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Again, it is seen that earthworms potentially simplify the job of biogeographical analysis if their
biotic elements have very little overlap.
It should be clear that any analytical biogeography of this sort absolutely requires a prior
phylogenetic analysis (Wiley 1988). Ball (1975) remarked pointedly that earthworms had nothing
to offer to biogeographical analyses because the treatment of the data available then was too
superficial. With two exceptions (Jamieson 1988; Jamieson et al. 2002), all the higher-level taxo-
nomic research on earthworms is based on classical methodology (e.g., Sims 1980; Omodeo 1998,
2000). This is not to say that the classical method was bad, but that ÑnewÒ methods, particularly
cladistic analysis (Hennig 1966; Sudhaus and Rehfeld 1992), have emerged since the older gener-
ation of earthworm taxonomists was trained. Unfortunately, very few of those specialists have taken
advantage of the revolution in systematics that has occurred.
Techniques of analyzing data for phylogenetic reconstruction are evolving and diversifying
rapidly. Although maximum parsimony remains very important, other tools are coming into more
general use. Maximum likelihood and Bayesian methods have been extended from molecular to
morphological data sets and to combined morphological and molecular data (Lewis 2001). These
tools allow certain flexibilities in data treatment and coping with homoplasy (independent evolution
of characteristics by lineages with common ancestor that did not have the characteristics in question)
that will be useful in redressing the phylogenetic deficiencies mentioned here. Both Bayesian and
maximum likelihood methods use underlying mathematical models of evolution and compare the
results of the model with the actual data obtained (molecular sequences or morphological data) on
the way to deriving an estimate of phylogenetic relationships. Jamieson et al. (2002) provided an
example of the application of several methods of analysis to a phylogenetic problem, but it is just
the beginning of what needs to be done.
The field of earthworm systematics is long overdue for a reinvigoration and an influx of ideas
and techniques that are new to many of us. Good classical systematics will never lose its fundamental
value and is the foundation for the standards of publication that are often ignored by modern
authors. However, a century of work by a small but dedicated group has failed to resolve such
fundamentals as the definitions of families (e.g., Sims 1980). To date, only Jamieson (1988) and
Jamieson et al. (2002) have offered a rigorous analysis of this problem. The higher-level taxonomics
of earthworms seems to be a very good area in which to apply molecular data.
Biogeographical contributions from earthworm phylogeny need not be confined to questions
involving taxa separated by oceanic barriers. In general, earthworms are slow to disperse, mating
is highly localized, and populations may be easily isolated. If the earthworm fauna of New Zealand
is an example, it can be seen that, in mountainous regions, there can be a tremendous overall species
diversity, although the number of species present at any one site may be small (Lee 1959). Thus,
the possibility exists to investigate the phylogeny of the earthworms of a single land area in relation
to many potential fragmentations and reannealings of ranges because of geological, hydrological,
or climatological processes. Although the noise in the data may be greater than in the case of
transoceanic questions, it should still be as good as or better than the data derived from other taxa
widely cited in the biogeographical literature.
HOW THE EARTH'S HISTORY AFFECTS
EARTHWORM DISTRIBUTIONS
The question of how to learn about the history of the Earth from earthworm phylogeny and
biogeography is worth asking only because there is good reason to believe that the history of life
is linked in many ways to the history of the Earth. On the other hand, have earthworms been
affected by historical processes and on what scales of time and space? Certainly, much of the
distributions of higher earthworm taxa can be illuminated by a study of the history of the EarthÔs
crust. What appears in the present as anomalous, disjunct distributions can be understood as the
