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Trichoptera: Glossosmatidae of Gunnison County, Colorado

Agapetus boulderensis Saddle Case Caddis

Milne, 1936
Updated 11Nov2015
TSN 117145

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Canton,SP and Ward,JV 1981 The aquatic insects, with emphasis on Trichoptera, of a Colorado stream affected by coal strip-mine drainage. Southwestern Naturalist 25 4, 453-460. PDF
     They studied Trout Creek where it runs through the Edna Coal Mine in northwestern Colorado. The mine spoils were 30 meters from the edge of the creek (approximately a 100 foot buffer zone). They found the aquatic insect density (numbers per square meter) and biomass (weight in grams per square meter) did not change above and below the mine. The Shannon-Weaver Diversity index also showed no difference between sites. However the community structure (which species were present and proportions) did change. Since there were irrigation water and cattle influences at their downstream site, their results may reflect these additional water uses. They note the biggest visible change at this mine is the loss of willow and alder trees downstream of the mine. The caddisfly population changed the most between sites, shifting from a mix of families above the mine to dominance by Hydropsychidae and Glossosomatidae below the mine.
Quote from page 457: "Glossosomatids (Glossosoma ventrale and Agapetus boulderensis) were abundant at both locations. At C2 (upstream of mine) the comprised 33% of the trichopterans; at C4 (below the mine) they clearly dominated the caddisfly community with increased abundance of both species, and accounted for 64% of the density."

Etnier,DA; Parker,CR; Baxter,JT and Long,TM 2010 A review of the genus Agapetus Curtis (Trichoptera: Glossosomatidae) in eastern and central North America, with description of 12 new species. Insecta Mundi, 149:1-77.

Herrmann,SJ; Ruiter,DE and Unzicker,JD 1986 Distribution and records of Colorado Trichoptera. Southwestern Naturalist 31 4, 421-457.
     They note the habitat for this species is streams and rivers, the altitudinal range is 1975-2749 m and adult collection dates are 3 August to 2 October. Quote from page 425 "Our data show this species to be more widespread in Colorado than previously reported." They list this species as present in Gunnison county.

Hoffman,AL; Olden,JD; Monroe, JB; Poff, NL; Wellnitz,T and Wiens, JA 2006 Current velocity and habitat patchiness shape stream herbivore movement. Oikos, 115(2), 358-368. PDF on ResearchGate
     Abstract: " Animal movements are influenced by the structure and arrangement of patches in a landscape. Most movement studies occur in terrestrial landscapes, though aquatic landscapes are equally heterogeneous and feature patches that differ in resistance to animal movements. Furthermore, the variable and highly directional flow of water over streambed landscapes is a unique environmental element, yet its constraint on animal movement is poorly understood. This study examines how habitat availability in a streambed landscape interacts with current velocity to affect movement patterns of two benthic grazers: glossosomatid caddisfly larvae (Agapetus boulderensis) and pulmonate snails (Physa sp.). Using experimental streambed landscapes, we found that Agapetus traveled farther as availability of smooth habitat (composed of low diatom turfs) increased compared to tall, structured filamentous stands, but only did so in slow current velocities. Swifter flows caused restricted movement of Agapetus and more upstream-oriented paths, but only in smooth landscapes where the potential for flow refugia from filamentous stands was minimal. Similarly, increasing proportions of smooth habitat facilitated greater net displacement of Physa using more upstream-oriented paths. Higher current velocities caused Physa to move faster, a pattern demonstrated only in smooth landscapes.

Our results illustrate a strong interaction between benthic habitat structure and current velocity in shaping patterns of grazer movements in a streambed landscape. Our study also suggests that the flow of water be considered not only a strong environmental gradient in streams, but also an interactive landscape feature that can combine with streambed structure to determine the permeability of patches to the movement of benthic organisms. Landscape ecology has mainly focused on terrestrial environments, and this study offers insight into some of the unique processes that may shape animal movement in aquatic environments."

McCahonCP; Whiles,AJ and Pascoe,D 1989 The toxicity of cadmium to different larval instars of the trichopteran larvae Agapetus fuscipes Curtis and the importance of life cycle information to the design of toxicity tests. Hydrobiologia, 185(2), 153-162. Abstract

Mecom, John O. 1972a Feeding habits of Trichoptera in a mountain stream. Oikos 23: 401-407.
     Agapetus larvae ate diatoms or detritus, changing with the seasons.

Milne,LJ 1936 Studies in North American Trichoptera. Part 3. Cambridge, Mass. : Author's publication. 128 pages

Monroe,JB and Olden,JD 2008 Aqua-Rock Climbers. Natural History.

