DO LATITUDE, ELEVATION, TEMPERATURE, AND PRECIPITATION INFLUENCE BODY AND CLUTCH SIZES OF FEMALE COMMON FIVE-LINED SKINKS, PLESTIODON FASCIATUS (LINNAEUS, 1758)?

Common Five-lined Skinks (Plestiodon fasciatus) have an extensive distribution that includes much of eastern North America. We examined 490 female specimens (274 with putative clutch sizes) from throughout the range to see if latitude, elevation, mean annual temperature, and/or mean annual precipitation affected body or clutch sizes. We predicted that larger females would produce larger clutches, latitude and elevation would negatively affect both body and clutch sizes, and that temperature and precipitation would exert a positive effect. Our results did not consistently support those predictions. Body size was positively associated with latitude, negatively associated with temperature, and not associated with elevation or precipitation. Clutch size was not related to female body size, but in most instances was positively associated with temperature and precipitation but negatively associated with elevation and latitude. Effectively K-selected in the North and r-selected in the South, body and clutch sizes in this species appear to be responding to different select.

Male body size varies with latitude in a temperate lizard

To examine the evolution of sexual size dimorphism (SSD), interspecific studies are often performed to generate hypotheses for the origin and maintenance of SSD. Although these methods are invaluable to our understanding of the evolution of SSD, they often quantify SSD for a species based on few populations. We found a significant sex-specific latitudinal cline in Plestiodon fasciatus (L., 1758) (= Eumeces fasciatus (L., 1758)), a species that was previously considered to be monomorphic for body size. Male body size significantly increased with increasing latitude, whereas female body size was relatively constant. Our findings argue for the importance of increased understanding and appreciation of intraspecific variation in SSD. We suggest that a more integrated approach to SSD be employed, where both intraspecific and interspecific variation is considered. We provide a foundation for posing hypotheses of the causes and consequences of SSD in P. fasciatus and perhaps other members of the species group.

Courtship and mating behaviours of two syntopic species of skink (Plestiodon anthracinus and Plestiodon fasciatus)

Courtship and mating behaviours are widely conserved throughout the scincid lizard genus Plestiodon, and ethological isolation between closely related species depends heavily on differentiating chemical cues. The purpose of this study was to determine whether or not subtle, as yet undetected differences are present in the mating behaviours of two syntopic, distantly related skinks, P. anthracinus and P. fasciatus. Observed courtship and mating behaviours were similar between the two species and to those reported for other species within this genus. However, survival analysis determined significant interspecific differences in the duration of pre-coital behaviours. Investigation of such subtle differences between species more closely related than these two may generate further insights into the evolution of ethological isolating mechanisms in lizards.