David C. Houghton

Biological changes along the continuum of an agricultural stream: influence of a small terrestrial preserve and use of adult caddisflies in biomonitoring

We monitored benthic macroinvertebrates and adult caddisflies along an agricultural stream continuum upstream, within, and downstream of a small forested preserve. The habitat upstream of all sites was >60% disturbed by agricultural activities. The percentage of riparian disturbance was markedly lower adjacent to the sites inside the preserve than those outside. Water physicochemical factors did not exhibit clear changes among sites, except for nitrate concentration, which was highest upstream of the preserve. Biological diversity of adult caddisflies was significantly higher within the preserve. Biological diversity of benthic invertebrates exhibited similar results except for non-significance between the upstream and preserve sites. Pollution tolerance and percentage of filtering collector metrics were unchanged among sites for both assemblages. The percentage of adult caddisflies in the shredder functional group increased significantly within the preserve but remained small relative to that of pollution-tolerant filtering collectors. The small terrestrial preserve promoted a three-fold increase in species diversity, even without corresponding changes in water quality or trophic structure. Such an increase, however, may not be as detectable with traditional benthic biomonitoring techniques due to the difficulties of sampling benthic microhabitats representatively and identifying specimens to the species level.

Biological diversity of the Minnesota caddisflies (Insecta, Trichoptera)

Abstract The caddisfly fauna of Minnesota contains at least 277 species within 21 families and 75 genera. These species are based on examination of 312,884 specimens from 2,166 collections of 937 Minnesota aquatic habitats from 1890 to 2007. Included in these totals is my own quantitative sampling of 4 representative habitat types: small streams, medium rivers, large rivers, and lakes, from each of the 58 major Minnesota watersheds from June through September during 1999–2001. All species are illustrated herein, and their known Minnesota abundances, distributions, adult flight periodicities, and habitat affinities presented. Four species: Lepidostoma griseum (Lepidostomatidae), Psilotreta indecisa (Odontoceridae), and Phryganea sayi and Ptilostomis angustipennis (Phryganeidae) are added to the known fauna. An additional 31 dubious species records are removed for various reasons. Of the 5 determined caddisfly regions of the state, species richness per watershed was highest in the Lake Superior and Northern Regions, intermediate in the Southeastern, and lowest in the Northwestern and Southern. Of the 48 individual collections that yielded >40 species, all but 1 were from the Northern Region. Many species, especially within the families Limnephilidae and Phryganeidae, have appeared to decrease in distribution and abundance during the past 75 years, particularly those once common within the Northwestern and Southern Regions. Many species now appear regionally extirpated, and a few have disappeared from the entire state. The loss of species in the Northwestern and Southern Regions, and probably elsewhere, is almost certainly related to the conversion of many habitats to large-scale agriculture during the mid-20th century.

Nocturnal flight periodicity of the caddisflies (Insecta: Trichoptera) in a large Michigan river

Over 18,000 caddisfly specimens representing 44 species were collected from sunset until sunrise on each of 6 days during July 2010 from a large river in northern Lower Michigan. Sampling occurred every 15 minutes from sunset until midnight and every hour afterward until sunrise. Mean specimen abundance peaked at 22:30, approximately 1 hour after sunset, before decreasing precipitously. Species richness peaked from 22:30 to 23:00 and decreased more gradually. All species and >95% of specimens were caught before midnight. Both overall specimen abundance and species richness correlated positively with dew point, reflecting relatively constant temperatures throughout the sampling period. Likewise, temperature correlated positively with specimen abundance at each sampling period from 23:00 to 00:00 and at 02:00. Of the 18 most abundant species, 10 had peak abundance between 22:30 and 22:45, 7 had extended peak abundance from 22:30 to 23:00 to 02:00, and 1 peaked after 22:30. Specimen abundance of all trophic functional groups peaked from 22:30 to 22:45, except for scrapers, which remained abundant until 23:30. Our results suggest that 1–2 hours after sunset is the optimal time for sampling adult caddisflies, but sampling until 2–3 hours after sunset is necessary to collect all species. Stopping a sample when specimen abundance starts to decrease may miss peak species richness. Ambient temperature must also be taken into consideration.

