species can only be identified after crosses with known cultures, it is likely that producers often cannot be sure of the identity of their wasps. Here we studied the causes of the lack of female offspring in the between-species crosses and what happened when one species is released for biological control in the native area of the other. Our results show that females in between-species crosses are inseminated and use the sperm to fertilize their eggs, but that these fertilized eggs die. In addition, females do not preferentially mate with males of their own species when exposed to conspecific and nonconspecific males. These results are used in a model to predict the effect of releasing the non-native species in the native area of the other species. This model shows that such introduction

Partial cytochrome oxidase II sequences distinguish the sibling species Trichogramma minutum Riley and Trichogramma platneri Nagarkatti

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The North American Trichogramma (Hymenoptera) : Trichogrammatidae parasitizing certain tortricidae (Lepidoptera) on apple and pear, with ITS2 DNA characterizations and description of a new species

Eleven species of Trichogramma are reported parasitizing tortricid eggs on apple and pear in North America. Codling moth, Cydia pomonella (L.), and oriental fruit moth, Grapholita molesta (Busck), were the primary pest species encountered. Species of the Trichogramma minutum complex were the dominant egg parasites in collections. One of the Trichogramma species, T. itsybitsi Pinto and Stouthamer, is new and is herein described. Species of Trichogramma collected are identified by their ITS2 DNA sequence

The utility of internally transcribed spacer 2 DNA sequences of the nuclear ribosomal gene for distinguishing sibling species of Trichogramma

The usefulness of the internally transcribed spacer 2 (ITS2) of the nuclear ribosomal gene complex is tested for providing taxonomic characters to identify Trichogramma species. The ITS2 sequences of a group of sibling species of the T. deion/T. pretiosum complexes were determined. A simple and precise identification key to the species of these assemblages was constructed using as taxonomic characters the size of the ITS2 and the difference in restriction length polymorphism of species with similarly sized ITS2. Individual wasps can be identified by amplification of their ITS2 with general primers, determining the size of the PCR product using standard agarose electrophoresis, followed in some species by a DNA-digestion with a restriction enzyme. Because this system works well for a number of closely related species we are hopeful that similar PCR-based identification can be extended to all species of the genus once their ITS2 sequences have been determined. The advantage of this identification system over the morphology-based system is that non-specialists are able to quickly and cheaply identify individual specimens. In addition, species specific primers were tested for the two most common species of these groups (i.e. T. pretiosum and T. deion). These primers can be used either as a direct identification tool or as a method to confirm the identification using the general key. The phylogeny of this group of wasps was also analyzed based on the ITS2 sequence