Heterochrony: Evolution vs Development

presentation include informations mostly from the article heterochrny the evolution of development by kenneth J

1. Heterochrony: the Evolution of Development by Kenneth J. McNamara Prepared by Ahmet VARIS 1

2. OUTLINE Darwinian view Aim What is heterochrony? Types of heterochrony Relative Frequency of Heterochrony Heterochrony and Sexual Dimorphism Conclusion 2

3. Darwin’s view of Evo/Devo “Embryology rises greatly in interest, when we look at the embryo as a picture, more or less obscure, of the progenitor, either in its adult or larval state, of all members of the same great class . ’’ ‘’ This is one of the most important subjects in the whole round of natural history .” ( Darwin , 1878, p.396 and p.386) 3

4. AIM Understand how developmental stages evolve from ancestor to next generation. Observe how species from a common ancestor have different physiology as a result of their evolution of development. Examples from species 4

5. Evolution & Development Within populations of a single species, individuals do not all grow and develop at the same rate or for the same duration . The same rule occur b etween closely related species, the main morphological differences arise from variations to the rate and duration of growth. It is now recognized that developmental genes, particularly those regulating embryonic or larval development, play a major role in evolution 5

6. HETEROCHRONY Earlier definition (1800s) ‘ T he term heterochrony was used to describe cases in which the ontogenetic sequence of events did not recapitulate or repeat the sequence of events in phylogeny ’. Ontogeny is recapitulation of phylogeny dependent on the physiological functions of heredity (reproduction) and adaptation (nutrition). 6

7. 7 Embryos of different vertebrates share basic primitive features such as gills (red) and tails ( blue ) (The Earth Through Time, Harold L.  8th edition, Chapter 6 - page 5 ) ( http :// evolution.berkeley.edu/evolibrary/article/side_o_0/ontogeny_01 ) T he course of a chick's development , if recapitulation of phylogeny by ontogeny is tottally true

8. Today’sdefinition of heterochrony ‘ the mechanism that produces a parallel between ontogeny and phylogeny ’ . Heterochrony involves a shift in the timing of developmental processes so an event occurs earlier, later, or at a different rate in a taxon compared to its ancestor . 8 ( Leonard & James , 1993)   Embryonic development and stripe patterns of the zebras  Equus burchelli  (top) and  grevyi  (bottom). Illustration drawn by Carole B.

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10. Paedomorphosis The evolutionary process in which larval or juvenile features of an ancestral organism are displaced to the adult forms of its descendants . I f the period of growth of the descendant form is stopped prematurely : progenesis I f onset of growth is delayed : postdisplacement I f the rate of growth is less in the descendant than in the ancestor : neoteny 10

11. 11 Second stage of the development is the last stage anymore. The rate of growth is less when it compared to ancestor. The onset of growth is delayed so the organisms development stop when it become mature and differentiate from ancestor. ( Kenneth J . 2012) ( https :// www.geol.umd.edu BSCI392 , 10-5-07 ) X axis:time Y axis: development

12. Peramorphosis P hylogenetic change in which individuals of a species mature past adulthood and take on traits which havent seen yet . if the period of growth in the descendant is extended : hypermorphosis if the onset of growth occurs earlier in the descendant than in the ancestor : predisplacement if the growth rate is increased : acceleration 12

13. 13 Maturation occur later than ancestor The speed of development is faster than ancestor The structures begin development earlier than ancestor ( Kenneth J . 2012) ( https :// www.geol.umd.edu BSCI392 , 10-5-07 ) X axis:time Y axis: development

14. 14 D ifferences in shape of the skull between three different breeds of dogs Evolution of the domestic dog from the wolf by paedomorphosis ( Kenneth J . 2012)

15. Relative Frequency of Heterochrony Amphibians show a dominantly paedomorphosis , which may be related to their large cell size, causing a reduced rate of cellular division . Paedomorphosis has occurred many times in frogs, for example , resulting in the development of many miniature species . The 29 smallest species (with the smallest having an average body length of just 7.7 millimeters) are spread across five families and 11 genera . P eramorphosis may have been more frequent in dinosaurs , in particular being a major contributing factor to the evolution of very large body size 15

16. 16 Peramorphic evolution of protoceratopsian dinosaurs ( Kenneth J . 2012)

17. Heterochrony and Sexual Dimorphism   Sexual dimorphism: T he condition where the two sexes of the same species exhibit different characteristics beyond the differences in their sexual organs . S ize and morphological variance arises from either variations in growth rates or differences in the relative times of onset of sexual maturity; in other words, it arises from heterochrony . 17

18. 18 The adult female of the blue boxfish , Stropiurichthys robustus , is paedomorphic compared with the male, resembling the juvenile in body shape and body patterning. Photocorynus males live parasitically attached to the female . ( Kenneth J . 2012) ( http :// www.fishbase.org/summary/Photocorynus-spiniceps.html )

19. Conclusion The evolution of organisms mostly caused from differentiation of heterechronic genes which influence development of organisms We are (as homo sapiens ) a classic example of dissociated heterochrony , where some peramorphic features are developmental trade-offs for other, paedomorphic , features: some parts of our anatomy are relatively retarded, compared with our ancestors , but others have developed beyond. So heterochrony is the interaction between development and evolution from ontegenetic and phylogenic perspective . 19

20. Articles about Heterochronic Genes Koen Geuten and Heleen Coenen , Heterochronic genes in plant evolution and development . Carl S. Thummel , Molecular Mechanisms of Developmental Timing in C. elegans and Drosophila . Eric G. Moss , Heterochronic Genes and the Nature of Developmental Time . 20

21. REFERENCES Kenneth J. McNamara (2012), Heterochrony : the Evolution of Developmen , DOI 10.1007/s12052-012-0420-3 Kathleen K. Smith (2002), Sequence Heterochrony and the Evolution of Development , DOI 10.1002/jmor.10014 Timing is Everything: Morphogenesis , Heterochrony and Evolution , 2016 Homeotic Genes and Body Patterns , http ://learn.genetics.utah.edu / The Earth Through Time, Harold L. Levin, 8th edition, Chapter 6 Ontogeny and phylogeny , http:// evolution.berkeley.edu/evolibrary/article/side_o_0/ontogeny_01 21

22. THANK YOU 22