There are serious concerns for native freshwater mussel survival (Bivalvia: Unionidae) in the Laurentian Great Lakes region after populations were seemingly pushed to the brink of extirpation following the introduction of dreissenid mussels (Dreissena polymorpha and D. rostriformis bugensis) in the mid-1980s. The Detroit River was the first major river system in North America to be invaded by dreissenids, and unionids were considered extirpated from the river by 1998. Since then several unionid refuges (areas with relatively low dreissenid impact and surviving unionids) have been found in coastal areas of lakes St. Clair and Erie, but no documentation exists in the Detroit River. To assess dreissenid presence and potential unionid persistence, a mixture of stratified random, historical, and potential refuge sites were surveyed during summer 2019 in the Detroit River. Unionid and dreissenid habitat use was further investigated with analysis of variance and classification tree analyses. Of the 56 sites surveyed, only five sites had live unionids totaling 220 animals of 11 species. More than 2000 unionid shells of 31 species were collected from 39 sites, confirming the large and diverse unionid populations that existed prior to the dreissenid invasion. Ninety-eight percent of live unionids found showed evidence of past or present dreissenid attachment. Estimated dreissenid densities were highly variable with river location and ranged from 0 to 5673 live individuals per m², with the largest densities concentrated in the upstream half of the Detroit River. Despite their previously assumed extirpation from the Detroit River, live unionids were found during this comprehensive survey. Although only 40% of the historical species within the unionid assemblage remains, our results suggest, in the right conditions, some coexistence is possible among some species of unionids and dreissenids in this large river system.

Mozingo Lake, a reservoir in the mid-continental United States, was sampled 63 times between January 1999 and October 2015. Prior to 2005, phytoplankton biovolume was largely composed of Cryptomonas and cyanobacteria (mostly Aphanizomenon); these taxa correlated with the abundance of Daphnia and juvenile copepods, and were also influenced by competition between cyanobacteria and bacillariophytes. These relationships suggest the zooplankton community was primarily controlled by bottom-up processes during this time. In 2005, gizzard shad (Dorosoma cepedianum) first appeared in the lake, coinciding with the first spined and helmeted forms of Daphnia as well as their decline from 39% to 3% of zooplankton; the relative abundance of juvenile copepods increased concurrently. By 2007 phytoplankton biovolume had decreased by 88%. Although all phytoplankton phyla declined in absolute abundance, some were more heavily impacted. The relative abundance of Aphanizomenon declined from 50% to 6% of the phytoplankton biovolume; Cryptomonas remained common, but bacillariophytes became codominant. Despite the steep decline in phytoplankton biovolume, several important trophic interactions did not change: phytoplankton biovolume continued to control juvenile copepods, and competition continued between cyanobacteria and bacillariophytes. Although juvenile copepods continued to compete with Daphnia, the scarcity of the latter allowed a relative expansion of juvenile copepods and bacillariophytes. Because very few of the standard parameters correlated with phytoplankton, it seems likely that most of the changes were caused by the introduction of gizzard shad, which is an intense consumer of cyanobacteria and Daphnia. Gizzard shad likely initiated a trophic cascade both directly (through consumption) and indirectly (by shifting competition). Although other factors may have played a role, it seems clear that the introduction of gizzard shad can cause dramatic changes in both the zooplankton and phytoplankton communities by altering species relationships in top-down, bottom-up, as well as lateral control processes.

The effects of many pesticides on aquatic ecosystems remain poorly understood, especially in naturalistic communities in which organisms are connected by a complex array of direct and indirect interactions. Moreover, multiple stressors can interact, and the addition of apex predators, such as fish, may introduce additional ecosystem changes that exacerbate or mitigate pesticide effects. Despite being both common and environmentally persistent, the effects of the herbicide metolachlor on realistic aquatic communities have received insufficient research attention. We tested the effects of metolachlor on pond mesocosms at three concentrations (0, 20, and 80 ppb), along with the presence vs. absence of fish (black crappie, Pomoxis nigromaculatus) to determine the independent and combined effects of these two environmental changes. We found both metolachlor and fish altered the pond mesocosms, but their effects did not interact. Metolachlor reduced phytoplankton as expected, but had nonlinear effects on dissolved oxygen. Metolachlor also altered tadpole behavior, making them less prone to hiding. Fish presence increased periphyton and decreased snail counts, as well as changing the behavior of tadpoles, reducing their hiding behavior. This work demonstrates previously undocumented effects of metolachlor in the presence and absence of fish and suggests future avenues of investigation.

