Distribution of clonal growth forms in wetlands

Clonal multiplication is a predominant type of reproduction in wetland species. However, both wetlands and plant organs of clonal growth are diverse, thus due to different stress factors operating in various wetlands preponderance of plants with specific clonal growth organs (CGOs) can be expected. To test this hypothesis the CGO spectra of wetland communities of the Netherlands were analysed, including a bog, a fen, heathland, a floodplain, river beds, fresh water pools, open salt water and a salt marsh. Moreover, it was evaluated whether different CGOs are characterised by different functional traits (shoot cyclicity, persistence of connections between ramets, number of offspring produced per year and lateral spread per year) in wetland species. Data on types of CGO, i.e., epigeogenous and hypogeogenous rhizomes, fragments and budding plants, stolons, tubers and bulbs, root-splitters, root-sprouters and special adaptations (turions) as well as their functional traits, were taken from the CLO-PLA 3 database. CGO spectra of wetland communities were analysed using two methods: comparison of observed vs. expected CGO spectra based on the presence/absence data and multivariate analysis (CCA) for inter-community differences considering species frequency. Moreover, relationships between CGOs and their functional traits were tested using multidimensional contingency tables. Apart from 26% of non-clonal species, the majority of wetland species was rhizomatous (51%). Other types of CGO were represented in less than 10% of species and root-derived CGOs were underrepresented (<2%) in comparison with terrestrial habitats. Among communities, fresh water pools and open salt water hosted higher proportion of species with fragments (similar to 10%) and turions (similar to 30%). Multivariate analysis divided wetland communities along the disturbance and hydric (water) gradients. Highly disturbed communities (salt marshes) were characterised by non-clonal species and species with root-derived CGOs. Aquatic communities (fresh water pools and open salt water) hosted species with the ability to spread by fragmentation and turions, contrary to permanently wet communities (bog and wet heathland) with the prevalence of species with epigeogenous rhizomes. It was also confirmed that the CGOs of wetland species differed in their traits. The most important functional trait characterising individual CGOs in the wetland flora was the degree of lateral spread (explained variability: 53%) followed by duration of persistence of connections between ramets (explained variability: 74%), which is in accordance with earlier distinguished strategies of clonal growth: integrator/splitter and spreading/non-spreading clones. (C) 2009 Elsevier B.V. All rights reserved.