Species Concept and Speciation Process

Recognizable ‘Kinds’ of Organisms

Species?

Taxonomy: dealing with variation The scientist Linnaeus (1707-1778) 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? 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 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 Population after selection Different selection processes Original population

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