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Detailed baseline inventories provide the foundation for the conservation of biodiversity. This fundamental knowledge, however, is lacking for lichens in southwestern Ontario. As a result we selected Awenda Provincial Park for a lichen survey because of its diverse and uncommon mesohabitats likely to contain previously unreported species, such as its 285 ha old-growth deciduous forest and its Quercus-Pinus savannah. Two hundred and three species were discovered in 96 genera. Four species are reported as new to Ontario: Abrothallus caerulescens, Bacidia kekesiana, Cheiromycina flabelliformis, and Lecanora minutella. Thirty-five species have a provincial conservation rank of S1 (critically imperiled), S2 (imperiled), or S3 (vulnerable). The five species that are ranked S1 are: Acarospora sinopica, Acrocordia cavata, Anisomeridium biforme, Chaenothecopsis savonica, and Leimonis erratica. Our results illustrate the conservation importance of Awenda and contribute to a better understanding of the distribution and frequency of lichens in Ontario. This baseline data can be used to apply conservation status ranks with more accuracy and monitor changes in populations caused by climate change, air pollution, or other disturbances.
Centaurea stoebe is a major invader of sensitive dune habitats of the Great Lakes region in North America, home to many unique and increasingly rare species. We analyzed the beginning stages of invasion of Centaurea on a relatively isolated island in northern Lake Michigan and sought to determine whether Centaurea is negatively impacting two species of concern, Cirsium pitcheri and Tanacetum huronense. Using a nearest neighbor analysis of mapped individuals in a long term study plot, we determined Centaurea, Cirsium, and Tanacetum all have aggregated underlying spatial structures. Two-species analyses revealed highly statistically significant segregation between the species but no significant positive or negative association between the invader and either native species. Using abundance data in widespread smaller plots, we found no statistical indication that high abundances of Centaurea were correlated with low abundances of the two native species, despite marked increases in the invader.
In the face of evidence across North America of the detrimental effects of the Centaurea invasion, our results are surprising. The clumped distributions of the invader and the two native species decrease the chance for interspecific interactions. Therefore, detecting negative impacts of an invading plant species in the early stages of an invasion will require a more experimental approach, where native and invasive plants are observed in direct competition.
A variety of nonprairie landscapes, including pastures, crop fields, and unmanaged seral ground, are being restored to native prairie on a yearly basis. Seldom is the seed bank associated with these nonprairie lands taken into account in the restoration process. We examine the seed bank potential of nonprairie lands and the relationship between aboveground vegetation and seed bank composition at the largest grassland restoration east of the Mississippi River, the Midewin National Tallgrass Prairie (U.S.A.), by surveying six land management histories: remnant prairie, restored prairie, new pasture, active pasture, old field, and crop field. Both aboveground vegetation and seed bank composition varied with land management history. However, species composition of aboveground vegetation differed significantly from the species composition of the seed bank irrespective of land management history. Aboveground vegetation carried a higher proportion of the seed bank flora than vice versa. In contrast to seed banks of other types of grasslands, the seed bank of historical prairie lands in the U.S. Midwest, irrespective of subsequent land-use history, is not a viable source of species for restoration of tallgrass prairie. A deficiency of many species in the seed bank flora, coupled with an abundance of weedy, often nonnative species, limits the potential contribution of the seed bank to restoration of a prairie vegetation community. Nevertheless, seed bank studies can provide a cost effective method to detect problematic species (i.e., weedy and/or invasive species) and therefore provide a window into the restoration potential of nonprairie lands.
CO2 flux from soil is a significant component of total atmospheric carbon, as well as an indicator of soil biological health, a useful tool for evaluating the impact of agricultural practices, and a key variable relevant to global climate change. A year-long study was conducted to evaluate subterranean termite contribution to soil CO2 flux on Oklahoma's Joseph H. Williams Tallgrass Prairie Preserve. Gas samples were extracted from metal flux chambers located within soil plots containing naturally occurring populations of foraging subterranean termites and from two different types of control plots without termites. Results indicate that CO2 flux during January, March, April, June, July, and December was similar among all three treatments. However, CO2 flux in control plots during May was significantly greater compared with termite-active plots. Overall CO2 flux from both termite-infested and termite-free plots was great enough to obscure CO2 contributions from subterranean termites alone. Therefore, although total normal baseline CO2 emissions from soil were measured, the specific amount of CO2 that termites alone contributed to this flux could not be accurately determined.
