DOI: 10.5061/dryad.jm63xsj8q
title: Data from: Urbanization-driven climate change increases invertebrate lipid demand, relative to protein—a response to dehydration

description: 1. Climatic change alters not only animal energy balance, but also water
 balance, but this latter topic has received less attention. Water can be
 obtained through consumption of moist food and metabolism of dry food. The
 breakdown of carbohydrates, lipids, and proteins can produce metabolic
 water. Metabolism of lipids produces large amounts of water, whereas
 excretion of nitrogenous waste related to protein metabolism requires
 water losses. 2. Here we tested the hypothesis that climatic shifts
 associated with urbanization influences animal lipid demand relative to
 protein, due to shifts in water balance. 3. We placed artificial diets
 high in lipid or protein, and either with or without supplemented water,
 at 16 pairs of sites along an urbanization gradient in Toledo, OH, USA. 4.
 Lipid consumption, relative to protein, increased with urbanization and
 mean temperature, but water supplementation reduced the magnitude of this
 association. Ants were ~50% of the observed consumers. 5. These results
 suggest that shifts in nutritional demand with climatic change are
 partially predictable from physiological first principles related to water
 balance and nutrient metabolism. Because ants and other arthropods play
 key roles in many food webs and ecosystems, increased demand for lipids
 with urbanization or climate change could have major consequences for
 ecosystem services (e.g. urban waste removal, seed predation). Overall,
 our results suggest that warming related to urbanization increases animal
 demand for lipids, in part to maintain water balance, and this could have
 important implications for both animal health and ecosystem services.
description: <b><i>Study Sites</i></b>
 We selected 16 pairs of sites along an urbanization gradient
 (Figure 1, Table S1) within Toledo, OH and surrounding areas, examining
 the effects of impervious surface at local scales (50 m radius buffer)
 nested within a coarser scale (500 m radius buffer). Pairs were
 distributed throughout the region, no more than 15 km from the city center
 and no less than 3 km from each other. We selected each site pair by
 considering Toledo’s landscape features (e.g. impervious surface),
 accessibility of sites, and obtained permissions.
 <b><i>Diets and Consumption
 Measurement</i></b> Two artificial diets
 varying in lipid and protein were used in this study. The high-lipid diet
 was composed of 1:1:5 Protein: Carbohydrate: Lipid (P: C: L) and the
 high-protein diet had a 5:1:1 P: C: L ratio (Table S2). The protein
 components were composed of three different foods, because each food item
 did not offer an even and complete suite of amino acids. The diet’s final
 amino acid profile was validated by Lebensmittel Consulting Co, Fostoria,
 OH. Diets were deposited into clean metal bottlecaps and dried at 50°C in
 a drying oven (100L Gravity Oven, model 51030520, Fisher Scientific,
 Hampton, NH). Bottlecaps were then attached to small petri dishes (Figure
 S1) with a non-toxic glue dot (0.5” removable dot, Glue Dots Intl.,
 Germantown, WI). The bottlecaps were used for simplicity, while the small
 petri dish captured particles of food displaced from the bottlecap
 (modified from Clissold<i> et al.</i> 2014). Food-filled
 bottlecaps were placed inside small labeled plastic bags and then weighed
 to 0.01 mg (Micro Balance, model XPE56, Mettler Toledo, Columbus, OH).
 When diets were collected from the field, they were placed into the same
 bags as before. Diets were then dried inside their open plastic bags, dirt
 and frass was removed, then they were weighed a final time within their
 bags, with differences in mass indicating consumption.
 <b><i>Consumption
 Trials</i></b> Within each site, we
 selected six trees that were no less than 10 m apart and placed one set of
 consumption measurement materials at each tree (Figure S1). Each
 consumption measurement setup was comprised of a high-lipid and
 high-protein diet, a wet or dry water pillow (small pouches filled with a
 polymer that absorbs water; Cricket water pillows, Zilla, Franklin, WI),
 and a cage to exclude mammals. The addition of a water source allowed us
 to isolate the effects of water balance from metabolic rate on
 consumption. The wet and dry pillows were assigned to measurement
 locations in a stratified order at each site. Cages were made of hardware
 wire laced together with green floral wire and were fixed to the ground
 with landscape staples. To prevent rain or UV radiation from altering the
 pillows and diet, we placed a covering on the cages, made of a large petri
 dish sprayed with translucent UV protectant (Model 1305 Gallery Series,
 Krylon Products Group, Cleveland, OH). The lid could also be removed to
 make observations with minimal disturbance to the arthropods
 inside.<i> </i> We measured consumption
 three times at each site, from June – August 2016, shuffling the order in
 which sites were visited (pairs of sites were initially randomly assigned
 to one of four groups and within each group the order of site visits was
 reversed during the second trial).  Each measurement took place over three
 days: cages were placed on the first day, sites were visited during the
 morning and at night on the second day, to make observations of
 consumption, and cages were removed on the third day. Cages were not
 placed during a storm, but cages were visited on the second and third day,
 regardless of weather conditions.
 <b><i>Other
 Measurements </i></b> We measured
 temperature and humidity for each survey using three data loggers
 (Thermochron iButton, model DS 1923, Maxim Inc., San Jose, CA), placed
 within cages, spread evenly within a site. Each iButton was attached to a
 Styrofoam covering protecting it from solar radiation while allowing
 exchange with the atmosphere. With each visitation, we measured soil
 moisture (SM 150 soil moisture sensor, Dynamax, Houston, TX) and canopy
 cover (Mobile application software, HabitApp v. 1.1, Scrufster) three
 times, within 0.5 m of each cage. Canopy cover measures via HabitApp were
 verified to be comparable to a densiometer before use. We also identified
 invertebrates located in our experimental setups during each visit via
 photographs. Most of these photographs were taken by the same person (J.
 Becker) and this person performed all identifications from photographs.
 Some invertebrates moved too quickly to be photographed. These individuals
 were noted, but not included in analyses, due to the lack of
 identification. This could have resulted in under-recording highly-mobile
 taxa.
description: AvgPerImp = The mean percentage of impervious surface within 50 m
 radius of the site AvgLeaten = The mean amount of lipid
 consumed for that cage, across all dates, in mg
 AvgPeaten = The mean amount of protein consumed for that cage,
 across all dates, in mg AvgCeaten = The mean amount of
 carbohydrate consumed for that cage, across all dates, in mg
 AvgLtoP = The mean ratio of lipid to protein consumed for that
 cage, across all dates AvgLandCeaten = The mean amount
 of carbohydrate and lipid (combined) consumed for that cage, across all
 dates, in mg AvgLandCtoP = The mean ratio of
 carbohydrate and lipid (combined) to protein consumed for that cage,
 across all dates AvgRH = The mean relative humidity for
 a site, across all dates AvgCan = The mean % canopy
 cover for a cage, across all dates AvgSM = The mean
 volumetric soil moisture (%) near a cage, across all dates
 AvgTemp = The mean temperature for a site, across all
 dates