Olden,JD 2007 Critical threshold effects of benthiscape structure on stream herbivore movement. Philosophical Transactions of the Royal Society B: Biological Sciences, 362 (1479) 461-472. Abstract
     Abstract: " In landscape ecology, substantial theoretical progress has been made in understanding how critical threshold levels of habitat loss may result in sudden changes in landscape connectivity to animal movement. Empirical evidence for such thresholds in real systems, however, remains scarce. Streambed landscapes provide a strong testing ground for studying critical thresholds because organisms are faced with substantial environmental heterogeneity while attempting to overcome the physical force of water. In this study, I report on the results from a series of experiments investigating the influence of habitat abundance and current velocity on the movement dynamics of two stream herbivores (caddisfly larva Agapetus boulderensis and snail Physa sp.) that differ substantially in how they perceive landscape structure. Specifically, I ask whether critical thresholds to herbivore movement exist in streambed landscapes. By exploiting the pattern recognition capabilities of artificial neural networks, I found that the rate, sinuosity and directionality of movement by Agapetus and Physa varied nonlinearly according to the abundance of habitat patches, current velocity and habitat-current interaction. Both the study organisms exhibited threshold responses to habitat abundance, yet the location and slope of these thresholds differed between species and with respect to different current velocities. These results suggest that a critical threshold in functional connectivity (i.e. the connection of habitat patches by dispersal) is not an inherent property of the landscape, but in fact emerges from the interplay of species' interactions with landscape structure. Moreover, current velocity interacted with habitat abundance to elicit strong upstream-oriented movement for both the species. This suggests that dispersing individuals may be polarized in the upstream direction and therefore functional connectivity is not equal in all directions. Such results highlight the need for future research addressing the sources of variability of critical threshold effects in ecological phenomena."

Olden,JD 2010 Current velocity shapes the functional connectivity of benthiscapes to stream insect movement. Modelling Perception with Artificial Neural Networks, 351. Abstract
     Uses A. boulderensis as a study organism.

Olden,JD; Hoffman,AL; Monroe,JB; and Poff,NL 2004 Movement behaviour and dynamics of an aquatic insect in a stream benthic landscape. Canadian Journal of Zoology 82:1135-1146. PDF.

Poff,NL and JV Ward. 1992 Heterogeneous currents and algal resources mediate in situ foraging activity of a mobile stream grazer. Oikos 65:465-478. PDF
     Abstract: " The importance of spatial heterogeneity in near-bed currents and algal resource patchiness in regulating the movement patterns, foraging activities, and distribution of the mobile stream insect, Agapetus boulderensis Milne (Glossosomatidae: Trichoptera) was investigated with field observational studies and field experiments. Near-bed current velocities were characterized for topographically-complex substrata concurrently with spatial patterns of algal density and taxonomic composition. Activities of self-marked mobile larvae were examined in relationship to mapped current and algal resources. Near-bed currents alone influenced the distribution and local abundance of individuals in a size-dependent fashion - fifth (final) instar larvae occurred across a velocity range of < 5 to 50 cm s-1, while smaller third and fourth instar larvae were found only at currents ranging from < 5 to 30 cm s-1. Agapetus movement was also constrained by local current. Direction of movement on stone surfaces was significantly into or lateral to oncoming flow. Rate of movement was inversely related to local current speed and positively related both to temperature and to travel in the upstream direction. Agapetus movement and foraging were also related to algal density and taxonomic composition. Movement rate was inversely correlated with estimated diatom density but positively correlated with densities of green and blue-green algae for larvae on one stone. Gut analysis revealed a significant positive preference by Agapetus for diatoms, particularly Cocconeis placentula, which was overrepresented in the gut relative to other diatoms or to blue-green algae. Together, patterns of local current and of algal distribution and composition were important descriptors of movement and foraging activity of this mobile grazer under naturally heterogeneous field conditions. A field experiment under controlled conditions of current and algal density showed both factors were independent and non-interactive determinants of grazer movement rates. This study supports previous research showing the importance of algal patchiness in mediating grazer foraging activity and distribution, but it further indicates that patterns of resource use by grazers may be constrained by heterogeneous local currents, independent of the effects of food distribution and abundance. "

Poff,NL and Ward,JV 1995 Herbivory under different flow regimes: a field experiment and test of a model with a benthic stream insect. Oikos, 179-188. PDF
     Abstract: "An experiment was conducted in an open-canopy mountain stream to examine the effects of different densities of the grazing caddisfly Agapetus boulderensis (Trichoptera: Glossosomatidae) on algal biomass and assemblage structure at two current velocities. Unglazed ceramic tiles were colonized by algae in grazer-free troughs for 30 d at slow (? 20 cm s-1) and fast (? 40 cm s-1) velocities before transfer to open troughs of similar velocity, where they were exposed to grazer densities ranging from ca 0.7 to 2.7 times natural streambed densities. At low velocity, algal biomass (chl-a and particulate C) and absolute densities of bacillariophytes, chlorophytes and cyanophytes declined as grazer density increased. Grazers also significantly altered algal assemblage structure by reducing the relative abundance of cyanophytes (mostly Anabaena cf. affinis) and chlorophytes (Ulothrix zonata) and increasing the relative abundance of some bacillariophytes (Cocconeis placentula, Fragilaria pinnata, F. vaucheriae, Melosira italica). The algal assemblage was effectively converted from a "late-successional" to an "early-successional" stage by grazers. By contrast, at high velocity, initial algal density was relatively low and grazers were less effective in inducing changes. As grazer density increased, total algal cell abundance (mostly bacillariophytes) declined, although the relative abundances of individual diatom species remained unmodified under increasing grazer densities. Grazers essentially maintained the "early-successional" nature of the algal assemblage under high velocity conditions. Further, for both current velocities, we tested a model that predicts algal biomass as a function of grazer density and time. Independent estimates of current-dependent grazing rate and algal growth rate were used in the model to generate predictions of particulate C along a gradient of grazer density at two current velocities. Algal biomass predicted by the model compared favorably with an empirical fit of the data under low and high velocities. These results suggest that the role of grazers in structuring algal assemblages may vary spatially with local current velocity in heterogeneous stream systems. "

