Biology

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    Unraveling a potential cryptic species complex of Polydora colonia and Polydora spongicola through morphology and DNA barcoding
    (Wheaton College. (Norton, Mass.), 2023-05) McGrail, Ophelia
    Marine biological invasions are a critical problem concerning biodiversity and habitat structure in the ocean. Rates of introductions are exacerbated by human activities in our interconnected world such as international shipping, travel, and commercial fishing. Introductions are difficult to track and manage, and this problem is made even more difficult by the existence of cryptic species complexes. These complexes are defined as two or more genetically different species "hiding" under a single species due to morphological or phylogenetic similarities. These complexes can be elucidated using genetic tools such as DNA barcoding. Cryptic invasions may occur if one species in the complex is native to an area, and another species is introduced and becomes established without detection. One group of organisms at the intersection of concerns on invasive species and cryptic species complex is the Polychaeta. The Polychaeta, a group of marine annelid worms, contains cryptic species complexes, some of which are  known to cause ecological and economic damage when introduced. This thesis investigates the possibility that two sponge-boring polychaete species, Polydora colonia and Polydora spongicola, may be part of a cryptic species complex. This question is addressed using DNA barcoding and morphological examination. This thesis is the first genetic study of Polydora colonia. 
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    Local and Landscape Level Effects on the Abundance, Morphometrics, and Diet Diversity of Invasive mantids Tenedora Sinensis and Mantis religiosa.
    (Wheaton College. (Norton, Mass), 2022-05-16) Shmerling, Adi.
    Arthropod Generalist Predators (AGP) play a substantial role in the ecosystem, feeding on a variety of prey items across trophic levels with little to no selective bias. As a result, AGP can be especially problematic if introduced to new environments, disrupting food webs and causing reductions in native populations, which can lead to top-down ecological cascades. In this study, we researched two AGP which are invasive to the Northeastern United States, the European mantis (M. religiosa) and the Chinese mantis (T. sinensis), both of which inhabit early-succession meadows and fields. These environments are noteworthy in that they are fragmentary by nature, and as such, inhabitant species diversity is heavily constrained by patch size, connectivity, and plant diversity. In order to assess how these constraints influenced the abundance, growth, and diet of M. religiosa and T. sinensis, we combined remote sensing, plant diversity surveys, and in- and ex- situ abundance, morphometric, and DNA metabarcoded gut content data to find correlations between these landscape, terrain and individual level variables.
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    Soil fungal responses to multiple global change stressors.
    (Wheaton College. (Norton, Mass.), 2022-05-16) Embury, Emily Lynn
    Human activities have driven environmental changes such as soil warming, nitrogen enrichment, and non-native plant invasions, and all three of these global change drivers have been shown to alter soil fungal communities. Soil fungi play important roles in decomposition, carbon sequestration, and nutrient cycling processes so it is important to understand how fungal communities are impacted by different global change drivers. To further understand the impacts of soil warming, nitrogen enrichment, and non-native plant invasions on soil fungi, I sought to analyze seven previously published studies together to look for generalizable patterns in how fungal communities respond to these global change drivers. I analyzed sequence data from seven studies and measured species richness, community composition, effect sizes of indicator species, and the distribution of trophic modes across treatments. I found significant variation of species richness in one study, significant variation of community composition in two studies, five key indicator species (none were common across all treatments), and no significant variation in trophic mode distribution. These results suggest that fungal responses to disturbance are highly dependent on the type of disturbance and site conditions. 
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    Patterns of succession in Wheaton woods
    (Wheaton College (MA), 1978) Chapman, Ellen
    A study of the floristic composition of Wheaton Woods, Norton Massachusetts is described with particular emphasis on its relation to successional processes and patterns. General history of New England forests is considered, and community characteristics of the study site described. Tree species were censused in respect to density, basal area, age, coverage and DFD indices so that general successional status could be ascertained. Reproductive success, percent mortality, and species diversity measures are used to suggest future floristic composition and general successional patterns. While white pine and red oak are presently characteristic across much of the study site, Wheaton Woods shows a high degree of heterogeneity due to natural as well as anthropeic disturbances. It is suggested that red and white oak along with red maple may become the most important species, while white pine will continue to decline in abundance and importance. Evaluation of succession and climax theory suggests that evolutionary adaptations of each species to specific stresses encompasses and supersedes traditional successional concepts. Stability of ecosystems is evaluated in relation to species diversity and stand age, and the importance of perturbation in maintenance of stability is emphasized.
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    Functional morphology of the Ocean Sunfish (Mola mola) Pharyngeal Jaw
    (Wheaton College. (Norton, Mass.), 2021-05-16) Flaum, Benjamin
    This study looked at the functional morphology of the ocean sunfish (Mola mola) pharyngeal jaw by looking at the general morphology, behavior under force, and the gelatinous prey retention of the pharyngeal jaws and teeth. This study demonstrates a novel use of pharyngeal teeth in fish, similar to structures found throughout the vertebrates that prevent the loss of ingested food and newly acquired prey items. We also discovered a functionally unique muscle to control the eversion of these teeth and other morphological characteristics (high safety factor, tooth replacement) that highlight the critical role of these teeth to the mola. Lastly, this study demonstrated that these teeth are likely only useful in adult fish, which follows the known ontogenetic diet shift.