DOI: 10.5061/dryad.vx0k6dk4s
title: Predation by shell-breaking crabs on a marine gastropod along a latitudinal gradient in the SW Atlantic: Influence of extrinsic and intrinsic factors

description: Biotic interactions—and predation in particular—are thought to follow a
 latitudinal gradient, increasing towards the tropics; yet empirical
 evidence remains contradictory and largely based on studies from the
 Northern Hemisphere. Moreover, the role of environmental variables shaping
 latitudinal gradients of predation intensity has seldom been tested. Here,
 we quantify predation by shell-breaking crabs on modern shells of the
 marine gastropod Trophon geversianus along a latitudinal gradient
 (40°–54°S) on the SW Atlantic coast. We further evaluate how intrinsic
 factors (four shell morphometric traits) and extrinsic factors (seven
 environmental variables and the biogeographic region) jointly influence
 predation patterns. Fragmentation from crushing predation affected 37% of
 the shells (544 out of 1,480), with the most frequent damage types being
 major body whorl damage (28%), deep aperture chips (11%), and extensive
 aperture chips (6%). When analysed by biogeographic province,
 fragmentation increased significantly towards the south in the Magellan
 province. Notably, random forest modelling revealed that intrinsic
 factors—particularly shell size and thickness—were stronger predictors
 than extrinsic factors in driving latitudinal variability of
 shell-breaking crab predation. By highlighting the dominant influence of
 intrinsic factors over extrinsic ones, this study emphasises the crucial
 role of species-specific traits in shaping predator-prey interactions
 across biogeographic regions.
description: # Predation by shell-breaking crabs on a marine gastropod along a
 latitudinal gradient in the SW Atlantic: Influence of extrinsic and
 intrinsic factors Dataset DOI: 10.5061/dryad.vx0k6dk4s ### Description of
 the data and file structure Summary This dataset supports a study
 investigating how oceanographic variables influence the frequency of
 shell-breaking crab traces on the marine gastropod Trophon geversianus
 across 34 sites in the Southwestern Atlantic. The dataset integrates
 biological data from 1,480 shells with environmental estimates, enabling
 analyses of spatial trends and ecological drivers of predation. Contents R
 Scripts This repository includes a single R script that reproduces Figures
 3 to 6 from the study, detailing: Figure 3: PCA of oceanographic variables
 Figure 4: Latitudinal trends of individual oceanographic variables and PCA
 scores Figure 5: Latitudinal and biogeographic variation in crushing
 predation frequency Figure 6: Intrinsic and extrinsic drivers of predation
 via Random Forest analyses #### Files Included File Name Description
 **Dataset1.csv** Biological data: incidence of three types of
 shell-breaking predation traces on 1,480 Trophon geversianus shells
 **Dataset2.csv** Environmental data: six oceanographic variables estimated
 for 34 sites **Rscript_Nov2024.R** R script used to generate Figures 3–6,
 perform statistical analyses, and reproduce results from the manuscript
 ##### Variable Definitions **Dataset1.csv** | Variable | Description | |
 --------------- |
 ------------------------------------------------------------------- | |
 Site | Sampling site name (matches with Dataset2) | | Province |
 Biogeographic province: `"Mag"` (Magellan) or `"Arg"`
 (Argentinean) | | type2 | Binary variable (0 or 1): deep aperture chip | |
 type3 | Binary variable (0 or 1): extensive aperture chip | | type5 |
 Binary variable (0 or 1): major body whorl damage | | Shell.length | Shell
 length in mm | | Shell.Thickness | Shell thickness in mm | | Lat |
 Latitude of the site (decimal degrees, negative = South) | | Lon |
 Longitude of the site (decimal degrees, negative = West) |
 **Dataset2.csv** | Variable | Description | Units / Notes | | -------- |
 ----------------------------------- | ---------------------------------- |
 | Site | Sampling site name | Matches with Dataset1 | | lat | Latitude of
 the site | Decimal degrees (negative = South) | | lon | Longitude of the
 site | Decimal degrees (negative = West) | | sst | Sea surface temperature
 | ºC | | salinity | Sea surface salinity | Practical Salinity Scale (PSS)
 | | nflh | Normalised Fluorescence Line Height | mW·cm⁻²·µm⁻¹·sr⁻¹ | |
 oxygen | Dissolved oxygen concentration | mol·m⁻³ | | pH | pH of surface
 waters | Total scale | | exposure | Wave exposure index | Arbitrary units
 | Missing data: Missing values, if any, are encoded as blank cells or NA.
 #### Software and Libraries The following R libraries are required to run
 the script: psych FactoMineR rcompanion randomForestSRC Ensure all
 packages are installed prior to execution. Execution Instructions Set your
 working directory in R. Load Dataset1.csv and Dataset2.csv using the
 file.choose() prompt. Run the script to generate the PDF outputs:
 Fig3_nov2024.pdf Fig4_Malve_nov2024.pdf Fig5_nov2024.pdf Fig6_nov2024.pdf
 ### Data Sources All data were derived from original field collections and
 public oceanographic datasets (e.g., Bio-ORACLE). Specific estimation
 methods are detailed in the associated manuscript. Citation If you use
 this dataset, you are encouraged to cite the associated publication:
 Malve, M. et al. (2025). Predation by shell-breaking crabs on a marine
 gastropod along a latitudinal gradient in the SW Atlantic: influence of
 extrinsic and intrinsic factors. Proceedings B. Contact For questions
 about this dataset or its reuse, please contact: Mariano Malve
 \[[marianomalve@gmail.com](mailto:marianomalve@gmail.com)] Marcelo
 Rivadeneira
 \[[marcelo.rivadeneira@ceaza.cl](mailto:marcelo.rivadeneira@ceaza.cl)] ###
 Code/software **Software and Workflow** Software The dataset and
 associated analyses were conducted using R, a free and open-source
 statistical computing environment. All analyses were run using: R version
 4.3.1 RStudio (optional, for script editing and workflow management) To
 reproduce the figures and results, users must have R installed along with
 the following packages: Required R Packages | Package | Purpose | Version
 (tested) | | --------------- |
 ------------------------------------------------ | ---------------- | |
 psych | PCA parallel analysis and exploratory stats | ≥ 2.3.9 | |
 FactoMineR | Principal Component Analysis (PCA) | ≥ 2.8 | | rcompanion |
 Effect size statistics (Cramér's V, prop tests) | ≥ 2.4.30 | |
 randomForestSRC | Random forest classification for imbalanced data | ≥
 3.2.1 | ### Access information Data was derived from the following
 sources: BioOracle Database for environmental variables.