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

Pre-Employment Screening Considerations and the ADA

This brochure is one of a series on human resources practices and workplace accommodations for persons with disabilities edited by Susanne M. Bruyère, Ph.D., CRC, Director, Employment and Disability Institute, Cornell University ILR School. The original version was written in 1993 by Marjorie E. Karowe, Attorney, Schenectady, N.Y., and updated in 2000 by Sheila D. Duston, an attorney/mediator practicing in the Washington, D.C. metropolitan area. It was further updated in 2011 by Beth Reiter, an independent legal consultant, Ithaca, N.Y., with assistance from Sara Furguson, a Cornell University Employment and Disability Institute student research assistant

Consideraciones respecto a las evaluaciones previas al empleo y la ADA

Este folleto es parte de una serie de prácticas de recursos humanos y acomodaciones en el lugar de trabajo para personas con discapacidades, editado por Susanne M. Bruyère, PhD., CRC, SPHR, directora del Programa sobre Empleo y Discapacidad, Escuela de Relaciones Laborales e Industriales, División de Extensión de la Universidad de Cornell. La versión original fue redactada en 1993 por Marjorie E. Karowe, abogada en Schenectady, Nueva York, y actualizada en el año 2000 por Sheila D. Duston, abogada conciliadora que ejerce en la zona metropolitana de Washington, D.C. Fue actualizada una vez más en el año 2011 por Beth Reiter, consultora legal independiente en Ithaca, Nueva York, con la asistencia de Sara Furguson, estudiante y asistente de investigación del Employment and Disability Institute de la Universidad de Cornell

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

The importance of testing multiple environmental factors in legume–insect research: replication, reviewers, and rebuttal

Investigating the impacts of predicted changes in our atmosphere and climate change on insect–plant interactions is a widely pursued area of research. To date, the majority of experimental studies have tested the impacts of single environmental factors on insect–plant interactions, but meta-analyses have clearly illustrated the importance of investigating multiple factors in tandem (Zvereva and Kozlov, 2006; Robinson et al., 2012). In particular, environmental change factors often interact with each other which can either strengthen or mitigate the effects of environmental factors acting alone (Robinson et al., 2012). For example, the positive effects of elevated atmospheric carbon dioxide concentrations (e [CO2]) on plant growth are stronger under high nitrogen (N) conditions compared to low N conditions (+ 32 and+ 19%, respectively; Robinson et al., 2012). Likewise, from the limited number of studies available, Robinson et al.(2012) showed that e [CO2] had different impacts on plant nitrogen, plant biomass, and secondary metabolites under elevated air temperature (eT) conditions. This does not invalidate single factor studies, of which we have published numerous examples, but this is an important consideration for making realistic predictions about how plants and insects will respond to future climates (Facey et al., 2014)

Physiological factors affecting the rapid decrease in protein assimilation efficiency by a caterpillar on newly‐mature tree leaves

Lymantria dispar L. caterpillars have a decreased ability to assimilate protein from mature leaves of red oak ( Quercus rubra ) compared with young, expanding leaves. The present study determines whether the drop in protein assimilation efficiency (PAE) occurs during the rapid phase of leaf maturation. Several mechanisms that might account for decreased PAE are also examined: mature leaf tissues could resist being chewed efficiently, protein in mature leaf tissues could become difficult to extract, and other nutrients in mature leaves might become growth limiting. The entire seasonal decrease in PAE occurs rapidly (in less than 2 weeks), when the leaves finished expanding. The maturation process is characterized by increased levels of fibre and decreased levels of water but no significant changes in the levels of protein or carbohydrates. Despite increased fibre in mature leaves, they are not chewed into larger food particles than are immature leaves. Carbohydrate assimilation efficiencies remain high on mature leaves, and signs of limiting water levels in larvae of L. dispar on mature leaves are not observed. The most important finding in the present study is the decreased extractability of protein in food particles from mature leaves, which plays a major role in explaining the rapid decrease in PAE. It is hypothesized that structural changes in cell walls during the rapid process of leaf maturation decrease protein extractability, which, in turn, greatly decreases the nutritional quality of mature oak leaves for caterpillars. The results of the present study therefore suggest a general mechanism to help explain the widely documented decrease in the nutritional quality of the mature leaves of many tree species for herbivorous insects.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106099/1/phen12049.pd

Response of Wheat Fungal Diseases to Elevated Atmospheric CO2 Level

Infection with fungal pathogens on wheat varieties with different levels of resistance was tested at ambient (NC, 390 ppm) and elevated (EC, 750 ppm) atmospheric CO2 levels in the phytotron. EC was found to affect many aspects of the plant-pathogen interaction. Infection with most fungal diseases was usually found to be promoted by elevated CO2 level in susceptible varieties. Powdery mildew, leaf rust and stem rust produced more severe symptoms on plants of susceptible varieties, while resistant varieties were not infected even at EC. The penetration of Fusarium head blight (FHB) into the spike was delayed by EC in Mv Mambo, while it was unaffected in Mv Regiment and stimulated in Mv Emma. EC increased the propagation of FHB in Mv Mambo and Mv Emma. Enhanced resistance to the spread of Fusarium within the plant was only found in Mv Regiment, which has good resistance to penetration but poor resistance to the spread of FHB at NC. FHB infection was more severe at EC in two varieties, while the plants of Mv Regiment, which has the best field resistance at NC, did not exhibit a higher infection level at EC. The above results suggest that breeding for new resistant varieties will remain a useful means of preventing more severe infection in a future with higher atmospheric CO2 levels