Management and control of biological invasions and emerging infectious diseases are leading topics of research in theoretical and applied ecology. When the initial number of potentially invasive or infectious individuals is small, demographic stochasticity can lead to rapid extinction, suggesting that the transient dynamics of establishment for invasive species and epidemics should be modeled as a stochastic process. Quantitative risk assessment can exploit this conceptualization to calculate risk metrics such as the chance of invasion or epidemic and to study the potential effectiveness of rapid response interventions. Here I review some simple establishment models and demonstrate how understanding the underlying stochastic processes can lead to more effective policies for risk management. As examples, I study the dynamics of feral nutria (Myocastor coypus) in East Anglia, UK, and infection by bovine tuberculosis (Mycobacterium bovis) in various species. Nutria are fur-bearing aquatic mammals that have been introduced around the world intentionally and through escape from farms and cause severe damage to marsh vegetation. Bovine tuberculosis is a chronic wasting disease of diverse mammal species and results in long term emaciation and decline in animal fitness. I find that both nutria and bovine tuberculosis exhibit high intrinsic rates of increase as measured by their increase in abundance when the population or epidemic is small. While Allee effects may affect the chance of establishment for nutria, analysis of additional data will be required to reject the hypothesis that nutria dynamics follow the simple Ricker growth model. The distinction is important, however, as the estimated chance of establishment under the Allee effect model is considerably less than under the Ricker model for introduced populations less than about 850 individuals. The chance of bovine tuberculosis epidemic for introductions of small numbers of individuals infectious with bovine tuberculosis in populations of brushtail possums (Trichosurus vulpecula) or badgers (Meles meles) is high. Thus, if surveillance programs are not almost completely effective at preventing introductions of infectious individuals, periodic outbreaks are likely to occur. Epidemics in these species might be controlled by culling.

Ecosystem stability processes such as constancy, resilience and persistence are important, but often neglected, topics of invasive species research. Here we consider how invasive dreissenid mussels affect ecosystem stability processes in Lake Erie through both consumptive and excretory processes using the stability landscape heuristic (Gunderson, 2000). Consumption of phytoplankton by dreissenid mussels adds complexity to the system and potentially slows energy transfer from lower to higher trophic levels decreasing system constancy and lowering system resiliency. Excreting soluble waste products at low nitrogen to phosphorus ratios exacerbates these impacts on stability processes because low nutrient ratios favor growth of cyanobacterial blooms, less preferred food of zooplankton, further decreasing the transfer of energy from lower to higher trophic levels. We also provide evidence for recent changes in Lake Erie's stability landscape including a return towards eutrophy.

Generalist parasites have been shown to have the potential to substantially affect the structure of the communities they inhabit. In order to predict the potential effects of these parasites, understanding the relationships they have with their host species is critical. In this study, the host range of Cuscuta gronovii was determined at two different times during the growing season, which corresponded with two life stages of parasitic individuals, seedling and adult. Field observations suggest that most of the successful infections by seedlings occurred upon only Impatiens capensis, one of the many species that it infects as an adult. This paper reports three tests of the hypothesis that I. capensis is a necessary nurse host for the parasite C. gronovii. In early summer survey plots, I. capensis was found to be infected by C. gronovii seedlings significantly more than predicted by the null hypothesis that all species in the plot were equally likely to be infected. In a late winter survey, in which all plants in a wetland infected with C. gronovii were identified and their positions mapped, I. capensis hosts were significantly closer to non-I. capensis hosts than predicted by the null hypothesis that infected I. capensis were distributed independently of non-I. capensis hosts. Finally, in a field experiment, newly germinated C. gronovii seedlings that were tied onto I. capensis and two other common hosts succeeded in infecting only on I. capensis. These results suggest that I. capensis acts as a necessary nurse host for C. gronovii in spring flooded southeastern Michigan wetlands.

