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Correlates of yield, fecundity and survival of a wild harvested Cyclopia intermedia (honeybush) population
Abstract
Cyclopia intermedia (honeybush) is a plant species endemic to the fynbos biome. Wild harvested populations are used commercially to produce tea. The species is a resprouter, regrowing from underground rootstock after fires, and as such resprouts once it has been cut. However, there is concern that premature cutting may be compromising rootstock recovery. We report on an initial 400 wild plants measured and monitored under different harvest regimes, including control plants. Plants were harvested once in 2018 and regrowth and survival monitored until 2021. Here, an allometric calculation is provided based on height and stem number to estimate the harvest yield. Plants in valleys or with high surrounding vegetation had the highest yield values and potential fecundity. After harvest, an increase in mortality was correlated with plant size, being higher for smaller plants, but after two years of drought high mortality was not explained by any harvesting category nor any of the site variables, suggesting drought results in high plant mortality regardless of harvest history. The study clarifies several speculative components of harvest method, demonstrates that a complete cut rather than half cut results in better potential yield, and that an ash admixture post-harvest had no measurable impact on regrowth.
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Flower colour differs dramatically between populations for some plant species; yet, we know little about what drives this variation. Such polymorphisms can be influenced by plant–pollinator interactions, but whether they are also influenced by pollinator‐mediated plant–plant interactions is unknown.
We test whether flower colour polymorphisms can arise through convergence (facilitation) or divergence (competition) of flower phenotypes resulting from plant–plant interactions mediated by the shared, and only, pollinator (orange‐breasted sunbird) of 10 Erica communities in South Africa.
Sunbird visitation rates to the less‐preferred Erica species in communities increased with colour similarity to the most‐visited species, suggesting that polymorphisms can be maintained by selection for colour convergence within communities, which promotes shared signals through rewarding mimicry (i.e. facilitation).
Colour similarity was lowest when risk of reproductive interference was greatest: that is, when reproductive morphology (stigma–anther distance) and flowering phenology was most similar, and when floral density differed greatly between species. This implies that polymorphisms can also be maintained by selection for colour divergence, since this promotes assortative pollinator foraging (i.e. competition).
Different populations of a species may experience opposite selective pressures, depending on their community context. This is the first evidence that a geographic mosaic of plant–plant pollination interactions could maintain colour polymorphisms in congeneric species sharing a single pollinator.
A free Plain Language Summary can be found within the Supporting Information of this article.
The evolution of floral traits in animal-pollinated plants involves the interaction between flowers as signal senders and pollinators as signal receivers. Flower colors are very diverse, effect pollinator attraction and flower foraging behavior, and are hypothesized to be shaped through pollinator-mediated selection. However, most of our current understanding of flower color evolution arises from variation between discrete color morphs and completed color shifts accompanying pollinator shifts, while evidence for pollinator-mediated selection on continuous variation in flower colors within populations is still scarce. In this review, we summarize experiments quantifying selection on continuous flower color variation in natural plant populations in the context of pollinator interactions. We found that evidence for significant pollinator-mediated selection is surprisingly limited among existing studies. We propose several possible explanations related to the complexity in the interaction between the colors of flowers and the sensory and cognitive abilities of pollinators as well as pollinator behavioral responses, on the one hand, and the distribution of variation in color phenotypes and fitness, on the other hand. We emphasize currently persisting weaknesses in experimental procedures, and provide some suggestions for how to improve methodology. In conclusion, we encourage future research to bring together plant and animal scientists to jointly forward our understanding of the mechanisms and circumstances of pollinator-mediated selection on flower color.
Variation in flower color due to transgenerational plasticity could stem directly from abiotic or biotic environmental conditions. Finding a link between biotic ecological interactions across generations and plasticity in flower color would indicate that transgenerational effects of ecological interactions, such as herbivory, might be involved in flower color evolution. We conducted controlled experiments across four generations of wild radish (Raphanus sativus, Brassicaceae) plants to explore whether flower color is influenced by herbivory, and to determine whether flower color is associated with transgenerational chromatin modifications. We found transgenerational effects of herbivory on flower color, partly related to chromatin modifications. Given the presence of herbivory in plant populations worldwide, our results are of broad significance and contribute to our understanding of flower color evolution.
