genotypes, but there appears to be no evidence for any geographical pattern in
their distribution (Finlayet al., unpublished), although particular genotypes do
seem to be correlated with particular habitat types. Identical genotypes have
been recovered from Great Salt Lake, and from hypersaline ponds in Spain.
A single genotype has been isolated from brackish waters in Argentina, Japan,
Morocco and Ukraine. A further single genotype was recorded from freshwater
habitats in Guatemala and Ukraine, and another from France and Mongolia.
These data are still being gathered, but they do suggest that protist genotypes
can have cosmopolitan distribution, with no apparent biogeography.
For asexual organisms with clonal evolution there is no theory-based species
concept analogous to the biological species concept, so that in bacteria and the
asexual microbial eukaryotes, a large degree of genotypic variation is expected
Figure 9.7Intensive examination of grassland
soils in Scotland (Finlayet al., 2000) revealed
many rare species of ciliated protozoa. Amongst
them was the ciliate shown here –Notohymena
antarctica– which we found in re-wetted soil. This
isolate from Scotland represents the first record
of the species outside of the Antarctic continent,
and in the northern hemisphere (Estebanet al.,
2006 ). Protargol silver-impregnated specimen.
Scale bar 20mm.BODY SIZE AND BIOGEOGRAPHY 179