Data from: Inter- and intrapopulation resource use variation of marine subsidized western fence lizards
Data files
Feb 01, 2024 version files 12.65 KB
Abstract
Marine resource subsidies can alter consumer dynamics of recipient populations in coastal systems. The response to these subsidies by generalist consumers is often not uniform, resulting in inter- and intrapopulation diet variation and niche diversification that may be intensified across heterogeneous landscapes.
We sampled western fence lizards, Sceloporus occidentalis, from Puget Sound beaches and from coastal and inland forest habitats, as well as the lizards’ marine and terrestrial prey items to quantify marine and terrestrial resource use with stable isotope analysis (SIA) and mixing models.
Isotopic results reveal beach lizards had higher average δ13C and δ15N values compared to coastal and inland forest lizards, exhibiting a strong mixing line between marine and terrestrial prey items. Across five beach sites, lizard populations received 20 to 51% of their diet from marine resources, on average, with individual lizards ranging between 7% and 86% marine diet.
The hillslope of the transition zone between marine and terrestrial environments at beach sites was positively associated with marine-based diets, as beach sites with the steepest slopes had the highest percent marine diets. Additionally, within-beach variation in transition zone slope was positively correlated with the isotopic niche space of beach lizard populations. Together, these results demonstrate that the physiography of transitional landscapes can mediate resource flow between environments, and variable habitat topography promotes niche diversification within a lizard population.
Marine resource subsidization of Puget Sound beach S. occidentalis populations may facilitate occupation of the northwesternmost edge of the species range.
Human impacts to the physiography of Puget Sound beaches, such as shoreline armoring, may influence the quantity of driftwood habitat available to support the unique ecology of beach-dwelling S. occidentalis. This highlights the importance of shoreline restoration, and conservation of intact beach habitat.
README: Inter and intrapopulation resource use variation of marine subsidized western fence lizards
Authors: Alexi Ebersole1, Marie E. Bunker1, Stacey L. Weiss1, Kena Fox-Dobbs2
Department of Biology1 and Geology2 University of Puget Sound, Tacoma, WA, USA 98416
## Data collection methods overview
* We collected data from seven western fence lizard (Sceloporus occidentalis) populations across 3 different habitats in Washington State, USA. For stable isotope analysis, we removed a small piece of tail tissue from the lizards which we processed between the University of Puget Sound, University of Washington Stable Isotope Laboratory, and the University of Colorado Boulder Earth Systems Stable Stable Isotope Laboratories. We collected arthropod prey and plant samples for stable isotope analysis and lizard diet reconstruction. We measured lizard body length and weight data by hand using rulers and spring scales in the field. To model the diets of lizards and quantify marine diet contribution, we used the MixSIAR R package and alpha value equation using our lizard tissue, prey, and plant stable isotope data.We used the SIBER R package to compare the isotopic niche space of lizard populations, and also used Google Earth imagery to examine the slope of transition zone between marine and terrestrial environments.
