| 1. |
- Tedore, Cynthia, et al.
(författare)
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The role of detectability in the evolution of avian-dispersed fruit color
- 2022
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Ingår i: Vision Research. - : Elsevier BV. - 0042-6989. ; 196
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Tidskriftsartikel (refereegranskat)abstract
- If the primary function of avian-dispersed fruit coloration were the maximization of detectability, then the commonest avian-dispersed fruit colors should be the ones most detectable to birds. We tested this prediction by photographing 63 fruit species primarily dispersed by birds, in situ in Sweden and Australia, with a multispectral camera closely mimicking the predominant spectral sensitivities of birds, including both UVS and VS (peak ultraviolet sensitivity ∼370 and 409 nm respectively) visual systems. Fruits were classified into nine distinct color categories based on different patterns of cone excitations, and were named by combining human color names with fruits’ UV reflective properties. For example, a bluish-UV fruit would be a fruit that excited the avian UV cone the most, but that also strongly excited the blue cone. Color and achromatic contrasts were calculated between each fruit color and common background objects, and compared to the relative abundance of the different fruit colors. Although red was highly detectable and the commonest color, the second and third commonest colors, purplish-UV and bluish-UV (often termed “black” by humans), were the least detectable. Although these latter two colors were more detectable to UVS than to VS birds, they were the least detectable to both visual systems. Rare fruit colors, such as UVish-purple, pink, and orange, were highly detectable to both visual systems. The lack of correlation between fruit color abundance and detectability suggests that the maximization of detectability has not been the primary driving force behind the evolution of fruit color.
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| 2. |
- Chouinard-Thuly, Laura, et al.
(författare)
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Technical and conceptual considerations for using animated stimuli in studies of animal behavior
- 2017
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Ingår i: Current Zoology. - : Oxford University Press (OUP). - 1674-5507 .- 2396-9814. ; 63:1, s. 5-19
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Tidskriftsartikel (refereegranskat)abstract
- Rapid technical advances in the field of computer animation (CA) and virtual reality (VR) have opened new avenues in animal behavior research. Animated stimuli are powerful tools as they offer standardization, repeatability, and complete control over the stimulus presented, thereby "reducing" and "replacing" the animals used, and "refining" the experimental design in line with the 3Rs. However, appropriate use of these technologies raises conceptual and technical questions. In this review, we offer guidelines for common technical and conceptual considerations related to the use of animated stimuli in animal behavior research. Following the steps required to create an animated stimulus, we discuss (I) the creation, (II) the presentation, and (III) the validation of CAs and VRs. Although our review is geared toward computer-graphically designed stimuli, considerations on presentation and validation also apply to video playbacks. CA and VR allow both new behavioral questions to be addressed and existing questions to be addressed in new ways, thus we expect a rich future for these methods in both ultimate and proximate studies of animal behavior.
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| 3. |
- Glenszczyk, Mateusz, et al.
(författare)
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The jumping spider Saitis barbipes lacks a red photoreceptor to see its own sexually dimorphic red coloration
- 2022
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Ingår i: Science of Nature. - : Springer Science and Business Media LLC. - 0028-1042 .- 1432-1904. ; 109:1
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Tidskriftsartikel (refereegranskat)abstract
- Examining the role of color in mate choice without testing what colors the study animal is capable of seeing can lead to ill-posed hypotheses and erroneous conclusions. Here, we test the seemingly reasonable assumption that the sexually dimorphic red coloration of the male jumping spider Saitis barbipes is distinguishable, by females, from adjacent black color patches. Using microspectrophotometry, we find clear evidence for photoreceptor classes with maximal sensitivity in the UV (359 nm) and green (526 nm), inconclusive evidence for a photoreceptor maximally sensitive in the blue (451 nm), and no evidence for a red photoreceptor. No colored filters within the lens or retina could be found to shift green sensitivity to red. To quantify and visualize whether females may nevertheless be capable of discriminating red from black color patches, we take multispectral images of males and calculate photoreceptor excitations and color contrasts between color patches. Red patches would be, at best, barely discriminable from black, and not discriminable from a low-luminance green. Some color patches that appear achromatic to human eyes, such as beige and white, strongly absorb UV wavelengths and would appear as brighter “spider-greens” to S. barbipes than the red color patches. Unexpectedly, we discover an iridescent UV patch that contrasts strongly with the UV-absorbing surfaces dominating the rest of the spider. We propose that red and black coloration may serve identical purposes in sexual signaling, functioning to generate strong achromatic contrast with the visual background. The potential functional significance of red coloration outside of sexual signaling is discussed.
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| 4. |
- Tedore, Cynthia, et al.
