10.5061/DRYAD.JM63XSJ8Q
McCluney, Kevin
0000-0002-3574-0354
Bowling Green State University
Becker, Jamie
Bowling Green State University
Data from: Urbanization-driven climate change increases invertebrate lipid
demand, relative to protein—a response to dehydration
Dryad
dataset
2020
2020-11-24T00:00:00Z
2020-11-24T00:00:00Z
en
27768 bytes
3
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
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.
Study Sites 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. Diets and Consumption
Measurement 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 et al. 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.
Consumption Trials 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. 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.
Other Measurements 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.
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