Bio1B Evolution 9 Last lecture: Evolution of sacrifice (altruism) Species & speciation • What is a species anyway? (Pp. 487-492) – Concepts - typological, biological, phylogenetic – Reproductive isolation - mechanisms Today Species & speciation • What is a species anyway? (Pp. 487-492) – Interesting one - Ensatina salamanders – Easy one? - Humans & living relatives • Speciation processes (Pp 492-504) • Introduction & geographic modes • Adaptive radiations • Hybridization - hybrid zones, reinforcement & hybrid- speciation 1 Species of Hominidae Pygmy chimp 2 Ensatina eschscholtzii - One ring species? Or 2 biological species? Or >11 Phylogenetic species k-e overlap; k-e overlap; hybrids no hybrids 3 Geographic modes of speciation Futuyma 2005 4 Allopatric sister species among northern, montane Cophixalus (Hoskin 2004) exiguus v aenigma exiguus • 5% mtDNA divergence aenigma • Large body size & lower freq. call in aenigma bombiens saxatilis concinnus v monticola concinnus • 5% mtDNA divergence monticola •concinnus has lower & longer call, distinct morphology hosmeri 5 Parapatric evolution of reproductive isolation over a very short distance in the grass species Anthoxanthum odoratum Futuyma 2005 6 Sympatric speciation on remote islands: eg. Lord Howe Island palms (Howea) Savolainen et al. 2006 Nature 441:210-214 Recently (<1Mya) formed sister species - ecologically distinct and with divergent flowering time - despite high gene flow across the range of each species on the island Flowering time Calcareous soils 7 Peripatric speciation: paradise-kingfishers in New Guinea (Mayr) Processes: Founder event, drift, selection? Futuyma 2005 8 Adaptive radiations (pp. 524-5) • Rapid speciation with ecologically-driven divergent selection • Common on remote islands or other novel environments following colonization e.g. Hawaiian silverswords • Promoted by isolation (Fig. 25.18) & ecological Other examples: African cichlids, Hawaiian arthropods, Andean opportunity lupines, Carribean anole lizards etc etc 9 Adaptive divergence of bill dimensions Speciation on islands: Losos & Rickleffs length 2009 width & depth Adaptive divergence among or within islands 10 Hybrid zones - alternative outcomes after re-contact between lineages Fig. 24.14 Or, new “hybrid species” Or - lineages don’t hybridize and eventually overlap if ecologically distinct 11.