Baetis bicaudatus (Ephemeroptera: Baetidae) of Gunnison County, Colorado

Ephemeroptera: Baetidae of Gunnison County, Colorado

Baetis bicaudatus
Small Minnow Mayfly, Iron Blue Dun, Blue-winged Olive, BWO, Little dark blue winged olive #20

Dodds 1923

Updated 17 August 2024
TSN 100823

A Baetis snack for a stonefly. Notice two tails on the Baetis larvae. Caught and released from the Upper East river on 2Aug2011.

Description

This is a classic two-tailed (bi-caudatus) Baetis species. Widespread in Western North America, they have indistinct markings on their body, but a bilobed mark on the pronotum.

Notes

This is one of the rhodani group of Baetis species.

Good Links

On this website:
Introduction to Baetis
Key to Baetis Nymphs

Outside websites:
Hatch Chart for the Gunnison Gorge & Black Canyon from Cimarron Creek Guides in Montrose http://cimarroncreek.com/flyfishing/hatchchart.cfm

Photos, Map, Museum specimens, DNA - Barcodinglife.org

References

Allan,JD 1978a Diet of brook trout (Salvelinus fontinalis Mitchell) and Brown Trout (Salmo trutta L.) in an alpine stream. Internationale Vereinigung für Theoretische und Angewandte Limnologie Verhandlungen 20, 2045-2050.
     Abstract: "Diurnal drift of stream invertebrates is examined as a predator avoidance adaptation via the hypothesis that those taxa or growth stages which are large, and thus subject to intense predation relative to smaller forms, should be most strongly constrained to nocturnal drift activity. Smaller taxa or stages may be aperiodic or day active. Data from an alpine stream document for the abundant and widespread mayfly Baetis bicaudatus that, on a continuum from small to large size, the risk of predation increases while the propensity to drift during the day decreases. There is supporting and some contrary evidence from the literature for the generality of this pattern."
This research was conducted in Cement Creek, a tributary of the East River in the Gunnison Basin of Colorado.

Allan,JD 1981 Determinants of diet of brook trout (Salvelinus fontinalis) in a mountain stream. Canadian Journal of Fisheries and Aquatic Sciences 38, 184-192. PDF

Allan,JD 1984 The size composition of invertebrate drift in a Rocky Mountain stream. Oikos, pp.68-76.

Allan,JD 1987 Macroinvertebrate drift in a Rocky Mountain stream. Hydrobiologia 144, 261-268.
     The author studied Cement Creek in Gunnison County during the spring, summer and fall of 1975-1978. He found that drift densities (number of animals per 100 m³ of water) was 10 times higher at night. 24 hour totals approached 2000 animals/100m³ in mid-summer down to 500 animals/m³ in the fall. Quote from the abstract: "Ephemeroptera, especially Baetis, dominated the drift." He found that benthic density (number of animals/m² from streambed samples) was the best predictor of 24hr drift rate for Baetis bicaudatus. Adding discharge to the calculation (a stepwise regression) helped predict the number of B. bicaudatus in the drift.

Allan,JD; Flecker,AS and McClintock,NL 1987 Prey size selection by carnivorous stoneflies. Limnol. Oceanogr. 32(4), 864-872. PDF
     Abstract: "To investigate prey size preference by carnivorous stoneflies, we conducted choice experiments and directly observed predatory behavior in laboratory streams. Small, medium, and large size classes of Hesperoperla pacifica (Perlidae), small Kogotus modestus, and medium and large Megarcys signata (both of the Perlodidae) were offered an array of sizes of the mayfly Baetis as prey. Small predators displayed strong positive selection for the smallest size class of prey, and preference declined steadily with increasing prey size. Large predators displayed hump-shaped preference curves, exhibiting strongest preference for intermediate size classes of prey. Thus size selectivity was demonstrated and varied with the size class of predator. Direct observations of encounters between predators and their prey revealed that percent attacks/ encounters by small predators was strongly biased toward small prey and by large predators was weakly biased toward large prey. Capture success always was greater and handling times shorter with small prey compared to large prey."

Allan,JD and Russek,E 1985 The quantification of stream drift. Canadian Journal of Fisheries and Aquatic Sciences 42:210-215. PDF
     Although the purpose of many drift studies is to describe quantitatively the abundance of drifting invertebrates and make comparisons between seasons or sites, almost no investigations have employed replicate sampling. We analyzed drift collections from a Rocky Mountain stream in order to investigate the variability of drift sampling. The data were normalized and the variances stabilized for each taxon examined by data transformation. The fourth root transformation was favored for five taxa and the logarithmic transformation for three. Using the 95% confidence limits on 24-k drift density for an abundant mayfly (Baetis bicaudatus), we found that six to seven replicates are required to obtain 95% CL + 58% of the mean. Drift sampling appears to require fewer replicates than benthic sampling for comparable precision. Investigators may fail to replicate drift samples because they elect to sample frequently over 24 hr in order to quantify the diel periodicity of drift. However, when comparison between sites or dates is the principal goal, we recommend that the effort normally put into frequent sampling over 24 h be invested instead in replicated sampling just after dark, whew drift normally is greatest. When we regressed drift from the first night sample against total drift from the remainder of the 24-h period, 60-90% of the variation in the latter was predicted from the single nighttime sample. Thus, little information appears to be lost by this recommended procedure.

