Pal Chapter 3 Species and Speciation

7/30/2019 Pal Chapter 3 Species and Speciation

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Species and SpeciationSpecies and Speciation

ARE SPECIES REAL IN NATURE?ARE SPECIES REAL IN NATURE?

Arbitrary creations of humans?Arbitrary creations of humans?

Fundamental units of living things?Fundamental units of living things?

Who recognizes species and how?Who recognizes species and how?

How do you define a species withHow do you define a species withincontrovertible limits?incontrovertible limits?


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Species ConceptsSpecies Concepts

TypologicalTypological

MorphologicalMorphological

BiologicalBiological

EvolutionaryEvolutionary

Typological Species ConceptTypological Species Concept

Clusters of individuals closely resembling eachClusters of individuals closely resembling each

other reflecting Godother reflecting Gods plan of nature.s plan of nature.

A fixed group of organisms that vary from an idealA fixed group of organisms that vary from an ideal

typetypethat was Godthat was Gods original blueprint.s original blueprint.

Recognition of such things as sexual dimorphismRecognition of such things as sexual dimorphism

and life stagesand life stages

Recognition of groups more closely related suchRecognition of groups more closely related suchas generaas genera

OverOver--splitting tendencysplitting tendency


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Pertinence of Typological ConceptPertinence of Typological Concept

LinneasLinneasss conceptconcept

International codes of zoologicalInternational codes of zoologicaland botanical nomenclature requireand botanical nomenclature requirea type specimen, illustrated.a type specimen, illustrated.

Concrete reference point forConcrete reference point forsystematicssystematics and identification ofand identification ofspecies.species.

Holotype ofYnezidinium malloyi


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Morphological Species ConceptMorphological Species Concept

A diagnosable cluster of individuals withinA diagnosable cluster of individuals withinwhich there is a pattern of ancestry andwhich there is a pattern of ancestry and

descent, and beyond which there is not.descent, and beyond which there is not.

Joel CracraftNiles Eldredge1943- 1942-

Morphological Concept of SpeciesMorphological Concept of Species

Similarity of form; inference of ancestrySimilarity of form; inference of ancestry

Must recognize sexual dimorphism andMust recognize sexual dimorphism and

other variationsother variations

Use of the population concept of a speciesUse of the population concept of a species

lessenslessens oversplittingoversplitting


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Pertinence of Variations withinPertinence of Variations within

SpeciesSpecies DarwinDarwins view of speciess view of species

Species viewed as part of a populationSpecies viewed as part of a population

that varied continuously.that varied continuously.

When group varies enough from ancestor,When group varies enough from ancestor,

new species (speciation)new species (speciation)

Variation is the stuff of evolutionVariation is the stuff of evolution

Some species continually split into newSome species continually split into newspeciesspecies

Darwins illustration of splitting from a single stem in two species


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Biological Species ConceptBiological Species Concept

An array of populations that are actuallyAn array of populations that are actually

or potentially interbreeding, and that areor potentially interbreeding, and that are

reproductively isolated from other suchreproductively isolated from other such

arrays under natural conditions.arrays under natural conditions.

Wider than population.Wider than population.

Interbreeding in fact.Interbreeding in fact.

Test of interbreedingTest of interbreeding hybrids, fossilshybrids, fossils


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Evolutionary Species ConceptEvolutionary Species Concept

Lineage evolving separately from othersLineage evolving separately from others

with its own unitary evolutionary role andwith its own unitary evolutionary role and

tendencies.tendencies.

Branching points in theBranching points in thefamily treefamily treeoror

evolution.evolution.

Key characteristics that separate theKey characteristics that separate the

species while allowing for variation and forspecies while allowing for variation and for

unity with the genus.unity with the genus.

Two species of dinoflagellate cystAreosphaeridium


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Process variations between species ofdinoflagellate cystAreosphaeridium


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Branching Bush with Gradualism

SPECIATIONSPECIATION

How do you get from one species toHow do you get from one species to

anotheranotherThe origin of speciesThe origin of species(Darwin(Darwin

doesndoesnt tell you exactly)t tell you exactly)

SympatricSympatric change within a populationchange within a population

Example:Example:AreosphaeridiumAreosphaeridium

AllopatricAllopatric change only with isolation ofchange only with isolation ofpart of populationpart of population


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Sympatric SpeciationSympatric Speciation

DarwinDarwins view plus geneticss view plus genetics

Mutation andMutation andmutation pressuremutation pressure

High competition and selective pressureHigh competition and selective pressure

eliminating the unfiteliminating the unfitsurvival of the fittestsurvival of the fittest

TheThegene poolgene poolis altered through time.is altered through time.

