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

Hybrid sterility

http://ywwg.com/wordpress/?p=397

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