ALBERT

Notes: Abstract Knowledge of both prokaryotic and eukaryotic organisms is essential to the study of molecular evolution. Their common ancestry mandates that their molecular functions share many aspects of adaptation and constraint, yet their differences in size, ploidy, and structural complexity also give rise to divergent evolutionary options. We explore the interplay of adaptation, constraint, and neutrality in their evolution by the use of genetic variants to probe molecular function in context of molecular structure, metabolic organization, and phenotype-environment interactions. Case studies ranging from bacteria to butterflies, flies, and vertebrates emphasize, among other points: a. the importance of moving from initial recording of evolutionary pattern variation to studying the processes underlying the patterns, by experiment, reconstructive inference, or both; b. the complementarity, not conflict, of finding different performance and fitness impacts of natural variants in prokaryotes or eukaryotes, depending on the nature and magnitude of the variants, their locations and roles in pathways, the nature of molecular function affected, and the resulting organismal phenotype-environment interactions leading to selection or its absence; c. the importance of adaptive functional interaction of different kinds of variants, as in gene expression variants versus variants altering polypeptide properties, or interaction of changes in enzymes' active sites with complementary changes elsewhere that adjust catalytic function in different ways, or coadaptation of different steps' properties in pathways; d. the power afforded by combining structural and functional analyses of variants with study of the variants' phenotype-environment interactions to understand how molecular changes affect (or fail to affect) adaptive mechanisms "in the wild." Comparative study of prokaryotes and eukaryotes in this multifaceted way promises to deliver both new insights into evolution and a host of new and productive questions about it.

Notes: [Auszug] Colios eurytheme Boisduval (Lepidoptera: Pieridae) is a convenient subject for investigation of the biological significance of pierid pteridines. Pteridines are deposited in the scales of the wings and, in company with melanin, they produce the orange and black wing pattern characteristic of this ...

Notes: [Auszug] Table l. CHEMICAL PROPERTIES OP PTERIDINES Electrophoretic Compound RF value* migration: cm toward anodef Extinction absorption coefficient $ peak(m/")i 2-amino-4-hydroxy- 0-18 23 262 1646010 6-carboxyl-pteridine Xanthopterin 0-36 22 392 6500 ...

Notes: Summary 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. Densities of adults fluctuate drastically, with the first (overwintering) brood always being less dense than the second brood. Dispersal radius of those dispersing does not vary with brood, sex, or year, although the proportion of dispersants does: more males than females disperse in the first brood, while the reverse is true in the second. A tentative behavioral explanation for this is proposed. Adult mortality is unusually high compared to other Colias. The population displays area continuity with adjacent population areas. The Wrightian neighborhood size varies in geographic extent, due to change in dispersant proportions, from 70 to 260 hectares. In adult numbers, it varies from 4–500 (or possibly fewer in very severe first-brood conditions) to upwards of 20,000 in some second broods (though not all adults present always reproduce successfully). Two possible models for the dispersal behavior of Colias are presented. One, the “excited state” model, is so far supported over the other, “continuous activity” model, by the present data and by earlier work on C. alexandra. The adult mortality level is consistent with the conclusion that this population is ecologically marginal for the species. Possible selective pressures preventing further extension of the species' distribution, including possible competition with other Colias, are discussed.

Notes: Summary 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. A system for measuring degree of physical damage to the adults is introduced. This “wear rating” varies with temporal position of any given sample in the course of a brood's flight season, the insects becoming progressively more damaged with time. The sex ratio also changes with brood aging: males eclose before females, and are in the majority early in the flight season, while females may predominate at the end of flight. Local population numbers for the montane grassland species C. alexandra may reach peak levels of 700–900 insects in favorable years, but be much lower in other years as a result of, e.g., drought. Peak densities are no more than 2/ha. The montane bog species, C. scudderi, maintains comparable low density but has much smaller local populations. The subalpine/alpine grassland species C. meadii displays peak local numbers as high as 3000, with peak density as high as 120/hectare. Dispersal varies both among and within species. Those C. alexandra who disperse show an average dispersal radius of about 1.3 km, with a radius for the whole population of about 0.6 km; maximum distance moved was 8 km. Dispersal proportions among recaptures are sharply curtailed by adverse weather, but the dispersal radius of those moving is unaffected by weather. C. scudderi's dispersal is strongly influenced by the geometry of its bog and streamside habitats. Some C. meadii populations approach isolated “island” status, but others show much dispersal. Dispersal radius of those dispersing ranges from 0.3 to 0.7 km in different populations, but the proportion of dispersals varies greatly. The longest observed movement by this species is 1.3 km, although up to 2.6 km could have been detected. Colias normally display constant loss (death plus emigration) rates with average residence expectations of 4–6 days; few insects reach their maximum physiological lifespan of approximately 1 month. Bad weather can increase the loss rate drastically. Females show shorter residence than males, appearently as a result of greater mortality. Total-numbers-per-brood estimates are given for our better studied populations. The reproductive strategy of Colias is such that Wright's models for neighborhood size apply. Neighborhood size for C. alexandra varied sixfold in numbers, and from 3 to 1.3 km in physical extent, between a favorable year and a drought year. One localized C. scudderi habitat is only 200 m in diameter, but a streamside population has a neighborhood length of 4.8 km. In C. meadii, one population of 2000–2500 insects is an 8-ha “island”, while another of similar numbers extends a single neighborhood across 1.9 km distance, 450 m altitude, and a major ecological boundary (timberline). Factors such as weather, individuals' visual cueing, and thermoregulatory behavior can influence population structure. For some Colias populations, selection may be very uniform within neighborhoods, while for others, single neighborhoods cross sharp discontinuities in selective forces. These patterns may differ for different selective forces, and may also vary with stages of the insects' life cycle. these populations will now prove a valuable resource for studying evolutionary population genetics.

