Explorations Into Who is Doing Freshwater Science and How We are Altering Waterscapes

The United States of America and the world are faced with three massive intertwining challenges at this time: COVID-19, racial inequity, and climate change. As a species, humans must come together and collectively address these challenges to preserve our humanity and make our world a more just and livable place for all species. This dissertation presents research to support paths forward on addressing racial inequity in scientific societies and human alterations to freshwater ecosystems, two small components of the larger challenges we face. We must not get overwhelmed by the magnitude of the issues that face us; instead, we must deconstruct them into actionable parts that we as individuals and communities can address, issue by issue. While academic researchers are encouraged by institutions (whether explicitly or implicitly) to be narrowly focused on their scientific research, many researchers are challenging this constraining stance and are demanding the freedom to study the contextual web surrounding their research. Scientists are stepping back and examining who is and who is not entering and remaining in their fields. Scientists are more and more often taking the time to place their work in the context of the world within which we live and consider the impacts of racial inequities and climate change both on their science, their fellow collaborators, and the public. My doctoral research and this dissertation reflect my efforts to model this approach to academic research as a graduate employee and scholar deeply concerned about our humanity. First, I address racial inequity in scientific societies and provide a path for one scientific society of which I am a member to become more inclusive and diverse. Specifically, I, along with 10 co-authors, evaluated the demography within the Society for Freshwater Science (SFS; Chapter 2). Respondents overwhelmingly identified as white (87%). Women, respondents with disabilities, and individuals from marginalized racial backgrounds were underrepresented in SFS relative to the US population. Only 0.7% of SFS survey respondents identified as Black, although African Americans represented 6% of the US professoriate in 2015. People who identified as transgender and people who identified as LGBTQ+ constituted a higher percentage of survey respondents than those identifying as such among US adults. We acknowledge that concerted efforts are needed to recognize and challenge systemic discrimination to ensure scientists from marginalized groups can contribute to and benefit from scientific societies. To aid in these efforts, we presented a guide for SFS toward creating a more welcoming and equitable space for all scientists to do their research. In addition to examining who is doing freshwater science, I, along with eight co-authors, examined how humans are altering freshwater ecosystems. Specifically, I quantified how dams in the Colorado River Basin are impacting aquatic invertebrate communities at the community (Chapter 3) and molecular (Chapter 4) levels. I found that each tailwater (i.e., the section of river downstream of a dam) was dominated by 3-7 invertebrate taxa that comprised 95% of individuals. Many of these dominant taxa were non-insect, non-flying species and thus were unavailable to terrestrial consumers. Consistent with previous studies, aquatic insects and sensitive EPT taxa (Ephemeroptera, Plecoptera, and Trichoptera) were negatively associated with hydropeaking intensity (magnitude of daily flow fluctuations associated with hydropower generation), which puts limits on the type and perhaps quality of the invertebrate food base. While total invertebrate abundance and biomass did not change with increasing distance from dam, insect and EPT richness, abundance, and biomass all increased, suggesting that impacts of damming are most acute immediately downstream of dams. Our results demonstrate that western U.S. tailwaters can support aquatic invertebrate communities with high abundance, yet low species diversity. At the molecular level, I used 2bRAD genetics methods to determine genetic diversity, population structure, and evidence of fragmentation for three species of aquatic insects in the Grand Canyon that differed according to dispersal ability. Genetic results revealed that actual dispersal patterns may not always be accurately predicted by trait databases and distribution patterns for some widespread species. We found evidence that both R. distincta and H. osleri are relatively high dispersers, whereas F. quilleri is a moderate disperser. This finding is congruent with dispersal abilities predicted by trait database for H. osleri and F. quilleri, but contradicts information for R. distincta. Additionally, genetic diversity and relationships between genetic and geographic distance suggest the evolutionary mechanisms at play in a fragmented landscape for these species. F. quilleri exhibited isolation by distance, whereas H. osleri and R. distincta showed evidence of gene flow. Furthermore, H. osleri showed population structure between tributaries on the North Rim vs. South Rim. As genetic tools become cheaper and more powerful, researchers will be able to understand the movements of and more successfully conserve understudied organisms, such as aquatic insects, that are critical for the integrity of our ecosystems. Ultimately my main dissertation chapters will be published as three scientific journal articles and contribute to the base of literature that organizers, activists, and conversation practitioners use to conserve our natural resources and make our scientific societies more just and equitable. Simply put, I have just provided the data. It is up to me and my readers to use these data to make substantial changes in how our human communities operate and how we as humans impact our environment. As a PhD student, I have begun this work, choosing to work with the Society for Freshwater Science to improve its meetings, working with the labor union of Oregon State graduate employees to create more equitable conditions for workers, and collaborating with the US Geological Survey which works closely with power companies operating dams. As a post-doc and later as a professional, I am committed to continuing this work in whatever context that I can. I believe that it is imperative that academic scientists take up the challenge of both analyzing the societal context surrounding their scientific research and making their labs, departments, universities, and communities more diverse and inclusive spaces. This is work that all humans must do, but academics are uniquely poised to do this work as people who are paid to think and do research. We must do some of the heavy lifting, as there are many, many folx who do not have the academic freedom that we are privileged enough to have. We must use that privilege to create a more just, equitable, sustainable, and loving society. Why else are we here

