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At least 1,153 records · Page 64Linked to original sources
USGS2010

Occupancy dynamics in a tropical bird community: Unexpectedly high forest use by birds classified as non‐forest species

1. Worldwide loss of biodiversity necessitates a clear understanding of the factors driving population declines as well as informed predictions about which species and populations are at greatest risk. The biggest threat to the long-term persistence of populations is the reduction and changes in configuration of their natural habitat. 2. Inconsistencies have been noted in the responses of populations to the combined effects of habitat loss and fragmentation. These have been widely attributed to the effects of the matrix habitats in which remnant focal habitats are typically embedded. 3. We quantified the potential effects of the inter-patch matrix by estimating occupancy and colonization of forest and surrounding non-forest matrix (NF). We estimated species-specific parameters using a dynamic, multi-species hierarchical model on a bird community in southwestern Costa Rica. 4. Overall, we found higher probabilities of occupancy and colonization of forest relative to the NF across bird species, including those previously categorized as open habitat generalists not needing forest to persist. Forest dependency was a poor predictor of occupancy dynamics in our study region, largely predicting occupancy and colonization of only non-forest habitats. 5. Our results indicate that the protection of remnant forest habitats is key for the long-term persistence of all members of the bird community in this fragmented landscape, including species typically associated with open, non-forest habitats. 6. Synthesis and applications. We identified 39 bird species of conservation concern defined by having high estimates of forest occupancy, and low estimates of occupancy and colonization of non-forest. These species survive in forest but are unlikely to venture out into open, non-forested habitats, therefore, they are vulnerable to the effects of habitat loss and fragmentation. Our hierarchical community-level model can be used to estimate species-specific occupancy dynamics for focal and inter-patch matrix habitats to identify which species within a community are likely to be impacted most by habitat loss and fragmentation. This model can be applied to other taxa (i.e. amphibians, mammals and insects) to estimate species and community occurrence dynamics in response to current environmental conditions and to make predictions in response to future changes in habitat configurations.

Journal of Applied Ecology↗
USGS2010

Modelling community dynamics based on species-level abundance models from detection/nondetection data

1. In large‐scale field surveys, a binary recording of each species’ detection or nondetection has been increasingly adopted for its simplicity and low cost. Because of the importance of abundance in many studies, it is desirable to obtain inferences about abundance at species‐, functional group‐, and community‐levels from such binary data. 2. We developed a novel hierarchical multi‐species abundance model based on species‐level detection/nondetection data. The model accounts for the existence of undetected species, and variability in abundance and detectability among species. Species‐level detection/nondetection is linked to species‐level abundance via a detection model that accommodates the expectation that probability of detection (at least one individuals is detected) increases with local abundance of the species. We applied this model to a 9‐year dataset composed of the detection/nondetection of forest birds, at a single post‐fire site (from 7 to 15 years after fire) in a montane area of central Japan. The model allocated undetected species into one of the predefined functional groups by assuming a prior distribution on individual group membership. 3. The results suggest that 15–20 species were missed in each year, and that species richness of communities and functional groups did not change with post‐fire forest succession. Overall abundance of birds and abundance of functional groups tended to increase over time, although only in the winter, while decreases in detectabilities were observed in several species. 4. Synthesis and applications . Understanding and prediction of large‐scale biodiversity dynamics partly hinge on how we can use data effectively. Our hierarchical model for detection/nondetection data estimates abundance in space/time at species‐, functional group‐, and community‐levels while accounting for undetected individuals and species. It also permits comparison of multiple communities by many types of abundance‐based diversity and similarity measures under imperfect detection.

