Monday, May 24

[Timothy Reluga <treluga@amath.washington.edu>]

	This coming Monday, 2:30, amath library, Rebecca would like to 
discuss the recent paper by Ellner and Fussmann on metapopulation models 
and succession.  Grab a copy at

http://www.amath.washington.edu/~treluga/Ellner03.pdf

Abstract: The classical (Levins) metapopulation scenario envisions a
species persisting in a network of habitat patches through a balance
between frequent local (within-patch) extinctions and recolonizations.
Although this is the dominant paradigm for species in fragmented habitats,
empirical support is limited, and it has been argued that ver y
restrictive conditions on migration rates are required: high enough for
recolonization to balance extinctions, but low enough that local
populations do not fluctuate in synchrony.  Through simulation and
analysis of a stochastic spatial model, we argue that the likelihood of
persistence via the classical scenario is strongly affected by some basic
properties of within-patch successional dynamics whose importance has not
been emphasized in metapopulation theor y: the distribution of
successional stage durations, and whether patches are ``refractor y'' vs.
immediately available for recolonization after an extinction has occurred.
These properties are tied to the biological causes of extinction (e.g.,
demographic accident vs.  regular successional changes) and patch recover
y (e.g., recolonization by a host species vs.  regeneration of an
exhausted resource base). Our results indicate that metapopulation theor y
needs to incorporate the patch-dynamics perspective of a landscape in a
dynamic mosaic of successional states, with particular attention to links
between colonization­extinction processes and local succession.


				Tim