Ross, HH 1951 Phylogeny and biogeography of the caddisflies of the genera Agapetus and Electragapetus (Trichoptera: Glossosomatidae) Journal of the Washington Academy of Sciences 41 (11) 347-356.

Ross, HH 1956 Evolution and classification of the mountain caddisflies. University of Illinois Press, Urbana, 213 pages.

Voelz,NJ; Poff,NL; Ward,JV 1994 Differential effects of a brief thermal disturbance on caddisflies (Trichoptera) in a regulated river. American Midland Naturalist 132 1, 173-182.
     Abstract: " During studies on filter-feeding and grazing caddisflies in the regulated upper Colorado River, a problem developed with the deep-release mechanism of Granby Dam and water had to be released from the surface for 16 days in August 1986. Maximum water temperatures exceeded the normal summer maxima by at least 4-5 C for up to 12 km below the reservoir. Samples taken along the longitudinal profile below the reservoir showed that populations of several caddisflies species, which had been numerically abundant in previous years, were virtually eliminated after this period of increased water temperature. Some species experienced immediate reductions, presumably due to larval/pupal mortality (e.g., Brachycentrus americanus, Glossosoma ventrale, G. parvulum), while others exhibited lagged responses over the next several months, presumably due to reduced hatching success and extensive winter mortality (e.g., Glossosoma verdona). Interestingly, at some sites, B. americanus and other caddisfly species were largely unaffected by the elevated temperatures. Species showing the greatest resilience to the thermal disturbance were either those having abundant terrestrial adults present at the time (e.g., Agapetus boulderensis) or those potentially having broad thermal tolerances (e.g., Brachycentrus occidentalis). Most studies concerning the effects of extreme temperature change on lotic organisms have dealt with heated effluents or the general thermal impacts induced by river regulation. This is the first report, that we are aware of, detailing the potential effect of short-term elevated temperatures on lotic macroinvertebrates in a river regulated by a deep-release dani."

Wellnitz,TA; Poff,NL; Cosyleón,G and Steury,B 2001 Current velocity and spatial scale as determinants of the distribution and abundance of two rheophilic herbivorous insects. Landscape Ecology, 16(2), 111-120. PDF
     Abstract: "Organisms frequently show marked preferences for specific environmental conditions, but these preferences may change with landscape scale. Patterns of distribution or abundance measured at different scales may reveal something about an organism's perception of the environment. To test this hypothesis, we measured densities of two herbivorous aquatic insects that differed in body morphology and mobility in relation to current velocity measured at different scales in the upper Colorado River (Colorado, USA). Streambed densities of the caddisfly larva Agapetus boulderensis (high hydrodynamic profile, low mobility) and mayfly nymph Epeorus sp. (low hydrodynamic profile, high mobility) were assessed at 3 spatial scales: whole riffles, individual cobbles within riffles, and point locations on cobbles. Riffles were several meters in extent, cobbles measured 10-30 cm in size, and the local scale was within a few centimeters of individual larvae (themselves ca. 0.5-1.0 cm in size). We also quantified the abundance of periphytic food for these herbivores at the cobble and riffle scales. Agapetus favored slow current (<30 cm s-1) across all scales. Epeorus, by contrast, favored fast current (60-80 cm s-1) at the local and riffle scale, but not at the cobble scale. Only Agapetus showed a significant relationship to current at the cobble scale, with greatest larval densities occurring at velocities near 30 cm s-1. We had predicted an inverse correlation between grazer density and periphytic abundance; however, this occurred only for Agapetus, and then only at the cobble scale. These data suggest that organisms respond to environmental gradients at different spatial scales and that the processes driving these responses may change with scale, e.g., shifting from individual habitat selection at local and cobble scales to population responses at the riffle scale. This study also highlights the importance of using the appropriate scale of measurement to accurately assess the relationship between organisms and environmental gradients across scale. "

Brown,WS 2005 Trichoptera of Gunnison County, Colorado, USA