Editing Camouflage (section)

== Evolution ==

As there is a lack of evidence for camouflage in the fossil record, studying the evolution of camouflage strategies is very difficult. Furthermore, camouflage traits must be both adaptable (provide a fitness gain in a given environment) and heritable (in other words, the trait must undergo [[Directional selection|positive selection]]).<ref>{{Cite journal |last1=Sabeti |first1=P. C. |last2=Schaffner |first2=S. F. |last3=Fry |first3=B. |last4=Lohmueller |first4=J. |last5=Varilly |first5=P. |last6=Shamovsky |first6=O. |last7=Palma |first7=A. |last8=Mikkelsen |first8=T. S. |last9=Altshuler |first9=D. |last10=Lander |first10=E. S. |display-authors=3 |date=2006-06-16 |title=Positive Natural Selection in the Human Lineage |journal=Science |volume=312 |issue=5780 |pages=1614–1620 |doi=10.1126/science.1124309 |pmid=16778047 |bibcode=2006Sci...312.1614S |s2cid=10809290 }}</ref> Thus, studying the evolution of camouflage strategies requires an understanding of the genetic components and various ecological pressures that drive crypsis.

=== Fossil history ===

Camouflage is a soft-tissue feature that is rarely preserved in the [[fossil]] record, but rare fossilised skin samples from the [[Cretaceous]] period show that some marine reptiles were countershaded. The skins, pigmented with dark-coloured [[eumelanin]], reveal that both [[leatherback turtle]]s and [[mosasaur]]s had dark backs and light bellies.<ref>{{cite journal |last1=Lindgren |first1=Johan |last2=Sjövall |first2=Peter |last3=Carney |first3=Ryan M. |last4=Udval |first4=Per |last5=Gren |first5=Johan A. |last6=Dyke |first6=Gareth |last7=Schultz |first7=Bo Pagh |last8=Shawkey |first8=Matthew D. |last9=Barnes |first9=Kenneth R. |last10=Polcyn |first10=Michael J. |display-authors=3 |title=Skin pigmentation provides evidence of convergent melanism in extinct marine reptiles |journal=Nature |date=February 2014 |volume=506 |pages=484–488 |doi=10.1038/nature12899 |pmid=24402224 |issue=7489|bibcode=2014Natur.506..484L |s2cid=4468035 }}</ref> There is fossil evidence of camouflaged insects going back over 100&nbsp;million years, for example lacewings larvae that stick debris all over their bodies much as their modern descendants do, hiding them from their prey.<ref>{{cite web |last=Pavid |first=Katie |title=Oldest insect camouflage behaviour revealed by fossils |url=https://www.nhm.ac.uk/discover/news/2016/june/oldest-insect-camouflage-behaviour-revealed.html |date=28 June 2016}}</ref> Dinosaurs appear to have been camouflaged, as a 120&nbsp;million year old fossil of a ''[[Psittacosaurus]]'' has been preserved with [[countershading]].<ref>{{cite web |last=Watson |first=Traci |title=This Dinosaur Wore Camouflage |website=[[National Geographic Society]] |url=https://www.nationalgeographic.com/news/2016/09/dinosaur-camouflage-fossil-find/ |archive-url=https://web.archive.org/web/20191106232025/https://www.nationalgeographic.com/news/2016/09/dinosaur-camouflage-fossil-find/ |url-status=dead |archive-date=6 November 2019 |date=14 September 2016}}</ref>

