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NATURAL SELECTION REDUCES ENERGY METABOLISM IN THE GARDEN SNAIL, HELIX ASPERSA ( CORNU ASPERSUM )
Author(s) -
Artacho Paulina,
Nespolo Roberto F.
Publication year - 2009
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.1558-5646.2008.00603.x
Subject(s) - biology , natural selection , selection (genetic algorithm) , ectotherm , stabilizing selection , snail , ecology , group selection , evolutionary biology , directional selection , inclusive fitness , zoology , machine learning , computer science
Phenotypic selection is widely recognized as the primary cause of adaptive evolution in natural populations, a fact that has been documented frequently over the last few decades, mainly in morphological and life‐history traits. The energetic definition of fitness predicts that natural selection will maximize the residual energy available for growth and reproduction, suggesting that energy metabolism could be a target of selection. To address this problem, we chose the garden snail, Helix aspersa ( Cornu aspersum ). We performed a seminatural experiment for measuring phenotypic selection on standard metabolic rate (SMR), the minimum cost of maintenance in ectotherm organisms. To discount selection on correlated traits, we included two additional whole‐organism performance traits (mean speed and maximum force of dislodgement). We found a combination of linear (negative directional selection, β=−0.106 ± 0.06; P = 0.001) and quadratic (stabilizing selection, γ=−0.012 ± 0.033; P = 0.061) selection on SMR. Correlational selection was not significant for any possible pair of traits. This suggests that individuals with average‐to‐reduced SMRs were promoted by selection. To the best of our knowledge, this is the first study showing significant directional selection on the obligatory cost of maintenance in an animal, providing support for the energetic definition of fitness.