Floral color shifts are thought to be one of the most common evolutionary transitions in plants, and pollinators are often proposed as important selective agents driving these transitions. However, shifts in flower color can also be related to neutral genetic processes or pleiotropy linked with selection via other biotic agents or abiotic factors. Here we ask whether abiotic factors or pollinators provide the best explanation for divergence in flower color among populations of the sundew Drosera cistiflora s.l. (Droseraceae). This species complex in the Greater Cape Floristic Region contains at least five distinctive floral color forms. Abiotic factors do not appear to play a significant role in color determination, as the forms are not specific to a single soil or vegetation type, sometimes co-occur in the same habitat, and maintain their color traits in common-garden and soil switching experiments. Instead, we found strong associations between flower color and the composition of pollinator assemblages which are dominated by hopliine scarab beetles. Pollinator assemblages show geographical structuring, both within and among color forms. This makes it difficult to dissect the roles of geography versus floral traits in explaining pollinator assemblages, but strong pollinator partitioning among color forms at sites where they are sympatric indicates that pollinators may select strongly on color. These results suggest that beetle pollinators are a significant factor in the evolution of D. cistiflora s.l. flower color.
Pollinator-mediated selection is expected to constrain floral color variation within plant populations. Here, we test for patterns of constraint on floral color variation in 38 bee- and/or hummingbird-pollinated plant species from Colorado, United States. We collected reflectance spectra for at least 15 individuals in each of 1–3 populations of each species (total 78 populations) and modeled perceived color variation in both bee and bird visual spaces. We hypothesized that bees would perceive less intraspecific color variation in bee-pollinated species (vs. bird-pollinated species), and reciprocally, birds would perceive less color variation in bird-pollinated species (vs. bee-pollinated species). In keeping with the higher dimensionality of the bird visual system, birds typically perceived much more color variation than bees, regardless of plant pollination system. Contrary to our hypothesis, bees perceived equal color variation within plant species from the two pollination systems, and birds perceived more color variation in species that they pollinate than in bee-pollinated species. We propose hypotheses to account for the results, including reduced long-wavelength sensitivity in bees (vs. birds), and the ideas that potential categorical color vision in birds and larger cognitive capacities of birds (vs. bees) reduces their potential discrimination against floral color variants in species that they pollinate, resulting in less stabilizing selection on color within bird-pollinated vs. bee-pollinated species.
Due to drastic changes in pollinators between native and invaded habitats, we might expect that pollinator-mediated selection on floral traits of alien plants differ from that in their native ranges. Here, through geometric morphometric tools and phenotypic selection analyses, we examined whether adaptation in flower shape and length occurred in Nicotiana glauca as a response to pollinator selection in contrasting pollination environments. We assessed populations of this plant species in the native range (South America), where plants depend on hummingbird pollination, and in two invaded areas, one where sunbirds act as pollinators (South Africa), and another where nectar feeding birds are absent and reproduction is entirely by autonomous self-pollination (Mallorca, Spain). Corolla length and shape varied significantly among pollination environments. Non-native sites were less variable and their range of variation fell within the native range of variation. Flower length in native populations and in a South African population matched the bill length of their respective pollinators. In contrast with the straight floral tubes in the native range, both non-native areas had significantly curved tubes. Curvature may improve the fit with the curved bills of sunbirds in South Africa (versus straight beaks of hummingbirds) and may enhance self-pollination in Mallorca, but this similarity between invaded areas may equally be due to drift and a shared colonization route. We found spatial variation in selection acting on corolla length but not on corolla shape. Overall, selection patterns were not consistent with floral trait variation. Although some results are consistent with both drift and selection, our study suggests that population divergence in flower shape and length is more likely the result of long-term diversifying pollinator-driven selection, which is difficult to detect by studying a single selection event.