The ornate box turtle (Terrapene ornata) is a terrestrial Emydid, listed as near threatened by the International Union for Conservation of Nature Redlist due to habitat destruction, degradation, habitat fragmentation, commercial harvest, and road mortality. Terrapene ornata is secretive, which can pose a challenge to conducting systematic surveys and assessing species status. Studies on the species' biology have relied on opportunistic encounters on the road and the use of radiotelemetry. The objective of this study was to assess the feasibility of using transect line surveys in single season occupancy surveys for T. ornata in Roosevelt County, New Mexico. We further used radiotelemetry to link turtle activity patterns with environmental conditions to aid in understanding detectability of the species. Our occupancy model showed the detection probability to be influenced by individual observers and the time of day. We found T. ornata to most likely occupy habitats with less dense ground cover and avoid highly altered habitats (i.e., cultivated fields). Radiotelemetry further revealed the effect humidity, time of day, and temperature on turtle activity patterns. The lowest activity occurred between 1200–1700 h, whereas peak activity occurred in early morning hours (0600–0900 h). The peak activity occurred between ∼10–25 C and was promoted by higher humidity. Our study represents the first attempt at using transect line surveys for occupancy modeling framework for the ornate box turtles. We suggest that future studies on box turtle occupancy focus on finer scale habitat assessment that would also include vegetation, invertebrate, and small mammal surveys.

Precocial young leave their nest immediately after hatch to move and forage as a group during a rapid period of development. Growth and body condition are correlated with survival; young are better able to thermoregulate as they become larger, and they are better able to escape predators as they become more mobile. Environmental conditions can influence development and ultimately survival. We evaluated weather, cover type, and temporal factors affecting northern bobwhite juvenile body condition. We captured 216 individuals from 33 broods >16 d old on five conservation areas in southwest Missouri in 2017 and 2018. Brood hatch dates ranged from 26 May through 19 September. Body condition was measured as the residuals from a linear regression of juvenile tarsus length and body mass on capture. We found some support for improved body condition earlier in the breeding season and in native grasslands that were burned and grazed within the previous 2 y. However, models representing these effects had similar support to the null model (i.e., ΔWAIC<2), indicating weak support. Limited support for these effects may have been due to limited data or the influence of other environmental factors not considered in our competing model set. Our top model supported negative effects of later hatching date and agricultural crop cover on juvenile body condition. The early breeding season is an important period for successful bobwhite productivity, and native grasslands managed with rotational fire and grazing may create higher quality brood rearing habitat for improved juvenile body condition.

Grassland bird responses to grazing and prescribed fire are species-specific and are primarily known from systems with cattle as the predominant grazer. There is less knowledge of how grazing by bison impacts grassland birds, especially in sites restored and reconstructed from row-crop agriculture. Working at a tallgrass prairie site consisting of restored and remnant prairie in the years following bison reintroduction and ongoing prescribed burning, we assessed overall species richness and the relative detection frequency of five focal species (Grasshopper Sparrow, Henslow's Sparrow, Dickcissel, Eastern Meadowlark, and Brown-headed Cowbird). We used stationary bioacoustics recorders to record the soundscape during the summer breeding season in areas with and without bison from 2016 to 2018. Species richness and the detection frequencies of our focal species were not influenced by bison disturbance. Grasshopper Sparrow and Dickcissel detection frequency increased slightly in response to prescribed fire, whereas Henslow's Sparrow detection frequency decreased. Time since sites were restored was a predominant factor that influenced the variation in detection frequency of Henslow's Sparrows and Eastern Meadowlarks, likely due to vegetation differences in restored versus remnant sites and each species' vegetation structure preferences. Brown-headed Cowbird detection frequency was unaffected by bison presence, prescribed fire, or time since restoration, but varied among sampling years. Our focal species showed no response to bison disturbance 4 y after the bison reintroduction. This suggests there could be a time-lag for a response or that these species will not respond to the bison reintroduction at this study site.

