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Invasive plants may disrupt symbioses between plants and soil biota. We tested whether ectomycorrhizal fungi (ECM) associating with Quercus rubra (Northern Red Oak) seedlings was lower near invasive Alliaria petiolata (Garlic Mustard). We quantified ECM colonization, identified morphotypes, and compared composition in forests with contrasting Garlic Mustard densities. Seedlings had lower ECM colonization and diversity in a stand with dense Garlic Mustard than in a stand without Garlic Mustard. ECM composition also differed between stands. Seedlings in a stand with moderate density Garlic Mustard had marginally less ECM than those at the no Garlic Mustard site. These findings suggest that ECM association is negatively correlated with Garlic Mustard invasion. This association may result in lasting changes to forest communities and hinder site restoration following Garlic Mustard removal.
Mowed roadsides represent a significant proportion of the grassland habitat in New England, but they receive little attention from naturalists. We sought to test the assumption that mowed roadsides are ecological wastelands dominated by deliberately seeded introduced perennial grass species. Surveys of seven sites in Rhode Island during the summer of 2008 revealed that roadsides are important refugia for grassland plants, including two species and two subspecies believed to be rare in New England. We found 80 grass and forb species, 45% of which are native. We also examined the effects of distance from the road and topography on the relative distributions of annual versus perennial species and of native versus introduced species. Perennial species cover increased with distance from the road at all seven sites, and the number of perennial species increased at five sites. The front slope had the most annual species and the most annual cover at all sites. Perennial species dominated the back slope, swale, and flat areas. Neither distance from the road nor topography had a clear effect on the distribution of native species relative to introduced species. Highway roadsides in southern New England are not an ecological wasteland, but rather are a complex upland grassland habitat reminiscent of the agricultural grasslands which dominated the region in the nineteenth century.
In the temperate deciduous forests of the northeastern United States, the majority of the dominant tree species disperse their seeds during the fall, causing a heterogeneous mixture of seeds to be present at a specific location at one time. Because these seeds vary in size and palatability to small mammals, some seed species, such as Quercus acorns, may alter the risk of removal of neighboring, less preferred species. The presence of a neighboring seed could attract seed predators, elevating the risk that a neighboring seed will be removed (apparent competition), or it could divert the attention of seed predators away from a neighboring seed (apparent mutualism). We evaluated the effects of nearest seed neighbors on the survival of 5 different tree species. Using logistic regression we determined whether the species or abundance of nearest neighbors caused changes in the risk of removal. Contrary to our expectations, we did not find any affect of neighboring seed species on the removal rates of other seeds, indicating that risk of removal of naturally occurring seeds, separated by at least 10 cm, is independent.
Selective browsing by Odocoileus virginianus (White-tailed Deer) has shifted plant communities in the Northeast, but the effects of seed dispersal by deer on forest seed banks are unknown. We used data from deer exclosures in hunted and unhunted properties in southeastern New York to determine whether deer browsing and different deer management histories have altered composition and/or abundance of forest saplings and seed banks. Results indicate that deer did not alter species richness, abundance, or composition in seed banks in either hunted or unhunted areas. Deer did, however, decrease sapling density and richness at the unhunted site but not at the hunted site. We conclude that impacts of unmanaged deer populations are greater on sapling recruitment than on seed banks.
We analyzed the survival rates of 160 Odocoileus virginianus (White-tailed Deer) over 6 years in the area of Wisconsin's highest prevalence of chronic wasting disease. Survival was very high for all age/sex classes and varied by season but not by year. When we omitted hunting mortality, yearlings and adults had similar annual survival, with survival of males (0.83–0.89) slightly lower than survival of females (0.91). However, including hunting mortality reduced survival of yearling and adult males to 0.72 and 0.41, and survival of yearling and adult females to 0.88 and 0.83, respectively. We also observed seasonal patterns, characterized by reduced survival across all sex and age classes during the rut season (10 October to 31 December), which includes the period of maximum hunting. Six mortalities (8.3%) were associated with chronic wasting disease, including one deer that died from the disease. We find no evidence that CWD was substantially increasing mortality rates during the duration of our study from 2003 to 2007, though the disease is relatively new to this area. Our results can serve as a baseline by which to compare future mortality rates in this area to assess the virulence of CWD over time.
