Simulating biases in the timing of collection within flowering periods of individuals
In addition to biases towards collection of early or late individuals within a local population, botanists may also preferentially collect individuals from the early or late portion of their individual flowering period (i.e., individual collection bias). In some cases, collectors may preferentially collect individuals that are proximate to their peak flowering date because this is when the most flowers are displayed. In other cases, collectors may preferentially collect specimens that have only recently begun to flower, when floral structures may exhibit less damage from inclement weather or herbivores, or proximate to flowering termination in cases where the collector prefers specimens that include both flowers and fruits. Accordingly, for each population of each species, we simulated DOYs within each individual’s flowering period both at random (i.e., without bias) and with three different types of bias (Fig. S2). Unbiased collections were simulated by selecting a random date chosen uniformly within the flowering period of each sampled individual (Fig. S2a). To represent a bias toward collection of individuals close to their peak (median) flowering DOY, we sampled collection dates from a truncated normal distribution centered on an individual’s mean flowering date and with σ = 25% of the flowering duration for that species and location (henceforth referred to asmean-biased collection data , Fig. S2b). To represent a bias toward collection dates shortly after flowering onset (henceforth,onset-biased collection data ), we sampled collection dates from a truncated normal distribution centered on a date 25% earlier than the mean flowering onset date of that individual (σ = 25%; Fig. S2c). Finally, to represent a bias toward collection on dates shortly before flowering termination (henceforth termination-biased collection data ), we sampled collection dates from a truncated normal distribution centered on a date 25% later than the mean flowering onset date of that individual (σ = 25%; Fig. S2d). As with examinations of population-level bias, collection biases within the flowering periods of individuals were examined only for the subset of species for which phenological responsiveness to mean annual temperature equaled 4 days/˚C, intrapopulation variation was high (σ = 30), individual flowering duration was moderate (30 days), and no population-level bias was present.