The fynbos biome of South Africa is a biodiversity hotspot renowned for its very high plant species richness, endemic birds and the presence of the Cape mountain leopard (Panthera pardus). Biodiversity monitoring across a range of faunal taxa was conducted in mountain fynbos habitat in the context of determining prey availability for leopard, caracal (Caracal caracal) and African wildcat (Felis silvestris lybica). Studies were conducted, with the help of international volunteers recruited by Biosphere Expeditions, at Blue Hill Nature Reserve, a recently established protected area where land management changed from agriculture to biodiversity conservation in 2009. We examined prey availability at a spatial and temporal scale, using transects, Sherman traps and camera trap monitoring. Mammal density across all three measures suggests low mammal abundance and thus food availability for the predators in the fynbos ecosystem, which is known to have low carrying capacity. Camera trap photos from fixed monitoring points were used to examine the recovery of medium to large mammal species at the study site. Trends were positive for most common species (with the exception of African wildcat), with significant increases in standardised capture rate indices reported for caracal, greater kudu (Tragelaphus strepsiceros) and grey rhebok (Pelea capreolus). Transects to monitor wildlife also fed into a biome-wide survey to assess the status of the endangered Hottentot buttonquail (Turnix hottentottus), a bird endemic to the fynbos. We also conducted the first bat survey undertaken at Blue Hill Nature Reserve using Anabat Express recording devices and report the presence of five bat species. Opsomming Die fynbos bioom van Suid Afrika is wel bekend vir sy uitstekende biodiversiteit, met n groot aantal plante sorte, inheemse voels, en ook die Kaapse Berg Luiperd (Panthera pardus). Ons het biodiversiteit monitering onderneem oor n groot verskeidenheid fauna vanaf klein tot groot om te bepaal die beskikbaarheid van prooi vir luiperd, rooikat (Caracal caracal) en wildekat (Felis silvestris lybica). Hierdie studier was deur Biosphere Expeditions onderneem, wie vrywillige werkers gevind het om die monitering op die Blue Hill Natuur Reservaat en omgewings te implementeer. Blue Hill Natuur Reservaat is n nuwe beskermde gebied geïmplementeer in 2009 wat tevore n landbou gebied was. Ons het prooi beskikbaarheid ondersoek op n ruimtelik en temporale skaal met gebruik van transects, Sherman-traps en automatiese kameras. Die aantal soogdiere oor al drie van die statistieke was baie laag, wat beteken min beskikbaarheid van kos vir die roofdiere in die fynbos sisteem, al hoewel daar alreeds kennis daarvan is. Automaties kameras op konstante moniteering plekke was gebruik om te sien of daar herstel was van die aantal gemiddelde tot groot soogdiere nommers op Blue Hill. Oor die algemeen (behalwe wildekat) was die aantal fotos meer oor tyd, wat aandei herstel van die wild. Daar was beduidende verhogings vir rooikat, kudu (Tragelaphus strepsiceros) en vaal rhebok (Pelea capreolus). Transects om wild oor die hele bioom te moniteer om die populasie van die bedreigde, inheemse Kaapse kwarteltjie (Turnix hottentotus) te ondervind was ook deur die expedisie gehelp. Die expedisie het ook die eerste vlermuis opmeeting onderneem met gebruik van Anabat recording devices, wat vyf spesies gevind het.
Flower signals of bee- and bird-pollinated plants have converged via pollinator-mediated evolution, driven by the visual system of their respective pollinators. For bird flowers, sensory exclusion of less effective bees is also important and such exclusion is also mediated by floral morphological filters. Likewise, other systems based on pollination by red-sensitive insects are also associated with red flowers displaying lower short-wavelength secondary peaks of reflectance, which decreases detectability to animals that are less sensitive to red, such as bees. These flowers often also present long tubes. Here, we tested a generalization of the bee-avoidance hypothesis in order to assess if it holds only for bird flowers or for other non-bee pollination systems as well. For this, we compared flower contrasts and spectral purity in bee visual systems as proxies for conspicuousness among four kinds of pollination systems: bee-visited flowers, insect-visited flowers (including bees and other insects), non-bee insect flowers (flowers visited by red-sensitive insects such as flies, butterflies and beetles, but not bees), and bird-visited flowers. We also assessed the association between conspicuousness to bees and flower depth, used as a proxy for morphological exclusion of bees. Overall, flower conspicuousness to bees differed only between insect (all three groups) and bird flowers, due to lower visual signals for the latter. This suggests that bee sensory exclusion via color signals is exclusive to bird flowers, while non-bee insect flowers might use other sensory channels to exclude bees, such as olfactory signals. Visual bee avoidance might be a mechanism exclusive to plants pollinated by specific guilds of red-sensitive insects not well represented in our sample. We also found a negative association between flower conspicuousness to bees and flower depth, suggesting an interplay of morphological and spectral traits in discouraging bee visits. Our results support the bee-avoidance hypothesis exclusively for bird flowers and an overall association between lower visual signals to bees and long tubes.
