Sex in the Half-Shell: A Review of the Functions and Evolution of Courtship Behavior in Freshwater Turtles

Abstract

ABSTRACT. -Freshwater turtle courtship is an exciting and potentially phylogenetically important field of study. Scattered data exist from the past century of research, yet no recent summary is available. Courtship in freshwater turtles includes a number of common behaviors, which usually involve visual, tactile, olfactory, and auditory signals. These signals function in both species and sex recognition and in the seduction of potential mates. Specific behavioral sequences are required to facilitate successful copulation, and these behaviors presumably play a role in mate choice. We performed a series of meta-analyses to investigate the evolution of courtship behavior in freshwater turtles. Biting, an aggressive form of courtship behavior, is plesiomorphic, conserved only in the Chelydridae, Kinosternidae, subfamily Emydinae and South American species in the Pleurodira. Head movement and foreclaw display are apparently apomorphic and evolved independently in the Geoemydinae, Deirochelyinae, and Australian species of the Pleurodira. Display type (pre-or postmounting display) and sexual size dimorphism also show phylogenetic patterns. Therefore, the evolution of courtship behavior in freshwater turtles might accompany the evolution of sexual dimorphism, which is directly subject to natural selection.KEY WORDS. -Meta-analysis; sexual dimorphism; mating signal; natural selectionThe courtship behavior of freshwater turtles (CBFT) has been a topic of research interest for over a century. Anecdotal reports and more detailed observational studies have identified visual, tactile, chemical, and auditory stimuli. Early reviews by Carpenter and Ferguson (1977) and Harless (1979) noted a paucity of data. Over 30 yrs later, an impressive body of literature on CBFT has accumulated, but this literature is scattered, and no recent summary is available. Thus, although observations of courtship behavior exist for many species, our understanding of how CBFT operates remains limited because the functions of most signals used in courtship remain elusive. This is partly attributable to logistical difficulties involved in studying behavior in freshwater turtles and to the difficulty of determining the interpretation of signals by the receiver.Some more rigorous studies have produced quantifiable models of courtship behavior (e.g., Baker and Gillingham 1983;Liu et al. 2008), and these lend themselves to hypothesis testing. However, analyses and applications of ethograms based on stereotype patterns remain rare, and this precludes combining ethograms for comparative studies. Harless (1979) has identified necessary steps to move forward-hypothesis testing, identification of stimuli that elicit signaling, and identification of signal function-and much of this remains to be accomplished.Herein, we provide a brief history of the study of CBFT. We review behaviors and signals currently implicated in turtle courtship studies and discuss the methods and statistical analyses commonly used in these studies. This review unifies descriptions of beh...

Conservation genetics of the endangered Spotted Turtle (Clemmys guttata) illustrate the risks of “bottleneck tests”

“…Organisms with long life spans, overlapping generations, and promiscuous mating systems violate some of these assumptions (Frankham et al 2002) and may therefore experience the genetic effects of population fragmentation and decline differently. For example, most species of turtle have delayed maturity, long generation times (often >25 years), long life spans, and polygamous or promiscuous mating systems (Congdon et al 1993(Congdon et al , 1994Litzgus 2006;Davy et al 2011;Liu et al 2013).…”

Quantification of cranial and tomiodont dimorphism in Testudines using the Midland Painted Turtle, Chrysemys picta marginata

“…Reptiles have featured prominently in research on sexual dimorphism because of their high degree of variation in dimorphisms and life histories (Cox et al 2008). Both male-and femalebiased sexual size dimorphisms are well recorded in Testudines and have been related to male mating strategies, female fecundity, ecological selection, and phylogenetic patterns (Berry and Shine 1980;Shine 1989;Stephens and Wiens 2009;Ceballos et al 2013;Liu et al 2013). Turtles of the family Emydidae are a model group in the study of sexual dimorphism owing to their taxonomic and ecological diversity (Stephens and Wiens 2003), relatively thorough study (Lovich and Ennen 2013), and range of interesting sexual dimorphisms, including some of the most head, elongate snout, and angular rostrum (Boycott and Bourquin 2000;V.…”

Body coloration and mechanisms of colour production in Archelosauria: The case of deirocheline turtles

“…Therefore, it has been suggested that some of the colourful regions found particularly in males may potentially be involved in intersexual communication and mate choice [35,40]. In freshwater turtles courtship takes place underwater and males adopt characteristic positions relative to the female [41]. Deirocheline turtles are characterized by elaborated courtship behaviour including a complex forelimb display known as titillation [41].…”

“…In freshwater turtles courtship takes place underwater and males adopt characteristic positions relative to the female [41]. Deirocheline turtles are characterized by elaborated courtship behaviour including a complex forelimb display known as titillation [41]. Males in most species of deirocheline turtles perform the titillation display facing the female while swimming backwards in front of her, mostly near the surface; however, males of the genus Pseudemys titillate swimming above and parallel to the female, facing the same direction as her [41–46].…”

“…Deirocheline turtles are characterized by elaborated courtship behaviour including a complex forelimb display known as titillation [41]. Males in most species of deirocheline turtles perform the titillation display facing the female while swimming backwards in front of her, mostly near the surface; however, males of the genus Pseudemys titillate swimming above and parallel to the female, facing the same direction as her [41–46]. Thus, depending on the position adopted during courtship (face-to-face vs swim above) males of different species expose different body areas to females.…”