On the Measurement of Repair Frequency: How Important Is Data Standardization?

Dietl, Gregory P.; Kosloski, Mary Elizabeth

doi:10.2110/palo.2012.p12-076r

Cited by 26 publications

(26 citation statements)

References 88 publications

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“…Damage levels also differed: weakly ornamented individuals experienced shell damage likely to lead to the formation of a repair scar (assuming they managed to survive the attack) 58% of the time, whereas heavily ornamented individuals only sustained severe shell damage in 17% of attacks. The significant differences across morphologies in both mortality and shell damage highlight the importance of comparing similarly shaped shells when using repair scars as a proxy for selective pressure from predators (Dietl and Kosloski ). Despite differences in the likelihood of death or sustaining severe shell damage, the overall percentage of knobbed whelk individuals that were likely to form repair scars during our predation experiments was similar (21 vs 13% of weakly and heavily ornamented individuals, respectively; Table ).…”

Section: Discussionmentioning

confidence: 99%

“…There are many possible complications with using repair scars (e.g. variable growth rates, and thus exposure time to enemies, and size and shape variation may bias estimated frequencies [Schoener , Alexander and Dietl , , Kowalewski , Dietl and Kosloski ]). However, if the individuals used for comparisons can be standardized for any morphological or exposure‐time variation that influences the accumulation of repair scars, the calculated repair frequency or rate represents a biologically meaningful index of selective pressure that captures variation in shell‐damaging attacks experienced by animals in the wild (Dietl and Kosloski ).…”

Section: Methodsmentioning

confidence: 99%

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Anatomy of a cline: dissecting anti‐predatory adaptations in a marine gastropod along the U.S. Atlantic coast

2017

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The scope of anti‐predatory adaptation is expected to be greater in warm than in cold environments. High temperatures lower the costs associated with the production and maintenance of energetically expensive traits and enable ecological interactions to intensify. We tested this hypothesis by characterizing the expression of anti‐predatory morphology within a marine gastropod species (the knobbed whelk Busycon carica) over a large (> 1400 km) geographic area that spans more than 10°C annual temperature variation. We also conducted experimental predation studies with a powerful durophagous predator, the stone crab Menippe, to verify the anti‐predatory advantages of a heavily ornamented shell morphology (e.g. increased thickness, pronounced spines), and we used repair scar data to assess clinal variation in selective pressure from predators. We predicted that repair scar rates would be greatest in warm southernmost latitudes, and that expression of energetically costly anti‐predatory morphology would peak in concert with elevated predation pressures. Experiments confirmed that whelks with energetically costly, heavily ornamented shells had higher survivorship rates than those with weakly ornamented shells. As predicted, we also found that the expression of anti‐predatory traits was greatest in the southern part of B. carica's range. After standardizing shells for size, shape, and exposure time to enemies, repair scar rates also peaked to the south. Taken together, these results suggest that the expression of anti‐predatory traits along the geographic cline is governed by the interaction of two selective factors: temperature and predation, with the former acting as the ultimate control on the scope of adaptation both by escalating predation pressure in the southern part of B. carica's range and by physically limiting (to the north) and facilitating (to the south) the production of anti‐predatory traits. Feedbacks between temperature and predation thus causally interact to enable and drive, respectively, the observed geographic cline in energy‐intensive anti‐predatory shell traits.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Anatomy of a cline: dissecting anti‐predatory adaptations in a marine gastropod along the U.S. Atlantic coast

2017

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“…Although ‘size’ is a rather non‐specific quality, it can convey important information to the predator: larger individuals offer more edible tissue, but their shells are typically thicker and more difficult to break (Boulding ; Boulding & LaBarbera ). Larger shells are also probably older, and thus have had more time to accumulate repairs (Vermeij ; Dietl & Kosloski ).…”

Section: Methodsmentioning

confidence: 99%

Gastropod shell repair tracks predator abundance

2014

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Predator-prey interactions can shape biological communities and drive evolutionary change. The assessment of predation rates in modern and ancient ecosystems presents many challenges. We examined the utility of one common predation metric, shell repair frequency, as a proxy for crushing predation on marine gastropod populations. Our six localities near Bamfield, British Columbia, represented two contrasting predation regimes: three high-wave-energy (exposed) environments have low predation rates, while three low-wave-energy (protected) environments exhibit high predation rates. We measured the occurrence of repair scars for local populations of the gastropod Chlorostoma funebrale, and recorded multiple independent variables (shell measurements, water velocity, predatory crab abundance) at each locality. Fisher's exact test established that the repair frequencies observed in the protected localities were significantly greater than those of the exposed environments. Factors important in predicting the likelihood of an individual having a repair scar were examined using binomial logistic regression. A model containing the main effects of crab abundance, shell height, shell thickness and water velocity provided the best fit in predicting the presence of repair scars, with crab abundance having the largest contribution. The strong relationship between the presence of repair scars and predator abundance indicates that repair frequency is a valid tool for assessing predation intensity in gastropod populations.

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“…Although repair scars can result from non-predatory breakage, scars resulting from crab predation are distinctive, and can be identified by the following criteria (Leighton, 2001;Kowalewski, 2002;Dietl & Kosloski, 2013;Stafford et al, in press): scar shape is non-random (e.g. We noted whether each specimen bore at least one repair scar or was free of scars, and repair frequency was calculated as the total number of specimens bearing at least one repair, divided by the total number of specimens, a widely used and conservative calculation (Kowalewski, 2002;Leighton, 2002;Alexander & Dietl, 2003;Dietl & Kosloski, 2013). chelae); scar is not concentric with growth lines; and/or matching scars observed on both sides of the shell (suggests that predator enclosed and attempted to crush prey).…”

Section: A T E R I a L S A N D M E T H O D Smentioning

confidence: 99%

The utility of wax replicas as a measure of crab attack frequency in the rocky intertidal

2014

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Crabs are thought to play a vital role in structuring gastropod populations. Studies quantifying the frequencies with which crabs attack gastropods in natural settings are, however, scarce. Although a wide variety of techniques exist with which predator -prey interactions can be investigated (e.g. laboratory experiments, exclusion caging, tethering and population surveys), there is a need for methods that can provide large amounts of quantitative data, particularly documenting the frequency with which crabs attack gastropods. This study examines the utility of using wax replicas of gastropods to determine crab attack frequencies. Replicas of Chlorostoma funebralis, Nucella ostrina and Nucella lamellosa were bolted to mesh screens and deployed in the rocky intertidal. Crabs attacked wax replicas of gastropods, leaving characteristic marks in the wax. In most cases, the appendage used in the attack could be identified from the marks (i.e. chelae vs walking legs). The effectiveness of this technique was verified using surveys of repair scar frequencies of the gastropod populations; patterns in attack frequency, determined from the number of marked wax replicas, were consistent with those of repair frequency, in that both were greater at the wave protected, quiet water locality. This study confirms the value of wax replicas in investigations of crab predation to determine the frequency and type of attack, and illustrates the potential of this method for quantifying predation intensity. The development of techniques that quantify the magnitude and exact nature of the effects of crab predation on intertidal communities is pivotal, given the intensity of commercial fishing of some species of crabs.

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On the Measurement of Repair Frequency: How Important Is Data Standardization?

Cited by 26 publications

References 88 publications

Anatomy of a cline: dissecting anti‐predatory adaptations in a marine gastropod along the U.S. Atlantic coast

Anatomy of a cline: dissecting anti‐predatory adaptations in a marine gastropod along the U.S. Atlantic coast

Gastropod shell repair tracks predator abundance

The utility of wax replicas as a measure of crab attack frequency in the rocky intertidal

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