scholarly journals Drivers of Avian Diversity and Abundance Across Gradients of Human Influence.

2021 ◽  
Author(s):  
Benjamin J. Padilla ◽  
Chris Sutherland
Keyword(s):  
Landscape Heterogeneity ◽  
Species Abundance ◽  
Habitat Modification ◽  
Individual Species ◽  
Avian Diversity ◽  
Human Influence ◽  
Sensitive Species ◽  
Landscape Modification ◽  
Driving Patterns ◽  
Abundance And Diversity

Abstract Context: Identifying factors driving patterns of species communities in heterogenous human-dominated landscapes remains elusive despite extensive research. Biodiversity is thought to decrease with habitat modification, as sensitive species are lost. Conversely, diversity has also been shown increase at moderate levels of landscape modification where greater habitat heterogeneity supports a diverse suite of species.Objectives: We explore patterns of avian and diversity and abundance in heterogenous landscapes using a novel integration of multiple dimensional gradients of human-mediated disturbance.Methods: We attempt to identify aspects of landscape heterogeneity driving patterns of avian diversity and abundance in agro-urban-rural systems. Specifically, we utilize an intuitive multi-dimensional gradient distinguishing between two axes of human-influence, variation in the built environment (hard - soft) and in agricultural development (green - brown). We use these as covariates in community N-mixture models to describe variation in species abundance and diversity.Results: Avian diversity was greatest in more heterogeneous regions of the landscape. Responses of individual species were variable, with sensitive species declining, while generalist species increased, leading to higher overall diversity in human-dominated regions. Conclusions: Species abundance and diversity is maximized in more heterogeneous parts of landscape mosaics. By characterizing distinct axes of human influence that capture spectrum of land use, we can identify differential effects confounded in traditional landscape metrics. Critically, we demonstrate that multi-dimensional landscape gradients provide a more nuanced understanding of how patterns of biodiversity emerge. Acknowledging that biodiversity is not always negatively impacted by habitat disturbance offers encouraging insight to guide conservation and management in human-dominated landscapes.

Patterns in diversity and composition of the microbenthos of subarctic intertidal beaches with different morphodynamics

2020 ◽  
Vol 648 ◽  
pp. 19-38
Author(s):  
AI Azovsky ◽  
YA Mazei ◽  
MA Saburova ◽  
PV Sapozhnikov
Keyword(s):  
Species Abundance ◽  
Abundance Ratio ◽  
Wave Action ◽  
Coarse Grained ◽  
Sediment Properties ◽  
Β Diversity ◽  
Α Diversity ◽  
Wide Range ◽  
Similar Mode ◽  
Abundance And Diversity

Diversity and composition of benthic diatom algae and ciliates were studied at several beaches along the White and Barents seas: from highly exposed, reflective beaches with coarse-grained sands to sheltered, dissipative silty-sandy flats. For diatoms, the epipelic to epipsammic species abundance ratio was significantly correlated with the beach index and mean particle size, while neither α-diversity measures nor mean cell length were related to beach properties. In contrast, most of the characteristics of ciliate assemblages (diversity, total abundance and biomass, mean individual weight and percentage of karyorelictids) demonstrated a strong correlation to beach properties, remaining low at exposed beaches but increasing sharply in more sheltered conditions. β-diversity did not correlate with beach properties for either diatoms or ciliates. We suggest that wave action and sediment properties are the main drivers controlling the diversity and composition of the intertidal microbenthos. Diatoms and ciliates, however, demonstrated divergent response to these factors. Epipelic and epipsammic diatoms exhibited 2 different strategies to adapt to their environments and therefore were complementarily distributed along the environmental gradient and compensated for each other in diversity. Most ciliates demonstrated a similar mode of habitat selection but differed in their degree of tolerance. Euryporal (including mesoporal) species were relatively tolerant to wave action and therefore occurred under a wide range of beach conditions, though their abundance and diversity were highest in fine, relatively stable sediments on sheltered beaches, whereas the specific interstitial (i.e. genuine microporal) species were mostly restricted to only these habitats.

