Predation affects body shape in the knife livebearer Alfaro cultratus (Cyprinodontiformes: Poeciliidae)
Data files
Nov 28, 2023 version files 133.59 KB
Abstract
Livebearing fishes are a common model for studying the effect of predation on prey biology. Numerous studies have found differences in life history, sexual selection, behavior, and morphology between populations of the same species that co-occur with predators and those that do not. Alfaro cultratus is a livebearing fish with populations in different predation environments, but unlike other livebearers, this species also has an extreme body shape that is laterally compressed. Given this unusual morphology, we asked if predation environment would still predict overall body shape, as has been documented in other species. We collected specimens from both predator and no-predator sites in Costa Rica and used a geometric morphometrics analysis to determine if body shape is affected by predation environment while controlling for size and river gradient. Body shape does indeed differ between predation environments; however, the observed differences contrast with the patterns found in other livebearer systems. Alfaro cultratus in predation environments had deeper and shorter bodies and deeper caudal peduncles than those found in environments without dominant fish predators.
README
Predation affects body shape in the knife livebearer Alfaro cultratus (Cyprinodontiformes: Poeciliidae)
Description of the data and file structure
TPS file: First line states the number of landmarks used, the next eleven lines show values for X and Y for each landmark. This is then followed by the corresponding image file name, the ID for the order of specimens and the scale value from the Generalized Procrustes Analysis. This is then repeated for each of the 459 specimens.
Text document: This file has one line for each of the 459 specimens. The first column shows at which locality was the specimen collected, the second shows a gradient value for that site, the third column indicates whether this is a low (0) or high predation (1) site, the fourth line is a unique museum ID for the BYU Life History Museum, the fifth line is the centroid size value calculated from the landmark positions and the final column is an order ID which matches the ID to each specimen's landmark data on the TPS file.
Methods
We used 459 female specimens of Alfaro cultratus for our analysis. We photographed all specimens on their left side and digitized 11 landmarks to characterize body shape (Figure 2), using the software tpsDig.
The predictor variable files list every specimen in the dataset with a column for its location ID, Gradient, High or Low Predation environment, Museum number ID, Centroid size and Order ID. This file is necessary for the multivariate linear mixed model.