Although visually transmitted social signals are well documented in many diurnal iguanians, including collared lizards, secretory femoral glands also suggest a role of chemical signals in ...intraspecific communication. We conducted laboratory trials to test the extent to which male and female collared lizards responded by tongue‐flicking femoral gland secretions, neutral (water), and odoriferous (cologne) control substances, males distinguished self‐secretions from those produced by unfamiliar rival males, and females distinguish secretions from unfamiliar vs. familiar males. Both males and females spent similar amounts of time in four arena quadrants each with a Petri dish treated with one of the four test compounds. Males gave more tongue flicks/trial to secretions produced by unfamiliar rivals and cologne than they tongue‐flicked their own secretions and water. By contrast, the number of tongue flicks by females on control substances and familiar and unfamiliar males was similar. Results support the hypothesis that femoral gland secretions function in intrasexual signaling among male collared lizards, perhaps allowing them to distinguish unfamiliar rivals. Females tongue‐flicked secretions from familiar and unfamiliar males with similar frequency that was high relative to that of males, suggesting a possible role of secretions in assessment of males. Ours is the first evidence of a signaling role of femoral gland secretions in collared lizards and adds to a growing body of evidence that chemical signaling has evolved in diurnal lizards that also have highly developed visual‐based signaling.
Territory defence is widely assumed to be adaptive because it enhances reproductive success. However, empirical evidence for such a benefit is scarce or nonexistent for many types of territorial ...organisms. The roles of intraspecific aggression versus interactions with females in successful breeding by territorial males are also still poorly understood in lower tetrapods, including lizards. We address both of these important issues using 10 years of data on genetic parentage combined with field behavioural studies in collared lizards, Crotaphytus collaris. As predicted, territorial males (T-males) had more mates, sired markedly more total offspring and sired more surviving offspring with more females than did nonterritorial (NT) males. Territorial males in structurally simpler habitats sired a higher proportion of each female's offspring than their counterparts in complex habitats, indicating that the ability of T-males to accrue mating benefits is highest where topography maximizes contact with multiple females. All measures of T-male reproductive success increased with travel rate but decreased with the time spent courting individual females, suggesting a fitness trade-off between these behaviours. We found no evidence that aggressive behaviour was linked to any component of male fitness. Hence, activities of territory owners appear to be shaped by sexual selection to enhance mating opportunities rather than to aggressively dominate same-sex rivals. Our study illustrates the value of long-term research documenting behaviour and fitness of free-ranging individuals over multiple reproductive cycles in evaluating fundamental questions about the adaptive significance of social tactics.
•Territorial male collared lizards had higher fitness than nonterritorial males.•Territorial tactics increased mating more effectively in simpler habitats.•Fitness of territory owners increased with travel but not with aggressive behaviour.•Limiting courtship per female promoted travel to interact with additional mates.•Male behaviour is selected to enhance interactions with multiple female mates.
We have recently shown that leucine culture upregulates ATP synthase beta-subunit (ATPSbeta) and increases ATP level, cytosolic Ca(2+), and glucose-induced insulin secretion in rat islets. The aim is ...to test whether glucokinase expression is also affected in rat islets and its role in glucose sensitization during leucine culture. Leucine culture increased glucose-induced NAD(P)H level at 1 and 2 days but not at 1 week. The half-maximal effective concentration of the glucose response curve for NAD(P)H was left-shifted from 5-7 to 2-3 mmol/l. The effect was dose dependent and rapamycin insensitive. Leucine culture did not affect glyceraldehyde effects on NAD(P)H. Leucine pretreatment for 30 min had no effects on NAD(P)H levels. Leucine culture for 2 days also increased glucose-induced cytosolic Ca(2+) elevation, ATP level, and insulin secretion. Leucine increase of glucokinase mRNA levels occurred as early as day 1 and lasted through 1 week. That of ATPSbeta did not occur until day 2 and lasted through 1 week. Leucine effects on both mRNAs were dose dependent. The upregulation of both genes was confirmed by Western blotting. Leucine culture also increased glucose-induced insulin secretion, ATP level, glucokinase, and ATPSbeta levels of type 2 diabetic human islets. In conclusion, leucine culture upregulates glucokinase, which increases NAD(P)H level, and ATPSbeta, which increases oxidation of NADH and production of ATP. The combined upregulation of both genes increases glucose-induced cytosolic Ca(2+) and insulin secretion.
