Phylogenetics and evolution of the aphid genus Uroleucon based on mitochondrial and nuclear DNA sequences

Abstract

The genus Uroleucon, and the related genus Macrosiphoniella, represent a large Tertiary radiation of aphids, with a total of about 300 species distributed throughout the world, primarily on host plant species in the family Asteraceae. A molecular phylogenetic study was conducted to identify major clades within Uroleucon and to address the cladistic validity of current subgeneric categories, the evolution of host plant associations, the age of origin, and intercontinental movements in this genus. The seventeen study species included members of the three major subgenera of Uroleucon, species from Europe and North America, one member of Macrosiphoniella, and two outgroups. Data consisted of DNA sequences for three mitochondrial regions and the nuclear gene EF1alpha, for a total of 4287 sites. Nodes supported strongly in both parsimony and maximum likelihood analyses suggest that: (1) Nearctic Uromelan are a monophyletic group branching near the base of the genus and not related to European Uromelan, (2) the New World subgenus Lambersius is possibly monophyletic but is not a tightly related group and is not closely related to other North American species, and (3) Nearctic members of subgenus Uroleucon are a closely related monophyletic group not allied with Nearctic Uromelan or Lambersius. Instead they represent a separate colonization by an Old World ancestor, as they are nested within a strongly supported clade containing European members of both subgenera Uroleucon and Uromelan. Neither of these subgenera is monophyletic. Molecular clock calculations, based on calibrations of mitochondrial divergences from other insects, suggest that Uroleucon + Macrosiphoniella is a relatively recent radiation, probably no more than 5±10 million years old. Although largely con®ned to Asteraceae, this clade did not radiate in parallel with its host plants. Rather, lateral movement between lineages of Asteraceae must have occurred repeatedly. R Systematic Entomology (1999) 24, 85±93

Transition Rates Between Specialization and Generalization in Phytophagous Insects

“…Using these data, extant groups of insects were coded as specialized or generalized in their patterns of host-plant use (see Table 1 for coding scheme). In fully resolved phylogenetic trees, branch lengths were set to one or assigned using methods Moran 1984, Moran et al 1999 Oreina leaf beetles allozymes 6, 6 feed on only one plant tribe Dobler et al 1996 Papilio butterflies mtDNA 12, 12 feed on only one tribe of host plant Sperling 1992Sperling , 1993Janz and Nylin 1998 Ophraella leaf beetles Dendroctonus bark beetles mtDNA 13, 6 feed on less than half of available hosts Kelley and Farrell 1998 Gonioctean leaf beetles mtDNA, allozymes 5, 10 feed on only one genus of host plant Mardulyn et al 1997 Graphium butterflies morphology 5, 7 feed on only one family of host plant Saigusa et al 1982;Scriber 1984;Miller 1987 Enchenopa treehoppers allozymes 2, 7 feed on only one species of host plant…”

Vertical Transmission of Biosynthetic Plasmids in Aphid Endosymbionts ( Buchnera )

“…In order to maximize the chance of detecting gene transfer among related Buchnera lineages, we sampled Buchnera of Uroleucon, a recent radiation of aphids that specialize on Asteraceae and often share host plants, habitats, secondary endosymbionts, and parasitoids (42,50). We compare phylogenies of chromosomal genes (dnaN and trpB) and plasmid-encoded genes (trpEG and leuABC) to test for plasmid transfer in this symbiont group.…”

“…Collection data, aphid DNA extractions, and standard PCR conditions were described previously (42). The PCR was used to amplify three gene regions of Buchnera: dnaN (1,107 bp), leuABC (3,919 bp), and trpEG (1,767 bp) (primer sequences available upon request).…”

The genusUroleucon(Hemiptera: Aphididae: Macrosiphini) in Argentina, with descriptions of five new species

“…But considering the conclusions by Carvalho et al (1998) and Moran et al (1999) In the future, another classification could be established, one congruent with the evolutionary history of the genus, based on morphologicalstatistical and molecular studies of species, which represent the different classical subgenera and different geographical origins (Eurasia, North America, South America). And so, these South American species may be grouped in a different subgenus, perhaps one that is exclusive for them.…”

“…Based on the analysis of several sequences of mitochondrial and nuclear DNA of several North American and European Uroleucon species, Moran et al (1999) established that (i) the North American species group of the subgenus Lambersius is possibly monophyletic but not a highly related group; (ii) the Nearctic Uromelan species are a monophyletic group, show a possible relationship with Nearctic Lambersius species, and are not related to European Uromelan species; and (iii) the Nearctic members of the genus Uroleucon are a closely related monophyletic group not allied with Nearctic Uromelan or Lambersius species; instead, they belong to a clade containing European members of both Uroleucon and Uromelan. They also wrote "Levels of pigmentation of coxae, anal plate and genital plate are strongly correlated yet independent of levels of pigmentation of other parts, such as cauda, abdominal scleroites, antennae and tibiae.…”