scholarly journals Distinctive convergence in Australian floral colours seen through the eyes of Australian birds

2014 ◽  
Vol 281 (1781) ◽  
pp. 20132862 ◽  
Author(s):  
Martin Burd ◽  
C. Tristan Stayton ◽  
Mani Shrestha ◽  
Adrian G. Dyer
Keyword(s):  
Visual System ◽  
Significant Degree ◽  
Floral Colour ◽  
Pollination Syndrome ◽  
Ancestral State ◽  
Colour Space ◽  
Bird Pollination ◽  
Long Wavelength ◽  
Avian Vision ◽  
Australian Birds

We used a colour-space model of avian vision to assess whether a distinctive bird pollination syndrome exists for floral colour among Australian angiosperms. We also used a novel phylogenetically based method to assess whether such a syndrome represents a significant degree of convergent evolution. About half of the 80 species in our sample that attract nectarivorous birds had floral colours in a small, isolated region of colour space characterized by an emphasis on long-wavelength reflection. The distinctiveness of this ‘red arm’ region was much greater when colours were modelled for violet-sensitive (VS) avian vision than for the ultraviolet-sensitive visual system. Honeyeaters (Meliphagidae) are the dominant avian nectarivores in Australia and have VS vision. Ancestral state reconstructions suggest that 31 lineages evolved into the red arm region, whereas simulations indicate that an average of five or six lineages and a maximum of 22 are likely to have entered in the absence of selection. Thus, significant evolutionary convergence on a distinctive floral colour syndrome for bird pollination has occurred in Australia, although only a subset of bird-pollinated taxa belongs to this syndrome. The visual system of honeyeaters has been the apparent driver of this convergence.

Bird pollination syndrome is the plant's adaptation to ornithophily, but nectarivorous birds are not so selective

Oikos ◽  
2021 ◽  
Author(s):  
Kryštof Chmel ◽  
Francis Luma Ewome ◽  
Guillermo Uceda Gómez ◽  
Yannick Klomberg ◽  
Jan E. J. Mertens ◽  
...  
Keyword(s):  
Pollination Syndrome ◽  
Bird Pollination

scholarly journals Spectral memory: Illumination-evoked plasticity

2018 ◽  
Author(s):  
Ifedayo-Emmanuel Adeyefa-Olasupo
Keyword(s):  
Visual System ◽  
Real World ◽  
Human Visual System ◽  
Retinal Image ◽  
Spectral Composition ◽  
Colour Space ◽  
The Core ◽  
Core Set ◽  
Group 2 ◽  
Group 1

AbstractHere human trichromats were presented with two types of scenes – geometric and real-world scenes –tinted with a shade of colour in order to destabilize the perceived illumination, and chromaticity of the retinal image of each scene. Each trichromat was instructed to adjust the chromaticity of the object embedded within each scene until its surface appeared devoid of any hue in the DKL colour space which spans two chromatic opponent axes – the S–(L+M) and L– M axis – and a luminance axis – the L+M axis. The following observations were made : (i) across scenes, adjustments were dispersed along the S–(L+M) axis, along which daylight is known to vary; (ii) across trichromats, for the geometric scenes, adjustments were biased towards the S pole of the S–(L+M) axis for one group (group 1), and towards the (L+M) pole for the other group (group 2); (iii) for the real-world scenes, adjustments for both groups systematically converged towards the (L+M) pole. These results suggest that when the core set of priors upon which the human visual system typically relies become ill-equipped, the human visual system is able to recruit one of the two illumination priors – PriorS or PriorL+M – in combination with the representation it has formed over time about the spectral composition of the illuminant associated with scenes the trichromatic observer is currently being exposed to within its ecological niche, as it attempts to stabilize the chromaticity of the retinal image of real-world scenes.

