Constraints on plant signals and rewards to multiple mutualists?

Many plants invest substantial resources in signaling to and rewarding two kinds of ‘interguild’ mutualists, pollinators and seed dispersers. The signals and rewards are expressed via traits of flowers and fruits. Pollinators and seed dispersers could act in synergistic or antagonistic ways to influence selection on these traits. Here, we address the issue of whether plant species might be constrained in signaling to and rewarding multiple mutualists that provide different types of benefits to plants. Specifically, does investment in one type of mutualist limit investment in another? We examined the correlation between flower size and fruit size for 472 plant species spanning three regional floras. Our analyses made the assumption that structure size is related to plant investment in signals and/or rewards. We expect that a constraint due to interguild mutualisms would be evidenced by a negative correlation between flower and fruit size. Instead, we found significantly positive relationships between flower size and fruit size in all three regional floras. These relationships remained robust after correcting for plant evolutionary history using phylogenetically independent contrasts. These patterns may reflect synergies in selection by pollinators and seed dispersers, genetically-based or resource-based constraints on investment in reproductive tissues, and/or an underlying trade-off in structure size versus number.     

What weta want: colour preferences of a frugivorous insect

Plants use colours as signals to attract mutualists and repel antagonists. Fleshy-fruits are often conspicuously coloured to signal different types of information including fruit maturity and spatial location. Previous work on fruit colour selection focus on large diurnal vertebrates, yet fruit colours are perceived differently by frugivores with different types of visual systems. Here, we tested whether a nocturnal, frugivorous, seed-dispersing insect selects fruits based on their pigmentation and whether different lighting conditions affect fruit colour selection. We captured 20 Wellington tree weta (Hemideina crassidens) from a forest reserve on the North Island of New Zealand and brought them into laboratory conditions to test their fruit colour preferences. The fruits of Coprosma acerosa, a native shrub species that naturally produces translucent, blue-streaked fruits, were dyed either red or blue. Fruits were then offered to weta in a binary (y-maze) choice test in two light conditions, either at night during a full moon or under artificial light conditions in the lab. Weta preferred unmanipulated, naturally blue-streaked fruits and artificially-blue coloured fruits over those dyed red. Furthermore, their colour preferences were unaffected by light environment. Our results therefore suggest that weta can discriminate between colours (using colour vision) in both light and dark light environments. Their consistent preferences for colours other than red indicate that weta might be responsible for the unusual colours of fleshy-fruits in New Zealand.     

Why is the beautyberry so colourful? Evolution,biogeography, and diversification of fruit colours in Callicarpa (Lamiaceae)

Fruit colour is essential to seed dispersal, speciation, and biological diversity in global ecosystems. The relationship between fruit-colour variation and species diversification has long been of interest in evolutionary biology, but remains poorly understood at the genus level. Here, we used Callicarpa, a typical representative of pantropical angiosperm, to analyse whether fruit colours are correlated with biogeographic distribution, dispersal events, and diversification rate. We estimated a time-calibrated phylogeny for Callicarpa and reconstructed ancestral fruit colour. Utilizing phylogenetic methods, we estimated the major dispersal events across the phylogenetic tree and the most likely fruit colours related to each dispersal event, and tested whether the dispersal frequencies and distances of the four fruit colours between major biogeographical areas were equal. We then tested whether fruit colours are correlated with latitude, elevation, and diversification rate. Biogeographical reconstructions showed that Callicarpa originated in the East Asia and Southeast Asia during the Eocene (∼35.53 Ma) and diverse species diverged mainly in the Miocene and lasted into the Pleistocene. Large-scale dispersal events were significantly associated with violet-fruited lineages. Furthermore, different fruit colours were markedly correlated with different latitudes and elevations (e.g., violet fruits were correlated with higher latitudes and elevations; red fruits and black fruits with lower latitudes; white fruits with higher elevations). Notably, violet fruits were statistically associated with highest diversification rates, driving fruit colour variation among different regions globally. Our results contribute to further understanding why fruit colour is so variable at the genus level of angiosperms in different areas around the world.     

