DOI: 10.5061/dryad.0vt4b8h4j
title: Apparent differential phenotypic responses by kelp forest grazers to disease-driven removal of sea star predators; [Data: Tegula shell morphology, GSI, stable isotope analysis]

description: The potential for aquatic gastropods to display phenotypic plasticity in
 response to predator cues is well documented in experimental settings.
 However, long-term physiological responses to predator exposure are
 difficult to evaluate at large scales in the field. Thus, it is currently
 unclear (a) the extent to which comparatively dilute predator cues
 experienced by natural snail populations influence morphometric
 development and (b) whether energetic costs associated with defensive
 morphology have allometric impacts on other life history characteristics
 (e.g., reproduction). The 2013 sea star wasting disease outbreak in
 central California, USA provided a unique framework for a large-scale
 natural predator removal experiment, comparing shell morphometrics and
 gonadosomatic index of subtidal Tegula turban snail populations at kelp
 forest sites where local predatory sea stars were completely absent (SS-)
 with paired sites maintaining low predator densities (SS+). All three
 snail species displayed significantly higher proportional allocation to
 shell mass at SS+ locations and concomitantly higher reproductive
 allocation with predators absent (SS-). Dietary stable isotope analysis
 suggests this may be partially an energetic consequence of behavioral
 grazing shifts displayed by snails following predator release.
 Interestingly, morphometric shifts in shell structure differed among the
 three Tegula species, and appeared closely related to species-specific
 predator avoidance strategies.
description: Dataset includes shell morphometric measurements and tissue (C
 & N) stable isotope analysis from subtidal
 <em>Tegula </em>turban snails (<em>T. brunnea, T.
 montereyi, T. pulligo; t</em>otal N = 300<em>) 
 c</em>ollected from three regions along the central California
 coast. Field collections were conducted in 2014-2015 after the widespread
 outbreak of sea star wasting disease, and snails were collected
 haphazardly by divers on SCUBA from paired sites within each region,
 selected based on the presence (SS+) and absence (SS-) of predatory sea
 stars. Detailed methods for data collection and processing are published
 in Wetmore & Anderson (2024). 
description: # Apparent differential phenotypic responses by kelp forest grazers to
 disease-driven removal of sea star predators --- GSI, shell morphology
 & stable isotope data for Tegula spp. in response to sea star wasting
 disease ## Description of the data and file structure Contains data on
 Tegula species, collection location, shell morphometric measurements, and
 biomass measurements for predator present (SS+) and predator absent (SS-)
 study sites in three central California study regions, with measurements
 in columns and individual samples in rows. ### Variables SampleID- Unique
 numerical identifier (1-300) randomly assigned to each individual snail at
 time of sample processing Area- Categorical identifier designating the
 study region where an individual was collected: Monterey
 ("MON"), Big Sur ("BIS"), San Luis Obispo
 ("SLO") SeaStar- Categorical identifier designating whether an
 individual was collected from a paired SS+ site with predatory sea stars
 present ("Present") or SS- site with predatory sea stars absent
 ("Absent") Vert- Categorical identifier designating whether an
 individual was collected from vertical habitat on the stipes and fronds of
 giant kelp ("Vertical") or from benthic habitat in understory
 algae ("Benthic") Spec- Categorical identifier designating* *one
 of three Tegula* species: T. brunnea* ("BRU"),* T. montereyi*
 ("MON"),* T. pulligo* ("PUL") Sh_H- Shell height
 (measured in mm) Sh_W- Basal shell width (measured in mm) Apert_W-
 Aperture height (measured in mm) Apert_H- Aperture width (measured in mm)
 Sh_HW- Shell height: width ratio (= Aperture height/Aperture width)
 Wt_Shell- Shell biomass (measured in g) C (Raw)- Tissue stable isotope
 ratio of 13C (‰, raw laboratory data)  N (Raw)- Tissue stable isotope
 ratio of 15N ( ‰, raw laboratory data)  C (Correct)- Tissue stable isotope
 ratio of 13C (‰, corrected for isotopic fractionation using a trophic
 enrichment factor of 1.5‰)  N(Correct)- Tissue stable isotope ratio of 13C
 (‰, corrected for isotopic fractionation using a trophic enrichment factor
 of 1.5‰)  GSI- Gonadosomatic index, calculated as (Gonad Dry Weight/Total
 Soft Tissue Dry Weight) x 100 Ripeness- Categorical (binary numerical)
 identifier designating whether an individual displayed ripe gonads: (1)
 ripe or (0) not ripe Sex- Categorical identifier designating the sex of an
 individual: ("F") Female or ("M") Male
 SexCode- Categorical (binary numerical) identifier designating the sex of
 an individual: (1) Female or (0) Male SI- Shell index, calculated as
 (Shell Weight/Total [Shell + Soft Tissue] Dry Weight) x 100 Wt_Tot- Total
 biomass, including Shell Weight + Soft Tissue Dry Weight (measured in g)
 Wt_Soft- Total (dry weight) biomass of all soft tissue (measured in g)
 Wt_Gon- Total (dry weight) biomass of gonad tissue (measured in g)