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Natural habitat can be patchy

Harrison et al. (1988) The American Naturalist 132:360-382. Euphydryas editha. Natural habitat can be patchy. Metapopulations of small mammals. Habitat loss and fragmentation Species extinction. Metapopulations of small mammals. Forests in Costarica. Monk seal. Metapopulations.

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Natural habitat can be patchy

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  1. Harrison et al. (1988) The American Naturalist 132:360-382. Euphydryas editha Natural habitat can be patchy Metapopulations of small mammals Gatto - Spatial patterns in ecology

  2. Habitat loss and fragmentation Species extinction Metapopulations of small mammals Forests in Costarica Monk seal Gatto - Spatial patterns in ecology

  3. Metapopulations Metapopulations of small mammals p = proportion of occupied patches c = colonization rate = “the probability that migrants from any given population reach another site” e = extinction rate of local populations (demographic and environmental stochasticity) Gatto - Spatial patterns in ecology

  4. The importance of discrete individuals The core of metapopulation concept Each local population is prone to extinction because each habitat patch hosts a finite number of individuals, subject to a sequence of random events In endangered populations (abundance is small in each patch) this number cannot be approximated by a real number, must be integer Correct evaluation of metapopulation persistence and extinction risk Metapopulations of small mammals Gatto - Spatial patterns in ecology

  5. Interacting Particle Systems (IPS) A system of particles (cells, organisms, etc.) that reproduce, move and die on a countable graph (e.g. a lattice) Metapopulations of small mammals x=space -2 -1 0 +1 +2 Gatto - Spatial patterns in ecology

  6. A spatially-explicit model (IPS) for metapopulations Abundance is discrete (nxy=0,1,2,...) Habitat characteristics Patches arranged in square grids (k x k matrix) Typically small grids (6x6 to 30x30) Demographic characteristics Local dynamics is logistic Metapopulations of small mammals Dispersal rules • Von Neumann (nearest 4 neighbors) • Moore (nearest 8 neighbors) • Propagule rain(from one patch to any other patch, p=1/k2) Boundary conditions • Periodic • Absorbing • Reflecting Gatto - Spatial patterns in ecology

  7. fragmentation floods forest fires rinderpest The role of disturbances Habitat loss and environmental catastrophes

  8. 6x6, Von Neumann dispersal The persistence-extinction boundaries INTERMEDIATE DISPERSAL PRINCIPLE • PE boundaries found as percolation thresholds in spatial stochastic processes • Key parameters: • dispersal rate (frequency of dispersal) D • intrinsic rate of population increase r • carrying capacity K • rate of environmental catastrophes m • remaining habitat h PERSISTENCE Metapopulations of small mammals Levins-like approximation Casagrandi & Gatto (1999) Nature400: 560.Casagrandi & Gatto (2002a) Theoretical Population Biology61: 115. Casagrandi & Gatto (2005) Journal of Theoretical Biology239: 22. Gatto - Spatial patterns in ecology

  9. The synergism between disturbances Habitat loss and environmental catastrophes

  10. Linking key parameters to species physiologyBody size M is the main determinant Metapopulations of small mammals Gatto - Spatial patterns in ecology

  11. Allometric scaling in small mammals Savage et al., 2004 Metapopulations of small mammals Kelt and Van Vuren, 1999

  12. Perceptual range Metapopulations of small mammals Mech SG, Zollner Pa (2002) Using body size to predict perceptual range. Oikos 98:47–52 H = height on the horizon (m) Gatto - Spatial patterns in ecology

  13. Small mammals in landscapes Bowman et al., 2002 db L Metapopulations of small mammals Mech and Zollner, 2002 db/2

  14. The landscape effect on PE boundary Small L (50 m) Small db (25 m) PERSISTENCE db L Metapopulations of small mammals 15x15 cells Large L (450) Large db (225) db/2 PERSISTENCE Gatto - Spatial patterns in ecology

  15. The effect of habitat loss and environmental catastrophes Metapopulations of small mammals

  16. That’sallfolks! Thanksfor yourattention Gatto - Spatial patterns in ecology

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