Nitrogen flows in Louisiana Gulf Coast salt marsh: Spatial considerations

Nitrogen flux data was synthesized in developing a nitrogen flow budget for a Louisiana Barataria BasinSpartina alterniflora salt marsh. Results demonstrate the importance of spatial consideration in developing a nitrogen budget for coastal marshes. Using a mass balance approach nitrogen inputs balanced nitrogen sinks or losses from a marsh soil-plant system with a specific rooting depth. However, per unit areas on a local scale, marshes serve as a large sink for nitrogen due to rapid accretion which removes 17.O g N m^–2yr^–1 through subsidence below the root zone. On a larger spatial scale (regional) it is shown that the marshes do not serve as a large nitrogen sink. The rapid marsh deterioration currently occurring in the rapidly subsiding marshes of the Mississippi River deltaic plain account for a net regional loss of 12.5 g N m^–2yr^–1. Thus, regionally the net sink is equivalent to only 5 g N m^–2yr^–1 as compared to 17.0 g N m^–2yr^–1 on a local scale.     

Proteases hold the key to an exclusive mutualism

Mutualisms, cooperative interactions between species, generally involve an economic exchange: species exchange commodities that are cheap for them to provide, for ones that cannot be obtained affordably or at all. But these associations can only succeed if effective partners can be enticed to interact. In some mutualisms, partners can actively seek one another out. However, plants, which use mutualists for a wide array of essential life history functions, do not have this option. Instead, natural selection has repeatedly favoured the evolution of rewards – nutritional substances (such as sugar‐rich nectar and fleshy fruit) with which plants attract certain organisms whose feeding activities can then be co‐opted for their own benefit. The trouble with rewards, however, is that they are usually also attractive to organisms that confer no benefits at all. Losing rewards to ‘exploiters’ makes a plant immediately less attractive to the mutualists it requires; if the reward cannot be renewed quickly (or at all), then mutualistic service is precluded entirely. Thus, it is in plants' interests to either restrict rewards to only the most beneficial partners or somehow punish or deter exploiters. Yet, at least in cases where the rewards are highly nutritious, we can expect counter‐selection for exploiter traits that permit them to skirt such control. How, then, can mutualisms persist? In this issue, Orona‐Tamayo et al. ( 2013 ) describe a remarkable adaptation that safeguards one particularly costly reward from nonmutualists. Their study helps to explain the evolutionary success of an iconic interaction and illuminates one way in which mutualism as a whole can persist in the face of exploitation.     

Using Stable Isotopes to Infer the Impacts of Habitat Change on the Diets and Vertical Stratification of Frugivorous Bats in Madagascar

Human-modified habitats are expanding rapidly; many tropical countries have highly fragmented and degraded forests. Preserving biodiversity in these areas involves protecting species–like frugivorous bats–that are important to forest regeneration. Fruit bats provide critical ecosystem services including seed dispersal, but studies of how their diets are affected by habitat change have often been rather localized. This study used stable isotope analyses (δ¹⁵N and δ¹³C measurement) to examine how two fruit bat species in Madagascar, Pteropus rufus (n = 138) and Eidolon dupreanum (n = 52) are impacted by habitat change across a large spatial scale. Limited data for Rousettus madagascariensis are also presented. Our results indicated that the three species had broadly overlapping diets. Differences in diet were nonetheless detectable between P. rufus and E. dupreanum, and these diets shifted when they co-occurred, suggesting resource partitioning across habitats and vertical strata within the canopy to avoid competition. Changes in diet were correlated with a decrease in forest cover, though at a larger spatial scale in P. rufus than in E. dupreanum. These results suggest fruit bat species exhibit differing responses to habitat change, highlight the threats fruit bats face from habitat change, and clarify the spatial scales at which conservation efforts could be implemented.     