Sympatric evolution corresponding to environmental change


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The Problem of DilutionThe Problem of Dilution

Gene flow within an interbreedingGene flow within an interbreeding

populationpopulation

Advantageous mutations would be dilutedAdvantageous mutations would be diluted

by interbreeding with normal individuals ofby interbreeding with normal individuals of

the population and disappear.the population and disappear.

Importance of theImportance of theperipherally isolatedperipherally isolated

populationpopulation studies of 1940studies of 1940, 1950, 1950ss

Allopatric speciation corresponding to isolation


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AllopatricAllopatric SpeciationSpeciation

Ernst Mayr 1904-20054 Stages (see p. 42 text)

1. Large population in homogeneous environment

2. Differentiation of environment or migration leads to subspecies

3. Further D and M leads to geographic isolation of subsp. or race

4. Reintroduction of isolated and main pop. cant interbreed.

Widespread Agreement

Founders, Clines and RingsFounders, Clines and Rings

Founder speciesFounder species Individuals isolated byIndividuals isolated bychance that create a new gene pool whichchance that create a new gene pool whichmay diversify e.g. Darwinmay diversify e.g. Darwins finchess finches

ClinesClines Gradient in features within aGradient in features within aspecies over space or timespecies over space or time

Ring speciesRing species Cline over spaceCline over space

((biogeographicbiogeographic) that results in failure of) that results in failure ofend members to interbreed, e.g. Europeanend members to interbreed, e.g. Europeangulls.gulls.


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Types of IsolationTypes of Isolation

GeographicGeographic oceans, mountain rangesoceans, mountain ranges

BehaviorsBehaviors

Distinct nichesDistinct niches

Feeding habits (DarwinFeeding habits (Darwins finches)s finches)

Small gene pool (e.g. tide pools)Small gene pool (e.g. tide pools)

ParasitesParasites

SPECIES IN PALEONTOLOGYSPECIES IN PALEONTOLOGY

any of that large class of objects ofany of that large class of objects of

organic origin that are of sufficientlyorganic origin that are of sufficiently

distinctive and consistent morphology sodistinctive and consistent morphology so

that a competent paleontologist couldthat a competent paleontologist could

define them so that another competentdefine them so that another competent

paleontologist could recognize them.paleontologist could recognize them.

Alan Shaw, 1964Alan Shaw, 1964

Time inTime inStratographyStratography


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Problems of Species inProblems of Species in

PaleontologyPaleontology CanCant demonstrate interbreedingt demonstrate interbreeding

CanCant use behavioral criteria (siblingt use behavioral criteria (siblingspecies)species)

Sexual dimorphismSexual dimorphism

The dimension of time in PaleontologyThe dimension of time in Paleontology

The Dimension of TimeThe Dimension of Time

AnagenesisAnagenesis PhyleticPhyletic evolution within a lineage.evolution within a lineage.

PhyleticPhyletic GradualismGradualism Gradual change with timeGradual change with time

of one species to another (speciation)of one species to another (speciation)

End members are clearly different speciesEnd members are clearly different species

Gradual changes make it difficult (impossible?) toGradual changes make it difficult (impossible?) to

draw the line between the two speciesdraw the line between the two species

Biologists (neontologists) donBiologists (neontologists) dont have thist have thisproblemproblem


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A selection ofMicrasters (species) viewed apically.


BiostratigraphyBiostratigraphy

Donald Weaver:Donald Weaver:

The finer you can cut your taxonomy, theThe finer you can cut your taxonomy, the

finer you can cut yourfiner you can cut your stratigraphystratigraphy


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Evolutionary Species concept ofEvolutionary Species concept of

G.G.SimpsonG.G.Simpson

Species defined by branching pointsSpecies defined by branching points

A single lineage=speciesA single lineage=species

Branch points relatively objectiveBranch points relatively objective

Punctuated EquilibriumPunctuated Equilibrium

Stephen J. Gould1941-2002

Niles Eldredge1943-


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Paleontologists had been conditioned toPaleontologists had been conditioned to

look forlook for anageneticanagenetic series of changes andseries of changes and

blame the imperfection of the record whenblame the imperfection of the record when

they did not appear. (Darwin)they did not appear. (Darwin)

PhyleticPhyletic GradulaismGradulaism ((anagenesisanagenesis ofof

species) is actually rare.species) is actually rare.


Stasis is the ruleStasis is the rule

Species remain the same for long periodsSpecies remain the same for long periods

of time.of time.

Suddenly a new species appears.Suddenly a new species appears.

IfIfanagenesisanagenesis is rare (or doesnis rare (or doesnt exist),t exist),

then problem of dividing speciesthen problem of dividing speciesdisappears.disappears.


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Phyletic Gradualism vs. Punctuated Equilibrium

TIME

Phyletic Gradualism Punctuated Equilibrium

I. cingulatum

Y. malloyi


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I. cingulatum Y. malloyi

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Pal Chapter 3 Species and Speciation