lecture 5 Flashcards
systematics
study of biological diversity and its origins and evolutionary relationships among organisms and their traits, ecology, and geographic distributions.
taxonomy
theory and practice of describing, identifying, naming, and classifying organisms.
nomenclature
set of rules governing taxonomic practice
classification
hierarchical scheme for arranging or organizing nomenclatural rules
taxon
basic unit of systematics; can refer to any named groups of organisms. provides universal vocabulary of names for distinct organisms
taxa
plural of taxon
Tuatura (Sphenodon photatus)
l- ast survivor of the order Rhynchocephalia, isolated on New Zealand for 82 mil yrs, legislation to protect species, but not all pops (40 islands, 25% extinct); failure to recognize distinct species; already one known extinction
- MCH diversity has adaptive significance for pathogen resistance.
- Tuatara pops. are highly differentiated.
- pop on North Brothers island is a distinct species of Spheodon guntheri (~350 left).
Describing new species
- 2 mill species are described
- about 8 mill left to be discovered and described
Describing new species requires a lot of work
- description and diagnosis must be adequately published in widely accessible form
- criteria of availability: name must be available
- validity of name: principle of priority, not already in use
- bionominal form in latin or greek (Genus species (italic (or underline)).
- law of type fixation: designated type specimen, name bearer
Species description ex
New combination (name of species in italics) sp. nov. (bold)
- holotype:
- paratype:
- diagnosis:
- desc of holotype:
- coloration of holotype:
- variation:
- etymology:
- distribution & ecology:
- remarks:
type specimens
- provide a physical reference point for a named taxonomic unit; are not typical representatives of a species
- provide a historical reference point for a species diagnosis
holotype
single physical example of an organisms used to formally describe a species
paratype
additional specimens other than the holotype, listed in the type series, where the original description designated a holotype.
neotype
a specimen later selected to serve as the single type specimen when the original holotype was lost or destroyed or never designated.
why do species matter?
- research in specimens in museum collections represent evidence and data for investigating biodiversity
- specimens document variation with species, distributions (current and historical), seasonal patterns, age differences, etc.
- collections based museum research is the primary driver of all phylogenetic and systematic work
- Specimens contain sources of data that are not apparent to us today, but will be of crucial importance in the future.
Authorities for naming new taxa
- responsible for providing and regulating nomenclature systems.
- promote stability and universality in the scientific names of animals and to ensure that the name of each taxon is unique and distinct (stable taxonomy = useful taxonomy; traceable and documented history of names)
Carl Linnaeus
- 1748; published Systema naturae, his classification of all plants and animals known at the time.
- classification based on a progressive subdivision of groups based on overall similarities and differences
- many features of his system are still used today (taxonomic ranks)
Problems with ranked classification
- typological - impossible to describe all genetic and morphological diversity of a species with a single specimen or a type species (paratypes)
- ranks - impossible to provide enough ranks to describe all evolutionary relationships
Ranks promote misguided biological comparisons
- comparisons have no phylogenetic basis
- no correspondence to age of group
- paraphyletic group - a group that includes a common ancestor and only some of the descendants of that ancestor (living and extinct)
- ranks are arbitrary and subjective
Rank free classification
- phylocode - rules governing phylogenetic nomenclature. it is designed to name parts of the tree of life by explicit reference to the phylogeny.
- the phylocode will only allow the naming of the clades, not of paraphyletic or polyphyletic groups.
- only species and clades have names; all ranks above species are excluded from the nomenclature.
- only allows the use of specimens, species, and apormorphies as specifiers (anchors)
- can be used concurrently with the existing codes based on rank-based nomenclature (ICBN, ICZN, etc)
Rank free classification: node based
the clade originating with the most recent common ancestor of A and B
Rank free classification: branch based
the clade that consists of A and all species that share a more recent common ancestor with A than C
Rank free classification: apomorphy based
the clade originating with the first species to possess apomorphy X as inherited by A and B.
