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Abstract Studies of paleocommunities and trophic webs assume that multispecies assemblages consist of species that coexisted in the same habitat over the duration of time averaging. However, even species with similar durability can differ in age within a single fossil assemblage. Here, we tested whether skeletal remains of different phyla and trophic guilds, the most abundant infaunal bivalve shells and nektobenthic fish otoliths, differed in radiocarbon age in surficial sediments along a depth gradient from 10 to 40 m on the warm-temperate Israeli shelf, and we modeled their dynamics of taphonomic loss. We found that, in spite of the higher potential of fishes for out-of-habitat transport after death, differences in age structure within depths were smaller by almost an order of magnitude than differences between depths. Shell and otolith assemblages underwent depth-specific burial pathways independent of taxon identity, generating death assemblages with comparable time averaging, and supporting the assumption of temporal and spatial co-occurrence of mollusks and fishes.
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Ecophenotypy, temporal and spatial fidelity, functional morphology, and physiological trade-offs among intertidal bivalves
Abstract Ecophenotypic variation in populations is driven by differences in environmental variables. In marine environments, ecophenotypic variation may be caused by differences in hydrodynamic conditions, substrate type, water depth, temperature, salinity, oxygen concentration, and habitat heterogeneity, among others. Instances of ecophenotypic variation in modern and fossil settings are common, but little is known about the influences of time averaging and spatial averaging on their preservation. Here we examine the shell morphology of two adjacent populations, both live collected and death assemblages, of the infaunal, suspension-feeding, intertidal bivalve Leukoma staminea from the well-studied Argyle Creek and Argyle Lagoon locations on San Juan Island, Washington. Individuals in the low-energy lagoon are free to burrow in the fine-grained substrate, while clams in the high-energy creek are precluded from burrowing in the rocky channel. Our results demonstrate variation in size and shape between the adjacent habitats. Lagoon clams are larger, more disk-shaped, and have relatively larger siphons than their creek counterparts, which are smaller, more spherical in shape, and have a relatively shallower pallial sinus. This ecophenotypy is preserved among death assemblages, although with generally greater variation due to time averaging and shell transport. Our interpretation is that ecophenotypic variation, in this case, is induced by differing hydrodynamic regimes and substrate types, cumulatively resulting in physiological trade-offs diverting resources from feeding and respiration to stability and shell strength, all of which have the potential to be preserved in the fossil record.
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- Award ID(s):
- 1650745
- PAR ID:
- 10093057
- Date Published:
- Journal Name:
- Paleobiology
- Volume:
- 44
- Issue:
- 3
- ISSN:
- 0094-8373
- Page Range / eLocation ID:
- 530 to 545
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1017/pab.2018.14
