Effect of Carbohydrate Supplementation on Investment into Offspring Number, Size, and Condition in a Social Insect

Resource availability can determine an organism's investment strategies for growth and reproduction. When nutrients are limited, there are potential tradeoffs between investing into offspring number versus individual offspring size. In social insects, colony investment in offspring size and number may shift in response to colony needs and the availability of food resources. We experimentally manipulated the diet of a polymorphic ant species (Solenopsis invicta) to test how access to the carbohydrate and amino acid components of nectar resources affect colony investment in worker number, body size, size distributions, and individual percent fat mass. We reared field-collected colonies on one of four macronutrient treatment supplements: water, amino acids, carbohydrates, and amino acid and carbohydrates. Having access to carbohydrates nearly doubled colony biomass after 60 days. This increase in biomass resulted from an increase in worker number and mean worker size. Access to carbohydrates also altered worker body size distributions. Finally, we found a negative relationship between worker number and size, suggesting a tradeoff in colony investment strategies. This tradeoff was more pronounced for colonies without access to carbohydrate resources. The monopolization of plant-based resources has been implicated in the ecological success of ants. Our results shed light on a possible mechanism for this success, and also have implications for the success of introduced species. In addition to increases in colony size, our results suggest that having access to plant-based carbohydrates can also result in larger workers that may have better individual fighting ability, and that can withstand greater temperature fluctuations and periods of food deprivation

Meta-analysis of gender performance gaps in undergraduate natural science courses

To investigate patterns of gender-based performance gaps, we conducted a meta-analysis of published studies and unpublished data collected across 169 undergraduate biology and chemistry courses. While we did not detect an overall gender gap in performance, heterogeneity analyses suggested further analysis was warranted, so we investigated whether attributes of the learning environment impacted performance disparities on the basis of gender. Several factors moderated performance differences, including class size, assessment type, and pedagogy. Specifically, we found evidence that larger classes, reliance on exams, and undisrupted, traditional lecture were associated with lower grades for women. We discuss our results in the context of natural science courses and conclude by making recommendations for instructional practices and future research to promote gender equity

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Data from: Harvesting biofuel grasslands has mixed effects on natural enemy communities and no effects on biocontrol services

1.Perennial bioenergy systems, such as switchgrass and restored prairies, are alternatives to commonly used annual monocultures such as maize. Perennial systems require lower chemical input, provide greater ecosystem services such as carbon storage, greenhouse gas mitigation, and support greater biodiversity of beneficial insects. However, biomass harvest will be necessary in managing these perennial systems for bioenergy production, and it is unclear how repeated harvesting might affect ecosystem services. 2.In this study, we examined how repeated production-scale harvesting of diverse perennial grasslands influences vegetation structure, natural enemy communities (arthropod predators and parasitoids), and natural biocontrol services in two states (Wisconsin and Michigan, USA) over multiple years. 3.We found that repeated biomass harvest reduced litter biomass and increased bare ground cover. Some natural enemy groups, such as ground-dwelling arthropods, decreased in abundance with harvest whereas others, such as foliar-dwelling arthropods increased in abundance. The disparity in responses is likely due to how different taxonomic groups utilize vegetation and differences in dispersal abilities. 4.At the community level, biomass harvest altered community composition, increased total arthropod abundance, and decreased evenness but did not influence species richness, diversity, or biocontrol services. Harvest effects varied with time, diminishing in strength both within the season (for total abundance and evenness), across seasons (for evenness), or were consistent throughout the duration of the study (for community composition). Greater functional redundancy and compensatory responses of the different taxonomic groups may have buffered against the potentially negative effects of harvest on biocontrol services. 5.Synthesis and applications. Our results show that in the short-term, repeated harvesting of perennial grasslands (when insect activity is low) consistently altered vegetation structure but had mixed effects on natural enemy communities and no discernable effects on biocontrol services. However, the long-term effects of repeated harvesting on vegetation structure, natural enemies, and other arthropod-derived ecosystem services such as pollination and decomposition remain largely unknown

Mean (± SE) worker head width for colonies supplemented with amino acids (dashed lines) and/or carbohydrates (grey bars) to their diet.

<p>Head width was significantly larger in colonies supplemented carbohydrates than those not supplemented carbohydrates (ANOVA <i>F</i>_{<i>1</i>, <i>24</i>} = 5.82, <i>p</i> = 0.024). There was no effect of amino acid (<i>F</i>_{<i>1</i>, <i>24</i>} = 0.03, <i>p</i> = 0.86). There was no interaction between carbohydrates and amino acid supplementation on worker head width (<i>F</i>_{<i>1</i>, <i>24</i>} = 0.04, <i>p</i> = 0.84).</p

The mean (± SE) percent fat mass workers supplemented carbohydrates (gray bars) and/or amino acids (dashed lines) to their diet.

<p>There was no significant effect of carbohydrates (ANCOVA, <i>F</i>_{<i>1</i>, <i>23</i>} = 0.03, <i>p</i> = 0.86), amino acids (<i>F</i>_{<i>1</i>, <i>21</i>} = 0.01, <i>p</i> = 0.93), or their interaction (<i>F</i>_{<i>1</i>, <i>24</i>} = 0.1, <i>p</i> = 0.76) on worker fat mass.</p

ANOVA table for the effect of diet treatment on worker number and worker body size.

<p>ANOVA table for the effect of diet treatment on worker number and worker body size.</p

The proportion of workers from two subpopulations (minors = 0–0.75 mm and majors = 0.75–1.6 mm) (sensu Tschinkel 1988).

<p><b>A.</b> There proportion of workers is significantly different between diet supplements (<i>G</i>-test <i>G =</i> 39.99, <i>d</i>.<i>f</i>. = 3, <i>p</i> < 0.0001). Specifically, there is a greater proportion of minor workers with wider HW from colonies reared with access to carbohydrates (gray bars) (<i>G =</i> 34.2 <i>d</i>.<i>f</i>. = 1, <i>p</i> < 0.0001). <b>B.</b> The proportion of smallest minor workers (0–0.675 mm) is significantly different between treatments (<i>G</i> = 314, <i>d</i>.<i>f</i>. = 3, <i>p</i> < 0.0001). Colonies with access to carbohydrates had significantly more workers with larger heads (<i>G</i> = 191, <i>d</i>.<i>f</i>. = 1, <i>p</i> < 0.0001). <b>C.</b> The proportion of the smallest major workers (0.75–1.125 mm) was not significantly different between treatments (<i>G</i> = 2.24, <i>d</i>.<i>f</i>. = 3, <i>p</i> = 0.52). There is no significant difference in HW of major workers from colonies reared without access to carbohydrates and those with access to carbohydrates (<i>G</i> = 0.2, <i>d</i>.<i>f</i>. = 1, <i>p</i> = 0.66).</p

Worker body size distributions based on head width of experimental colonies of <i>Solenopsis invicta</i> after being reared for 60 days on diets that varied access to water (blue, diamonds) carbohydrates (green, triangles), amino acids (red, squares), or both (purple, asterisks).

<p>Worker body size distributions based on head width of experimental colonies of <i>Solenopsis invicta</i> after being reared for 60 days on diets that varied access to water (blue, diamonds) carbohydrates (green, triangles), amino acids (red, squares), or both (purple, asterisks).</p