Mitchell's satyr (Neonympha mitchellii mitchellii) is a restricted fen species currently listed as endangered by the U.S. Fish and Wildlife Service and is considered one of the rarest butterflies in North America. The objectives of this study were to estimate population size, determine distribution within the study site and characterize habitat use for this important species. A mark-release-recapture study conducted at a prairie fen in Jackson County, Michigan, yielded a total population estimate of 1106 individuals. Most N. m. mitchellii were captured at the interface of open fen or sedge meadow and tamarack/hardwood forest within 3 m of woody vegetation. Distribution of N. m. mitchellii within the fen was clumped. The longest distances flown by males and females were 511.8 m and 344.8 m, respectively. Minimum home range values were 0.22 ha for males and 0.07 ha for females. Compared with prior studies on two populations in southwestern Michigan, these individuals flew significantly farther and had much larger population and home range sizes. This new information is critical for the conservation of the species and provides evidence that individuals may be capable of dispersing to new areas if linkages exist between isolated colonies.

Although marking methods are available for identifying larval and adult amphibians, techniques for egg masses have not been tested. Individual egg masses can be difficult to relocate and monitor because they are similar in appearance and often found within communal aggregations. We evaluated a method of marking spotted salamander (Ambystoma maculatum) egg masses with visible fluorescent elastomer (VIE) and provided the first assessment of an identification technique for this life stage. Laboratory and field experiments tested for effects of VIE on the development of embryos, retention in the jelly matrix and the practicality of this technique in the field. We found no effect of VIE on survival or hatching of embryos, nor on body size and developmental stage of hatchlings compared to unmarked controls. In the laboratory, marks remained intact and identifiable within the jelly matrix until hatching was complete (>35 d). In the field, marks in the outer jelly matrix remained intact for 83% of developmental days; marks in the inner matrix remained intact longer for 97% of developmental days. We found this method efficient for large samples and were able to locate VIE-marked egg masses at depths typical of oviposition sites (0.05–0.45 m). We suggest that the VIE technique has broad applications and would be suitable for other species with similar egg jellies. When combined with methods for larvae and adults, this technique may facilitate identification for multiple life stages and improve tests of individual-based allocation, population and life history models.

Migration is an important part of many temperate bird species' annual life history. We used a time-point census method to describe the changes in bird communities during the autumn migration in central Iowa. Site selection within a second-growth forest varied significantly based on diet and migration habits of birds. Temporal changes in individual activity and species presence show preferences that may be related to availability of fruit. We discuss the effect of the invasive shrub Rosa multiflora on bird abundances on both temporal and spatial scales.

Forest fragmentation can influence abiotic and biotic factors important for the reproduction and survival of animals. Previous investigations suggest that, in the fall, more food is available for white-footed mice (Peromyscus leucopus) in edge than interior habitats and in small than large forest fragments. However, in the winter, individuals in small fragments and edge habitat may be more exposed to harsh weather extremes, which can result in higher mortality. We examined the effects of fragment size (small and large) and habitat (edge and interior) on populations of white-footed mice during nest box censuses in the winter (January–April) of 2003 in southwestern Ohio. While population density was initially higher in small than large fragments and edge than interior habitats, by the end of the winter there were no significant differences in population size. Populations in small fragments and edge habitat had larger decreases and greater rates of decline in density than those in large fragments and interior habitats over the course of the winter. These results suggest that while small fragments and edge habitat may be high quality habitat in the fall, animals in these areas may suffer higher mortality rates during the winter, compared with animals in large fragments and interior habitat.

