Ecology and the origin of species
Overview: Part I Patterns What is a species? What is speciation? Mechanisms of reproductive isolation How does it happen? Spatial and temporal patterns Stages of speciation
The origin of species - that mystery of mysteries Darwin (1859) The Origin of Species. some of the varieties producing only a single variety, but in a more and more modified condition, some producing two or three varieties, and some failing to produce any.
The origin of species = the origin of reproductive isolation How could a continuous evolutionary process changes in allele frequency produce genetically and morphologically discrete groups living in one habitat? Dobzhansky (1937) Genetics and the Origin of Species. Mayr (1942) Systematics and the Origin of Species. Speciation is not the divergence into new niches but, ultimately, the origin of reproductive isolation. The Biological Species Concept (BSC):
Reproductive Isolating mechanisms Nosil et al. (2005) Evolution 59: 705-719.
Reproductive isolating mechanisms: premating, prezygotic barriers Seehausen & van Alphen (1999) Ecol. Lett. 2: 262-271. Fulton & Hodges 1999 Proc. Roy. Soc. B 266: 2247-2252. Cichlid Pundamilia pundamilia Columbine Aquilegia formosa A. pubescens Cichlid Pundamilia nyererei
Reproductive isolating mechanisms: postmating, prezygotic barriers Fricke & Arnqvist (2004) J. Anim. Behav. 67: 729-732. Tribolium flour beetle
Reproductive isolating mechanisms: postmating, postzygotic barriers Intrinsic (genetic) postzygotic isolation 1 Naisbit et al. (2002) Genetics 161: 1517-1526. Hatching rate 0.5 0 H. Cydno (Hc) H. Melpomene (Hm) Hm x Hc Heliconius melpomene F1 x Hc or Hm H. cydno
Reproductive isolating mechanisms: postmating, postzygotic barriers Extrinsic (ecological) postzygotic isolation Rundle (2002) Evolution 56: 322-329.
Reproductive isolating mechanisms: postmating, postzygotic barriers Extrinsic (ecological) postzygotic isolation Rundle (2002) Evolution 56: 322-329. Littoral Zone Open water Threespine stickleback, Gasterosteus aculeatus
Overview: Part I Patterns What is a species? What is speciation? Mechanisms of reproductive isolation How does it happen? Spatial and temporal patterns Stages of speciation
Geographical patterns of speciation Allopatric Sympatric vicariant event or dispersal cladogenesis Time
Geographical patterns of speciation Allopatric Sympatric vicariant event or dispersal cladogenesis Time Range overlap Range movements Time Range overlap Time since split Time since split
Geographical patterns of speciation Predictions Allopatric Degree of sympatry Barraclough & Vogler (2000) Am. Nat. 155: 419-434. Range overlap Time since split Sympatric Degree of sympatry (range overlap) most speciation is allopatric Range overlap Time since split Time since split
Allopatric patterns of speciation: vicariance Isthmus of Panama Pacific Caribbean Knowlton & Weigt (1998) Proc. Roy. Soc. B 265: 2257-2263. Snapping shrimps, Alpheus
Allopatric patterns of speciation: dispersal Cuban members of the carolinensis subgroup Non-Cuban members of the carolinensis subgroup Glor et al. (2005) Mol. Ecol. 14: 2419-2432. Anolis carolinensis
Allopatric patterns of speciation: area Losos & Schluter (2000) Nature 408: 847-850. Anolis lizards on Caribbean islands
Allopatric patterns of speciation: area Number of islands Number of species Grant & Grant (1996) Phil. Soc. Trans. Roy. Soc. 351: 765-772. Finches from the Galapagos Islands
Sympatric patterns of speciation Criteria required to provide convincing evidence: Via (2001) Trends in Evol. Ecol. 16: 381-390. Coyne (2007) Current Biology. 17: R787-788.
