Browsing by Subject "trade-offs"

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    Choosiness as a component of life history strategies in cabbage white butterflies
    (2017-07) Jaumann, Sarah
    Many animals are choosy when selecting resources such as mates, food, or sites to lay eggs. For animals that lay eggs and do not subsequently care for their young, choosing the best sites for their eggs can greatly increase the survival and health of their offspring. Given these benefits, it is surprising that there is variation in choosiness; not all animals are choosy when laying eggs. Behaviors can be costly if they require energy and exhibit trade-offs with other traits that also require energy. I applied this idea to choosiness during oviposition, testing the hypothesis that animals are not choosy when being choosy is costly. In cabbage white butterflies, I demonstrated variation in choosiness and a trade-off between choosiness and fecundity, suggesting that being choosy is costly. If energetic costs determine degree of choosiness, then manipulating energy from food should lead to variation in choosiness. I manipulated food availability directly by varying nutrition and indirectly by varying butterfly density and thus potential competition for food. Density did not affect choosiness or other traits, but nutrition did. Poor adult nutrition led to lower levels of choosiness and lower fecundity but no changes in other traits. Thus, poor nutrition may decrease investment in multiple traits, including choosiness, rather than causing adaptive shifts in life history with increased investment in some traits. My results suggest that choosiness is energetically costly, but only direct cues about energy availability affect choosiness. These findings have implications for the health of butterflies and other pollinators.
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    Evaluating weed management decisions that influence cover crop adoption in the Upper Midwest
    (2022-12) Ley, Ethan
    The use of pre-emergence residual herbicides has proven to be an effective strategy for controlling problematic late-emerging weed species in annual crops. However, the use of residual preemergence (PRE) herbicides has the potential to negatively affect other crops within an annual two-crop rotation, such as fall-planted cover crops. The intent of this study was to determine if residual PRE herbicides would affect the emergence and growth of fall-planted cover crops. Four PRE herbicides, dimethenamid-p, a packaged mixture of dimethenamid-p + saflufenacil, a packaged mixture of acetochlor + clopyralid + mesotrione, and a layered treatment of dimethenamid-p 30 days after first application of dimethenamid-p were applied before silage corn planting. Following silage corn harvest in the fall, three cover crops, winter cereal rye (S. cereale ), winter camelina (C. sativa ), and red clover (T. pratense) were planted with a no-till drill at three locations in Minnesota that differed in soil type and climate. Plant measurements were obtained for each cover crop at burndown in the spring to assess establishment, growth and biomass. Cover crop height, plant density, and ground coverage in the spring were influenced by an interactions between cover crop species, herbicide, and location . However, there was no difference in the total biomass accumulation at termination the following Spring. These results indicate that application of these residual PRE herbicides for control of late-emerging weed species did not interfere with cover crop biomass production as long as soil moisture was at or above normal during the growing season.