Biomedical subjects

Carol L Boggs

Publications and source records attributed to Carol L Boggs.

9 recordsLinked to original sources

PubMed2006

Delayed population explosion of an introduced butterfly.

1. The causes of lagged population and geographical range expansions after species introductions are poorly understood, and there are relatively few detailed case studies. 2. We document the 29-year history of population dynamics and structure for a population of Euphydryas gillettii Barnes that was introduced to the Colorado Rocky Mountains, USA in 1977. 3. The population size remained low (< 200 individuals) and confined to a single habitat patch (approximately 2.25 ha) to 1998. These values are similar to those of many other populations within the natural geographical range of the species. 4. However, by 2002 the population increased dramatically to > 3000 individuals and covered approximately 70 ha, nearly all to the south of the original site. The direction of population expansion was the same as that of predominant winds. 5. By 2004, the butterfly's local distribution had retracted mainly to three habitat patches. It thus exhibited a 'surge/contraction' form of population growth. Searches within 15 km of the original site yielded no other new populations. 6. In 2005, butterfly numbers crashed, but all three habitat patches remained occupied. The populations within each patch did not decrease in the same proportions, suggesting independent dynamics that are characteristic of metapopulations. 7. We postulate that this behaviour results, in this species, in establishment of satellite populations and, given appropriate habitat structure, may result in lagged or punctuated expansions of introduced populations.

Animals↗

PubMed2005

Larval food limitation in butterflies: effects on adult resource allocation and fitness.

Allocation of larval food resources affects adult morphology and fitness in holometabolous insects. Here we explore the effects on adult morphology and female fitness of larval semi-starvation in the butterfly Speyeria mormonia. Using a split-brood design, food intake was reduced by approximately half during the last half of the last larval instar. Body mass and forewing length of resulting adults were smaller than those of control animals. Feeding treatment significantly altered the allometric relationship between mass and wing length for females but not males, such that body mass increased more steeply with wing length in stressed insects as compared to control insects. This may result in changes in female flight performance and cost. With regard to adult life history traits, male feeding treatment or mating number had no effect on female fecundity or survival, in agreement with expectations for this species. Potential fecundity decreased with decreasing body mass and relative fat content, but there was no independent effect of larval feeding treatment. Realized fecundity decreased with decreasing adult survival, and was not affected by body mass or larval feeding treatment. Adult survival was lower in insects subjected to larval semi-starvation, with no effect of body mass. In contrast, previous laboratory studies on adult nectar restriction showed that adult survival was not affected by such stress, whereas fecundity was reduced in direct 11 proportion to the reduction of adult food. We thus see a direct impact of larval dietary restriction on survival, whereas fecundity is affected by adult dietary restriction, a pattern reminiscent of a survival/reproduction trade-off, but across a developmental boundary. The data, in combination with previous work, thus provide a picture of the intra-specific response of a suite of traits to ecological stress.

Animal Nutritional Physiological Phenomena↗

PubMed2005

Linking nectar amino acids to fitness in female butterflies.

Nectar of butterfly-pollinated flowers contains generally higher levels of amino acids than does nectar of flowers pollinated by most other animal types. One proposed explanation is that these amino acids promote butterfly fitness, although the evidence has been equivocal. In a new study, Mevi-Schütz and Erhardt showed that nectar amino acids enhanced fecundity in the butterfly Araschnia levana, but only when the larval diet was poor. Their results support the hypothesis that butterflies are agents of selection for higher nectar amino acid production, suggest that the larval food plant has a key role in the evolution of the flower-butterfly mutualism, and demonstrate that the importance, to butterfly reproduction, of different nutrient sources varies with butterfly nutritional state.

Journal Article↗

PubMed2005

The amino acids used in reproduction by butterflies: a comparative study of dietary sources using compound-specific stable isotope analysis.

It is a nutritional challenge for nectar-feeding insects to meet the amino acid requirements of oviposition. Here we investigate whether egg amino acids derive from larval diet or are synthesized from nectar sugar in four species of butterfly: Colias eurytheme, Speyeria mormonia, Euphydryas chalcedona, and Heliconius charitonia. These species exhibit a range of life history and differ in degree of shared phylogeny. We use 13C differences among plants to identify dietary sources of amino acid carbon, and we measure amino acid 13C using compound-specific stable isotope analysis. Egg essential amino acids derived solely from the larval diet, with no evidence for metabolic carbon remodeling. Carbon in nonessential amino acids from eggs derived primarily from nectar sugars, with consistent variation in amino acid turnover. There was no relationship between the nonessential amino acids of eggs and host plants, demonstrating extensive metabolic remodeling. Differences between species in carbon turnover were reflected at the molecular level, particularly by glutamate and aspartate. Essential amino acid 13C varied in a highly consistent pattern among larval host plants, reflecting a common isotopic "fingerprint" associated with plant biosynthesis. These data demonstrate conservative patterns of amino acid metabolism among Lepidoptera and the power of molecular stable isotope analyses for evaluating nutrient metabolism in situ.

