scholarly journals Floral colour structure in two Australian herbaceous communities: it depends on who is looking

2019 ◽  
Vol 124 (2) ◽  
pp. 221-232 ◽  
Author(s):  
Mani Shrestha ◽  
Adrian G Dyer ◽  
Jair E Garcia ◽  
Martin Burd
Keyword(s):  
Flowering Plants ◽  
Floral Colour ◽  
Random Structure ◽  
Phylogenetic Structure ◽  
Colour Perception ◽  
Phylogenetic Relatedness ◽  
Herbaceous Communities ◽  
Hymenopteran Species ◽  
Complex Landscape ◽  
Colour Signals

Abstract Background and Aims Pollinator-mediated interactions between plant species may affect the composition of angiosperm communities. Floral colour signals should play a role in these interactions, but the role will arise from the visual perceptions and behavioural responses of multiple pollinators. Recent advances in the visual sciences can be used to inform our understanding of these perceptions and responses. We outline the application of appropriate visual principles to the analysis of the annual cycle of floral colour structure in two Australian herbaceous communities. Methods We used spectrographic measurements of petal reflectance to determine the location of flowers in a model of hymenopteran colour vision. These representations of colour perception were then translated to a behaviourally relevant metric of colour differences using empirically calibrated colour discrimination functions for four hymenopteran species. We then analysed the pattern of colour similarity in terms of this metric in samples of co-flowering plants over the course of a year. We used the same method to analyse the annual pattern of phylogenetic relatedness of co-flowering plants in order to compare colour structure and phylogenetic structure. Key Results Co-flowering communities at any given date seldom had colour assemblages significantly different from random. Non-random structure, both dispersion and clustering, occurred occasionally, but depended on which bee observer is considered. The degree of colour similarity was unrelated to phylogenetic similarity within a co-flowering community. Conclusions Perceived floral colour structure varied with the sensory capabilities of the observer. The lack of colour structure at most sample dates, particularly the rarity of strong dispersion, suggests that plants do not use chromatic signals primarily to enable bees to discriminate between co-flowering species. It is more likely that colours make plants detectable in a complex landscape.

Geophysical, evolutionary and ecological processes interact to drive phylogenetic dispersion in angiosperm assemblages along the longest elevational gradient in the world

2019 ◽  
Vol 190 (4) ◽  
pp. 333-344 ◽  
Author(s):  
Hong Qian ◽  
Brody Sandel ◽  
Tao Deng ◽  
Ole R Vetaas
Keyword(s):  
Plate Tectonics ◽  
Biotic Interactions ◽  
Elevational Gradient ◽  
Flowering Plants ◽  
Ecological Processes ◽  
Phylogenetic Structure ◽  
Phylogenetic Relatedness ◽  
The World ◽  
Net Relatedness Index ◽  
Phylogenetic Dispersion

AbstractEcologists have embraced phylogenetic measures of assemblage structure, in large part for the promise of better mechanistic inferences. However, phylogenetic structure is driven by a wide array of factors from local biotic interactions to biogeographical history, complicating the mechanistic interpretation of a pattern. This may be particularly problematic along elevational gradients, where rapidly changing physical and biological conditions overlap with geological and biogeographical history, potentially producing complex patterns of phylogenetic dispersion (relatedness). We focus on the longest elevational gradient of vegetation in the world (i.e. c. 6000 m in Nepal) to explore patterns of phylogenetic dispersion for angiosperms (flowering plants) along this elevational gradient. We used the net relatedness index to quantify phylogenetic dispersion for each elevational band of 100 m. We found a zig-zag pattern of phylogenetic dispersion along this elevational gradient. With increasing elevation, the phylogenetic relatedness of species decreased for the elevational segment between 0 and c. 2100 m, increased for the elevational segment between 2100 and c. 4200 m, and decreased for the elevational segment above c. 4200 m. We consider this pattern to be a result of the interaction of geophysical (e.g. plate tectonics) and eco-evolutionary processes (e.g. niche conservatism and trait convergence). We speculate on the mechanisms that might have generated this zig-zag pattern of phylogenetic dispersion.

