Sexual Selection and Sexual Dimorphism in Foreclaw Length of Pseudemys
Sexual selection is thought to be responsible for the evolution of ornamental traits that may signal quality to potential mates. Male turtles in the emydid subfamily Deirochelyinae have markedly elongated foreclaws which they use during courtship. We explore whether claw length indicates male quality as measured by body condition and if the degree of sexual dimorphism in claw length and claw growth trajectories vary among three species of Pseudemys (Pseudemys concinna, Pseudemys floridana, and Pseudemys nelsoni) in the Rainbow Run, Marion County, Florida. Claw length was not correlated with body condition (mass relative to size) in these species. Thus, claw length likely does not serve as an honest indicator of male body condition. Claw length is sexually dimorphic in all three species, with P. concinna showing the highest degree of sexual dimorphism. Claw length increases with plastron length in all three species, but proportional claw length decreases with plastron length in P. floridana and P. nelsoni and increases in male and juvenile P. concinna. Variation in the degree of claw dimorphism and claw growth patterns in this study suggests the possibility of unrecognized diversity and complexity in courtship behavior in Pseudemys.
Claw length as a function of body condition in Pseudemys concinna, Pseudemys floridana, and Pseudemys nelsoni from Rainbow Run, Marion Co., Florida by category: adult males—solid triangles (long dash line), adult females—solid circles (solid line), sub-adult females—hollow circles (short dash line), juveniles—hollow squares (dot dash line). There is no significant relationship between claw length and body condition except in adult female P. concinna (Table 1).
Proportional claw length is plotted as a function of body condition in Pseudemys concinna, Pseudemys floridana, and Pseudemys nelsoni from Rainbow Run, Marion Co., Florida by category: adult males—solid triangles (long dash line), adult females—solid circles (solid line), sub-adult females—hollow circles (short dash line), juveniles—hollow squares (dot dash line). There is no significant relationship between claw length and body condition except in adult female P. concinna and P. floridana (Table 2).
Claw length as a function of plastron length in Pseudemys concinna, Pseudemys floridana, and Pseudemys nelsoni from Rainbow Run, Marion Co., Florida by category: adult males—solid triangles (long dash line), adult females—solid circles (solid line), sub-adult females—hollow circles (short dash line), juveniles—hollow squares (dot dash line). Claw length is positively related to plastron length in most life history categories of each species, except if there is no significant relationship (Table 4).
Proportional claw length as a function of plastron length in Pseudemys concinna, Pseudemys floridana, and Pseudemys nelsoni from Rainbow Run, Marion Co., Florida by category: adult males—solid triangles (long dash line), adult females—solid circles (solid line), sub-adult females—hollow circles (short dash line), juveniles—hollow squares (dot dash line). Proportional claw length is negatively related or has no significant relationship to plastron length in all life history categories of each species, except in adult male and juvenile P. concinna, where it is positively related (Table 5).
Contributor Notes
Associate Editor: D. S. Siegel
Present address: Odum School of Ecology, University of Georgia, Athens, Georgia 30602; Email: k.ebey@uga.edu. Send correspondence to this address.