A carryover effect of migration underlies individual variation in reproductive readiness and extreme egg size dimorphism in Macaroni Penguins

Crossin, Glenn T.; Trathan, Phil N. ORCID: https://orcid.org/0000-0001-6673-9930; Phillips, Richard A.; Dawson, Alistair; Le Bouard, Fabrice; Williams, Tony D.. 2010 A carryover effect of migration underlies individual variation in reproductive readiness and extreme egg size dimorphism in Macaroni Penguins. American Naturalist, 176 (3). 357-366. 10.1086/655223

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Abstract/Summary

Where life-history stages overlap, there is the potential for physiological conflicts that might be important in mediating carryover effects. However, our knowledge of the specific physiological mechanisms underlying carryover effects remains rudimentary, and specific examples remain rare. Here we show that female macaroni penguins (Eudyptes chrysolophus) initiate vitellogenesis and yolk formation while at sea during return migrations to breeding colonies; yolk formation takes approximately 16 days, but females lay only 7-14 days after their return. Once on land, Eudyptes penguins show a unique reproductive pattern of extreme egg size dimorphism in which the smaller, first-laid A-egg is 55%-75% of the size of the larger B-egg. We show that the degree of egg size dimorphism is inversely correlated with time between arrival and laying; that is, females that begin reproductive development well in advance of their return produce more dimorphic eggs. Furthermore, late-arriving females that produce the most dimorphic eggs have lower plasma levels of the yolk precursor vitellogenin on arrival; that is, they show lower reproductive "readiness." These data support the hypothesis that extreme egg size dimorphism in Eudyptes penguins is due to a physiological constraint imposed by a migratory carryover effect and argue against small A-eggs having a specific, adaptive function.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1086/655223
Programmes:	CEH Topics & Objectives 2009 - 2012 > Biodiversity > BD Topic 2 - Ecological Processes in the Environment > BD - 2.4 - Estimate the impact of the main drivers and pressures on biodiversity ... BAS Programmes > Polar Science for Planet Earth (2009 - ) > Ecosystems
UKCEH and CEH Sections/Science Areas:	Watt
ISSN:	0003-0147
NORA Subject Terms:	Marine Sciences Biology and Microbiology Zoology
Date made live:	21 Sep 2010 08:41 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/10819

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