Scale dependence in the phylogenetic relatedness of alien and native taxa

2020 ◽  
Vol 13 (5) ◽  
pp. 601-610
Author(s):  
Chris M McGrannachan ◽  
Gillis J Horner ◽  
Melodie A McGeoch
Keyword(s):  
Alien Species ◽  
Spatial Scale ◽  
Native Species ◽  
Spatial Scales ◽  
Pairwise Distance ◽  
Phylogenetic Structure ◽  
Phylogenetic Clustering ◽  
Phylogenetic Relatedness ◽  
Darwin's Naturalization Hypothesis ◽  
Darwin’S Naturalization Hypothesis

Abstract Aims Darwin’s naturalization hypothesis proposes that successfully established alien species are less closely related to native species due to differences in their ecological niches. Studies have provided support both for and against this hypothesis. One reason for this is the tendency for phylogenetic clustering between aliens and natives at broad spatial scales with overdispersion at fine scales. However, little is known about how the phylogenetic relatedness of alien species alters the phylogenetic structure of the communities they invade, and at which spatial scales effects may manifest. Here, we examine if invaded understorey plant communities, i.e. containing both native and alien taxa, are phylogenetically clustered or overdispersed, how relatedness changes with spatial scale and how aliens affect phylogenetic patterns in understorey communities. Methods Field surveys were conducted in dry forest understorey communities in south-east Australia at five spatial scales (1, 20, 500, 1500 and 4500 m2). Standardized effect sizes of two metrics were used to quantify phylogenetic relatedness between communities and their alien and native subcommunities, and to examine how phylogenetic patterns change with spatial scale: (i) mean pairwise distance and (ii) mean nearest taxon distance (MNTD). Important Findings Aliens were closely related to each other, and this relatedness tended to increase with scale. Native species and the full community exhibited either no clear pattern of relatedness with increasing spatial scale or were no different from random. At intermediate spatial scales (20–500 m2), the whole community tended towards random whereas the natives were strongly overdispersed and the alien subcommunity strongly clustered. This suggests that invasion by closely related aliens shifts community phylogenetic structure from overdispersed towards random. Aliens and natives were distantly related across spatial scales, supporting Darwin’s naturalization hypothesis, but only when phylogenetic distance was quantified as MNTD. Phylogenetic dissimilarity between aliens and natives increased with spatial scale, counter to expected patterns. Our findings suggest that the strong phylogenetic clustering of aliens is driven by human-mediated introductions involving closely related taxa that can establish and spread successfully. Unexpected scale-dependent patterns of phylogenetic relatedness may result from stochastic processes such as fire and dispersal events and suggest that competition and habitat filtering do not exclusively dominate phylogenetic relationships at fine and coarse spatial scales, respectively. Distinguishing between metrics that focus on different evolutionary depths is important, as different metrics can exhibit different scale-dependent patterns.

scholarly journals Assessment of floral colour signals at a community through the eyes of the birds and bees

2019 ◽  
Vol 222 (2) ◽  
pp. 648-650
Author(s):  
Adrian G. Dyer ◽  
Mani Shrestha
Keyword(s):  
Floral Colour ◽  
Colour Signals

scholarly journals Source range phylogenetic community structure can predict the outcome of avian introductions

2021 ◽  
Author(s):  
Brian S. Maitner ◽  
Daniel S Park ◽  
Brian J Enquist ◽  
Katrina M Dlugosch
Keyword(s):  
Propagule Pressure ◽  
Source Region ◽  
Predictive Ability ◽  
Phylogenetic Structure ◽  
Phylogenetic Relatedness ◽  
Phylogenetic Community Structure ◽  
Phylogenetic Hypotheses ◽  
Underlying Mechanisms ◽  
Consistent Support ◽  
Phylogenetic Models

Competing phylogenetic models have been proposed to explain the success of species introduced to other communities. Here, we present a study predicting the establishment success of birds introduced to Florida, Hawaii, and New Zealand using several alternative models, considering species' phylogenetic relatedness to source and recipient range taxa, propagule pressure, and traits. We find consistent support for the predictive ability of source region phylogenetic structure. However, we find that the effects of recipient region phylogenetic structure vary in sign and magnitude depending on inclusion of source region phylogenetic structure, delineation of the recipient species pool, and the use of phylogenetic correction in the models. We argue that tests of alternative phylogenetic hypotheses including the both source and recipient community phylogenetic structure, as well as important covariates such as propagule pressure, are likely to be critical for identifying general phylogenetic patterns in introduction success, predicting future invasions, and for stimulating further exploration of the underlying mechanisms of invasibility.

