Historically, closed eastern forests transitioned into open savannas and prairies in the U.S. Midwest, but this transition is poorly understood. To investigate the eastern boundary of the prairie-forest ecotone, we conducted a case study of historic and modern vegetation patterns of the Yellow River watershed in northwest Indiana. Historic vegetation came from the Public Land Survey notes collected in the early 1800s, whereas modern vegetation came from the Forest Inventory Analysis and USGS National Land Cover Database. We mapped vegetation data using GIS to reconstruct the region's past and current forest composition and structure. We also mapped climate, topography, and soil composition across the watershed to investigate the relationship between historic vegetation and environmental gradients. We found a sharp transition in the presettlement forest structure and composition, with dense deciduous forests in the eastern portion of our study area and open oak savannas in the west. The savanna ecosystem dominated in sandy well-drained soils and was at a slightly lower elevation than the adjacent closed forest. Modest environmental changes accompanied major vegetation changes in the past, which might suggest fire and hydrological patterns helped maintain the sharp ecotone. By contrast the modern forest shows no difference in tree density and composition across the watershed, which is consistent with major land use and hydrology changes in the watershed since settlement. On the modern landscape, land that was historically closed forest now has higher agricultural productivity compared to land that was historically savanna, whereas the historic savanna currently supports more mesic forest. These results suggest the environmental gradient continues to subtly shape the landscape. Though land use change has largely removed the closed mixed hardwood forests and oak savannas from this area, a better understanding of the historic vegetation and the conditions that supported it can help inform land management and restoration, as well as reveal ecological processes that drive vegetation transitions.

Changes in climate, land use and management have led to an increase in woody species encroachment into grasslands, threatening key ecosystem services and resilience. This study uses dendroecological techniques to investigate acclimation strategies of two native woody species, Juniperus virginiana and Pinus ponderosa, to spatial and temporal variability in precipitation and stand density in Nebraska (NE). Two locations in Eastern NE and one in Western NE, were selected and tree cores for ring-width measurements were collected. Stable Isotope ratios of carbon were analysed to investigate water use efficiency (WUE), and stable isotope ratios of oxygen were used to understand stomatal conductance and control. Our results showed trees in dense stands exhibited less intra-specific variability in response to climate and narrower tree rings than sparse open stands, with P. ponderosa being more responsive to density and climate variability than J. virginiana. Populations in the drier Sandhills grasslands of Western NE were more dependent on intra- and inter-annual precipitation and generally more impacted by drought events than those in the East. Eastern NE trees were less limited by drought and displayed lower WUE relative to Western location, even though temperatures were slightly higher, but this was compensated for by the overall higher precipitation levels in the East. Generally, above average winter temperatures were positively correlated with ring widths, while temperature extremes during the growing season were negatively correlated. Although years of extreme drought events were visible in the tree-ring width patterns for both species independent of stand density and location, it seems that once the trees are established and have access to soil moisture, the current climate variability and extremes in NE do not limit or cause a permanent decline in growth of either species.

Shortleaf pine (Pinus echinata), Missouri's only native pine species, experienced intense logging during the post-Civil War Ozark lumber boom. Although recent restoration efforts have occurred primarily on federal and state land, efforts are being made to incorporate shortleaf management strategies on private land through the distribution of 1 y old bare-root seedlings grown from seeds at the George O. White nursery in Licking, Mo. In this study we examined the genetic structure of Missouri's historic shortleaf pines to determine if geographic compartmentalization of seed stock was necessary. Using twelve polymorphic microsatellite loci, we genotyped historic shortleaf pine wood core samples from eight counties in the Missouri Ozarks and needles from seedlings provided by the George O. White nursery. Missouri's historic shortleaf pine populations exhibited high heterozygosity and no observable pattern of genetic structure between individuals of varying geographic location, diameter at breast height (DBH), or altitude. However, private alleles found in all but one of the historic populations suggest the presence of a form of genetic diversity in Missouri's shortleaf pine populations that is not present in the George O. White nursery stock. To maintain high levels of genetic diversity over the long term and prevent overrepresentation of alleles from nursery stock in reintroduced shortleaf populations, managers should consider increasing the number of individuals used as seed sources for seedling propagation.

Declining populations of forest songbirds in the eastern U.S. have emphasized a need for scientists and managers to understand habitat selection by birds in remnant patches of contiguous forest. Past work has identified effects of landscape-scale covariates on bird occurrence and abundance; however, less is known about the effects of local-scale forest structure. We applied a combination of forest inventory data and LiDAR-derived canopy height data to derive variables of local-scale forest structure in a managed forest. We then assessed the effects of these variables on the abundance of 18 forest bird species obtained from point counts, while accounting for imperfect detection using a combined distance and time-removal model. We found mean canopy height and terrain variables including elevation, slope, and aspect affected the local-scale abundance of the largest number of bird species and also had the largest effect sizes. Variables associated with vertical structure of the canopy were not important predictors of abundance. Our results confirm the importance of canopy height and terrain on abundance of multiple forest songbirds and emphasize the value of fine-scale spatial data for assessing bird habitat use.

