Lecture 11: The Idea of Species Why do we need a definition? Species: fundamental unit of biology Earliest definition: HOLOTYPE Controversy about definition: 1. Phenetic Species Concept 2. Biological Species Concept 3. Ecological Species Concept And more…
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Lecture 11: The Idea of Species Why do we need a definition? Species: fundamental unit of biology Earliest definition: HOLOTYPE Controversy about definition:
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Lecture 11: The Idea of Species
Why do we need a definition?
Species: fundamental unit of biology
Earliest definition: HOLOTYPE
Controversy about definition:
1. Phenetic Species Concept
2. Biological Species Concept
3. Ecological Species Concept
And more…
Species Concepts from Various AuthorsD.A. Baum and K.L. Shaw - Exclusive groups of organisms, where an exclusive group is one whose members are all more closely related to
each other than to any organisms outside the group.
J. Cracraft - An irreducible cluster of organisms, diagnosably distinct from other such clusters, and within which there is a parental pattern of ancestry and descent.
Charles Darwin - "From these remarks it will be seen that I look at the term species, as one arbitrarily given for the sake of convenience to a set of individuals closely resembling each other, and that it does not essentially differ from the term variety, which is given to less distinct and more fluctuating forms. The term variety, again, in comparison with mere individual differences, is also applied arbitrarily, and for mere convenience sake" (Origin of Species, 1st ed., p. 108).
T. Dobzhansky - The largest and most inclusive reproductive community of sexual and cross-fertilizing individuals which share a common gene pool. And later...Systems of populations, the gene exchange between which is limited or prevented by reproductive isolating mechanisms.
M. Ghiselin - The most extensive units in the natural economy, such that reproductive competition occurs among their parts.
D.M. Lambert - Groups of individuals that define themselves by a specific mate recognition system.
J. Mallet - Identifiable genotypic clusters recognized by a deficit of intermediates, both at single loci and at multiple loci.
E. Mayr - Groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups.
C.D. Michener - A group of organisms not itself divisible by phenetic gaps resulting from concordant differences in character states (except for morphs - such as sex, age, or caste), but separated by such phenetic gaps from other such units.
H.E.H. Patterson - That most inclusive population of individual biparental organisms which share a common fertilization system.
G.G. Simpson - A lineage of populations evolving with time, separately from others, with its own unique evolutionary role and tendencies.
P.H.A. Sneath and R.R. Sokal - The smallest (most homogeneous) cluster that can be recognized upon some given criterion as being distinct from other clusters.
A.R. Templeton - The most inclusive population of individuals having the potential for phenotypic cohesion through intrinsic cohesion mechanisms (genetic and/or demographic - i.e. ecological -exchangeability).
E.O. Wiley - A single lineage of ancestor-descendant populations which maintains its identity from other such lineages and which has its own evolutionary tendencies and historical fate.
S. Wright - A species in time and space is composed of numerous local populations, each one intercommunicating and intergrading with others.