Study sites

Seeds were collected from August to September 2018 (to avoid seasonal variability) from eight populations of I. capensis in Poland. We sampled the entire Polish range of this species from all types of habitats, from natural (alder carrs, hydrophilous tall herb communities along rivers, near water seepages, and along the banks of the Szczecin Lagoon) to anthropogenic (tall herb communities along roadside ditches, transformed forests along artificial canals) (Table 1, Fig. 1). The studied populations were also subject to different lighting conditions, which were scored using a 3-point scale: plants which grew in willow forests and the understory of alder carrs were strongly shaded (3), while those from tall herb communities were partly shaded by solitary trees (2) or exposed to full sun (1). As the height of I. capensis specimens, the location of capsules within the plant (main stem vs. branches), and their derivation from flowers of various types (cleistogamous vs. chasmogamous) may affect seeds weight (Waller, 1982), the seeds for our study were collected always from the main stems of 8–10 plants of similar (average for the population) height and from capsules derived from chasmogamous flowers, to minimize the bias. Species nomenclature was adopted from Euro+Med PlantBase (Euro+Med PlantBase, 2019).

Satellite map data ©2019 Google, Modifed using CorelDRAW 18. For explanation of symbols, see Table 1.