U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska
Document Type
Article
Date of this Version
2006
Abstract
We investigated the differentiation and reproductive isolation among different geographic populations of Gonatocerus morrilli, egg parasitoids of the glassy-winged sharpshooter (Homalodisca coagulata), to confirm previous observations that there may exist a cryptic species complex or a new species. Two mitochondrial genes [cytochrome oxidase subunits I (COI) and II (COII)] and the internal transcribed spacer region 2 (ITS2) of several individuals per population were sequenced. G. morrilli populations from Texas (TX), Florida (FL), California (CA), and an outgroup (G. ashmeadi) were analyzed. For comparison, a population from Argentina (G. annulicornis) morphologically similar to G. morrilli was also included. For all three sequence fragments, percentage sequence divergence (%D) demonstrated that both the TX and FL populations (TX/FL) were closely related and therefore determined to be the same species; in contrast, the %D between TX/FL and CA fell within the range of the outgroup, making the CA population a new species or sp. n. Neighbor-joining distance trees also clustered the TX/FL and CA populations or species into two well supported distinctive clades. The near G. morrilli sp. n. was more closely related to G. annulicornis than to the TX/FL species. Mating studies demonstrated that the populations or species from CA and TX were reproductively incompatible, producing no female offspring in both direct and reciprocal crosses; whereas, the heterogamic crosses between TX and FL produced fertile offspring and relative compatibility indices similar to the homogamic crosses. Unidirectional cytoplasmic incompatibility was ruled out as a cause for the lack of reproduction since both males and females were infected in equal portions with Wolbachia.
Comments
Published in Biological Control 38 (2006) 282–293.