=== Genetics ===

Camouflage does not have a single genetic origin. However, studying the genetic components of camouflage in specific organisms illuminates the various ways that crypsis can evolve among lineages. Many [[cephalopod]]s have the ability to actively camouflage themselves, controlling crypsis through neural activity. For example, the genome of the common cuttlefish includes 16 copies of the [[reflectin]] gene, which grants the organism remarkable control over coloration and iridescence.<ref>{{cite journal |last1=Song |first1=Weiwei |last2=Li |first2=Ronghua |last3=Zhao |first3=Yun |last4=Migaud |first4=Herve |last5=Wang |first5=Chunlin |last6=Bekaert |first6=Michaël |display-authors=3 |date=15 February 2021 |title=Pharaoh Cuttlefish, Sepia pharaonis, Genome Reveals Unique Reflectin Camouflage Gene Set |journal=Frontiers in Marine Science |volume=8 |pages=639670 |doi=10.3389/fmars.2021.639670 |issn=2296-7745|doi-access=free |bibcode=2021FrMaS...839670S |hdl=1893/32292 |hdl-access=free }}</ref> The reflectin gene is thought to have originated through transposition from symbiotic ''[[Aliivibrio fischeri]]'' bacteria, which provide bioluminescence to its hosts. While not all cephalopods use [[active camouflage]], ancient cephalopods may have inherited the gene horizontally from symbiotic ''A. fischeri'', with divergence occurred through subsequent gene duplication (such as in the case of ''Sepia officinalis'') or gene loss (as with cephalopods with no active camouflage capabilities).<ref>{{cite journal |last1=Guan |first1=Zhe |last2=Cai |first2=Tiantian |last3=Liu |first3=Zhongmin |last4=Dou |first4=Yunfeng |last5=Hu |first5=Xuesong |last6=Zhang |first6=Peng |last7=Sun |first7=Xin |last8=Li |first8=Hongwei |last9=Kuang |first9=Yao |last10=Zhai |first10=Qiran |last11=Ruan |first11=Hao |date=September 2017 |title=Origin of the Reflectin Gene and Hierarchical Assembly of Its Protein |journal=[[Current Biology]] |volume=27 |issue=18 |pages=2833–2842.e6 |doi=10.1016/j.cub.2017.07.061|pmid=28889973 |s2cid=9974056 |doi-access=free |bibcode=2017CBio...27E2833G }}</ref><sup>[3]</sup> This is unique as an instance of camouflage arising as an instance of [[horizontal gene transfer]] from an [[endosymbiont]]. However, other methods of horizontal gene transfer are common in the evolution of camouflage strategies in other lineages. [[Peppered moth]]s  and [[Phasmatodea|walking stick insects]]  both have camouflage-related genes that stem from transposition events.<ref>{{cite journal |last1=van't Hof |first1=Arjen E. |last2=Campagne |first2=Pascal |last3=Rigden |first3=Daniel J. |last4=Yung |first4=Carl J. |last5=Lingley |first5=Jessica |last6=Quail |first6=Michael A. |last7=Hall |first7=Neil |last8=Darby |first8=Alistair C. |last9=Saccheri |first9=Ilik J. |date=June 2016 |title=The industrial melanism mutation in British peppered moths is a transposable element |url=http://www.nature.com/articles/nature17951 |journal=[[Nature (journal)|Nature]] |volume=534 |issue=7605 |pages=102–105 |doi=10.1038/nature17951 |pmid=27251284 |bibcode=2016Natur.534..102H |s2cid=3989607 |issn=0028-0836}}</ref><ref>{{cite journal |last1=Werneck |first1=Jane Margaret Costa de Frontin |last2=Torres |first2=Lucas |last3=Provance |first3=David Willian |last4=Brugnera |first4=Ricardo |last5=Grazia |first5=Jocelia |date=3 December 2021 |title=First Report of Predation by a Stink Bug on a Walking-Stick Insect with Reflections on Evolutionary Mechanisms for Camouflage |doi=10.21203/rs.2.10812/v1 |s2cid=240967012 }}</ref>

