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species than aspidogastrean species infecting them and their particular
microhabitats. And there are no potentially competing species of other
taxa in these microhabitats. In other words, there is a vast number of
vacant niches. It seems, then, that at least for the aspidogastreans, the
autecological paradigm is more useful than the demographic one.
Demographic ecologists have not found the aspidogastreans worthy of
their attention because they are rare and unlikely to compete with each
other or, to any significant extent, with species of other taxa.
Generality of the approach
The question of whether the aspidogastreans are exceptional must be
answered, and also to what extent is the autecological approach useful?
Aspidogastreans are very ancient and can be considered as living fossils.
They may have lost the versatility of undergoing much further adaptive
radiation, or - in the terminology of Kauffman ( 1993 )-theymayhave
reached radiation and fitness stasis as a consequence of adaptive walks in
rugged fitness landscapes which have led them to local optima where
they are trapped. Species that have not had such a long evolutionary
history, perhaps many insects, may still be relatively unfit and still
climbing in many directions, where the chances to encounter other,
potentially competing, species still exist. So, the possibility should be
considered that the autecological approach is best suited for slowly
evolving taxa with little adaptive potential and little speciation, whereas
the demographic approach is better suited to rapidly evolving taxa
which can adapt rapidly and speciate fast.
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