Seasonal Changes in the Critical Thermal Maxima of Four Species of Aquatic Insects (Ephemeroptera, Trichoptera)

ABSTRACT Seasonal changes in the critical thermal maxima (CTmax) of four species of aquatic insects were determined from February 2012 to February 2013 from a first-order stream in northern Lower Michigan. Three of these species: Stenonema femoratum (Ephemeroptera: Heptageniidae), Hydropsyche slossonae (Trichoptera: Hydropsychidae), and Dolophilodes distinctus (Trichoptera: Philopotamidae) exhibited seasonal changes in CTmax, increasing through the spring and summer and then decreasing into the subsequent fall and winter. CTmax of these species correlated strongly with both the seasonal ambient stream temperature and with a series of different laboratory acclimation temperatures, suggesting that organisms adapt to laboratory acclimation in a similar manner as they adapt to seasonal changes. In contrast, the CTmax of Parapsyche apicalis (Trichoptera: Arctopsychidae) remained constant regardless of ambient or acclimation temperature. All species exhibited greater thermal sensitivity relative to ambient temperature during the summer than the winter. Our study indicates that thermal tolerance patterns can be different among species in the same environment. It also provides the first winter and year-round thermal tolerance data for aquatic insects.

Abrupt biological discontinuity in a small Michigan (USA) stream due to historical riparian canopy loss

We assessed physicochemical and biological continuity in an 800-m reach of a small (<2 m wide) headwater stream during 2010 and 2012 in the northcentral U.S. Dense riparian canopy covered the first 600 m of stream reach, was lacking in an approximately 100-m portion due to historical (>10 years previously) agriculture, and returned in the last 100 m of the study area. Reflecting this difference, the forested area had less sunlight penetration to the water level and greater volume of woody debris in the stream. There was no difference in specific conductance or pH among sites. Water temperature was lower in the upstream forested sites and higher in the non-forested site and those downstream of it. Dissolved oxygen exhibited a reciprocal trend with temperature. The non-forested site exhibited an abrupt change in biological continuity as indicated by a decrease in benthic macroinvertebrate and adult caddisfly shredder abundance, an increase in filtering collector and scraper abundance, a decrease in trout abundance, and an increase in both total and warm-water fish species. The stream returned to its previous state when canopy returned downstream. Both years of the study yielded similar results. Our results indicate that abrupt changes in riparian canopy can lead to similarly abrupt changes in biological continuity, often within a relatively short (100 m) distance.

Delineation and characterization of Michigan, USA, caddisfly (Insecta: Trichoptera) biodiversity and comparison with Minnesota

Based on canonical correspondence analysis (CCA) ordination of the relative caddisfly abundance of 79 streams (5–15 m in width), the state of Michigan appears to be composed of three distinct regions of caddisfly biological diversity corresponding to the Upper Peninsula, northern Lower Peninsula, and southern Lower Peninsula. The analysis further determined latitude, watershed gradient, and anthropogenic disturbance as important variables influencing distributional patterns. Overall species richness was higher and trophic functional group composition was as predicted by the river continuum concept in the predominately forested Upper Peninsula and northern Lower Peninsula regions. The northern Lower Peninsula region in particular was dominated by shredders. Overall species richness was lower in the agricultural southern Lower Peninsula region, and streams were dominated (>75% of specimens) by filtering collectors. Similar patterns of biological diversity and important environmental variables were determined when combining the Michigan streams with 87 similar streams from throughout Minnesota into a larger CCA ordination. Overall, five regions of caddisfly biological diversity are now established in the two states: northern Great Lakes, northern forested, southern agricultural, southeastern Minnesota, and northwestern Minnesota.

A 5-Year Study of the Adult Flight Periodicity of 27 Caddisfly (Trichoptera) Species in Forest and Meadow Habitats of a First-Order Lower Michigan (USA) Stream.