A genome-wide scan study identifies a single nucleotide substitution in ASIP associated with white versus non-white coat-colour variation in sheep (Ovis aries)

In sheep, coat colour (and pattern) is one of the important traits of great biological, economic and social importance. However, the genetics of sheep coat colour has not yet been fully clarified. We conducted a genome-wide association study of sheep coat colours by genotyping 47 303 single-nucleotide polymorphisms (SNPs) in the Finnsheep population in Finland. We identified 35 SNPs associated with all the coat colours studied, which cover genomic regions encompassing three known pigmentation genes (TYRP1, ASIP and MITF) in sheep. Eighteen of these associations were confirmed in further tests between white versus non-white individuals, but none of the 35 associations were significant in the analysis of only non-white colours. Across the tests, the s66432.1 in ASIP showed significant association (P=4.2 × 10⁻¹¹ for all the colours; P=2.3 × 10⁻¹¹ for white versus non-white colours) with the variation in coat colours and strong linkage disequilibrium with other significant variants surrounding the ASIP gene. The signals detected around the ASIP gene were explained by differences in white versus non-white alleles. Further, a genome scan for selection for white coat pigmentation identified a strong and striking selection signal spanning ASIP. Our study identified the main candidate gene for the coat colour variation between white and non-white as ASIP, an autosomal gene that has been directly implicated in the pathway regulating melanogenesis. Together with ASIP, the two other newly identified genes (TYRP1 and MITF) in the Finnsheep, bordering associated SNPs, represent a new resource for enriching sheep coat-colour genetics and breeding.     

Variability,heritability and condition-dependence of the multidimensional male colour phenotype in a passerine bird

Elaborate ornamental traits are commonly assumed to be honest signals of individual quality, owing to the presumed costs involved in their production and/or maintenance. Such traits are often highly variable, possibly because of condition-dependence and/or high underlying genetic variation, and it has been suggested that their expression should be more sensitive to condition and/or more heritable than non-ornamental traits. Many bird species display colourful plumage with multiple distinct patches of different developmental origins, forming complex colour phenotypes. Despite this complexity, colourful ornaments are often studied in isolation, without comparison to suitable non-ornamental controls. Based on plumage reflectance data collected over 8 years, we assessed the signalling potential of the multidimensional male colour phenotype in a tropical bird: the purple-crowned fairy-wren Malurus coronatus. Specifically, we tested the predictions that the expression of putative ornamental colours (purple and black – the breeding colours – and blue) is (1) more variable, (2) more heritable and (3) more condition-dependent compared to year-round non-ornamental colours (buff-white and brown). Our results show that ornamental colours exhibit greater levels of variability, and some chromatic components of purple and blue colouration appear slightly heritable (h² = 0.19–0.30). However, contrary to predictions of heightened condition-dependence in ornaments, only brightness of the buff-white and brown colouration increased with male body condition, although brightness of the purple colouration was related to male age as expected. Despite partial support for predictions, the lack of consistent patterns illustrates the complexity of visual signals and highlights the need to study colour phenotypes in their entirety.Subject terms: Behavioural ecology, Evolutionary ecology, Ecological genetics, Quantitative trait, Sexual selection     

Colour preferences of flower-naive honeybees

Flower-naive honeybees Apis mellifera L. flying in an enclosure were tested for their colour preferences. Bees were rewarded once on an achromatic (grey, aluminium or hardboard), or on a chromatic (ultraviolet) disk. Since naive bees never alighted on colour stimuli alone, a scent was given in combination with colour. Their landings on twelve colour stimuli were recorded. Results after one reward (“first test”) were analysed separately from those obtained after few rewards (“late tests”).

1. After pre-training to achromatic signals, bees preferred, in the first test, bee-uv-blue and bee-green colours. With increasing experience, the original preference pattern persisted but the choice of bee-blue and bee-green colours increased.
2. Neither colour distance of the test stimuli to the background or to the pre-training signal, nor their intensity, nor their green contrast, accounted for the colour choice of bees. Choices reflected innate preferences and were only associated with stimulus hue.
3. Bees learned very quickly the pre-trained chromatic stimulus, the original colour preferences being thus erased.
4. Colour preferences were strongly correlated with flower colour and its associated nectar reward, as measured in 154 flower species.
5. Colour preferences also resemble the wavelength dependence of colour learning demonstrated in experienced bees.

