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 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.

Independent Discovery of the Equilibrium Theory of Island Biogeography

Ecology ◽  
1989 ◽  
Vol 70 (6) ◽  
pp. 1954-1957 ◽  
Author(s):  
James H. Brown ◽  
Mark V. Lomolino
Keyword(s):  
Island Biogeography ◽  
Equilibrium Theory ◽  
Theory Of Island Biogeography

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).

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 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.

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