Agriculture and development have caused landscape change throughout the southwestern Great Plains in the range of the lesser prairie-chicken (Tympanuchus pallidicinctus). Landscape alteration within the lesser prairie-chicken range may contribute to range contraction and population losses through decreases in survival rates. Our objectives were to determine if: (1) landscape configuration (i.e., the spatial arrangement of habitat) or composition (i.e., the amount of habitat), at the study-site scale, affected annual survival of females, (2) relationships exist between landscape context (i.e., landscape configuration and composition) and weekly survival to assess effects of landscape composition and configuration on lesser prairie-chicken populations, and (3) anthropogenic features influenced daily mortality risk. We captured 170 female lesser prairie-chickens and used very-high-frequency and GPS (Global Positioning System) transmitters to track their movement and survival for 2 y. We used known-fate survival models to test if landscape configuration or composition within three sites in Kansas were related to differences in female survival among sites. In addition we tested for relationships between weekly survival and landscape configuration or composition within home ranges. Finally, we used Andersen-Gill models to test the influence of distance to anthropogenic features on daily mortality risk. Differences in survival were evident between sites with differing landscape compositions as annual survival in Northwestern Kansas ( = 0.27) was half that of Clark County, Kansas ( = 0.56), which corresponded with 41.9% more grassland on the landscape in Clark County; landscape configuration did not measurably differ among sites. Survival was greater for prairie-chickens with home-ranges that had greater patch richness and in areas with 30% crop and 57% grassland. Female lesser prairie-chickens also experienced greater mortality risk closer to fences at patch edges. Further conversion of grassland landscapes occupied by lesser prairie-chickens should be avoided to reduce habitat loss and fragmentation thresholds that could affect survival. We suggest continued encouragement of Conservation Reserve Program enrollment in western areas of the lesser prairie-chicken range to maintain or increase the amount of grassland to increase annual survival.

The Mourning Dove (Zenaida macroura) is the most important game bird in central and northern Mexico, especially in the state of Jalisco. However, nothing is known about the dynamics of their populations during the nonbreeding season. To obtain an insight into these dynamics in Jalisco, Mourning Doves were counted every winter season from 2004/2005 to 2016/2017 along 10 routes throughout the state. Of these routes, only the data from eight were analyzed, because the two on the Pacific Coast were practically devoid of Mourning Doves. The data indicate Mourning Dove abundance in Jalisco during the nonbreeding winter season: (1) might reflect U.S. population changes two summers earlier, and (2) be significantly reduced from the 2004/2005 to 2014/2015 winter seasons, in part due to decreases in the U.S. central population, but seemingly also due to local, regional, or extra-regional processes yet to be understood.

Multivariate statistics are commonly used by ecologists to study spatial and temporal community dynamics to better inform management decisions. Since these methods are a universal tool to analyze data, it is important to assess their effectiveness using long-term datasets in well-studied systems. The objectives of this study were to identify trends in the fish communities and to characterize the community trajectory (i.e., directional or nondirectional) of the Illinois River, a large tributary to the Mississippi River, using nonmetric multidimensional scaling (NMDS). Although NMDS has been used to evaluate community trajectory in multivariate space over time in smaller rivers, there has been less attention given to larger rivers, which may exhibit different dynamics. To evaluate changes in large river fish communities, we used a long-term electrofishing monitoring dataset (1957–2013) that includes fish abundance data from six reaches of the Illinois River, Illinois, U.S.A. Temporal changes in Illinois River fish communities were evident in NMDS ordinations. Larger changes in NMDS ordinations were associated with improving water quality conditions, whereas the invasion of bigheaded carp (silver carp Hypophthalmichtys molitrix and bighead carp H. nobilis) produced smaller and less variable changes. Across all six reaches of the Illinois River, the trajectory of fish communities was directional in multivariate space, with no return to an initial or predisturbance condition. Community trajectory in larger and more heavily-modified rivers may be substantially different and more complex than that of smaller and less heavily modified rivers.

Extreme flood events can substantially affect riverine systems, modifying in-stream habitat and influencing fish assemblages and densities. Rare species are especially vulnerable to these disturbance events because of their small population size and often reduced phenotypic heterogeneity. In June 2016 the lower Elk River in West Virginia experienced severe flooding, resulting in a peak discharge that exceeded the 0.005 annual exceedance probability (>200 y flood) in the main stem. We obtained pre-flood and post-flood population count data and estimated abundances for one cohort of the federally endangered Diamond Darter (Crystallaria cincotta) at 15 sites. While both the total count data and total estimated abundance decreased following the flood, our analyses did not indicate the extreme flood event strongly impacted Diamond Darter abundance. This indicates individuals are able to withstand high velocities and resist displacement or mortality. In addition site-level abundances were estimated at three sentinel sites during 2015 and 2016 using a multinomial N-mixture model that accounted for variation in detectability resulting from water temperature. Mean estimated abundance varied among the three sites and between the 2 y. Our results suggest there is substantial variation in year-class strength between the two cohorts we sampled. It is suggested that survey efforts at established sentinel sites be continued on an annual basis in order to help determine factors influencing year-class strength.

