Colour polymorphic species are model systems for examining the evolutionary processes that generate and maintain discrete phenotypic variation in natural populations. Lizards have repeatedly evolved strikingly similar polymorphic sexual signals in distantly related lineages, providing an opportunity to examine convergence and divergence in colour polymorphism, correlated traits and associated evolutionary processes. Herein, we synthesise the extensive literature on lizard colour polymorphisms in both sexes, including recent advances in understanding of the underlying biochemical, cellular and genetic mechanisms, and correlated behavioural, physiological and life‐history traits. Male throat, head or ventral colour morphs generally consist of red/orange, yellow and white/blue morphs, and sometimes mixed morphs with combinations of two colours. Despite these convergent phenotypes, there is marked divergence in correlated behavioural, physiological and life‐history traits. We discuss the need for coherence in morph classification, particularly in relation to ‘mixed’ morphs. We highlight future research directions such as the genetic basis of convergent phenotypes and the role of environmental variation in the maintenance of polymorphism. Research in this very active field promises to continue to provide novel insights with broad significance to evolutionary biologists.

Diesel exhaust particles (DEP) are the major constituent of ambient particulate matter in urban environments and occupational settings. Exposure to DEP in combination with an allergen has been demonstrated to enhance allergen-related airway inflammation, immunoglobulin (Ig) E production, and airway responsiveness (AR) in human and in animal models. However, the mechanisms behind these effects of DEP are not yet fully understood. In this study, we compared the effects of short-term DEP exposure on ovalbumin (OVA)-mediated airway responses under two exposure protocols using an OVA-allergic rat model. Male Brown Norway rats were sensitized to aerosolized OVA (40.5 ± 6.3 mg/m 3) on days 1, 8, and 15, and challenged with OVA on day 29. The rats were exposed to DEP (20 mg/m 3) for 4 h/day for 5 consecutive days either before sensitization (protocol A) or before OVA challenge on days 24-28 (protocol B). Control animals received filtered air and aerosolized saline instead of DEP and OVA, respectively. The results showed that DEP exposure 1) elicited an adjuvant effect on OVA-specific IgE and IgG production in serum under both protocols; 2) significantly reduced OVA-induced airway inflammation and lung injury in protocol A, but increased these markers in protocol B; 3) markedly lowered OVA-induced production of nitric oxide, reactive oxygen species, and interleukin (IL)-10 and IL-12 by alveolar macrophages (AM) in protocol A, but increased these parameters in protocol B; 4) significantly lowered the numbers of T cells and their CD4 + and CD8 + subsets in lungdraining lymph nodes in protocol A, but increased these cell counts in protocol B; 5) reduced intracellular glutathione in AM and lymphocytes in both protocols; and 6) enhanced AR of the OVA-sensitized rats to methacholine challenge in protocol B. These results suggest that the effects of DEP on the immune system, including aggravation or exacerbation of asthma, may be greatly influenced by allergic immune status and time of antigen exposure. vi

17Colour polymorphism can promote rapid evolution and speciation, particularly when 18 populations differ in the number or composition of morphs. The tawny dragon, Ctenophorus 19 decresii, is a compelling study system in which to examine evolutionary processes and 20 outcomes when polymorphic and monomorphic lineages meet. The species comprises a 21 northern lineage polymorphic for male throat coloration which lacks ultraviolet (UV) 22 reflectance and a monomorphic southern lineage with UV-blue throats. We characterised 23 genomic and phenotypic clines across the contact zone based on single nucleotide 24 polymorphisms, the mitochondrial ND4 gene, and male colour traits, and concurrently 25 assessed the phenotype of captive-bred F1 hybrids. Our results indicate that genomic 26 introgression is asymmetric, with high frequencies of backcrossing to the northern but not 27 southern lineage, accompanied by the prevalence of the northern mtDNA haplotype in 28 hybrids. The clines for throat phenotype are abrupt and displaced to the south, relative to the 29 genetic and dorsolateral phenotype clines. This suggests strong selection for the northern 30 throat phenotype within the contact zone, particularly for the absence of ultraviolet 31 reflectance, given the intermediate throat phenotype in captive-bred F1 hybrids. Our results 32 demonstrate that a polymorphic sexual signal is the target of selection during incipient 33 speciation and provide insight into the microevolutionary processes linking polymorphism 34 and speciation.35 36