Increasing urbanization in the United States presents new challenges and opportunities for wildlife species. One species that is thought to benefit from urbanization is Didelphis virginiana (Virginia Opossum). We used radio-telemetry to determine home-range size of opossums living in an urban area and compared body mass measurements of urban and rural animals to ascertain how urbanization affects this parameter for opossums. Minimum convex polygon estimates for male (37.3 ± 46.0 ha; n = 3) and female home ranges (18.8 ± 15.6 ha; n = 5) were smaller than those reported for opossums in rural areas and similar to those from previous urban studies. Opossums living within the city limits had an average body mass (3.0 ± 0.8 kg) that was 34% larger than those in rural areas (2.2 ± 0.6 kg). These data, combined with previous work, suggest that urban areas provide more resources and may be beneficial to opossum populations.
Bats vary their activity with different features of habitat, resource availability, predation risk, and other factors. Agricultural fields may provide an abundance of insect prey, but are also risky habitats due to their exposure. How bats use mixed landscapes is important information for biologists, as increasing development affects the amount of suitable habitat and impacts bat populations in the region. Using acoustic recording, we monitored relative bat activity in open areas and edges of the woodland/farmland interface of agricultural fields in Kent County, DE. We examined bat activity among different sites, in openings versus edges, among crop types, relative to nearby forest fragment size and shape, and under different weather conditions. Bat activity was significantly higher along edges than in the open in the agricultural fields for passes/night, but we found no differences among crop types or sites and no interaction effects. We also found no effect of size or amount of edge of a fragment on bat activity. We found significant negative correlations between passes and temperature and wind speed, and significant positive correlations between passes and relative humidity and barometric pressure. Bats use agricultural areas for foraging, and the woodland interfaces along these fields are important for bat activity. This study provides data that may help engender conservation practices, such as retention of forested edges and maintenance of tree lines, and perhaps crop selection and pest control management, in the region's farming community.
Dams fragment watersheds and prevent anadromous fishes from reaching historic spawning habitat. Sedgeunkedunk Stream, a small tributary to the Penobscot River (Maine), has been the focus of efforts to reestablish marine-freshwater connectivity and restore anadromous fishes via the removal of two barriers to fish migration. Currently, Petromyzon marinus (Sea Lamprey) is the only anadromous fish known to spawn successfully in the stream downstream of the lowermost dam. Here, we describe the distribution and abundance of a spawning population of Sea Lamprey in Sedgeunkedunk Stream, prior to and in anticipation of habitat increase after the completion of one barrier removal. In 2008, we estimated the abundance of Sea Lamprey and its nests using daily stream surveys and an open-population mark-recapture model. We captured 47 Sea Lamprey and implanted each with a PIT tag so that we could track movements and nest associations of individual fish. The spawning migration began on 18 June, and the last living individual was observed on 27 June. We located 31 nests, distributed from head-of-tide to the lowermost dam; no spawners or nests were observed in the tidally influenced zone or upstream of this dam. Mean longevity in the stream and the number of nests attended were correlated with arrival date; early migrants were alive longer and attended more nests than later migrants. Males were more likely to be observed away from a nest, or attending three or more nests, than were females, which attended usually one or two nests. We observed a negative association between nest abundance and substrate cover by fine sediment. Based on their observed movements in the system, and the extent of their habitat use, we anticipate that spawning Sea Lamprey will recolonize formerly inaccessible habitat after dam removals.
