Showing papers on "Uroleucon published in 2000"

Cospeciation between bacterial endosymbionts (Buchnera) and a recent radiation of aphids (Uroleucon) and pitfalls of testing for phylogenetic congruence.

Abstract: Previous studies of phylogenetic congruence between aphids and their symbiotic bacteria (Buchnera) sup- ported long-term vertical transmission of symbionts. However, those studies were based on distantly related aphids and would not have revealed horizontal transfer of symbionts among closely related hosts. Aphid species of the genus Uroleucon are closely related phylogenetically and overlap in geographic ranges, habitats, and parasitoids. To examine support for congruence of phylogenies of Buchnera and Uroleucon, sequences from four mitochondrial, one nuclear, and one endosymbiont gene (trpB) were obtained. Congruence of phylogenies based on pooled aphid genes with phylogenies based on trpB was highly significant: Most nodes resolved by trpB corresponded to nodes resolved by the pooled aphid genes. Furthermore, no nodes were both inconsistent between the trees and strongly supported in both trees. Two kinds of analyses testing the null hypothesis of perfect congruence between pairwise combinations of datasets and tree topologies were performed: the Kishino-Hasegawa test and the likelihood-ratio test. Both tests indicated significant disagreement among most pairwise combinations of mitochondrial, nuclear, and symbiont datasets. Because rampant recombination among mitochondrial genomes of different aphid species is unlikely, inaccurate assumptions in the evolutionary models underlying these tests appear to be causing the hypothesis of a shared history to be incorrectly rejected. Moreover, trpB was more consistent with the aphid genes as a set than any single aphid gene was with the others, suggesting that the symbionts show the same phylogeny as the aphids. Overall, analyses support the interpretation that symbionts and aphids have undergone strict cospeciation, with no horizontal transmission of symbionts even among closely related, ecologically similar aphid hosts.

Newly established and rarely collected aphids (Homoptera: Aphididae) in Florida and the southeastern United States.

Abstract: Several aphid species are reported as newly established in Florida and/or the southeastern United States, including Acyrthosiphon kondoi Shinji, Aphis amaranthi Holman, Brachycaudus helichrysi (Kaltenbach), Coloradoa achilleae Hille Ris Lambers, Hyadaphis coriandri (Das), Hyperomyzus carduellinus (Theobald), Melanaphis sp., Schizaphis rotundiventris (Signoret), Shivaphis celti Das, Takecallis arundicolens (Clarke), and Toxoptera citricida (Kirkaldy). Further establishment records are reported for Trichosiphonaphis polygoni (van der Goot) that was previously reported from a few counties in Florida and Georgia. Recent Florida finds are reported for three native species, including Aphis minima Tissot, Kaltenbachiella ulmifusa (Walsh & Riley), and Uroleucon elephantopicola Robinson. Identification information is provided for newly introduced exotic species.

Electrical Penetration Graph analysis reveals population differentiation of host‐plant probing behaviors within the aphid species Uroleucon ambrosiae

Abstract: Uroleucon ambrosiae collected from the eastern and the southwestern United States were studied in relation to host-plant probing. In the field, eastern aphids are highly specific on Ambrosia trifida, while southwestern aphids feed on Ambrosia trifida plus many other species in the family Asteraceae. Electrical penetration graphs of insects on the principal host, A. trifida, and an additional host of southwestern populations, Heterotheca subaxillaris, revealed regional differentiation in host-associated aphid behaviors, specifically in the first phase of subcuticular probing, and in phloem finding activities. Eastern aphids used A. trifida more efficiently than southwestern aphids, but were demonstrably less vigorous in their probing activities on H. subaxillaris.

Screening of safflower germplasm accessions to aphid, Uroleucon compositae Theobald.

Abstract: A total of 332 safflower gennplasm accessions including three checks were evaluated for resistance to aphid, UroJeucon compositae Theobald Results revealed that, only two entries viz, nus 568 and nus 945 were found to be highly tolerant by recording foliage drying grade of one, while forty eight entries recorded foliage drying grade 2 indicating their tolerant reaction to aphids