     

非随机过程影响百山祖局域植物群落的物种组成

为探讨从区域到局域的变化过程中的主导影响机制,通过整理百山祖自然保护区的历次植物调查资料,并详细调查5 hm2的样地群落,对保护区整个区域和样地群落物种组成的差异和功能性状的组成差异进行了比较。结果表明,在区域种库和局域群落之间的物种组成差异明显,在区域和局域物种数量排名前10的科和属中只有5科和5属是共有的;相较于区域中的属,样地中温带分布的属明显增多,而热带分布的属较少。功能性状方面,与区域相比,样地中草本植物比例减少而木本植物比例增加;单叶植物比例增加,复叶植物比例下降;两性花比例下降,雌雄异株比例上升;肉质果比例上升,而干果比例下降。这些结果表明从区域到局域群落构建过程中生态位分化机制等非随机过程起着重要的作用。     

Evidence from the domestication of apple for the maintenance of autumn colours by coevolution

The adaptive value of autumn colours is still a puzzle for evolutionary biology. It has been suggested that autumn colours are a warning signal to insects that use the trees as a host. I show that aphids (Dysaphis plantaginea) avoid apple trees (Malus pumila) with red leaves in autumn and that their fitness in spring is lower on these trees, which suggests that red leaves are an honest signal of the quality of the tree as a host. Autumn colours are common in wild populations but not among cultivated apple varieties, which are no longer under natural selection against insects. I show that autumn colours remain only in the varieties that are very susceptible to the effects of a common insect-borne disease, fire blight, and therefore are more in need of avoiding insects. Moreover, varieties with red leaves have smaller fruits, which shows that they have been under less effective artificial selection. This suggests a possible trade off between fruit size, leaf colour and resistance to parasites. These results are consistent with the hypothesis that autumn colours are a warning signal to insects, but not with other hypotheses.     

Invasive ants disrupt frugivory by endemic island birds

Biological invasions can alter direct and indirect interactions between species, generating far-reaching changes in ecological networks that affect key ecological functions. We used model and real fruit assays to show that the invasion and formation of high-density supercolonies by the yellow crazy ant (YCA), Anoplolepis gracilipes, disrupt frugivory by endemic birds on Christmas Island, Indian Ocean. The overall handling rates of model fruits by birds were 2.2–2.4-fold lower in ant-invaded than in uninvaded rainforest, and pecking rates by two bird species declined by 2.6- and 4.5-fold, respectively. YCAs directly interfered with frugivory; their experimental exclusion from fruiting displays increased fruit handling threefold to sixfold, compounding indirect effects of ant invasion on resources and habitat structure that influence bird abundances and behaviours. This invasive ant, whose high densities are sustained through mutualism with introduced scale insects, rapidly decreases fruit handling by endemic island birds and may erode a key ecological function, seed dispersal. Because most other invasive ant species form expansive, high-density supercolonies that depend in part on association with hemipteran mutualists, the effects that we report here on avian frugivore–plant associations may emerge across their introduced ranges.     

Seasonal Changes in Colour: A Comparison of Structural,Melanin- and Carotenoid-Based Plumage Colours

Background

Plumage coloration is important for bird communication, most notably in sexual signalling. Colour is often considered a good quality indicator, and the expression of exaggerated colours may depend on individual condition during moult. After moult, plumage coloration has been deemed fixed due to the fact that feathers are dead structures. Still, many plumage colours change after moult, although whether this affects signalling has not been sufficiently assessed.

Methodology/Principal Findings

We studied changes in coloration after moult in four passerine birds (robin, Erithacus rubecula; blackbird, Turdus merula; blue tit, Cyanistes caeruleus; and great tit, Parus major) displaying various coloration types (melanin-, carotenoid-based and structural). Birds were caught regularly during three years to measure plumage reflectance. We used models of avian colour vision to derive two variables, one describing chromatic and the other achromatic variation over the year that can be compared in magnitude among different colour types. All studied plumage patches but one (yellow breast of the blue tit) showed significant chromatic changes over the year, although these were smaller than for a typical dynamic trait (bill colour). Overall, structural colours showed a reduction in relative reflectance at shorter wavelengths, carotenoid-based colours the opposite pattern, while no general pattern was found for melanin-based colours. Achromatic changes were also common, but there were no consistent patterns of change for the different types of colours.

