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ADVANCED MICROBIOLOGY

Definition:• The emergence of reproductively isolated sub-population from or

within an original interbreeding population• Evolution of the species

SPECIATION

often associated with the accumulation of geneticdifferences, may not be expressed asmorphological variation.

Many evidence showing that:In one morphospecies occurred totally reproductively isolated group

A. Single population with homogenousenvironment

B. Differentiation of environment andmigration to new environmentproduce differentiation of races andsubspecies

C. Further differentiation and migration

A

B

C

D

SEQUENCE OF EVENTS FOR SPECIATION

produces geographic isolation ofsome races and subspecies.

D. Isolated subspecies differentiate withrepect to their genom that controlreproductive isolation

ILLUSTRATION

Fig 4. Northward spread of black rust on wheat ( as a resultof urediniaporedipersal by air current)

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COMPONENTS OF THE SPECIATION:1.2.3.4.

The original interbreeding populationGenetic SystemNatural selectionReproductive isolation

1. THE ORIGINAL INTERBREEDING POPULATION

Basal population structure:1. Highly heterogenous

2. Sexual outcrossing and vegetatively incompatible.

Population potential for speciation

Basal Population:

Definition of Population :• Numerical size: 11 colony/ g soil• Geographic size or distribution: local or global• Genetic Structure: number of vc groups as in fig. above, maintain

territorial integrity, promote mutual antagonism and territorial invasion

Population of (morethan 40 vc groups)Ophiostoma ulmi on11 x 16 cm wood ofelm tree.

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2. GENETIC SYSTEM: SOURCE OF VARIATION

Heterotalism vs. Homotalism

Secondary HomotalismsParasexualism

Mutation

Clonal Reproduction

Acts on interbreeding population viastages:

Aspects1. Substrate or host2. Vectors3. Climate4. Competitor5. Predator

Routine selection

Maintenance ofstable population

many aspects and during many

Stages1. Spore germination2. colonization3. consolidation4. fruiting5. spore dispersal6. resting

Episodic selection

Breakdown of basalpopulation structure

ILLUSTRATION:

natural selection as directive, stabilize or disruptive against basalpopulation structure.

• Routine natural selection ------- Heterothalism• Episodic natural selection --------Homothalism

In one morphospecies: heterothalism and homothalism may occur.Example:

Achlya homothalic dan heterothalic individu may occur

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Growth rate (mm/10 da)

Individue has gene combination suits to environmental conditionwill survive (red shadow).

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40 60 80 100 120

in permanent pond

homothalic population, low population intemporary pond

Experiments on natural selection

of divergence of orginal interbreeding population at the samegeographic location

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Wild dikaryon

Synthetic dikaryons20

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GRADUAL NICHE DIVERGENCEAND DESRUPTIVE SELECTION

Sympatric mode of selection:

• initiated in interbreeding population confronted with two ecological nice

• Force the individual in the population to shift gradually (stablepolymorphism) ---- destruptive

1. Ecological niche:Typhula ishikariensis (kapang salju)

3 biotypes, A established in inlandB in coastal region

reproductivelyisolated

C is similar to B but with inland –coastaldistribution

2. Nutritional strategies:• Mucor mucedo inhabits rodents dung• M. pyriformis common on rotting fruits

• Neurospora intermedia :2 subpopulations:

‘yellow giant’ on food and food wastesin E and SE Asia

‘tipe standard’ on burned substratein the tropic

• Lophodermium pada Pinus3 subpopulations:

penghuni serasahpenghuni daun jarum yang hijaupenghuni daun jarum yang mati

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Isolated

Isolated

Isolated

ALOPATRIC

• Subpopulation being separated bygeographic barrier followed byreproductive isolation

• Not main speciation in fungi

SYMPATRIC

• Subpopulation being isolated withinthe original population for its naturalselection or genetic barrier

• Main species means in fungalspeciation

REPRODUCTIVE ISOLATION

Genetic changes continuously, cause subpopulations not being able to mateand the subpopulations develop into a new species.

Factors stimulate reproductive isolation:Geographic barrierNiche ecology isolationgenetic barrier

ALOPATRIC VS SYMPATRIC SPECIATION

GENETIC BARRIER

•PREZIGOTIC ISOLATION:•Gamete production and its release in different time

Coelomyces dodgei dan C. punctatusPhytophthora spp.

•Plasmogamic or heterokaryotic failureCoprinus spp., Armilaria spp. , Aspergillus nidulans

POST ZYGOTIC ISOLATION:•Zygote abortion:

Phytophthora megakarya dan P. palmivora asal pohon coklatAble to mate but zygote unable to develop

•Post meiotic genetic disturbance:Neurospora intermedia:perithecium has empty asci or only some asci has ascospores.

•Sterile hybrid:P. meadii (hybrid Phytopthora indigenous x P. palmivora (in rubber) di India) sterile

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