On two barrier islands of Georgia, U.S.A., three species of sandspur (genus Cenchrus) occupy different types of habitats: Dune sandspur (C. tribuloides) occurs in newly formed dunes; southern sandspur (C. echinatus) occurs in established dunes; and coast or field sandspur (C. incertus) in areas associated with high levels of human disturbance (“waste places”). All three species have seeds with spines. I investigated the roles of spines in each species' natural history, giving particular attention to the contrasting habitats occupied by each. Seeds from C. tribuloides typically float more than twice as long as seeds of the other two species, as might be expected for this coastal species, yet experimental removal of spines did not decrease the floating duration for any species. In a wind tunnel, unaltered seeds of C. echinatus dispersed at lower wind speeds than did the other species, but experimentally removing spines gave its seeds wind-dispersal properties similar to the other two species. This suggests that spiny seeds increase wind dispersal for that species occupying habitats of open sand flats, precisely where wind dispersal is common. Tethered spineless seeds of C. tribuloides (the only species with seeds large enough to tether) were also more susceptible to predation by crabs, the most common granivore of the sand dunes. Therefore, spines serve to protect against predation in open areas. This study demonstrates the multiple roles that spines can play in seed performance and how these roles may differ among species according to the habitats in which they occur.

Goldenseal, Hydrastis canadensis L., is a herbaceous understory plant of the eastern deciduous forest that is harvested from natural populations due to its medicinal value. The objectives of this study were to determine if regrowth from harvest varies between patches and also to relate regrowth to pre-harvest leaf and patch size. We used data from three experimentally harvested natural patches and data on recovery of an illegally harvested patch harvested at the end of the growing season. We found variation in patch regrowth which suggests harvest technique and timing may be important. Experimental rhizome removal during mid-summer resulted in slower recovery of leaf size relative to the patch that was illegally harvested. We found a trend for reduced leaf area 2 y post-harvest relative to that pre-harvest. We also found variation in stem count between patches in response to harvest, which may be due to the pre-harvest size of ramets. The patch with larger pre-harvest ramets showed compensatory growth in the year immediately after harvest while the patches comprised of smaller ramets did not. Our results indicate that response to, and recovery from, harvest varies between patches and that individual ramet leaf size may be a better predictor of patch recovery than stem count. Because regrowth may be affected by harvest timing, an established harvest season may alleviate some harvest pressure on H. canadensis.

Red brome [Bromus madritensis subsp. rubens (L.) Husn.] is a Mediterranean winter annual grass that has invaded Southwestern USA deserts. This study evaluated interactions among 13 Sonoran Desert annual species at four densities of red brome from 0 to the equivalent of 1200 plants m⁻². We examined these interactions at low (3 μg) and high (537 μg NO₃⁻ g soil⁻¹) nitrogen (N) to evaluate the relative effects of soil N level on survival and growth of native annuals and red brome. Red brome did not affect emergence or survival of native annuals, but significantly reduced growth of natives, raising concerns about effects of this exotic grass on the fecundity of these species. Differences in growth of red brome and of the three dominant non nitrogen-fixing native annuals at the two levels of soil N were similar. Total species biomass of red brome was reduced by 83% at low, compared to high, N levels, whereas that of the three native species was reduced by from 42 to 95%. Mean individual biomass of red brome was reduced by 87% at low, compared to high, N levels, whereas that of the three native species was reduced by from 72 to 89%.

Indiana's system of natural area reserves is evaluated to assess the system's conservation value for imperiled butterflies. This system of nature reserves was designed to conserve representative examples of all terrestrial community types present in the state. It is one of the more long-lived attempts to develop a representative conservation system in the United States. The system of complementary reserves appears to be conserving most of the state-imperiled butterfly fauna. Of the 38 species evaluated, 32 are known to occur on sites that are either part of the reserve system or on sites that have been identified as priority additions to the system of reserves. There are 187 known populations of state-imperiled butterflies within the nature reserve system and on other public lands. Species with specialized habitat requirements such as fen, prairie, glade and oak savanna are well represented in the system. The system fares less well at conserving species at the extreme periphery of their range. These species, which have few known populations in the state, are sparingly represented or are missed entirely by the system. A few rare, but widespread, species of forested habitats are also poorly represented in the system.

Four butterflies with discernable phenotypic variation are also evaluated to determine if the reserve system adequately captures phenotypic variability across the state. Divergent populations of all four species were captured within the system.

