scholarly journals Marine subsidies mediate patterns in avian island biogeography

2020 ◽  
Vol 287 (1922) ◽  
pp. 20200108
Author(s):  
Debora S. Obrist ◽  
Patrick J. Hanly ◽  
Jeremiah C. Kennedy ◽  
Owen T. Fitzpatrick ◽  
Sara B. Wickham ◽  
...  
Keyword(s):  
Species Richness ◽  
Population Density ◽  
Island Biogeography ◽  
Forest Edge ◽  
Bird Communities ◽  
Negative Interaction ◽  
Breeding Bird ◽  
Island Area ◽  
Marine Subsidies ◽  
Theory Of Island Biogeography

The classical theory of island biogeography , which predicts species richness using island area and isolation, has been expanded to include contributions from marine subsidies, i.e. subsidized island biogeography (SIB) theory . We tested the effects of marine subsidies on species diversity and population density on productive temperate islands, evaluating SIB predictions previously untested at comparable scales and subsidy levels. We found that the diversity of terrestrial breeding bird communities on 91 small islands (approx. 0.0001–3 km 2 ) along the Central Coast of British Columbia, Canada were correlated most strongly with island area, but also with marine subsidies. Species richness increased and population density decreased with island area, but isolation had no measurable influence. Species richness was negatively correlated with marine subsidy, measured as forest-edge soil δ 15 N. Density, however, was higher on islands with higher marine subsidy, and a negative interaction between area and subsidy indicates that this effect is stronger on smaller islands, offering some support for SIB. Our study emphasizes how subsidies from the sea can shape diversity patterns on islands and can even exceed the importance of isolation in determining species richness and densities of terrestrial biota.

scholarly journals Maintenance of biodiversity on islands

2016 ◽  
Vol 283 (1829) ◽  
pp. 20160102 ◽  
Author(s):  
Ryan A. Chisholm ◽  
Tak Fung ◽  
Deepthi Chimalakonda ◽  
James P. O'Dwyer
Keyword(s):  
Species Richness ◽  
Island Biogeography ◽  
Mechanistic Model ◽  
Neutral Theory ◽  
Small Island ◽  
Small Islands ◽  
Island Area ◽  
Island Species ◽  
Theory Of Island Biogeography ◽  
Species Area

MacArthur and Wilson's theory of island biogeography predicts that island species richness should increase with island area. This prediction generally holds among large islands, but among small islands species richness often varies independently of island area, producing the so-called ‘small-island effect’ and an overall biphasic species–area relationship (SAR). Here, we develop a unified theory that explains the biphasic island SAR. Our theory's key postulate is that as island area increases, the total number of immigrants increases faster than niche diversity. A parsimonious mechanistic model approximating these processes reproduces a biphasic SAR and provides excellent fits to 100 archipelago datasets. In the light of our theory, the biphasic island SAR can be interpreted as arising from a transition from a niche-structured regime on small islands to a colonization–extinction balance regime on large islands. The first regime is characteristic of classic deterministic niche theories; the second regime is characteristic of stochastic theories including the theory of island biogeography and neutral theory. The data furthermore confirm our theory's key prediction that the transition between the two SAR regimes should occur at smaller areas, where immigration is stronger (i.e. for taxa that are better dispersers and for archipelagos that are less isolated).

Functional evenness of bird communities varies along the elevational gradient in Europe: Conservation implications

2019 ◽  
Author(s):  
Federico Morelli ◽  
Yanina
Keyword(s):  
Species Richness ◽  
Elevation Gradient ◽  
Bird Species ◽  
Elevational Gradient ◽  
Negative Association ◽  
Bird Communities ◽  
Breeding Bird ◽  
Bird Species Richness ◽  
Large Spatial Scale ◽  
Functional Evenness

ContextThe negative association between elevation and species richness is a well-recognized pattern in macro-ecology. ObjectivesThe aim of this study was to investigate changes in functional evenness of breeding bird communities along an elevation gradient in Europe. MethodsUsing the bird data from the EBCC Atlas of European Breeding Birds we estimated an index of functional evenness which can be assumed as a measure of the potential resilience of communities.ResultsOur findings confirm the existence of a negative association between elevation and bird species richness in all European eco regions. However, we also explored a novel aspect of this relationship, important for conservation: Our findings provide evidence at large spatial scale of a negative association between the functional evenness (potential community resilience) and elevation, independent of the eco region. We also found that the Natura2000 protected areas covers the territory most in need of protection, those characterized by bird communities with low potential resilience, in hilly and mountainous areas.ConclusionsThese results draw attention to European areas occupied by bird communities characterized by a potential lower capacity to respond to strong ecological changes, and, therefore, potentially more exposed to risks for conservation.