Journal of Applied Ecology↗
USGS2011

Engineering a future for amphibians under climate change

1. Altered global climates in the 21st century pose serious threats for biological systems and practical actions are needed to mount a response for species at risk. 2. We identify management actions from across the world and from diverse disciplines that are applicable to minimizing loss of amphibian biodiversity under climate change. Actions were grouped under three thematic areas of intervention: (i) installation of microclimate and microhabitat refuges; (ii) enhancement and restoration of breeding sites; and (iii) manipulation of hydroperiod or water levels at breeding sites. 3. Synthesis and applications. There are currently few meaningful management actions that will tangibly impact the pervasive threat of climate change on amphibians. A host of potentially useful but poorly tested actions could be incorporated into local or regional management plans, programmes and activities for amphibians. Examples include: installation of irrigation sprayers to manipulate water potentials at breeding sites; retention or supplementation of natural and artificial shelters (e.g. logs, cover boards) to reduce desiccation and thermal stress; manipulation of canopy cover over ponds to reduce water temperature; and, creation of hydrologoically diverse wetland habitats capable of supporting larval development under variable rainfall regimes. We encourage researchers and managers to design, test and scale up new initiatives to respond to this emerging crisis.

Journal of Applied Ecology↗
USGS2011

The human dimension of fire regimes on Earth

Humans and their ancestors are unique in being a fire‐making species, but ‘natural’ (i.e. independent of humans) fires have an ancient, geological history on Earth. Natural fires have influenced biological evolution and global biogeochemical cycles, making fire integral to the functioning of some biomes. Globally, debate rages about the impact on ecosystems of prehistoric human‐set fires, with views ranging from catastrophic to negligible. Understanding of the diversity of human fire regimes on Earth in the past, present and future remains rudimentary. It remains uncertain how humans have caused a departure from ‘natural’ background levels that vary with climate change. Available evidence shows that modern humans can increase or decrease background levels of natural fire activity by clearing forests, promoting grazing, dispersing plants, altering ignition patterns and actively suppressing fires, thereby causing substantial ecosystem changes and loss of biodiversity. Some of these contemporary fire regimes cause substantial economic disruptions owing to the destruction of infrastructure, degradation of ecosystem services, loss of life, and smoke‐related health effects. These episodic disasters help frame negative public attitudes towards landscape fires, despite the need for burning to sustain some ecosystems. Greenhouse gas‐induced warming and changes in the hydrological cycle may increase the occurrence of large, severe fires, with potentially significant feedbacks to the Earth system. Improved understanding of human fire regimes demands: (1) better data on past and current human influences on fire regimes to enable global comparative analyses, (2) a greater understanding of different cultural traditions of landscape burning and their positive and negative social, economic and ecological effects, and (3) more realistic representations of anthropogenic fire in global vegetation and climate change models. We provide an historical framework to promote understanding of the development and diversification of fire regimes, covering the pre‐human period, human domestication of fire, and the subsequent transition from subsistence agriculture to industrial economies. All of these phases still occur on Earth, providing opportunities for comparative research.

Journal of Biogeography↗
USGS2006

Understanding the genetic effects of recent habitat fragmentation in the context of evolutionary history: Phylogeography and landscape genetics of a southern California endemic Jerusalem cricket (Orthoptera: Stenopelmatidae: Stenopelmatus)

Habitat loss and fragmentation due to urbanization are the most pervasive threats to biodiversity in southern California. Loss of habitat and fragmentation can lower migration rates and genetic connectivity among remaining populations of native species, reducing genetic variability and increasing extinction risk. However, it may be difficult to separate the effects of recent anthropogenic fragmentation from the genetic signature of prehistoric fragmentation due to previous natural geological and climatic changes. To address these challenges, we examined the phylogenetic and population genetic structure of a flightless insect endemic to cismontane southern California, Stenopelmatus 'mahogani' (Orthoptera: Stenopelmatidae). Analyses of mitochondrial DNA sequence data suggest that diversification across southern California began during the Pleistocene, with most haplotypes currently restricted to a single population. Patterns of genetic divergence correlate with contemporary urbanization, even after correcting for (geographical information system) GIS-based reconstructions of fragmentation during the Pleistocene. Theoretical simulations confirm that contemporary patterns of genetic structure could be produced by recent urban fragmentation using biologically reasonable assumptions about model parameters. Diversity within populations was positively correlated with current fragment size, but not prehistoric fragment size, suggesting that the effects of increased drift following anthropogenic fragmentation are already being seen. Loss of genetic connectivity and diversity can hinder a population's ability to adapt to ecological perturbations commonly associated with urbanization, such as habitat degradation, climatic changes and introduced species. Consequently, our results underscore the importance of preserving and restoring landscape connectivity for long-term persistence of low vagility native species. Journal compilation ?? 2006 Blackwell Publishing Ltd.