Àlvarez,M; Landeira-Dabarca,A and Peckarsky,B 2014 Origin and specificity of predatory fish cues detected by Baetis larvae (Ephemeroptera; Insecta). Animal Behaviour, 96, pp.141-149. PDF
     Abstract: "Some prey respond to predator cues by altering their behaviour, but the response may depend on predator diet and identity. There are few data on how predator feeding status and diet affect the behaviour of aquatic insects and on the specificity of the response of these prey to different predators. We present the results of four bioassays conducted in microcosms to evaluate the relationship between predator fish diet, predator identity and the predator avoidance behaviour of mayfly prey of the genus Baetis to elucidate the origin and specificity of the antipredator response. Results from the first bioassay indicated that the response of Baetis to predatory trout is independent of diet, which enabled us to rule out the following potential origins of the signal: alarm cues emitted by wounded Baetis conspecifics, salivary enzymes released by feeding fish and excretion products that may contain Baetis and conspecific odours. Thus, we focused further experiments on fish cutaneous mucus as the potential origin of cues that cause Baetis to reduce its activity. In two bioassays, we observed that North American Baetis bicaudatus did not distinguish between five freshwater fish species that co-inhabit the same drainage, despite differences in their relative risk of predation (four predatory salmonid species and one omnivorous sucker species). However, in another bioassay, we observed that European Baetis rhodani larvae did not respond to cutaneous mucus of novel predators (carp, seawater turbot or frog), indicating that Baetis do not show a general response to all mucus donor organisms. Our bioassays identified mucus as the potential origin of the cue eliciting antipredator behaviour in Baetis, providing much needed insight into the specificity of fish-associated chemical cues that cause some prey to respond. Experimental approaches similar to the one used in this study may increase our understanding of the role of chemical cues in aquatic ecosystems."

Àlvarez,M and Peckarsky,BL 2005 How do grazers affect periphyton heterogeneity in streams? Oecologia 142: 576-587. PDF
     Abstract: "The effects of grazing by stream invertebrates on algal biomass and spatial heterogeneity were tested experimentally in flow-through microcosms with natural substrates (rocks). One experiment tested the effects of fixed densities of three species of grazers (the caddisfly Allomyia sp. and two mayflies, Epeorus deceptivus and Baetis bicaudatus) on periphyton. Baetis was tested with and without chemical cues from fish predators, which reduced grazer foraging activity to levels similar to the less mobile mayfly (Epeorus). Mean algal biomass (chlorophyll a; chl a) was reduced in grazer treatments compared to ungrazed controls, but there were no differences among grazer treatments. Algal heterogeneity (Morisita index) increased with grazer mobility, with the highest heterogeneity occurring in the Baetis-no fish treatment (most mobile grazer) and the lowest in the caddisfly treatment (most sedentary grazer). A second experiment used a three factorial design, and tested whether initial resource distribution (homogeneous vs. heterogeneous), Baetis density (high vs. low) and fish odor (present vs. absent) affected grazer impact on algal resources. Abundances of Baetis and chl a on individual rocks were recorded to explore the mechanisms responsible for the observed distributions of algae. Initial resource heterogeneity was maintained despite being subjected to grazing. Mean chl a was highest in controls, as in experiment I, and effects of Baetis on algal biomass increased with grazer density. There were no fish effects on algal biomass and no effects of grazer density or fish on algal heterogeneity. At the scale of individual rocks Baetis was unselective when food was homogeneously distributed, but chose high-food rocks when it was heterogeneously distributed. Results of these mechanistic experiments showed that Baetis can track resources at the scale of single rocks; and at moderate densities mobile grazers could potentially maintain periphyton distributions observed in natural streams."

Àlvarez,M and Peckarsky,BL 2013 The influence of moss on grazers in high-altitude streams: food, refuge or both? Freshwater Biology, 58(9) 1982-1994. PDF

Àlvarez,M and Peckarsky,BL 2014 Cascading effects of predatory fish on the composition of benthic algae in high-altitude streams. Oikos, 123(1)120-128. PDF

Ball,SL; Hebert,PDN; Burian,SK; Webb,JM 2005 Biological identification of mayflies (Ephemeroptera) using DNA barcodes. Journal of the North American Benthological Society 24(3) 508-524.

Corkum LD and Clifford HF 1981 Function of caudal filaments and correlated structures in mayfly nymphs, with special reference to Baetis (Ephemeroptera). Quaestiones Entomologicae 17: 129-146. PDF

Cowan CA and Peckarsky BL. 1990 Feeding by a lotic mayfly grazer as quantified by gut fluorescence. Journal of the North American Benthological Society 9(4)368-378. PDF

Cowan,CA and Peckarsky,BL 1994 Diel feeding and positioning periodicity of a grazing mayfly in a trout stream and a fishless stream. Canadian Journal of Fisheries and Aquatic Sciences, 51(2), pp.450-459.
     Abstract: "We studied the feeding and positioning periodicity on natural substrates of the overwintering and fast-growing summer generations of a grazing mayfly, Baetis bicaudatus, in a third-order trout stream and a fishless, first-order tributary in western Colorado. At 4-h intervals over 24-h, we recorded the number of Baetis on stone tops in flow-through enclosures in situ and in streamside circular flow-through chambers. We determined the feeding periodicity of Baetis using abundance of plant pigments as an index of gut fullness. Baetis were nocturnal in the trout stream; more animals were found on stone tops and guts were fuller at night, suggesting that individuals came to stone tops to feed during darkness. However, Baetis from the fishless stream were either aperiodic or weakly nocturnal. We tested the hypothesis that nocturnal feeding by Baetis is a response to the presence of visually feeding trout by conducting transplant experiments in the circular streams. After 24 h, Baetis transferred from the trout stream to fishless water remained strongly nocturnal, while Baetis transferred from the fishless stream to trout water became significantly more nocturnal, suggesting that the risk of fish predation outweighs the benefits of relaxing nocturnal periodicity to feed continuously."

