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Is spatial autocorrelation an intrinsic property of territory size?

Valcu M, Kempenaers B - Oecologia (2010)

Bottom Line: In animals, competition for space and resources often results in territorial behaviour.We found significant positive SAC in a wide array of competition-simulated conditions.Our results strongly suggest that SAC is an intrinsic trait of any territory measure.

View Article: PubMed Central - PubMed

Affiliation: Department of Behavioural Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, Seewiesen, Germany. valcu@orn.mpg.de

ABSTRACT
In animals, competition for space and resources often results in territorial behaviour. The size of a territory is an important correlate of fitness and is primarily determined by the spatial distribution of resources and by interactions between competing individuals. Both of these determinants, alone or in interaction, could lead to spatial non-independence of territory size (i.e. spatial autocorrelation). We investigated the presence and magnitude of spatial autocorrelation (SAC) in territory size using Monte Carlo simulations of the most widely used territory measures. We found significant positive SAC in a wide array of competition-simulated conditions. A meta-analysis of territory size data showed that SAC is also a feature of territories mapped based on behavioural observations. Our results strongly suggest that SAC is an intrinsic trait of any territory measure. Hence, we recommend that appropriate statistical methods should be employed for the analysis of data sets where territory size is either a dependent or an explanatory variable.

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Moran’s I coefficient (IM) of Thiessen territory size at the scale of closest neighbours as a function of inhibition distance (r) of a sequential spatial inhibition point process (see Materials and methods for details). The confidence envelope (greyarea) represents simulated 95% confidence limits. The upper thin horizontal line indicates the IM of Thiessen territory size constructed from territory centres under complete spatial randomness. The lower thin horizontal line is the expected value of IM, under the  hypothesis of no autocorrelation, for the minimum sample size (n = 34)
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Fig1: Moran’s I coefficient (IM) of Thiessen territory size at the scale of closest neighbours as a function of inhibition distance (r) of a sequential spatial inhibition point process (see Materials and methods for details). The confidence envelope (greyarea) represents simulated 95% confidence limits. The upper thin horizontal line indicates the IM of Thiessen territory size constructed from territory centres under complete spatial randomness. The lower thin horizontal line is the expected value of IM, under the hypothesis of no autocorrelation, for the minimum sample size (n = 34)

Mentions: Significant SAC was present in the simulated Thiessen territories generated under increased competition (SSI) across the whole range of inhibition radii r, whereby the IM decreased with increasing r (Fig. 1). However, the decrease in IM only started at a relatively large inhibition radius (r = 0.25; Fig. 1), suggesting that an increasing level of competition will minimally affect SAC. Even for the largest possible inhibition radius, the SAC was still positive and significant [IM = 0.22, 95% CI = (0.04, 0.4)].Fig. 1


Is spatial autocorrelation an intrinsic property of territory size?

Valcu M, Kempenaers B - Oecologia (2010)

Moran’s I coefficient (IM) of Thiessen territory size at the scale of closest neighbours as a function of inhibition distance (r) of a sequential spatial inhibition point process (see Materials and methods for details). The confidence envelope (greyarea) represents simulated 95% confidence limits. The upper thin horizontal line indicates the IM of Thiessen territory size constructed from territory centres under complete spatial randomness. The lower thin horizontal line is the expected value of IM, under the  hypothesis of no autocorrelation, for the minimum sample size (n = 34)
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2821514&req=5

Fig1: Moran’s I coefficient (IM) of Thiessen territory size at the scale of closest neighbours as a function of inhibition distance (r) of a sequential spatial inhibition point process (see Materials and methods for details). The confidence envelope (greyarea) represents simulated 95% confidence limits. The upper thin horizontal line indicates the IM of Thiessen territory size constructed from territory centres under complete spatial randomness. The lower thin horizontal line is the expected value of IM, under the hypothesis of no autocorrelation, for the minimum sample size (n = 34)
Mentions: Significant SAC was present in the simulated Thiessen territories generated under increased competition (SSI) across the whole range of inhibition radii r, whereby the IM decreased with increasing r (Fig. 1). However, the decrease in IM only started at a relatively large inhibition radius (r = 0.25; Fig. 1), suggesting that an increasing level of competition will minimally affect SAC. Even for the largest possible inhibition radius, the SAC was still positive and significant [IM = 0.22, 95% CI = (0.04, 0.4)].Fig. 1

Bottom Line: In animals, competition for space and resources often results in territorial behaviour.We found significant positive SAC in a wide array of competition-simulated conditions.Our results strongly suggest that SAC is an intrinsic trait of any territory measure.

View Article: PubMed Central - PubMed

Affiliation: Department of Behavioural Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, Seewiesen, Germany. valcu@orn.mpg.de

ABSTRACT
In animals, competition for space and resources often results in territorial behaviour. The size of a territory is an important correlate of fitness and is primarily determined by the spatial distribution of resources and by interactions between competing individuals. Both of these determinants, alone or in interaction, could lead to spatial non-independence of territory size (i.e. spatial autocorrelation). We investigated the presence and magnitude of spatial autocorrelation (SAC) in territory size using Monte Carlo simulations of the most widely used territory measures. We found significant positive SAC in a wide array of competition-simulated conditions. A meta-analysis of territory size data showed that SAC is also a feature of territories mapped based on behavioural observations. Our results strongly suggest that SAC is an intrinsic trait of any territory measure. Hence, we recommend that appropriate statistical methods should be employed for the analysis of data sets where territory size is either a dependent or an explanatory variable.

Show MeSH