The influence of stimulus and background colour on signal visibility in the lizard Anolis cristatellus

2001 ◽  
Vol 204 (9) ◽  
pp. 1559-1575 ◽  
Author(s):  
L.J. Fleishman ◽  
M. Persons
Keyword(s):  
Visual System ◽  
Brightness Contrast ◽  
System Response ◽  
Signal Design ◽  
Light Conditions ◽  
Chromatic Contrast ◽  
Long Wavelength ◽  
Peak Sensitivity ◽  
Multi Linear Regression ◽  
To Receive

Anoline lizards communicate with visual displays in which they open and close a colourful throat fan called the dewlap. We used a visual fixation reflex as an assay to test the effects of stimulus versus background chromatic and brightness contrast on the probability of detecting a moving coloured (i.e. dewlap-like) stimulus in Anolis cristatellus. The probability of stimulus detection depended on two additive visual-system channels, one responding to brightness contrast and one responding to chromatic contrast, independent of brightness. The brightness channel was influenced only by wavelengths longer than 450nm and probably received input only from middle- and/or long-wavelength photoreceptors. The chromatic contrast channel appeared to receive input from three, or possibly four, different classes of cone in the anoline retina, including one with peak sensitivity in the ultraviolet. We developed a multi-linear regression equation that described most of the results of this study to a reasonable degree of accuracy. In the future, this equation could be used to predict the relative visibility of different-coloured stimuli in different habitat light conditions, which should be very useful for testing hypotheses that attempt to relate habitat light conditions and visual-system response to the evolution of signal design.

scholarly journals The Manú Gradient as a study system for bird pollination

2018 ◽  
Vol 6 ◽  
pp. e22241 ◽  
Author(s):  
Mannfred Boehm ◽  
Micah Scholer ◽  
Jeremiah Kennedy ◽  
Julian Heavyside ◽  
Aniceto Daza ◽  
...  
Keyword(s):  
Plant Species ◽  
Pollination Syndrome ◽  
Published Data ◽  
Bird Pollination ◽  
University Of British Columbia ◽  
San Pedro ◽  
History Of ◽  
Voucher Specimens ◽  
The University ◽  
Species Being

This study establishes an altiudinal gradient, spanning from the highland Andes (2400 m) to lowland Amazon, as a productive region for the study of bird pollination in Southeastern Peru. The 'Manú Gradient' has a rich history of ornithological research, the published data and resources from which lay the groundwork for analyses of plant-bird interactions. In this preliminary expedition we documented 44 plants exhibting aspects of the bird pollination syndrome, and made field observations of hummingbird visits at three sites spanning the Manú Gradient: 2800 m (Wayqecha), 1400 m (San Pedro), and 400 m (Pantiacolla). Some of the documented plant taxa are underrepresented in the bird pollination literature and could be promising avenues for future analyses of their pollination biology. The Manú Gradient is currently the focus of a concerted, international effort to describe and study the birds in the region; we propose that this region of Southeastern Peru is a productive and perhaps underestimated system to gain insight into the ecology and evolution of bird pollination.Observations were made on 11, 19, and 14 putatively bird pollinated plant species found at the high-, mid- and low-elevation sites along the gradient, respectively. Hummingbirds visited 18 of these plant species, with some plant species being visited by multiple hummingbird species or the same hummingbird species on differing occasions. Morphometric data is presented for putatively bird-pollinated plants, along with bill measurements from hummingbirds captured at each of three sites. Voucher specimens from this study are deposited in the herbaria of the Universidad Nacional de Agraria de La Molina (MOL), Peru and the University of British Columbia (UBC), Canada. The specimens collected represent a ‘snapshot’ of the diversity of bird-pollinated flora as observed over 10 day sampling windows (per site) during the breeding season for hummingbirds of Manú .

scholarly journals Hierarchical organization of macaque and cat cortical sensory systems explored with a novel network processor

