A new species of Chrysemys (Emydidae: Deirochelyinae) from the latest Miocene-Early Pliocene of Tennessee, USA and its implications for the evolution of painted turtles

Chrysemys, commonly known as painted turtles, have the largest native biogeographic range of all North American turtles. The presence of a new species, Chrysemys corniculata sp. nov., in the Late Hemphillian-Early Blancan North American Land Mammal Age (latest Miocene-Early Pliocene) of Tennessee provides further data on the evolution of Chrysemys, deirochelyines and emydids. The new fossil species lies basally in Deirochelyinae and suggests that either Chrysemys represents a basal deirochelyine morphology and is one of the oldest genera in the family, or that similar basal morphologies have evolved multiple times throughout deirochelyine evolution. Its occurrence at the same time as Chrysemys picta, during the Hemphillian-Early Blancan, a time of high biodiversity in emydid turtles, suggests either multiple species of Chrysemys during the Late Hemphillian-Early Blancan (at least one in the mid-west and one farther east), or multiple lineages with basal morphologies during this time. Early fossil deirochelyines occur after the greenhouse conditions of the Eocene and the Mid-Miocene Climatic Optimum. Vicariance led to deirochelyines becoming more speciose, including the occurrence of C. corniculata, after the Mid-Miocene Climatic Optimum, potentially suggesting cooler temperatures aided in the evolution of the subfamily and their speciation during the Hemphillian and into the Early Blancan.

A New Perspective on Female-to-Male Communication in Salamander Courtship

Courtship behavior in salamanders is often complex and involves well-documented communication from males to females in multiple sensory modalities. Historically, behaviors exhibited during the major stages of courtship have been predominately framed as a male acting and signaling to "persuade" a passive female to participate in courtship and remain with him until sperm release is completed. In this review, we use courtship descriptions for lungless salamanders (Plethodontidae) as a case study to illustrate this historical bias of a male-centered perspective. We then re-examine the literature and summarize the many ways females are active participants during plethodontid courtships. We also relate female behaviors to the types of female-to-male communication that may occur. For example, females have been documented to approach a male and initiate courtship, participate in mutual head rubbing, and step astride the male's tail to begin the tail-straddling walk (a key courtship behavior observed in all plethodontids). Additionally, females have glands that may produce chemical signals that males respond to during courtship. We conclude that communication during courtship is more accurately described as a two-way interaction where each partner's behavior is coordinated with the other's via multi-modal signaling. Shifting the lens through which we view courtship and behavior provides insight into which female behaviors and anatomical features are most likely to be used for communication with males.

Evolutionary history of mental glands in turtles reveals a single origin in an aquatic ancestor and recurrent losses independent of macrohabitat

Despite the relevance of chemical communication in vertebrates, comparative examinations of macroevolutionary trends in chemical signaling systems are scarce. Many turtle and tortoise species are reliant on chemical signals to communicate in aquatic and terrestrial macrohabitats, and many of these species possess specialized integumentary organs, termed mental glands (MGs), involved in the production of chemosignals. We inferred the evolutionary history of MGs and tested the impact of macrohabitat on their evolution. Inference of ancestral states along a time-calibrated phylogeny revealed a single origin in the ancestor of the subclade Testudinoidea. Thus, MGs represent homologous structures in all descending lineages. We also inferred multiple independent losses of MGs in both terrestrial and aquatic clades. Although MGs first appeared in an aquatic turtle (the testudinoid ancestor), macrohabitat seems to have had little effect on MG presence or absence in descendants. Instead, we find clade-specific evolutionary trends, with some clades showing increased gland size and morphological complexity, whereas others exhibiting reduction or MG loss. In sister clades inhabiting similar ecological niches, contrasting patterns (loss vs. maintenance) may occur. We conclude that the multiple losses of MGs in turtle clades have not been influenced by macrohabitat and that other factors have affected MG evolution.

