SFS Annual Meeting

6/04/2024  |   13:30 - 13:45   |  Independence Ballroom B

Unlocking the Past: Multigenic Analysis Sheds Light on Polypedilum Evolution and Biogeography in South America Polypedilum is one of the largest genera in Chironomidae, with approximately 440 described species and a global distribution. Polypedilum larvae are found in various aquatic environments, primarily in sediments, but also associated with macrophytes and Phytotelmata. Although phylogenetic analyses of the genus have been conducted in recent decades, no study has addressed biological processes such as diversification, dispersal, and vicariance in a biogeographic context. The main objective of this study was to propose a hypothesis on the divergence time of Polypedilum lineages with emphasis on species from South America, through phylogenetic reconstructions. To achieve this aim, we analyzed concatenated multigenic data comprising 3166 characters from 143 individual specimens using both maximum likelihood and Bayesian inference frameworks. The monophyly of the genus Polypedilum was confirmed, as well as the monophyly of the subgenera Asheum and Cerobregma. The initial divergence of Polypedilum was estimated to be approximately 75 MYA, at the end of the Cretaceous period, followed by substantial diversification during the Paleogene, a pattern shared by other genera of Chironomidae. Analyses suggest that the ancestors of Polypedilum originated in the Northern Hemisphere, especially in Oriental Region, with multiple dispersal events to southern regions. Additionally, some nodes are biogeographically informative, indicating geographic structuring among species collected in different regions of Argentina and Chile. This study provides valuable insights into the evolutionary history and biogeography of Polypedilum species in South America. The next step will involve the implementation of diversification analyses to further elucidate the latitudinal gradient of diversity in this ecologically significant group of aquatic insects.

Fabio Laurindo da Silva (Primary Presenter/Author), University of São Paulo, fabiologia@gmail.com;

Elisabeth Stur (Co-Presenter/Co-Author), Norwegian University of Science and Technology, elisabeth.stur@ntnu.no;

Chao Song (Co-Presenter/Co-Author), Taizhou University, songchaonk@163.com ;

Silvio Shigueo Nihei (Co-Presenter/Co-Author), University of São Paulo, silvionihei@gmail.com ;

Torbjørn Ekrem (Co-Presenter/Co-Author), Norwegian University of Science and Technology , torbjorn.ekrem@ntnu.no;

Luiz Carlos (Co-Presenter/Co-Author), Federal University of Florianopolis, luizcarlospinho@gmail.com ;

Nicholas Matzke (Co-Presenter/Co-Author), Auckland University, n.matzke@auckland.ac.nz ;

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6/04/2024  |   13:45 - 14:00   |  Independence Ballroom B

DIVERSITY OF CHIRONOMIDAE FROM COASTAL WETLANDS ALONG WASHINGTON’S PACIFIC COAST Coastal dune wetlands are vulnerable to loss of habitat from development as well as destruction from sea level rise and severe storms resulting from climate change. The purpose of this research is to document chironomid communities from coastal wetlands along Washington’s Pacific Coast. Chironomidae are common wetland insects, and some species tolerate large ranges in environmental conditions making them ideal in biodiversity studies of coastal wetlands. This study was conducted on Point Brown Peninsula, Grays Harbor County, Washington, which supports a diversity of coastal wetlands ranging from bogs to an engineered lake and canal network to ephemeral pools. Additionally, the high dune ecosystems of Point Brown Peninsula are characterized by Sitka spruce and coastal forests which create stable lentic habitats. Despite their proximity to the ocean, most coastal wetlands in the study region receive more surface runoff and precipitation than saltwater intrusion making them freshwater ecosystems. Samples of Surface Floating Pupal Exuviae were collected seasonally for two years from 11 sites on Point Brown Peninsula. Over 3000 specimens have been enumerated and identified to the lowest taxonomic level. A total of 30 morphospecies were documented with the highest diversity found in unaltered wetlands in the study region. Damaging winter storms during king tides threaten the jetty protecting the interior of the peninsula and if saltwater enters these wetlands, then the chironomid community will likely be impacted. Thus, this research provides a baseline by which to monitor any such impacts in the future.

Barbara Hayford (Primary Presenter/Author), University of Montana, barbara.hayford@umt.edu;

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6/04/2024  |   14:00 - 14:15   |  Independence Ballroom B

THE SIGNIFICANCE OF TAXA RESOLUTION OF CHIRONOMIDAE IN URBAN SEMI-ARID STORMWATER PONDS Freshwater is an important natural resource that needs to be protected, especially as urban pressures that affect its health increase. This study was conducted in a semi arid urban city in North Texas and examined the aquatic macroinvertebrate community in permanent stormwater ponds. The study compared ponds along a gradient of urbanization to understand what variables are important in maximizing biodiversity in these highly fragmented and impacted systems. Using a modified 1 meter box sampler, benthic macroinvertebrates were collected from available vegetated habitats in May using a dip net. These invertebrates were identified to lowest possible taxa and the communities were compared to habitat variables and water quality parameters. We determined that as urbanization increased taxa richness decreased and that taxa richness was greater in habitats of emergent and submerged vegetation cover compared to Typha spp. The most abundant organism in the ponds was Chironomidae with 33 genera represented. The most important finding from this study was the added knowledge from identifying Chironomidae to the genus level. The higher taxa resolution strengthened the understanding of the biodiversity within stormwater ponds and better management practices for this area. Many studies only view Chironomidae at the tribe or family level and often lump this taxa together as tolerant of pollutants which is not necessarily true. In semi- arid regions taxa resolution of Chironomidae should be included in studies due to the high ecological and physiological diversity conveyed by the prevalent group.

