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288
C.R. Largiadèr
different populations of Pecos pupfish (Cyprinodon pecosensis) differ in agonistic
behavior, territoriality, and in mating success when competing with the
introduced sheepshead minnow (C. variegatus). This suggests that in local
populations of C. pecosensis, the rate of introgressive hybridization with C.
variegatus may vary depending on differences in the competitive ability of
males in these populations.
16.6 Conclusions
Anthropogenic introgressive hybridization is a widespread phenomenon, and
it will certainly continue to increase in importance. Many habitat modifications
are irreversible, and there are also many situations where the mixing of
gene pools by introgression has occurred to a point where it is irreversible.
Facing this reality, managers now need to answer important questions as to
whether introgressed populations should also be conserved in some cases,
and to what degree introgression is acceptable (Allendorf et al. 2001). Should
we, for example, also conserve new taxa that have been created through
hybridization between native and introduced species, or the hybrid swarm
that has completely replaced the formerly native taxon? In this context, it is
also worth mentioning that distinguishing between natural and man-induced
hybridization is a difficult, but crucial task (Allendorf et al. 2001; Petit et al.
2004).
Predicting hybridization and its outcomes is probably an unsolvable task,
due to the complexity of potential interactions between the factors involved.
Nevertheless, for an improved management and conservation of native taxa
that are threatened by hybridization with invading taxa, it is of primary
importance to conduct more long-term studies, which systematically integrate
information on environmental and biological (including genetic) characteristics
at the level of local populations.
Finally, hybridization is an evolutionary process that plays an important
part in the context of biological invasions, which in turn are a key driving
force of current evolutionary change (Mooney and Cleland 2001). Thus, the
recent progress toward integrating evolutionary biology into invasion biology
(Lee 2002; Levin 2003) provides an important basis for further advance in
research on anthropogenic hybridization.