Browsing by Subject "Aquatic insects"

Now showing 1 - 4 of 4
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    Diversity and distribution of the Caddisflies (Insecta: Trichoptera) of Ecuador
    (2017) Ríos-Touma, Blanca; Holzenthal, Ralph W.; Huisman, Jolanda; Thomson, Robin; Rázuri-Gonzales, Ernesto
    Background. Aquatic insects and other freshwater animals are some of the most threatened forms of life on Earth. Caddisflies (Trichoptera) are highly biodiverse in the Neotropics and occupy a wide variety of freshwater habitats. In Andean countries, including Ecuador, knowledge of the aquatic biota is limited, and there is a great need for baseline data on the species found in these countries. Here we present the first list of Trichoptera known from Ecuador, a country that harbors two global biodiversity ‘‘hotspots.’’ Methods.We conducted a literature review of species previously reported from Ecuador and supplemented these data with material we collected during five recent field inventories from about 40 localities spanning both hotspots. Using species presence data for each Ecuadorian province, we calculated the CHAO 2 species estimator to obtain the minimum species richness for the country. Results. We recorded 310 species, including 48 new records from our own field inventories for the country. CHAO 2 calculations showed that only 54% of the species have been found. Hydroptilidae and Hydropsychidae were the most species rich families. We report the family Xiphocentronidae for the first time from Ecuador as well as several new records of genera from different families. Discussion. As in the neighboring Andean countries of Colombia and Peru, it is common to find undescribed species of caddisflies. There are vast areas of Ecuador and the northern Andes that are completely unexplored, and we expect that hundreds of new species are yet to be discovered.
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    Evaluation of the potential effects of methoprene and BTI (Bacillus thurinqiensis israelensis) on wetland birds and invertebrates in Wright County, MN, 1988 to 1993
    (University of Minnesota Duluth, 1995) Niemi, Gerald J; Axler, Richard P; Hanowski, JoAnn M; Hershey, Anne E; Lima, Ann R; Regal, Ronald R; Shannon, Lyle J
    This report summarizes the results of a six year study (1988 to 1993) to assess the potential effects of two mosquito control materials, methoprene (applied as Altosid sand granules) and Bacillus thuringiensis var. israelensis (Bti, applied as Vectobac-G granules) on zooplankton, aquatic insects, and breeding birds in the Twin Cities metropolitan area. The study was a before-and-after design with 1988 to 1990 as pre-treatment and 1991 to 1993 as treatment years. A total of 27 wetlands in western Wright County were randomly selected and randomly placed within one of three groups of sites: 9 control, 9 Bti-treated, and 9 methoprene-treated. Selected populations of zooplankton, aquatic insects, and breeding birds were sampled within each of these wetlands. Each site was also monitored to verify the applications of Bti or methoprene to the respective sites and to verify that the control sites were not treated. In 1992, the number of study sites was reduced to 26 because of the loss of one methoprene-treated site from sampling. No effects could be attributed to treatment on zooplankton or breeding birds. Aquatic insects, however, were considerably reduced following treatments in 1992 and 1993. Chironomids comprised approximately 60% of the total individuals sampled, and were greatly reduced in both methoprene and Bti sites compared to controls. We focused on this group particularly because of their abundance, but also because they are closely related to mosquitoes and known to be susceptible to both larvicides. However, our results showed that all insect groups were similarly affected by both larvicides. Both Bti and methoprene applications to these wetlands reduced aquatic insect densities by a range of 57-83% and biomass by a range of 50-83% in the second and third years of treatment. Following the effects of treatments observed in 1992, populations of aquatic insects recovered to pre-treatment levels at the start of 1993, but quickly declined again following treatment. No food chain effects of these declines, with the possible exception of increases in the density of some copepods in methoprene-treated sites, were observed in either zooplankton or in breeding birds. High nest loss rates due to predation may have been a greater limiting factor to birds than mosquito control treatment. The carrying capacity of bird populations may also be lower than that affected by food reductions, especially since alternative foods tended to be available for Red-winged Blackbirds outside of the wetland study sites. Even though this study represents one of the largest ever conducted to assess the effects of mosquito control materials on non-target organisms, a variety of questions regarding the overall effects of mosquito control treatments remain unanswered. Among the most pressing questions are the determination of the long term effects (e.g., > 5-10 yrs) of the control program and whether populations of aquatic insects can continue to recover within these treated areas.
