Editing Unit of selection (section)

=== Species and higher levels ===
{{Main|Punctuated equilibrium}}
{{See also|Speciation|Species concept|l2=Species problem|Species complex}}

It remains controversial among biologists whether selection can operate at and above the level of species.<ref name="Vrba 1984">{{cite journal | last=Vrba | first=Elisabeth S. | title=What is Species Selection? | journal=Systematic Zoology | volume=33 | issue=3 | pages=318–328 | year=1984 | doi=10.2307/2413077 | jstor=2413077 }}</ref> Proponents of species selection include [[R. A. Fisher]] (1929);<ref name="Vrba 1984"/> [[Sewall Wright]] (1956);<ref name="Vrba 1984"/> [[Richard Lewontin]] (1970);<ref name="Vrba 1984"/> [[Niles Eldredge]] & [[Stephen Jay Gould]] (1972); [[Steven M. Stanley]] (1975).<ref name="Stanley 1975">{{cite journal | last=Stanley | first=SM | title=A theory of evolution above the species level. | journal=Proceedings of the National Academy of Sciences of the United States of America | volume=72 | issue=2 | year=1975 | pmid=1054846 | pmc=432371 | pages=646–650 | doi=10.1073/pnas.72.2.646| bibcode=1975PNAS...72..646S | doi-access=free }}</ref><ref name="Vrba 1984"/> Gould proposed that there exist [[macroevolution]]ary processes which shape evolution, not driven by the [[microevolution]]ary mechanisms of the [[Neo-Darwinism|Modern Synthesis]].<ref>{{cite journal |last=Lieberman |first=Bruce S. |author2=Vrba, Elisabeth S. |title=Stephen Jay Gould on species selection: 30 years of insight |journal=Paleobiology |date=Spring 2005 |volume=31 |issue=2 Suppl |pages=113–121 |doi=10.1666/0094-8373(2005)031[0113:SJGOSS]2.0.CO;2 |s2cid=14801676 |url=http://paleo.ku.edu/geo/faculty/BSL/gouldselection.pdf |access-date=2012-07-08 |archive-url=https://web.archive.org/web/20120918210548/http://paleo.ku.edu/geo/faculty/BSL/gouldselection.pdf |archive-date=2012-09-18 |url-status=dead }}</ref> If one views species as entities that replicate (speciate) and die (go extinct) within a [[clade]], then species could be subject to selection and thus could change their occurrence over geological time, much as heritable selected-for traits change theirs over generations.
For evolution to be driven by species selection, differential success must be the result of selection upon species-intrinsic properties, rather than for properties of genes, cells, individuals, or populations within species. Such properties include, for example, population structure, their propensity to speciate, extinction rates, and geological persistence.  While the fossil record shows differential persistence of species, examples of species-intrinsic properties subject to natural selection have been much harder to document.

One issue with selection among [[clade]]s is that they are not independent, i.e. all species are descended from the same [[last universal common ancestor]] and are thus part of the same clade.<ref name="okasha2006" /> This criticism does not apply to selection among different [[gene family|gene families]] that are not evolutionarily related, and which are [[Gene duplication|duplicated]] and lost at different rates rather than speciating and going extinct at different rates.<ref name="james2023" />

In the microbial realm, it has been interpreted that the unit of selection is a blend of ecological and functional behaviors, or [[Guild (ecology)|guilds]], beyond the species-level.<ref>{{Cite journal |last1=Shapiro |first1=B. Jesse |last2=Polz |first2=Martin F. |date=May 2014 |title=Ordering microbial diversity into ecologically and genetically cohesive units |url=http://dx.doi.org/10.1016/j.tim.2014.02.006 |journal=Trends in Microbiology |volume=22 |issue=5 |pages=235–247 |doi=10.1016/j.tim.2014.02.006 |pmid=24630527 |issn=0966-842X|pmc=4103024 |hdl=1721.1/101684 }}</ref>