Abstract
Quantifying the relations between plant-antagonistic interactions and natural selection among populations is important for predicting how spatial variation in ecological interactions drive adaptive differentiation. Here, we investigate the relations between the opportunity for selection, herbivore-mediated selection, and the intensity of plant-herbivore interaction among 11 populations of the insect-pollinated plant Primula florindae over 2 years. We experimentally quantified herbivore-mediated directional selection on three floral traits (two display and one phenological) within populations and found evidence for herbivore-mediated selection for a later flowering start date and a greater number of flowers per plant. The opportunity for selection and strength of herbivore-mediated selection on number of flowers varied nonlinearly with the intensity of herbivory among populations. These parameters increased and then decreased with increasing intensity of plant-herbivore interactions, defined as an increase in the ratio of herbivore-damaged flowers per individual. Our results provide novel insights into how plant-antagonistic interactions can shape spatial variation in selection on floral traits and contribute toward understanding the mechanistic basis of geographic variation in angiosperm flowers.
Highlights
A major goal in evolutionary biology is to understand how biotic interactions shape spatial variation in natural selection acting on angiosperm floral traits (Harder and Johnson, 2009; Van der Niet et al, 2014)
Spatial variation in selection is an important underlying mechanism of many evolutionary patterns and processes including the maintenance of heritable variation in quantitative traits (Grant and Price, 1981), coevolutionary interactions (Paudel et al, 2016), Biotic Interaction and Natural Selection and the geographical differentiation of floral traits leading to speciation (Siepielski et al, 2013)
The results indicated that the opportunity for selection and the strength of herbivore-mediated selection on floral display covaried nonlinearly with an increasing intensity of plant-herbivore interactions among populations
Summary
A major goal in evolutionary biology is to understand how biotic interactions shape spatial variation in natural selection acting on angiosperm floral traits (Harder and Johnson, 2009; Van der Niet et al, 2014). Empirical work on natural selection has provided evidence that the relations between biotic interaction intensity, the opportunity for selection (defined as the variance in relative fitness; Downhower et al, 1987; Weis et al, 1992) and the strength of selection are often linear among populations (Weis et al, 1992; Wilson, 1995; Ashman and Morgan, 2004; Moeller and Geber, 2005).
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