Endocrine differences among colour morphs in a lizard with alternative behavioural strategies

Yewers, Madeleine St Clair; Jessop, Tim S.; Stuart‐Fox, Devi

doi:10.1016/j.yhbeh.2017.05.001

Cited by 17 publications

(16 citation statements)

References 91 publications

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“…In lizards, male morphs differ in several traits including behaviour (Stephenson, ; Taylor & Lattanzio, ; Yewers, Pryke, & Stuart‐Fox, ), morphology (Huyghe, Vanhooydonck, Herrel, Tadic, & Van Damme, ; Stephenson, ), territory (Zamudio & Sinervo, ), parasitic load (Megía‐Palma et al., ) and physiology (LaDage, Riggs, Sinervo, & Pravosudov, ; Stephenson, ). However, different comparisons among morphs did not reveal any significant difference including morphometry (Meyers, Irschick, Vanhooydonck, & Herrel, ; Sacchi et al., ; Yewers, Jessop, & Stuart‐Fox, ), total of number of offspring and their survivorship (Zamudio & Sinervo, ), performance (Huyghe et al., ; Meyers et al., ), behaviour, microhabitat use, thermoregulation (Huyghe et al., ) and/or spermatogenic output (this study). Currently, we lack relevant data concerning lateral coloration in S .…”

Section: Discussionmentioning

confidence: 99%

Lack of spermatogenic variation in a polymorphic lizard, Sceloporus aeneus (Squamata: Phrynosomatidae)

et al. 2018

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Although different mechanisms exist to explain the presence of polymorphism in lizards, one model suggests that multiple morphotypes display the same level of fitness. Three male morphs (grey, yellow and orange) coexist in Sceloporus aeneus, a Mexican endemic oviparous lizard. Using a histological perspective, we test the hypothesis that spermatogenic output does not vary across morphotypes of S. aeneus during its maximum testicular activity. Males of S. aeneus (five grey, five yellow and five orange) were collected in Calimaya, Estado de México, Mexico. Snout‐vent length (SVL), testis mass, diameter and epithelial heights for the seminiferous tubules and epididymis, and the number of layers of germ cells did not vary among morphs; moreover, according to principal component analysis, a high overlap among lateral colour morphs exists. Our results suggest strongly that the lateral colour morphs in S. aeneus have the same spermatogenic output, and natural selection may be a stronger driving force than sexual selection within this species. Further studies into other lizard species with multiple morphotypes are required to determine whether the lack of variation in spermatogenic output observed in this endemic lizard is consistent across polymorphic species which will provide a greater understanding of the selective mechanisms acting on an individual’s fitness.

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Section: Discussionmentioning

confidence: 99%

Lack of spermatogenic variation in a polymorphic lizard, Sceloporus aeneus (Squamata: Phrynosomatidae)

et al. 2018

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“…This supertype was also associated with male throat color; the gray morph was more likely to possess supertype four compared to other morphs. The gray morph is the least bold and least aggressive and has low testosterone levels compared to the three other male morphs (Yewers, Jessop, & Stuart‐Fox, ; Yewers et al., ). Despite these characteristics likely reducing the ability of gray morphs to defend territories and obtain mates, the gray morph is present within all polymorphic populations, implying a compensatory selective advantage (McLean et al., ).…”

Section: Discussionmentioning

confidence: 99%

Specific MHC class I supertype associated with parasite infection and color morph in a wild lizard population