(författare)
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Avian UV vision enhances leaf surface contrasts in forest environments
- 2019
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- UV vision is prevalent, but we know little about its utility in common general tasks, as in resolving habitat structure. Here we visualize vegetated habitats using a multispectral camera with channels mimicking bird photoreceptor sensitivities across the UV-visible spectrum. We find that the contrast between upper and lower leaf surfaces is higher in a UV channel than in any visible channel, and that this makes leaf position and orientation stand out clearly. This was unexpected since both leaf surfaces reflect similarly small proportions (1-2%) of incident UV light. The strong UV-contrast can be explained by downwelling light being brighter than upwelling, and leaves transmitting < 0.06% of incident UV light. We also find that mirror-like specular reflections of the sky and overlying canopy, from the waxy leaf cuticle, often dwarf diffuse reflections. Specular reflections shift leaf color, such that maximum leaf-contrast is seen at short UV wavelengths under open canopies, and at long UV wavelengths under closed canopies.
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| 5. |
- Tedore, Cynthia, et al.
(författare)
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Disentangling the visual cues used by a jumping spider to locate its microhabitat
- 2016
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 219, s. 2396-2401
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Tidskriftsartikel (refereegranskat)abstract
- Many arthropod species have evolved to thrive only on the leaves of a particular species of plant, which they must be capable of finding in order to survive accidental displacement, developmental transitions, or the changing of the seasons. A number of studies have tested whether such species select leaves to land or oviposit on based on their color, shape, or size. Unfortunately, many studies did not control for correlates of these characters, such as the brightness of different colors, the areas of different shapes, and the level of ambient illumination in the vicinity of different sizes of leaves. In the present study, we tested for leaf color, shape, and size preferences in a leaf-dwelling jumping spider (Lyssomanes viridis) with known summer and winter host plants, while controlling for these correlates. First, color preferences were tested outdoors under the natural illumination of their forest habitat. L. viridis did not prefer to perch on a green substrate compared to various shades of gray, but did prefer the second darkest shade of gray we presented them with. Of the green and other gray substrates, this shade of gray's integrated photon flux (350-700 nm), viewed from below, i.e. the spider's perspective in the arena, was the most similar to real leaves. This relationship also held when we weighted the transmitted photon flux by jumping spiders' green photopigment spectral sensitivity. Spiders did not prefer the star-like leaf shape of their summer host plant, Liquidambar styraciflua, to a green circle of the same area. When given a choice between a sweet gum-shaped stimulus that was half the area of an otherwise identical alternative, spiders preferred the larger stimulus. However, placing a neutral density filter over the side of the experimental arena with the smaller stimulus abolished this preference, with spiders then being more likely to choose the side of the arena with the smaller stimulus. In conclusion, L. viridis appears to use ambient illumination and possibly perceived leaf brightness but not leaf shape or color to locate its microhabitat. This calls for a careful re-examination of which visual cues a variety of arthropods are actually attending to when they search for their preferred host species or microhabitat.
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| 6. |
- Tedore, Cynthia, et al.
(författare)
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Immunological dependence of plant-dwelling animals on the medicinal properties of their plant substrates: a preliminary test of a novel evolutionary hypothesis
- 2015
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Ingår i: Arthropod-Plant Interactions. - : Springer Science and Business Media LLC. - 1872-8855 .- 1872-8847. ; 9:5, s. 437-446
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Tidskriftsartikel (refereegranskat)abstract
- We present preliminary evidence for a novel evolutionary hypothesis, i.e., that animals living on plants high in antimicrobial secondary metabolites could, via drift or selection, evolve weakened immune defenses and an immunological dependence on the antimicrobial properties of their plant substrate and/or the volatile mix in the air surrounding their plant. Animals experience immunological stress during developmental transitions, so we evaluated our hypothesis by testing for an effect of plant substrate on hatching success in the jumping spider Lyssomanes viridis, a species that constructs its egg sacs on Liquidambar styraciflua leaves. Compared with other sympatric species, L. styraciflua is known to be high in potent volatile broad-spectrum antimicrobial compounds, most notably, the monoterpene terpinen-4-ol, a well-studied antimicrobial agent known from tea tree oil. We found that L. viridis experience higher hatching success on L. styraciflua than on other sympatric species or plastic substrate controls and that L. viridis has a chemically mediated preference for this plant. In contrast to other spiders' compact, densely woven egg sacs, L. viridis' egg sacs are sparsely woven and the eggs widely spaced, maximizing the eggs' surface area exposed to volatiles coming off the leaf. Similar architectures exist in distantly related taxa, suggesting convergent evolution. Our theoretical framework and preliminary results open up an unexplored frontier-the possibility that any number of plant-dwelling species may depend upon on the antimicrobial properties of the plant tissues they inhabit.
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| 7. |
- Tedore, Cynthia, et al.
