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Abstract There exists extensive variation in eye size. Much work has provided a connection between light availability and differences in eye size across taxa. Experimental tests of the role of the light environment on the evolution of eye size are lacking. Here, we performed a selection experiment that examined the influence of light availability on shifts in eye size and the connection between eye size and phototactic (anti‐predator) behaviour inDaphnia. We set‐up replicate experimental populations ofDaphnia, repeatedly evaluated phenotypic shifts in eye size during the ~50‐day experiment, and performed a common garden experiment at the end of the experiment to test for evolutionary shifts in eye size and behaviour. Our phenotypic analyses showed that eye size rapidly diverged between the light treatments; relative eye size was consistently larger in the low versus high light treatments. Selection on eye size was also modified by variation in density as increases inDaphniadensity favoured a larger eye. However, we did not observe differences in eye size between the light treatments following two generations of common garden rearing at the end of the experiment. We instead observed strong shifts in anti‐predator behaviour.Daphniafrom the low light treatment exhibited decreased phototactic responses to light. Our results show that decreased light relaxes selection on anti‐predator behaviour. Such trends provide new insights into selection on eye size and behaviour.
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Investment in visual system predicted by floral associations in sap beetles (Coleoptera: Nitidulidae)
Abstract Patterns in morphological variation are a central theme of evolution. Uncovering links between morphological character evolution and natural history, specifically feeding behaviour, is important to understanding biological diversity. Species within the sap beetles (Nitidulidae) exhibit a tremendous diversity of feeding behaviours. This immense diversity of feeding can be seen both between major lineages and very closely related taxa. Feeding behaviour diversity may drive morphological variation in several character systems (e.g., eyes). For example, in a shift from feeding on rotting fruit to flower‐visiting (anthophily), selective pressures on the visual system may vary and ultimately lead to differences in eye morphology. We tested for potential morphological shifts in relative eye size among adult beetles. We specifically tested for significant relationships between relative eye size and the following factors flower‐visiting and sex. We also tested for the influence of phylogeny on the evolution of relative eye size, implementing tests of trait correlation across a topology. We found greater relative eye size in taxa exhibiting anthophilous behaviour, regardless of phylogenetic relatedness or feeding behaviour of sister taxa. We were unable to recover a relationship between relative eye size and sex. Thus, feeding behaviour is currently the strongest predictor of eye size in sap beetles.
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- Award ID(s):
- 1655981
- PAR ID:
- 10442938
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Systematic Entomology
- Volume:
- 48
- Issue:
- 1
- ISSN:
- 0307-6970
- Page Range / eLocation ID:
- p. 1-9
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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