The importance of samples and isolates for species–area relationships

Tjørve, Even; Turner, Will R.

doi:10.1111/j.1600-0587.2008.05515.x

Cited by 38 publications

(38 citation statements)

References 82 publications

(122 reference statements)

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“…5; see also Rosenzweig, 1995;Tjørve & Turner, 2009;Triantis et al, 2012). 5; see also Rosenzweig, 1995;Tjørve & Turner, 2009;Triantis et al, 2012).…”

Section: Extinction Debt and Species-area Relationshipsmentioning

confidence: 96%

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Extinction debt and the species–area relationship: a neutral perspective

Halley

Sgardeli

Triantis

2013

Global Ecology and Biogeography

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Aim To estimate the magnitude of delayed relative to imminent extinctions and to assess the importance of delay as a potential source of error in forecasts of extinction. To formulate a simple mechanistic model using neutral theory that links extinction debt with the species–area relationship (SAR). Location World‐wide. Methods We use the neutral model of biodiversity to describe how a community subject to immigration responds to an insular contraction. We investigate the species richness at different times after the habitat‐loss event. We compare this with observed species losses in avian studies. Results From the model, two SARs emerge: one with a shallow slope for a habitat area before habitat loss and another with a steeper slope for the habitats that remain after habitat loss. From these curves, the first predicts imminent extinctions while the second predicts total extinctions. The difference between the two curves gives the delayed extinctions, namely the number of species that are lost during the relaxation of the community to equilibrium. The model agrees well with observed relaxation rates in communities of birds. The lag times for relaxation are often very large, with half‐lives in the order of thousands of years for remnant areas above 5000 km2. In many parameter combinations explored, the majority of extinctions are delayed extinctions, and may exceed imminent extinctions by orders of magnitude. Main conclusions Extinction debt is a major reason for failures to observe extinctions following habitat loss. Our modelling approach supports the view that a significant proportion of extinctions are delayed, so that the predictions of SARs (as currently applied) are liable to underestimate total extinctions. SARs are a valuable instrument for conservation but must be used with caution.

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“…5; see also Rosenzweig, 1995;Tjørve & Turner, 2009;Triantis et al, 2012). 5; see also Rosenzweig, 1995;Tjørve & Turner, 2009;Triantis et al, 2012).…”

Section: Extinction Debt and Species-area Relationshipsmentioning

confidence: 96%

“…2, where the upper curves represent sample areas and the lower curve represents isolates, long-term equilibrium communities. 4 provides a quantitative form for the arguments presented by Preston (1962) and Tjørve & Turner (2009). While the exact form of the loci is different in Fig.…”

Section: The Relative Magnitude Of Delayed and Imminent Extinctionsmentioning

confidence: 99%

Extinction debt and the species–area relationship: a neutral perspective

Halley

Sgardeli

Triantis

2013

Global Ecology and Biogeography

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“…Species–area curves generated from islands or other types of isolated areas are also termed isolate curves (e.g. Tjørve & Turner, 2009). As early as almost four decades ago, Preston’s (1962a,b) magisterial work discussed differences in slope and curve shape between sample‐area curves and isolate curves (in log–linear space).…”

Section: The Isolate Curvementioning

confidence: 99%

“…breeding habitat, space, nutrients or food), point (or catastrophic) events, and inbreeding (Turner & Tjørve, 2005). Tjørve & Turner (2009, p. 391) state that ‘Minimum‐area effects on actual islands and other isolates predictably cause species–area curves either to be sigmoid in arithmetic space or to be lowered for smaller areas’, and report sigmoid isolate curves in a number of data sets, which cover large‐scale windows going from very fine to coarse scales. Sigmoid curves may not be obtainable for all isolate‐area relationships because the size of islands with no species is so small that it will hardly affect the outcome of the regression.…”

Section: The Isolate Curvementioning

confidence: 99%

Subjecting the theory of the small-island effect to Ockham’s razor

Tjørve¹,

Tjørve²

2011

Journal of Biogeography

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Species–area curves from islands and other isolates often differ in shape from sample‐area curves generated from mainlands or sections of isolates (or islands), especially at finer scales. We examine two explanations for this difference: (1) the small‐island effect (SIE), which assumes the species–area curve is composed of two distinctly different curve patterns; and (2) a sigmoid or depressed isolate species–area curve with no break‐points (in arithmetic space). We argue that the application of Ockham’s razor – the principle that the simplest, most economical explanation for a hypothesis should be accepted over less parsimonious alternatives – leads to the conclusion that the latter explanation is preferable. We hold that there is no reason to assume the ecological factors or patterns that affect the shapes of isolate (or island) curves cause two distinctly different patterns. This assumption is not required for the alternative, namely that these factors cause a single (though depressed) isolate species–area curve with no break‐points. We conclude that the theory of the small‐island effect, despite its present standing as an accepted general pattern in nature, should be abandoned.

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“…The general SAR equation, where the species number, S a , is a function of area a , S a = f ( a ), is expected to take the form of a convex-upward decelerating curve16. Similarly, S A−a = f ( A − a ), and S A = f ( A ), where A is the total area.…”

Section: Resultsmentioning

confidence: 99%

Fundamental equations for species-area theory

Pan

2013

Sci Rep

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Species-area theory is an important concept in ecology. However, debates still surround the species-area relationship (SAR) or endemics-area relationship (EAR) and their relations to expected extinction rates. In this paper, I introduce the concept of overlap-area relationship (OAR) to link SAR and EAR. Two fundamental equations are derived from the relationship between the area and species number in a limited whole area A: 1) the sum of species number in area a and species number, here defined as endemics, in area A − a is the total species number in area A; 2) the number of species common to both areas a and A − a (overlapping species) equals the species number in area a minus the endemics number in area a. Thus, we should carefully consider the total area on which EAR depends, when estimating extinction rate based on SAR.

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The importance of samples and isolates for species–area relationships

Cited by 38 publications

References 82 publications

Extinction debt and the species–area relationship: a neutral perspective

Extinction debt and the species–area relationship: a neutral perspective

Subjecting the theory of the small-island effect to Ockham’s razor

Fundamental equations for species-area theory

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