Dodds,GS 1923 Mayflies from Colorado: descriptions of certain species and notes on others. Transactions of American Entomological Society 69, 93-116.
     Dodds described Baetis bicaudatus in this paper.

Encalada,AC and Peckarsky,BL 2006 Selective oviposition of the mayfly Baetis bicaudatus. Oecologia, 526-537. PDF
     Abstract: "Selective oviposition can have important consequences for recruitment limitation and population dynamics of organisms with complex life cycles. Temporal and spatial variation in oviposition may be driven by environmental or behavioral constraints. The goals of this study were to: (1) develop an empirical model of the substrate characteristics that best explain observed patterns of oviposition by Baetis bicaudatus (Ephemeroptera), whose females lay eggs under rocks protruding from high-elevation streams in western Colorado; and (2) test experimentally selective oviposition of mayfly females. We surveyed the number and physical characteristics of potential oviposition sites, and counted the number and density of egg masses in different streams of one watershed throughout two consecutive flight seasons. Results of surveys showed that variability in the proportion of protruding rocks with egg masses and the density of egg masses per rock were explained primarily by seasonal and annual variation in hydrology, and variation in geomorphology among streams. Moreover, surveys and experiments showed that females preferred to oviposit under relatively large rocks located in places with high splash associated with fast current, which may provide visual, mechanical or both cues to females. Experiments also showed that high densities of egg masses under certain rocks were caused by rock characteristics rather than behavioral aggregation of ovipositing females. While aggregations of egg masses provided no survival advantage, rocks selected by females had lower probabilities of desiccating during egg incubation. Our data suggest that even when protruding rocks are abundant, not all rocks are used as oviposition sites by females, due to female selectivity and to differences in rock availability within seasons, years, or streams depending on variation in climate and hydrogeomorphology. Therefore, specialized oviposition behavior combined with variation in availability of quality oviposition substrata has the potential to limit recruitment of this species."

Encalada,AC and Peckarsky,BL 2011 Large-scale manipulation of mayfly recruitment affects population size. Oecologia. DOI 10.1007/s00442-0112147-1. PDF
     Abstract: " Recruitment establishes the initial size of populations and may influence subsequent population dynamics. Although strong inference can be made from empirical relationships between recruitment and population sizes, a definitive test of recruitment limitation requires manipulating recruitment at relevant spatial and temporal scales. We manipulated oviposition of the mayfly Baetis bicaudatus in multiple streams and measured the abundance of late-stage larvae at the end of the cohort. Based on fundamental knowledge of mayfly behavior, we increased, eliminated, or left unmodified preferred mayfly oviposition sites in 45-m reaches of streams (N = 4) of one high-altitude drainage basin in western Colorado, USA. We compared egg densities before (2001) and after the manipulation (2002) using paired t tests and compared larval densities before and after the manipulation among treatments using repeated measures analysis of variance. This manipulation altered not only egg densities, but also larval abundances 1 year later. Compared to the previous year, we experimentally increased egg densities at the addition sites by approximately fourfold, reduced egg densities to zero in the subtraction sites, and maintained egg densities in the control sites. After the manipulation, larval densities increased significantly by a factor of approximately 2.0 in the addition sites and decreased by a factor of approximately 2.5 in the subtraction sites. This outcome demonstrates that dramatic changes in recruitment can limit larval population size at the scale of a stream reach, potentially masking previously observed post-recruitment processes explaining the patterns of variation in abundance of a stream insect. Furthermore, our results emphasize the importance of preferred oviposition habitats to population sizes of organisms."

Fuller,MR and Peckarsky,BL 2011 Ecosystem engineering by beavers affects mayfly life histories. Freshwater Biology, 56(5), pp.969-979. PDF

Gilpin,BR and Brusven,MA 1970 Food habits and ecology of mayflies of the St. Maries River in Idaho. Melanderia 4:19-40. PDF

Harper,PP and Harper,F 1997 Mayflies (Ephemeroptera) of the Yukon. Pp. 152-167 In: H.V. Danks and J.A. Downes, eds. Insects of the Yukon. Biological Survey of Canada (Terrestrial Arthropods). Ottawa, Ontario, Canada. PDF

Harper,MP and Peckarsky,BL 2006 Emergence cues of a mayfly in a high-altitude stream ecosystem: potential response to climate change. Ecological Applications 16 (2) 612-621. PDF
     Abstract: "To understand the consequences of human accelerated environmental change, it is important to document the effects on natural populations of an increasing frequency of extreme climatic events. In stream ecosystems, recent climate change has resulted in extreme variation in both thermal and hydrological regimes. From 2001 to 2004, a severe drought in western United States corresponded with earlier emergence of the adult stage of the high-altitude stream mayfly, Baetis bicaudatus. Using a long-term database from a western Colorado stream, the peak emergence date of this mayfly population was predicted by both the magnitude and date of peak stream flow, and by the mean daily water temperature, suggesting that Baetis may respond to declining stream flow or increasing water temperature as proximate cues for early metamorphosis. However, in a one-year survey of multiple streams from the same drainage basin, only water temperature predicted spatial variation in the onset of emergence of this mayfly. To decouple the effects of temperature and flow, we separately manipulated these factors in flow-through microcosms and measured the timing of B. bicaudatus metamorphosis to the adult stage. Mayflies emerged sooner in a warmed-water treatment than an ambient-water treatment; but reducing flow did not accelerate the onset of mayfly emergence. Nonetheless, using warming temperatures to cue metamorphosis enables mayflies to time their emergence during the descending limb of the hydrograph when oviposition sites (protruding rocks) are becoming available. We speculate that large-scale climate changes involving warming and stream drying could cause significant shifts in the timing of mayfly metamorphosis, thereby having negative effects on populations that play an important role in stream ecosystems."

