title: Individual heterogeneity in reproductive rates and cost of reproduction in a long-lived vertebrate.
abstract: Individual variation in reproductive success is a key feature of evolution, but also has important implications for predicting population responses to variable environments. Although such individual variation in reproductive outcomes has been reported in numerous studies, most analyses to date have not considered whether these realized differences were due to latent individual heterogeneity in reproduction or merely random chance causing different outcomes among like individuals. Furthermore, latent heterogeneity in fitness components might be expressed differently in contrasted environmental conditions, an issue that has only rarely been investigated. Here, we assessed (i) the potential existence of latent individual heterogeneity and (ii) the nature of its expression (fixed vs. variable) in a population of female Weddell seals (Leptonychotes weddellii), using a hierarchical modeling approach on a 30-year mark-recapture data set consisting of 954 individual encounter histories. We found strong support for the existence of latent individual heterogeneity in the population, with "robust" individuals expected to produce twice as many pups as "frail" individuals. Moreover, the expression of individual heterogeneity appeared consistent, with only mild evidence that it might be amplified when environmental conditions are severe. Finally, the explicit modeling of individual heterogeneity allowed us to detect a substantial cost of reproduction that was not evidenced when the heterogeneity was ignored.
authors.affiliation: Department of Ecology, Montana State University Bozeman, Montana, 59717.
authors.forename: Thierry
authors.initials: T
authors.lastname: Chambert
authors.forename: Jay J
authors.initials: JJ
authors.lastname: Rotella
authors.forename: Megan D
authors.initials: MD
authors.lastname: Higgs
authors.forename: Robert A
authors.initials: RA
authors.lastname: Garrott
keywords: Bayesian statistics; individual variation; life-history theory; marine mammals; population dynamics; posterior predictive checks
references.citation: Stat Med. 2009 Nov 10;28(25):3049-67
references.pmid: 19630097
references.citation: J Anim Ecol. 2006 Jul;75(4):921-7
references.pmid: 17009755
references.citation: Nature. 2003 Oct 16;425(6959):714-7
references.pmid: 14562103
references.citation: Ecol Appl. 2012 Jul;22(5):1628-39
references.pmid: 22908718
references.citation: Ecology. 2010 Apr;91(4):951-7
references.pmid: 20462110
references.citation: Oecologia. 2008 May;156(1):237-47
references.pmid: 18246374
references.citation: Philos Trans R Soc Lond B Biol Sci. 2007 Jan 29;362(1477):95-111
references.pmid: 17405209
references.citation: Ecology. 2011 Oct;92(10):1985-93
references.pmid: 22073789
references.citation: J Anim Ecol. 2006 May;75(3):724-33
references.pmid: 16689955
references.citation: Theor Popul Biol. 2012 Dec;82(4):317-28
references.pmid: 23316493
references.citation: J Anim Ecol. 2011 Mar;80(2):375-83
references.pmid: 21182519
references.citation: J Exp Biol. 1992 Apr;165:181-94
references.pmid: 1588250
references.citation: Nature. 1993 Nov 18;366(6452):223-7
references.pmid: 8232582
references.citation: Am Stat. 1985 Aug;39(3):176-85
references.pmid: 12267300
references.citation: J Anim Ecol. 2010 Mar;79(2):436-44
references.pmid: 20102422
references.citation: Oikos. 2011 Mar;120(3):369-380
references.pmid: 29093607
references.citation: Trends Ecol Evol. 1999 Sep;14(9):343-348
references.pmid: 10441307
references.citation: Am Nat. 2002 Jan;159(1):96-105
references.pmid: 18707403
references.citation: Proc Biol Sci. 2011 Dec 7;278(1724):3465-73
references.pmid: 21957133
references.citation: J Anim Ecol. 2009 Jul;78(4):798-806
references.pmid: 19302318
references.citation: Ecology. 2009 Apr;90(4):975-84
references.pmid: 19449692
references.citation: Trends Ecol Evol. 1998 Oct 1;13(10):403-7
references.pmid: 21238360
references.citation: J Anim Ecol. 2009 Jan;78(1):143-51
references.pmid: 18700872
references.citation: Trends Ecol Evol. 2010 Apr;25(4):207-14
references.pmid: 19897275
references.citation: Am Nat. 2000 Jul;156(1):1-13
references.pmid: 10824017
references.citation: Am Nat. 2007 Apr;169(4):481-93
references.pmid: 17273980
references.citation: Ecol Lett. 2009 Nov;12(11):1261-76
references.pmid: 19740111
references.citation: Ecology. 2009 Sep;90(9):2491-502
references.pmid: 19769127
references.citation: Am Nat. 2008 Apr;171(4):455-67
references.pmid: 20374136
references.citation: J Anim Ecol. 2012 Jan;81(1):162-73
references.pmid: 21939440
references.citation: J Anim Ecol. 2007 May;76(3):448-58
references.pmid: 17439462
references.citation: Am Nat. 2012 Mar;179(3):375-90
references.pmid: 22322225
references.citation: Physiol Biochem Zool. 2008 Sep-Oct;81(5):651-62
references.pmid: 18707529
references.citation: Ecol Lett. 2009 Jan;12(1):93-106
references.pmid: 19016825
references.citation: Proc Biol Sci. 2011 Feb 7;278(1704):321-8
references.pmid: 20861050
references.citation: Rev Reprod. 1997 Sep;2(3):175-94
references.pmid: 9414481
references.citation: Ecology. 2009 Jul;90(7):1981-95
references.pmid: 19694145
references.citation: Oecologia. 2008 Feb;155(1):11-20
references.pmid: 17985158
references.citation: Trends Ecol Evol. 2001 May 1;16(5):254-260
references.pmid: 11301155
references.citation: J Anim Ecol. 2006 Sep;75(5):1058-70
references.pmid: 16922841
references.citation: J Exp Biol. 2004 Feb;207(Pt 6):973-82
references.pmid: 14766956
references.citation: Oecologia. 2003 Aug;136(4):543-50
references.pmid: 12768406
references.citation: Proc Biol Sci. 2012 Nov 22;279(1747):4532-41
references.pmid: 23015628
references.citation: Trends Ecol Evol. 2004 Jun;19(6):329-33
references.pmid: 16701279
references.citation: J Anim Ecol. 2011 Mar;80(2):361-4
references.pmid: 21054382
references.citation: Evolution. 2000 Jun;54(3):936-41
references.pmid: 10937266
references.citation: Respir Physiol. 1973 Apr;17(3):283-90
references.pmid: 4702979