Investment in male function should often yield diminishing fitness returns, subjecting the evolution of male phenotypes to substantial constraints. In plants, the subdivision of male function via the gradual presentation of pollen might minimize these constraints by preventing the saturation of receptive stigmas. Here we report on an investigation of (a) patterns of investment in male function by plants in hermaphroditic (monoecious) and dioecious populations of Sagittaria latifolia, and (b) patterns of siring success by males vs. hermaphrodites in experimental mating arrays. We show that in natural populations, males from dioecious populations had greater investment in male function than hermaphrodites in monoecious populations. However, as a proportion of total flower production, males presented substantially fewer flowers at once than hermaphrodites. In comparison with hermaphrodites, therefore, males prolonged the period over which they presented pollen. In mating arrays comprised of females, males, and hermaphrodites, siring success by males increased linearly with flower production. This finding is consistent with the existence of a linear gain curve for male function in S. latifolia and supports the idea that the gradual deployment of male function enables plants to avoid diminishing returns on the investment in male function.
FieldData
Data collected from natural populations of S. latifolia, as described in the paper. Column names refer to the following information: Site (sampling location); SS (sexual system - monoecious or dioecious); Mopen (number of open male flowers per inflorescence); Mtotal (total number of male flowers per inflorescence); MVL (leaf mid-vein length for the leaf subtending the inflorescence, cm); Petal (petal width, cm).
ArrayDataPlantFlowerSize
Plant size and flowering data for the plants used in the mating arrays. Column labels refer to: Array (the array number; nb. these do not correspond with the labels in Fig. 2, see data file description for the cumulative siring data set for a key); Treatment (high vs. low nutrient resource additions); Plant (code name for the genotype included in the array); Sex (H - hermaphrodite, M - male); MVL (leaf mid vein length for the leaf subtending the inflorescence); Nflowers (total number of flowers produced per inflorescence); Year (year the genotype had been sampled from natural populations).
Cumulative_floweringBYsiring
The data set contains the data used to generate Figure 1, and to analyse the association between flower production and siring success. Column names are as follows: Treatment (levels of the nutrient resource addition treatment - High and Low); Array (label for the mating array); CumFlws (cumulative number of male flowers produced by the focal male per day for the duration the array was set up); CumSire (cumulative number of seeds sired by the focal male over the course of the array).
PropSiring
These data correspond with those presented in Fig. 2. Column labels: Array (label for array); Trt (level of the nutrient resource addition treatment - High vs. Low); Mflws (the total number of flowers produced by the focal male in the array); Hflws (the total number of hermaphrodite flowers produced by all hermaphrodites per array); Totflws (the sum of Mflws and Hflws); Mprog(the total number of seeds sired by the focal male per array); TotProg (the total number of seeds genotyped per array).
SiringCountData
These data were used to evaluate overall differences in the number of seeds sired by males vs. hermaphrodites. Column labels are: Array (label for the mating array); Treatment (level of the nutrient resource addition treatment - High vs. Low); SexofSire (plant sex (male or hermaphrodite) to correspond with the data in the next column; Progeny (the number of seeds sired by the focal male, or the average number of seeds sired by the hermaphrodites in each array); Fflowers (the total number of female flowers available for siring opportunities in each array).
MomType
These data were used to conduct an analysis of deviance between the identity of the father (male vs. hermaphrodite) and identity of the mother (female vs. hermaphrodite) using a contingency table approach. The column labels are: Treatment (levels of the nutrient resource addition treatment - High vs. Low); Father (the sex of the father that sired the seeds genotyped in the paternity analysis - M for male, H for hermaphrodite); Mother (the sex of the mother that produced the seeds genotyped for paternity analysis); Count (the total number of seeds screened for each treatment and sex combination).