Hernandez,SA and Peckarsky,BL 2014 Do stream mayflies exhibit trade-offs between food acquisition and predator avoidance behaviors? Freshwater Science 33(1) 124-133.

Hughes,JM; Mather,PB; Hillyer,MJ; Cleary,C and Peckarsky,B 2003 Genetic structure in a montane mayfly Baetis bicaudatus (Ephemeroptera: Baetidae), from the Rocky Mountains, Colorado. Freshwater Biology 48, 2149-2162. PDF
     Abstract: "1. Populations of a number of sub-tropical stream insect species have been found to show unexpected patterns of genetic variation, with more differences between samples from the same stream than between whole streams or between subcatchments. Many samples also showed deviations from Hardy-Weinberg proportions. It has been proposed that these patterns result from limited numbers of matings contributing to a given stream reach, because adults emerge throughout the year, and low levels of larval drift between reaches. These patterns may be less likely in a northern hemisphere montane species with synchronous emergence of adults and high levels of drift. We tested the hypothesis that patterns of genetic variation in a montane mayfly from the Rocky Mountains, Colorado, would reflect a pattern of 'isolation by distance' with samples from the same creek being more similar than samples from different creeks and that deviations from Hardy-Weinberg proportions would be minimal.
2. Based on allozyme variation, the hypothesis of minimal deviations from Hardy-Weinberg proportions was not supported and there was no evidence of isolation by distance. Nevertheless the levels of differentiation among samples from within the same stream were less than those reported for most subtropical species.
3. Results from analysis of a fragment of the cytochrome oxidase gene (subunit 1) revealed contrasting patterns. The levels of genetic differentiation were an order of magnitude higher between streams than among samples within streams. In addition, although there was no significant isolation by distance effect overall, a nested clade analysis provided evidence for restricted gene flow with isolation by distance for some clades.
4. We suggest that these contrasting results may reflect the differences in male and female dispersal patterns. While differentiation at nuclear gene markers (allozymes) give information about both male and female dispersal, mitochondrial DNA markers reflect only female dispersal. We suggest that in this species, female dispersal may be more restricted, perhaps mostly along stream channels, whereas male dispersal is more widespread. An alternative explanation for the different results is the different evolutionary rates of the mitochondrial and nuclear markers."

Kerans,BL; Peckarsky BL and Anderson,C 1995 Estimates of mayfly mortality: is stonefly predation a significant source?. Oikos 74(2):315-323. PDF
     Abstract: " Field experiments and surveys were carried out in a Rocky Mountain alpine stream during the summers of 1990 and 1992 to estimate the proportion of natural losses of the mayfly Baetis bicaudatus resulting from the co-occurring, predatory stonefly, Kogotus modestus. Functional response experiments determined the number of prey consumed by male and female Kogotus by manipulating the densities of prey and the presence or absence of predators in stream-side chambers. Estimates of losses of Baetis and density of Kogotus were based on ten benthic samples collected weekly (except for last sampling date) from one study reach. Concurrently, drift density of Baetis was estimated upstream and downstream of the reach to determine gains or losses of Baetis resulting from migration. In the functional response experiments Kogotus consumed the same number of prey regardless of prey densities. Female predators tended to consume more prey (~ 2 d^-1) than males (~ 1 d^-1), although the result was only statistically significant in one out of three experiments. Per-capita mortality rates of Baetis declined from 0.01 to 0.001 d^-1 (predator m^-2)^-1 with increasing prey density. In the study reach Baetis density declined 70% during the 4.5 wk and per-capita losses averaged 3.8% d^-1. We estimated that predation by Kogotus could cause between 1.6 and 9.5% of the losses of Baetis from the study reach. This occurred because high losses of Baetis were combined with low consumption rates and densities (1.83 individuals m^-2) of Kogotus. Baetis drift density was higher at night than during the day. Drift densities of Baetis tended to be higher leaving than entering the reach in nighttime estimates, although the results were not statistically significant. Few replicates resulted in low power to detect differences in upstream and downstream drift densities; therefore, it is possible that some losses could be the result of drift out of the study reach. Nonetheless our results suggest that Kogotus populations had little direct, lethal effect on Baetis populations in this study reach."

Koch,BJ; Hall Jr,RO and Peckarsky,BL 2020 Nonconsumptive effects of Brook Trout predators reduce secondary production of mayfly prey. Freshwater Science, 39(3), pp.549-558.

Larson,EI; Poff,NL; Atkinson,CL and Flecker,AS 2018 Extreme flooding decreases stream consumer autochthony by increasing detrital resource availability. Freshwater Biology, 63(12), pp.1483-1497. PDF
     Quote: "All taxa showed variability in the proportion of their diet derived from autochthonous compared to allochthonous sources across streams (Supplementary Table 1). Generally, mean consumer autochthony ranged from around 0.25 to 0.5 proportionally of the diet. Certain taxa, such as the rhyacophilid caddisfly Rhyacophila angelita (mean of dietary proportion derived from the epilithon of 0.39-0.48 for their prey across streams), the simuliid blackfly Simulium sp. (0.24-0.31), the perlodid stonefly Megarcys signata (0.48-0.53) and nemourid stonefly Zapada sp. (0.51-0.53) varied little in their resource use across streams. In contrast, the baetid mayfly Baetis bicaudatis (0.22-0.52), the perlodid stonefly Kogotus modestus (0.28-0.61), and the ephemerellid mayflies Drunella doddsi (0.26-0.55), and Drunella grandis (0.25-0.42) exhibited more variability in their resource use across streams. Full stable isotope results and biplots are available in Supplemental Figures 1 and 2."