A study of the fish faunas in all or parts of seven Illinois river basins revealed an average loss of 8.4 species per basin over approximately the last 100 y. In contrast, between the 1980s and 1990s, five basins showed an increase in the species richness (number of species) and two showed a statistically significant increase (paired t-test) in the species richness per sample site. Only the Kaskaskia River basin had a significant decline (paired t-test) in the species richness per sample site between the 1980s and 1990s. Minnows (Cyprinidae) had the largest number of species showing declines over the last 100 y and was followed in decreasing order by darters and perches (Percidae), catfishes (Ictaluridae), suckers (Catostomidae), topminnows (Fundulidae) and sunfishes (Centrarchidae). Changes in the overall fauna since the 1980s show an increase in species occurrence, but minnows and catfishes showed little net change and suckers, sunfishes and darters showed a positive increase in occurrence.

Rodent prey of the barn owl (Tyto alba) partly reflects the availability of prey species of small mammals. However, small- to moderate-sized mice of the genera Sigmodon (cotton rats), Oryzomys (rice rats) and Microtus (voles) are selectively preyed upon when available, and species of Dipodomys (kangaroo rats) are often underrepresented prey items. The range of T. alba in north Texas overlaps the restricted range of the little-studied Texas kangaroo rat (D. elator). Examination of regurgitated barn owl pellets provides the first documentation of predation on this distinctive rodent. However, given the ready availability of this kangaroo rat, its representation as a prey species of the barn owl is lower than expected, even given the usually poor representation of other Dipodomys species from other localities. Selective predation on favored prey and presence of other buffer species are certainly contributory factors to the low incidence of kangaroo rats in owl pellets. Some predator avoidance mechanism(s) of Dipodomys, perhaps especially well developed in D. elator, might also be implicated.

The carcasses of Pacific salmon can be an important food resource for aquatic and terrestrial organisms, depending on where the carcasses are located. We hypothesized that the availability of sockeye salmon (Oncorhynchus nerka) carcasses to ovipositing flies (Family: Calliphoridae) would be facilitated by brown bears (Ursus arctos) moving salmon from the water to terrestrial environments. We further hypothesized that the proportion of carcasses in terrestrial environments (hence accessible to flies) would vary among streams as a function of stream size. In three small southwestern Alaska streams during 2 y, flies oviposited on about half of the carcasses in terrestrial habitats (44% of those on gravel, 54% in grass and 57% in the forest). Only 28% of the partially submerged carcasses and 0.5% of the fully submerged carcasses were colonized. The proportion of carcasses deposited outside the stream was strongly and positively influenced by the level of bear predation and negatively affected by stream complexity (in deeper more complex streams more carcasses remained in the water). Based on data from the past 12 y on sockeye salmon abundance and predation by bears (averaging about 40% of the salmon), we estimated that on average 204, 551 and 839 carcasses were colonized per km annually in the three streams (12 to 24% of the total number of carcasses). In these sites, where salmon are abundant and highly available to bears, a large fraction of the tissue is not consumed and so is available to flies. Fly maggots, numbering up to 50,000 per carcass, can consume virtually an entire salmon within 5 d. Thus bears as consumers and transporters of carcasses facilitate the scavenging of carcasses by maggots, increasing the transfer marine-derived nutrients from aquatic to riparian habitats.

The Cape fur seal (Arctocephalus pusillus pusillus) is a common pinniped species along the southern African coastline. While much information is available about this species, little is known concerning its reproductive energetics. With radio telemetry, we monitored attendance patterns for 1 to 4 mo from 1996–1999. Attendance of 29 nursing females averaged 1.86 ± 0.77 d on shore and 5.23 ± 2.87 d at sea. Mean cycle time was 7.09 ± 4.33 d, of which 29.6% was spent on shore and 70.4% at sea. A significant increase in length of time at sea was observed during the first 4 mo of lactation.

