SFS Annual Meeting

6/06/2024  |   13:30 - 13:45   |  Independence Ballroom B

PREDATOR EFFECTS ON PREY COMMUNITIES DIFFER BASED ON PREDATION STRATEGY AND SPATIAL SCALE The biodiversity of a region (gamma diversity) depends on how many species occur in an average habitat patch within the region (alpha diversity) and how much variation there is in the identities of species present in patches within the region (beta diversity). Models suggest that both generalist and specialist predators should reduce alpha diversity, but generalist predators would enhance beta diversity while specialist predators would reduce beta diversity. Such differences are expected as generalist predators enhance vulnerabilities to extinction in all species by reducing their population numbers while specialist predators enhance vulnerabilities of their preferred prey. We conducted an experiment in artificial ponds to assess the effects of one specialist predator (sunfish) and two generalist predators (newts and Anax dragonfly nymphs) on the alpha, beta and gamma diversity of aquatic insects present in ponds. We found 70 taxa in the artificial ponds across all treatments. Sunfish presence reduced alpha diversity by an average of 5.9 taxa and reduced gamma diversity by an average of 10.6 taxa compared to ponds that contained no predators, but there was not an effect on beta diversity. The presence of either newts or Anax did not affect diversity compared to predator free ponds. These results indicate that the effect of predators on prey diversity varies with scale and type of predator present but the particular patterns of change that we observed are not always consistent with that predicted by theory.

Jasper Leavitt (Primary Presenter/Author), East Carolina University, jasper.leavitt@gmail.com;

David Chalcraft (Co-Presenter/Co-Author), East Carolina University, chalcraftd@ecu.edu;

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6/06/2024  |   13:45 - 14:00   |  Independence Ballroom B

Effect of Leaf Litter Diversity on Adult Insect Colonization of Ponds Leaf litter provides energy and nutrients to forested aquatic ecosystems. The species of leaves affects decomposition rates, water chemistry, and the resources available to aquatic consumers. Adult insects will select pond habitats based on the leaf species in those ponds, but it is unknown whether they use leaf diversity for selection as well. We considered leaf diversity broadly and examined leaf species richness, functional diversity, and phylogenetic diversity to determine which most influenced insect habitat selection. We established 45 aquatic mesocosms as potential colonization sites in Northern Louisiana. Mixtures of leaves were randomly selected containing 0, 3, 5, 7, 9, or 11 species of leaves. Leaf functional and phylogenetic diversity were estimated for each pool and designs were discarded if these variables were related to each other or leaf species richness. Insect colonizers were collected from pools from late-April to mid-June. Preliminary data over a 1.5-week period captured ~900 individual insects from 40 species. Most individuals were from one species of dytiscid beetle, Copelatus glyphicus. More individuals and more species colonized pools with leaves than those without. We found no effect of leaf phylogenetic or functional diversity on insect species richness, total abundance, or the abundance of the two most common species. Copelatus glyphicus had lower abundance in intermediate leaf richness treatments. Future analyses will determine whether these patterns are consistent across the whole experiment and examine effects of water and leaf chemistry variables on colonizer communities.

Julia Earl (Primary Presenter/Author), Louisiana Tech University, jearl@latech.edu;

Shelby Medlock (Co-Presenter/Co-Author), Louisiana Tech University, sam135@email.latech.edu;

Daniel Edwards (Co-Presenter/Co-Author), Iowa State University, dje@iastate.edu;

Joseph Aubert (Co-Presenter/Co-Author), Louisiana Tech University, aubertjoseph@gmail.com;

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6/06/2024  |   14:00 - 14:15   |  Independence Ballroom B

EXAMINING BIODIVERSITY THROUGH THE LENS OF LACUSTRINE FISH SPECIES IN ONTARIO AND EUROPE Freshwater fishes are an invaluable part of the economy, culture, and ecosystems in temperate and tropical regions. As a result, it is imperative that we understand patterns of ecological diversity, especially in our current era of anthropogenic stressors and climate change. To create a clear picture of diversity within a given system, it is important to explore biodiversity through multiple lenses. Specifically, we look at species richness, interspecific diversity, and functional diversity to test whether there are consistent patterns across lakes in Ontario and Europe. We have examined fishes across 9350 lakes in Ontario and 1824 lakes across Europe and found that patterns in species richness relative to lake environmental conditions are similar between continents. Analyses reveal that lake area, maximum depth, watershed elevation, lake elevation, lake age, longitude, and temperature are important predictors of species richness across both continents. In all models, a random effect of watershed basin explained significant variation in fish species richness. We evaluate the hypothesis that lake environmental conditions lead to a convergence in morphological diversity between continents as well. Understanding the drivers of diversity and the scale at which they act may help us understand how to conserve these ecosystems for fish as well as other organisms within freshwater lakes.

