Editing Coevolution (section)

===Parasites and sexually reproducing hosts===
[[Host–parasite coevolution]] is the coevolution of a [[host (biology)|host]] and a [[parasite]].<ref name="Woolhouse">{{cite journal |doi=10.1038/ng1202-569 |last1=Woolhouse |first1=M. E. J. |last2=Webster |first2=J. P. |last3=Domingo |first3=E. |last4=Charlesworth |first4=B. |last5=Levin |first5=B. R. |title=Biological and biomedical implications of the coevolution of pathogens and their hosts |journal=[[Nature Genetics]] |date=December 2002 |pmid=12457190 |volume=32 |issue=4 |pages=569–77 |url=http://www.era.lib.ed.ac.uk/bitstream/1842/689/2/Charlesworth_Woolhouse.pdf |hdl=1842/689 |s2cid=33145462 |hdl-access=free }}</ref> A general characteristic of many viruses, as [[obligate parasite]]s, is that they coevolved alongside their respective hosts. Correlated mutations between the two species enter them into an evolution arms race. Whichever organism, host or parasite, that cannot keep up with the other will be eliminated from their habitat, as the species with the higher average population fitness survives. This race is known as the [[Red Queen hypothesis]].<ref>{{cite journal |last=Van Valen |first=L. |date=1973 |title=A New Evolutionary Law |journal=Evolutionary Theory |volume=1 |pages=1–30}} cited in: [http://pespmc1.vub.ac.be/REDQUEEN.html The Red Queen Principle]</ref> The Red Queen hypothesis predicts that sexual reproduction allows a host to stay just ahead of its parasite, similar to the [[Red Queen's race]] in ''[[Through the Looking-Glass]]'': "it takes all the running ''you'' can do, to keep in the same place".<ref>{{cite book |last=Carroll |first=Lewis |author-link=Lewis Carroll |orig-year=1871 |title=Through the Looking-glass: And what Alice Found There |url=https://books.google.com/books?id=cJJZAAAAYAAJ |publisher=Macmillan |date=1875 |page=42 |quote=it takes all the running ''you'' can do, to keep in the same place.}}</ref> The host reproduces sexually, producing some offspring with immunity over its parasite, which then evolves in response.<ref>{{cite journal |doi=10.1038/srep10004 |last=Rabajante |first=J. |display-authors=etal |title=Red Queen dynamics in multi-host and multi-parasite interaction system |journal=[[Scientific Reports]] |year=2015 |volume=5 |pages=10004 |pmid=25899168 |pmc=4405699 |bibcode=2015NatSR...510004R}}</ref>

The parasite–host relationship probably drove the prevalence of sexual reproduction over the more efficient asexual reproduction. It seems that when a parasite infects a host, sexual reproduction affords a better chance of developing resistance (through variation in the next generation), giving sexual reproduction variability for fitness not seen in the asexual reproduction, which produces another generation of the organism susceptible to infection by the same parasite.<ref>{{cite web |title=Sexual reproduction works thanks to ever-evolving host, parasite relationships |website=PhysOrg |url=https://phys.org/news/2011-07-sexual-reproduction-ever-evolving-host-parasite.html |date=7 July 2011}}</ref><ref>{{cite journal |last1=Morran |first1=L.T. |author2=Schmidt, O.G. |author3=Gelarden, I.A. |author4=Parrish, R.C. II |author5= Lively, C.M. |title=Running with the Red Queen: Host-Parasite Coevolution Selects for Biparental Sex |journal=Science |volume=333 |issue=6039 |pages=216–8 |date=8 July 2011 |id=Science.1206360 |bibcode=2011Sci...333..216M |doi=10.1126/science.1206360 |pmid=21737739 |pmc=3402160}}</ref><ref>{{cite encyclopedia |author=Hogan, C. Michael |date=2010 |url=https://editors.eol.org/eoearth/wiki/Virus |title=Virus |encyclopedia=Encyclopedia of Earth |editor=Cutler Cleveland |editor2=Sidney Draggan}}</ref> Coevolution between host and parasite may accordingly be responsible for much of the genetic diversity seen in normal populations, including blood-plasma polymorphism, protein polymorphism, and histocompatibility systems.<ref>{{cite journal |author1=Anderson, R. |author2=May, R. |date=October 1982 |title=Coevolution of hosts and parasites |journal=Parasitology |volume=85 |issue=2 |pages=411–426 |doi=10.1017/S0031182000055360 |pmid=6755367|s2cid=26794986 }}</ref>

[[File:Reed warbler cuckoo.jpg|upright|thumb|[[Brood parasite]]: [[Eurasian reed warbler]] raising a [[common cuckoo]]<ref name=Weiblen/>]]