Organismic and Evolutionary Biology Graduate Student Publication Series

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Now showing 1 - 3 of 3
  • Publication
    Remember your roots: Biogeographic properties of plants' native habitats can inform invasive plant risk assessments
    (2023-01-01) Pfadenhauer, William; Nelson, Michael; Laginhas, Britt; Bradley, Bethany
    Aim: Reducing the effects of invasive plants is best accomplished by predicting which species will invade and preventing their introduction. To do this, risk assessments rely on a variety of plant traits and biogeographic properties to predict potential invasiveness. However, the relative importance of these traits and properties is unknown. Determining which biogeographic properties contribute the most to predicting invasiveness could improve the accuracy and reduce the time needed to complete future risk assessments. Here, we provide a comprehensive analysis and ranking of the biogeographic properties that best differentiate invasive and noninvasive plant species. Location: Conterminous United States. Methods: We compiled county-level distributions of 10,721 vascular plant species native to the conterminous United States of which 884 were established elsewhere and 131 were invasive elsewhere. For each species, we used native distribution data to calculate biogeographic properties, including range size, human modification and abiotic niche breadth. We assessed the ability of biogeographic properties to predict whether each species was invasive outside of the United States using random forest classification models. Results: Variables that represent the breadth of a species' native range, including the ranges of soil textures, ranges of soil fertility and total geographic area, are strong predictors of plant invasiveness. Models that included these variables correctly classified 86% of invasive species and 62% of noninvasive species. Variables representing resource availability and disturbance regime were not useful for distinguishing between established and invasive species. Main conclusions: Focusing on niche breadth properties could improve the accuracy of risk assessments and reduce the effort spent compiling information with lower predictive power. The importance of niche breadth in this analysis supports previous findings that broad physiological tolerance enables survival and reproduction in numerous environments, thereby increasing the likelihood of invasion.
  • Publication
    Effects of the floral phytochemical eugenol on parasite evolution and bumble bee infection and preference
    (2018-01-01) Palmer-Young, Evan C.; Calhoun, Austin C.; Mirzayeva, Anastasiya; Sadd, Benn M.
    Ecological and evolutionary pressures on hosts and parasites jointly determine infection success. In pollinators, parasite exposure to floral phytochemicals may influence between-host transmission and within-host replication. In the bumble bee parasite Crithidia bombi, strains vary in phytochemical resistance, and resistance increases under in vitro selection, implying that resistance/infectivity trade-offs could maintain intraspecific variation in resistance. We assessed costs and benefits of in vitro selection for resistance to the floral phytochemical eugenol on C. bombi infection in Bombus impatiens fed eugenol-rich and eugenol-free diets. We also assessed infection-induced changes in host preferences for eugenol. In vitro, eugenol-exposed cells initially increased in size, but normalized during adaptation. Selection for eugenol resistance resulted in considerable (55%) but non-significant reductions in infection intensity; bee colony and body size were the strongest predictors of infection. Dietary eugenol did not alter infection, and infected bees preferred eugenol-free over eugenol-containing solutions. Although direct effects of eugenol exposure could influence between-host transmission at flowers, dietary eugenol did not ameliorate infection in bees. Limited within-host benefits of resistance, and possible trade-offs between resistance and infectivity, may relax selection for eugenol resistance and promote inter-strain variation in resistance. However, infection-induced dietary shifts could influence pollinator-mediated selection on floral traits.
  • Publication
    Identification of supraoptimal temperatures in juvenile blueback herring (Alosa aestivalis) using survival, growth rate and scaled energy reserves
    (2022-01-01) Guo, Lian W; Jordaan, Adrian; Schultz, Eric T.; McCormick, Stephen D.
    For young fishes, growth of somatic tissues and energy reserves are critical steps for survival and progressing to subsequent life stages. When thermal regimes become supraoptimal, routine metabolic rates increase and leave less energy for young fish to maintain fitness-based activities and, in the case of anadromous fishes, less energy to prepare for emigration to coastal habitats. Thus, understanding how energy allocation strategies are affected by thermal regimes in young anadromous fish will help to inform climate-ready management of vulnerable species and their habitat. Blueback herring (Alosa aestivalis) are an anadromous fish species that remain at historically low population levels and are undergoing southern edge-range contraction, possibly due to climate change. We examined the effects of temperature (21°C, 24°C, 27°C, 30°C, 33°C) on survival, growth rate and energy reserves of juveniles collected from the mid-geographic range of the species. We identified a strong negative relationship between temperature and growth rate, resulting in smaller juveniles at high temperatures. We observed reduced survival at both 21°C and 33°C, increased fat and lean mass-at-length at high temperatures, but no difference in energy density. Juveniles were both smaller and contained greater scaled energy reserves at higher temperatures, indicating growth in length is more sensitive to temperature than growth of energy reserves. Currently, mid-geographic range juvenile blueback herring populations may be well suited for local thermal regimes, but continued warming could decrease survival and growth rates. Blueback herring populations may benefit from mitigation actions that maximize juvenile energy resources by increasing the availability of cold refugia and food-rich habitats, as well as reducing other stressors such as hypoxic zones.