Bailey Hewitt (Primary Presenter/Author), University of Toronto, bailey.hewitt@mail.utoronto.ca;

Donald Jackson (Co-Presenter/Co-Author), University of Toronto, don.jackson@utoronto.ca;

Brian Shuter (Co-Presenter/Co-Author), University of Toronto, brian.shuter@utoronto.ca;

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6/06/2024  |   14:15 - 14:30   |  Independence Ballroom B

Ecological Structure and Function at River Confluences Confluences disrupt the river continuum and often act as an abrupt change in habitat conditions. They are an obvious “mixing zone” of intersecting streams with differing hydrology, chemistry, and sediment characteristics and may be considered a unique habitat patch or transition zone within a river network. Due to such mixing processes, both biological community structure and ecological processes are likely affected. However, few studies have investigated the ecology of confluences. Through a two-part investigation of macroinvertebrate communities and leaf litter decomposition at five river confluences in the spring of 2023, we predicted that macroinvertebrate biodiversity and decomposition rates would be highest downstream of a confluence in the mainstem or in a tributary as opposed to upstream of a confluence on the mainstem. This study revealed the highest rates of leaf litter decomposition downstream of a confluence or in the tributary in four of five sites. Macroinvertebrate diversity was also highest downstream of a confluence in four sites and highest in the tributary at one site. However, it was determined that stream position did not statistically influence insect diversity. The unique hydrology and geomorphology of confluences likely highlight the importance of further ecological studies to gain further insight into the functionality of river systems.

Amy Pfarr (Primary Presenter/Author), University of Maryland Baltimore County (UMBC), apfarr1@umbc.edu;

Christopher Swan (Co-Presenter/Co-Author), University of Maryland Baltimore County, cmswan@umbc.edu;

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6/06/2024  |   14:30 - 14:45   |  Independence Ballroom B

The influence of oil palm cultivation on periphyton communities in northern Guatemala streams The expansion of oil palm cultivation is associated with negative environmental outcomes. However, research on its impacts on freshwater systems remains limited, and little is known about its effects on in-stream communities of primary producers. To assess these impacts, we compared periphyton communities in streams associated with forest, pasture, oil palm cultivation without riparian buffers, and oil palm cultivation with riparian buffers. Generally, the environment surrounding forest and riparian-buffered oil palm streams exhibited higher canopy cover, lower water temperature, and light input, and substrates rich in sand and leaf litter. In contrast, pasture and non-buffered oil palm streams had a lower canopy cover, more light, higher water temperatures, and substrates rich in mud and submerged vegetation. Chemical characteristics also varied among streams, with differences observed in dissolved oxygen, turbidity, and conductivity among the four types. Forest streams had the lowest chlorophyll concentration and periphyton taxon richness, with communities dominated by taxa such as Phormidium, Stigonema, Eunotia, and Frustulia. In contrast, pasture streams exhibited the highest chlorophyll concentrations and taxon richness, dominated by taxa such as Cymbella, Gonatozygon, Closterium, Cosmarium, and Spirogyra. Streams within oil palm plantations showed intermediate rates of chlorophyll concentration and richness, with genera such as Navicula and Gyrosigma representing the taxa in these streams. This research documents that oil palm cultivation significantly impacts the periphyton community structure of streams in Guatemala.

Natalia Vargas López (Primary Presenter/Author), Odum School of Ecology, University of Georgia and Center of Studies of Atitlán, navargalo@gmail.com;

Krista Capps (Co-Presenter/Co-Author), University of Georgia, kcapps@uga.edu;

Oscar A. Rojas-Castillo (Co-Presenter/Co-Author), Freshwater Biology Section, Department of Biology, University of Copenhagen, oscar.rojas.gua27@gmail.com;

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6/06/2024  |   14:45 - 15:00   |  Independence Ballroom B

Isotopic Perspectives on Common and Rare Lake Fishes: Trophic Position, Niche Overlap, and Niche Size Commonness of particular species is a key feature of regional species assemblages. Across assemblages, mesopredators are ubiquitous and are often both species-rich and locally abundant. Mesopredator fishes are prominent in most aquatic ecosystems, and these species are often assumed to have similar roles within communities. Yet, more detailed work within individual ecosystems often suggests that these species play a variety of food web roles. We used community data across 1400 lakes in combination with stable isotope analysis (d13C and d15N) in select lakes to characterize the trophic complexity of fish assemblages across the Adirondack Mountains of New York. In this region, fish assemblages are highly nested, and are dominated by small- to medium-sized mesopredators. We find that these mesopredator species have unique isotopic niches that are conserved across lakes, suggesting distinctive trophic strategies rather than substitutability of species. Overlap between isotopic niches decreased with increasing co-occurrence between species pairs, suggesting the importance of resource partitioning to reduce competition. In addition, more widespread species tend to have larger niche areas as compared to taxa with restricted distributions. Clarifying the functional differences among these species will allow for improved forecasting of changes to lake food webs as sensitive species disappear from communities due to climate change and species invasions.

Montana Airey (Primary Presenter/Author), Cornell University, ma2276@cornell.edu;

Peter McIntyre (Co-Presenter/Co-Author), Cornell University, pbm3@cornell.edu;

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