Browsing by Author "Gorczynski, Daniel"

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    Evolutionary history and environmental variability structure contemporary tropical vertebrate communities
    (Wiley, 2024) Hsieh, Chia; Gorczynski, Daniel; Bitariho, Robert; Espinosa, Santiago; Johnson, Steig; Lima, Marcela Guimarães Moreira; Rovero, Francesco; Salvador, Julia; Santos, Fernanda; Sheil, Douglas; Beaudrot, Lydia; Program in Ecology and Evolutionary Biology
    Aim Tropical regions harbour over half of the world's mammals and birds, but how their communities have assembled over evolutionary timescales remains unclear. To compare eco-evolutionary assembly processes between tropical mammals and birds, we tested how hypotheses concerning niche conservatism, environmental stability, environmental heterogeneity and time-for-speciation relate to tropical vertebrate community phylogenetic and functional structure. Location Tropical rainforests worldwide. Time period Present. Major taxa studied Ground-dwelling and ground-visiting mammals and birds. Methods We used in situ observations of species identified from systematic camera trap sampling as realized communities from 15 protected tropical rainforests in four tropical regions worldwide. We quantified standardized phylogenetic and functional structure for each community and estimated the multi-trait phylogenetic signal (PS) in ecological strategies for the four regional species pools of mammals and birds. Using linear regression models, we test three non-mutually exclusive hypotheses by comparing the relative importance of colonization time, palaeo-environmental changes in temperature and land cover since 3.3 Mya, contemporary seasonality in temperature and productivity and environmental heterogeneity for predicting community phylogenetic and functional structure. Results Phylogenetic and functional structure showed non-significant yet varying tendencies towards clustering or dispersion in all communities. Mammals had stronger multi-trait PS in ecological strategies than birds (mean PS: mammal = 0.62, bird = 0.43). Distinct dominant processes were identified for mammal and bird communities. For mammals, colonization time and elevation range significantly predicted phylogenetic clustering and functional dispersion tendencies respectively. For birds, elevation range and contemporary temperature seasonality significantly predicted phylogenetic and functional clustering tendencies, respectively, while habitat diversity significantly predicted functional dispersion tendencies. Main conclusions Our results reveal different eco-evolutionary assembly processes structuring contemporary tropical mammal and bird communities over evolutionary timescales that have shaped tropical diversity. Our study identified marked differences among taxonomic groups in the relative importance of historical colonization and sensitivity to environmental change.
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    Functional diversity and redundancy of tropical forest mammals over time
    (Wiley, 2021) Gorczynski, Daniel; Beaudrot, Lydia; Program in Ecology and Evolutionary Biology
    Globally, tropical rain forests comprise some of the most diverse and functionally rich ecosystems but are increasingly degraded by human impacts. Protected areas have been shown to conserve species diversity, but their effectiveness at maintaining functional diversity over time is less well known, despite the fact that functional diversity likely reveals more ecological information than taxonomic diversity. By extension, the degree to which species loss decreases functional diversity within protected areas is also unknown; functional redundancy may buffer communities from loss of functional diversity from some local extinctions. Using eight years of camera trap data, we quantified annual functional dispersion of the large mammal community in the Volcán Barva region of Costa Rica and tested for changes in functional dispersion over time in response to environmental and anthropogenic predictors. We quantified functional redundancy based on simulated declines in functional dispersion with species loss. Observed functional dispersion did not change significantly over time and was not associated with measured environmental or anthropogenic predictors. Quantitative modeling of observed functional traits over time did not identify significant changes. We did however find qualitative trends in relative trait proportions, which could be indicative of functional change in the future. We found high functional redundancy, with average simulated functional dispersion declining significantly only after 9 out of 21 large mammal species were lost from the community. We cautiously suggest that protected tropical rain forests can conserve functional diversity over the course of a decade even in heavily fragmented landscapes.
