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Abstract Fish scales are bony plates embedded in the skin that vary extensively in shape across taxa. Despite a plethora of hypotheses regarding form–function relationships in scales, we know little about the ecological selective factors that shape their diversity. Here we examine evolutionary patterns of scale morphology using novel three-dimensional topography from the surfaces of 59 species of damselfishes, a prominent radiation of coral reef fishes. We find evidence that scale morphology changes with different flow environments, such that species that spend more time in open-water habitats have smoother scales. We also show that other aspects of ecology lead to highly derived scales. For example, anemonefishes show an evolutionary transition to smaller scales and smaller ctenii (scale spines). Moreover, changes in body shape, which may reflect ecological differentiation, are related to scale shape but not surface properties. We also demonstrate weak evolutionary integration among multiple aspects of scale morphology; however, scale size and shape are related, and scale morphology is correlated between different body regions. Finally, we also identify a relationship between aspects of lateral line pore morphology, such that the number of lateral line pores per scale and the size of those pores are inversely related. Overall, our study provides insights into the multidimensionality of scale evolution and improves our understanding of some of the factors that can give rise to the diversity of scales seen across fishes.
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Interactions among multiple selective pressures on the form–function relationship in insular stream fishes
Abstract Relationships between body shape and escape performance are well established for many species. However, organisms can face multiple selection pressures that might impose competing demands. Many fishes use fast starts for escaping predator attacks, whereas some species of gobiid fishes have evolved the ability to climb waterfalls out of predator-dense habitats. The ancestral ‘powerburst’ climbing mechanism uses lateral body undulations to move up waterfalls, whereas a derived ‘inching’ mechanism uses rectilinear locomotion. We examined whether fast-start performance is impacted by selection imposed from the new functional demands of climbing. We predicted that non-climbing species would show morphology and fast-start performance that facilitate predator evasion, because these fish live consistently with predators and are not constrained by the demands of climbing. We also predicted that, by using lateral undulations, powerburst climbers would show escape performance superior to that of inchers. We compared fast starts and body shape across six goby species. As predicted, non-climbing fish exhibited distinct morphology and responded more frequently to an attack stimulus than climbing species. Contrary to our predictions, we found no differences in escape performance among climbing styles. These results indicate that selection for a competing pressure need not limit the ability of prey to escape predator attacks.
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- Award ID(s):
- 1942178
- PAR ID:
- 10496670
- Publisher / Repository:
- Biological Journal of the Linnean Society
- Date Published:
- Journal Name:
- Biological Journal of the Linnean Society
- Volume:
- 134
- Issue:
- 3
- ISSN:
- 0024-4066
- Page Range / eLocation ID:
- 557 to 567
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/biolinnean/blab098
