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Ultraviolet (UV) light-transmitted signals play a major role in avian foraging and communication, subserving functional roles in feeding, mate choice, egg recognition, and nestling discrimination. Sequencing functionally relevant regions of the short wavelength sensitive type 1 (SWS1) opsin gene that is responsible for modulating the extent of SWS1 UV sensitivity in birds allows predictions to be made about the visual system's UV sensitivity in species where direct physiological or behavioral measures would be impractical or unethical. Here, we present SWS1 segment sequence data from representative species of three avian lineages for which visually based cues for foraging and communication have been investigated to varying extents. We also present a preliminary phylogenetic analysis and ancestral character state reconstructions of key spectral tuning sites along the SWS1 opsin based on our sequence data. The results suggest ubiquitous ultraviolet SWS1 sensitivity (UVS) in both paleognaths, including extinct moa (Emeidae), and parrots, including the nocturnal and flightless kakapo (Strigops habroptilus), and in most, but not all, songbird (oscine) lineages, and confirmed violet sensitivity (VS) in two suboscine families. Passerine hosts of avian brood parasites were included both UVS and VS taxa, but sensitivity did not co-vary with egg rejection behaviors. The results should stimulate future research into the functional parallels between the roles of visual signals and the genetic basis of visual sensitivity in birds and other taxa.
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... This is surprising because visible cues at a distance and, hence, greater visual acuity through relatively larger eyes [7] are both critical for parasites to locate host nests [8] and for hosts to recognize and prevent, dampen or eliminate parasitism (e.g. the detection of approaching adults, parasitic eggs and/or hatched chicks [9]). As the rare exception, one study examined whether a short-wavelength (SWS I) avian visual receptor was more often tuned for ultraviolet wavelengths in rejector over acceptor host species in a handful of passerine lineages but found no statistical evidence for such a predicted pattern [10]. Similarly, relative overall brain size (an indirect predictor of neural processing complexity of visual information such as the coloration of foreign eggs or the sight of well-hidden host nests) was not predictably larger in egg rejector compared with non-rejector host individuals intraspecifically [11] and was even smaller in rejector compared with acceptor hosts and in parasitic compared with non-parasitic lineages [12,13], although no study to date has assessed visual subregions in host or parasite brains. ...
... This is expected since avian brood parasitism has only evolved at seven independent origins of avian diversity [2], linking most of the approximately 100 avian obligate brood parasite species through often shared phylogenetic histories. Although this result may have arisen because brood parasites, in general, are larger in body size than hosts [10] and eye size is positively related to body dimensions [12], results were similar when using RES. ...
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In coevolutionary arms-races, reciprocal ecological interactions and their fitness impacts shape the course of phenotypic evolution. The classic example of avian host–brood parasite interactions selects for host recognition and rejection of increasingly mimetic foreign eggs. An essential component of perceptual mimicry is that parasitic eggs escape detection by host sensory systems, yet there is no direct evidence that the avian visual system covaries with parasitic egg recognition or mimicry. Here, we used eye size measurements collected from preserved museum specimens as a metric of the avian visual system for species involved in host–brood parasite interactions. We discovered that (i) hosts had smaller eyes compared with non-hosts, (ii) parasites had larger eyes compared with hosts before but not after phylogenetic corrections, perhaps owing to the limited number of independent evolutionary origins of obligate brood parasitism, (iii) egg rejection in hosts with non-mimetic parasitic eggs positively correlated with eye size, and (iv) eye size was positively associated with increased avian-perceived host–parasite eggshell similarity. These results imply that both host-use by parasites and anti-parasitic responses by hosts covary with a metric of the visual system across relevant bird species, providing comparative evidence for coevolutionary patterns of host and brood parasite sensory systems.
... Products taking birds' ultraviolet (UV) vision into account certainly meet such expectations (Aidala et al. 2012, Swaddle et al. 2020. The spectrum of birds' vision extends into the ultraviolet, thus UV markings that reflect differentially in the UV are visible to birds but mostly invisible for humans (Hart 2001, Lind et al. 2013. ...
