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Multiple aspects of plasticity in clutch size vary among populations of a globally distributed songbird
Author(s) -
Westneat David F.,
Bókony Veronika,
Burke Terry,
Chastel Olivier,
Jensen Henrik,
Kvalnes Thomas,
Lendvai Ádám Z.,
Liker András,
Mock Douglas,
Schroeder Julia,
Schwagmeyer P. L.,
Sorci Gabriele,
Stewart Ian R. K.
Publication year - 2014
Publication title -
journal of animal ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.134
H-Index - 157
eISSN - 1365-2656
pISSN - 0021-8790
DOI - 10.1111/1365-2656.12191
Subject(s) - avian clutch size , clutch , phenotypic plasticity , biology , ecology , life history theory , life history , zoology , reproduction , physics , thermodynamics
Summary Plasticity in life‐history characteristics can influence many ecological and evolutionary phenomena, including how invading organisms cope with novel conditions in new locations or how environmental change affects organisms in native locations. Variation in reaction norm attributes is a critical element to understanding plasticity in life history, yet we know relatively little about the ways in which reaction norms vary within and among populations. We amassed data on clutch size from marked females in eight populations of house sparrows ( P asser domesticus ) from N orth A merica and E urope. We exploited repeated measures of clutch size to assess both the extent of within‐individual phenotypic plasticity and among‐individual variation and to test alternative hypotheses about the underlying causes of reaction norm shape, particularly the decline in clutch size with date. Across all populations, females of this multibrooded species altered their clutch size with respect to date, attempt order, and the interaction of date and order, producing a reaction norm in multidimensional environmental space. The reaction norm fits that predicted by a model in which optimal clutch size is driven by a decline with date hatched in the ability of offspring to recruit. Our results do not fit those predicted for other proposed causes of a seasonal decline in clutch size. We also found significant differences between populations in response to date and the date by attempt order interaction. We tested the prediction that the relationship with date should be increasingly negative as breeding season becomes shorter but found steeper declines in clutch size with date in populations with longer seasons, contrary to the prediction. Populations also differed in the level of among‐individual variation in reaction norm intercept, but we found no evidence of among‐individual variation in reaction norm slope. We show that complex reaction norms in life‐history characters exhibit within‐ and among‐population variance. The nature of this variance is only partially consistent with current life‐history theory and stimulates expansions of such theory to accommodate complexities in adaptive life history.