Editing Evolutionary developmental biology (section)

===Variations in the toolkit===
{{Multiple image 
| total_width = 300px
| image1      = Heliconius erato Richard Bartz.jpg 
| caption1    = ''[[Heliconius erato]]''
| image2      = Heliconius melpomene 2b Richard Bartz.jpg 
| caption2    = ''[[Heliconius melpomene]]''
| footer      = Different species of ''Heliconius'' butterfly have [[parallel evolution|independently evolved]] similar patterns, apparently both [[facilitated variation|facilitated and constrained]] by the available [[developmental-genetic toolkit]] genes controlling wing [[pattern formation]]. 
}}

Variations in the toolkit may have produced a large part of the morphological evolution of animals. The toolkit can drive evolution in two ways. A toolkit gene can be expressed in a different pattern, as when the beak of Darwin's [[large ground-finch]] was enlarged by the ''[[Bone morphogenetic protein|BMP]]'' gene,<ref>{{Cite journal |last=Abzhanov |first=A. |last2=Protas, M. |last3=Grant, B.R. |last4=Grant, P.R. |last5=Tabin, C.J. |year=2004 |title=Bmp4 and Morphological Variation of Beaks in Darwin's Finches |journal=Science |volume=305 |issue=5689 |pages=1462–1465 |bibcode=2004Sci...305.1462A |doi=10.1126/science.1098095 |pmid=15353802 |s2cid=17226774}}</ref> or when snakes lost their legs as ''distal-less'' became under-expressed or not expressed at all in the places where other reptiles continued to form their limbs.<ref>{{Cite journal |last=Cohn, M.J. |last2=Tickle, C. |year=1999 |title=Developmental basis of limblessness and axial patterning in snakes |journal=Nature |volume=399 |issue=6735 |pages=474–479 |bibcode=1999Natur.399..474C |doi=10.1038/20944 |pmid=10365960 |s2cid=4309833}}</ref> Or, a toolkit gene can acquire a new function, as seen in the many functions of that same gene, ''distal-less'', which controls such diverse structures as the mandible in vertebrates,<ref name="Beverdam2002">{{Cite journal |last=Beverdam |first=A. |last2=Merlo, G.R. |last3=Paleari, L. |last4=Mantero, S. |last5=Genova, F. |last6=Barbieri, O. |last7=Janvier, P. |last8=Levi, G. |date=August 2002 |title=Jaw Transformation With Gain of Symmetry After DLX5/DLX6 Inactivation: Mirror of the Past? |url=https://iris.unito.it/bitstream/2318/87307/1/Beverdam_2002.pdf |journal=Genesis |volume=34 |issue=4 |pages=221–227 |doi=10.1002/gene.10156 |pmid=12434331 |s2cid=19592597 |hdl-access=free |hdl=2318/87307}}</ref><ref name="Depew2002">{{Cite journal |last=Depew, M.J. |last2=Lufkin, T. |last3=Rubenstein, J.L. |date=October 2002 |title=Specification of jaw subdivisions by DLX genes |journal=Science |volume=298 |issue=5592 |pages=381–385 |doi=10.1126/science.1075703 |pmid=12193642 |s2cid=10274300 |doi-access=free}}</ref> legs and antennae in the fruit fly,<ref>{{Cite journal |last=Panganiban |first=Grace |last2=Rubenstein |first2=John L. R. |date=2002 |title=Developmental functions of the Distal-less/Dlx homeobox genes |url=http://dev.biologists.org/content/129/19/4371 |journal=Development |volume=129 |issue=19 |pages=4371–4386 |doi=10.1242/dev.129.19.4371 |pmid=12223397}}</ref> and [[eyespot (mimicry)|eyespot pattern]] in [[butterfly]] [[wing]]s.<ref>{{Cite journal |last=Beldade, P. |last2=Brakefield, P.M. |last3=Long, A.D. |year=2002 |title=Contribution of Distal-less to quantitative variation in butterfly eyespots |journal=Nature |volume=415 |issue=6869 |pages=315–318 |doi=10.1038/415315a |pmid=11797007 |s2cid=4430563}}</ref> Given that small changes in toolbox genes can cause significant changes in body structures, they have often enabled the same function [[Convergent evolution|convergently]] or [[Parallel Evolution|in parallel]]. ''distal-less'' generates wing patterns in the butterflies ''[[Heliconius erato]]'' and ''[[Heliconius melpomene]]'', which are [[Müllerian mimicry|Müllerian mimics]]. In so-called [[facilitated variation]],<ref>{{Cite journal |last=Gerhart |first=John |last2=Kirschner |first2=Marc |year=2007 |title=The theory of facilitated variation |journal=Proceedings of the National Academy of Sciences |volume=104 |issue=suppl1 |pages=8582–8589 |bibcode=2007PNAS..104.8582G |doi=10.1073/pnas.0701035104 |pmc=1876433 |pmid=17494755 |doi-access=free}}</ref> their wing patterns arose in different evolutionary events, but are controlled by the same genes.<ref>{{Cite journal |last=Baxter, S.W. |last2=Papa, R. |last3=Chamberlain, N. |last4=Humphray, S.J. |last5=Joron, M. |last6=Morrison, C. |last7=ffrench-Constant, R.H. |last8=McMillan, W.O. |last9=Jiggins, C.D. |year=2008 |title=Convergent Evolution in the Genetic Basis of Mullerian Mimicry in Heliconius Butterflies |journal=Genetics |volume=180 |issue=3 |pages=1567–1577 |doi=10.1534/genetics.107.082982 |pmc=2581958 |pmid=18791259}}</ref> Developmental changes can contribute directly to [[speciation]].<ref>{{Cite journal |last=Pennisi, E. |author-link=Elizabeth Pennisi |year=2002 |title=Evolutionary Biology:Evo-Devo Enthusiasts Get Down to Details |journal=Science |volume=298 |issue=5595 |pages=953–955 |doi=10.1126/science.298.5595.953 |pmid=12411686 |s2cid=154023266}}</ref>