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... 2006; Lhomme & Hines, 2019;Loope et al., 2017;Nehring et al., 2015), the evolution and function of sensory systems to facilitate their behavioral interactions and arms race remain poorly understood (Aidala et al., 2012;Stevens, 2013). Hosts have large sensory repertoires that facilitate general foraging decisions, social interactions, task allocation, and the recognition of nestmates as well as intruders. ...
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... 2006; Lhomme & Hines, 2019;Loope et al., 2017;Nehring et al., 2015), the evolution and function of sensory systems to facilitate their behavioral interactions and arms race remain poorly understood (Aidala et al., 2012;Stevens, 2013). Hosts have large sensory repertoires that facilitate general foraging decisions, social interactions, task allocation, and the recognition of nestmates as well as intruders. ...
Article
Obligate insect social parasites evolve traits to effectively locate and then exploit their hosts, whereas hosts have complex social behavioral repertoires, which include sensory recognition to reject potential conspecific intruders and heterospecific parasites. While social parasites and host behaviors have been studied extensively, less is known about how their sensory systems function to meet their specific selective pressures. Here, we compare investment in visual and olfactory brain regions in the paper wasp Polistes dominula, and its obligate social parasite P. sulcifer, to explore the links among sensory systems,brain and behavior. Our results show significant relative volumetric differences between these two closely related species, consistent with their very different life histories. Social parasites show proportionally larger optic lobes and central complex to likely navigate long-distance migrations and unfamiliar landscapes to locate the specific species of hosts they usurp. Contrastingly, hosts have larger antennal lobes and calyces of the mushroom bodies compared with social parasites, as predicted by their sensory means to maintain social cohesion via olfactory signals, allocate colony tasks, forage, and recognize conspecific and heterospecific intruders. Our work suggests how this tradeoff between visual and olfactory brain regions may facilitate different sensory adaptations needed to perform social and foraging tasks by the host, including recognition of parasites, or to fly long distances and successful host localizing by the social parasite.
... Additional details of these procedures can be found in Hodges et al. (2020). We acknowledge that a digital camera-based quantification of the appearance of eggshells does not allow for modelling of all the avian-perceivable visual cues, including ultraviolet reflectance (Aidala et al. 2012), but physically quantified differences from RGB cues are typically matched by avian-perceivable differences (e.g., Hauber et al. 2019; Price-Waldman and Stoddard 2021). ...
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Avian eggshell pigmentation may provide information about a female’s physiological condition, in particular her state of oxidative balance. Previously we found that female house wrens (Troglodytes aedon Vieillot, 1809) with lighter, less-maculated, and redder ground-colored shells were older and produced heavier offspring than females laying darker, browner eggs. The strong pro-oxidant protoporphyrin is responsible for this species’ eggshell pigmentation, so differences in pigmentary coloration may be related to eggshell protoporphyrin content and reflect female oxidative balance and condition during egg-formation. Therefore, we tested the assumption that egg-surface coloration is related to the amount of protoporphyrin in the shell matrix. We analyzed digital photographs of eggs to determine maculation coverage as a measure of the overall ground coloration of the egg and its red-, green-, and blue-channel pixel values. Pigments were then extracted from these same eggs and analyzed using high-performance liquid chromatography. There was a strong, positive relationship between eggshell redness and protoporphyrin content of eggshells, but no relationship between percent maculation and protoporphyrin content. Thus, when older, larger females deposit more protoporphyrin in their eggshells, this may reflect a tolerance for high levels of circulating protoporphyrin or an effective mechanism for off-loading protoporphyrin into the eggshell matrix. Keywords: Eggs, Female quality, HPLC, Eggshell pigmentation, Eggshell speckles
... This research has also defined a range of plants present in their respective environments that were avoided by moa; both these positive and negative selection processes were presumably driven by olfaction. Moa had the genetic information for ultraviolet (UV) vision [67]; foliage that moa were known to eat has not been tested for its appearance in UV light but this could yield interesting results. ...
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