Conclusions/Significance

Changes of plumage coloration independent of moult are probably widespread; they should be perceivable by birds and have the potential to affect colour signalling.     

Bilayer undulation dynamics in unilamellar phospholipid vesicles: Effect of temperature,cholesterol and trehalose

We report a combined dynamic light scattering (DLS) and neutron spin-echo (NSE) study on the local bilayer undulation dynamics of phospholipid vesicles composed of 1,2-dimyristoyl-glycero-3-phosphatidylcholine (DMPC) under the influence of temperature and the additives cholesterol and trehalose. The additives affect vesicle size and self-diffusion. Mechanical properties of the membrane and corresponding bilayer undulations are tuned by changing lipid headgroup or acyl chain properties through temperature or composition. On the local length scale, changes at the lipid headgroup influence the bilayer bending rigidity κ less than changes at the lipid acyl chain: We observe a bilayer softening around the main phase transition temperature T_m of the single lipid system, and stiffening when more cholesterol is added, in concordance with literature. Surprisingly, no effect on the mechanical properties of the vesicles is observed upon the addition of trehalose.     

The biogeography of fungal communities in wetland sediments along the Changjiang River and other sites in China

Whether fungal community structure depends more on historical factors or on contemporary factors is controversial. This study used culture-dependent and -independent (polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE)) methods to assess the influence of historical and contemporary factors on the distributions of fungi in the wetland sediments at 10 locations along the Changjiang River and at 10 other locations in China. The culture-dependent approach detected greater species diversity (177 operational taxonomic units (OTUs)) than PCR-DGGE analysis (145 OTUs), and the species in the genera of Penicillium (relative frequency=16.8%), Fusarium (15.4%), Aspergillus (7.6%), Trichoderma (5.8%) and Talaromyces (4.2%) were dominant. On the basis of DGGE data, fungal diversity along the Changjiang River increased from upstream to downstream; altitude explained 44.8% of this variation in diversity. And based on the data from all 20 locations, the fungal communities were geographically clustered into three groups: Southern China, Northern China and the Qinghai-Tibetan Plateau. Multivariate regression tree analysis for data from the 20 locations indicated that the fungal community was influenced primarily by location (which explained 61.8% of the variation at a large scale), followed by total potassium (9.4%) and total nitrogen (3.5%) at a local scale. These results are consistent with the concept that geographic distance is the dominant factor driving variation in fungal diversity at a regional scale (1000–4000 km), whereas environmental factors (total potassium and total nitrogen) explain variation in fungal diversity at a local scale (<1000 km).     

Do female tamarins use visual cues to detect fruit rewards more successfully than do males?

Primates are unique among eutherian mammals for possessing trichromatic colour vision. It is generally proposed that trichromacy evolved to aid detection of ripe fruits against mature foliage. However, while trichromacy is routine in all Old World monkeys and apes (the catarrhines), a cone opsin polymorphism in New World monkeys (the platyrrhines) results in foraging groups with mixed capacities for chromatic distinction. Although 50-66% of female platyrrhines are trichromatic, all males are dichromatic. Here, we test the hypothesis that trichromatic platyrrhines use visual cues to detect fruit rewards more successfully than do males. Specifically, we ask whether female emperor tamarins, Saguinus imperator imperator, and saddleback tamarins, S. fuscicollis weddelli, are the first members of their foraging group to locate food patches; and, furthermore, whether they are more successful than males in using colour, shape and size cues to discriminate between sham and reward feeding sites. Our results show that females and males do not differ in their ability to locate or discriminate between feeding sites. We conclude that trichromatic vision in female tamarins does not confer an advantage for detecting yellow fruit rewards against mature foliage. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.      

