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Drilling predation increased in response to changing environments in the Caribbean Neogene

Published online by Cambridge University Press:  03 May 2016

Jill S. Leonard-Pingel
Affiliation:
Geoscience Research Division, Scripps Institution of Oceanography, La Jolla, CA 92093, U.S.A. E-mail: leonard-pingelj@wlu.edu.
Jeremy B. C. Jackson
Affiliation:
Geoscience Research Division, Scripps Institution of Oceanography, La Jolla, CA 92093, U.S.A. Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20013, U.S.A. Smithsonian Tropical Research Institute, Post Office Box 0843-03093, Balboa, Panama

Abstract

Changes in the physical environment are major drivers of evolutionary change, either through direct effects on the distribution and abundance of species or more subtle shifts in the outcome of biological interactions. To investigate this phenomenon, we built a fossil data set of drilling gastropod predation on bivalve prey for the last 11 Myr to determine how the regional collapse in Caribbean upwelling and planktonic productivity affected predator–prey interactions. Contrary to theoretical expectations, predation increased nearly twofold after productivity declined, while the ratio of drilling predators to prey remained unchanged. This increase reflects a gradual, several-fold increase in the extent of shallow-water coral reefs and seagrass meadows in response to the drop in productivity that extended over several million years. Drilling predation is uniformly higher in biogenic habitats than in soft sediments. Thus, changes in predation intensity were driven by a shift in dominant habitats rather than a direct effect of decreased productivity. Most previous analyses of predation through time have not accounted for variations in environmental conditions, raising questions about the patterns observed. More fundamentally, however, the consequences of large-scale environmental perturbations may not be instantaneous, especially when changes in habitat and other aspects of local environmental conditions cause cascading series of effects.

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Copyright
Copyright © 2016 The Paleontological Society. All rights reserved 
Figure 0

Figure 1 Map of Panama and eastern Costa Rica, with insets showing the four basins from which collections were taken; Limon Basin, Costa Rica; Bocas del Toro Basin, Panama; Panama Canal Zone, Panama; and Darien Basin, Panama. Numbers correspond to faunules listed in Table 1.

Figure 1

Table 1 Age, geologic formation, and locality information for each faunule. Numbers correspond to locations mapped in Figure 1.

Figure 2

Table 2 Age, habitat designation, environmental data, and abundance data for each faunule (O'Dea et al. 2007; Leonard-Pingel et al. 2012). Mixed habitat refers to a combination of seagrass and coral dominated environments.

Figure 3

Table 3 Bivalve genera pooled across all samples with drilling frequency and preferred habitat. Preferred habitat is inferred from a reivew of the literature with key references cited.

Figure 4

Figure 2 Percentage of bivalves drilled for each faunule. The percentage of drilled bivalves significantly increased through time (ρ=0.33, p<0.05), but there is no correlation between percentage of drilled bivalves and time when faunules are analyzed by habitat (soft-sediment habitats (squares): ρ=0.04, p=0.44; biogenic habitats (circles): ρ=−0.19, p=0.26). This contradicts the hypothesis that predation is positively correlated with primary productivity.

Figure 5

Figure 3 Differences in predation rates between habitats and bivalve functional groups. W-values are for Wilcoxon rank-sum tests; G-values are for G-tests. A, Biogenic faunules (n=14) have significantly higher drilling frequencies than do soft-sediment faunules (n=14). B, Genera characteristic of biogenic habitats (n=36) display higher drilling frequencies than do genera characteristic of soft-sediment habitats (n=54). C, The percentage of epifaunal bivalves (n=13592 valves) drilled is more than twice that of infaunal bivalves (n=44011 valves) in all 28 faunules combined. D, The percentage of chemosymbiotic bivalves (n=4646 valves) drilled is more than triple that of siphonate bivalves (n=31050 valves) in all 28 faunules combined.

Figure 6

Figure 4 Box plots of eight common bivalve genera that occur in both soft-sediment and biogenic faunules. W-values are for Wilcoxon rank-sum tests; n denotes the number of faunules. The percentage of valves drilled (drilling frequency) generally remains constant within a genus, with the single exception of Macrocallista.

Figure 7

Figure 5 Faunules binned according to age; n is the number of faunules for each bin. A, The relative abundance of gastropod predators and bivalve prey remained constant over the past 11 Myr (χ2=1.97, p=0.37). B, The ratio of muricid gastropods to naticid gastropods increased significantly through time.

Figure 8

Figure 6 Naticid gastropods as a proportion of total drilling gastropods varies significantly among different habitat types (χ2=10.99, p<0.01) and is significantly lower in seagrass and reef habitats than soft-sediment habitats. Faunules binned according to habitat type; n is the number of faunules for each bin.