Ontogeny and Population Biology of a Sex-Limited Colour Polymorphism

Research output: ThesisDoctoral Thesis (compilation)


This study has involved investigation of number of populations of the damselfly Ischnura elegans over several years, looking at frequency changes over time, morphological differences between the sexes and the morphs, differences in growth rate and development time, differences in fecundity between the morphs, and genetic differentiation between populations. I. elegans is a small annual damselfly with three female colour morphs (Androchrome, Infuscans, and Infuscans-obsoleta), one of which (the Androchrome) is considered a male mimic; males are monomorphic.

Empirically estimated selection coefficients were used in a population genetic and dynamic model with environmental variation which predicted coexistence of the three morphs. This suggests that negative frequency-dependence on fecundity mediated by male mating harassment is sufficient to explain coexistence of the morphs. Field data also showed that fecundity decreased with increasing frequency in the population for all three morphs. Investigation of sexual dimorphism revealed that the sexes differed in development time, growth rates, and adult size and shape and that sexual size dimorphism is produced in I. elegans by a combination of development time and development rate acting in concert. The female morphs also differed in development time, growth rates, and adult size and shape, although in this case effects of development time and development rate cancelled each other out. In addition, male-like body shape had a negative effect on fecundity in Infuscans-obsoleta females but not in Androchrome or Infuscans females. Quantitative genetic parameters for morphological traits showed that an evolutionary response to selection on body shape is possible. Comparisons of Fst-values and the lack of isolation by distance both suggest that this is a highly dynamic non-equilibrium system, and genetic diversity appears to be influenced by wind direction.

The results in this study indicate that the morphs are subject to negative frequency-dependent selection via male mating harassment, and that the differences between the morphs are part of their identity as alternative adaptive strategies.


Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Ecology


  • embryologi, ontogeni, animal morphology, embryology, Utvecklingsbiologi, Damselflies, Colour polymorphism, Development, Frequency-dependence, Morphology, growth (animal), ontogeny, Animal anatomy, Development biology, Djurs anatomi och morfologi, Population divergence, Animal ecology, Djurekologi
Original languageEnglish
Awarding Institution
Supervisors/Assistant supervisor
  • Svensson, Erik I., Supervisor, External person
Award date2006 Nov 23
  • Xanto Grafiska AB
Print ISBNs91-7105-243-7
Publication statusPublished - 2006
Publication categoryResearch

Bibliographic note

Defence details Date: 2006-11-23 Time: 09:00 Place: Blue Hall, Ecology Building, Sölvegatan 37, Lund External reviewer(s) Name: Promislow, Daniel Title: Dr. Affiliation: University of Georgia, USA --- The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Animal Ecology (Closed 2011) (011012001)

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