ABSTRACT Life cycles of 27 caddisfly species were estimated from weekly adult flight periodicity data during 2010–2014 from a forest and a meadow site of a small stream in northern Lower Michigan. Of the 11 species abundant only at the forest site, 10 appeared to be univoltine and 1 appeared bivoltine. Of the 13 species abundant only at the meadow site, 5 appeared univoltine, 5 appeared bivoltine, and 3 were enigmatic due to inconsistent flight peaks between years. Although the sites were separated by ∼400 m, only three species were abundant at both sites due to differences in stream habitat and food availability. Two of these species had notably dissimilar life cycles between sites, reflecting these differences. Despite the study dates encompassing both the warmest and coldest years of the 2000s, most species retained consistent flight periods between years. This consistency with date appeared unrelated to lunar phase. Date was a better predictor of flight periodicity than water temperature for every species except those that emerged earliest in the season. Warming water temperatures appeared to synchronize emergence of species at the meadow site to a greater degree than those of the forest site, probably due to the greater range of temperatures at the meadow site, although date was still the better predictor at both sites. These data suggest that warming water temperatures, although important under certain conditions, may not always be primary life cycle synchronizers in small streams.

Updated checklist of the Michigan (USA) caddisflies, with regional and habitat affinities

Abstract Based on examination of ~180,000 specimens from 695 collections of 443 localities collected from the 1930s to 2015 we report 295 species of caddisflies from Michigan. Of these, 41 are reported from the state for the first time. Another 18 species previously reported from Michigan are listed as doubtful. The 11 most abundant species collectively represented over half of all specimens collected. Conversely, 80 species were known from <10 specimens, and 27 species from a single specimen. The Michigan fauna is similar to those of Minnesota and Ohio, adjacent states with comparable recent collecting effort. Regional and habitat affinities for each Michigan species are reported herein. Due to the high level of species discovery over the last few years, despite a >80-year collecting history, it is likely that additional species remain undiscovered in the state.

Serial discontinuity in naturally alternating forest and floodplain habitats of a Michigan (USA) stream based on physicochemistry, benthic metabolism, and organismal assemblages

ABSTRACT We tested the response of several different water quality metrics at 6 sites along a 4-km alternating forest (canopied) and floodplain (non-canopied) reach of the East Branch of the Black River, an undisturbed northern Lower Michigan trout stream, during summer 2015. Physicochemical parameters were unchanged between sites and reflected an undisturbed continuum. In-stream woody debris was higher at the forest sites, whereas relative canopy cover and sunlight intensity were higher at the floodplain sites. Both benthic macroinvertebrates and adult caddisflies exhibited greater species richness and a higher abundance of shredders at the forest sites, and a higher abundance of scrapers at the floodplain sites. Fish specimen abundance, species richness, and percentage of trout were not different between sites, and instead all increased throughout the summer. Community respiration was unchanged between the single tested floodplain site and the forest sites upstream and downstream of it. Gross primary production and net daily metabolism were higher at the floodplain site, leading to stream autotrophy. This result was also obtained when tested in summer 2017. Our results support the idea that terrestrial habitat changes can singularly affect the fundamental ecological functioning of an undisturbed stream, primarily due to deviations in sunlight penetration and allochthonous input. Moreover, the short distances between sites with alternating results indicate the dynamic and serially discontinuous state of natural rivers.

When to sample adult caddisflies: data from a five-year study of a first-order Michigan (USA) stream

ABSTRACT Nearly 20,000 adult caddisfly specimens were collected during May through September 2010–2014 from approximately weekly ultraviolet light samples of Fairbanks Creek in northern Lower Michigan. Detrended correspondence analysis determined four distinct seasonal assemblages corresponding to spring (May to late June), summer (late June to late July), late summer (late July to early September), and autumn (early to late September). Of the 109 total species caught, 5 indicated the spring assemblage, 13 the summer assemblage, 1 the late summer assemblage, and 4 the autumn assemblage. Species richness, specimen abundance, and number of unique species were highest during the summer. Most summer samples contained ∼50% of all species caught during the year; whereas the spring and autumn assemblage contained a smaller but unique fauna, and the late summer assemblage was characterized by a decreasing richness of summer species. Pollution tolerance and shredder to filtering collector ratio metrics varied by factors of 5–30x; both were highly dependent on the abundance of particular species. Overall mean values of all metrics varied seasonally but not annually. The specific date of peak species richness varied based on annual weather, but occurred at a similar degree-day value for all 5 years. These results suggest the importance of sampling within a season when comparing streams for biological monitoring purposes. Moreover, they confirm the comparability of samples taken from different years, provided such samples are collected during the same season.