We examined why the lower Little Colorado River (LCR), Arizona continues to be dominated by four native fish species despite decades of encroachment by nine nonnative species. Most perennial flow begins at Blue Spring, located at river kilometer (RKM) 20.74 above the LCR's mouth, which is supplemented downriver by other springs. Blue Spring's water is extremely supersaturated with dissolved CO₂ (658 mg/L), and at baseflow the CO₂ concentrations apparently functioned as a fish-barrier for about 1 km further downriver until it outgassed to 288 mg/L. Thereafter, CO₂ outgassed to 202 mg/L by the top of Chute Falls (RKM 14.20) and 76 mg/L near the river's mouth. Chute Falls, and high CO₂ levels above it, obstruct upriver, but not downriver, fish movements; however, we still captured fishes from eight nonnative species above this falls. Our findings indicate most warmwater nonnative fishes in the LCR were immigrants from upriver sources within and bordering the intermittent corridor that invaded the system during floods, while most coldwater trout invaded from the Colorado River. Most nonnative species failed or were severely limited at reproducing progeny in the LCR, except occasionally by channel catfish Ictalurus punctatus and fathead minnow Pimephales promelas in the lower 13.57 km corridor, which was likely related to CO₂. Correlation tests suggested severe flood and/or suspended sediment regimes reduced populations of fathead minnows, red shiners Cyprinella lutrensis, and plains killifish Fundulus zebrinus in the LCR. Conversely, severe suspended sediment regimes (especially ≥60,000 mg/L) increased channel catfish, black bullhead Ameiurus melas, and common carp Cyprinus carpio, hypothetically by paralyzing these fishes upriver, whereby many drifted downstream and recovered in the lower LCR; however, their abundances decreased after prolonged periods of high CO₂. Nonnative fishes are controlled in the LCR by the system's endemic abiotic conditions.

Since elk (Cervus elaphus) were extirpated from eastern North America, they have been successfully reintroduced in numerous eastern states and one Canadian province. In forest-dominated areas, reintroductions of large ungulates can create potential for conflict with humans if elk select agriculture or private property to meet nutritional needs. We determined the seasonal diet selection of recently reintroduced elk in the Missouri Ozarks by comparing diet composition with availability of 12 forage classes. We measured diet composition using microhistological analysis of feces collected from June 2011 through February 2013, and we determined forage availability through vegetation sampling. Elk selected grains and cool-season grasses over all other forage classes across all seasons and years except during summer 2012 and fall 2012. Legumes were the most highly consumed forage class for all seasons and years. Native forbs were selected during summer and fall 2012 but were not selected during 2011. Approximately half (44.6%) of the annual elk diet was comprised of species cultivated in managed forage openings. Clover (Trifolium spp.), alfalfa (Medicago sativa), and common lespedeza (Kummerowia spp.) were the most prevalent species in the elk diet, indicating the importance of managed forage openings for the Missouri elk herd. However, during a drought in 2012 elk diet shifted to native species, likely because elk became more selective of forages that met their nutritional needs. In forest-dominated landscapes, where conflict with humans on privately owned land is possible, we recommend the creation of forage openings composed of cool-season grasses and legumes to increase forage availability for elk. We recommend management for natural open lands that promote native forbs and grasses given they provide a valuable food source when environmental conditions affect availability, nutritional quality, or palatability of cultivated forages and because cultivated forage openings are not always an option in some areas or over long time periods.

River otter (Lontra canadensis) populations in Illinois have rebounded considerably after >80 y of harvest protection and a successful re-introduction program. However, few studies of river otter survival ecology exist in the Midwestern U.S. We estimated survival rates and mortality causes for river otters in southern Illinois during 2014–2016. Thirty-four (16 F, 18 M) river otters were radio-marked and monitored for 8235 radio-days (x̄ days/river otter = 242.2 ± 20.6 [se throughout]). Two males died (one trapped, one unknown) during the period of radio-telemetry monitoring. Annual survival rates were 1.0 ± 0.00 (lower confidence bound = 0.83) and 0.85 ± 0.09 for females and males, respectively, and similar between sexes (P = 0.19). Pooled-sex breeding season survival was 0.96 ± 0.04. Trapping was the primary cause of mortality during our study, and three river otters were killed after radio-telemetry ended: two were harvested by recreational trappers and one by a vehicle collision. These primary mortality sources (i.e., trapping and vehicle collisions) for river otters in southern Illinois were similar to those reported elsewhere, but the high survival we observed is similar to published estimates for unexploited populations. Our study provides useful demographic information for river otter management in lightly harvested populations in the Midwest.

The evening bat (Nycticeius humeralis) is considered a common species in southeastern United States, with historically few records in the Upper Midwest region of the United States. However, recent work in Michigan and Minnesota has shown that evening bats are becoming increasingly common in the region. After capture of a juvenile male evening bat in late summer 2015 in southern Rock County, Wisconsin, we radio-tracked three adult female evening bats in summer 2016 at the same Rock County location. These three bats were tracked to three roost trees with counts during evening emergence ranging from 20 to 103 bats. This work represents the first confirmed capture and roost site investigation for evening bats in Wisconsin and supports the idea this species is expanding its range.