Bio1B Evolution 9Last lecture:Evolution of sacrifice (altruism)Species & speciation• What is a species anyway? (Pp. 487-492)– Reproductive isolation - mechanismsTodaySpecies & speciation• What is a species anyway? (Pp. 487-492)– Concepts - typological, biological, phylogenetic– Reproductive isolation - mechanisms– E.g. Humans & relatives, Ensatina = ring spp.Speciation processes (Pp 492-504)• Introduction & geographic modes• The DM model – postzygotic isolation• Adaptive radiationsWhat is a species?Typological (pre-evolutionaryeg. Aristotle, Linnaeus)EvolutionaryDiscontinuities:DWM + extinctionMorphological SCReproductiveisolationBiological SCCharacterchangePhylogenetic SCNeoDarwinists Systematists DarwinGroups of populationsreproductively isolatedfrom othersDiagnosable clusterswith commonancestry (molecularor morphological)Phenotypically distinctsets of populationsReconciling different perspectivesForms of Reproductive Isolation•Prezygotic– Separation of mating• Habitat, Timing, Behavior, Mechanical•Gamete recognition•Postzygotic– Viability (F1 or later), FertilityGeneral lineage concept: focuseson the process - not how torecognize speciesIncreasing RI &phenotypic divergencePostzygotic RIincreases withgenetic divergencealso Fig. 17.5Species of HominidaePygmychimpEnsatina eschscholtzii - One ring species? Or 2biological species? Or >11 Phylogenetic speciesk-e overlap;no hybridsk-e overlap;hybridsGeographic modes of speciationFutuyma 2005exiguusaenigmabombienssaxatilisconcinnusmonticolahosmeriexiguus v aenigma• 5% mtDNA divergence• Large body size & lowerfreq. call in aenigmaconcinnus v monticola• 5% mtDNA divergence•concinnus has lower & longercall, distinct morphologyAllopatric sister species among northern, montane Cophixalus (Hoskin 2004)Parapatric evolution ofreproductive isolation overa very short distance in thegrass speciesAnthoxanthum odoratumFutuyma 2005Sympatric speciation on remote islands:eg. Lord Howe Island palms (Howea) Savolainen et al. 2006 Nature441:210-214Recently (<1Mya) formedsister species - ecologicallydistinct and with divergentflowering time - despite highgene flow across the range ofeach species on the islandCalcareous soilsFlowering timePeripatric speciation: paradise-kingfishersin New Guinea (Mayr)Futuyma 2005Processes: Founderevent, drift,
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