1 Bio1B Evolution 9 Last lecture: Evolution of sacrifice (altruism) Species & speciation • What is a species anyway? (Pp. 487-492) – Reproductive isolation - mechanisms Today Species & 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 radiations What is a species? Typological (pre-evolutionary eg. Aristotle, Linnaeus) Evolutionary Discontinuities: DWM + extinction Morphological SC Reproductive isolation Biological SC Character change Phylogenetic SC NeoDarwinists Systematists Darwin Groups of populations reproductively isolated from others Diagnosable clusters with common ancestry (molecular or morphological) Phenotypically distinct sets of populations Reconciling different perspectives Forms of Reproductive Isolation • Prezygotic – Separation of mating • Habitat, Timing, Behavior, Mechanical • Gamete recognition • Postzygotic – Viability (F1 or later), Fertility General lineage concept: focuses on the process - not how to recognize species Increasing RI & phenotypic divergence Postzygotic RI increases with genetic divergence also Fig. 17.52 Species of Hominidae Pygmy chimp Ensatina eschscholtzii - One ring species? Or 2 biological species? Or >11 Phylogenetic species k-e overlap; no hybrids k-e overlap; hybrids Geographic modes of speciation Futuyma 20053 exiguus aenigma bombiens saxatilis concinnus monticola hosmeri exiguus v aenigma • 5% mtDNA divergence • Large body size & lower freq. call in aenigma concinnus v monticola • 5% mtDNA divergence • concinnus has lower & longer call, distinct morphology Allopatric sister species among northern, montane Cophixalus (Hoskin 2004) Parapatric evolution of reproductive isolation over a very short distance in the grass species Anthoxanthum odoratum Futuyma 2005 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 Calcareous soils Flowering time4 Peripatric speciation: paradise-kingfishers in New Guinea (Mayr) Futuyma 2005 Processes: Founder event, drift,
View Full Document
Unlocking...