Sabrina Moore (Primary Presenter/Author), Presbyterian College, Scmoore@presby.edu;

Katherine Cline (Co-Presenter/Co-Author), University of North Texas, katherinecline@my.unt.edu;

James Kennedy (Co-Presenter/Co-Author), University of North Texas, james.kennedy@unt.edu;

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6/04/2024  |   14:15 - 14:30   |  Independence Ballroom B

An evaluation of chironomid pupal exuviae technique (CPET) as an indicator of environmental quality in stormwater retention ponds along an urban gradient. Stormwater retention ponds, constructed primarily for services such as flood control, are abundant in urban landscapes and documented hotspots of aquatic biodiversity. A previous study we completed measured benthic community structure in five stormwater retention ponds in north-central Texas along an urban gradient. Results showed that chironomids (Diptera: Chironomidae) were the dominant macroinvertebrates in all five ponds. It was also determined that differences in the pond conditions associated with urban development could only be determined when chironomids were identified to the genus-level. However, collection and identification of chironomid larvae is often time-consuming. The objective of this present study is to evaluate the efficacy of the Chironomidae pupal exuviae technique (CPET) to detect changes in water quality in the same series of urban ponds in north-central Texas over one year. Based on results, CPET is an effective method of analyzing chironomid community response to environmental changes associated with anthropogenic impact. The CPET method reduced collection and laboratory processing time. A total of 16,635 surface-floating pupal exuviae were collected during this study, representing 81 chironomid taxa, which included 38 genera across three subfamilies. The chironomid communities changed between ponds in proportion to the intensity of the urban development within their watersheds. In addition, the method provided the emergence phenology of a highly diverse chironomid assemblage. Results indicated that CPET is an effective tool to monitor and evaluate the health of urban ponds.

Kaitlynn Davis (Primary Presenter/Author), University of North Texas, KaitlynnDavis@my.unt.edu;

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6/04/2024  |   14:30 - 14:45   |  Independence Ballroom B

CHIRONOMID SPECIES DISTINGUISH STRESSORS ALONG A GRADIENT OF URBANIZATION Chironomidae abundance is considered an indicator of stream degradation. In Maryland, genus-level tolerance values are applied to macrobenthos including chironomids. However, identification of chironomid larvae to genus is time-consuming and expensive. The goal of this study was to determine whether chironomid species, assessed by sampling floating pupal exuviae, could distinguish stressors in urban streams. Twenty-five streams in Baltimore City and County represented a gradient ranging from largely forested to suburban to highly urban watersheds. Chironomid pupal exuviae were collected every three weeks throughout the season. In-stream habitats were quantified with water chemistry, sediment structure and algal abundance variables. Mid-June chironomid emergence, a period of maximum species richness, yielded 104 species. Richness declined with increasing conductivity, reflecting application of road salt de-icers. Species richness was greatest at intermediate levels of attached algal abundance. Ordination of environmental variables depicted a dominant urban gradient of increasing conductivity, calcium, nutrients and sediment-bound metals, and a secondary gradient contrasting sandy bed sediment with coarser substrate and greater cover of the macroalga Cladophora. Ordination of chironomids emphasized the interrelation of environmental variables but distinguished sites with sediment metal concentrations exceeding probable effects levels for copper, zinc and lead. Two-way cluster analysis of chironomid species produced ecologically interpretable groups of streams. Chironomids dominating the “high metals” group differed from those of the “highest conductivity” group at the species level but not always at the genus level. Quantitation of species’ tolerance and optimal habitat will aid understanding of biological responses to stream restoration.

Susan Gresens (Primary Presenter/Author), Towson University, sgresens@towson.edu;

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6/04/2024  |   14:45 - 15:00   |  Independence Ballroom B

Long-term emergence patterns of Chironomidae (Diptera) from a temperate intermittent stream Extreme environmental conditions in intermittent habitats filter aquatic communities based on the ability of organisms to recolonize habitats quickly, survive periods of drying, and sometimes also survive freezing. Although intermittent streams often support interesting, specialized species, they tend to support a less species rich community than their perennial counterparts. I collected Chironomidae from an intermittent, 3rd order stream biweekly for 6 years using surface floating pupal exuviae. In most years, the stream flowed from March to July/August, dried for 4-6 weeks, rewetted in August/September, and flowed until the stream froze in December. However, this pattern was not always repeated and in one year the stream was dry for 7 months and in another there were multiple drying-rewetting cycles in late summer. More than 150 species of midge were identified, but many species (62) were rare (<5 individuals). Common taxa had regular emergence patterns and either had a synchronous spring emergence or continuous emergence during the periods of flow. Common taxa with continuous emergence patterns usually resumed emergence within 2-3 weeks after the stream rewetted. Emergence timing appeared to follow temperature and flow cues; however, differences in the duration of the dry period preceding emergence did not impact chironomid emergence timing. Intermittent streams are usually expected to only support a depauperate community of facultative species, but these habitats can support interesting and diverse communities that should be protected.

Will Bouchard (Primary Presenter/Author), Minnesota Pollution Control Agency and University of Minnesota, bouc0048@umn.edu;

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