Speciation 1 Brian O’Meara EEB464 Fall 2015 .
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Transcript of Speciation 1 Brian O’Meara EEB464 Fall 2015 .
Speciation 1
Brian O’MearaEEB464 Fall 2015
http://www.youtube.com/watch?v=lopTMhAbXoI
Initiation of speciation
Maintenance of current species
Prezygotic
Postzygotic
Zygote image © Laboratoire de Biologie de la Reproduction; Lausanne, image downloaded from http://www.embryology.ch/anglais/evorimplantation/furchung01.html
Prezygotic
Postzygotic
Zygote image © Laboratoire de Biologie de la Reproduction; Lausanne, image downloaded from http://www.embryology.ch/anglais/evorimplantation/furchung01.html
• Physical or temporal isolation
• Lack of proper mating cues• Mechanical problems• Gametic problems
• Hybrid inviability• Hybrid sterility
Physical or temporal isolation
Wikimedia commons
Lack of proper mating cues
From BBC Planet Earth
Mechanical problems
Fleur Champion de Crespigny via National GeographicJohanna L. Rönn/Uppsala University via National Geographic
Gametic problems
Ludlow, A.M. & A.E. Magurran. 2006. Gametic isolation in guppies (Poecilia reticulata). Proc. Biol. Sci. 273(1600):2477-2482
Wibowo Djatmiko
Hybrid inviability
Crosses of green toads from Sicily. a: Cross B. balearicus female × B. siculus male; b: reciprocal cross B. siculus × B. balearicus;
f: in the age of two months (from left to right): retarded tadpole, "giant" leucistic tadpole with developmental arrest, malformed dwarfed tadpole, leucistic tadpole that turned later out to be incapable of metamorphosis, apparently normally metamorphosing tadpole;
c-d: offspring in the age of seven days, showing dead and malformed embryos and tadpoles in comparison with apparently normally developing ones; e: about one-months old normal tadpole (left) in comparison with leucistic "large" tadpole (right);
g: adult, two-year-old F1-male;h: adult, two-year-old F1-female.
Photographs: M. Stöck.
Colliard et al. Strong reproductive barriers in a narrow hybrid zone of West-Mediterranean green toads (Bufo viridis subgroup) with Plio-Pleistocene divergence.
BMC Evol Biol (2010) vol. 10 pp. 232
Dobzhansky-Muller Incompatibilities
How can genes evolve within a species neutrally
but still lead to hybrid inviability/sterility?
Think of the ancestral species being genotype
AA BB
Speciation
Allopatric Parapatric Sympatric
Allopatric Sympatric
Prezygotic
Physical or temporal isolation
Lack of proper mating cues
Mechanical problems
Gametic problems
Postzygotic
Hybrid inviability
Hybrid sterility
Sympatric speciation has always fascinated evolutionary biologists, and
for good reason; it pits diversifying selection directly against the
tendency of sexual reproduction to homogenize populations. ... The
most precise definitions make sympatric speciation an infinitesimal end
point of a continuum. Because it is virtually impossible to demonstrate
the occurrence of such a theoretical extreme, we argue that testing
whether a case fits a particular definition is less informative than
evaluating the biological processes affecting divergence. We do not
deny the importance of geographical context for understanding
divergence. Rather, we believe this context can be better understood by
modelling and measuring quantities, such as gene flow and selection,
rather than assigning cases to discrete categories like
sympatric and allopatric speciation.
Fitzpatrick, Fordyce, Gavrilets. What, if anything, is sympatric speciation?. J Evolution Biol (2008) vol. 21 (6) pp. 1452-1459
Sticklebacks
Rundle HD & Schluter D (2004). Natural Selection and Ecological Speciation in Sticklebacks. In: Adaptive Speciation, eds. Dieckmann U, Doebeli M, Metz JAJ & Tautz D, pp. 192–209. Cambridge University Press.
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Gavrilets and Vose. Dynamic patterns of adaptive radiation. P Natl Acad Sci Usa (2005) vol. 102 (50) pp. 18040-18045
Sympatric speciation
Bolnick and Fitzpatrick. Sympatric speciation: Models and empirical evidence. Annu Rev Ecol Syst (2007) vol. 38 pp. 459-487
Empirical Theoretical
Punctuated equilibrium
Various works by Gould and Eldredge