Sympatric patterns of speciation Apple maggot fly, Rhagoletis pomonella Native host Non-native host for about 150 years Feder 1998 in Howard & Berlocher (eds) Endless Forms OUP. Hawthorn Apple
Sympatric patterns of speciation Midas cichlids Amphilophus spp. benthic limnetic Barluenga et al. (2006) Nature 439: 719-723. pharyngeal jaws
Spatio-temporal patterns of speciation: ring species Greenish warbler Phylloscopus trochiloides Irwin et al. (2001) Nature 409: 333-337. Irwin et al. (2005) Science 307: 414-416. Geographic variation in song
Spatio-temporal patterns of speciation: ring species Irwin et al. (2001) Nature 409: 333-337. Irwin et al. (2005) Science 307: 414-416. Geographic variation in genetics Genetic differences between subspecies, with the two most northerly groups being most distinct.
Temporal patterns of speciation Silene spp. Moyle et al. (2004) Evolution 58: 1195-1208. Coyne & Orr (1997) Evolution 51: 295-303. Drosophila spp. Reproductive isolation increases over time.
Temporal patterns of speciation Drosophila spp. Coyne & Orr (1997) Evolution 51: 295-303. Prezygotic RI evolves faster/ is stronger than intrinsic postzygotic RI.
Temporal patterns of speciation Prezygotic RI is stronger between sympatric than allopatric taxa. Coyne & Orr (1997) Evolution 51: 295-303.
Temporal patterns of speciation Prezygotic RI is stronger between sympatric than allopatric taxa. Selection against unfit hybrids produced in sympatry (extrinsic post-zygotic isolation) will strengthen prezygotic isolation Coyne & Orr (1997) Evolution 51: 295-303. (e.g. mate choice): Reinforcement.
Stages of speciation: reinforcement Rundle (2002) Evolution 56: 322-329. Gow et al. (2007) J. Evol. Biol. 20: 2173-2180. Benthics Threespine stickleback, Gasterosteus aculeatus 1 cm Limnetics Experimental and observational work shows that hybrids are less fit than parent species. Are sympatric species more choosey in their mate choice than similar allopatric ones (as predicted by reinforcement)?
Stages of speciation: reinforcement Priest limnetic Beaver lake Priest benthic Rundle & Schluter (1998) Evolution 52: 200-208. Salmon river limnetic male benthic male benthic Allopatric females show no discrimination in mate choice between benthic and limnetic males but sympatirc benthic females do discriminate; they are unwilling to mate with sympatric limnetics. Suggests selection on mate choice in sympatry (reinforcement).
Stages of speciation What is speciation? The evolution of reproductive isolation (RI) How does it happen? RI accumulates over time Spatial element: allopatry, sympatry, reinforcement Schluter (2001) Trends in Evol. Ecol. 16: 372-380. Level of reproductive isolation 0% 100% Allopatric phase By-product mechanism Sympatric phase Reinforcement
Speciation References RI mechanisms: Spatial & temporal Patterns: Fricke & Arnqvist (2004) J. Anim. Behav. 67: 729-732. Fulton & Hodges 1999 Proc. Roy. Soc. B 266: 2247-2252. Naisbit et al. (2002) Genetics 161: 1517-1526. Nosil et al. (2005) Evolution 59: 705-719. Rundle (2002) Evolution 56: 322-329. Seehausen & van Alphen (1999) Ecol. Lett. 2: 262-271. Barluenga et al. (2006) Nature 439: 719-723. Barraclough & Vogler (2000) Am. Nat. 155: 419-434. Coyne (2007) Current Biology. 17: R787-788. Coyne & Orr (1997) Evolution 51: 295-303. Feder 1998 in Howard & Berlocher (eds) Endless Forms OUP. Glor et al. (2005) Mol. Ecol. 14: 2419-2432. Gow et al. (2007) J. Evol. Biol. 20: 2173-2180. Grant & Grant (1996) Phil. Soc. Trans. Roy. Soc. 351: 765-772. Irwin et al. (2001) Nature 409: 333-337. Irwin et al. (2005) Science 307: 414-416. Knowlton & Weigt (1998) Proc. Roy. Soc. B 265: 2257-2263. Losos & Schluter (2000) Nature 408: 847-850 Moyle et al. (2004) Evolution 58: 1195-1208. Rundle (2002) Evolution 56: 322-329. Rundle & Schluter (1998) Evolution 52: 200-208. Schluter (2001) Trends in Evol. Ecol. 16: 372-380. Via (2001) Trends in Evol. Ecol. 16: 381-390.