########################################################################
## Included files:
lizard_data.csv: Includes raw carbon and nitrogen stable isotope data for western fence lizard (Sceloporus occidentalis) lizard tissue samples used in the study, lizard body size and length data, in addition to statistical analyses quantifying marine diet contributions
# Site - The name of the S. occidentalis study population in Washington State
# Lizard ID - The unique toe-clip number assigned to individual S. occidentalis
for identification and recapture purposes
# δ13C (permil) - The carbon stable isotope ratio (13C:12C) of S. occidentalis tail tissue
# weight %C - The percent weight of carbon contained in the S. occidentalis tail tissue sample
# δ15N (permil) - The nitrogen stable isotope ratio (14N:15N) of S. occidentalis tail
tissue
# weight %N - The percent weight of nitrogen contained in the S. occidentalis tail
tissue sample
# C/N ratio - The ratio by weight of carbon versus nitrogen contained in the S. occidentalis tail tissue sample
# % marine diet MixSIAR (claw&claw TEF) - the percent of diet from marine derived nutrients for individual S. occidentalis, estimated with the MixSIAR R package, using claw Δ13Ctissue-diet, and claw Δ15Ntissue-diet diet to tissue discrimination values
# % marine diet MixSIAR (skin&claw TEF) - the percent of diet from marine derived nutrients for individual S. occidentalis, estimated with the MixSIAR R package, using skin Δ13Ctissue-diet, and claw Δ15Ntissue-diet diet to tissue discrimination values
# % marine diet alpha - the percent of diet from marine derived nutrients for individual S. occidentalis, estimated with the alpha equation: ? = {[(δ13Cconsumer – Δ13C) – δ13Cterrestrial]/(δ13Cmarine – δ13Cterrestrial)}*100
# sex - the sex of the lizard was determined (M = male, F = female) using the post anal scales of the lizard
# svl.mm - the snout to vent length of the lizard in millimeters
#bmass.g - the body mass of the lizard in grams
##############################################################################
plant_data.csv: Includes raw carbon and nitrogen stable isotope data for plant samples used in the study. At the inland site we collected foliage of seven abundant grass taxa to confirm the absence of C4 vegetation. Algae and blackberry samples were used in the alpha equation to calculate the contribution of marine resources in lizard diets
# Site - the name of the S. occidentalis study population in Washington State
# Sample ID - the name of plant sample
# δ13C (permil) - the carbon stable isotope ratio (13C:12C) of the plant sample
# weight %C - the percent weight of carbon contained in the plant sample
# δ15N (permil) - the nitrogen stable isotope ratio (14N:15N) of the plant
# weight %N - the percent weight of nitrogen contained in the plant sample
# C/N ratio - the ratio by weight of carbon versus nitrogen contained in the plant sample
##############################################################################
prey_data.csv: Includes raw carbon and nitrogen stable isotope data for arthropod prey item samples used in the study for lizard diet reconstruction and analyses
# Site - the name of the S. occidentalis study population in Washington State
# Sample ID - the name of the arthropod prey item sample. For example, “LCB.tidal.arth1” refers to a intertidal arthropod collected along the shoreline at the Lower Chambers Bay study site, while “LCB.terrest.arth7” refers to a terrestrial arthropod collected above the wrack line on the bank at Lower Chambers Bay.
# Family - the taxonomic family of the arthropod samples
# δ13C (permil) - the carbon stable isotope ratio (13C:12C) of the arthropod sample
# weight %C - the percent weight of carbon contained in the arthropod sample
# δ15N (permil) - the nitrogen stable isotope ratio (14N:15N) of the arthropod
# weight %N - the percent weight of nitrogen contained in the arthropod sample
# C/N ratio - the ratio by weight of carbon versus nitrogen contained in the arthropod sample
##############################################################################
transition_zone.csv: The slope of the transition zone between marine and terrestrial environments (e.g., unvegetated bluff, open meadow, coastal forest) calculated as the elevation relief along five 75 m transects that extended inland perpendicular from sea level (0 m asl) along the shoreline where lizards were captured. Measurements were repeated 5 times at each study site.
# Site - the name of the S. occidentalis study population in Washington State
# Transition zone slope - the rise/run of the transition zone between marine and terrestrial environments along 75 m transects. Calculated using Google Earth imagery.
##############################################################################
siber_data.csv: Includes data from the Stable Isotope Bayesian Ellipses in R (SIBER) package that we used to estimate and compared the isotopic niche space of the beach lizard populations
# Site - the name of the S. occidentalis study population in Washington State
# SEAc - The “Standard Ellipse Area” (SEA) of S. occidentalis populations calculated with the SIBER package in R, that is corrected for small sample sizes to estimate isotope niche space (SEAc).
##############################################################################
Additional notes:
* “.” signifies missing data in the spreadsheet
Methods
Sceloporus occidentalis tail tissue, insects, and plant material were collected from several locations around Washington state in the summer months of 2020 and 2021. Stable isotope analyses were performed on these samples at the University of Washington Stable Isotope Laborator and the University of Colorado Boulder Earth Systems Stable Isotope laboratoty using methods described in Pringle and Fox-Dobbs, 2008. More detailed methodology can be found in Ebersole et al, "Inter- and intrapopulation resource use variation of marine subsidized western fence lizards," or in the attached README file.