Evidence for a single, ancient origin of a genus-wide alternative life history strategy.

Understanding the evolutionary origins and factors maintaining alternative life history strategies (ALHS) within species is a major goal of evolutionary research. While alternative alleles causing discrete ALHS are expected to purge or fix over time, one-third of the ~90 species of butterflies are polymorphic for a female-limited ALHS called Alba. Whether Alba arose once, evolved in parallel, or has been exchanged among taxa is currently unknown.

Hybrid incompatibility arises in a sequence-based bioenergetic model of transcription factor binding.

Postzygotic isolation between incipient species results from the accumulation of incompatibilities that arise as a consequence of genetic divergence. When phenotypes are determined by regulatory interactions, hybrid incompatibility can evolve even as a consequence of parallel adaptation in parental populations because interacting genes can produce the same phenotype through incompatible allelic combinations. We explore the evolutionary conditions that promote and constrain hybrid incompatibility in regulatory networks using a bioenergetic model (combining thermodynamics and kinetics) of transcriptional regulation, considering the bioenergetic basis of molecular interactions between transcription factors (TFs) and their binding sites.

Specific-gene studies of evolutionary mechanisms in an age of genome-wide surveying.

The molecular tools of genomics have great power to reveal patterns of genetic difference within or among species, but must be complemented by the mechanistic study of the genetic variants found if these variants' evolutionary meaning is to be well understood. Central to this purpose is knowledge of the organisms' genotype-phenotype-environment interactions, which embody biological adaptation and constraint and thus drive natural selection. The history of this approach is briefly reviewed.

A genetic polymorphism evolving in parallel in two cell compartments and in two clades.

Background: The enzyme phosphoenolpyruvate carboxykinase, PEPCK, occurs in its guanosine-nucleotide-using form in animals and a few prokaryotes. We study its natural genetic variation in Colias (Lepidoptera, Pieridae). PEPCK offers a route, alternative to pyruvate kinase, for carbon skeletons to move between cytosolic glycolysis and mitochondrial Krebs cycle reactions.

Evolutionary genomics of Colias Phosphoglucose Isomerase (PGI) introns.

Little is known of intron sequences' variation in cases where eukaryotic gene coding regions undergo strong balancing selection. Phosphoglucose isomerase, PGI, of Colias butterflies offers such a case. Its 11 introns include many point mutations, insertions, and deletions.

Emergence of complex haplotypes from microevolutionary variation in sequence and structure of Colias phosphoglucose isomerase.

A molecular evolutionary explanation of natural genetic variation requires analysis of specific variants' evolutionary dynamics. To pursue this for phosphoglucose isomerase (PGI) of Colias butterflies, whose polymorphism is maintained by strong natural selection, we assembled a large data set of wild haplotypes, highly variable at the amino acid and DNA levels. The most common electrophoretic, i.

A mitochondrial-DNA-based phylogeny for some evolutionary-genetic model species of Colias butterflies (Lepidoptera, Pieridae).

We study the phylogenetic relationships among some North American Colias ("sulfur") butterflies, using mitochondrial gene sequences (ribosomal RNA, cytochrome oxidase I+II) totaling about 20% of the mitochondrial genome. We find that (1) the lowland species complex shows a branching order different from earlier views; (2) several montane and northern taxa may be more distinct than in earlier views; (3) one morphologically conservative Holarctic assemblage, C. hecla, is differentiated at the molecular-genetic level into at least three taxa which occupy distinct positions in the phylogeny and are sisters to diverse other taxa.

From DNA to fitness differences: sequences and structures of adaptive variants of Colias phosphoglucose isomerase (PGI).

Colias eurytheme butterflies display extensive allozyme polymorphism in the enzyme phosphoglucose isomerase (PGI). Earlier studies on biochemical and fitness effects of these genotypes found evidence of strong natural selection maintaining this polymorphism in the wild. Here we analyze the molecular features of this polymorphism by sequencing multiple alleles and modeling their structures.

Thermal physiological ecology of Colias butterflies in flight.

As a comparison to the many studies of larger flying insects, we carried out an initial study of heat balance and thermal dependence of flight of a small butterfly (Colias) in a wind tunnel and in the wild.Unlike many larger, or facultatively endothermic insects, Colias do not regulate heat loss by altering hemolymph circulation between thorax and abdomen as a function of body temperature. During flight, thermal excess of the abdomen above ambient temperature is weakly but consistently coupled to that of the thorax.

Population structure of pierid butterflies IV. Genetic and physiological investment in offspring by male Colias.

Population structure encompasses all the rules by which a population's gametes come together, including genetic and physiological investment in offspring. We document female use of nutrients donated by males at mating, and complete sperm precedence, in Colias eurytheme Boisduval. The effect of these phenomena on the population structure of this species is discussed.

Individual variation in oviposition preference in the butterfly, Colias eurytheme.

We examined intra-population variation in oviposition preference in the pierid butterfly, Colias eurytheme. Females' preferences were tested in the laboratory, using two-way choice tests between the potential hosts, alfalfa and vetch. There were consistent differences in oviposition preference among females within a population.

Population structure of pierid butterflies : II. A "Native" population of Colias philodice eriphyle in Colorado.

The structure of a bivoltine, discrete-generation population of Colias philodice eriphyle, occurring in relatively undisturbed habitat, has been examined by mark-release-recapture techniques. The population's general ecology is briefly discussed. Males eclose before females as in other Colias, and a measure of physical wear on adults is related to age of individuals and to the overall position of a sample in the flight period, again as in other Colias.

Population structure of pierid butterflies : I. Numbers and movements of some montane Colias species.

The numbers, dispersal behavior, aging and residence, and Wrightian neighborhood configurations of three species of Colias butterflies have been studied in central Colorado, using mark-release-recapture techniques as major tools. All populations studied have nonoverlapping generations and mature one brood each year. A brief general review of these species' autecology is given.

Nectar resource use by Colias butterflies : Chemical and visual aspects.

Nectar foraging preferences of Colias butterflies in two different mountain ecosystems are examined with respect to plant distribution, nectar quantity, carbohydrate (and amino acid) content of nectar, and visual pattern of the plants utilized and avoided. Colias, and apparently numerous other small, ectothermic, low-energy-demand pollinators, "patronize" plants producing relatively dilute nectars containing a high proportion of monosaccharide sugars and significant amounts of polar, nitrogen-rich amino acids. These plants also converge on a common "target" flower pattern in ultraviolet and human-visible light.