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    Identifying The Impacts Of Excess Fine Sediment On Benthic Macroinvertebrate Communities
    (2016-03) Herrera, Larissa
    Many streams throughout the United States are negatively impacted by excess fine sediments (sand, silt, and clay). Benthic macroinvertebrates are a commonly-used tool to assess stream condition; however, current methodologies typically are not able to distinguish among stressors. Previous studies have correlated macroinvertebrate communities and traits with excess fine sediments, demonstrating that aquatic macroinvertebrates are sensitive to deposited fine sediment and the assemblages will shift in response. Western Lake Superior streams have a wide range of fine sediment amounts due to clay and sand soils, but have low amounts of other stressors, and thus are a good region to investigate relationships between macroinvertebrate traits and fine sediments. Data were collected from 22 stream sites located along the north shore of Lake Superior in 2010. The data collected in 2010 did not have the desired gradient of fine sediment due to wet conditions that year; therefore, the data were supplemented with data collected by NRRI personnel in earlier years (1997 – 2008). The five sediment stressors used in analyses included percent embeddedness, depth of fine sediments, total percent fine sediments, percent sand, and a combined sediment index created using normalized and transformed embeddedness, depth of fine sediments and total percent fine sediments. Fifty-seven specific taxonomic groups and macroinvertebrate physical and behavioral characteristics (traits) were tested as potential response metrics in linear regressions. In addition, TITAN analyses were used to look for thresholds or sediment stressor values at which a taxon increases greatly, decreases greatly, or disappears from a community. Both the linear regressions and TITAN analyses showed a change in the community structure under conditions of excess sediment in the form of embeddedness, total fines, depth of fines, and/or the combined sediment index. The TITAN analyses also showed a change in the community structure due to increasing proportion sand in the streambed. Furthermore, the analyses identified potential characteristics that may specifically make a particular macroinvertebrate more or less vulnerable to excess fine sediments.
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    Systematics Of Cernotina Ross And Cyrnellus Banks (Insecta: Trichoptera: Polycentropodidae)
    (2020-07) Camargos, Lucas
    The family Polycentropodidae occurs worldwide, and is represented in the Americas by Cernotina Ross 1938, Cyrnellus Banks 1913, Nyctiophylax Brauer 1865, Polycentropus Banks 1907 and Polyplectropus Ulmer 1905. Cernotina and Cyrnellus are exclusive to the New World, reaching their highest diversity in the Neotropics, with 75 and 12 described species respectively. Despite this diversity, none of the two have had revisionary work done, and the taxonomic information is scattered in many different papers by many authors across the 20th and early 21st Century. In Chapter 1, I ran the first phylogenetic analyses on the diverse genus Cernotina, using morphological characters of the male adult, especially the genitalia. To analyze the character matrix, I used Maximum Parsimony and Bayesian inference. In Maximum Parsimony, I used equally-weighted analyses with two different search strategies, one simple run and another with multiple rounds saving suboptimal trees to filter for a better set of most parsimonious trees, and an implied-weights analysis, using a posteriori character weigthing to achieve better resolution. In the Bayesian inference, I used Mk model + lognormal distribution, commonly used in morphological data. The results suggest the monophyly of Cernotina, adds phylogenetic evidence for synonymization of Ce. perpendicularis with Ce. lanceolata, and Ce. hastilis with Ce. nigridentata, and group certain species with morphological and geographic congruence, such as Ce. acalyptra + Ce. cystophora + Ce. encrypta, and Ce. lutea + Ce. cadeti, respectively. However, the overall resolution of the simple maximum-parsimony and the Bayesian trees were very low. In addition, the branch support for most nodes is also very low. This result might be due to the nature of the genitalic characters of Cernotina, being extremely variable on all its components, making the task of finding character congruence difficult. With additional data such as DNA sequence and geometric morphometrics, such issues could be alleviated. In Chapter 2, I revised the genus Cernotina at species-level. I discussed the complex homology of the morphological characters of the male genitalia, especially concerning the intermediate appendage and its relation to the Xth tergum and the preanal appendage, produced illustrations and comparative diagnoses for each species in the genus, and taxonomic descriptions for 64 species. In addition, I described 16 new species. I also proposed 2 synonymies considering the phylogenetic data from Chapter 1: Ce. lanceolata as junior synonym of Ce. perpendicularis, and Ce. nigridentata as junior synonym of Ce. hastilis. In Chapter 3, I revised the genus Cyrnellus at species-level. I also discussed the homology of the morphological characters of the much simpler male genitalia of the genus, produced a key to species of Cyrnellus, provided illustrations, and full taxonomic descriptions for 11 species. In addition, I reinstated the validity of Cy. minimus based on the morphology of the inferior appendage in ventral view. I also synonymized 2 species based on morphological similarity and high variability among specimens: Cy. keskes as junior synonym of Cy. minimus, and Cy. kozepes as junior synonym of Cy. ulmeri.