scholarly journals Altitudinal diversity gradients and the theory of island biogeography - an explanation

2002 ◽  
Vol 8 (3) ◽  
pp. 213
Author(s):  
John Ogden
Keyword(s):  
Species Richness ◽  
New Zealand ◽  
Environmental Variables ◽  
Island Biogeography ◽  
Environmental Heterogeneity ◽  
Causal Agent ◽  
Forest Diversity ◽  
Island Biogeography Theory ◽  
Diversity Gradients ◽  
Theory Of Island Biogeography

As part of a wider discussion of forest diversity in New Zealand, Ogden (1995) pointed out that the area available between any pair of contours on a conical mountain decreased with altitude in parallel with the decrease in species richness. This correlation is confounded with other environmental variables, such as temperature, which have been widely considered to be causal in the diversity decline. However, generalization has been elusive, and the supposed causal mechanisms are often couched in vague terms such as "harshness". Ogden chose to emphasize area, and invoked the theory of island biogeography of MacArthur and Wilson (1967) by drawing parallels between islands and successively superimposed areas on mountains. Kingston (this issue) objected, mainly on the grounds that the theory of island biogeography refers to "isolated" areas and deals with the equilibrium between immigration and extinction, on which Ogden presented no evidence. In the light of these criticisms the data presented in Ogden (1995) is re-assessed here. I conclude that the "area hypothesis" is at least as good as any other for "explaining" (correlating with) elevational diversity trends. Area is itself correlated with environmental heterogeneity, which is presumably more important as a causal agent. However, Kingston's insistence on the need for evidence on immigration and extinction to support the application of island biogeography theory is acknowledged.

scholarly journals Can altitudinal diversity gradients be explained by a reduction in area with altitude?

2002 ◽  
Vol 8 (3) ◽  
pp. 211
Author(s):  
Cath Kingston
Keyword(s):  
Species Richness ◽  
Surface Area ◽  
Environmental Conditions ◽  
Island Biogeography ◽  
Equilibrium Theory ◽  
Diversity Gradients ◽  
Theory Of Island Biogeography ◽  
Reduction In Area

Species richness at higher altitudes of a region typically decreases with altitude, the usual explanation being that environmental conditions become harsher as altitude increases. On conical or ridge shaped mountains the surface area available within equally spaced altitude bands declines as altitude increases. It has been suggested (Ogden 1995) that this may be responsible for the decrease in species richness. The phenomenon of decreasing species richness with altitude has been further interpreted by Ogden as lending support to the equilibrium theory of island biogeography (MacArthur and Wilson 1967) which predicts that larger areas will contain more species. The hypothesis that a decrease in area is responsible for the decline in diversity with altitude is here considered critically, and the evidence presented in support of it is found to be lacking.

scholarly journals Edge effects in the avifaunal community of riparian rain-forest tracts in Tropical North Queensland

2016 ◽  
Vol 32 (4) ◽  
pp. 280-289 ◽  
Author(s):  
Montague H. C. Neate-Clegg ◽  
Emily C. Morshuis ◽  
Cristina Banks-Leite
Keyword(s):  
Species Richness ◽  
Community Composition ◽  
Edge Effects ◽  
Rain Forest ◽  
Forest Edge ◽  
Bird Communities ◽  
Forest Bird ◽  
Resource Distributions ◽  
Detection Frequency ◽  
Open Canopy

AbstractMost evidence suggests anthropogenic edges negatively affect rain-forest bird communities but little has been done to test this in Australasia. In this study, avifaunal detection frequency, species richness and community composition were compared between the edge and interior and between flat and more complex-shaped edges of riparian rain-forest tracts in Tropical North Queensland. The detection frequency and richness of guilds based on diet, foraging strata and habitat specialism were also compared. This study detected 15.1% more birds at the rain-forest edge compared with the interior but no difference in species richness. Edge shape had no effect on detection frequency or richness. Many guilds (subcanopy, closed forest, frugivorous and insectivorous species) experienced increased detection frequency at the edge relative to the interior, but for some guilds this response was reduced (habitat generalists) or reversed (understorey and mixed-flock species) along complex edges. Overall community composition was affected by edge distance but not by edge shape. Edge habitat was shorter and had more open canopy than the interior, supporting habitat-based explanations for the observed avifaunal edge effects. These results suggest generally positive edge effects in Australian rain-forest bird communities, possibly reflecting local resource distributions or a disturbance-tolerant species pool.

scholarly journals What Do Ecological Paradigms Offer to Conservation?