Background
The current cultivation and plant breeding of Honeybush tea (produced from members of Cyclopia Vent.) do not consider the genetic diversity nor structuring of wild populations. Thus, wild populations may be at risk of genetic contamination if cultivated plants are grown in the same landscape. Here, we investigate the spatial distribution of genetic diversity within Cyclopia intermedia E. Mey. — this species is widespread and endemic in the Cape Floristic Region (CFR) and used in the production of Honeybush tea.
Methods
We applied High Resolution Melt analysis (HRM), with confirmation Sanger sequencing, to screen two non-coding chloroplast DNA regions (two fragments from the atpI-aptH intergenic spacer and one from the ndhA intron) in wild C. intermedia populations. A total of 156 individuals from 17 populations were analyzed for phylogeographic structuring. Statistical tests included analyses of molecular variance and isolation-by-distance, while relationships among haplotypes were ascertained using a statistical parsimony network.
Results
Populations were found to exhibit high levels of genetic structuring, with 62.8% of genetic variation partitioned within mountain ranges. An additional 9% of genetic variation was located amongst populations within mountains, suggesting limited seed exchange among neighboring populations. Despite this phylogeographic structuring, no isolation-by-distance was detected ( p > 0.05) as nucleotide variation among haplotypes did not increase linearly with geographic distance; this is not surprising given that the configuration of mountain ranges dictates available habitats and, we assume, seed dispersal kernels.
Conclusions
Our findings support concerns that the unmonitored redistribution of Cyclopia genetic material may pose a threat to the genetic diversity of wild populations, and ultimately the genetic resources within the species. We argue that ‘duty of care’ principles be used when cultivating Honeybush and that seed should not be translocated outside of the mountain range of origin. Secondarily, given the genetic uniqueness of wild populations, cultivated populations should occur at distance from wild populations that is sufficient to prevent unintended gene flow; however, further research is needed to assess gene flow within mountain ranges.
Aims
Bee-pollinated flowers are rarely red, presumably because bees (which lack red receptors) have difficulty detecting red targets. Although the response of bees to red colour has been investigated in lab experiments, most stimuli have been pure red, while the subtle diversity of red as perceived by humans (human-red) has received very limited attention. Here we test the hypothesis that ultraviolet (UV) reflected from human-red flowers enhances their attractiveness to bees, through increased chromatic contrast.
Methods
Using Onosma confertum (Boraginaceae), a plant with UV-reflecting red flowers that are pollinated by bumblebees, we investigated the effects of UV reflection on pollinator responses by conducting phenotypic manipulation experiments in the field. Colour preferences of flower-naïve bumblebees were also examined. Colour perception by bumblebees was estimated in terms of chromatic and achromatic contrast, based on two different colour perception models.
Important Findings
We found that both natural and flower-naïve bumblebees strongly preferred visiting UV-reflecting targets compared with UV-absorbing ones. Colour models show that the UV-reflecting flowers exhibit higher spectral purity and higher chromatic contrast against the foliage background, whereas they have similar achromatic contrast in terms of green receptor contrast. These results indicate that the component of UV reflection increases chromatic contrast in O. confertum, enhancing the visual attractiveness of these red flowers to bumblebees. We further infer that the secondary reflectance might be a necessary component in human-red flowers that are primarily pollinated by animals without red receptors, such as bees.
