Experimental landscapes
The 3D printed experimental arenas were made from PLA plastic and
consisted of four habitats patches (circular: c . 7cm in diameter
and 1.5cm in height) connected by four corridors (c . 28cm in
length and 1cm in width) in a square (2x2) configuration, with each
habitat patch connected by two corridors. Both habitat patches and
corridors were filled with a mixture of plaster of Paris and black dye
(c. 0.5cm in thickness). Plaster of Paris acts as a substrate for the
Collembola to live on which keeps moisture, whilst the black dye makes
Collembola more visible for counting (Li et al. 2021). To avoid moisture
wicking between the different components of the landscapes (patches and
corridors), plastic baffles were printed allowing the moisture of the
corridors to be manipulated separately to the moisture of the patches
(Fig. 1a).
As Collembola are delicate and not easy to handle, they were inoculated
into the four patches of each landscape by tapping individuals (mean ±
SD = 423 ± 317) into each mesocosm. During the experimental set up a
potential confounding effect was accidentally introduced whereby
microcosms were not randomly assigned to treatment after introducing the
Collembola. This may have caused systemic differences in population
level responses to treatments (Fig. 2), which we have attempted to
account for by including microcosm as a random effect in the statistical
models. Thus, food (dry dead yeast) was added to each patch each week
(7±2mg mean±SD, n=30) throughout the experiment, and thus food was not a
limiting factor to growth. Collembola were reared in the microcosms for
three weeks prior the start of the treatments to allow populations to
stabilise, with 2ml water and 7mg of food added each week to each patch.
Clear lids were used to cover the microcosms and stop them drying out
too quickly, and all microcosms were placed in dark rearing room to
minimise light exposure.