Molecular Ecology↗
USGS2011

Mixed-source reintroductions lead to outbreeding depression in second-generation descendents of a native North American fish

Reintroductions are commonly employed to preserve intraspecific biodiversity in fragmented landscapes. However, reintroduced populations are frequently smaller and more geographically isolated than native populations. Mixing genetically, divergent sources are often proposed to attenuate potentially low genetic diversity in reintroduced populations that may result from small effective population sizes. However, a possible negative tradeoff for mixing sources is outbreeding depression in hybrid offspring. We examined the consequences of mixed‐source reintroductions on several fitness surrogates at nine slimy sculpin ( Cottus cognatus ) reintroduction sites in south‐east Minnesota. We inferred the relative fitness of each crosstype in the reintroduced populations by comparing their growth rate, length, weight, body condition and persistence in reintroduced populations. Pure strain descendents from a single source population persisted in a greater proportion than expected in the reintroduced populations, whereas all other crosstypes occurred in a lesser proportion. Length, weight and growth rate were lower for second‐generation intra‐population hybrid descendents than for pure strain and first‐generation hybrids. In the predominant pure strain, young‐of the‐year size was significantly greater than any other crosstype. Our results suggested that differences in fitness surrogates among crosstypes were consistent with disrupted co‐adapted gene complexes associated with beneficial adaptations in these reintroduced populations. Future reintroductions may be improved by evaluating the potential for local adaptation in source populations or by avoiding the use of mixed sources by default when information on local adaptations or other genetic characteristics is lacking.

Molecular Ecology↗
USGS2006

Filling in the gaps: Modelling native species richness and invasions using spatially incomplete data

Detailed knowledge of patterns of native species richness, an important component of biodiversity, and non-native species invasions is often lacking even though this knowledge is essential to conservation efforts. However, we cannot afford to wait for complete information on the distribution and abundance of native and harmful invasive species. Using information from counties well surveyed for plants across the USA, we developed models to fill data gaps in poorly surveyed areas by estimating the density (number of species km -2) of native and non-native plant species. Here, we show that native plant species density is non-random, predictable, and is the best predictor of non-native plant species density. We found that eastern agricultural sites and coastal areas are among the most invaded in terms of non-native plant species densities, and that the central USA appears to have the greatest ratio of non-native to native species. These large-scale models could also be applied to smaller spatial scales or other taxa to set priorities for conservation and invasion mitigation, prevention, and control efforts. ?? 2006 The Authors.

Diversity and Distributions↗
USGS2010

Fishing out marine parasites? Impacts of fishing on rates of parasitism in the ocean

Among anthropogenic effects on the ocean, fishing is one of the most pervasive and extends deepest into the past. Because fishing reduces the density of fish (reducing transmission efficiency of directly transmitted parasites), selectively removes large fish (which tend to carry more parasites than small fish), and reduces food web complexity (reducing transmission efficiency of trophically transmitted parasites), the removal of fish from the world’s oceans over the course of hundreds of years may be driving a long-term, global decline in fish parasites. There has been growing recognition in recent years that parasites are a critical part of biodiversity and that their loss could substantially alter ecosystem function. Such a loss may be among the last major ecological effects of industrial fishing to be recognized by scientists.

