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26 BULLETIN OF THE UNIVERSITYOF NEBRASKA STATE MUSEUM
are “complex zoological problems” and there
is doubt surrounding the identities of all species
and names.
Species Concept
I utilize the Phylogenetic Species Concept
outlined by Wheeler and Platnick (2000): species
are the smallest aggregation of populations
diagnosable by a unique combination of
character states. Each species description is
a scientific hypothesis. The number of specimens
examined (given at the beginning of
each description) is the number of replicates
studied. Character states are used to support
the hypothesis that all the individuals examined
are of the same species. The different
species can be recognized by a unique combination
of character states because they are
isolated genetically from other species (in
sexual organisms such as Platycoelia). Population
genetics has demonstrated the inevitability
of character state fixation due to various
forces, including genetic drift and natural selection.
Different character states will become
fixed in different species due to genetic isolation.
As is generally true, the strength of the
hypothesis (species description) increases
with the number of replicates (specimens) examined.
Not all species are equally diagnosable.
Some are easily recognized by examining one
individual with a unique set of characters (for
example a male with radically different
parameres), and some must be proposed only
after many individuals from different populations
are examined (when species have
recently diverged or have not changed drastically
since their divergence so fixed character
states are difficult to recognize). These analyses
must be done in the context of other
closely related species. Examining intraspecific
variation within closely related species is
an important tool in distinguishing fixed
character states from phenotypic traits that
vary within a population or species. When
traits are mistaken for fixed character states,
the number of species can be overestimated.
No species description (hypothesis) is accurate
for all of the individuals in a species.
There are sometimes anomalous individuals
that have unusual traits or have been malformed
during development. Size and coloration
of some species many vary widely from
year to year, depending on the amount of rain,
food availability, temperature, etc. Some
populations also may exhibit phenotypic
variation of certain traits at different levels
from other populations. There is also the possibility
of some low level of interspecific
breeding and gene flow between closely related
species. Ideally, a taxonomist would examine
large series of specimens from single
collecting events and from different geographic
areas within the distribution of a
given species to get a full appreciation of the
intraspecific variation. Unfortunately, this is
often a luxury we do not have. The opposing
forces of overwhelming species richness of insects
and disappearing habitats, research dollars,
and expertise make career-long
taxonomic studies of limited groups impractical.
Because all proposed species are scientific
hypotheses, examining more specimens and
specimens from different localities and populations
can test their validity. I expect that
some of my Platycoelia species designations
will have to be slightly modified as more
specimens become available.
I have not seen a compelling argument
for maintaining subspecific names in the context
of the phylogenetic species concept. In
fact, subspecies concepts all seem subjective
and reliant on the whims of the experts on
the given group to determine what populations
are deserving of the status. To me, this
harks back to the days before cladistic analysis
when taxonomic authorities would present
intuitive phylogenies as fact. I am not opposed,
on principle, to naming subspecies, but
I have yet to find an objective set of criteria
for determining whether different populations
warrant subspecific status. Therefore, I do not
recognize subspecies as valid taxa in this
work. Ohaus (1904b) proposed two subspecific
names within Platycoelia. Types of each were
examined and determined to be synonymous
with the nominal species.