Hetero-and conspecific interactions, nutrient availability, climate, habitat heterogeneity and disturbances can generate variation and spatial patterns of femaleness in plants. We assessed whether year, site, plant size, plant density and canopy area of conspecific neighbors influenced the expression and spatial aggregation of femaleness in Croton aff. wagneri, a monoecious shrub from dry shrublands of the inter-Andean valleys in Ecuador. We georeferenced in two sites (1,700 and 1,400 m.a.s.l) in five 10x10 m plots, within each site, the position of each Croton reproductive plant during first part of flowering season in two years, and measured their height, length and width. The femaleness index of each plant was determined by the number of female and male buds and flowers. Plant density was determined for each plot, along with the number of neighbors and the summed canopy area of conspecific neighbors (at 1.0, 2.0, and 2.5 m radius, and the five closest plants) from each focal plant. Croton's femaleness at the lower elevation site was greater than at the higher elevation site and increased with plant size and with canopy of the closest five neighbors. Soil at the lower elevation site had higher temperatures and lower water content. Aggregate patterns of femaleness were found in more plots at the lower elevation site. Our results indicate that location, plant size and canopies of conspecific neighbors of Croton can affect femaleness and its aggregation and support the hypothesis that femaleness can be influenced by facilitative interactions.

In November and December 2013 and 2016, the reproductive individuals were selected and counted in each 10x10 m subplot at two sites with different elevations (1,700 and 1,400 m). Plants with buttons and female and male flowers were considered. Plant density was calculated as number of reproductive individuals in 10x10 m plots (10 density values were obtained for each year). All individuals, reproductive and non-reproductive, were counted within 10x10 plots. In 2016 only breeding plants were counted, for this reason NA is registered in number of individuals in 2016.