Demographics of injuries indicate sexual coercion in a population of Painted Turtles (Chrysemyspicta)

Sexually coercive reproductive tactics are widespread among animals. Males may employ specialized structures to harass, intimidate, or physically harm females to force copulation, and injuries to the head and neck are reported in taxa with sexually coercive mating systems. The mating tactics of Painted Turtles (Chrysemys picta (Schneider, 1783)) are typically described as involving male courtship and female choice. In contrast, female Painted Turtles in our study population display injuries on the head and neck indicative of bite wounds inflicted by sexually dimorphic tomiodonts and weaponized shell morphology of males during reproductive interactions. Using a 24-year data set, we demonstrate population-level trends in soft tissue wounds inflicted by conspecifics. Adult females experienced more wounding than adult males or juveniles, and larger females had a greater probability of wounding than smaller females. Wounding was concentrated on the dorsal head and neck of females, consistent with expectation of sexual coercion. Furthermore, elevated rates of fresh wounding occurred during late summer, concurrent with the breeding period. By assessing wound demographics, we provide indirect evidence that the tomiodonts and shell of male Painted Turtles inflict injury and function as sexual weapons. These findings shed new light on our understanding of mating system complexity in an often-overlooked and difficult-to-observe taxonomic group.

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

Animal body coloration is a complex trait resulting from the interplay of multiple mechanisms. While many studies address the functions of animal coloration, the mechanisms of colour production still remain unknown in most taxa. Here we compare reflectance spectra, cellular, ultra- and nano-structure of colour-producing elements, and pigment types in two freshwater turtles with contrasting courtship behaviour, Trachemys scripta and Pseudemys concinna. The two species differ in the distribution of pigment cell-types and in pigment diversity. We found xanthophores, melanocytes, abundant iridophores and dermal collagen fibres in stripes of both species. The yellow chin and forelimb stripes of both P. concinna and T. scripta contain xanthophores and iridophores, but the post-orbital regions of the two species differ in cell-type distribution. The yellow post-orbital region of P. concinna contains both xanthophores and iridophores, while T. scripta has only xanthophores in the yellow-red postorbital/zygomatic regions. Moreover, in both species, the xanthophores colouring the yellow-red skin contain carotenoids, pterins and riboflavin, but T. scripta has a higher diversity of pigments than P. concinna. Trachemys s. elegans is sexually dichromatic. Differences in the distribution of pigment cell types across body regions in the two species may be related to visual signalling but do not match predictions based on courtship position. Our results demonstrate that archelosaurs share some colour production mechanisms with amphibians and lepidosaurs (i.e. vertical layering/stacking of different pigment cell types and interplay of carotenoids and pterins), but also employ novel mechanisms (i.e. nano-organization of dermal collagen) shared with mammals.

Paternity Analysis of Wood Turtles (Glyptemys insculpta) Reveals Complex Mating Patterns

Mating system characteristics are of great importance as they may influence male and female reproductive success and reproductive isolation. The wood turtle (Glyptemys insculpta) is a terrestrial freshwater species listed as endangered by the International Union for Conservation of Nature. Considering its conservation status and the paucity of information currently available on parentage relationship for the species, we performed a microsatellite analysis to study the mating system of wood turtles in the Shawinigan River (Québec). We sampled 38 clutches over 2 years (14 in 2006 and 24 in 2007), for a total of 248 offspring genotyped with 7 microsatellite loci. The reconstructed genotypes of the fathers revealed that reproductive success in the sampled clutches varied greatly between males and are positively correlated with the number of mates and clutches sired. Frequency of multiple paternity was estimated at 37% through a consensus of 3 different estimation methods. Positive correlation was observed between the genetic diversity of clutches and the number of fathers. Repeat paternity, however, was observed in 88% of the clutches by the same female in successive years, which suggests either a frequent use of sperm storage, or remating with the same partner in successive years.

Patterns of intraspecific aggression inferred from injuries in an aquatic turtle with male-biased size dimorphism

Patterns of sexual size dimorphism (SSD) in turtles are correlated with ecological mode, and it has been hypothesized that mating systems are also shaped by ecological mode. Male combat and coercive mating are competing explanations for male-biased SSD, but are difficult to assess empirically in aquatic species with cryptic behaviour. We quantified SSD and compiled observations of putative combat wounds collected from over 500 captures of Snapping Turtles (Chelydra serpentina (L., 1758)) in Algonquin Provincial Park, Ontario, to test hypotheses of mate competition and coercion. We found that both sex and body size were important predictors of risk of wounding, consistent with the hypothesis that male–male sexual competition is the primary driver of intraspecific aggression. Low wounding rates among females suggests that resource competition and coercive mating are not important causes of injuries. The risk of wounding increased monotonically with body size in adult males but not in adult females, and small males were less likely to be injured, suggesting that they employ a risk-averse strategy by avoiding direct competition for mates. There was no evidence of asymptotic or decreasing wounding probability in the largest males, which is consistent with the hypothesis that large males compete most intensively to monopolize mates.