The goal of this protocol is to mimic the biomechanics of physiological accommodation in a cost-efficient, practical manner. Accommodation is achieved through the contraction of the ciliary body and relaxation of zonule fibers, which results in the thickening of the lens necessary for near vision. Here, we present a novel, simple method in which accommodation is replicated by tensing the zonules connected to the lens capsule via a manual lens stretcher (MLS). This method monitors the radial stretching achieved by a lens when subjected to a consistent force and allows for a comparison of accommodating lenses, which can be stretched, to non-accommodating lenses, which cannot be stretched. Importantly, the stretcher couples to the zonules directly, and not to the sclera of the eye, thus only requiring the lens, zonules, and ciliary body rather than the entire globe sample. This difference can significantly decrease the cost of acquiring donor cadaver lenses by about 62% compared to acquiring an entire globe.

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The outcome of secondary contact between divergent lineages or species may be influenced by both the reproductive traits of parental species and the fitness of offspring; however, their relative contributions have rarely been evaluated, particularly in longer‐lived vertebrate species. We performed pure and reciprocal laboratory crosses between Ctenophorus decresii (tawny dragon) and C. modestus (swift dragon) to examine how parental reproductive traits and ecologically relevant offspring fitness traits may explain contact zone dynamics in the wild. The two species meet in a contact zone of post‐F1 hybrids with asymmetric backcrossing and predominantly C. modestus mtDNA haplotypes. We found no evidence for reduced parental fecundity or offspring fitness for F1 hybrid crosses. However, maternal reproductive strategy differed between species, irrespective of the species of their mate. Ctenophorus modestus females had higher fecundity and produced more and larger clutches with lower embryonic mortality. Parental species also influenced sex ratios and offspring traits, with C. modestus ♀ × C. decresii ♂ hybrids exhibiting higher trait values for more fitness measures (growth rate, sprint speed, bite force) than offspring from all other pairings. Together, these patterns are consistent with the prevalence of C. modestus mtDNA in the contact zone, and asymmetric backcrossing likely reflects fitness effects that manifest in the F2 generation. Our results highlight how parental species can influence multiple offspring traits in different ways, which together may combine to influence offspring fitness and shape contact zone dynamics.

Australian lizards are a diverse group distributed across the continent and inhabiting a wide range of environments. Together, they exhibit a remarkable diversity of reproductive morphologies, physiologies, and behaviours that is broadly representative of vertebrates in general. Many reproductive traits exhibited by Australian lizards have evolved independently in multiple lizard lineages, including sociality, complex signalling and mating systems, viviparity, and temperature-dependent sex determination. Australian lizards are thus outstanding model organisms for testing hypotheses about how reproductive traits function and evolve, and they provide an important basis of comparison with other animals that exhibit similar traits. We review how research on Australian lizard reproduction has contributed to answering broader evolutionary and ecological questions that apply to animals in general. We focus on reproductive traits, processes, and strategies that are important areas of current research, including behaviours and signalling involved in courtship; mechanisms involved in mating, egg production, and sperm competition; nesting and gestation; sex determination; and finally, birth in viviparous species. We use our review to identify important questions that emerge from an understanding of this body of research when considered holistically. Finally, we identify additional research questions within each topic that Australian lizards are well suited for reproductive biologists to address.

The sensory drive hypothesis predicts the correlated evolution of signaling traits and sensory perception in differing environments. For visual signals, adaptive divergence in both color signals and visual sensitivities between populations may contribute to reproductive isolation and promote speciation, but this has rarely been tested or shown in terrestrial species. We tested whether opsin protein expression differs between divergent lineages of the tawny dragon (Ctenophorus decresii) that differ in the presence/absence of an ultraviolet sexual signal. We measured the expression of four retinal cone opsin genes (SWS1, SWS2, RH2, and LWS) using droplet digital PCR. We show that gene expression between lineages does not differ significantly, including the UV wavelength sensitive SWS1. We discuss these results in the context of mounting evidence that visual sensitivities are highly conserved in terrestrial systems. Multiple competing requirements may constrain divergence of visual sensitivities in response to sexual signals. Instead, signal contrast could be increased via alternative mechanisms, such as background selection. Our results contribute to a growing understanding of the roles of visual ecology, phylogeny, and behavior on visual system evolution in reptiles.