Lugo-Ortiz,CR and McCafferty,WP 1998 A new North American genus of Baetidae (Ephemeroptera) and key to Baetis complex genera. Entomological News 109 5, 345-353. Abstract
     The key splitting Baetis species from Labiobaetis, Barbaetis, Heterocloeon, Plauditus and Acentrella is useful. Page 351 has figures illustrating the Baetis traits of thumb on the labial palp (Fig 20) and figure 21 showing abdominal tergal scales.

McCafferty,WP; Durfee,RS; Kondratieff,BC 1993 Colorado mayflies (Ephemeroptera): an annotated inventory. Southwestern Naturalist 38 3, 252-274. PDF
     Quote from page 255: "This is a relatively common mountain species throughout the West. It sometimes is the only mayfly species found in alpine streams of Colorado. It is now known to range into Alaska (Milner, 1987), and the first author and N. Kluge of St. Petersburg, Russia have recently confirmed that it also occurs in Siberia. Another "two-tailed," trout-stream species of Baetis that may eventually be confirmed from Colorado is B. punctiventris (McDunnough), which has often been incorrectly known as Pseudocloeon edmundsi to Salmon River and Yellowstone fly fishermen."

McCafferty,WP and Provonsha, AV The Mayflies of North AmericaSpecies List (Version 8Feb2011)
     Here is the geographic range and synonyms:

Baetis bicaudatus Dodds, 1923 [CAN:FN,NW;USA:FN,NW,SW]
    Baetis minimus Dodds, 1923 (syn.)

McIntosh,AR; Peckarsky,BL and Taylor,BW 2002 The influence of predatory fish on mayfly drift: extrapolating from experiments to nature. Freshwater Biology 47: 1497-1513. PDF

McIntosh,AR; Peckarsky,BL and Taylor,BW 1999 Rapid size-specific changes in the drift of Baetis bicaudatus (Ephemeroptera) caused by alterations in fish odour concentration. Oecologia 118(2) 256-264. PDF

McPeek,MA and Peckarsky,BL 1998 Life histories and the strengths of species interactions: combining mortality, growth and fecundity effects. Ecology 79: 235-247. PDF
     Abstract: "Interactive effects of one species on another may simultaneously influence mortality, growth, and fecundity. To quantify the strength of an interaction between two species, we must therefore use techniques that integrate these various responses into estimates of overall effect. Demographic models of populations provide such a framework. Here we develop a demographic model describing the life history of a hemimetabolous insect to evaluate the relative importance of predator effects on mortality and growth of damselflies (Enallagma boreale) in fishless ponds and mayflies (Baetis bicaudatus) in trout streams.
Previous experiments have shown that dragonfly predators in fishless ponds inflict direct mortality and cause reduced growth rates in Enallagma damselflies. Parameterization of the demographic model from these data show, however, that only the direct mortality effects of dragonflies should significantly influence damselfly population dynamics. This is because damselfly size at emergence does not influence adult female fecundity, so the effects of dragonflies on damselfly larval growth do not influence adult fecundity. Likewise, both trout and stonefly predators inflict mortality on larval Baetis mayflies and cause decreases in growth rates. However, our demographic analyses indicate that the growth effects of both predators should dominate the population-dynamic effects on Baetis. This is because size at emergence translates directly into adult fecundity in mayflies. We also present data suggesting that developmental responses to changes in environmental conditions (e.g., predator abundances, resource availabilities) differ between species depending on these same life history parameters.
The biological significance of lethal vs. sublethal predator impacts must be evaluated in a demographic framework to identify whether alterations in growth rate, and the timing of and size at metamorphosis, significantly influence population dynamics. The demographic model used for any particular organism must be tailored to its life history, but the various impacts of interactions with other species can all be integrated into estimates of projected population growth that can then be readily compared among species with different life histories."

Mihuc,TB and Minshall, GW 1995 Trophic generalists vs. trophic specialists: implications for food web dynamics in post-fire streams. Ecology, 76(8), pp.2361-2372.
     Abstract: "The trophic ecology of 11 benthic macroinvertebrate taxa found in Cache Creek, Yellowstone National Park (YNP) was studied to determine if burned organic matter is an important resource and how resource utilization patterns may be altered in post-fire streams. Laboratory food quality experiments were conducted to determine the growth response of each species when grown on several resource types: burned organic matter, periphyton, unburned coarse particulate material (CPM), and unburned fine particulate material (FPM). The central hypothesis of this research was that benthic macroinvertebrates cannot use burned organic matter as a resource. A secondary hypothesis was that some benthic macroinvertebrates are facultative in trophic function, with the ability to use both allochthonous and autochthonous resources for growth. Of the 11 taxa studied, only one (Paraleptophlebia heteronea) could grow on burned organic matter as a resource, indicating that post-fire food webs probably do not exhibit major shifts in resource utilization to burned material. Two species were generalist detrivores (P. heteronea, Ameletus cooki) able to use both natural FPM and CPM resources. Two species were specialist detritivores (Oligophlebodes sigma, Ephemerella infrequens) growing only on unburned CPM resources, and two (Cinygmula mimus, Epeorus albertae) were specialist herbivores utilizing only periphyton. Five species were generalist herbivore-detritivores (Baetis bicaudatus, Drunella doddsi, D. coloradensis, D. spinifera, Zapada columbiana), exhibiting growth on both detritus and periphyton resources. Based on the experimental results, trophic generalists are common food web components in Yellowstone streams. Two of the most abundant benthic macroinvertebrates during post-fire recovery, B. bicaudatus and Z. columbiana, were trophic generalists, indicating that some generalists may be disturbance adapted. In this study, published functional feeding group classification did not indicate obligate resource utilization (growth on only one resource type) for most taxa studied. Comparison of a food web for Cache Creek based on functional feeding group classification and one based on the results of this study indicates that the inclusion of generalists in the web results in a more realistic approximation of food web relationships such as the link-species scaling law. Our results suggest that future research should include spatial and temporal aspects of resource switching and generalist resource utilization by individual lotic primary consumers."

