1Bio1B Evolution 9Last lecture:Evolution of sacrifice (altruism)Species & speciation• What is a species anyway? (Pp. 487-492)– Concepts - typological, biological, phylogenetic– Reproductive isolation - mechanisms– Easy one? - Humans & living relativesTodaySpecies & speciation• What is a species anyway? (Pp. 487-492)– Interesting one - Ensatina salamanders• Speciation processes (Pp 492-504; Losos & Rickleffs (2009) paper -• Introduction & geographic modes• Adaptive radiations• Hybridization - hybrid zones, reinforcement & hybrid-speciation2Ensatina eschscholtzii - One ring species? Or 2biological species? Or >11 Phylogenetic speciesk-e overlap;no hybridsk-e overlap;hybrids3Geographic modes of speciationFutuyma 20054exiguusaenigmabombienssaxatilisconcinnusmonticolahosmeriexiguus 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)5Parapatric evolution ofreproductive isolation overa very short distance in thegrass speciesAnthoxanthum odoratumFutuyma 20056Sympatric 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 time7Peripatric speciation: paradise-kingfishersin New Guinea (Mayr)Futuyma 2005Processes: Founderevent, drift, selection?8Adaptive radiations (pp. 524-5)• Rapid speciation withecologically-drivendivergent selection• Common on remoteislands or other novelenvironmentsfollowing colonization• Promoted by isolation& ecologicalopportunitye.g. Hawaiian silverswords(Fig. 25.18)Other examples: African cichlids,Hawaiian arthropods, Andeanlupines, Carribean anole lizards etcetc9Speciation onislands:Losos &Rickleffs2009Adaptivedivergenceamong orwithin islandsAdaptive divergenceof bill dimensionslengthwidth & depth10Hybrid zones - alternative outcomesOr, new “hybrid species”Fig. 24.1411Hybrid zone - Bombina variegata-bombina (Fig. 24.13)12A stable hybridzone inEnsatinaAlexandrino et al. 200520 yrslater13Recent (<8kya) expansion from long-isolated (>2 Myr)refugia in the NE Australian rainforestIs there evidence forreproductive isolation?Is there evidence forreinforcement =>prezygotic isolation?ManyhybridzonesSkink = narrow (<1km) hybridzone - random mating, but someselection against hybridsSmall marsupial - randommating, hybrid swarmFrog - reinforcement =>Reproductive isolationMoritz et al.2009 PRSL1415Hybrid speciation=> Formation of unique andisolated lineages from inter-lineage hybrids• Allopolyploidy (see p. 496)• If same ploidy, requires eco-geographic isolation fromparent lineages• E.g. arid-adapted Helianthusanomalus = H.annuus X H.petiolarisFig 24.18, p. 50316Adaptive shifts via hybridization:diploid vs polyploidReview: Mallet2007, Nature446:279-283PhenotypePolyploidhybridParentspecies 2Parentspecies
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