Download Evolution

Species Concept
and
Speciation Process
Recognizable ‘Kinds’ of Organisms
Species?
Taxonomy: dealing with variation
• The scientist Linnaeus (17071778) sought to classify
organisms in an organized way to
more easily study and keep track
of them.
• He also practiced medicine and
specialized in syphilis
• Binomial nomenclature
– Genus species
Who cares about this?
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Taxonomists
Conservation biologists
CITES, wildlife regulatory agencies
Politicians and developers?
• Epizootiologists and Epidemiologists
• Journal Clubs?
Species?
Head and Body Lice
Are the two separate species? The scientific name of
the lice can be found either way in the in the
literature:
Pediculus humanus humanus
Pediculus humanus capitus
Or
Pediculus humanus
Pediculus capitus
The two taxa of lice are virtually indistinguishable
morphologically except that the body louse is slightly
larger than the head louse.
Body lice seem to be more important in the
transmission of diseases (such as epidemic typhus)
than head lice
Concept of Species
• What is a Species?
• How does this concept fit into bioscience?
– Systematics, ecology and evolution
– Does the concept of species represent a testable hypothesis?
• Is a single concept universal (apply to all life forms)?
• Are there many concepts?
The Biological Species Concept
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AKA the isolation concept
Championed by Ernst Mayr
Widely accepted by zoologists and botanists
Basically states that:
– lack of gene flow leads to divergence between
populations
– reproductive isolation is test of separate species
status i.e. different species can not interbreed
Problems with the biological
species concept
• Can’t be applied to many organisms
– Asexual organisms
– Bacteria
• Links concept to a limited number of speciation
processes
• Overemphasis on gene flow
– Some distinct populations can, but do not interbreed
because of factors such as behavior or distribution
– Some sympatric individuals can’t interbreed but
natural selection maintains continuity in population
Reproductive isolation?
Wolbachia spp. is a
bacterium that affects
the reproduction of
mosquitoes
Infected mosquitos limited to breeding
with other infected mosquitos
Reproductive Isolation
Fossil Species
Change in populations
Speciation
• Speciation results after heritable changes occur to such
an extent that populations of organisms form separate,
significantly different(?) clades. (cladogenesis)
• Mechanisms
– Genetic drift, hybridyzation,various incompatibilities
genetic& behavioral etc..
– Natural Selection
• Modes of speciation
– Allopatric
– Peripatric
– Sympatric
Fig. 12.20
Evolution of Populations
Spectrum of characteristics in population
Original
population
Population after
selection
Different selection processes
Divergence in Population
Some other species concepts
• Taxonomic species concepts
– Morphospecies
– Genospecies
– Phylogenetic species
• Recognition Concept
• Cohesion Concept
Using DNA to classify species
Bioinformatics is a new field involving the
use of technology to evaluate biological data
BioNumerics-Applied Maths