The [[Agouti (coloration)|Agouti]] genes are orthologous genes involved in camouflage across many lineages. They produce yellow and red coloration ([[Melanin#Pheomelanin|phaeomelanin]]), and work in competition with other genes that produce black (melanin) and brown (eumelanin) colours.<ref>{{cite journal |last1=Voisey |first1=Joanne |last2=Van Daal |first2=Angela |date=February 2002 |title=Agouti: from Mouse to Man, from Skin to Fat |url=http://doi.wiley.com/10.1034/j.1600-0749.2002.00039.x |journal=Pigment Cell Research |volume=15 |issue=1 |pages=10–18 |doi=10.1034/j.1600-0749.2002.00039.x |pmid=11837451 }}</ref> In [[Eastern deer mouse|eastern deer mice]], over a period of about 8000 years the single agouti gene developed 9 mutations that each made expression of yellow fur stronger under natural selection, and largely eliminated melanin-coding black fur coloration.<ref>{{cite journal |last1=Pfeifer |first1=Susanne P |last2=Laurent |first2=Stefan |last3=Sousa |first3=Vitor C. |last4=Linnen |first4=Catherine R. |last5=Foll |first5=Matthieu |last6=Excoffier |first6=Laurent |last7=Hoekstra |first7=Hopi E. |last8=Jensen |first8=Jeffrey D. |display-authors=3 |date=2018-01-15 |title=The Evolutionary History of Nebraska Deer Mice: Local Adaptation in the Face of Strong Gene Flow |url=http://dx.doi.org/10.1093/molbev/msy004 |journal=Molecular Biology and Evolution |volume=35 |issue=4 |pages=792–806 |doi=10.1093/molbev/msy004 |pmid=29346646 |pmc=5905656 |issn=0737-4038}}</ref> On the other hand, all black [[Cat|domesticated cats]] have deletions of the agouti gene that prevent its expression, meaning no yellow or red color is produced. The evolution, history and widespread scope of the agouti gene shows that different organisms often rely on orthologous or even identical genes to develop a variety of camouflage strategies.<ref>{{cite journal |last1=Eizirik |first1=Eduardo |last2=Yuhki |first2=Naoya |last3=Johnson |first3=Warren E. |last4=Menotti-Raymond |first4=Marilyn |last5=Hannah |first5=Steven S. |last6=O'Brien |first6=Stephen J. |display-authors=3 |date=March 2003 |title=Molecular Genetics and Evolution of Melanism in the Cat Family |journal=Current Biology |volume=13 |issue=5 |pages=448–453 |doi=10.1016/S0960-9822(03)00128-3 |pmid=12620197 |s2cid=19021807 |doi-access=free |bibcode=2003CBio...13..448E }}</ref>

=== Ecology ===

While camouflage can increase an organism's fitness, it has genetic and energetic costs. There is a trade-off between detectability and mobility. Species camouflaged to fit a specific [[Habitat#Microhabitat types|microhabitat]] are less likely to be detected when in that microhabitat, but must spend energy to reach, and sometimes to remain in, such areas. Outside the microhabitat, the organism has a higher chance of detection. Generalized camouflage allows species to avoid predation over a wide range of habitat backgrounds, but is less effective. The development of generalized or specialized camouflage strategies is highly dependent on the biotic and abiotic composition of the surrounding environment.<ref>{{cite book |last1=Ruxton |first1=Graeme D. |author-link=Graeme Ruxton |url=https://oxford.universitypressscholarship.com/view/10.1093/oso/9780199688678.001.0001/oso-9780199688678-chapter-2 |title=Background matching |last2=Allen |first2=William L. |last3=Sherratt |first3=Thomas N. |last4=Speed |first4=Michael P. |date=2018 |publisher=[[Oxford University Press]] |volume=1 |doi=10.1093/oso/9780199688678.003.0002 |isbn=978-0-19-968867-8 }}</ref>