Females in diverse vertebrate and invertebrate clades often mate and produce offspring with multiple male partners. Deciphering the evolutionary mechanisms underlying the origins of females producing ...offspring with multiple sires remains a challenging problem, because a single male can usually provide enough sperm to fertilize all eggs produced by individual females. We tested the hypothesis that having multiple males sire individual clutches is adaptive for female eastern collared lizards, Crotaphytus collaris, by examining both the fitness costs and benefits for females of producing offspring with one versus multiple male partners. We found no support for the hypothesis that females produce offspring with multiple sires to acquire access to higher-quality food resources or refuges. However, hatching success of clutches increased with the number of males that inseminated eggs, which suggests that accepting sperm from multiple males may improve offspring hatching success through one or more mechanisms. Our results also indicate that females producing offspring with multiple male partners gained genetic advantages. Although offspring mortality from clutches sired by one versus multiple males was similar, females producing clutches sired by multiple males had more total offspring that survived to maturity, resulting in a net fitness advantage for these females. Our results suggest that producing offspring with multiple males is adaptive for female collared lizards because it promotes acquisition of several fitness benefits.
•The evolutionary basis for offspring production with multiple males is enigmatic.•We tested if multi-sire offspring production is adaptive in female collared lizards.•Multi-sire females had higher rates of egg hatching success.•Having multiple sires enhanced female reproductive output and offspring survival.•Females gained fitness benefits by producing offspring with multiple males.
Sexual selection theory often predicts that socially dominant males should sire more offspring than males adopting subordinate social tactics. However, it is often difficult to determine the extent ...to which this expected distribution of male reproductive success is influenced by intra- and intersexual selection. Using a combination of field behavioral studies and molecular genetic techniques, I first tested the extent to which observations of social and spatial behavior predicted the distribution of reproductive success among female collared lizards and males displaying alternative social tactics (territorial and non-territorial) during a single reproductive season. I also examined the strength of sexual selection acting on male morphological and behavioral traits. Contrary to expectations, male social status did not accurately predict patterns of reproductive success: non-territorial males obtained reproductive success equal to that of territorial males and females were highly promiscuous, mating with a similar number of territorial and non-territorial males, both within and among successive clutches. None of the traits that I examined were significant targets of sexual selection among non-territorial males. However, male snout-vent-length was under positive directional selection among territorial males. To test the generality of my earlier findings, I expanded my analyses to encompass three seasons to examine how the number of female mates and offspring sired among males varied with marked natural variation in the intensity of intra- and intersexual selection within and among seasons, and the influence of behavioral traits on male fitness. I also examined how the degree of female promiscuity varied with changes in the intensity of sexual selection and the influence of female promiscuity on offspring survivorship. Unexpectedly, results from all seasons confirmed that non-territorial males consistently mated with similar numbers of females and sired similar numbers of offspring as territorial males. Moreover, females were promiscuous in all three seasons with similar numbers of territorial and non-territorial males. However, promiscuity decreased offspring survivorship. Together, my results suggest that mating relationships among collared lizards contrast sharply with predictions from classical mating system theory and likely represent the outcome of sexual conflict. Both sexual conflict and the high reproductive success of non-territorial males appear to be promoted by the homogeneous and continuous topography of the semi-natural habitat at my study site, which differs markedly from the natural habitat of collared lizards.
Neural crest cells have been at the forefront of research on vertebrate development and evolution for over 150 years. These stem cells have the ability to create almost all of the cell types and ...structures that define the vertebrate clade, including the craniofacial skeleton, peripheral sensory nervous system, striking patterns of pigmentation, and much more. Our understanding of neural crest development has necessarily drawn upon research from diverse developmental models, including, fish, birds, and mammals. However, many of the early, fundamental insights into how these cells develop were obtained in amphibian model systems, especially Xenopus. This chapter reviews the contributions of amphibian model systems to neural crest research, with a particular focus on work in Xenopus. We discuss the historical role of amphibian developmental models in the early years of neural crest research and provide an overview of current thinking on neural crest development from a molecular and genomic perspective.
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