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Is domestication driven by reduced fear of humans? Boldness, metabolism and serotonin levels in divergently selected red junglefowl (Gallus gallus)
Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering. (AVIAN Behavioural Genomics and Physiology group)
Linköping University, Department of Physics, Chemistry and Biology, Biology. (AVIAN Behavioural Genomics and Physiology group)
Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering. (AVIAN Behavioural Genomics and Physiology group)
Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering. (AVIAN Behavioural Genomics and Physiology group)
2015 (English)In: Biology Letters, ISSN 1744-9561, E-ISSN 1744-957X, Vol. 11, no 9, 20150509Article in journal (Refereed) Published
Abstract [en]

Domesticated animals tend to develop a coherent set of phenotypic traits. Tameness could be a central underlying factor driving this, and we therefore selected red junglefowl, ancestors of all domestic chickens, for high or low fear of humans during six generations. We measured basal metabolic rate (BMR), feed efficiency, boldness in a novel object (NO) test, corticosterone reactivity and basal serotonin levels (related to fearfulness) in birds from the fifth and sixth generation of the high- and low-fear lines, respectively (44-48 individuals). Corticosterone response to physical restraint did not differ between selection lines. However, BMR was higher in low-fear birds, as was feed efficiency. Low-fear males had higher plasma levels of serotonin and both low-fear males and females were bolder in an NO test. The results show that many aspects of the domesticated phenotype may have developed as correlated responses to reduced fear of humans, an essential trait for successful domestication.

Place, publisher, year, edition, pages
ROYAL SOC , 2015. Vol. 11, no 9, 20150509
Keyword [en]
genetics; domestication; stress
National Category
Zoology Evolutionary Biology
Identifiers
URN: urn:nbn:se:liu:diva-123162DOI: 10.1098/rsbl.2015.0509ISI: 000364772300009PubMedID: 26382075OAI: oai:DiVA.org:liu-123162DiVA: diva2:877387
Note

Funding Agencies|research council Formas; ERC [322206]

Available from: 2015-12-07 Created: 2015-12-04 Last updated: 2017-01-18Bibliographically approved
In thesis
1. Early domestication?: Phenotypic alterations of Red Junglefowl selected for divergent fear of humans
Open this publication in new window or tab >>Early domestication?: Phenotypic alterations of Red Junglefowl selected for divergent fear of humans
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Domestication is the process through which animals adapt to conditions provided by humans. The domesticated phenotype differs from wild ancestors in a number of traits relating to physiology, morphology and behaviour. One of the most striking differences is the animals’ fear response towards humans, and reduced fear of humans is assumed to have been an early prerequisite for the success of domestication. The early alterations seen in the domesticated phenotype may be traits developed as a correlated selection response due to tameness rather than selected upon one by one.

This thesis summarizes a project where Red Junglefowl were selected for divergent fear of humans during six generations. In every generation, fear response to human was assessed in a standardized test and, according to fear score, the animals were bred for either high fear of humans (H) or low fear of humans (L). The animals were, above that of the standardized selection test, behaviourally phenotyped in different tests in each generation mainly focusing on fear, exploration and social behaviour. In addition to behaviour, the animals were phenotyped for body weight, egg weight, metabolism, feed intake, plumage condition, blood plasma corticosterone and peripheral serotonin. After culling, vital organs and brains were harvested and weighed.

In paper I, we demonstrated that the selection trait has a significant genetic heritability and is genetically correlated with other behavioural responses associated with fearfulness and exploration. In paper II, we concluded that animals from the L strain had better plumage condition, higher weight, laid larger eggs and also generated larger offspring. Furthermore, when tested in a social dominance test with a limited resource, they received less and performed more aggression regardless of whether the restricted source was edible or not. In paper III, we revealed that animals from the L strain had higher basal metabolic rate as chicks, gained more weight in relation to feed intake and were bolder in a Novel Object test. Furthermore, the L males had higher plasma levels of peripheral serotonin, but the corticosterone after a restraint stress test did not differ. In paper IV and V, we concluded the project by comparing brain and organ weights as well as behaviour of the parental generation (P0) with the fifth selected generation (S5). The absolute brain weight as well as the weight specific brain weight were larger in the animals selected on H than in the L-animals. The relative weight of telencephalon was significantly higher in H whereas relative weight of cerebellum was significantly lower. Heart, liver, spleen and testes were all relatively heavier in H animals than in L. Interestingly, the behaviours assessed in P0 and S5 seemed to be rather resilient to the selection with only small differences in S5.