Network Structure of Vertebrate Scavenger Assemblages at the Global Scale: Drivers and Ecosystem Functioning Implications

The organization of ecological assemblages has important implications for ecosystem functioning, but little is known about how scavenger communities organize at the global scale. Here, we test four hypotheses on the factors affecting the network structure of terrestrial vertebrate scavenger assemblages and its implications on ecosystem functioning. We expect scavenger assemblages to be more nested (i.e. structured): 1) in species‐rich and productive regions, as nestedness has been linked to high competition for carrion resources, and 2) regions with low human impact, because the most efficient carrion consumers that promote nestedness are large vertebrate scavengers, which are especially sensitive to human persecution. 3) We also expect climatic conditions to affect assemblage structure, because some scavenger assemblages have been shown to be more nested in colder months. Finally, 4) we expect more organized assemblages to be more efficient in the consumption of the resource. We first analyzed the relationship between the nestedness of the scavenger assemblages and climatic variables (i.e. temperature, precipitation, temperature variability and precipitation variability), ecosystem productivity and biomass (i.e. NDVI) and degree of human impact (i.e. human footprint) using 53 study sites in 22 countries across five continents. Then, we related structure (i.e. nestedness) with its function (i.e. carrion consumption rate). We found a more nested structure for scavenger assemblages in regions with higher NDVI values and lower human footprint. Moreover, more organized assemblages were more efficient in the consumption of carrion. However, our results did not support the prediction that the structure of the scavenger assemblages is directly related to climate. Our findings suggest that the nested structure of vertebrate scavenger assemblages affects its functionality and is driven by anthropogenic disturbance and ecosystem productivity worldwide. Disarray of scavenger assemblage structure by anthropogenic disturbance may lead to decreases in functionality of the terrestrial ecosystems via loss of key species and trophic facilitation processes

Averting biodiversity collapse in tropical forest protected areas

The rapid disruption of tropical forests probably imperils global biodiversity more than any other contemporary phenomenon¹⁻³. With deforestation advancing quickly, protected areas are increasingly becoming final refuges for threatened species and natural ecosystem processes. However, many protected areas in the tropics are themselves vulnerable to human encroachment and other environmental stresses⁴⁻⁹. As pressures mount, it is vital to know whether existing reserves can sustain their biodiversity. A critical constraint in addressing this question has been that data describing a broad array of biodiversity groups have been unavailable for a sufficiently large and representative sample of reserves. Here we present a uniquely comprehensive data set on changes over the past 20 to 30 years in 31 functional groups of species and 21 potential drivers of environmental change, for 60 protected areas stratified across the world’s major tropical regions. Our analysis reveals great variation in reserve ‘health’: about half of all reserves have been effective or performed passably, but the rest are experiencing an erosion of biodiversity that is often alarmingly widespread taxonomically and functionally. Habitat disruption, hunting and forest-product exploitation were the strongest predictors of declining reserve health. Crucially, environmental changes immediately outside reserves seemed nearly as important as those inside in determining their ecological fate, with changes inside reserves strongly mirroring those occurring around them. These findings suggest that tropical protected areas are often intimately linked ecologically to their surrounding habitats, and that a failure to stem broad-scale loss and degradation of such habitats could sharply increase the likelihood of serious biodiversity declines.Keywords: Ecology, Environmental scienc

Impacts of Invasive Species on Ecosystem Energy Flow on the Big Island of Hawai\u27i: Excuse Me, But Are You Going to Eat That Cane Toad?

