Abstract
Under the preference-performance hypothesis, natural selection will favor females that choose oviposition sites that optimize the fitness of their offspring. Such a preference-performance relationship may entail important consequences mainly on fitness-related traits. We used the well-characterized cactus-Drosophila system to investigate the reproductive capacity in the pair of sibling species D. buzzatii and D. koepferae reared in two alternative host plants. According to our hypothesis, ovariole number (as a proxy of reproductive capacity) depends on host plant selection. Our results indicate that the capacity of D. buzzatii showed to be mild, only increasing the number of ovarioles by as much as 10% when reared in its preferred host. In contrast, D. koepferae exhibited a similar reproductive capacity across host cacti, even though it showed a preference for its primary host cactus. Our study also revealed that D. buzzatii has a larger genetic variation for phenotypic plasticity than its sibling, although ovariole number did not show clear-cut differences between species. We will discuss the weak preference-performance pattern observed in these cactophilic species in the light of nutritional and toxicological differences found between the natural host plants.
Highlights
Ovariole number variation is one of the most important indicators of the reproductive effort made by females in relation to resource availability for offspring [1,2]
The analysis of co-variance revealed a significant Line-by-Cactus interaction (Table 1), indicating that variation among lines in ovariole number depended on the rearing cactus
Ovariole number scores of the lines tested varied across rearing cacti. These results can be interpreted as genetic variation for phenotypic plasticity on ovariole number
Summary
Ovariole number variation is one of the most important indicators of the reproductive effort made by females in relation to resource availability for offspring [1,2]. The number of ovarioles exhibits strong phenotypic plasticity in response to changing environmental conditions during juvenile development [6,7]. It has been recently suggested that nutritional plasticity of ovariole number has an adaptive value [10]. Generalist Drosophila species, such as D. melanogaster and D. simulans, changed the number of ovarioles under diet variation. Specialist species, such as D. sechellia and D. erecta, exhibit similar ovariole number across different diets. Such adaptive plastic responses allow generalist species to express advantageous phenotypes in a broader range of environments, unlike specialist species, which show a lack of environmental sensitivity. Females lay eggs in necrotic cactus tissues (Figure 1), which is the particular environment in which larvae feed
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