2000 ◽  
Vol 355 (1393) ◽  
pp. 71-89 ◽  
Author(s):  
Claus–C. Hilgetag ◽  
Marc A. O'Neill ◽  
Malcolm P. Young
Keyword(s):  
Visual System ◽  
Low Cost ◽  
Significant Degree ◽  
Sensory Systems ◽  
Network Processor ◽  
Hierarchical Organization ◽  
Cortical Areas ◽  
Hierarchical Relationships ◽  
Hierarchical Constraints ◽  
Anatomical Constraints

Neuroanatomists have described a large number of connections between the various structures of monkey and cat cortical sensory systems. Because of the complexity of the connection data, analysis is required to unravel what principles of organization they imply. To date, analysis of laminar origin and termination connection data to reveal hierarchical relationships between the cortical areas has been the most widely acknowledged approach. We programmed a network processor that searches for optimal hierarchical orderings of cortical areas given known hierarchical constraints and rules for their interpretation. For all cortical systems and all cost functions, the processor found a multitude of equally low–cost hierarchies. Laminar hierarchical constraints that are presently available in the anatomical literature were therefore insufficient to constrain a unique ordering for any of the sensory systems we analysed. Hierarchical orderings of the monkey visual system that have been widely reported, but which were derived by hand, were not among the optimal orderings. All the cortical systems we studied displayed a significant degree of hierarchical organization, and the anatomical constraints from the monkey visual and somatomotor systems were satisfied with very few constraint violations in the optimal hierarchies. The visual and somato–motor systems in that animal were therefore surprisingly strictly hierarchical. Most inconsistencies between the constraints and the hierarchical relationships in the optimal structures for the visual system were related to connections of area FST (fundus of superior temporal sulcus). W e found that the hierarchical solutions could be further improved by assuming that FSTconsists of two areas, which differ in the nature of their projections. Indeed, we found that perfect hierarchical arrangements of the primate visual system, without any violation of anatomical constraints, could be obtained under two reasonable conditions, namely the subdivision of FST into two distinct areas, whose connectivity we predict, and the abolition of at least one of the less reliable rule constraints. Our analyses showed that the future collection of the same type of laminar constraints, or the inclusion of new hierarchical constraints from thalamocortical connections, will not resolve the problem of multiple optimal hierarchical representations for the primate visual system. Further data, however, may help to specify the relative ordering of some more areas. This indeterminacy of the visual hierarchy is in part due to the reported absence of some connections between cortical areas. These absences are consistent with limited cross–talk between differentiated processing streams in the system. Hence, hierarchical representation of the visual system is affected by, and must take into account, other organizational features, such as processing streams.

Misinterpreting Changes of Illuminant on Complex Mondrian Patterns

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 111-111
Author(s):  
S M C Nascimento ◽  
D H Foster
Keyword(s):  
Visual System ◽  
Temperature Change ◽  
Short Wavelength ◽  
Choice Experiment ◽  
The Other ◽  
Invariant Cone ◽  
Colour Temperature ◽  
Long Wavelength ◽  
Naturally Occurring ◽  
Colour Changes

Ratios of cone excitations from different surfaces of the same coloured scene are almost invariant under illuminance changes, and might provide the cue by which the visual system discriminates illuminant from non-illuminant changes in coloured scenes. Previous work with pairs of surfaces showed that observers were able to detect small, naturally occurring, violations in these ratios (Nascimento and Foster, 1995 Perception24 Supplement, 60 – 61). In the present study, sensitivity to violations was assessed with more complex, Mondrian patterns. In a two-interval forced-choice experiment, two colour transformations of the same Mondrian pattern were compared by observers. The patterns comprised 7 × 7 coloured patches. Each patch was a simulation of a Munsell surface, and the whole pattern was illuminated by a Planckian illuminant of variable colour temperature. In one of the intervals only the colour temperature of the illuminant changed; in the other, the same colour-temperature change was made, but, in addition, the spectral reflectances of the surfaces were adjusted such that all cone ratios were exactly preserved for the three classes of cone. The task was to identify which of the intervals contained the pure illuminant change. Observers could reliably discriminate the intervals but systematically interpreted colour changes with invariant cone-ratios as being illuminant changes, with a probability that increased as the degree of violation of invariance increased. Performance depended mainly on long-wavelength-sensitive cones, less on medium-wavelength-sensitive cones, and little or not at all on short-wavelength-sensitive cones or luminance signals. Cone-excitation ratios, although sometimes unreliable, appear to be the dominant cue for deciding on the nature of colour changes.