Amino Acids↗

PubMed2003

Pollen feeding in the butterfly Heliconius charitonia: isotopic evidence for essential amino acid transfer from pollen to eggs.

Heliconius and Laparus butterflies exhibit a unique pollen-collecting behaviour that enhances lifespan and fecundity. The specific nutritional contribution of pollen, however, had not been previously demonstrated. We used stable isotope variation to trace the carbon flow into eggs from corn pollen provided experimentally to ovipositing female Heliconius charitonia, and to evaluate the use of isotopically contrasting nectar sugars in egg amino acids. The delta(13)C of individual amino acids from pollen, larval host plant and the eggs from experimental butterflies was measured with gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS), to evaluate amino acid transfer. The delta(13)C of egg essential amino acids indicated a transfer of essential amino acids from pollen to butterfly eggs. However, the delta(13)C of non-essential amino acids reflected the isotopic composition of the artificial nectar, indicating that H. charitonia synthesizes non-essential amino acids from dietary sugars. This, to our knowledge, is the first direct demonstration of amino acid transfer from pollen to butterfly eggs, and suggests that essential amino acids in particular are a key resource for extending lifespan and fecundity in Heliconius butterflies.

Amino Acids, Essential↗

PubMed2003

The evolution of wing color: male mate choice opposes adaptive wing color divergence in Colias butterflies.

Correlated evolution of mate signals and mate preference may be constrained if selection pressures acting on mate preference differ from those acting on mate signals. In particular, opposing selection pressures may act on mate preference and signals when traits have sexual as well as nonsexual functions. In the butterfly Colias philodice eriphyle, divergent selection on wing color across an elevational gradient in response to the thermal environment has led to increasing wing melanization at higher elevations. Wing color is also a long-range signal used by males in mate searching. We conducted experiments to test whether sexual selection on wing melanization via male mate choice acts in the same direction as natural selection on mate signals due to the thermal environment. We performed controlled mate choice experiments in the field over an elevational range of 1500 meters using decoy butterflies with different melanization levels. Also, we obtained a more direct estimate of the relation between wing color and sexual selection by measuring mating success in wild-caught females. Both our experiments showed that wing melanization is an important determinant of female mating success in C. p. eriphyle. However, a lack of elevational variation in male mate preference prevents coevolution of mate signals and mate preference, as males at all elevations prefer less-melanized females. We suggest that this apparently maladaptive mate choice may be maintained by differences in detectability between the morphs or by preservation of species recognition.

Animals↗

PubMed2002

Climate change hastens population extinctions.

Climate change is expected to alter the distribution and abundance of many species. Predictions of climate-induced population extinctions are supported by geographic range shifts that correspond to climatic warming, but few extinctions have been linked mechanistically to climate change. Here we show that extinctions of two populations of a checkerspot butterfly were hastened by increasing variability in precipitation, a phenomenon predicted by global climate models. We model checkerspot populations to show that changes in precipitation amplified population fluctuations, leading to rapid extinctions. As populations of checkerspots and other species become further isolated by habitat loss, climate change is likely to cause more extinctions, threatening both species diversity and critical ecosystem services.

Animals↗

PubMed2002

Renewable and nonrenewable resources: amino acid turnover and allocation to reproduction in Lepidoptera.

The allocation of nutritional resources to reproduction in animals is a complex process of great evolutionary significance. We use compound-specific stable isotope analysis of carbon (GC/combustion/isotope ratio MS) to investigate the dietary sources of egg amino acids in a nectar-feeding hawkmoth. Previous work suggests that the nutrients used in egg manufacture fall into two classes: those that are increasingly synthesized from adult dietary sugar over a female's lifetime (renewable resources), and those that remain exclusively larval in origin (nonrenewable resources). We predict that nonessential and essential amino acids correspond to these nutrient classes and test this prediction by analyzing egg amino acids from females fed isotopically distinct diets as larvae and as adults. The results demonstrate that essential egg amino acids originate entirely from the larval diet. In contrast, nonessential egg amino acids were increasingly synthesized from adult dietary sugars, following a turnover pattern across a female's lifetime. This study demonstrates that female Lepidoptera can synthesize a large fraction of egg amino acids from nectar sugars, using endogenous sources of nitrogen. However, essential amino acids derive only from the larval diet, placing an upper limit on the use of adult dietary resources to enhance reproductive success.

Amino Acids↗

PubMed2002

The evolution of wing color in Colias butterflies: heritability, sex linkage, and population divergence.

We investigated the genetic background of intraspecific variation in wing color across an elevational gradient in the butterfly Colias philodice eriphyle. The degree of wing melanization was an accelerating function of elevation, and differences in wing melanization persisted in a common environment. Full-sibling analysis and parent-offspring regression yielded consistent, moderate to high heritabilities for the degree of wing melanization. The breeding experiments also demonstrated that wing melanization is strongly sex linked. Because traits that differentiate sister species also tend to be sex linked, our results suggest that the genetic mechanisms underlying intraspecific differences in wing melanization are not fundamentally different from those that have been shown to differentiate sister species.

Analysis of Variance↗