scholarly journals Visual Signalling in Plant-Animal Interactions

2021 ◽  
Author(s):  
◽  
Nik Fadzly N Rosely
Keyword(s):  
New Zealand ◽  
Geographical Location ◽  
Human Perception ◽  
Basic Research ◽  
Species Interaction ◽  
Visual Signals ◽  
Fruit Colour ◽  
Colour Perception ◽  
Visual Signalling ◽  
Colour Signals

<p>The process of visual signalling between plant and animals is often a combination of exciting discoveries and more often than not; highly controversial hypotheses. Plants and animals interact mutualistically and antagonistically creating a complex network of species relations to some extent suggesting a co evolutionary network. In this study, I investigate two basic research questions: the first is how plants utilize aposematic and cryptic colours? The second is how animals are affected by the colour signals broadcasted by plants? By using the avian eye model, I discover how visual signals/colours from plants are actually perceived, and the effects of these signals on birds (not human) perception. Aposematism and crypsis are common strategies utilized by animals, yet little evidence is known of such occurrences in plants. Aposematic and cryptic colours were evaluated by studying different colouration strategy through the ontogeny of two native heteroblastic New Zealand plants: Pseudopanax crassifolius and Elaeocarpus hookerianus. To determine the potential effect of colour signals on animals, I investigated an evolutionary theory of leaf colours constraining the conspicuousness of their fruit colour counterparts. Based on the available data, I also conducted a community level analysis about the effects of fruit colours and specific avian frugivores that might be attracted to them. Finally, I examined the fruit colour selection by a frugivorous seed dispersing insect; the Wellington Tree Weta (Hemideina crassidens). My result shows that aposematic and cryptic colours are successfully applied by plants to either warn or remain inconspicuous from browsing herbivores. The evidence I presented lends support to the Moa browsing hypothesis in relation to constraining the conspicuousness of their fruit colour counterparts. Based on the cryptic plant colourations. However, the same level of selective interaction could not be inferred for frugivore fruit colour selection based on avian vision. I demonstrated that leaf reflectance does not constrain/influence the conspicuousness of fruit colours. There was also no fruit colour diversity based on geographical location. Fruit colour alone is not sufficient to influence a specific frugivore assemblage. Other environmental factors and species interaction must be taken into account. Weta proved to possess colour vision capable of colour perception even in low light conditions. Weta also consistently selected naturally blue streaked and manipulated blue coloured fruits of Coprosma acerosa in a binary test. This supports the idea of weta co- evolving with fruit colours of certain divaricating plants in New Zealand. I suggest that the fruit colours of New Zealand are shaped by the combined selection pressure from birds, lizards/geckos and weta.</p>

scholarly journals An Ishihara-style test of animal colour vision

2018 ◽  
Author(s):  
Karen L. Cheney ◽  
Naomi F. Green ◽  
Alexander P. Vibert ◽  
Misha Vorobyev ◽  
N. Justin Marshall ◽  
...  
Keyword(s):  
Colour Vision ◽  
Weber Fraction ◽  
List Type ◽  
Colour Perception ◽  
Sensory Bias ◽  
Long Wavelength ◽  
Single Target ◽  
Normal Colour ◽  
Behavioural Tests ◽  
Colour Signals

AbstractColour vision mediates ecologically relevant tasks for many animals, such as mate choice, foraging and predator avoidance. However, our understanding of animal colour perception is largely derived from human psychophysics, even though animal visual systems differ from our own. Behavioural tests of non-human animals are required to understand how colour signals are perceived by them.Here we introduce a novel test of colour vision in animals inspired by the Ishihara colour charts, which are widely used to identify human colour deficiencies. These charts consist of dots that vary in colour, brightness and size, and are designed so that a numeral or letter is distinguishable from distractor dots for humans with normal colour vision. In our method, distractor dots have a fixed chromaticity (hue and saturation) but vary in luminance. Animals can be trained to find single target dots that differ from distractor dots in chromaticity. We provide Matlab code for creating these stimuli, which can be modified for use with different animals.We demonstrate the success of this method with triggerfìsh, Rhinecanthus aculeatus, and highlight behavioural parameters that can be measured, including success of finding the target dot, time to detect dot and error rate. Triggerfìsh quickly learnt to select target dots that differed from distractors dots regardless of the particular hue or saturation, and proved to use acute colour vision. We measured discrimination thresholds by testing the detection of target colours that were of increasing colour distances (ΔS) from distractor dots in different directions of colour space. At least for some colours, thresholds indicated better discrimination than expected from the Receptor Noise Limited (RNL) model assuming 5% Weber fraction for the long-wavelength cone.This methodology seems to be highly effective because it resembles natural foraging behavior for the triggerfìsh and may well be adaptable to a range of other animals, including mammals, birds, bees and freshwater fish. Other questions may be addressed using this methodology, including luminance thresholds, sensory bias, effects of sensory noise in detection tasks, colour categorization and saliency.