Quantitative imaging mass spectrometry of renal sulfatides: validation by classical mass spectrometric methods

Owing to its capability of discriminating subtle mass-altering structural differences such as double bonds or elongated acyl chains, MALDI-based imaging MS (IMS) has emerged as a powerful technique for analysis of lipid distribution in tissue at moderate spatial resolution of about 50 μm. However, it is still unknown if MS¹-signals and ion intensity images correlate with the corresponding apparent lipid concentrations. Analyzing renal sulfated glycosphingolipids, sulfatides, we validate for the first time IMS-signal identities using corresponding sulfatide-deficient kidneys. To evaluate the extent of signal quenching effects interfering with lipid quantification, we surgically dissected the three major renal regions (papillae, medulla, and cortex) and systematically compared MALDI IMS of renal sulfatides with quantitative analyses of corresponding lipid extracts by on-target MALDI TOF-MS and by ultra-performance LC-ESI-(triple-quadrupole)tandem MS. Our results demonstrate a generally strong correlation (R² > 0.9) between the local relative sulfatide signal intensity in MALDI IMS and absolute sulfatide quantities determined by the other two methods. However, high concentrations of sulfatides in the papillae and medulla result in an up to 4-fold signal suppression. In conclusion, our study suggests that MALDI IMS is useful for semi-quantitative dissection of relative local changes of sulfatides and possibly other lipids in tissue.     

In vivo hepatic lipid quantification using MRS at 7 Tesla in a mouse model of glycogen storage disease type 1a

The assessment of liver lipid content and composition is needed in preclinical research to investigate steatosis and steatosis-related disorders. The purpose of this study was to quantify in vivo hepatic fatty acid content and composition using a method based on short echo time proton magnetic resonance spectroscopy (MRS) at 7 Tesla. A mouse model of glycogen storage disease type 1a with inducible liver-specific deletion of the glucose-6-phosphatase gene (L-G6pc^−/−) mice and control mice were fed a standard diet or a high-fat/high-sucrose (HF/HS) diet for 9 months. In control mice, hepatic lipid content was found significantly higher with the HF/HS diet than with the standard diet. As expected, hepatic lipid content was already elevated in L-G6pc^−/− mice fed a standard diet compared with control mice. L-G6pc^−/− mice rapidly developed steatosis which was not modified by the HF/HS diet. On the standard diet, estimated amplitudes from olefinic protons were found significantly higher in L-G6pc^−/− mice compared with that in control mice. L-G6pc^−/− mice showed no noticeable polyunsaturation from diallylic protons. Total unsaturated fatty acid indexes measured by gas chromatography were in agreement with MRS measurements. These results showed the great potential of high magnetic field MRS to follow the diet impact and lipid alterations in mouse liver.     

Impact of the microalga Dunaliella salina (Dunal) Teodoresco culture and its β-carotene extract on the development of salt-stressed squash (Cucurbita pepo L. cv. Mabrouka)

Salinity is a major threat to crop production and global food security. Algae and their extracts containing bioactive compounds can enhance the salt tolerance of plants, including the salt-sensitive plants. The current study evaluated the efficacy of Dunaliella salina (Dunal) Teodoresco culture and/or its β-carotene extract in improving the salt tolerance of squash (Cucurbita pepo L. cv. Mabrouka). Amendment of C. pepo with D. salina culture and/or its β-carotene extract was more effective in alleviating the impact of moderate salinity imposed by seawater dilution of 2.5 dS m⁻¹ than either low (0.55 dS m⁻¹) or high (3.5 dS m⁻¹) salinity, with a comparable effect to that of salicylic acid (SA). Plants that received a combination of D. salina culture and its β-carotene extract showed significantly higher growth (total biomass, fruit productivity) and physiological attributes (photosynthetic pigments, nitrogen (N), phosphorus (P), and potassium (K⁺) contents) than those receiving either amendment alone, reaching up to 80–90% of the SA-treated plants at moderate salinity (2.5 dS m⁻¹). The combination could enhance the antioxidant activity of moderately salt-stressed C. pepo via increasing carotenoids and phenolics contents, suggesting that this combination could enhance the adaptation of C. pepo to the moderate salinity. The present study recommends using the blooms of D. salina and its β-carotene that is naturally secreted in situ in natural or synthetic open systems in improving the salt tolerance of C. pepo instead of using the expensive synthetic hormones.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12298-022-01176-6.