Skip to Main Content
Skip Nav Destination
GEOREF RECORD

Sexual shape dimorphism and selection pressure on males in fossil ostracodes

Tatsuhiko Yamaguchi, Rie Honda, Hiroki Matsui and Hiroshi Nishi
Sexual shape dimorphism and selection pressure on males in fossil ostracodes
Paleobiology (May 2017) 43 (3): 407-424

Abstract

Sexual dimorphism is thought to have evolved via selection on both sexes. Ostracodes display sexual shape dimorphism in adult valves; however, no previous studies have addressed temporal changes on evolutionary timescales or examined the relationships between sexual shape dimorphism and selection pressure and between sexual shape dimorphism and juvenile shape. Temporal changes in sexually dimorphic traits result from responses of these 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 s.l. from deep-sea sediments of the Paleocene (62.6-57.6 Ma) and estimated the proportion of females in the fossil populations at 11 time intervals. Because the proportion of females in a population is altered by the mortality rate of adult males, it is reflective of selection pressure on males. We attempted to correlate the height/length ratios between the sexes with the proportion of females, taking into consideration that the valve shape was not linked with the selection pressure on males. In time-series data of the height/length ratio, both sexes indicate no significant changes on evolutionary timescales, even though the sex ratio of the population changed from female skewed to male skewed during the late Paleocene. The sexual shape dimorphism was not driven by sexual selection. The static allometry between the height/length ratio and length indicates that the sexual shape dimorphism did not function for sexual display. The absence of change over time in the female allometric slope suggests that the evolution of valve shape was constrained by stasis.


ISSN: 0094-8373
EISSN: 1938-5331
Coden: PALBBM
Serial Title: Paleobiology
Serial Volume: 43
Serial Issue: 3
Title: Sexual shape dimorphism and selection pressure on males in fossil ostracodes
Affiliation: Kochi University, Center for Advanced Marine Core Research, Nankoku, Japan
Pages: 407-424
Published: 201705
Text Language: English
Publisher: Paleontological Society, Lawrence, KS, United States
References: 71
Accession Number: 2017-077590
Categories: Invertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables
N41°25'30" - N41°25'30", W49°48'49" - W49°48'47"
Secondary Affiliation: Tohoku University, JPN, Japan
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, The Paleontological Society. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201741
Program Name: IODPIntegrated Ocean Drilling Program
Close Modal

or Create an Account

Close Modal
Close Modal