2010 ◽  
Vol 2010 ◽  
pp. 1-9 ◽  
Author(s):  
Som B. Ale ◽  
Henry F. Howe
Keyword(s):  
Species Richness ◽  
Biodiversity Conservation ◽  
Community Composition ◽  
Carrying Capacity ◽  
Island Biogeography ◽  
Ecological Theory ◽  
Theory And Practice ◽  
Logistic Growth ◽  
Theory Of Island Biogeography ◽  
Conservation Plans

Ecological theory provides applications to biodiversity management—but often falls short of expectations. One possibility is that heuristic theories of a young science are too immature. Logistic growth predicts a carrying capacity, but fisheries managed with the Lotka-Volterra paradigm continue to collapse. A second issue is that general predictions may not be useful. The theory of island biogeography predicts species richness but does not predict community composition. A third possibility is that the theory itself may not have much to do with nature, or that empirical parameterization is too difficult to know. The metapopulation paradigm is relevant to conservation, but metapopulations might not be common in nature. For instance, empirical parameterization within the metapopulation paradigm is usually infeasible. A challenge is to determine why ecology fails to match needs of managers sometimes but helps at other. Managers may expect too much of paradigmatic blueprints, while ecologists believe them too much. Those who implement biodiversity conservation plans need simple, pragmatic guidelines based on science. Is this possible? What is possible? An eclectic review of theory and practice demonstrate the power and weaknesses of the ideas that guide conservation and attempt to identify reasons for prevailing disappointment.

Boreal ground-beetle (Coleoptera: Carabidae) assemblages of the mainland and islands in Lac la Ronge, Saskatchewan, Canada

2017 ◽  
Vol 149 (4) ◽  
pp. 491-503 ◽  
Author(s):  
Aaron J. Bell ◽  
Iain D. Phillips ◽  
Scott E. Nielsen ◽  
John R. Spence
Keyword(s):  
Species Richness ◽  
Island Biogeography ◽  
Passive Sampling ◽  
Unit Area ◽  
Ground Beetle ◽  
Small Islands ◽  
Island Size ◽  
Extinction Rates ◽  
Theory Of Island Biogeography ◽  
Species Area

AbstractWe tested the applicability of the “passive sampling” hypothesis and theory of island biogeography (TIB) for explaining the diversity of forest-dwelling carabid assemblages (Carabidae: Coleoptera) on 30 forested islands (0.2–980.7 ha) in Lac la Ronge and the adjacent mainland in Saskatchewan, Canada. Species richness per unit area increased with distance to mainland with diversity being highest on the most isolated islands. We detected neither a positive species-area relationship, nor significant differences in species richness among island size classes, or between islands and the mainland. Nonetheless, carabid assemblages distinctly differed on islands <1 ha in area and gradually approached the structure of mainland assemblages as island area increased. Small islands were characterised by abundant populations of small-bodied, winged species and few if any large-bodied, flightless species like Carabus taedatus Fabricius. Our findings suggest that neither the “passive sampling” hypothesis nor the theory of island biogeography adequately explain carabid beetle diversity patterns observed among islands in Lac la Ronge. Instead, we hypothesise that population processes such as higher extinction rates of large-bodied, flightless species and the associated release of smaller-bodied, flying species from intra-guild predation on small islands contribute to observed differences in the structure of carabid assemblages between islands.

scholarly journals Breeding bird communities in a morain landscape (Affi, North-Western Venetia): a preliminary survey.

2012 ◽  
Vol 81 (2) ◽  
Author(s):  
Corrado Battisti ◽  
Giuseppe Dodaro
Keyword(s):  
Species Richness ◽  
Diversity Index ◽  
Research Effort ◽  
Absolute Number ◽  
Bird Communities ◽  
Breeding Bird ◽  
Number Of Species ◽  
The Mean ◽  
High Level ◽  
River Plain

A pilot study was conducted on a moraine hilly landscape (Affi, Verona). We found 43 species of birds overall (40 breeding, two migrants, one exotic species). Mosaics showed the largest absolute number of species (n = 25), the higher mean species richness and the highest diversity index. The croplands and wood fragments, on the contrary, pointed out the lowest absolute number of species, the vineyards showed the mean species richness. These bird communities are typical of conditions with high heterogeneity (mosaic environment) to medium-high level of anthropization, with a species composition characterized by the dominance of common and widespread taxa. We observed individuals of Ptyonoprogne rupestris in atypical environments (anthropized river plain). A stronger research effort is necessary in order to complete the knowledge of breeding bird communities in these particular environments.