The spatiotemporal interaction between fire and grazing was a key process in the development of North America's grasslands. Restoring interacting fire and grazing may be instrumental in conserving rangeland biodiversity, but a need exists to understand how it affects organisms in highly fragmented grassland landscapes. We examined nest survival of a species of conservation concern, the Eastern Meadowlark (Sturnella magna), in fragmented Midwestern grasslands that varied in the spatial and temporal application of fire and grazing. The patch-burn grazed treatment (i.e., interacting fire and grazing) consisted of burning a different third of a pasture annually. Pastures in the grazed-and-burned treatment were burned in their entirety every third year and both treatments were moderately stocked with cattle. Average daily nest survival rates were similar across treatments (patch-burn grazed: incubation = 0.90 and nestling = 0.93, grazed-and-burned: incubation = 0.90 and nestling = 0.92), but patch-burn grazing resulted in more stable survival rates from year to year, while the grazed-and-burned treatment appeared to create a boom and bust survival cycle (patch-burn grazed range = 12–16%, grazed-and-burned range = 2–31%). Models indicated a treatment-year interaction, nest stage, and woody vegetation most affected the overall probability of nest survival. Nest survival was greatest in 2009 when grazed-and-burned pastures were burned but dropped dramatically the following year in that treatment. Nests had a higher probability of survival during the nestling stage (β = 0.49, se = 0.27), and woody vegetation near the nest resulted in lower survival (β = −0.07, se = 0.04). Parasitism rates were greater in grazed-and-burned pastures and reduced clutch sizes by an average of 0.6 eggs but did not affect the number of chicks fledging per nest. Overall, our findings suggest restoring heterogeneity to fragmented grasslands through patch-burn grazing can positively affect Eastern Meadowlarks by stabilizing nest survival rates over time.
We examined golden-cheeked warbler (Setophaga chrysoparia; hereafter warbler) behavior by age, sex, and habitat characteristics across their breeding range in central Texas (1995–1997). This federally endangered songbird foraged more on oak (Quercus spp.) substrates early in the breeding season and more on Ashe juniper (Juniperus ashei) late in the breeding season. We observed no overall difference in tree species use by warbler sex and age; however, we detected female and juvenile warblers in the low and middle canopy more often for all behaviors than males. Also, female warblers rested less and foraged twice as much as male warblers, who instead vocalized more than females and juveniles. In the southernmost study location, male warblers foraged more and vocalized less. More specifically, they foraged more on oaks when compared to other tree species, suggesting vegetation may influence warbler behavior in some locations. As the breeding season progressed, warblers increased their use of lower tree height classes for foraging and nonforaging behaviors. Site-specific vegetation management practices incorporating structural and compositional heterogeneity may better address the habitat needs of both warbler sex and age groups.
The Chinese mantis, Tenodera aridifolia sinensis (Saussure), is a univoltine tritrophic predator of old fields, now widespread after its introduction into North America more than a century ago. In 3 y of study of a population in eastern Virginia, we observed several unusual features in this oldfield insect: >90% of egg cases deposited in shrubs and trees, many at heights >2 m, not on goldenrods and similar herbaceous plants as previously reported. Egg cases were nonrandomly oriented (to the south) but with no significant association between compass orientation and days to hatching of young. Egg cases were randomly dispersed but least dense in patches without woody plants, the opposite of expectation for an oldfield insect. Finally, smaller egg cases yielded fewer and later-hatching young when oriented towards the south. A parsimonious explanation is that some females produce >1 egg case in eastern Virginia, with later egg cases being smaller and with fewer eggs because of reduced food intake. Furthermore, the southerly orientations of egg cases in trees may relate to more degree-days for greater metabolic efficiencies for females late in the growing season. Supporting this argument is a later study of temperature variation on 5 y old pine trees, which showed that south-facing locations at ground level, 1 m, and 2 m were significantly warmer than comparable north-facing locations, especially at 2 m.
