Biology Reference
In-Depth Information
17
CHAPTER
Corridors
As ecosystems become increasingly fragmented, interest in predicting
the ecological and population biology effects of connecting fragments via
corridors has grown (e.g., Tewksbury et al. 2002; Chetkiewicz et al. 2006;
Hilty et al. 2006). One of the primary goals of providing corridors is to
facilitate movement of organisms from one fragment to another, not only
to ensure that all fragments are populated with targeted species, but also to
reduce the degree of intraspecifi c genetic differentiation among fragments.
The effects of corridors are not all positive. For example, pathogens,
parasites, herbivores, predators, invasive species, and fi re that attenuate
conservation target species populations may more readily spread among
connected fragments (e.g., Bienen 2002; Wilson 2005). Corridors also increase
the ratio of edge to habitat, which can have untoward ecological effects on
the movement of organisms (e.g., Harper et al. 2007).
Considerable effort is currently being expended in the design,
establishment, and maintenance of interpreserve corridors. Given that
investment, tools need to be developed to provide predictive information
on movement success and gene fl ow among fragments for species of
greatest interest, and also on the spread of deleterious organisms. While a
number of empirical studies demonstrate that fragmentation and corridors
can have varying effects on the population genetics of particular species
(Kirchner et al. 2003; Levey et al. 2005; Culley et al. 2007, for example), that
plant species are highly idiosyncratic in their life history characteristics, and
that the population genetic status of particular populations often differs,
suggests that no overarching theory will be predictive across all species or
populations. Further, our impression from searching for relevant studies is
that surveys of the effects of corridors on plants is lagging behind parallel
research for animals. In the following examples, we demonstrate the use
of NEWGARDEN to examine various effects of spacing between preserves
and the construction of corridors on plant populations and conservation
genetics. These examples will demonstrate features of NEWGARDEN
trial design input that have not yet been discussed: (1) the area designated
to be the preserve, or preserves plus corridors, can be specifi ed by input
statements, and (2) input statements can be given that will determine which
subsections of such a designated preserve system will be analyzed for the
reporting of output statistics.
Search WWH ::
Custom Search