Results of plant CNP stoichiometry

Results of chemical analysis to determine the carbon-nitrogen-phosphorus stoichiometry of plant fragments that had not been used in feeding trials. ID [= unique identifier of the record], speciesName [= name of plant species], Replicate [= replicate id within a species], P% [= phosphorus content in % of plant dry mass], C% [= carbon content in % of plant dry mass], N% [= nitrogen content in % of plant dry mass

Results of caterpillar feeding trials

The results of the caterpillar (using Parapoynx stratiotata) feeding trials were conducted in the laboratory in the Netherlands and are located in a tab-separated text file. Respectively, column headings are: ID [= unique identifier of each record], species [= plant species fed upon by caterpillar], fresh biomass (g) [= initial plant mass offered to caterpillar], fresh biomass after (g) [= remaining plant mass], FWeaten (g) [= fresh plant biomass lost during feeding trial], 450nm [= spectrophotometric absorbance at 450 nm after experiment], TON [= oxidized nitrogen in water in mg/L],NH4 [= total ammonium in water in mg/L], PO4 [= o-phosphate in water in mg/L], NO2 [= nitrite in water in mg/L], FW caterpillar end (mg) [= final fresh weight of combined caterpillars in milligrams], P% [= plant phosphorus content in % of plant dry mass of plant remainder after feeding], C% [= plant carbon content in % of plant dry mass of plant remainder after feeding], N% [= plant nitrogen content in % of plant dry mass of plant remainder after feeding], TPC% [= plant total phenolics content in % of plant dry mass of plant remainder after feeding], caterpillar.DM [= caterpillar dry mass after feeding],caterpillar.C [= caterpillar carbon content in % of its dry mass after feeding]caterpillar.N [= caterpillar nitrogen content in % of its dry mass after feeding], caterpillar.P [= caterpillar phosphorus content in % of its dry mass after feeding

Native and Non-Native Plants Provide Similar Refuge to Invertebrate Prey, but Less than Artificial Plants

<div><p>Non-native species introductions are widespread and can affect ecosystem functioning by altering the structure of food webs. Invading plants often modify habitat structure, which may affect the suitability of vegetation as refuge and could thus impact predator-prey dynamics. Yet little is known about how the replacement of native by non-native vegetation affects predator-prey dynamics. We hypothesize that plant refuge provisioning depends on (1) the plant’s native status, (2) plant structural complexity and morphology, (3) predator identity, and (4) prey identity, as well as that (5) structurally similar living and artificial plants provide similar refuge. We used aquatic communities as a model system and compared the refuge provided by plants to macroinvertebrates (<i>Daphnia pulex</i>, <i>Gammarus pulex</i> and damselfly larvae) in three short-term laboratory predation experiments. Plant refuge provisioning differed between plant species, but was generally similar for native (<i>Myriophyllum spicatum</i>, <i>Ceratophyllum demersum</i>, <i>Potamogeton perfoliatus</i>) and non-native plants (<i>Vallisneria spiralis</i>, <i>Myriophyllum heterophyllum</i>, <i>Cabomba caroliniana</i>). However, plant refuge provisioning to macroinvertebrate prey depended primarily on predator (mirror carp: <i>Cyprinus carpio carpio</i> and dragonfly larvae: <i>Anax imperator</i>) and prey identity, while the effects of plant structural complexity were only minor. Contrary to living plants, artificial plant analogues did improve prey survival, particularly with increasing structural complexity and shoot density. As such, plant rigidity, which was high for artificial plants and one of the living plant species evaluated in this study (<i>Ceratophyllum demersum</i>), may interact with structural complexity to play a key role in refuge provisioning to specific prey (<i>Gammarus pulex</i>). Our results demonstrate that replacement of native by structurally similar non-native vegetation is unlikely to greatly affect predator-prey dynamics. We propose that modification of predator-prey interactions through plant invasions only occurs when invading plants radically differ in growth form, density and rigidity compared to native plants.</p></div

Refuge provisioning by native and non-native aquatic plants.

<p>Mean ± SEM survival (%) of (<b>A</b>) <i>Daphnia pulex</i>, (<b>B</b>) damselfly larvae and (<b>C</b>) <i>Gammarus pulex</i> under mirror carp predation (<i>Cyprinus carpio</i>; n = 8) and of (<b>D</b>) <i>Gammarus pulex</i> under <i>Anax imperator</i> predation (n = 9) in low (white bars; 300 shoots m^-2) and high density (grey bars; 800 shoots m^-2) plant monocultures grouped into native (left side) and non-native species (right side). Horizontal bars represent the groups that were compared. Comparisons between two groups are shown as non-significant (ns) or one to three asterisks (GLMM Wald χ² tests: * <i>P</i> < 0.05; ** <i>P</i> < 0.01; *** <i>P</i> < 0.001), whereas lowercase letters indicate significance among three or more groups (GLMM simultaneous inference post hoc; <i>P</i> < 0.05). ‘NA’ indicates not available.</p

Information on the real and artificial aquatic plants used.

<p>Overview of the aquatic plants in the predation trials along with information regarding the wet and dry weight of the native, non-native and plastic plant monocultures as well as their biomass, percent volume infested (PVI), morphological description and fractal dimension.</p><p>Information on the real and artificial aquatic plants used.</p

Refuge provisioning by artificial aquatic plants.

<p>Mean ± SEM survival (%; n = 8) of the benthic crustacean (<i>Gammarus pulex</i>) predated upon by mirror carp (<i>Cyprinus carpio carpio</i>) in the presence of artificial plant analogues of varying complexity and in low (white bars; 300 shoots m^-2) and high density (grey bars; 800 shoots m^-2). Horizontal bars indicate the groups that were compared, where comparisons between two groups are shown as either non-significant (ns) or their significance using asterisks (GLMM Wald χ² tests: * <i>P</i> < 0.05; ** <i>P</i> < 0.01; *** <i>P</i> < 0.001) and lowercase letters for significance among three or more groups (GLMM simultaneous inference post hoc; <i>P</i> < 0.05).</p