Fire regimes and vegetation sensitivity analysis: an example from Bradshaw Station, monsoonal northern Australia

2003 ◽  
Vol 12 (4) ◽  
pp. 349 ◽  
Author(s):  
Cameron Yates ◽  
Jeremy Russell-Smith
Keyword(s):  
Fire History ◽  
Fire Regime ◽  
Landscape Scale ◽  
Fire Season ◽  
Individual Species ◽  
Northern Australia ◽  
Sensitive Species ◽  
Obligate Seeder ◽  
Return Interval ◽  
Noaa Avhrr

The fire-prone savannas of northern Australia comprise a matrix of mostly fire-resilient vegetation types, with embedded fire-sensitive species and communities particularly in rugged sandstone habitats. This paper addresses the assessment of fire-sensitivity at the landscape scale, drawing on detailed fire history and vegetation data assembled for one large property of 9100�km2, Bradshaw Station in the Top End of the Northern Territory, Australia. We describe (1) the contemporary fire regime for Bradshaw Station for a 10 year period; (2) the distribution and status of 'fire sensitive' vegetation; and (3) an assessment of fire-sensitivity at the landscape scale. Fire-sensitive species (FSS) were defined as obligate seeder species with minimum maturation periods of at least 3 years. The recent fire history for Bradshaw Station was derived from the interpretation of fine resolution Landsat MSS and Landsat TM imagery, supplemented with mapping from coarse resolution NOAA-AVHRR imagery where cloud had obstructed the use of Landsat images late in the fire season (typically October–November). Validation assessments of fire mapping accuracy were conducted in 1998 and 1999. On average 40% of Bradshaw burnt annually with about half of this, 22%, occurring after August (Late Dry Season LDS), and 65% of the property burnt 4 or more times, over the 10 year period; 89% of Bradshaw Station had a minimum fire return interval of less than 3 years in the study period. The derived fire seasonality, frequency and return interval data were assessed with respect to landscape units (landsystems). The largest landsystem, Pinkerton (51%, mostly sandstone) was burnt 41% on average, with about 70% burnt four times or more, over the 10 year period. Assessment of the fire-sensitivity of individual species was undertaken with reference to data assembled for 345 vegetation plots, herbarium records, and an aerial survey of the distribution of the long-lived obligate-seeder tree species Callitris intratropica. A unique list of 1310 plant species was attributed with regenerative characteristics (i.e. habit, perenniality, resprouting capability, time to seed maturation). The great majority of FSS species were restricted to rugged sandstone landforms. The approach has wider application for assessing landscape fire-sensitivity and associated landscape health in savanna landscapes in northern Australia, and elsewhere.

scholarly journals How, when, and where relic DNA biases estimates of microbial diversity

2017 ◽  
Author(s):  
JT Lennon ◽  
ME Muscarella ◽  
SA Muscarella ◽  
BK Lehmkuhl
Keyword(s):  
Microbial Diversity ◽  
Dna Sequences ◽  
Species Abundance ◽  
Rrna Gene ◽  
Bacterial Dna ◽  
Soil Sediment ◽  
Species Abundance Distributions ◽  
Abundance And Diversity ◽  
Dna Pool ◽  
Biased Estimates

Extracellular or “relic” DNA is one of the largest pools of nucleic acids in the mbiosphere1,2. Relic DNA can influence a number of important ecological and evolutionary processes, but it may also bias estimates of microbial abundance and diversity, which has implications for understanding environmental, engineered, and host-associated ecosystems. We developed models capturing the fundamental processes that regulate the size and composition of the relic DNA pools to identify scenarios leading to biased estimates of biodiversity. Our models predict that bias increases with relic DNA pool size, but only when the species abundance distributions (SAD) of relic and intact DNA are distinct from one another. We evaluated our model predictions by quantifying relic DNA and assessing its contribution to bacterial diversity using 16S rRNA gene sequences collected from different ecosystem types, including soil, sediment, water, and the mammalian gut. On average, relic DNA made up 33 % of the total bacterial DNA pool, but exceeded 80 % in some samples. Despite its abundance, relic DNA had no effect on estimates of taxonomic and phylogenetic diversity, even in ecosystems where processes such as the physical protection of relic DNA are common and predicted by our models to generate bias. Rather, our findings are consistent with the expectation that relic DNA sequences degrade in proportion to their abundance and therefore may contribute minimally to estimates of microbial diversity.

scholarly journals Decline in New Zealand's freshwater fish fauna: Effect of land use

2020 ◽  
Author(s):  
Michael Joy ◽  
KJ Foote ◽  
P McNie ◽  
M Piria
Keyword(s):  
New Zealand ◽  
Land Cover ◽  
Freshwater Fish ◽  
Native Species ◽  
Species Abundance ◽  
Fish Fauna ◽  
Fish Distribution ◽  
Individual Species ◽  
Freshwater Fish Fauna ◽  
Over Time