Ecology Letters↗
USGS2011

Abundance of introduced species at home predicts abundance away in herbaceous communities

Many ecosystems worldwide are dominated by introduced plant species, leading to loss of biodiversity and ecosystem function. A common but rarely tested assumption is that these plants are more abundant in introduced vs. native communities, because ecological or evolutionary-based shifts in populations underlie invasion success. Here, data for 26 herbaceous species at 39 sites, within eight countries, revealed that species abundances were similar at native (home) and introduced (away) sites - grass species were generally abundant home and away, while forbs were low in abundance, but more abundant at home. Sites with six or more of these species had similar community abundance hierarchies, suggesting that suites of introduced species are assembling similarly on different continents. Overall, we found that substantial changes to populations are not necessarily a pre-condition for invasion success and that increases in species abundance are unusual. Instead, abundance at home predicts abundance away, a potentially useful additional criterion for biosecurity programmes.

Ecology Letters↗
USGS2011

Forest species diversity reduces disease risk in a generalist plant pathogen invasion

Empirical evidence suggests that biodiversity loss can increase disease transmission, yet our understanding of the 'diversity-disease hypothesis' for generalist pathogens in natural ecosystems is limited. We used a landscape epidemiological approach to examine two scenarios regarding diversity effects on the emerging plant pathogen Phytophthora ramorum across a broad, heterogeneous ecoregion: (1) an amplification effect exists where disease risk is greater in areas with higher plant diversity due to the pathogen's wide host range, or (2) a dilution effect where risk is reduced with increasing diversity due to lower competency of alternative hosts. We found evidence for pathogen dilution, whereby disease risk was lower in sites with higher species diversity, after accounting for potentially confounding effects of host density and landscape heterogeneity. Our results suggest that although nearly all plants in the ecosystem are hosts, alternative hosts may dilute disease transmission by competent hosts, thereby buffering forest health from infectious disease.

Ecology Letters↗
USGS2012

Latitudinal species diversity gradient of marine zooplankton for the last three million years

High tropical and low polar biodiversity is one of the most fundamental patterns characterising marine ecosystems, and the influence of temperature on such marine latitudinal diversity gradients is increasingly well documented. However, the temporal stability of quantitative relationships among diversity, latitude and temperature is largely unknown. Herein we document marine zooplankton species diversity patterns at four time slices [modern, Last Glacial Maximum (18 000 years ago), last interglacial (120 000 years ago), and Pliocene (~3.3–3.0 million years ago)] and show that, although the diversity-latitude relationship has been dynamic, diversity-temperature relationships are remarkably constant over the past three million years. These results suggest that species diversity is rapidly reorganised as species' ranges respond to temperature change on ecological time scales, and that the ecological impact of future human-induced temperature change may be partly predictable from fossil and paleoclimatological records.

Ecology Letters↗
USGS2018

Natural history museums and cyberspace

‘The museums have been reincarnated in electronic form.’ So say three experts from the Smithsonian Institution, who describe how the latest technologies are plunging the museum straight into the heart of the battle to safeguard biodiversity.

Museum International↗
USGS2012

Influence of space use on fitness and the reintroduction success of the Laysan teal

