Comorbid attention deficit hyperactivity disorder and substance use disorder complexity and chronicity in treatment-seeking adults

Introduction and Aims - Attention deficit hyperactivity disorder (ADHD) is a known risk factor for substance use disorder (SUD); however, the potential additive contribution of comorbid ADHD to drug-specific dependence in SUD populations is largely unknown. The current study aimed to assess this association between ADHD symptoms and drug-specific SUD complexity and chronicity. Design and Methods - A cross-sectional survey was administered to a convenience sample of 489 adults receiving SUD treatment at 16 Australian drug and alcohol treatment centres between September 2010 and August 2011. Participants were screened for adult ADHD symptoms using the Adult ADHD Self-Report Scale. Associations between ADHD screening status and drug-specific SUD complexity and chronicity were assessed using multivariate logistic and modified Poisson regression analysis, controlling for a range of potential confounders. Results - Overall, 215 (44%) patients screened positive for concurrent adult ADHD and SUD. After Simes' correction, a significant positive association was observed between ADHD screening status and current amphetamine SUD (odds ratio (OR) = 1.85; 95% confidence interval (CI): 1.19–2.36). Patients who screened positive for ADHD were significantly more likely to report SUD history for heavy alcohol use (OR = 2.05; 95% CI: 1.21–3.45) and amphetamine (OR = 1.96; 95% CI: 1.26–3.06) as well as significantly increased risk of moderate (3–4 years) duration for benzodiazepine and amphetamine SUDs and long (≥5 years) duration for alcohol, opiates other than heroin or methadone, and amphetamine SUDs. Discussion and Conclusions - The findings provide evidence that there is increased drug dependence complexity and chronicity in treatment-seeking SUD patients who screen positively for ADHD, specifically for amphetamine, alcohol, opiates other than heroin or methadone, and benzodiazepines

The function and evolution of colour polymorphism in the tawny dragon lizard

© Dr Madeleine St Claire YewersColour polymorphic species are model systems to investigate the evolutionary processes that maintain intraspecific diversity within a population. Colour polymorphism occurs when two or more discrete, genetically inherited colour forms coexist within an interbreeding population. Almost ubiquitously, colour morphs differ in morphological, behavioural, ecological, life history and/or physiological traits in addition to colour that often form alternative strategies. Each strategy has optimal trait combinations that allow morphs to maximise fitness. Variation in the trait composition of morph-specific strategies has important implications for understanding life-history trade-offs and the maintenance of polymorphism within populations. Differences in morph composition and correlated traits between populations can also promote divergence and ultimately speciation. In this thesis, I investigate the evolutionary maintenance of colour polymorphism in the tawny dragon lizard, Ctenophorus decresii. I do so in two distinct ways; by assessing colour vision differences between genetically and geographically distinct monomorphic and polymorphic lineages, and by comparing a range of traits that could differentially affect the fitness of morphs within a colour polymorphic population. In the south of their range, male tawny dragons are monomorphic for throat coloration whereas in the north of their range, they are polymorphic. There are four discrete male colour morphs in polymorphic populations that vary in the presence/absence of yellow and orange coloration; the yellow morph, orange morph, grey morph and orange-yellow morph (a yellow background with a central orange patch). Throat colour is heritable, fixed for life, and is an important sexual signal. Males of the monomorphic southern lineage express ultraviolet (UV)-blue throat coloration, unlike males of the polymorphic northern lineage. Lineages meet at a narrow contact zone where genotypic admixture suggests potential barriers to gene flow and incipient speciation. I determined the cone photoreceptor spectral sensitivities using microspectrophotometry and opsin expression of the two lineages, to see if they differ, particularly in sensitivity to UV-blue wavelengths. I confirmed the presence of four single cone classes in both lineages and provide the first evidence of UV visual sensitivity in agamid lizards. However, whether the lineages differ in UV-blue sensitivity remains unresolved. Within a polymorphic northern population, I assessed a combination of traits associated with each colour morph. I found morph-specific alternative strategies differentiated by consistencies in behaviour and hormones. The orange morph has an aggressive strategy with high levels of androgens while the grey morph has a cautious strategy with low levels of baseline androgens. The yellow morph has a conditional strategy where its aggression depends on the colour of the intruder and exhibits a stress-induced androgen increase. The orange-yellow morph similarly shows aggression conditional on the colour of the intruder but it is the boldest with high levels of androgens. Morphs did not differ in performance (bite force) or space use, and there was no relationship between spatial arrangement and relatedness. However, genetic structure based on microsatellite markers indicated weak genetic differentiation between morphs. Therefore, there are minimal barriers to gene flow between morphs. Instead, frequency-dependent selection is likely to be maintaining polymorphism in the tawny dragon lizard

Space use and genetic structure do not maintain color polymorphism in a species with alternative behavioral strategies

Space use including territoriality and spatial arrangement within a population can reveal important information on the nature, dynamics, and evolutionary maintenance of alternative strategies in color polymorphic species. Despite the prevalence of color polymorphic species as model systems in evolutionary biology, the interaction between space use and genetic structuring of morphs within populations has rarely been examined. Here, we assess the spatial and genetic structure of male throat color morphs within a population of the tawny dragon lizard, Ctenophorus decresii. Male color morphs do not differ in morphology but differ in aggressive and antipredator behaviors as well as androgen levels. Despite these behavioral and endocrine differences, we find that color morphs do not differ in territory size, with their spatial arrangement being essentially random with respect to each other. There were no differences in genetic diversity or relatedness between morphs; however, there was significant, albeit weak, genetic differentiation between morphs, which was unrelated to geographic distance between individuals. Our results indicate potential weak barriers to gene flow between some morphs, potentially due to nonrandom pre- or postcopulatory mate choice or postzygotic genetic incompatibilities. However, space use, spatial structure, and nonrandom mating do not appear to be primary mechanisms maintaining color polymorphism in this system, highlighting the complexity and variation in alternative strategies associated with color polymorphism

