Competition as a selective mechanism for larger offspring size in guppies

Highly competitive environments are predicted to select for larger offspring. Guppies Poecilia reticulata from low-predation populations have evolved to make fewer, larger offspring than their counterparts from high-predation populations. As predation co-varies with the strength of competition in na...

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Bibliographic Details
Published inOikos Vol. 117; no. 1; pp. 104 - 113
Main Author Bashey, Farrah
Format Journal Article
LanguageEnglish
Published Copenhagen Copenhagen : Blackwell Publishing Ltd 01.01.2008
Blackwell Publishing Ltd
Blackwell Publishing
Blackwell
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Summary:Highly competitive environments are predicted to select for larger offspring. Guppies Poecilia reticulata from low-predation populations have evolved to make fewer, larger offspring than their counterparts from high-predation populations. As predation co-varies with the strength of competition in natural guppy populations, here I present two laboratory experiments that evaluate the role of competition in selecting for larger offspring size. In the first experiment, paired groups of large and small newborns from either a high- or a low-predation population were reared in mesocosms under a high- or a low-competition treatment. While large newborns retained their size advantage over small newborns in both treatments, newborn size increased growth only in the high-competition treatment. Moreover, the increase in growth with size was greater in guppies derived from the low-predation population. In the second experiment, pairs of large and small newborns were reared in a highly competitive environment until reproductive maturity. Small size at birth delayed maturation and the effect of birth size on male age of maturity was greater in the low-predation population. These results support the importance of competition as a selective mechanism in offspring size evolution.
Bibliography:http://dx.doi.org/10.1111/j.2007.0030-1299.16094.x
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ISSN:0030-1299
1600-0706
DOI:10.1111/j.2007.0030-1299.16094.x