Translocation is an important tool for wildlife conservation and biodiversity restoration, but an inefficient one because of the unpredictability of success. Predictors of success such as habitat quality of the release site and number of individuals released have been identified, but the dynamics of successful translocations remain poorly understood. In particular, little is known about the relationship of individual post-release movements to population establishment. In 2004, Laysan teal Anas laysanensis were reintroduced by translocating 20 wild birds from Laysan Island to Midway Atoll. Twenty-two additional wild founders were brought the next year. We monitored the survival, reproductive success and movements of the 42 translocated individuals and their offspring for 4 years. Additionally, we monitored population size from 2004 to 2010. Unlike most translocations, we did not observe elevated post-release mortality despite flight-feather trimming to prevent immediate dispersal off-island: first year survival was > 90% and survival rates until 2009 were 0.65±0.08 for founding adults. Laysan teal flew between the two main islands of Midway Atoll, and offspring had significantly larger maximum movement distances than founders. We monitored 84 nests and observed a significant, negative relationship of home range size to productivity for founding females. Flightless founders did not show fidelity to their release sites, but had strong fidelity to annual home ranges after attaining flight. Although we observed a component Allee effect on mate-finding, this did not translate into a demographic Allee effect, and generally, the high fitness of founders contributed substantially to successful population establishment. Laysan teal abundance increased linearly until 2009, but showed evidence of population regulation afterwards. The population estimate was 473 (95% confidence interval 439–508) in 2010. On the much larger main Hawaiian Islands, we expect greater post-release movement, a stronger component Allee effect, lower survival and lower reproductive rates because of predation to preclude successful reintroductions of this species to sites without predator management.

Laysan Island;Midway Atoll↗
USGS2009

Fungal endophytes: diversity and functional roles

All plants in natural ecosystems appear to be symbiotic with fungal endophytes. This highly diverse group of fungi can have profound impacts on plant communities through increasing fitness by conferring abiotic and biotic stress tolerance, increasing biomass and decreasing water consumption, or decreasing fitness by altering resource allocation. Despite more than 100 yr of research resulting in thousands of journal articles, the ecological significance of these fungi remains poorly characterized. Historically, two endophytic groups (clavicipitaceous (C) and nonclavicipitaceous (NC)) have been discriminated based on phylogeny and life history traits. Here, we show that NC-endophytes represent three distinct functional groups based on host colonization and transmission, in planta biodiversity and fitness benefits conferred to hosts. Using this framework, we contrast the life histories, interactions with hosts and potential roles in plant ecophysiology of C- and NC-endophytes, and highlight several key questions for future work in endophyte biology.

New Phytologist↗
USGS2009

Taxonomy of quaternary deep-sea ostracods from the Western North Atlantic ocean

Late Quaternary sediments from Ocean Drilling Program (ODP) Hole 1055B, Carolina Slope, western North Atlantic (32??47.041??? N, 76??17.179??? W; 1798m water depth) were examined for deep-sea ostracod taxonomy. A total of 13933 specimens were picked from 207 samples and c. 120 species were identified. Among them, 87 species were included and illustrated in this paper. Twenty-eight new species are described. The new species are: Ambocythere sturgio, Argilloecia abba, Argilloecia caju, Argilloecia keigwini, Argilloecia robinwhatleyi, Aversovalva carolinensis, Bythoceratina willemvandenboldi, Bythocythere eugeneschornikovi, Chejudocythere tenuis, Cytheropteron aielloi, Cytheropteron demenocali, Cytheropteron didieae, Cytheropteron richarddinglei, Cytheropteron fugu, Cytheropteron guerneti, Cytheropteron richardbensoni, Eucytherura hazeli, Eucytherura mayressi, Eucytherura namericana, Eucytherura spinicorona, Posacythere hunti, Paracytherois bondi, Pedicythere atroposopetasi, Pedicythere kennettopetasi, Pedicythere klothopetasi, Pedicythere lachesisopetasi, Ruggieriella mcmanusi and Xestoleberis oppoae. Taxonomic revisions of several common species were made to reduce taxonomic uncertainty in the literature. This study provides a robust taxonomic baseline for application to palaeoceanographical reconstruction and biodiversity analyses in the deep and intermediate-depth environments of the North Atlantic Ocean. ?? The Palaeontological Association, 2009.