Reproductive aspects of the Chocoan River turtle (Rhinoclemmys nasuta, Geoemydidae) along the Colombian Pacific coast

We collected data on several aspects of the reproductive biology of the Chocoan River Turtle (Rhinoclemmys nasuta) as part of a long-term demographic study (2005-2015), along the Pacific coast of the department of Valle del Cauca in Colombia. We palpated 659 females and found 77 gravid, with two peaks in the proportion of females gravid, one between May and June, and another from October to December; there was a significant correlation between the monthly proportion gravid and the monthly amount of precipitation (Spearman rank correlation , ). We obtained 13 eggs (mean length = 63.8 mm, mean width = 35.4 mm, mean weight = 45.8 g). Using egg volume as a general indicator of size, there was no significant relationship with female size. To induce oviposition, oxytocin, prostaglandin, or a combination of the two was injected into 37 gravid females with a success rate of 48.6%. We determined the duration of incubation for two individuals as 133 and 135 days. With this information, we fill some gaps in the knowledge of reproductive ecology of this species; however, the sample size is very low and primarily comes from a single insular population and therefore it is important to continue studies on aspects of reproductive ecology such as those evaluated in this study and other topics like sex determination.

Sexual coercion and courtship by male western gorillas

Sexual coercion and courtship are possible explanations for why male primates may direct agonistic behavior towards females. If so, then in species where females exhibit mate choice by transferring between males: (a) females who are not lactating (potential migrants) should receive more agonistic behavior than other females, (b) males should exhibit more agonistic behavior towards females during intergroup encounters than when no rival males are nearby, and (c) males should show more herding behavior when their group contains potential migrant females. We tested those hypotheses in a population of approximately 150 western gorillas at Mbeli Bai, northern Congo. We also tested whether difference in male phenotypic traits influenced their rates of agonistic behavior towards females. Of the 332 observed cases of male agonistic behavior towards females, 29% represented feeding competition, 7 % involved interventions in conflicts between females, and the remaining 64 % were considered potential evidence of sexual coercion and/or courtship. After excluding the cases of feeding competition and intervention, a multivariate analysis indicated that potential migrant females received agonistic behavior at a statistically significantly higher rate than other adult females. Females also received agonistic behavior at a significantly higher rate during intergroup encounters than at other times. Herding occurred during 22% of the 292 dyadic interunit encounters, and was significantly more likely to occur when the group contained a potential migrant female, but was not influenced by the number of adult females or the type of group encountered. Males with shorter body lengths had significantly higher rates of aggression, but phenotypic traits were not significantly correlated with herding. Collectively, our results are consistent with sexual coercion and/or courtship as an explanation for male-to-female agonistic behavior, but we are unable to distinguish between those two male mating strategies. Both types of behavior are likely due to a combination of perceived risks of female transfer and opportunity to advertise protector ability.

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

Studies of population genetics in turtles have suggested that turtles do not experience genetic impacts of bottlenecks as strongly as expected. However, recent studies cast doubt on two commonly used tests implemented in the program BOTTLENECK, suggesting that these findings should be re-evaluated. The Spotted Turtle (Clemmys guttata (Schneider, 1792)) is endangered both globally and within Canada, but genetic data required to develop effective recovery strategies are unavailable. Here, we conducted the first study of population genetic structure in C. guttata. We then used multiple small populations of C. guttata as replicates to test whether the commonly used program BOTTLENECK could detect the genetic signature of bottlenecks in our study populations, which are all thought to have experienced significant declines in the past 2–3 generations (75 years). Turtles (n = 256) were genotyped at 11 microsatellite loci. A suite of Bayesian population genetics analyses and a principal coordinates analysis identified a minimum of 6 distinct genetic populations and a maximum of 10 differentiated subpopulations across the sampled Canadian range of C. guttata, which corresponded to demographically independent units. BOTTLENECK failed to detect population declines. A literature review found that bottleneck tests in 17 of 18 previous genetic studies of tortoises and freshwater turtles were based on suboptimal sampling, potentially confounding their results. High retention of genetic diversity (allelic richness and heterozygosity) in isolated populations of C. guttata and other turtle species is encouraging for species recovery, but conclusions about the prevalence of genetic bottlenecks in such populations should be re-examined.