Notophthalmus viridescens (Red-spotted Newt) collected from 3 low-pH ponds (ca. 4.8) and 3 high-pH ponds (ca. 8.1) in Vermont varied in pH tolerance and water preference. While newts from all ponds survived in pH values as low as 4.4, the mean 10-day survival of newts in pH = 3.2 was 69% for newts from the low-pH Green Mountain ponds compared to 33% for newts from the high-pH Taconic Mountain ponds. Taconic Mountain newts selected water from Taconic ponds 73% of the time, while Green Mountain newts exhibited no preference for pond water from either mountain range. In order to isolate the effect of pH on water choice, we conducted an experiment in which newts chose between reconstituted soft water (RSW) that had been adjusted to either high pH (8.0) or low pH (4.5). Taconic Mountain newts selected high-pH RSW 72% of the time. Although Green Mountain newts exhibited no preference for pond water having high or low pH, they selected the high-pH RSW 70% of the time. These differences in pH tolerance and water preference between Green and Taconic Mountain newts may represent local adaptation shaping population distribution and divergence.
Spiza americana (Dickcissel) colonized a restored Conservation Reserve Program grassland in Maryland during the second year of restoration and has continued to return in subsequent years. In 2000–2010, we banded 125 adult and hatch-year birds; during this period the population ranged annually from one to 16 individuals. Twenty-one percent of adult male Dickcissels (n = 38) returned in a subsequent nesting season, 30% of adult females (n = 20) returned, and 1.7% (n = 67) of the banded hatch-year individuals returned. A female Dickcissel returned to these grasslands after being banded as a nestling the previous year; this bird is the first nestling Dickcissel ever to be re-sighted in a subsequent year across this species range. This same female Dickcissel nested an average of 196.5 m (range = 84–297 m) from her natal site over four breeding seasons, and now holds the longevity record (4 yrs, 11 months) for the species; she also became the first known female Dickcissel to return to a breeding site in Maryland. At our study site, whether adult Dickcissels returned the following summer was not related to their nesting experience (success or failure) the previous year. However, males that were unsuccessful in procuring mates often did not return the following year, and females returned at a greater rate than males.
Thalassarche melanophrys (Black-browed Albatross) has rarely been sighted in the northwest Atlantic, with fewer than 30 anecdotal and fewer than 10 confirmed sightings spanning the West Indies north to Greenland. On 8 August 2009, a Black-browed Albatross was observed from a longliner conducting an exploratory Chionoecetes opilio (Snow Crab) survey, off the coast of northern Labrador. This sighting currently represents the most northerly record for continental North America. The only more northerly records are two specimens seen off Greenland. Black-browed Albatrosses have been seen more frequently, though rarely, in the eastern North Atlantic, while they have yet to be documented in the north Pacific. Given the higher frequency of sightings along the European coast, it may be that the majority of Black-browed Albatrosses crossing the equator are traveling up the African coast. Black-browed sightings on the Atlantic coast of North America therefore may originate in northern Europe, or from birds traveling along the Atlantic coast of South America.
Clangula hyemalis (Long-tailed Ducks) were observed diving in the wake of the Nantucket Island ferry during December over a 5-year period (2005–2009). The unusual diving behavior appeared to be related to foraging, but could not be confirmed. Long-tailed Ducks typically feed on more mobile prey than most other diving ducks, and it is speculated that the propeller wash in shallow water dislodged or disturbed prey and provided an enhanced feeding opportunity. Long-tailed Ducks collected while feeding in a disturbed area near a clamming boat not far from the ferry channel were feeding predominantly on Crangon septemspinosa (Sand Shrimp) that apparently had been dislodged by the clamming operation.
The range of Okanagana rimosa (Say's Cicada) in eastern North America appears to be widespread but patchy. We report the first known occurrence of mating by the species in New Jersey. We also report the first known record of the species from the state from a previously unpublished specimen collected in 1942 and deposited in the American Museum of Natural History collection. These two reports spanning 68 years are the only known specimens from New Jersey.
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