SYSTEMATICS: MAN'S ATTEMPT AT PIGEON-HOLING
NATURE
- One Man's Dream
- Carl Linnaeus (1707-1778); "laws of order" is taxonomy.
- Individual group of organisms is a taxon, groups of organisms are taxa. Species and higher order
taxa reflect evolutionary mechanisms.
- What DO Taxonomists DO?
- Compare different species and make decisions on their relationships;
- Examine large-scale diversity patterns in time and space
- Evaluate present and past geographic distributions and determine the underlying mechanisms
responsible for the pattern
- What IS Systematics?
- The science of the "diversity of life" and includes:
- Phylogenetic analysis (determining temporal evolutionary relationships)
- Biogeography (determining spatial relationships)
- Taxonomy is the underpinning of all other biological and paleobiological sciences.
- How Many
Taxa?
- Aristotle recognized 550 kinds of animals
- 1700s there were >6000 recorded species of plants and 4000 species of animals.
- Each species was given a binomen - genus and species epithet;
placed into a systematic hierarchy
- Phylum
- Class
- Order
- Family (-idae; -aceae)
- Genus
- species
- The International Currency - Not the Euro
- Rules of Nomenclature for animals and plants differ, slightly
- Botanists withdrew from an attempt by the British Association for the Advancement of
Science to standardize nomenclatural rules in 1842
- Both agree that priority of a taxon is based upon its date of publication.
- Rules for Zoologists
- Binominal Nomenclature. Priority of names begins arbitrarily on 1 January 1758 (10th edition of
System Naturae (Linnaeus) and Aranei Svecici (Clerck)/
- Principle of priority - the oldest available name for a taxon is its valid name (except ichnotaxa)
- Principle of the First Reviser - when normal priority can't be established, one name can become
precedent over another (e.g., simultaneous publication)
- Principle of Co-ordination -- within the family, genus, or species, a name established for a taxon
at any rank is deemed to have simultaneously established with the same author and date for the
other ranks.
- Principle of Homonymy - every taxon has a unique name different from any other.
- The Principle of Name-bearing Types - each nominal taxon has a name-bearing type. A
nominal family-group taxon has a nominal genus, a nominal genus has a nominal species, which
is designated by a holotype, lectotype, neotype, or syntype.
- Rules for Botanists
- Independence from Zoological Nomenclature - two organisms can have the same binomial
name!!
- Names of taxonomic groups are determined by nomenclatural types
- Nomenclature of a group is based upon publication priority
- Each taxonomic group can only have one name, with earliest record having priority
- Scientific names are treated as Latin regardless of derivation
- Rules of nomenclature are retroactive unless expressly limited.
- How to Classify an Animal?
- Parataxonomy? A parataxon defined as "a taxon based on a fragment or detached organ that can
be classified at genus and species levels by comparison with other fragments or detached organs,
but cannot be assigned to the same taxa at those levels as the whole animal to which it belongs."
- The Exception - Conodonts
- Dual nomenclature (one for entire apparatuses; one for isolated elements).
- Became unworkable, and the oldest name is now applied to one of the elements and has become
the accepted systematic name
- How to Classify a Plant?
- Disarticulated Plant Fossils - whole plants are rarely preserved.
- Majority of plant fossils represent organs that were lost during and/or after life.
- Paleobotanists use a system for isolated organs whereby each different organ may have a
different binomen.
- How to Classify Behavior?
- STRONG debate to erect a separate code of nomenclature for ichnofossils.
- Formal trace-fossil names are FORM TAXA and comprise an ichnogenus, ichnospecies, along
with an author and date.
- A suitable idiomorphic holotype must be designated for comparative purposes.
- METHODOLOGIES THROUGH TIME
- Mid 60's assumed relationships on comparative anatomy or morphology (similarities in
appearance) and phylogenetic relationships (the way in which organsisms are related to each
other). This introduced uncertainties and subjectivity into the method.
- Numerical Taxonomy (Phenetics) utilizes statistical techniques and "objectivity"
- Cladistics in 1970's presumed that unless phylogenetic hypotheses were testable, evolutionary
history was uncertain.
- PHENETICS
- Proposed as a purely objective and statistically valid method
- Classification should be based upon mathematical similarities between organisms.
- Taxon characteristics measured and coded (OTU), resulting in a large data matrix.
- Computer algorithms used to determine statistically related taxa; most features in
common.
- Problems arose when determined that coding and character weighting was not objective -
another subjective exercise based upon the investigator's paradigm.
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