Channel catfish (Ictalurus punctatus) are a popular target for Nebraska anglers, and the proportion of Nebraska anglers targeting catfish is consistently 50% or greater on an annual basis. Commercial fishing for channel catfish was legal on the Missouri River, in Nebraska, from the 1800s until 1992. Several studies have been published regarding channel catfish population characteristics in this reach prior to the closure of commercial fishing; however, there have been no long-term assessments done post-closure. There is concern among anglers and managers about numbers and size of channel catfish in the Missouri River and a desire to better understand population dynamics in order to better manage channel catfish stocks. The goal of this study was to assess spatial and temporal changes in population characteristics of channel catfish in the Missouri River, Nebraska from 1998 – 2013. Specifically, we asked: (1) did channel catfish population characteristics differ among four reaches of the river from 1998 to 2013 and (2) did channel catfish population characteristics exhibit any temporal trends within reaches from 1998 to 2013? We found channel catfish in Nebraska portions of the Missouri River are characterized by slow growth and high mortality. The majority of fish sampled were age-3 or younger and fish age-6 or older were rare. Mean lengths have decreased since the early 1990s and are similar to mean lengths before closure of commercial fishing. Relative abundance decreased in two reaches and was below the 15 y mean in all reaches from 2008-2013. We recommend management goals and objectives be updated and individual goals and objectives intended to decrease mortality and improve size structure be developed for the four study reaches.
Invasion of North American waters by nonnative Dreissena polymorpha and D. rostriformis bugensis has resulted in declines of the Unionidae family of native North American mussels. Dreissenid mussels biofoul unionid mussels in large numbers and interfere with unionid movement, their acquisition of food, and the native mussels' ability to open and close their shells. Initial expectations for the Great Lakes included extirpation of unionids where they co-occurred with dreissenids, but recently adult and juvenile unionids have been found alive in several apparent refugia. These unionid populations may persist due to reduced dreissenid biofouling in these areas, and/or due to processes that remove biofoulers. For example locations inaccessible to dreissenid veligers may reduce biofouling and habitats with soft substrates may allow unionids to burrow and thus remove dreissenids. We deployed caged unionid mussels (Lampsilis siliquoidea) at 36 sites across the western basin of Lake Erie to assess spatial variation in biofouling and to identify other areas that might promote the persistence or recovery of native unionid mussels. Biofouling ranged from 0.03 – 26.33 g per mussel, reached a maximum in the immediate vicinity of the mouth of the Maumee River, and appeared to primarily consist of dreissenid mussels. A known mussel refugium in the vicinity of a power plant near the mouth of the Maumee actually exhibited very high biofouling rates, suggesting that low dreissenid colonization did not adequately explain unionid survival in this refugium. In contrast, the southern nearshore area of Lake Erie, near another refugium, had very low biofouling. A large stretch of the western basin appeared to have low biofouling rates and muddy substrates, raising the possibility that these open water areas could support remnant and returning populations of unionid mussels. Previous observations of unionid refugia and the occurrence of low biofouling rates in large areas of the western basin of Lake Erie raise the possibility that unionid and dreissenid coexistence may be possible here and elsewhere.
This study documents the causes of mortality of juveniles in a declining population of thirteen-lined ground squirrels (Ictidomys tridecemlineatus). We found a dramatic decline in juvenile numbers between emergence from the natal burrow and the onset of hibernation. From 2005 to 2007, an average 70.6% of all juveniles disappeared from the population (n = 168 males and 224 females), including a 72.0% loss of males and 65.2% loss of females (χ21 = 2.1, P > 0.10). Weekly loss of juvenile males peaked 3–4 w after emergence while female loss remained relatively stable through summer. Radio-tracking enabled us to eliminate dispersal as a cause of the decline in juvenile numbers. Predation accounted for at least 71.4% of mortalities in radio-collared juveniles (66.7% of males and 76.0% of females; χ21 = 0.087, P > 0.75). We found no sex differences in specific behaviors that could predispose one sex to predation, but males were less wary than females in response to a potentially frightening stimulus.