Worldwide, it has been estimated that invasive species have negative economic impacts in the billions of dollars, with impacts to island ecosystems being among the most devastating. While it is estimated that the most costly and destabilizing impacts are upon ecosystem functions, such impacts are difficult to quantify monetarily, and exact mechanisms are poorly understood. In particular, the role invasive species play in altering energy flow through ecosystems, specifically regarding the recycling of nutrients associated with carrion, is poorly elucidated for most invasive vertebrates. How invasive amphibians and reptiles, which comprise the majority of the invasive species biomass in island ecosystems, may be affecting energy flow within the scavenging pathway is virtually unknown. By setting out camera traps associated with carcasses of 3 taxa (coqui frogs, geckos, cane toads), this study has identified the dominant scavenging vertebrates on the Big Island of Hawai\u27i, as well as the fate of sequestered energy that is available to be scavenged upon the death of invasive amphibians and reptiles. These data contribute to our understanding of the functional mechanisms through which invasive species alter energy flow and stability of insular ecosystems

Diverse, equitable, and inclusive scientific societies: Progress and opportunities in the Society for Freshwater Science

Discussions about diversity, equity, and inclusivity are becoming increasingly common in scientific societies. However, more concerted efforts are needed to recognize and challenge systemic discrimination to ensure scientists from marginalized groups can contribute to and benefit from scientific societies. Here, we evaluate efforts and opportunities within the Society for Freshwater Science (SFS) as examples for how scientific societies can make progress toward diversity, equity, and inclusivity. In 2017, SFS collected anonymous demographic information and open-ended feedback from SFS members through an online survey. We combined this information with 2 examples of recent initiatives and challenges that occurred within SFS. We present a guide for SFS and other scientific societies toward creating a more welcoming and equitable space for all scientists. To prioritize diversity, equity, and inclusivity, scientific societies must center the voices of marginalized and underrepresented people in all scientific society activities, including within groups of all sizes and at all society events. These actions will allow scientific societies to better represent and engage with their current and future members and the broader communities those members serve

Scavenging in the Anthropocene: Human impact drives vertebrate scavenger species richness at a global scale

Understanding the distribution of biodiversity across the Earth is one of the most challenging questions in biology. Much research has been directed at explaining the species latitudinal pattern showing that communities are richer in tropical areas; however, despite decades of research, a general consensus has not yet emerged. In addition, global biodiversity patterns are being rapidly altered by human activities. Here, we aim to describe large‐scale patterns of species richness and diversity in terrestrial vertebrate scavenger (carrion‐consuming) assemblages, which provide key ecosystem functions and services. We used a worldwide dataset comprising 43 sites, where vertebrate scavenger assemblages were identified using 2,485 carcasses monitored between 1991 and 2018. First, we evaluated how scavenger richness (number of species) and diversity (Shannon diversity index) varied among seasons (cold vs. warm, wet vs. dry). Then, we studied the potential effects of human impact and a set of macroecological variables related to climatic conditions on the scavenger assemblages. Vertebrate scavenger richness ranged from species‐poor to species rich assemblages (4–30 species). Both scavenger richness and diversity also showed some seasonal variation. However, in general, climatic variables did not drive latitudinal patterns, as scavenger richness and diversity were not affected by temperature or rainfall. Rainfall seasonality slightly increased the number of species in the community, but its effect was weak. Instead, the human impact index included in our study was the main predictor of scavenger richness. Scavenger assemblages in highly human‐impacted areas sustained the smallest number of scavenger species, suggesting human activity may be overriding other macroecological processes in shaping scavenger communities. Our results highlight the effect of human impact at a global scale. As speciesrich assemblages tend to be more functional, we warn about possible reductions in ecosystem functions and the services provided by scavengers in human‐dominated landscapes in the Anthropocene

Functional traits driving species role in the structure of terrestrial vertebrate scavenger networks