Palaeontology↗
USGS2006

Evidence for the role of infectious disease in species extinction and endangerment

Infectious disease is listed among the top five causes of global species extinctions. However, the majority of available data supporting this contention is largely anecdotal. We used the IUCN Red List of Threatened and Endangered Species and literature indexed in the ISI Web of Science to assess the role of infectious disease in global species loss. Infectious disease was listed as a contributing factor in <4% of species extinctions known to have occurred since 1500 (833 plants and animals) and as contributing to a species' status as critically endangered in <8% of cases (2852 critically endangered plants and animals). Although infectious diseases appear to play a minor role in global species loss, our findings underscore two important limitations in the available evidence: uncertainty surrounding the threats to species survival and a temporal bias in the data. Several initiatives could help overcome these obstacles, including rigorous scientific tests to determine which infectious diseases present a significant threat at the species level, recognition of the limitations associated with the lack of baseline data for the role of infectious disease in species extinctions, combining data with theory to discern the circumstances under which infectious disease is most likely to serve as an agent of extinction, and improving surveillance programs for the detection of infectious disease. An evidence-based understanding of the role of infectious disease in species extinction and endangerment will help prioritize conservation initiatives and protect global biodiversity.

Conservation Biology↗
USGS2010

Ants as a measure of effectiveness of habitat conservation planning in southern California

In the United States multispecies habitat conservation plans were meant to be the solution to conflicts between economic development and protection of biological diversity. Although now widely applied, questions exist concerning the scientific credibility of the conservation planning process and effectiveness of the plans. We used ants to assess performance of one of the first regional conservation plans developed in the United States, the Orange County Central‐Coastal Natural Community Conservation Plan (NCCP), in meeting its broader conservation objectives of biodiversity and ecosystem‐level protection. We collected pitfall data on ants for over 3 years on 172 sites established across a network of conservation lands in coastal southern California. Although recovered native ant diversity for the study area was high, site‐occupancy models indicated the invasive and ecologically disruptive Argentine ant ( Linepithema humile ) was present at 29% of sites, and sites located within 200 m of urban and agricultural areas were more likely to have been invaded. Within invaded sites, native ants were largely displaced, and their median species richness declined by more than 60% compared with uninvaded sites. At the time of planning, 24% of the 15,133‐ha reserve system established by Orange County NCCP fell within 200 m of an urban or agricultural edge. With complete build out of lands surrounding the reserve, the proportion of the reserve system vulnerable to invasion will grow to 44%. Our data indicate that simply protecting designated areas from development is not enough. If habitat conservation plans are to fulfill their conservation promise of ecosystem‐level protection, a more‐integrated and systematic approach to the process of habitat conservation planning is needed .

California↗
USGS2012

Diet of non-native northern snakehead ( Channa argus ) compared to three co-occurring predators in the lower Potomac River, USA

Introductions of large, non-native, carnivorous fishes continue to occur worldwide and represent a substantial management concern to global biodiversity. One of the most recent non-native fishes to successfully establish in North America is the northern snakehead ( Channa argus ), found in the lower Potomac River catchment. Dispersal of the northern snakehead throughout this system has been well documented since its original discovery in May 2004; however, little is known about the foraging habits of this species and its interactions with co-occurring predators. Here, we quantify northern snakehead diet in comparison with the diets of naturalised largemouth bass ( Micropterus salmoides ), and native American eel ( Anguilla rostrata ) and yellow perch ( Perca flavescens ) collected from tidal freshwaters bordering Virginia and Maryland near Fort Belvoir, Virginia. Over 97% of northern snakehead gut contents were fishes, with fundulid and centrarchid species consumed most frequently. Dietary overlap was biologically significant only between northern snakehead and largemouth bass. Aquatic invertebrates were >10 times more common in native predator diets, reducing dietary overlap with northern snakehead. Ontogenic shifts in adult northern snakehead diet were also detected, which may be explained by optimal foraging rather than true prey specificity. Northern snakehead may be occupying a novel niche based on a piscivorous diet, therefore limiting competition with resident predators in the lower Potomac River. Further research into interactions between largemouth bass and northern snakehead is needed to inform management decisions and understand the ecological impacts of this non-native species.

Maryland, Virginia↗