© 2019 CSIRO. The number of New Zealand's freshwater fish listed as threatened has increased since 1992 when the first New Zealand threat classification system list was compiled. In this study, temporal and land cover-related trends were analysed for data on freshwater fish distribution, comprising more than 20 000 records for the 47 years from January 1970 to January 2017 from the New Zealand Freshwater Fish Database. The analysis included individual species abundance and distribution trends, as well as an index of fish community integrity, namely the Index of Biotic Integrity (IBI). Of the 25 fish species that met the requirements for analysis to determine changes in the proportion of sites they occupied over time, 76% had negative trends (indicating declining occurrence). Of the 20 native species analysed for the proportion of sites occupied over time, 75% had negative trends; 65% of these were significant declines and more species were in decline at pasture sites than natural cover sites. The average IBI score also declined over the time period and, when analysed separately, the major land cover types revealed that the IBI declined at pasture catchment sites but not at sites with natural vegetation catchments.

scholarly journals Estimation of the relative abundance of species in artificial mixtures of insects using low-coverage shotgun metagenomics

2020 ◽  
Vol 4 ◽  
Author(s):  
Lidia Garrido-Sanz ◽  
Miquel Àngel Senar ◽  
Josep Piñol
Keyword(s):  
Relative Abundance ◽  
Species Abundance ◽  
Single Species ◽  
Insect Species ◽  
Individual Species ◽  
Advanced Degree ◽  
Mixed Species ◽  
Species List ◽  
Shotgun Metagenomics ◽  
Low Coverage

Amplicon metabarcoding is an established technique to analyse the taxonomic composition of communities of organisms using high-throughput DNA sequencing, but there are doubts about its ability to quantify the relative proportions of the species, as opposed to the species list. Here, we bypass the enrichment step and avoid the PCR-bias, by directly sequencing the extracted DNA using shotgun metagenomics. This approach is common practice in prokaryotes, but not in eukaryotes, because of the low number of sequenced genomes of eukaryotic species. We tested the metagenomics approach using insect species whose genome is already sequenced and assembled to an advanced degree. We shotgun-sequenced, at low-coverage, 18 species of insects in 22 single-species and 6 mixed-species libraries and mapped the reads against 110 reference genomes of insects. We used the single-species libraries to calibrate the process of assignation of reads to species and the libraries created from species mixtures to evaluate the ability of the method to quantify the relative species abundance. Our results showed that the shotgun metagenomic method is easily able to set apart closely-related insect species, like four species of Drosophila included in the artificial libraries. However, to avoid the counting of rare misclassified reads in samples, it was necessary to use a rather stringent detection limit of 0.001, so species with a lower relative abundance are ignored. We also identified that approximately half the raw reads were informative for taxonomic purposes. Finally, using the mixed-species libraries, we showed that it was feasible to quantify with confidence the relative abundance of individual species in the mixtures.

Community Ecology

Ecology ◽  
2012 ◽  
Author(s):  
Herman A. Verhoef
Keyword(s):  
Community Ecology ◽  
Evolutionary Biology ◽  
Environmental Gradients ◽  
Functional Integration ◽  
Species Abundance ◽  
Functional Trait ◽  
Individual Species ◽  
Global Changes ◽  
Ecological Communities ◽  
Early 21St Century

At the beginning of the 20th century there was much debate about the “nature” of communities. The driving question was whether the community was a self-organized system of co-occurring species or simply a haphazard collection of populations with minimal functional integration. At that time, two extreme views dominated the discussion: one view considered a community as a superorganism, the member species of which were tightly bound together by interactions that contributed to repeatable patterns of species abundance in space and time. This concept led to the assumption that communities are fundamental entities, to be classified as the Linnaean taxonomy of species. Frederick E. Clements was one of the leading proponents of this approach, and his view became known as the organismic concept of communities. This assumes a common evolutionary history for the integrated species. The opposite view was the individualistic continuum concept, advocated by H. A. Gleason. His focus was on the traits of individual species that allow each to live within specific habitats or geographical ranges. In this view a community is an assemblage of populations of different species whose traits allow persisting in a prescribed area. The spatial boundaries are not sharp, and the species composition can change considerably. Consequently, it was discussed whether ecological communities were sufficiently coherent entities to be considered appropriate study objects. Later, consensus was reached: that properties of communities are of central interest in ecology, regardless of their integrity and coherence. From the 1950s and 1960s onward, the discussion was dominated by the deterministic outcome of local interactions between species and their environments and the building of this into models of communities. This approach, indicated as “traditional community ecology,” led to a morass of theoretical models, without being able to provide general principles about many-species communities. Early-21st-century approaches to bringing general patterns into community ecology concern (1) the metacommunity approach, (2) the functional trait approach, (3) evolutionary community ecology, and (4) the four fundamental processes. The metacommunity approach implicitly recognizes and studies the important role of spatiotemporal dynamics. In the functional trait approach, four themes are focused upon: traits, environmental gradients, the interaction milieu, and performance currencies. This functional, trait-focused approach should have a better prospect of understanding the effects of global changes. Evolutionary community ecology is an approach in which the combination of community ecology and evolutionary biology will lead to a better understanding of the complexity of communities and populations. The four fundamental processes are selection, drift, speciation, and dispersal. This approach concerns an organizational scheme for community ecology, based on these four processes to describe all existing specific models and frameworks, in order to make general statements about process–pattern connections.

