title: Behavioural phenotypes over the lifetime of a holometabolous insect.
abstract: BACKGROUND
  Behavioural traits can differ considerably between individuals, and such differences were found to be consistent over the lifetime of an organism in several species. Whether behavioural traits of holometabolous insects, which undergo a metamorphosis, are consistent across ontogeny is virtually unexplored. We investigated several behavioural parameters at five different time points in the lifetime of the holometabolous mustard leaf beetle Phaedon cochleariae (Coleoptera: Chrysomelidae), two times in the larval (second and third larval stage) and three times in the adult stage. We investigated 1) the stability of the behavioural phenotype (population level), 2) whether individuals rank consistently across behavioural traits and over their lifetime (individual level), and 3) in how far behavioural traits are correlated with the developmental time of the individuals.
  
  
  RESULTS
  We identified two behavioural dimensions in every life stage of P. cochleariae, activity and boldness (population level). Larvae and young adults ranked consistently across the investigated behavioural traits, whereas consistency over time was only found in adults but not between larvae and adults (individual level). Compared to adult beetles, larvae were less active. Moreover, younger larvae were bolder than all subsequent life stages. Over the adult lifetime of the beetles, males were less active than females. Furthermore, the activity of second instar larvae was significantly negatively correlated with the development time.
  
  
  CONCLUSIONS
  Our study highlights that, although there is no individual consistency over the larval and the adult life stage, the behavioural clustering shows similar patterns at all tested life stages of a holometabolous insect. Nevertheless, age- and sex-specific differences in behavioural traits occur which may be explained by different challenges an individual faces at each life stage. These differences are presumably related to the tremendous changes in life-history traits from larvae to adults and/or to a niche shift after metamorphosis as well as to different needs of both sexes, respectively. A faster development of more active compared to less active second instar larvae is in line with the pace-of-life syndrome. Overall, this study demonstrates a pronounced individuality in behavioural phenotypes and presumably adaptive changes related to life stage and sex.
authors.affiliation: Department of Chemical Ecology, Bielefeld University, Universitätsstr. 25, 33615 Bielefeld, Germany.
authors.forename: Thorben
authors.initials: T
authors.lastname: Müller
authors.affiliation: Department of Chemical Ecology, Bielefeld University, Universitätsstr. 25, 33615 Bielefeld, Germany.
authors.forename: Caroline
authors.initials: C
authors.lastname: Müller
keywords: Activity; Behavioural dimensions; Boldness; Holometabolous insect; Individuality; Lifetime; Metamorphosis; Ontogeny; Phaedon cochleariae
references.citation: Am Nat. 1993 Aug;142(2):242-72
references.pmid: 19425978
references.citation: Physiol Behav. 2007 Feb 28;90(2-3):405-11
references.pmid: 17196999
references.citation: Biol Rev Camb Philos Soc. 2007 May;82(2):291-318
references.pmid: 17437562
references.citation: Nature. 2007 Nov 8;450(7167):E5; discussion E5-6
references.pmid: 17994035
references.citation: J Anim Ecol. 2015 Jan;84(1):90-101
references.pmid: 24942327
references.citation: Physiol Behav. 2014 Apr 22;129:95-103
references.pmid: 24576678
references.citation: Trends Ecol Evol. 2004 Jul;19(7):372-8
references.pmid: 16701288
references.citation: Oecologia. 2003 Mar;134(4):596-604
references.pmid: 12647133
references.citation: Psychoneuroendocrinology. 2011 Oct;36(9):1370-7
references.pmid: 21493009
references.citation: Physiol Behav. 1991 Jul;50(1):83-90
references.pmid: 1946736
references.citation: J Evol Biol. 2009 Aug;22(8):1599-607
references.pmid: 19555442
references.citation: Philos Trans R Soc Lond B Biol Sci. 2013 Apr 08;368(1618):20120344
references.pmid: 23569292
references.citation: Annu Rev Psychol. 2005;56:453-84
references.pmid: 15709943
references.citation: Biol Rev Camb Philos Soc. 2010 May;85(2):301-25
references.pmid: 19961473
references.citation: J Exp Biol. 2007 Sep;210(Pt 18):3165-70
references.pmid: 17766293
references.citation: Trends Ecol Evol. 2010 Nov;25(11):653-9
references.pmid: 20832898
references.citation: Dev Psychobiol. 2011 Sep;53(6):631-40
references.pmid: 21365642
references.citation: Proc Biol Sci. 2012 Jul 7;279(1738):2645-51
references.pmid: 22398164
references.citation: Proc Biol Sci. 2011 Feb 22;278(1705):628-33
references.pmid: 20826482
references.citation: Nature. 2007 May 31;447(7144):581-4
references.pmid: 17538618
references.citation: Annu Rev Entomol. 2002;47:467-500
references.pmid: 11729082
references.citation: Ecol Lett. 2007 May;10(5):355-63
references.pmid: 17498134
references.citation: Behav Processes. 2014 Mar;103:105-11
references.pmid: 24315799
references.citation: Philos Trans R Soc Lond B Biol Sci. 2010 Dec 27;365(1560):4051-63
references.pmid: 21078657
references.citation: J Exp Biol. 2006 Feb;209(Pt 3):393-8
references.pmid: 16424089
references.citation: Dev Psychobiol. 2011 Sep;53(6):505-9
references.pmid: 21866537
references.citation: Proc Biol Sci. 2006 Mar 22;273(1587):741-50
references.pmid: 16608695