scholarly journals Rural–urban gradient and land use in a millenary metropolis: how urbanization affects avian functional groups and the role of old villas in bird assemblage patterning

Web Ecology ◽  
2013 ◽  
Vol 13 (1) ◽  
pp. 49-67 ◽  
Author(s):  
L. Vignoli ◽  
S. Scirè ◽  
M. A. Bologna
Keyword(s):  
Land Use ◽  
Species Richness ◽  
Inner City ◽  
Functional Groups ◽  
Bird Communities ◽  
Urban Gradient ◽  
Natural Areas ◽  
Breeding Bird ◽  
Bird Assemblages ◽  
Species Groups

Abstract. Urbanization generally leads to a complex environmental gradient, ranging from almost undisturbed natural areas to highly modified urban landscapes. Here we analyse the effects of a rural–urban gradient on breeding bird communities and functional species groups in remnant natural and semi-natural areas of Rome. A total of 69 breeding bird species were found in the study area. Species richness decreased with increasing urbanization at two spatial scales: the point count station and the landscape scales. Evenness showed a negative trend from periphery to city centre, whereas for dominant species the opposite was true. Functional species groups responded to the urbanization gradient with functional group-specific patterns. Those groups linked to open habitats (nesting and habitat functional groups) decreased in abundance along the rural–urban gradient, whereas those associated with forests exhibited a mixed trend. Generalist species' occurrence increased with urbanization. As for predators and granivorous species, we found a negative relationship with urbanization whereas for omnivorous species the opposite trend was true. The distribution of old villas (large-sized remnant green areas) in the inner city areas influenced species composition along the studied gradient, usually showing higher species richness than surrounding fragments. Agricultural areas hosted richer and better balanced bird assemblages in respect to those found in urban and forested areas. Our findings proved that an urban gradient plays a major role in structuring bird communities, although the extent and distribution of land use categories was another factor that influenced avian assemblages. The presence of historical villas also influenced bird assemblages, making it possible to preserve high bird diversity even in inner city-areas.

scholarly journals From Island Biogeography to Conservation: A Multi-Taxon and Multi-Taxonomic Rank Approach in the Tuscan Archipelago

Land ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 486
Author(s):  
Enrico Ruzzier ◽  
Leonardo Forbicioni ◽  
Rodolfo Gentili ◽  
Nicola Tormen ◽  
Olivia Dondina ◽  
...  
Keyword(s):  
Species Richness ◽  
Differential Effect ◽  
Island Biogeography ◽  
Regression Models ◽  
Habitat Diversity ◽  
Land Bridge ◽  
Taxonomic Rank ◽  
Island Area ◽  
Species Area ◽  
Species Area Relationship

Investigating the drivers that support species richness (S) in insular contexts can give insights for the conservation of insular biodiversity. Our aim was to decouple the effect of drivers (island area, distance from mainland and habitat diversity) accounted in three hypotheses or a combination of them in explaining S in seven islands of the Tuscan Archipelago: Area (species–area relationship, SAR), area and distance from mainland (equilibrium hypothesis, EQH) and habitat (habitat diversity hypothesis, HDH). We used published and original datasets to assess S (except aliens) for 42 taxa (14 animal and 28 plant taxa) in each island, and we used S as the dependent variable and the drivers as covariates in regression models. In 31 taxa, the data supported one of the tested hypotheses or a combination of them, and the most commonly supported hypotheses were SAR (12 taxa) and EQH (10 taxa). The effect of the area was also evident in SAR + HDH (five taxa) and EQH + HDH (one taxon), making it the prevailing driver in explaining S. Since distances are relatively short, and three out of four islands are land-bridge islands, the effect of distance was significant for 12 taxa. The effects of habitat diversity were evident for just nine taxa. The multi-taxon approach allowed us to understand the differential effect of drivers among taxa in influencing S in a single archipelago. Moreover, the multi-taxonomic rank approach highlighted how the information contained within higher taxonomic ranks (e.g., Division) can be substantially different from that derived from lower ranks (e.g., Family). These insights are of particular importance from a conservation perspective of the archipelago’s biodiversity, and this approach can be transferred to mainland fragmented systems.

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