Ornithology, Evolution, and Philosophy 123

10
Systematics and Classification
The systematist is interested in zoological uniqueness, in whole organisms, and
systems. He determines the characters of taxa, their variation, and the biological
causes for differences or shared characters. Classification, the delimitation, ordering
and ranking of taxa, makes the organic diversity accessible to systematics at
large and to other biological disciplines. The specific method of the systematist is
comparison, not the experiment (Mayr 1969b).
Diversity
The diversity of the organic world presents the systematist with numerous challenges
at different levels of integration (Mayr 1974c). Inventory taking, at whatever
level, is the first step and in taxonomy this means the delimitation of species
taxa. The origin of diversity refers to the development of new genotypes (through
mutation, recombination, etc.), new populations (through geographical variation,
reduction of gene flow, etc.), new species and genera. Macroevolution is nothing
but an extension of microevolution at the level of subspecies and species and a response
to a previously vacant ecological zone. Real advances during the course
of evolution were the widespread adoption of sexuality and multicellularity, and
in plants vascularity and angiospermy. Each was a major step that provided an
entirely new platform for the development of more evolutionary diversity. It is the
study of diversity which has slowly undermined essentialism which dominated the
study of nature for centuries.
The great contributions made by systematists during the 19th century include
population thinking (which developed from the recognition of individuality), the
theory of geographic speciation and the biological species concept which were
incorporated into biology anonymously step by step and in such a gradual way
that systematics did not receive due credit (Mayr 1968b). Again systematists played
a decisive role in the development of the synthetic theory of evolution. Systematics
is one of the cornerstones of biology. Their practitioners investigated the
role of geographical isolation and of isolating mechanisms, the rates and trends
of evolution, the emergence of evolutionary novelties, polytypic species, population
structure and the never ending variety of solutions found by organisms to
cope with similar challenges of the environment. Mayr (l.c.) saw no conflict between
molecular biology and organismic biology (including systematics): “Each
level of integration poses its own specific problems, requires its own methods
and techniques, and develops its own theoretical framework and generalizations.”