Sexual differences in growth strategies of the wolf spider Hygrolycosa rubrofasciata |
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Authors: | Laura Vertainen Rauno V Alatalo Johanna Mappes Silja Parri |
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Institution: | 1. Department of Biological and Environmental Science, University of Jyv?skyl?, Finland
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Abstract: | In invertebrates, the size at maturation is considered to be important for adult fitness. In the wolf spider Hygrolycosa rubrofasciata, however, it is only females that clearly benefit of larger size through augmented egg production, while male mating success
is determined by display activity not related to size. Thus, we can expect conflicting growth patterns for the sexes. Additionally,
populations differ greatly in adult size: individuals from dry habitats are smaller than those from wet habitats. To study
the sexual differences in reaction norms of growth, we reared spiderlings from seven populations at two food levels under
controlled laboratory conditions and compared size at sexual maturity. The shapes of reaction norms for adult size differed
between the sexes. In females, the reaction norms were parallel, but individuals from dry habitats tended to grow larger at
the given food levels. In males, there was a significant interaction between food level and population without any consistent
differences between populations. Maturation time was a plastic character in both sexes with no genetic differences among populations.
However, females on low food level matured later and significantly smaller in size than those on high food level. Males also
matured later on low food level, but they were nearly of the same size as males that received more food. Female growth patterns
reflected the strong selection for large size at maturity. However, the patterns for males were highly variable, which could
be explained by the weak overall selection on male size, which means that any environmental factors can affect male growing
patterns.
This revised version was published online in November 2006 with corrections to the Cover Date. |
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Keywords: | body mass maturation phenotypic plasticity reaction norms |
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