Notes: Summary 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.

Notes: Summary 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. High-energy demand, endothermic pollinators, by contrast, appear to require higher concentration nectars and/or higher proportions of di- and oligosaccharide sugars. These results are discussed in the light of water balance and energy budget demands of different pollinator classes. Questions are also raised concerning behavioral aspects of pollinator search for resources and the pertinence of these data to the concept of floral mimicry.

Notes: Summary 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. Larval and adult experience had little or no effect on females' preference. These results suggest that the intra-population variation in oviposition preference is genetically based, but the results of experiments designed to estimate the heritability of oviposition preference were not conclusive. We suggest that intra-population variation in host selection characters may play a key role in shifts to new host plants.

Notes: Summary 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. Total heat loss is best expressed as the sum of heat loss from the head and thorex combined plus heat loss from the abdomen because the whole body is not isothermal. Convective cooling is a simple linear function of the square root of air speed from 0.2 to 2.0 m/s in the wind tunnel. Solar heat flux is the main source of heat gain in flight, just as it is the exclusive source for warmup at rest. The balance of heat gain from sunlight versus heat loss from convection and radiation does not appear to change by more than a few percent between the wings-closed basking posture and the variable opening of wings in flight, although several aspects require further study. Heat generation by action of the flight muscles is small (on the order of 100 m W/g tissue) compared to values reported for other strongly flying insects. Colias appears to have only very limited capacity to modulate flight performance. Wing beat frequency varies from 12–19 Hz depending on body mass, air speed, and thoracic temperature. At suboptimal flight temperatures, wing beat frequency increases significantly with thoracic temperature and body mass but is independent of air speed. Within the reported thermal optimum of 35–39°C, wing beat frequency is negatively dependent on air speed at values above 1.5 m/s, but independent of mass and body temperature. Flight preference of butterflies in the wind tunnel is for air speeds of 0.5–1.5 m/s, and no flight occurs at or above 2.5 m/s. Voluntary flight initiation in the wild occurs only at air speeds ≦1.4 m/s. In the field, Colias fly just above the vegetation at body temperatures of 1–2°C greater than when basking at the top of the vegetation. These measurements are consistent with our findings on low heat gain from muscular activity during flight. Basking temperatures of butterflies sheltered from the wind within the vegetation were 1–2°C greater than flight temperatures at vegetation height.

Notes: Summary The thermal ecology ofColias butterfly larvae has been studied, using simple modifications of previous thermistor implantation technology. Like their adults, these larvae rely on a repertoire of thermoregulatory behavior to control body temperature in relation to external heat sources and sinks. They neither heat nor cool by metabolic means. They display narrow, well-marked body temperature ranges for their major activity, feeding. These are 10–15 °C lower than the maximum activity temperatures of the adults. Also in contrast to the adults, the locations of the larval activity maxima differ by several degrees C between the taxa studied. In each taxon studied the rate of feeding reaches a maximum in a body temperature range corresponding roughly to the temperature range maximizing the occurrence of feeding. The overall larval growth rate is maximized under constant temperature regimes corresponding to the maximum feeding range. A qualitative model for larval activity in the field in relation to daily temperature changes is constructed and apparently supported in its essentials. These results are discussed in relation to other aspects of larval ecology, notably predator pressure, and some speculation on their meaning for larval metabolic organization is raised.