Minshall,GW Robinson,CT and Lawrence,DE 1997 Postfire responses of lotic ecosystems in Yellowstone National Park, U. S. A. Canadian Journal Fisheries Aquatic Sciences 54: 2509-2525.
http://www.cnr.berkeley.edu/wfrg/main/lecture01/Minshall1.pdf

Newell,RL and Hossack,BR 2009 Large, wetland-associated mayflies (Ephemeroptera) of Glacier National Park, Montana. Western North American Naturalist, 69(3) 335-342. Abstract and PDF

Peckarsky,BL 1980 Influence of detritus on colonization of stream invertebrates. Canadian Journal of Fisheries and Aquatic Sciences 37, 957-963.

Peckarsky,BL 1983 Biotic interactions or abiotic limitations? A model of lotic community structure. In: Dynamics of Lotic Ecosystems. Eds: Fontaine III,Thomas D; Bartell,Steven M Ann Arbor Science, Ann Arbor, Michigan, 303-323.

Peckarsky,BL 1990 Habitat selection by stream-dwelling predatory stoneflies. Canadian Journal of Fisheries and Aquatic Sciences 48, 1069-1076.

Peckarsky,BL 1991a A field test of resource depression by predatory stonefly larvae. Oikos 61 (1) 3-10.

Peckarsky,BL 1991b Is there a coevolutionary arms race between predators and prey? A case study with stoneflies and mayflies. Advances in Ecology 1: 167-180.

Peckarsky,BL 1996 Alternative predator avoidance syndromes of stream-dwelling mayfly larvae. Ecology 77 (6) 1888-1905.Abstract

Peckarsky,BL; Cowan,CA; Penton,MA and Anderson,C 1993 Sublethal consequences of stream-dwelling predatory stoneflies on mayfly growth and fecundity. Ecology 74(6)1836-1846. Abstract

Peckarsky,BL; Encalada,AC and McIntosh,AR 2011 Why do vulnerable mayflies thrive in trout streams?. American Entomologist, 57(3), pp.152-164. PDF

Peckarsky,BL; Hughes,JM; Mather,PB; Hillyer,M; Encalada,AC 2005 Are populations of mayflies living in adjacent fish and fishless streams genetically differentiated? Freshwater Biology 50(1), 42-51. doi: 10.1111/j.1365-2427.2004.01292.x PDF
     Abstract: "1. Conspecific populations living in habitats with different risks of predation often show phenotypic variation in defensive traits. Traits of two species of mayflies (Baetidae: Baetis bicaudatus and Baetis sp. nov.) differ between populations living in fish and fishless streams in a high altitude drainage basin in western Colorado, U.S.A. We tested for genetic differentiation between mayfly populations in these two habitat types, assuming that lack of genetic differentiation would be consistent with the hypothesis that those traits are phenotypically plastic.
2. Previous work has shown that larvae of both species behave differently and undergo different developmental pathways in adjacent fish and fishless streams. These phenotypic differences in behaviour and development have been induced experimentally, suggesting that populations from fishless streams have the genetic capability to respond to fish.
3. During summer 2001 we collected Baetis larvae from several fish and fishless streams, and from fish and fishless sections of the same streams. We used allozymes and a fragment of the cytochrome oxidase subunit 1 mitochondrial gene to examine genetic variation of Baetis individuals within and among streams.
4. Results showed that genetic variation exists among populations of the same species of Baetis from different streams, but none of that variation was associated with the presence or absence of fish. These data confirm that populations of Baetis living in fish and fishless streams are not genetically distinct, and are consistent with the hypothesis that traits associated with environments of different risk are phenotypically plastic."

Peckarsky,BL; Kerans,B; Taylor,BW and McIntosh,AR. 2008 Predator effects on prey population dynamics in open systems. Oecologia 156(2):431-40. Abstract, PDF
     Abstract: "Animal population dynamics in open systems are affected not only by agents of mortality and the influence of species interactions on behavior and life histories, but also by dispersal and recruitment. We used an extensive data set to compare natural loss rates of two mayfly species that co-occur in high-elevation streams varying in predation risk, and experience different abiotic conditions during larval development. Our goals were to generate hypotheses relating predation to variation in prey population dynamics and to evaluate alternative mechanisms to explain such variation. While neither loss rates nor abundance of the species that develops during snowmelt (Baetis bicaudatus) varied systematically with fish, loss rates of the species that develops during baseflow (Baetis B) were higher in streams containing brook trout than streams without fish; and surprisingly, larvae of this species were most abundant in trout streams. This counter-intuitive pattern could not be explained by a trophic cascade, because densities of intermediate predators (stoneflies) did not differ between fish and fishless streams and predation by trout on stoneflies was negligible. A statistical model estimated that higher recruitment and accelerated development enables Baetis B to maintain larger populations in trout streams despite higher mortality from predation. Experimental estimates suggested that predation by trout potentially accounts for natural losses of Baetis B, but not Baetis bicaudatus. Predation by stoneflies on Baetis is negligible in fish streams, but could make an important contribution to observed losses of both species in fishless streams. Non-predatory sources of loss were higher for B. bicaudatus in trout streams, and for Baetis B in fishless streams. We conclude that predation alone cannot explain variation in population dynamics of either species; and the relative importance of predation is species- and environment-specific compared to non-predatory losses, such as other agents of mortality and non-consumptive effects of predators."