Northern Mockingbirds (Mimus polyglottus) were studied between 1995 and 2015 on a university campus in New Orleans, U.S.A., spanning the 2005 landfall of Hurricane Katrina. The storm subjected the city to high winds and a prolonged flood. Nesting success showed a spike for 3 y after the storm, after which it gradually sank back to near pre-storm levels. Number of broods detected jumped from the first to the second year after the storm on campus and at two nearby residential sites. Success of males in acquiring mates improved from the first nesting season after the storm to the second across the three sites. Results draw attention to the importance of considering top-down effects in analyzing the recovery of storm-impacted birds.

This case study seeks to fill a critical knowledge gap regarding how natural wind disturbance affects stand and seedling bank diversity in mixed northern hardwood forests managed by single tree selection harvest methods. Contemporary timber harvests on state managed lands in Michigan's Upper Peninsula employ single tree selection cutting methods to promote more complex age structure in second growth stands dominated by sugar maple (Acer saccharum). However, concern exists that single tree selection harvest may result in lowered compositional diversity of seedlings as the low light conditions of small dispersed gaps exclude less shade tolerant species from gap regeneration. In July 2016 severe thunderstorms with winds in excess of 145 km/h (90 mph) caused extensive tree fall and canopy gap creation in second growth mixed northern hardwood forests in the southern Keweenaw Peninsula. We measured the species composition of overstory tree mortality and understory seedling regeneration in 14 storm gaps created in stands with and without previous single tree selection harvest. Storm gaps ranged in size from 125 to 1100 m². American basswood (Tilia americana) was disproportionately wind-thrown. Robust seedling regeneration was released in all storm gaps, with sugar maple comprising more than 75% of mean seedling abundance, regardless of previous single tree selection harvest. Sugar maple and ironwood (Ostrya virginiana) comprised 80% of sapling abundance. Results indicate single tree selection of mixed northern hardwood stands does not exacerbate, but rather emulates, dense sugar maple regeneration found on unmanaged second growth sites.

The purpose of this project was to isolate and describe the behaviors of individuals of two ant species, Aphaenogaster carolinensis Wheeler and Nylanderia faisonensis Forel, during their interference interactions, and to relate those to effects on colonies and their access to resources. Videos were taken of baited index cards from within the shared habitat of the ant species in northeast Georgia forests. Two measures of individual behavior, change in speed and deflection, and three measures of colony behavior, time to first ant, recruitment time and maximum number of individuals, were collected from video. Nest occurrence for each species within a specified distance of baits was determined for both species as well. Nylanderia faisonensis saw greater change in speed and deflection angle in response to species interactions than A. carolinensis. Locations with N. faisonensis nests had a higher maximum number of individuals of both species. Nylanderia faisonensis had longer recruitment times at locations with A. carolinensis nests. Although N. faisonensis was always the aggressor, they experienced clear negative consequences of their interactions.

An inverse density-dependent relationship between abundance and adult sex ratio (ASR, males:female) occurs in some populations of polygynous mammals due to life history differences between the sexes. Male fecundity and survival is dictated by attempts to obtain as many copulations as possible, whereas female fecundity and survival is dictated by resource acquisition. Therefore, females usually acquire forage before males as a result of interspecific scramble competition, particularly when forage becomes more limited at K carrying capacity. This leads to the passive displacement of males in a given area. The common belief is that most monogamous mammal populations exhibit balanced adult sex ratios. The coupling of sexually mature males and females in a population result in this pattern for this mating system. Present literature focuses on primary or secondary sex ratios in mammals or on ASR patterns within individual species. Our goal was to test if expected ASR patterns would be visible across numerous species in both mating systems. We hypothesized we would see an inverse relationship between abundance and ASR across polygynous populations, and no relationship between abundance and ASR across monogamous populations. We extracted time series population data from published literature for 43 populations of 15 different mammal species. Results from our analysis of a linear mixed-effects model were consistent with our hypothesis for polygynous populations, as we found a significant inverse relationship between abundance and ASR. However, our analysis also revealed a significant inverse relationship between abundance and ASR in monogamous populations that was not consistent with our hypothesis. Our findings provide quantitative support for a theoretical model explaining the evolutionary and ecological mechanisms driving a density-dependent relationship between abundance and ASR in polygynous mammals. An investigation into monogamous mammals is needed to assess why some species with this mating system display a density-dependent response in ASR as well.