Reproductive condition was quantified using measures of body condition and milk composition. Milk ingestion and field metabolic rates established a baseline for the energetics of 1 mo old pups. Body composition averaged 11.05 ± 2.31% lipid and 19.15 ± 2.60% protein. Milk from 17 individuals was composed of 58.07 ± 6.79% water, 2.02 ± 0.58% ash, 10.76 ± 1.23% protein and 23.16 ± 8.24% lipid. Milk energy content averaged 11.02 ± 3.10 kJ ml⁻¹. Thirteen pups consumed milk at a rate of 136.58 ± 29.11 ml kg⁻¹ d⁻¹. Mean energy intake was 1505.10 ± 320.80 kJ kg⁻¹ d⁻¹, with 37.16 ± 8.04% going to body maintenance and 62.84 ± 8.04% to growth. Fat and protein tissue was deposited at a rate of 16.10 ± 34.93 g d⁻¹ and 21.40 ± 59.20 g d⁻¹, respectively. Pup mass gain averaged 99.30 ± 3154.10 g d⁻¹. Male and female pups differed significantly in body mass and field metabolic rate.

Sympatry among bobcats (Lynx rufus), coyotes (Canis latrans) and gray foxes (Urocyon cinereoargenteus) is relatively recent in the southeastern United States given recent expansion of coyote range. Interspecific relationships among canids and felids have been documented in northern latitudes. However, interactions among these three species at southern latitudes are poorly understood. We examined overlap in space use of sympatric bobcats (n = 47), coyotes (n = 37) and gray foxes (n = 27) in central Mississippi during 1993–1997. Home ranges of all three species overlapped extensively. However, gray foxes maintained core use areas that did not overlap substantially with those of bobcats and coyotes. Home range and core area overlap were similar across seasons among all species. Our findings indicate that these three species readily share space, but gray foxes apparently maintain core areas in areas void of concentrated bobcat and coyote use.

Unsuccessful oak (Quercus spp.) regeneration could result in losses of the rarer portions of the midwestern North American oak savanna region, including the tall grass oak savannas. We undertook this study to understand the effects of restoration on promoting growth of naturally occurring Q. alba seedlings in a degraded tall grass oak savanna in Iowa, USA. Initial restoration efforts, which involved mechanical removal of encroaching overstory trees, promoted positive increases in height and basal diameter of Q. alba seedlings in canopy gaps. Conversely, seedlings growing under Q. alba tree canopies in restoration areas and seedlings in control areas failed to display height and diameter increases. As seedlings were most abundant beneath Q. alba canopy trees, this created a dichotomy whereby seedling source (beneath canopies) and proper conditions for growth (in canopy gaps) were not one in the same. Although this restoration is still in its early stages, these results suggest that Q. alba regeneration may be successfully promoted at this site.

Visual and chemical cues may provide predators with information on the abundance and quality of prey in a particular area. In a laboratory study we investigated if general cues of prey and prey habitat had an effect on the patch selection and orientation of Chinese praying mantis nymphs (Tenodera aridifolia sinensis Saussure). For location, juvenile mantids spent more time on the side of the arena with chemical cues from crickets relative to a blank control and more time on the side with brightly colored images of flowers relative to a “grass” control. For orientation, individuals spent more time oriented toward moving crickets and images of flowers than control sides of the arenas. Use of these cues may aid mantis nymphs in locating prey in nature.

Slimy sculpin (Cottus cognatus) are found throughout much of North America; however, their presence has never been recorded on Prince Edward Island (PEI), Canada. After slimy sculpin were discovered in one river in western PEI (Big Pierre Jacques River), all of the rivers on PEI were sampled to determine their distribution. Sculpin were discovered in one additional watershed, the Brae River, which is separated from the Big Pierre Jacques by one watershed. In both rivers, all age classes of sculpin were present, indicating a healthy population. As there are no historical records of slimy sculpin in the province, it is not known whether these fish were introduced to the area, or whether they were historically present but were extirpated from other rivers across the province.