There is a wealth of research on the way interactions with pollinators shape flower traits. However, we have much more to learn about influences of the abiotic environment on flower colour.
We combine quantitative flower colour data for 339 species from a broad spatial range covering tropical, temperate, arid, montane and coastal environments from 9.25ºS to 43.75ºS with 11 environmental variables to test hypotheses about how macroecological patterns in flower colouration relate to biotic and abiotic conditions.
Both biotic community and abiotic conditions are important in explaining variation of flower colour traits on a broad scale. The diversity of pollinating insects and the plant community have the highest predictive power for flower colouration, followed by mean annual precipitation and solar radiation. On average, flower colours are more chromatic where there are fewer pollinators, solar radiation is high, precipitation and net primary production are low, and growing seasons are short, providing support for the hypothesis that higher chromatic contrast of flower colours may be related to stressful conditions.
To fully understand the ecology and evolution of flower colour, we should incorporate the broad selective context that plants experience into research, rather than focusing primarily on effects of plant–pollinator interactions.
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 the 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 (OW), the New World (NW) ones are less conspicuous to bees and maybe more conspicuous not only to VS-birds (violet-sensitive) but also to UVS-birds (ultraviolet-sensitive). 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 the NW 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 NW than in the OW. The fine evolution towards colour specialization is more likely to result in higher efficiency of bee avoidance than bird attraction.
Cyclopia is endemic to regions of the Cape Floristic Region across the Eastern and
Western Cape provinces of South Africa and is commonly known as honeybush. Honeybush has historically been used as an herbal tea, and has proven medicinal properties. Honeybush biomass and extracts are used in the functional foods and cosmetics sectors, both locally and overseas. The growing demand for honeybush calls for increased agricultural production and a shift away from the predominantly wild harvested supply.
Introduced plants become decoupled from their usual pollinators and by relying on resident pollinator species or other reproductive strategies become established in new areas, spread and, eventually, invade. Here, using breeding system experiments, we studied the reproductive biology of the bird-pollinated South American species Nicotiana glauca across native and non-native areas, both inside and outside the range of flower-visiting birds. In the native range, where the species is visited by hummingbirds, open cross-pollinated flowers set as many seeds and almost as many fruits as open pollination controls, suggesting that pollinators make a major contribution to reproductive success. In South Africa, the flowers were pollinated by sunbirds which, although less efficiently, also contributed to N. glauca reproduction, replacing hummingbirds. In contrast, in Mallorca, where nectar feeding birds are absent, fruit production in open cross-pollinated flowers was near zero, and significantly lower than in open pollination controls, suggesting that reproduction is almost entirely by autonomous self-pollination. Hand-pollination experiments showed that the species is self-compatible throughout its range. Pollinator exclusion experiment showed that N. glauca relies on self-pollination only in pollinator poor areas, where plants have a much higher capacity for autonomous self-pollination than elsewhere. A reduction in anther-stigma distance does not seem to account the higher self-pollination capacity in the non-native environment without pollinators. Despite probable evolutionary adaptation, and flexibility in pollinator association and mating system, seed production in the introduced range was somewhat pollen limited, suggesting that the mismatch between N. glauca and its novel pollination environment might retard invasion.
The NBA 2018 Synthesis report can be downloaded from the NBA website: http://nba.sanbi.org.za
Pollinator-mediated selection is expected to constrain floral color variation within plant populations, yet populations with high color variation (at least in human visual space) are common in nature. To explore this paradox, we collected floral reflectance spectra for 34 populations of 14 putatively bee-pollinated plant species of north-central New Mexico, USA, and translated them into three different animal visual spaces. We asked, (1) is intra-population variation in flower color constrained to be lower than the discrimination threshold of the putative dominant pollinators? And, (2) is perceived intrapopulation variation in flowers higher for non-pollinating animals than it is for the presumed dominant pollinator group? We found evidence consistent with some pollinator-imposed constraints on floral color in our species, with the majority (70.6%) of populations having > 95% of flower-flower or flower-centroid comparisons (where the centroid represents the mean phenotype) estimated to be visually indiscriminable to bees. We also found that perceived floral color variation was significantly greater for two non-pollinating groups-birds and humans-than for bees. Our results suggest that a large portion of human-perceived floral color variation within populations persists because it is effectively invisible to pollinators. In this scenario, human-perceived color may evolve neutrally (via drift) or via indirect selection on correlated characters such as herbivore-or drought-resistance, consistent with previous studies identifying non-pollinator agents of selection on flower color.
