Camille Madec , Johan Ehrlén and Jon Ågren

Floral display affects functional gender in the hermaphroditic herb Primula farinosa Camille Madec 1*, Johan Ehrlén 2 and Jon Ågren 1 * [email protected], Tel: +46 18471 2852; 1 Plant Ecology and Evolution, Dept. of Ecology and Genetics, EBC, Uppsala University, Sweden; 2 Dpt. of Ecology, Environment and Plant Sciences, Stockholm University, Sweden. Introduction Questions A prominent floral display may be favoured by selection because it (1) Is male reproductive success of the long-scaped morph greater than that of increases attractiveness to pollinators, but may be associated with a cost the short-scaped morph? in terms of an increased risk of damage from seed predators and grazers. (2) Does this compensate for a higher risk of reduced seed production caused by The benefits of a large display may be expressed through both male and interactions with seed predators and grazers? female function, while the negative effects of herbivore attack may often (3) Is the long-scaped morph functionally more male than is the short-scaped appear only after pollen dispersal, and thus predominantly influence female morph? reproductive success. Interactions with antagonists are therefore expected to influence plant functional gender. Results The short-lived, hermaphroditic herb Primula farinosa is dimorphic for scape length and occurs as a long-scaped and a short-scaped morph. The long-scaped morph displays its flowers well above the ground, whereas the At the first site, where grazing pressure and seed predation were high (Fig. 3), short-scaped morph displays its flowers close to the ground (Fig. 1). In the long-scaped morph produced fewer seeds than did the short-scaped morph, southern Sweden, the plant is grazed by ungulates and attacked by an but tended to sire more seeds than did the short morph (Fig. 4). As a result, no insect seed predator, the tortricid moth Falseuncaria ruficiliana. significant difference in overall reproductive success was recorded between scape morphs (Fig. 4), but the functional gender of the long-scaped morph was more male than that of the short-scaped morph (Fig. 5). At the second site, the Long-scaped morph two morphs did not differ significantly in seed production, siring success, or functional gender. Short-scaped morph a b 0.2 1 - Bird’s eye primrose *** 0.8 Figure 3. Effect of scape 0.15 * morph (long vs. short) on (Primula farinosa) (a) the proportion of 0.6 Long - Perennial herb 0.1 plants grazed and (b) the Short proportion of fruits - Hermaphroditic 0.4 consumed by seed - Self-incompatible 0.05 predators in P. farinosa 0.2 - Distylous at sites 1 and 2. Proportion of grazed plants Proportion Proportion of consumed fruit Proportion * P < 0.05, *** P < 0.001 0 0 1 2 1 2 Figure 1. Floral display of the two scape Site Site morphs of Primula farinosa. 180 180 Site 1 Site 2 160 160 140 140 120 120 Methods 100 * 100 80 80 Long 60 60 Short We conducted a field experiment with genotyped plants at two sites in SE 40 40 20 20 Sweden. Female reproductive success was assessed by quantifying seed of seeds per plant Number 0 0 production and male siring success by genotyping offspring (Fig. 2). Female Male Total Female Male Total Reproductive success Reproductive success Figure 4. Effect of scape morph (long vs. short) on female, male and total reproductive successes of P. farinosa at sites 1 and 2. Mean ± SE. * P < 0.05 Array 1 50 m Site 2, 17 arrays 0.8 * L morph associated with … genotype G 2 0.6 Figure 5. Effect of scape S plants associated with morph (long vs. short) on genotype G1 50 m 0.4 Long functional gender Short (maleness) of P. farinosa at Maleness 0.2 sites 1 and 2. Mean ± SE. 13 km * P < 0.05 … 0 … 1 2 Site 50 m Site 1, 23 arrays L morph associated with Conclusions genotype G1 50 m S plants associated with genotype G2 … Our results demonstrate that interaction with antagonists can differentially affect selection on floral display through female and male function and produce a Figure 2. Experimental design. Each array included 4 long- and 4 short-scaped plants. Scape morph was relationship between floral display and plant functional gender. Positive effects of associated with a distinct microsatellite genotype, and half of the plants of each morph in each array were of the thrum and half of the plants of the pin style morph. a large floral display on male reproductive success may at least partly compensate for an increased risk of herbivore-mediated reduction in seed production. .

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