Intraspecific leaf trait variation of the heterophyllous amphibious plant Luronium natans: a trait-based study

Abstract

Heterophylly, a type of intraspecific trait variation (ITV), is commonly observed in aquatic and amphibious plants. In this study, we focused on Luronium natans (L.) Raf., as a model species to investigate ITV, specifically looking at variations within different leaf types. The objective was to test general hypotheses regarding ITV across various leaf traits. We collected 210 leaves from the homogeneous environments of softwater lakes in northwestern Poland to measure six leaf traits: leaf area (LA), leaf dry weight (LDW), specific leaf area (SLA), leaf dry mass content (LDMC), circularity, and leaf width/length ratio (shape traits). These leaves were categorized into three types based on the shoot: heterophyllous shoots with floating leaves (HF), heterophyllous shoots with submerged leaves (HS), and submerged rosettes with linear leaves (S). Significant differences were observed in LA and LDMC within these leaf types and in SLA between HF and S types. ITV within each shoot type exhibited a wide range of variation, particularly in LA, LDW, SLA, and LDMC, with shape traits displaying stronger variability than functional traits. Our results indicate lower ITV of functional leaf traits within the same heterophyllous shoots compared to fully submerged leaves in a rosette form. We also noted negative correlations between SLA-LDMC and LA-circularity trait pairs, suggesting a variation–covariation pattern in leaf traits with minimal influence from water environmental factors.