Ecosystem drivers of leaf traits and resource-use strategies in nymphaeids

Macrophytes are a fundamental component of aquatic ecosystems by linking riparian (e.g. terrestrial) to aquatic (e.g. pelagic, deep water) domains and offering multiple services. However, eutrophication, invasive species and habitat degradation are threatening macrophytes and terrestrial-wet-aquatic ecotones globally. In this context, approaches based on functional traits (i.e. specific features measured at individual level) are often implemented to quantify plant responses to ecosystem conditions. Here, we carry out a trait-based investigation on local to regional scale (within and among lakes), focusing on four species of nymphaeids: Nelumbo nucifera Gaertn., Nuphar lutea (L.) Sm., Nymphaea alba L. and Nymphoides peltata (S.G.Gmel.) Kuntze. Our aim is to gain insights into resource use strategies of nymphaeids (including leaf economic spectrum and biochemistry), integrated with spectral reflectance data at leaf to canopy scales and genetic information, in response to varying stressors and drivers. Data were collected from four lakes in Central-Northern Italy, covering a gradient of physical-chemical water and sediment conditions. We found evidence of wide variability in traits among species, as well as considerable species plasticity within and across sites. Site-specific conditions - mainly driven by surrounding land uses - seem to determine intraspecific differentiation especially in structural traits (e.g. leaf area), while biochemical traits (e.g. pigments) show a high local variability, which is probably due to plotspecific conditions. This evidence suggests a relevant environmental filtering force on resource allocation in response to abiotic factors and reinforces the key contribution of intraspecific trait variability to shed light on spatial patterns within and among ecosystems.