There are many examples of the tradeoffs between specific and general cryptic patterning. ''[[Phestilla]] melanocrachia'', a species of nudibranch that feeds on [[Scleractinia|stony coral]], utilizes specific cryptic patterning in reef ecosystems. The nudibranch syphons pigments from the consumed coral into the epidermis, adopting the same shade as the consumed coral. This allows the nudibranch to change colour (mostly between black and orange) depending on the coral system that it inhabits. However, ''P. melanocrachia'' can only feed and lay eggs on the branches of host-coral, ''[[Platygyra]] carnosa'', which limits the geographical range and efficacy in nudibranch nutritional crypsis. Furthermore, the nudibranch colour change is not immediate, and switching between coral hosts when in search for new food or shelter can be costly.<ref>{{cite journal |last1=Wong |first1=Kwan Ting |last2=Ng |first2=Tsz Yan |last3=Tsang |first3=Ryan Ho Leung |last4=Ang |first4=Put |date=24 June 2017 |title=First observation of the nudibranch Tenellia feeding on the scleractinian coral Pavona decussata |journal=Coral Reefs |volume=36 |issue=4 |pages=1121 |doi=10.1007/s00338-017-1603-8 |bibcode=2017CorRe..36.1121W |s2cid=33882835 |doi-access=free }}</ref>

The costs associated with distractive or disruptive crypsis are more complex than the costs associated with background matching. Disruptive patterns distort the body outline, making it harder to precisely identify and locate.<ref>{{cite book |last1=Ruxton |first1=Graeme D. |author-link=Graeme Ruxton |url=https://oxford.universitypressscholarship.com/view/10.1093/oso/9780199688678.001.0001/oso-9780199688678-chapter-3 |title=Disruptive camouflage |last2=Allen |first2=William L. |last3=Sherratt |first3=Thomas N. |last4=Speed |first4=Michael P. |date=20 September 2018 |publisher=[[Oxford University Press]] |volume=1 |doi=10.1093/oso/9780199688678.003.0003|isbn=978-0-19-968867-8 }}</ref> However, disruptive patterns result in higher predation.<ref>{{cite journal |last1=Stevens |first1=Martin |author1-link=Martin Stevens (biologist) |last2=Marshall |first2=Kate L. A. |last3=Troscianko |first3=Jolyon |last4=Finlay |first4=Sive |last5=Burnand |first5=Dan |last6=Chadwick |first6=Sarah L. |display-authors=3 |date=2013 |title=Revealed by Conspicuousness: Distractive Markings Reduce Camouflage |journal=Behavioral Ecology |volume=24 |issue=1 |pages=213–222 |doi=10.1093/beheco/ars156 |issn=1465-7279|doi-access=free }}</ref> Disruptive patterns that specifically involve visible symmetry (such as in some butterflies) reduce survivability and increase predation.<ref>{{cite journal |last1=Cuthill |first1=Innes C. |author-link=Innes Cuthill |last2=Hiby |first2=Elly |last3=Lloyd |first3=Emily |date=22 May 2006 |title=The Predation Costs of Symmetrical Cryptic Coloration |journal=Proceedings of the Royal Society B: Biological Sciences |volume=273 |issue=1591 |pages=1267–1271 |doi=10.1098/rspb.2005.3438 |issn=0962-8452 |pmc=1560277 |pmid=16720401}}</ref> Some researchers argue that because wing-shape and color pattern are genetically linked, it is genetically costly to develop asymmetric wing colorations that would enhance the efficacy of disruptive cryptic patterning. Symmetry does not carry a high survival cost for butterflies and moths that their predators views from above on a homogeneous background, such as the bark of a tree. On the other hand, natural selection drives species with variable backgrounds and habitats to move symmetrical patterns away from the centre of the wing and body, disrupting their predators' symmetry recognition.<ref>{{cite journal |last1=Wainwright |first1=J. Benito |last2=Scott-Samuel |first2=Nicholas E. |last3=Cuthill |first3=Innes C. |author3-link=Innes Cuthill |date=15 January 2020 |title=Overcoming the Detectability Costs of Symmetrical Coloration |journal=Proceedings of the Royal Society B: Biological Sciences |volume=287 |issue=1918 |pages=20192664 |doi=10.1098/rspb.2019.2664 |pmc=7003465 |pmid=31937221}}</ref>