Peckarsky,BL; McIntosh,AR; Taylor,BW; Dahl,J 2002 Predator chemicals induce changes in mayfly life history traits: A whole stream manipulation. Ecology 83 (3) 612-618. PDF
     Abstract: " In high-elevation streams of western Colorado, mayflies (Baetis bicaudatus) develop faster, but mature at a smaller size where trout are present compared to streams where fish are absent. These life history traits reduce the time of larval exposure to trout predation, but cost reduced fecundity. We designed a field experiment involving manipulation of whole streams to determine whether these changes were caused by the presence of brook trout, and specifically, whether they could be triggered by trout chemical cues. In 1999 and 2000, we introduced water from containers with brook trout (Salvelinus fontinalis) into five naturally fishless streams, and fishless stream water into five adjacent control streams, to determine whether these cues alone could induce the mayfly life history traits we have observed in natural trout streams. As in previous small-scale experiments, the size at which mayflies matured declined significantly in streams with added trout chemicals but did not change in streams with fishless water only. Thus, life history traits similar to those observed in the field were induced within the natural variability inherent in streams. These results demonstrate the strength of this predator-prey interaction and indicate that brook trout are an important agent of natural selection on mayfly life history traits."

Peckarsky,BL; McIntosh,AR; Caudill,CC; Dahl,J 2002 Swarming and mating behavior of a mayfly Baetis bicaudatus suggest stabilizing selection for male body size. Behavioral Ecology and Sociobiology 51, 530-537.

Peckarsky,BL; McIntosh,AR; Caudill,CC and Dahl,J 2002 Stabilizing selection on male body size of high altitude populations of Baetis bicaudatus (Ephemeroptera: Baetidae). Behavioral Ecology and Sociobiology 51:530-537. Abstract

Peckarsky,BL; McIntosh,AR; Àlvarez,M and Moslemi,JM 2013 Nutrient limitation controls the strength of behavioral trophic cascades in high elevation streams. Ecosphere, 4(9)1-17. PDF
     Abstract: "Indirect effects of predators on primary producers vary over space and time. Key components of the environmental context underlying that variability include the bottom-up supply of resources and the defense, mobility and foraging efficiency of primary consumers. We manipulated key resources that limit primary producers and tested the effects of system enrichment on the strength of top-down interactions between top predators (Salvelinus fontinalis), different types of grazing invertebrates and algae in high elevation streams of Colorado, USA. We added nitrogen and phosphorus to flow-through microcosms powered by stream water and tested the direct effects of chemical cues from brook trout on the behavior of sedentary, predator-resistant (caddisflies) and mobile, predator-vulnerable grazers (mayflies), and the indirect cascading effects of predators on: (1) the biomass of algae mediated by grazer behavior and (2) the impact of grazers on algal biomass accrual. Recognizing the value of whole-ecosystem experiments, we also tested the effects of supplementing nutrients to two headwater fishless streams on the impact of grazers on algae and the performance (growth rates) of four predominant grazer species compared to two adjacent reference streams with ambient (limited) nutrients. In both experiments, algal biomass increased with added nutrients where consumption by grazers was swamped by increased algal accrual due to enrichment. Results of the microcosm experiment were consistent with a context-dependent behavioral trophic cascade whereby predator cues increased the biomass of algae only in treatments with enriched nutrients and mobile, predator-vulnerable grazers (Baetis mayflies). Baetis showed risk-sensitive behavioral responses to fish cues, which resulted in cascading effects on algae only under enrichment. In contrast,behavior of sedentary, predator- resistant caddisflies (Allomyia) was unaffected by predator cues and a cascade was never observed. The whole ecosystem experiment revealed no aggregative responses by grazers but instead, strong developmental responses of all grazer species to nutrient enrichment. Growth rates of grazers increased with mobility, with the highest rates occurring for mobile, predator-vulnerable Baetis mayflies in enriched streams. Our results emphasize the importance of experimentally testing thecontext-dependency of trophic cascades, and are consistent with the hypothesis that nutrient limitation may reduce the strength of trophic cascades."

Poff,NL; Wellnitz,TA and Monroe,JB 2003 Redundancy among three herbivorous insects across an experimental current velocity gradient. Oecologia 134:262-269. PDF
     Abstract: "We conducted streamside experiments to determine if the ability of herbivorous insects to remove algal periphyton varies with local current velocity. We used two mayfly species (Baetis bicaudatus and Drunella grandis) and one caddisfly species (Glossosoma verdona), which differ from one another in body morphology and mobility. Periphyton was grown for 30 days on ceramic tiles in constant velocity to create similar initial forage conditions for grazers. Tiles were transferred to three velocity regimes characteristic of the natural streambed: slow (3-5 cm s-1), medium (15-20 cm s-1) and fast (32-41 cm s-1). Four grazer treatments (Baetis, Drunella, and Glossosoma alone, and all species combined) were repeated for each velocity treatment to isolate the effect of local current on grazer ability to crop periphyton. Grazers differed in their abilities to remove periphyton across current treatments. Glossosoma removed significantly (P<0.05) more periphyton at fast versus either slow or medium velocities; Baetis showed a similar (but non-significant) trend; and, Drunella always removed about 75% of periphyton, irrespective of current. At fast current, periphyton removal was equivalent among the species. At medium current, Drunella removed significantly more than both Baetis and Glossosoma, whereas at slow current, Drunella removed more than Baetis, which removed more than Glossosoma. Periphyton removal under the combined three-grazer treatment was similar qualitatively to the combined effects of individual grazers. More periphyton tended to be removed as current increased, with the fast versus slow contrast showing marginal significance (P=0.10). Under all current regimes, the quantity of periphyton removed did not differ from the null model expectation of simple additive effects among individual grazers (i.e., no facilitation or inhibition). These experiments show that for some species, herbivory varies with current, which suggests that the herbivore "function" of cropping periphyton may vary with the environmental context of local current. Under some local velocities, however, different herbivore species "function" similarly and are potentially redundant with respect to periphytic removal. In naturally heterogeneous streams characterized by sharp gradients in local current velocity, we expect current-dependent species interactions to be common and at least partially contribute to intra-guild co-existence of species."

