Diapause Dynamics And Host Plant Utilization of \u3ci\u3eColias Philodice, Colias Interior\u3c/i\u3e and Their Hybrids (Lepidoptera: Pieridae)

Abnormal diapause dynamics and, to a lesser extent, reduced efficiency of host utilization by hybrid larvae constitute potential post-zygotic barriers to gene flow between a multivoltine legume-feeder, Colias philodice (Lepidoptera: Pieridae) and a univoltine Vaccinium-feeder, C. interior. At the time when C. interior larvae enter diapause, approximately 50% of hybrid larvae ceased feeding but did not enter diapause, and subsequently starved. Hybrid larvae readily accepted the host plants of both parental species. However, relative to C. philodice, hybrid larvae displayed a significantly reduced fifth instar relative growth rate (RGR) when fed the primary legume host, Medicago sativa. Reduced growth of hybrid larvae was attributable to both reduced relative consumption rate (RCR) and reduced efficiency of conversion of digested food (ECD), but not to reduced digestive efficiency (AD). Relative to C. interior, hybrid larvae fed Vaccinium myrtilloides displayed reduced pupal weight and reduced ECD. These results may explain in part why all known naturally­ occurring hybrids among North American Colias arise from parental species with similar host plant ranges and diapause strategies

Facultative monophagy as a consequence of prior feeding experience: behavioral and physiological specialization in Colias philodice larvae

Although newly-emerged Colias philodice readily accept Medicago sativa, Melilotus alba , and Coronilla varia , fifth instar larvae reared on any single plant species display a highly significant induced feeding preference for their rearing host. Forced host-switching reveals that fifth instar relative growth rate (RGR) on M. sativa and M. alba is significantly reduced by prior feeding on either alternative host. Moreover, regardless of rearing diet, switching to a novel host during the fifth instar results in reduced RGR, relative consumption rate (RCR), efficiency of conversion of digested food (ECD), and pupal weight. These results support the hypothesis that induction of feeding preference is an adaptive response that predisposes larvae to feed on the plant species they are most capable of utilizing for growth.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47778/1/442_2004_Article_BF00377204.pd

Determinants of diet quality: the effects of diet pH, buffer concentration and buffering capacity on growth and food utilization by larvae of Manduca sexta (Lepidoptera: Sphingidae)

The growth of fourth-instar Manduca sexta larvae on nutrient-rich artificial diets is significantly affected by the characteristics of the buffer system present in the diet. An increase in diet buffer concentration or buffering capacity can cause decreases in total larval weight gain, relative growth rate, net growth efficiency and larval lipid content, and increases in the length of the instar, respiration rate, and the amount of assimilated food allocated to energy metabolism. We conclude that there is a significant metabolic cost associated with processing a diet with a high buffer concentration or buffering capacity. Within the pH range examined in this study (4.4-5.5), pH has a less pronounced effect on herbivore growth parameters, and presumably also on fitness, than do buffer concentration and buffering capacity. These results demonstrate that foliar buffer systems are potentially important determinants of the nutritional value of foliage to insect herbivores.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31031/1/0000708.pd

Performance of a generalist grasshopper on a C 3 and a C 4 grass: compensation for the effects of elevated CO 2 on plant nutritional quality

The increasing CO 2 concentration in Earth’s atmosphere is expected to cause a greater decline in the nutritional quality of C 3 than C 4 plants. As a compensatory response, herbivorous insects may increase their feeding disproportionately on C 3 plants. These hypotheses were tested by growing the grasses Lolium multiflorum C 3 ) and Bouteloua curtipendula C 4 ) at ambient (370 ppm) and elevated (740 ppm) CO 2 levels in open top chambers in the field, and comparing the growth and digestive efficiencies of the generalist grasshopper Melanoplus sanguinipes on each of the four plant × CO 2 treatment combinations. As expected, the nutritional quality of the C 3 grass declined to a greater extent than did that of the C 4 grass at elevated CO 2 ; protein levels declined in the C 3 grass, while levels of carbohydrates (sugar, fructan and starch) increased. However, M. sanguinipes did not significantly increase its consumption rate to compensate for the lower nutritional quality of the C 3 grass grown under elevated CO 2 . Instead, these grasshoppers appear to use post-ingestive mechanisms to maintain their growth rates on the C 3 grass under elevated CO 2 . Consumption rates of the C 3 and C 4 grasses were also similar, demonstrating a lack of compensatory feeding on the C 4 grass. We also examined the relative efficiencies of nutrient utilization from a C 3 and C 4 grass by M. sanguinipes to test the basis for the C 4 plant avoidance hypothesis. Contrary to this hypothesis, neither protein nor sugar was digested with a lower efficiency from the C 4 grass than from the C 3 grass. A novel finding of this study is that fructan, a potentially large carbohydrate source in C 3 grasses, is utilized by grasshoppers. Based on the higher nutrient levels in the C 3 grass and the better growth performance of M. sanguinipes on this grass at both CO 2 levels, we conclude that C 3 grasses are likely to remain better host plants than C 4 grasses in future CO 2 conditions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47704/1/442_2004_Article_1555.pd

Effects of elevated atmospheric CO 2 on the nutritional ecology of C 3 and C 4 grass-feeding caterpillars

