DOI: 10.5061/dryad.69p8cz9ds
title: Data from: The impact of a range-shifting predator is affected by prey preference and composition

description: Global biodiversity is undergoing a grand reshuffling with species across
 taxa and biomes shifting their ranges in response to climate change.
 Research on the ecological impacts of range-shifting species has
 prioritized linking the traits of the range-shifting species themselves to
 impacts, with studies giving more limited attention to the characteristics
 of the recipient community. Understanding how community composition and
 structure can alter the impact of novel species is important for
 predicting and managing ecological changes. We used the range-shifting
 predatory whelk Mexacanthina lugubris as a case study to investigate how
 the presence of shellfish prey might influence range shift impacts. We
 hypothesized that the structure of a recipient community would influence
 Mexacanthina lugubris’ consumptive effects. We tested this hypothesis via
 a field experiment in southern California, where we caged whelks at a
 gradient of densities and observed their predation on mussels, barnacles
 living on bare rock, and barnacles living on mussels over eight weeks. We
 found that Mexacanthina lugubris consumed barnacles on bare rock
 preferentially before consuming barnacles on mussels and mussels
 themselves. Our findings demonstrate that the composition and structure of
 the recipient community (i.e., the presence of mussels) can mitigate the
 overall impact of the range-shifting predator by altering prey
 accessibility. This context-dependent attenuation of predator effects
 highlights a form of apparent facilitation among prey and underscores the
 importance of considering recipient community traits when assessing or
 managing the ecological consequences of range-shifting species.
description: # Data from: The impact of a range-shifting predator is affected by prey
 preference and composition #### Kyle Suen #### 2025-06-26 [Access this
 dataset on
 Dryad](https://datadryad.org/submission/10.5061/dryad.69p8cz9ds) The
 dataset consists of data gathered from caging experiments that were
 conducted to monitor the consumption of prey by a range-shifting predator.
 At Dana Point and Scripps Reef, CA, cages were placed at the intertidal
 zone on plots that contained California mussels and acorn barnacles.
 Varying densities of *Mexacanthina lugubris*, a range-shifting predatory
 whelk that feeds on mussels and barnacles, were placed in the cages.
 Observations were made of their feeding rates and prey preferences over
 the course of eight weeks in order to see how the presence of mussels may
 affect the feeding habits of barnacles by *Mexacanthina lugubris*. Results
 were displayed via consumption rates of barnacles on bare rock and of
 barnacles on mussels, and through changes in preference for barnacles on
 bare rock by *Mexacanthina lugubris*. Consumption rates of mussels were
 also recorded. #### Description of the data and file structure Datasets
 are split into different files that create corresponding figures for the
 manuscript. 1a. “Fig2Data_DP.csv” and “Fig2Data_SR.csv” contain the data
 for Figure 2, which shows changes in the percent cover of live barnacles
 as a function of the average number of *Mexacanthina lugubris* in cages
 over a time range of two, four, six, and eight weeks. The data shows the
 change in the percentage of barnacles on bare rock that are living (Change
 % Living Bare from Initial) and the change in percentage of barnacles on
 mussels that are living (Change % Living Mussel), categorized by the
 density of whelks that are in the cage and by time of
 observation. “Fig2Data_DP.csv” contains the data collected at Dana Point,
 and “Fig2Data_SR.csv” contains the data collected at Scripps Reef. 1b.
 “Fig2Code.m” contains the code for Figure 2. The code generates two sets
 of graphs that show changes in the percent cover of live barnacles as a
 function of the average number of *Mexacanthina lugubris* in cages over a
 time range of two, four, six, and eight weeks. Each set of graphs shows
 changes on different substrates (bare rock and mussels), indicated by
 different colored lines, and at different sites (Dana Point and Scripps
 Reef). 2a. “Fig3Data_DP.csv” and “Fig3Data_SR.csv” contain the data for
 Figure 3, which shows changes in *Mexacanthina lugubris* preference for
 barnacles on bare rock compared to barnacles on mussels as a function of
 the average number of *Mexacanthina lugubris* in cages over a time range
 of two, four, six, and eight weeks. Preference is quantified through the
 selectivity index Chesson’s Alpha. Columns A-J in both datasets contain
 observation data gathered from the aforementioned caging experiment.
 Columns K-AD contain the calculations done to find the selectivity index
 for the observation data, with columns AA and AB showing Chesson’s Alpha
 for Barnacles on Mussels and Chesson’s Alpha for Barnacles on Bare Rock,
 respectively. “Fig3Data_DP.csv” contains the data collected at Dana Point,
 and “Fig3Data_SR.csv” contains the data collected at Scripps Reef. 2b.
 “Fig3Code.m” contains the code for Figure 3. The code generates two sets
 of graphs that show changes in *Mexacanthina lugubris* preference for
 barnacles on bare rock compared to barnacles on mussels as a function of
 the average number of *Mexacanthina lugubris* in cages over a time range
 of two, four, six, and eight weeks. Each set of graphs shows changes at
 different sites (Dana Point and Scripps Reef). 3a. Fig4Data.csv contains
 the data for Figure 4, which shows changes in the number of live mussels
 in a plot as a function of the average number of *Mexacanthina lugubris*
 over a time range of two, four, six, and eight weeks. Live mussels are
 listed in a column, categorized by the density of whelks that are in the
 cage, by time of observation, and by site. Note: In the table, values do
 not start until Row 58. The data for this figure and set of results comes
 from a larger dataset gathered from the lab on intertidal communities as a
 whole. As the figure only needed information on California Mussels, all
 other data were omitted. Other rows were not deleted as the code was set
 to gather data based on the original row number. 3b. “Figure4Code.m”
 contains the code for Figure 4. The code generates two sets of graphs that
 show the number of live mussels via consumption as a function of the
 average number of *Mexacanthina lugubris* in cages over two, four, six,
 and eight weeks. Each set of graphs shows changes at different sites (Dana
 Point and Scripps Reef). 4a. “FigA1Data.csv” contains the data for Figure
 A1 in Appendix 1, which shows the percent cover of live and dead barnacles
 on mussels within each plot at Dana Point and at Scripps Reef. The percent
 cover of barnacles on mussels is split into two columns: alive and dead.
 Columns are categorized by whether the observation was conducted in the
 field or via a photo and by site. 4b. “FigA1Code.m” contains the code for
 Figure A1. The code generates two bar graphs that show the percent cover
 of live and dead barnacles on mussels within each plot at Dana Point and
 at Scripps Reef. Bars are colored depending on whether the data was
 gathered from an observation of a photograph taken at the site or from an
 on-site observation.