To summarize, the selection on divergent tameness in Red Junglefowl has affected several phenotypic traits associated with the domesticated phenotype. The results of this project indicate that tameness in Red Junglefowl could be an underlying factor driving trait modifications towards the domesticated phenotype.

Abstract [sv]

Den här avhandlingen är ett resultat av ett projekt där vi avlat djur på tamhet för att undersöka egenskapens roll i den tidiga domesticeringen. De domesticerade djur som vi har i vår närhet har alla genomgått en process där de har anpassats för vår miljö. Det skulle kunna liknas vid en snabb evolution, där ett djurs utseende och beteende förändras under en relativt sett kort tid genom avel av människan. Domesticerade djur skiljer sig från sina vilda släktingar på många olika sätt, de kan vara både mindre och större är ursprunget, finnas i olika färgvariationer, ha ändrade kroppsproportioner och de skiljer sig även åt i tröskelvärden för beteende från de vilda djuren. Skillnaderna mellan domesticerade djur och ursprunget är förvånansvärt lika mellan djurarter och man brukar kalla detta för den domesticerade fenotypen.

I det här projektet ville vi se om den domesticerade fenotypen egentligen är en biprodukt som uppkommer om man avlar djur på tamhet, på så sätt skulle rädslan för människor vara en nyckelegenskap för domesticeringen. För att undersöka detta använde vi det röda djungelhönset (RJF) som alla domesticerade höns härstammar ifrån. I sex generationer avlades RJF som antingen hade hög eller låg rädsla för människor. Eftersom vi bara har ett avelskriterium kan vi dra slutsatsen att om dessa djur kommer att skilja sig åt på fler sätt så beror det på korrelerade selektionseffekter. Det vill säga, man avlar på en egenskap och andra egenskaper följer med.

I varje generation har vi utfört beteendetester på djuren som främst varit kopplade till rädsla, utforskande och sociala beteenden. Utöver beteendetesterna har vi undersökt djurens kroppsvikt, äggvikt, metabolism, födointag, fjäderdräkt och tagit blodprov för att mäta kortikosteron och serotonin. När djuren har avlivats har vi vägt hjärnan, hjärtat, levern, mjälten och testiklarna.

Efter sex generationer av selekterad avel hade hönsen i projektet förändrats på olika sätt. Först och främst konstaterade vi att rädslan för människa är möjlig att avla på då den har en signifikant genetisk arvbarhet. De djuren som har en låg rädsla för människor har blivit större, socialt dominanta, lägger större ägg och får större avkomma. Metabolismen har påverkats så att de höns som har låg rädsla för människor har högre metabolism och omsätter även maten mer till tillväxt än de djuren med hög rädsla. Aveln har även påverkat djurens morfologi, de djuren som har hög rädsla för människor och alltså kan anses vara mer som ursprunget har större hjärna, hjärta, lever och mjälte. Många av dessa förändringar som uppkommit redan efter sex generationer korrelerar med de skillnader man ser mellan vilda och domesticerade djur vilket påvisar vikten av egenskapen för domesticeringsprocessen.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2016. 40 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1790
National Category
Biological Sciences Evolutionary Biology
Identifiers
urn:nbn:se:liu:diva-132003 (URN)10.3384/diss.diva-132003 (DOI)9789176856857 (ISBN)
Public defence
2016-12-07, Planck, Fysikhuset, Campus Valla, Linköping, 09:15 (English)
Opponent
Supervisors
Available from: 2016-11-17 Created: 2016-10-13 Last updated: 2016-11-22Bibliographically approved

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