(författare)
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Ultraviolet vision aids the detection of nutrient-dense non-signaling plant foods
- 2021
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Ingår i: Vision Research. - : Elsevier BV. - 0042-6989. ; 183, s. 16-29
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Tidskriftsartikel (refereegranskat)abstract
- To expand our understanding of what tasks are particularly helped by UV vision and may justify the costs of focusing high-energy light onto the retina, we used an avian-vision multispectral camera to image diverse vegetated habitats in search of UV contrasts that differ markedly from visible-light contrasts. One UV contrast that stood out as very different from visible-light contrasts was that of nutrient-dense non-signaling plant foods (such as young leaves and immature fruits) against their natural backgrounds. From our images, we calculated color contrasts between 62+ species of such foods and mature foliage for the two predominant color vision systems of birds, UVS and VS. We also computationally generated images of what a generalized tetrachromat, unfiltered by oil droplets, would see, by developing a new methodology that uses constrained linear least squares to solve for optimal weighted combinations of avian camera filters to mimic new spectral sensitivities. In all visual systems, we found that nutrient-dense non-signaling plant foods presented a lower, often negative figure-ground contrast in the UV channels, and a higher, often positive figure-ground contrast in the visible channels. Although a zero contrast may sound unhelpful, it can actually enhance color contrast when compared in a color opponent system to other channels with nonzero contrasts. Here, low or negative UV contrasts markedly enhanced color contrasts. We propose that plants may struggle to evolve better UV crypsis since UV reflectance from vegetation is largely specular and thus highly dependent on object orientation, shape, and texture.
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| 8. |
- Tedore, Cynthia, et al.
(författare)
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Using RGB displays to portray color realistic imagery to animal eyes
- 2017
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Ingår i: Current Zoology. - : Oxford University Press (OUP). - 1674-5507 .- 2396-9814. ; 63:1, s. 27-34
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Tidskriftsartikel (refereegranskat)abstract
- RGB displays effectively simulate millions of colors in the eyes of humans by modulating the relative amount of light emitted by 3 differently colored juxtaposed lights (red, green, and blue). The relationship between the ratio of red, green, and blue light and the perceptual experience of that light has been well defined by psychophysical experiments in humans, but is unknown in animals. The perceptual experience of an animal looking at an RGB display of imagery designed for humans is likely to poorly represent an animal’s experience of the same stimulus in the real world. This is due, in part, to the fact that many animals have different numbers of photoreceptor classes than humans do and that their photoreceptor classes have peak sensitivities centered over different parts of the ultraviolet and visible spectrum. However, it is sometimes possible to generate videos that accurately mimic natural stimuli in the eyes of another animal, even if that animal’s sensitivity extends into the ultraviolet portion of the spectrum. How independently each RGB phosphor stimulates each of an animal’s photoreceptor classes determines the range of colors that can be simulated for that animal. What is required to determine optimal color rendering for another animal is a device capable of measuring absolute or relative quanta of light across the portion of the spectrum visible to the animal (i.e., a spectrometer), and data on the spectral sensitivities of the animal’s photoreceptor classes. In this article, we outline how to use such equipment and information to generate video stimuli that mimic, as closely as possible, an animal’s color perceptual experience of real-world objects.
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| 9. |
- Tedore, Cynthia, et al.
(författare)
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Visual mutual assessment of size in male Lyssomanes viridis jumping spider contests
- 2015
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Ingår i: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 26:2, s. 510-518
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Tidskriftsartikel (refereegranskat)abstract
- Numerous animals are known to assess the resource holding potential of their opponents using conventional signals and other correlates of resource holding potential. Although body and weapon size generally correlate with resource holding potential and are often presumed to be visually evaluated in animal contests, no one has demonstrated visual assessment of opponent size while controlling for all potential correlates of size. To this end, we presented male Lyssomanes viridis jumping spiders with computer-animated opponents 1) of 3 different overall sizes and 2) with different weapon and nonweapon appendages elongated by the amount that would normally accompany a 20% increase in body size. Male L. viridis have strikingly colored, exaggerated chelicerae and forelegs, which are used as weapons in contests, and the forelegs are waved during visual agonistic displays. We scored 4 levels of escalation in males’ responses to animations. Using generalized linear mixed modeling, we assessed the relative predictive power of the following variables on escalation intensity: 1) focal male size, 2) animated opponent size, and 3) the difference in size between the focal male and his animated opponent. When we presented males with animations scaled to different sizes, we found that size difference was the best predictor of escalation intensity, followed by opponent size. The effect of opponent size disappeared when size difference was included in the same model. Focal male size did not significantly predict escalation intensity. This suggests that males employ a mutual assessment strategy. Surprisingly, males did not respond differently to animations with versus without elongated weaponry.
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