Richards,C and Minshall,GW 1988. The influence of periphyton abundance on Baetis bicaudatus distribution and colonization in a small stream. Journal of the North American Benthological Society 7(2):77-86.

Stewart,KW and Szczytko,SW 1983 Drift of Ephemeroptera and Plecoptera in two Colorado rivers. Freshwater Invertebrate Biology. 2(3)117-131. PDF

The United States Geological Survey (USGS) National Water Quality Assessment Data Warehouse (NAWQA) shows this species is present in Gunnison County. Data as of 1Sep2005

Vance,SA and Peckarsky,BL 1996 The infection of nymphal Baetis bicaudatus by the mermithid nematode Gasteromermis sp. Ecological Entomology 21: 377-381.

Vance,SA 1996 The effect of the mermithid parasite Gasteromermis sp. (Nematoda: Mermithidae) on the drift behaviour of its mayfly host, Baetis bicaudatus (Ephemeroptera: Baetidae): a tradeoff between avoiding predators and locating food. Canadian Journal of Zoology 74: 1907-1913.

Vance,SA and Peckarsky,BL 1997 The effect of mermithid parasitism on predation of nymphal Baetis bicaudatus (Ephemeroptera) by invertebrates. Oecologia 110: 147-152.
     They found that Kogotus modestus ate significantly more parasitized than unparasitized B. bicaudatus. However, Rhyacophila hyalinata caught and ate equal numbers of parasitized and unparasitized nymphs. They attribute this to the behavior of parasitized nymphs and different hunting behaviors of the predators. Parasitized nymphs drifted less, which increased encounter rates with Kogotus nymphs. However R. hyalinata larvae are ambush predators and catch parasitized and unparasitized nymphs equally. They hypothesize that avoiding fish predation by drifting less is a greater advantage to the parasite than the losses suffered by increased stonefly predation.

Vance,SA 1996 Morphological and behavioural sex reversal in mermithid-infected mayflies. Proceedings of the Royal Society of London B 263: 907-912.
     She studied Baetis bicaudatus from the East River near Gothic. B. bicaudatus were either unparasitized with a normal morphology or parasitized with a "female" or intersex morphology. No parasitized mayflies showed complete male characteristics. Through the use of flow cytometry she discovered the "female" mayflies were probably about half males who had suffered sex reversal as a result of Gasteromermis parasitism. Parasitized individuals also tended to fly upstream and were observed crawling under the water, all of which are female behaviors that allow the nematode to emerge from the mayfly and burrow into the substrate to complete its life cycle.

Wellnitz,T 2014 Can current velocity mediate trophic cascades in a mountain stream?. Freshwater Biology, 59(11) 2245-2255. PDF

Wilcox,AC; Peckarsky,BL; Taylor,BW; and Encalada,AC 2008 Hydraulic and geomorphic effects on mayfly drift in high-gradient streams at moderate discharges. Ecohydrology 1(2) 176-186.
     Abstract: "We investigated relationships between geomorphic and hydraulic factors and invertebrate drift in high-gradient streams. We measured drift density of a highly mobile mayfly (Baetis bicaudatus) into and out of 12 stream reaches in western Colorado, as well as benthic density and abiotic variables within those reaches, during a time of moderate discharge. Multiple regression analysis indicated that drift propensity (drift density/benthic density), a measure of drift standardized by the benthic density of the source population, was significantly related to Reynolds number, a dimensionless ratio of fluid inertial forces to viscous forces, and Shields number, a dimensionless ratio of shear stress to submerged particle weight that quantifies flow competence. Drift propensity was positively correlated with Reynolds number, but counter to our hypothesis that stronger hydraulic forces would be associated with higher drift, mayflies in reaches with greater flow competence (Shields number) showed lower propensities to drift. Further, immigration ratio (drift in/drift out of each reach) increased significantly with Shields number, indicating that more individuals drifted into than out of reaches with higher flow competence. Although we hypothesized that more hydraulically rough stream reaches (i.e. those with greater flow resistance) would be more favourable to benthic invertebrates and would thus have lower drift, neither drift propensity nor immigration ratio were related to flow resistance. In high-gradient streams at discharges below the range of incipient motion of bed particles, mayfly drift behaviour may be influenced by hydraulic forces, but the relationships we observed are not indicative of passive, abiotically driven drift."

Zuellig,RE; Kashian,DR; Brooks,ML; Kiffney,PM and Clements,WH 2008 The influence of metal exposure history and ultraviolet-B radiation on benthic communities in Colorado Rocky Mountain streams. Journal of the North American Benthological Society, 27(1), 120-134. PDF

Illustrations

The middle tail is only a stub or apparently missing. Consider that nymphs of other species may look like B. bicaudatus initially, but will gain tail segments with each new instar.

Brown, WS 2004 Mayflies (Ephemeroptera) of Gunnison County, Colorado, USA
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