The negative impacts of herbivore consumption on plants are well known, but impacts on ecosystem processes are not. Herbivores can alter soil nutrient availability through herbivory and waste deposition. If predators significantly reduce herbivory, they may impact some soil ecosystem processes. Gray wolves may regulate white-tailed deer herbivory in Great Lakes forests, and this may impact soil nitrogen availability. Deer exclosure/control plots in high- and low-wolf use forest patches were employed to determine whether wolves and/or deer affect nitrogen availability. Despite evidence for deer affecting soil nitrogen availability in other forests and wolves affecting it in grasslands, we found no such effects in this forest. Given the context dependence of top-down impacts on nutrient dynamics, we encourage further inquiry.
Sex ratios of rodents in samples of owl pellets have been interpreted to reflect predator selectivity, availability of prey on the landscape, and variable susceptibility of the sexes to predation. Metric distinction of male from female innominates of deer mice (Peromyscus maniculatus) and voles (Microtus spp.) extracted from ∼120 pellets cast by barn owls (Tyto alba) in southeastern Washington state revealed more females than males. The sex ratio did not change from pellets cast when much of the landscape was productive agricultural land to pellets cast when a portion of the land was taken out of production and placed in soil bank. Barn owls are opportunistic foragers that have greater success at prey capture when vegetation cover is discontinuous. Barn owls likely captured more young females than males of both rodent taxa because the former are more subject than the latter to intra- and inter-specific displacement into more open habitats, whether agricultural land or soil bank land, therefore are more susceptible to predation.
Intersex condition (ooctyes in testicular tissue) has been documented in many watersheds among a diverse variety of fishes worldwide. However, few studies have tested for the occurrence of the condition in fishes from rivers of the American Midwest. Midwestern watersheds, such as the Illinois River Waterway, U.S.A. may provide important new information about the effects of endocrine disrupting chemicals (EDCs) on fishes because of the variety of urban, industrial, and agricultural land uses within the watersheds. A first step in the study of EDCs in any ecosystem is a survey to document the symptoms of EDC exposure, such as intersex condition. Our objective was to test for intersex condition in male largemouth bass Micropterus salmoides in the lower Des Plaines River, an area directly affected by surface runoff and wastewater effluents from the Chicago Metropolitan Area. Histological analysis indicated that testicular oocytes were present in 21 of 51 (41%) largemouth bass sampled and oocyte numbers ranged from 1–25/thin section among intersex individuals. Our study details the severity of intersex in a population of largemouth bass near a major metropolitan area, which represents an important contribution to the understanding of fish reproductive ecology in ecosystems with a history of environmental disturbance and recovery such as the Illinois River Waterway.
Egg and nest crypsis is a strategy to reduce detection by predators, thereby minimizing offspring mortality. While this strategy has been well studied in birds, it has received little attention in other taxa. Turtles are plausibly able to camouflage their subterranean nests by reducing the level of soil surface disturbance. To test the hypothesis that more cryptic nests experience lower predation, we first quantified the camouflage of natural Painted Turtle (Chrysemys picta) nests from the human perspective and demonstrated that substantial variation in nest camouflage exists. We subsequently tracked the predation fates of these nests and related nest camouflage to nest survival. Although the results trend in the expected direction, logistic regression did not yield a significant association between camouflage rating and nest survival. These results suggest turtle nests are highly detectable by predators and mothers have little ability to influence predation risk to their nests via camouflage. This work opens a previously little-explored area in nest crypsis in which further study could aid in discerning a functional connection between turtle nest camouflage and survival.