The effects of silvicultural disturbances on cryptogam diversity in the boreal-mixedwood forest

2002 ◽  
Vol 32 (1) ◽  
pp. 38-51 ◽  
Author(s):  
Steven G Newmaster ◽  
F Wayne Bell
Keyword(s):  
Species Richness ◽  
Species Abundance ◽  
Diversity Indices ◽  
Forest Harvesting ◽  
Aerial Application ◽  
Forest Diversity ◽  
Four Blocks ◽  
Abundance And Diversity ◽  
Species Richness And Abundance ◽  
And Function

In northern forests, cryptogams (spore producing plants) occupy a key position in forest ecosystem diversity and function. Forest harvesting and silvicultural practices have the potential to reduce cryptogam diversity. This project uses four blocks that were mechanically site prepared, planted with a single conifer species, and subsequently subjected to five conifer release treatments: (1) motor-manual cleaning, (2) mechanical brush cutting, (3) aerial application of triclopyr, (4) aerial application of glyphosate, and (5) control (untreated clearcut). Five 10 × 10 m subplots were installed in each of the five treatment plots and the uncut forest on the four blocks. Botanical surveys were conducted before and 1–5 years after treatments. Species richness and abundance, Shannon's and Heip's indices, and rank abundance diagrams clearly show that richness and abundance were affected by silvicultural treatments. Vegetation management treatments resulted in significant reductions in cryptogam diversity, to the point that only a few colonists and drought-tolerant species remained. Cryptogam diversity was ranked in the following order: forest > clearcut > mechanical clearing > herbicide treatment. Herbicide treatments had the greatest initial effect on species richness, species abundance, and diversity indices. Cryptogam diversity showed signs of recovery 5 years after treatments. Missed strips (untreated areas) within a clearcut provided a refuge for remnant communities of forest cryptogams that could play a key role in the rehabilitation forest diversity.

New Mosquito Collection Records for Southern Georgia

2001 ◽  
Vol 36 (2) ◽  
pp. 114-121 ◽  
Author(s):  
John P. Smith ◽  
Thomas G. Floore
Keyword(s):  
Culex Quinquefasciatus ◽  
Species Abundance ◽  
Abundant Species ◽  
Light Traps ◽  
Aedes Vexans ◽  
Detailed Report ◽  
Mosquito Collection ◽  
Abundance And Diversity ◽  
Southern Georgia

Twenty-nine species representing eight genera, numerous new county records and one state record, Mansonia titillans (Walker), were collected in a surveillance project conducted in 20 southern Georgia counties during the summer of 1997. A detailed report of species abundance and diversity is presented. Overall, as sampled by CO2 light traps, Culex quinquefasciatus Say was the most widely distributed species and Aedes vexans (Meigen) was the most abundant species followed closely by Aedes atlanticus Dyer and Knab.

Ecology of Dolichopodidae (Diptera) in a wetland habitat and their potential role as bioindicators

2011 ◽  
Vol 6 (1) ◽  
pp. 118-129 ◽  
Author(s):  
Ivan Gelbič ◽  
Jiří Olejníček
Keyword(s):  
Species Richness ◽  
Potential Role ◽  
Species Abundance ◽  
Abundant Species ◽  
Seasonal Activity ◽  
Wet Meadow ◽  
Emergence Traps ◽  
Abundance And Diversity ◽  
Pan Traps ◽  
Malaise Traps

AbstractEcological investigations of long-legged flies (Dolichopodidae) were carried out in wet meadow wetlands near České Budějovice, Czech Republic. Sampling was performed during the adult flies’ seasonal activity (March–October) in 2002, 2003 and 2004 using yellow pan traps, Malaise traps, emergence traps, and by sweeping. Altogether 5,697 specimens of 78 species of Dolichopodidae were collected, identified and analysed. The study examined community structure, species abundance, and diversity (Shannon-Weaver’s index - H’; Sheldon’s equitability index - E). Chrysotus cilipes, C. gramineus and Dolichopus ungulatus were the most abundant species in all three years. Species richness and diversity seem strongly affected by soil moisture.

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