Fitness and growth of the ephemeral mudflat species Cyperus fuscus in river and anthropogenic habitats in response to fluctuating water-levels

Abstract

Cyperus fuscus is a representative of threatened ephemeral wetland plant communities in summer-dry shoreline habitats. We compared variation and plasticity in traits related to fitness and growth of plants germinating from the soil seed bank and established plants from river and secondary anthropogenic habitats. Plants from sites at rivers, fishponds and fish storage ponds were cultivated and selfed to get homogenous seed material for a germination and an environmental manipulation experiment involving three different water regimes. Differences in traits and their plasticities were evaluated by means of linear mixed models. Cyperus fuscus followed a low-oxygen escape strategy when flooded. Seeds of plants derived from the soil seed bank germinated faster than seeds of plants derived from established plants suggesting that short-term selection of genotypes is mediated by the particular conditions on the site during germination. The experiment revealed significant differences between river and secondary habitats as well as between the soil seed bank and established plants. For example, plants from river habitats produced the highest number of culms with inflorescences. The difference was most evident under partial submergence. Plants from fish storage ponds rapidly reached the reproductive phase, but produced less culms with inflorescences. This seemingly allows them to cope with numerous and irregular disturbances and intensive substrate moisture changes. Our results suggest that populations have adapted to conditions at secondary habitats provided by fish farming during the last centuries.

Genetic variation in an ephemeral mudflat species: The role of the soil seed bank and dispersal in river and secondary anthropogenic habitats

“…It has been hypothesized that novel habitats created by humans may provide evolutionary opportunities for rapid adaptive niche shifts associated with lineage divergence (e.g., Baduel, Hunter, Yeola, & Bomblies, 2018; Kamdem et al, 2012). Previously, we found evidence for phenotypic differentiation between primary and secondary habitats in our study species suggesting that adaptive evolution has taken place (Böckelmann et al, 2017). Plants from river habitats tolerated flooding events that usually occur unpredictably regarding particular date and intensity in early summer on riverbanks better than plants from the anthropogenic pond types.…”

“…Cyperus fuscus is an annual, self‐compatible, and highly plastic graminoid native to the Mediterranean and temperate Eurasia (Böckelmann et al, 2017; East, 1940). It is a typical mudflat species growing on muddy, sandy, or gravelly substrata on mudbanks of rivers, lakes, pools, and ponds, which are usually exposed in later summer (class Isoëto‐Nanojuncetea; Hejný, 1960).…”

“…The populations of the three habitat types are the same as those used for the environmental manipulation experiment of Böckelmann et al (2017). For each of these populations, soil samples from two depths [0–5 cm deep soil (shallow seed bank) and 5–15 cm deep soil (deep seed bank)] and ripe seeds were collected from three plots per locality in summer 2012 and stored in the dark at 6°C for approximately six months.…”

“…Similarly, the ripe seeds collected from above‐ground individuals in the field were seeded and leaf samples from the grown plants were put into silica gel. More details of the sampling procedure are given in Böckelmann et al (2017). Leaf samples of the additional populations across Europe were taken in the field, where they were immediately put into bags with silica gel for drying.…”

“…Nevertheless, the evolutionary forces that shape the genetic structure of species may be altered in anthropogenic versus natural habitats, which may provide opportunities for adaptive niche shifts (Kamdem et al, 2012). Divergent environmental conditions such as the frequency and intensity of flooding during plant growth are expected to exert divergent selection pressures in river and anthropogenic wetland habitats, which may lead to phenotypic differentiation (Böckelmann, Tremetsberger, Šumberová, Grausgruber, & Bernhardt, 2017). Genetic and/or epigenetic differentiation could underlie such differential adaptation (Bossdorf, Richards, & Pigliucci, 2008).…”