Data from: Sexual shape dimorphism and selection pressure on males in fossil ostracodes
Sexual dimorphism is considered to have evolved by selection on both sexes. Ostracodes display sexual shape dimorphism in adult valves; however, no previous studies have addressed temporal changes in evolutionary time scales or examined the relationships between sexual shape dimorphism, selection pr...
| Main Authors: | , , , |
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| Format: | Article in Journal/Newspaper |
| Language: | unknown |
| Published: |
2017
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| Subjects: | |
| Online Access: | http://hdl.handle.net/10255/dryad.132759 http://hdl.handle.net/10255/dryad.136300 https://doi.org/10.5061/dryad.14j2m.2 |
| Summary: | Sexual dimorphism is considered to have evolved by selection on both sexes. Ostracodes display sexual shape dimorphism in adult valves; however, no previous studies have addressed temporal changes in evolutionary time scales or examined the relationships between sexual shape dimorphism, selection pressure, and juvenile shape. Temporal changes in sexually dimorphic traits result from responses of the traits to selection pressure. Using the Gaussian mixture model for the height/length ratio, a valve shape parameter, we identified sexual differences in the valve shape of Krithe dolichodeira from deep-sea sediments of the Paleocene age (62.6–57.6 Ma) and estimated the ratio of females in the fossil populations at eleven time intervals. As the female ratio in a population is altered by the mortality rate of adult males, it is reflective of the selection pressure on males. We attempted to correlate the height/length ratios between the sexes with the female ratios and considered that the valve shape did not link with the selection pressure on males. In time series data of the height/length ratio, both sexes indicate no real changes in the evolutionary time scales, although the population changed the sex ratios from female-skewed into male-skewed during the late Paleocene. The sexual shape dimorphism was not under sexual selection. The static allometry between the height/length ratio and length indicates that the sexual shape dimorphism was not functional for sexual display. The temporal change in female allometric slope indicates no real changes, suggesting that the evolution of the valve shape is constrained by static allometry. |
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