No 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

No abstract

Ornamental bill color is postulated to function as a condition‐dependent signal of individual quality in a variety of taxonomically distant bird families. Most red, orange, and yellow bill colors are derived from carotenoid pigments, and carotenoid deposition in ornamentation may trade off with their use as immunostimulants and antioxidants or with other physiological functions. Several studies have found that bill color changes in response to physiological perturbations, but how quickly such changes can occur remains unclear. We tested the hypothesis that carotenoid‐based orange bill color of American goldfinches Spinus tristis responds dynamically to rapid changes in physiological stress and reflects short‐term changes in condition. We captured male and female goldfinches and measured bill color in the field and again under captive conditions several hours later. The following day, the captive birds were injected with either immunostimulatory lipopolysaccharide (LPS) or a control saline and changes in bill color were measured over a five day period. Yellow saturation of the bill decreased within 6.5 h between the field and captivity measures on the first day, presumably in response to capture stress. Over the longer experimental period, bill hue and luminance decreased significantly, whereas saturation significantly increased in both LPS and control groups. Bill hue and luminance decreased significantly more in birds treated with LPS than in control birds. Among LPS treated birds, individuals expressing high bill color at the beginning of the experiment lost more color than ‘low‐color’ birds, but still retained higher color at the end of the experiment, suggesting that birds that invest heavily in bill coloration are able to sustain high costs in the face of a challenge. Bill color change may have resulted from rapid reallocation of carotenoids from ornamentation to immune function. However, the complex shifts in bill color over time suggest that bill color may be influenced by multiple carotenoid compounds and/or changes in blood flow or chemistry in vessels just beneath the translucent keratinized outer layer of the bill. We conclude that bill color is a dynamic, condition‐dependent trait that strategically and reliably signals short‐term fluctuations in physiological condition.