Yewers et al 2018 Ecology and Evolution dataset

This file contains data on territory size, territory overlap and microsatellite genotypes of tawny dragon lizard male colour morphs

Data from: Space use and genetic structure do not maintain colour polymorphism in a species with alternative behavioural strategies

Space use including territoriality and spatial arrangement within a population can reveal important information on the nature, dynamics and evolutionary maintenance of alternative strategies in colour polymorphic species. Despite the prevalence of colour polymorphic species as model systems in evolutionary biology, the interaction between space-use and genetic structuring of morphs within populations has rarely been examined. Here we assess the spatial and genetic structure of male throat colour morphs within a population of the tawny dragon lizard, Ctenophorus decresii. Male colour morphs do not differ in morphology but differ in aggressive and anti-predator behaviours as well as androgen levels. Despite these behavioural and endocrine differences, we find that colour morphs do not differ in territory size, with their spatial arrangement being essentially random with respect to each other. There were no differences in genetic diversity or relatedness between morphs; however, there was significant, albeit weak, genetic differentiation between morphs, which was unrelated to geographic distance between individuals. Our results indicate potential weak barriers to gene flow between some morphs, potentially due to non-random pre- or post-copulatory mate choice or postzygotic genetic incompatibilities. However, space use, spatial structure and non-random mating do not appear to be primary mechanisms maintaining colour polymorphism in this system, highlighting the complexity and variation in alternative strategies associated with colour polymorphism

Behavioural differences across contexts may indicate morph-specific strategies in the lizard Ctenophorus decresii

Discrete colour polymorphisms are often genetically correlated with other traits under natural and sexual selection, such as behaviour, life history and physiology. Elucidating such correlations is essential to understand the adoption of alternative strategies between morphs and the role they play in the maintenance of colour polymorphisms within a population. Using field experiments, we tested the hypothesis that four visually discrete morphs (orange, yellow, yellow with a central orange patch (orange-yellow) and grey) of the tawny dragon lizard, Ctenophorus decresii, display alternative behavioural strategies. Specifically, we compared the response of colour morphs to simulated conspecific territorial intruders and predators in the wild. Although the orange-yellow morph can be objectively classified, it may behaviourally resemble the orange or yellow morph; therefore we compared statistical models in which the orange-yellow morph was considered a separate morph (four-morph model) or grouped with either pure orange or pure yellow individuals (three-morph models). For aggression, a three-morph model with orange-yellow individuals grouped as yellow morphs best fitted the data. The orange morph showed consistently high aggression to all morphs, while the grey morph showed consistently low aggression. Aggression of the yellow morph was conditional on the morph of the intruder. In addition to being the least aggressive, the grey morph was the least bold. Although the orange morph was the most aggressive, it was only the boldest under a three-morph model, which was equally likely compared to a four-morph model. Overall our results support the view that tawny dragon lizard morphs adopt different behavioural strategies, the orange and grey morphs exhibiting more aggressive and cautious strategies, respectively, and the yellow morph changing its aggression depending on its competitor's colour

Spectral sensitivity of cone photoreceptors and opsin expression in two colour-divergent lineages of the lizard Ctenophorus decresii

Intraspecific differences in sensory perception are rarely reported but may occur when a species range extends across varying sensory environments, or there is coevolution between the sensory system and a varying signal. Examples in colour vision and colour signals are rare in terrestrial systems. The tawny dragon lizard Ctenophorus decresii is a promising candidate for such intraspecific variation, because the species comprises two geographically and genetically distinct lineages in which throat colour (a social signal used in intra- and inter-specific interactions) is locally adapted to the habitat and differs between lineages. Male lizards from the southern lineage have UV-blue throats, whereas males from the northern lineage are polymorphic with four discrete throat colours that all show minimal UV reflectance. Here, we determine the cone photoreceptor spectral sensitivities and opsin expression of the two lineages, to test whether they differ, particularly in the UV wavelengths. Using microspectrophotometry on retinal cone photoreceptors, we identified a long-wavelength-sensitive (LWS) visual pigment, a \u27short\u27 and \u27long\u27 medium-wavelength-sensitive (MWS) pigment and a short-wavelength-sensitive (SWS) pigment, all of which did not differ in λmax between lineages. Through transcriptome analysis of opsin genes we found that both lineages express four cone opsin genes, including the SWS1 opsin with peak sensitivity in the UV range, and that amino acid sequences did not differ between lineages with the exception of a single leucine to valine substitution in the RH2 opsin. Counts of yellow and transparent oil droplets associated with LWS+MWS and SWS+UVS cones, respectively, showed no difference in relative cone proportions between lineages. Therefore, contrary to predictions, we find no evidence of differences between lineages in single cone photoreceptor spectral sensitivity or opsin expression. However, we confirm the presence of four single cone classes, suggesting tetrachromacy in C. decresii, and we also provide the first evidence of UV sensitivity in agamid lizards

Data from: Specific MHC class I supertype associated with parasite infection and colour morph in a wild lizard population

The major histocompatibility complex (MHC) is a large gene family that plays a central role in the immune system of all jawed vertebrates. Non-avian reptiles are under-represented 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 colour 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 tick-borne 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 colour morph. However, it is unlikely that male throat colouration acts as a signal of MHC genotype to conspecifics because we found no evidence to suggest that male throat colouration 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