10.5061/DRYAD.8CQ43
Reddin, Carl J.
Queen's University Belfast
Bothwell, John H.
Queen's University Belfast
Durham University
O'Connor, Nessa E.
Queen's University Belfast
Trinity College
Harrod, Chris
University of Antofagasta
Data from: The effects of spatial scale and isoscape on consumer isotopic
niche width
Dryad
dataset
2018
scale dependence
niche space
mussel
limpet
Marine
Ulva spp.
Patella vulgata
Fucus serratus
Trophic ecology
stable isotope ecology
ellipse
Mytilus spp.
Littorina littorea
Laminaria digitata
2018-11-20T00:00:00Z
2018-11-20T00:00:00Z
en
https://doi.org/10.1111/1365-2435.13026
191445 bytes
1
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
1. The mean and variance of ecological variables are dependent on sampling
attributes such as the coverage of environmental heterogeneity (sampling
extent) and spatial scale. Trophic niche width is often approximated by
bulk tissue stable isotopes of C and N, i.e. the population isotopic
niche. However, recent studies suggest that environmental heterogeneity
(experienced by individuals) may be more important in defining the
isotopic niche width than trophic variability. We hypothesised that
isotopic niche width will increase monotonically with spatial scale,
largely produced by environmental variation, e.g. nutrient source. 2. To
refine this hypothesis, by describing the shapes of isotope scaling
curves, we explored a previously published dataset describing three
Chilean intertidal species representing different feeding guilds (grazing
snails, suspension feeding mussel). We tested these hypotheses on a new,
larger dataset describing three functionally-analogous intertidal species
from Northern Ireland. We generated isotopic variance-area curves from a
spatially-explicit bootstrap and investigated the scale-dependency of
environment-isotope relationships, including wave exposure and sub-habitat
heterogeneity. 3. Spatial scale explained 50% of the variance in
population isotopic niche widths (bivariate C-N ellipse area) by simple,
non-linear relationships. Finer scales (< 1 to 10 km lag) accounted
for most variance. Scale dependence was strong for ẟ15N variance, of which
> 40% was explained by modelling linear coefficients. A ẟ15N
baseline gradient, or isoscape, dominated ẟ15N variance scaling patterns,
from sheltered, terrestrially-influenced embayments to exposed,
pelagic-dominated coastline. Consumer ẟ13C variance had a weaker
scale-dependence, plateauing at mesoscales (> 20 km lag). 4. We
show that isotopic niche width is strongly dependent on sampling spatial
extent, which controls the environmental heterogeneity experienced by
individual consumers. Environmental heterogeneity must be accounted for
before isotopic niche width can be considered to accurately represent
trophic niche width. Studies conducted at different spatial scales are
likely to identify different environment-isotope relationships. 5. We
recommend that spatial scale should be incorporated into sampling designs
explicitly, easiest by maintaining a consistent lag distance or area
within which populations are sampled. Identified isoscapes can be
de-trended, where necessary.
Table S4. Northern Irish environment and consumers’ stable isotope
dataThis file contains all consumer (ME = Mytilus, LL = Littorina
littorea, PV = Patella vulgata) stable isotope values alongside
environmental variables for the site.FEreddinST4.csvTable S5. Northern
Irish macroalgal stable isotope data.This file contains macroalgal
(Laminaria digitata, Ulva spp., Fucus serratus) stable isotope
values.FEreddinST5.csvR code for isotope scaling curves and
plottingDirectories need changing. All files imported are also made in
this R code from the original data files. The file
'Covariogrammodels.csv' is attached separately for
consistencyIsotope scaling curves.RCovariogram model parametersThis file
is needed to plot the covariograms, but is also made in 'Isotope
scaling curves.R'Covariogrammodels.csvR code for modelling the effect
of sample sizeFiles needed for this code are either made within it or in
'Isotope scaling curves.R' from the original
data.SampleSizeModelling.R
Northern Ireland