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    Geographic differences in body size distributions underlie food web connectance of tropical forest mammals
    (Springer Nature, 2024) Beaudrot, Lydia; Acevedo, Miguel A.; Gorczynski, Daniel; Harris, Nyeema C.; Program in Ecology and Evolutionary Biology
    Understanding variation in food web structure over large spatial scales is an emerging research agenda in food web ecology. The density of predator–prey links in a food web (i.e., connectance) is a key measure of network complexity that describes the mean proportional dietary breadth of species within a food web. Connectance is a critical component of food web robustness to species loss: food webs with lower connectance have been shown to be more susceptible to secondary extinctions. Identifying geographic variation in food web connectance and its drivers may provide insight into community robustness to species loss. We investigated the food web connectance of ground-dwelling tropical forest mammal communities in multiple biogeographic regions to test for differences among regions in food web connectance and to test three potential drivers: primary productivity, contemporary anthropogenic pressure, and variation in mammal body mass distributions reflective of historical extinctions. Mammal communities from fifteen protected forests throughout the Neo-, Afro-, and Asian tropics were identified from systematic camera trap arrays. Predator–prey interaction data were collected from published literature, and we calculated connectance for each community as the number of observed predator–prey links relative to the number of possible predator–prey links. We used generalized linear models to test for differences among regions and to identify the site level characteristics that best predicted connectance. We found that mammal food web connectance varied significantly among continents and that body size range was the only significant predictor. More possible predator–prey links were observed in communities with smaller ranges in body size and therefore sites with smaller body size ranges had higher mean proportional dietary breadth. Specifically, mammal communities in the Neotropics and in Madagascar had significantly higher connectance than mammal communities in Africa. This geographic variation in contemporary mammalian food web structure may be the product of historical extinctions in the Late Quaternary, which led to greater losses of large-bodied species in the Neotropics and Madagascar thus contributing to higher average proportional dietary breadth among the remaining smaller bodied species in these regions.
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    Measuring understorey vegetation structure using a novel mixed-reality device
    (Wiley, 2022) Gorczynski, Daniel; Beaudrot, Lydia; Program in Ecology and Evolutionary Biology
    Most ecological studies of vegetation structure have relied on manual field measurements that are labour-intensive and time-consuming. Many current alternatives to classical measurements are expensive or difficult to transport to field settings. Here we evaluated a new method for measuring understorey vegetation with a novel mixed-reality, remote sensing device, the Microsoft HoloLens. We developed a vegetation sensing application called VegSense that allows the HoloLens user to control the device's environmental scanners to measure understorey vegetation. Using VegSense, we tested the ability of the Microsoft HoloLens relative to classical field measurements to (a) detect trees and saplings, (b) measure diameter at breast height (DBH), (c) detect individual understorey vegetation structures and (d) estimate understorey vegetation complexity replicating the rod-transect method. We found that VegSense performed well in detecting and measuring trees with a DBH of 17 cm or more and estimating vegetation complexity and performed moderately at detecting understorey vegetation. Our results indicate that the HoloLens is a suitable alternative for multiple classical field measurements of understorey vegetation. This method costs much less than typical terrestrial LiDAR systems, and can facilitate efficient, high-quality environmental data collection. Further software development has the potential to reveal additional ways in which this device can be harnessed for applications to ecology and evolution.
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    The Functional Side of Diversity: Effects of Environmental Conditions and Human Disturbance on Tropical Forest Mammal Communities
    (2023-07-13) Gorczynski, Daniel; Beaudrot, Lydia
    Biodiversity provides many benefits to humans, but human activity is rapidly driving the loss of biodiversity, particularly in the tropics. Relevant species characteristics such as body size and diet, known as traits, provide insight into the biological roles of diverse species in an ecosystem. Little is known about the trait diversity of large mammals in tropical rainforests because of the reclusive nature of these species but increasing our knowledge can provide important information about critical ecosystem functions performed by mammals. In addition, many tropical mammals are currently endangered, threatening the persistence of their ecological functions. To address this pressing issue in this dissertation, I investigate how environmental and anthropogenic conditions affect mammal trait diversity in tropical rainforests around the world. This work overcomes prior data limitations by using data from the largest tropical forest remote camera monitoring network in the world. I assess the ecological drivers of trait diversity at an unprecedented scope and scale by coupling these data with cutting-edge remote sensing techniques. First, I found that mammal trait diversity remained constant over the course of a decade within a Costa Rican national park surrounded by a human dominated landscape, potentially due to high functional redundancy among this mammal community. Second, in a global comparison of 15 tropical forest national parks, I found that trait diversity was higher in parks where the amount of healthy plant growth was higher, while human-induced extinctions reduced trait diversity and therefore degraded ecosystem functions. Third, I investigated how microhabitat characteristics affected species trait diversity in a national park in Tanzania and revealed that higher forest floor habitat surface area was associated with increased mammal trait diversity, and that carnivorous and social species showed preference for higher habitat surface area. Finally, in a global analysis of species spatial overlap, I identified that species with similar traits were more likely to co-occur in the presence of high human density, suggesting that human presence is altering the spatial distribution of ecosystem functions in protected areas, potentially leading to changes in species interactions and increased extinction risk. Together, this dissertation reveals the importance of functional traits for understanding environmental and anthropogenic effects on biodiversity and identify factors that structure the critical ecological roles of mammals in tropical rain forests.