Hacking

Stuart‐Fox

Godfrey

et al. 2018

Ecology and Evolution

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The major histocompatibility complex (MHC) is a large gene family that plays a central role in the immune system of all jawed vertebrates. Nonavian reptiles are underrepresented within the MHC literature and little is understood regarding the mechanisms maintaining MHC diversity in this vertebrate group. Here, we examined the relative roles of parasite‐mediated selection and sexual selection in maintaining MHC class I diversity of a color polymorphic lizard. We discovered evidence for parasite‐mediated selection acting via rare‐allele advantage or fluctuating selection as ectoparasite load was significantly lower in the presence of a specific MHC supertype (functional clustering of alleles): supertype four. Based on comparisons between ectoparasite prevalence and load, and assessment of the impact of ectoparasite load on host fitness, we suggest that supertype four confers quantitative resistance to ticks or an intracellular tickborne parasite. We found no evidence for MHC‐associated mating in terms of pair genetic distance, number of alleles, or specific supertypes. An association was uncovered between supertype four and male throat color morph. However, it is unlikely that male throat coloration acts as a signal of MHC genotype to conspecifics because we found no evidence to suggest that male throat coloration predicts male mating status. Overall, our results suggest that parasite‐mediated selection plays a role in maintaining MHC diversity in this population via rare‐allele advantage and/or fluctuating selection. Further work is required to determine whether sexual selection also plays a role in maintaining MHC diversity in agamid lizards.

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“…Alternatively, captive tawny dragons that have reduced breeding opportunities may more readily allocate resources away from producing ornamental coloration. Ctenophorus decresii is polymorphic for male throat coloration, but color morphs do not differ in their response to capture stress (Yewers et al., ) despite their differences in aggressiveness and boldness (Yewers et al., ). Consistent with this, color morphs did not differ in effects of stress on color expression, with effects observed across skin colors within and between morphs.…”

Section: Discussionmentioning

confidence: 99%

“…Males in northern populations are polymorphic for throat color, with four discrete morphs: gray (dark gray and cream reticulation with no orange or yellow), yellow (varying amounts of yellow with cream and dark gray reticulations), orange (varying amounts of orange with cream and dark gray reticulations), and orange+yellow (orange center surrounded by yellow) (Figure 1b-e). The color morphs differ in behavior (Yewers, Pryke, & Stuart-Fox, 2016) and associated endocrine levels (Yewers, Jessop, & Stuart-Fox, 2017). Although color morphs and color expression (amount of orange or yellow) are heritable, there is nevertheless substantial variation between individuals in the extent of coloration and patterning within each morph category (Rankin, McLean, Kemp, & Stuart-Fox, 2016).…”

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confidence: 99%

Stress‐induced changes in color expression mediated by iridophores in a polymorphic lizard

Lewis

Rankin

Pask

et al. 2017

Ecology and Evolution

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Stress is an important potential factor mediating a broad range of cellular pathways, including those involved in condition‐dependent (i.e., honest) color signal expression. However, the cellular mechanisms underlying the relationship between stress and color expression are largely unknown. We artificially elevated circulating corticosterone levels in male tawny dragon lizards, Ctenophorus decresii, to assess the effect of stress on the throat color signal. Corticosterone treatment increased luminance (paler throat coloration) and decreased the proportion of gray, thereby influencing the gray reticulations that produce unique patterning. The magnitude of change in luminance for corticosterone‐treated individuals in our study was around 6 “just noticeable differences” to the tawny dragon visual system, suggesting that lizards are likely to be able to perceive the measured variation. Transmission electron microscopy (TEM) of iridophore cells indicated that luminance increased with increasing density of iridophore cells and increased spacing (and/or reduced size) of crystalline guanine platelets within them. Crystal spacing within iridophores also differed between skin colors, being greater in cream than either gray or yellow skin and greater in orange than yellow skin. Our results demonstrate that stress detectably impacts signal expression (luminance and patterning), which may provide information on individual condition. This effect is likely to be mediated, at least in part, by structural coloration produced by iridophore cells.

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Endocrine differences among colour morphs in a lizard with alternative behavioural strategies

Cited by 17 publications

References 91 publications

Lack of spermatogenic variation in a polymorphic lizard, Sceloporus aeneus (Squamata: Phrynosomatidae)

Lack of spermatogenic variation in a polymorphic lizard, Sceloporus aeneus (Squamata: Phrynosomatidae)

Specific MHC class I supertype associated with parasite infection and color morph in a wild lizard population

Stress‐induced changes in color expression mediated by iridophores in a polymorphic lizard

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