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Matrix-calibrated species-area model


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Matrix-calibrated species-area model

  1. 1. 0.1 1 10 100 1000 1 10 100 Area Species Offshore islands of Singapore z -value (slope) Ecologists have long observed a near ubiquitous relationship between the size of an island and the number of species found on the island Koh et al. (2002) Journal of Biogeography Springtails Butterflies
  2. 2. - Arrhenius (1920) S=cA z Area Species z This so-called species-area relationship can be described by a power model
  3. 3. Because land-use change on a mainland often creates landscapes that look like islands of forests in an ocean of other land uses…
  4. 4. S=cA z S original = c z S new A new A original ( ) ...the species-area model is often used by conservation biologists to predict biodiversity loss based upon forest loss
  5. 5. However, there are 2 problems with this approach... #1: it assumes that land uses intervening forest fragments, are completely inhospitable to any species #2: it discounts the deleterious effects on a forest fragment mediated by biophysical interactions near the interface between forest and matrix Problem #2: Edge effects Problem #1: Matrix effects
  6. 6. ( ) S=cA z S original = c z S new A new A original ( ) Koh & Ghazoul (2010) Conservation Biology Koh et al. (2010) Journal of Applied Ecology The improved model accounts for how species respond to changes in composition & quality of the matrix. It also accounts for effects of forest edges. These improvements allow for predictions of extinction risks that are specific to the landscape and the taxon of interest. Correction for forest edge effects Calibrating the slope to account for taxon-specific responses to individual components of the landscape matrix
  7. 7. The matrix-calibrated species-area model
  8. 8. When pitted against four other variants of SAMs, the MC SAM is about 13.5 times more strongly supported by the data than the next best model in our analysis--the conventional SAM.
  9. 9. A prototype of an interactive online tool developed to illustrate how the new MC model (including correction for edge-effects) could be used to predict effects of land-use change in the wider landscape. (This slide is interactive.)
  10. 10. The MC SAM has been implemented in recent studies