Species assemblages often have a non-random nested organization, which in vertebrate scavenger (carrion-consuming) assemblages is thought to be driven by facilitation in competitive environments. However, not all scavenger species play the same role in maintaining assemblage structure, as some species are obligate scavengers (i.e., vultures) and others are facultative, scavenging opportunistically. We used a database with 177 vertebrate scavenger species from 53 assemblages in 22 countries across five continents to identify which functional traits of scavenger species are key to maintaining the scavenging network structure. We used network analyses to relate ten traits hypothesized to affect assemblage structure with the ‘role’ of each species in the scavenging assemblage in which it appeared. We characterized the role of a species in terms of both the proportion of monitored carcasses on which that species scavenged, or scavenging breadth (i.e., the species ‘normalized degree’), and the role of that species in the nested structure of the assemblage (i.e., the species ‘paired nested degree’), thus identifying possible facilitative interactions among species. We found that species with high olfactory acuity, social foragers, and obligate scavengers had the widest scavenging breadth. We also found that social foragers had a large paired nested degree in scavenger assemblages, probably because their presence is easier to detect by other species to signal carcass occurrence. Our study highlights differences in the functional roles of scavenger species and can be used to identify key species for targeted conservation to maintain the ecological function of scavenger assemblages

Scavenging in the Anthropocene: Human impact drives vertebrate scavenger species richness at a global scale

Understanding the distribution of biodiversity across the Earth is one of the most challenging questions in biology. Much research has been directed at explaining the species latitudinal pattern showing that communities are richer in tropical areas; however, despite decades of research, a general consensus has not yet emerged. In addition, global biodiversity patterns are being rapidly altered by human activities. Here, we aim to describe large-scale patterns of species richness and diversity in terrestrial vertebrate scavenger (carrion-consuming) assemblages, which provide key ecosystem functions and services. We used a worldwide dataset comprising 43 sites, where vertebrate scavenger assemblages were identified using 2,485 carcasses monitored between 1991 and 2018. First, we evaluated how scavenger richness (number of species) and diversity (Shannon diversity index) varied among seasons (cold vs. warm, wet vs. dry). Then, we studied the potential effects of human impact and a set of macroecological variables related to climatic conditions on the scavenger assemblages. Vertebrate scavenger richness ranged from species-poor to species rich assemblages (4–30 species). Both scavenger richness and diversity also showed some seasonal variation. However, in general, climatic variables did not drive latitudinal patterns, as scavenger richness and diversity were not affected by temperature or rainfall. Rainfall seasonality slightly increased the number of species in the community, but its effect was weak. Instead, the human impact index included in our study was the main predictor of scavenger richness. Scavenger assemblages in highly human-impacted areas sustained the smallest number of scavenger species, suggesting human activity may be overriding other macroecological processes in shaping scavenger communities. Our results highlight the effect of human impact at a global scale. As species-rich assemblages tend to be more functional, we warn about possible reductions in ecosystem functions and the services provided by scavengers in human-dominated landscapes in the Anthropocene.SG, JMPG, and ACA were supported by Juan de la Cierva contracts (Ministerio de Economía y Competitividad, MEC; IJCI‐2015‐24947, FJCI‐2015‐25632, and IJCI‐2014‐20744, respectively). ESG was also supported by Generalitat Valenciana (SEJI/2018/024), ACA by the Govern de les Illes Balears (PD/039/2017), and MM by a Ramón y Cajal contract (MEC; RYC‐2015‐19231). EA was supported by La Caixa‐Severo Ochoa International PhD Program 2015. NS was partly supported by the National Science Centre in Poland (2013/08/M/NZ9/00469). SAL thanks PICT (BID) 0725/2014. MK and KJ were supported by the Slovenian Research Agency (P4‐0059). Contributions of KT and JCB were partially supported through funding from U.S. Department of Agriculture, the U.S. Department of Energy under (DE‐EM0004391) to the University of Georgia Research Foundation. EB and EF were supported by the USA National Science Foundation. CK completed study under research permit NCST/5/002/R/448 with support from Hawk Mountain Sanctuary, The Peregrine Fund, and via Pompeo M. Maresi Memorial Fund via Princeton University. JAS and CCW were supported by the USA National Science Foundation #1255913 and the Gordon and Betty Moore Foundation. Several authors were funded by funds from the MEC (CGL2012‐40013‐C02‐01/02, CGL2015‐66966‐C2‐1‐R and CGL2017‐89905‐R) and from the Junta de Andalucía (RNM‐1925).Peer reviewe