It is plausible that the nutritional quality of C 3 plants will decline more under elevated atmospheric CO 2 than will the nutritional quality of C 4 plants, causing herbivorous insects to increase their feeding on C 3 plants relative to C 4 plants. We tested this hypothesis with a C 3 and C 4 grass and two caterpillar species with different diet breadths. Lolium multiflorum (C 3 ) and Bouteloua curtipendula (C 4 ) were grown in outdoor open top chambers at ambient (370 ppm) or elevated (740 ppm) CO 2 . Bioassays compared the performance and digestive efficiencies of Pseudaletia unipuncta (a grass-specialist noctuid) and Spodoptera frugiperda (a generalist noctuid). As expected, the nutritional quality of L. multiflorum changed to a greater extent than did that of B. curtipendula when grown in elevated CO 2 ; levels of protein (considered growth limiting) declined in the C 3 grass, while levels of carbohydrates (sugar, starch and fructan) increased. However, neither insect species increased its feeding rate on the C 3 grass to compensate for its lower nutritional quality when grown in an elevated CO 2 atmosphere. Consumption rates of P. unipuncta and S. frugiperda were higher on the C 3 grass than the C 4 grass, the opposite of the result expected for a compensatory response to the lower nutritional quality of the C 4 grass. Although our results do not support the hypothesis that grass-specialist insects compensate for lower nutritional quality by increasing their consumption rates more than do generalist insects, the performance of the specialist was greater than that of the generalist on each grass species and at both CO 2 levels. Mechanisms other than compensatory feeding, such as increased nutrient assimilation efficiency, appear to determine the relative performance of these herbivores. Our results also provide further evidence against the hypothesis that C 4 grasses would be avoided by insect herbivores because a large fraction of their nutrients is unavailable to herbivores. Instead, our results are consistent with the hypothesis that C 4 grasses are poorer host plants primarily because of their lower nutrient levels, higher fiber levels, and greater toughness.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47706/1/442_2004_Article_1572.pd

Differential effect of tannic acid on two tree-feeding Lepidoptera: implications for theories of plant anti-herbivore chemistry

Feeding efficiencies of ultimate instar larvae of two polyphagous tree-feeding Lepidoptera, Malacosoma disstria (Lasiocampidae) and Orgyia leucostigma (Liparidae), were measured on artificial diets containing from 0% to 8% tannic acid. Relative growth rate (RGR) of O. leucostigma was not affected by up to 8% tannic acid, suggesting that O. leucostigma has evolved an effective counteradaptation to hydrolyzable tannins. In contrast, as little as 0.5% tannic acid caused a significant reduction in RGR of M. disstria , due both to reduced efficiency of conversion of digested food (ECD) and reduced relative consumption rate (RCR), and caused a significant increase in mortality during the pupal stage. Moreover, when reared from hatching on tannin-containing diets, no M. disstria larvae survived past the fourth instar.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47780/1/442_2004_Article_BF00380074.pd

Adult oviposition preference, larval feeding preference, survivorship, and growth rates for Colias interior and Colias philodice.

The data presented here attest to the importance of both genetics and experience in determining feeding preference in C. philodice and C. interior. Larvae demonstrate an innate preference for specific host plants, but their ability to utilize host plant tissue depends on previous feeding experience. The larvae used for these experiments will be raised through pupation and will, I am hopeful, allow subsequent investigation of oviposition and feeding preference among interspecific hybrids.http://deepblue.lib.umich.edu/bitstream/2027.42/53528/1/1963.pdfDescription of 1963.pdf : Access restricted to on-site users at the U-M Biological Station

Predicting Host Range Evolution: Colonization Of Coronilla Varia By Colias Philodice (Lepidoptera: Pieridae)

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137286/1/evo03852.pd

The effects of quantity and quality of diet nitrogen on the growth, efficiency of food utilization, nitrogen budget, and metabolic rate of fifth-instar Spodoptera eridania larvae (Lepidoptera: Noctuidae)

Relative growth rate and relative nitrogen accumulation rate for fifth-instar Spodoptera eridania larvae vary less than 20% on artificial diets in which protein content varies more than 250%, due to compensatory adjustments in consumption rate and changes in efficiencies of food and nitrogen utilization. The substitution of zein for two-thirds of the casein in a diet containing 26.0% protein results in a 25% decrease in both relative growth and nitrogen accumulation rates, due to reduced values of relative consumption rate, relative nitrogen consumption rate, approximate digestibility, approximate digestibility of nitrogen and efficiency of conversion of digested nitrogen. Although larval growth rate is relatively independent of diet nitrogen, larval composition is highly dependent upon both nitrogen quantity and quality. As diet nitrogen increases, larval nitrogen content increases and fat content decreases. Larvae on diets containing a mixture of casein and zein produce 3.5-3.9 times as much uric acid and respire at rates significantly higher than larvae on diets containing the same total amount of protein but lacking zein. Thus, there is a measurable metabolic cost associated with processing low quality protein. We conclude, however, that elevated metabolic rates of larvae on diets containing nutritionally unbalanced protein are not the cause of reduced growth rates. On these diets, growth is limited byan amino acid present in limiting quantities, and the elevated metabolic rate is due, at least in part, to increased synthesis of uric acid. Finally, we discuss the possibility that variation in amino acid profiles across host plant species might be a factor favouring specialization in insect herbivores.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28225/1/0000678.pd