scholarly journals Red flowers differ in shades between pollination systems and across continents

2020 ◽  
Vol 126 (5) ◽  
pp. 837-848 ◽  
Author(s):  
Zhe Chen ◽  
Yang Niu ◽  
Chang-Qiu Liu ◽  
Hang Sun
Keyword(s):  
Large Scale ◽  
New World ◽  
Floral Colour ◽  
Chromatic Contrast ◽  
Colour Perception ◽  
Old World ◽  
Primary Signal ◽  
Achromatic Contrast ◽  
Pollination Systems ◽  
Plant Pollinator

Abstract Background and Aims Floral colour is a primary signal in plant–pollinator interactions. The association between red flowers and bird pollination is well known, explained by the ‘bee avoidance’ and ‘bird attraction’ hypotheses. Nevertheless, the relative importance of these two hypotheses has rarely been investigated on a large scale, even in terms of colour perception per se. Methods We collected reflectance spectra for 130 red flower species from different continents and ascertained their pollination systems. The spectra were analysed using colour vision models for bees and (three types of) birds, to estimate colour perception by these pollinators. The differences in colour conspicuousness (chromatic and achromatic contrast, purity) and in spectral properties between pollination systems and across continents were analysed. Key Results Compared with other floral colours, red flowers are very conspicuous to birds and much less conspicuous to bees. The red flowers pollinated by bees and by birds are more conspicuous to their respective pollinators. Compared with the bird flowers in the Old World, the New World ones are less conspicuous to bees and may be more conspicuous not only to violet-sensitive but also to ultraviolet-sensitive birds. These differences can be explained by the different properties of the secondary reflectance peak (SP). SP intensity is higher in red flowers pollinated by bees than those pollinated by birds (especially New World bird flowers). A transition from high SP to low SP in red flowers can induce chromatic contrast changes, with a greater effect on reducing attraction to bees than enhancing attraction to birds. Conclusions Shades of red flowers differ between pollination systems. Moreover, red bird flowers are more specialized in the New World than in the Old World. The evolution towards colour specialization is more likely to result in higher efficiency of bee avoidance than bird attraction

scholarly journals Parallel evolution of angiosperm colour signals: common evolutionary pressures linked to hymenopteran vision

2012 ◽  
Vol 279 (1742) ◽  
pp. 3606-3615 ◽  
Author(s):  
Adrian G. Dyer ◽  
Skye Boyd-Gerny ◽  
Stephen McLoughlin ◽  
Marcello G. P. Rosa ◽  
Vera Simonov ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Parallel Evolution ◽  
Flower Colour ◽  
Flowering Plants ◽  
Similar Distribution ◽  
Colour Discrimination ◽  
Colour Space ◽  
Angiosperm Species ◽  
Close Fit ◽  
Colour Signals

Flowering plants in Australia have been geographically isolated for more than 34 million years. In the Northern Hemisphere, previous work has revealed a close fit between the optimal discrimination capabilities of hymenopteran pollinators and the flower colours that have most frequently evolved. We collected spectral data from 111 Australian native flowers and tested signal appearance considering the colour discrimination capabilities of potentially important pollinators. The highest frequency of flower reflectance curves is consistent with data reported for the Northern Hemisphere. The subsequent mapping of Australian flower reflectances into a bee colour space reveals a very similar distribution of flower colour evolution to the Northern Hemisphere. Thus, flowering plants in Australia are likely to have independently evolved spectral signals that maximize colour discrimination by hymenoptera. Moreover, we found that the degree of variability in flower coloration for particular angiosperm species matched the range of reflectance colours that can only be discriminated by bees that have experienced differential conditioning. This observation suggests a requirement for plasticity in the nervous systems of pollinators to allow generalization of flowers of the same species while overcoming the possible presence of non-rewarding flower mimics.

Sign in / Sign up

Export Citation Format

Share Document