scholarly journals The gamma response to colour hue in humans: Evidence from MEG

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0243237
Author(s):  
Gavin Perry ◽  
Nathan W. Taylor ◽  
Philippa C. H. Bothwell ◽  
Colette C. Milbourn ◽  
Georgina Powell ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Frequency Response ◽  
Visual Stimulation ◽  
Gamma Oscillations ◽  
Colour Space ◽  
Long Wavelength ◽  
Gamma Frequency ◽  
Full Screen ◽  
Gamma Power ◽  
Oscillatory Response

It has recently been demonstrated through invasive electrophysiology that visual stimulation with extended patches of uniform colour generates pronounced gamma oscillations in the visual cortex of both macaques and humans. In this study we sought to discover if this oscillatory response to colour can be measured non-invasively in humans using magnetoencephalography. We were able to demonstrate increased gamma (40–70 Hz) power in response to full-screen stimulation with four different colour hues and found that the gamma response is particularly strong for long wavelength (i.e. red) stimulation, as was found in previous studies. However, we also found that gamma power in response to colour was generally weaker than the response to an identically sized luminance-defined grating. We also observed two additional responses in the gamma frequency: a lower frequency response around 25–35 Hz that showed fewer clear differences between conditions than the gamma response, and a higher frequency response around 70–100 Hz that was present for red stimulation but not for other colours. In a second experiment we sought to test whether differences in the gamma response between colour hues could be explained by their chromatic separation from the preceding display. We presented stimuli that alternated between each of the three pairings of the three primary colours (red, green, blue) at two levels of chromatic separation defined in the CIELUV colour space. We observed that the gamma response was significantly greater to high relative to low chromatic separation, but that at each level of separation the response was greater for both red-blue and red-green than for blue-green stimulation. Our findings suggest that the stronger gamma response to red stimulation cannot be wholly explained by the chromatic separation of the stimuli.

Reproductive biology, ecology and conservation of Carmichaelia williamsii (Fabaceae), a vulnerable legume from New Zealand

1999 ◽  
Vol 5 (3) ◽  
pp. 179 ◽  
Author(s):  
Peter B. Heenan ◽  
Peter J. De Lange
Keyword(s):  
New Zealand ◽  
Reproductive Biology ◽  
Flower Morphology ◽  
Pollination Syndrome ◽  
Field Observations ◽  
Bird Pollination ◽  
The Poor ◽  
Morphology And Structure ◽  
Nectar Source ◽  
Conservation And Management

Carmichaelia williamsii is a threatened leguminous shrub that is most common on the Poor Knights Islands and Aldermen Islands, northern New Zealand. Flower morphology and structure of C. williamsii is suited to a bird pollination syndrome as the floral parts are stout, the petals yellow, the nectar source is distant from the stigma, and the flowers lack scent. The stigma is covered by a protective cuticle that prevents pollination until it is ruptured, which would usually be by foraging birds. Experimental self- and cross-pollinations demonstrated that if the cuticle is not ruptured fertilization will not occur, and that the species is self-compatible. Field observations on Aorangi Island, Poor Knights Islands, confirmed that C. williamsii is probably bird pollinated as plants in full flower were being systematically worked by the native passerine honeyeater the Bellbird (Anthornis me/anura; Meliphagidae). C. williamsii mainly grows in seral habitats, and populations often comprise plants of a similar height class. Introduced rats and the loss of pollinating birds could pose conservation and management problems for the species.

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