Evolutionary Biology BIOL 3350 Dr Lisa Rapaport Lecture 15 Part 1 Notes What Is A Species I II Biological Species Concept Advantages A Intuitive conceptual makes sense that two different breeds could not breed with each other B Complete lack of gene flow no gray areas C Two main processes where species become isolated from each other and speciation occurs over time genetic drift and natural selection Biological Species Concept Disadvantages A Allopatric they are separated by space or time if they are not in the same place at the same time then they cannot interbreeding with each other B Fossil cannot tell if they are the same or different species because we do not know if they interbred C Hybridizing two different parents so which species does the hybrid D Asexual parthenogenic females produced eggs that are clones of just themselves no DNA from the males are females then a species of their own E Biological species concept does not take into account the evolutionary belong to process III Morphospecies Concept A Some species designations may be arbitrary because some species have a lot of phenotypic differences but some do not have a lot of morphological differences like bacteria and fungi where do we draw this distinction line B Sometimes groups will look very similar as a result of similar adaptations but it will not reflect similarity in ancestry C Phylogeny of lizards and snakes based on morphospecies concept 1 Relies on physiological adaptions for diet 2 Reliance on tongue and vision considered to be ancestry Adaptations 3 Revised Phylogeny of Lizards and Snakes 4 Relies on DNA analyses evolution of venom glands through molecules structure of proteins IV Phylogenetic Species Concept A Each letter represents a different clade B Each group with the same letter represents different populations on the same species C Clades are groups that are related to each other D When populations become isolated they diverge genetically through genetic drift and or natural selection 1 1 Diagnostic traits will evolve overtime E Phylogenetic species concept does not give us specific characteristics to use when defining species V Gray Treefrog Speciation A H versicolor and H chrysoscelis cannot mate with each other and produce fertile offspring B They are now behaviorally isolated through their mating calls C Females of the one species are not attracted to the calls of the males of the other species D Biological species concept says they are different E H versicolor was formed by different parental species Modes of Speciation A When they were part of the same population they could interbreed with each other Reduction in Gene Flow A When gene flow is cut off between 2 populations genetic drift and natural selection causes the populations to differentiated from each other overtime VIII Isolation in sympatry A If much of the area is different between the 2 populations species A may be adapting to different aspects than species B and vice versa IX Premating isolation mechanism A They may overlap in their distribution but they differ in their microhabitats so they do not hybridize B Spatial separation one species may breed in a marsh while the other breeds in open water area C Temporal separation one breeds early in the summer while the other breeds late in the summer never get to mate D Behavioral isolation different social behavior E Mechanical isolation common in reptiles and insects the shapes of the reproductive organs are usually very species to each species Postmating isolating mechanisms A Example of hybrid sterility mules B Hybrid inviability may have higher mortality or low fertility making it less fit than the non hybrid individuals VI VII X 2