Biological coloration presents a canvas for the study of ecological and evolutionary processes. Enduring interest in colour‐based phenotypes has driven, and been driven by, improved techniques for quantifying colour patterns in ever‐more relevant ways, yet the need for flexible, open frameworks for data processing and analysis persists.
Here we introduce pavo 2 , the latest iteration of the r package pavo . This release represents the extensive refinement and expansion of existing methods, as well as a suite of new tools for the cohesive analysis of the spectral and (now) spatial structure of colour patterns and perception. At its core, the package retains a broad focus on (a) the organization and processing of spectral and spatial data, and tools for the alternating (b) visualization, and (c) analysis of data. Significantly, pavo 2 introduces image‐analysis capabilities, providing a cohesive workflow for the comprehensive analysis of colour patterns.
We demonstrate the utility of pavo with a brief example centred on mimicry in Heliconius butterflies. Drawing on visual modelling, adjacency, and boundary strength analyses, we show that the combined spectral (colour and luminance) and spatial (pattern element distribution and boundary salience) features of putative models and mimics are closely aligned.
pavo 2 offers a flexible and reproducible environment for the analysis of colour, with renewed potential to assist researchers in answering fundamental questions in sensory ecology and evolution.
Predictor effect displays, introduced in this article, visualize the response surface of complex regression models by averaging and conditioning, producing a sequence of 2D line graphs, one graph or set of graphs for each predictor in the regression problem. Partial residual plots visualize lack of fit, traditionally in relatively simple additive regression models. We combine partial residuals with effect displays to visualize both fit and lack of fit simultaneously in complex regression models, plotting residuals from a model around 2D slices of the fitted response surface. Employing fundamental results on partial residual plots along with examples for both real and contrived data, we discuss and illustrate both the strengths and limitations of the resulting graphs. The methods described in this paper are implemented in the effects package for R.
Colour signals are the main floral trait for plant–pollinator communication. Owing to visual specificities, flower visitors exert different selective pressures on flower colour signals of plant communities. Although they evolved to attract pollinators, matching their visual sensitivity and colour preferences, floral signals may also evolve to avoid less efficient pollinators and antagonistic flower visitors.
We evaluated evidence for the bee avoidance hypothesis in a Neotropical community pollinated mainly by bees and hummingbirds, the campo rupestre. We analysed flower reflectance spectra, compared colour variables of bee‐pollinated flowers (bee‐flowers; 244 species) and hummingbird‐pollinated flowers (hummingbird‐flowers; 39 species), and looked for evidence of bee sensorial exclusion in hummingbird‐flowers.
Flowers were equally contrasting for hummingbirds. Hummingbird‐flowers were less conspicuous to bees, reflecting mainly long wavelengths and avoiding red‐blind visitors. Bee‐flowers reflected more short wavelengths, were more conspicuous to bees (higher contrasts and spectral purity) than hummingbird‐flowers and displayed floral guides more frequently, favouring flower attractiveness, discrimination and handling by bees.
Along with no phylogenetic signal, the differences in colour signal strategies between bee‐ and hummingbird‐flowers are the first evidence of the bee avoidance hypothesis at a community level and reinforce the role of pollinators as a selective pressure driving flower colour diversity.
Biological invasions provide opportunities to study evolutionary processes occurring over contemporary timescales. To explore the speed and repeatability of adaptation, we examined the divergence of life‐history traits to climate, using latitude as a proxy, in the native North American and introduced European and Australian ranges of the annual plant Ambrosia artemisiifolia.
We explored niche changes following introductions using climate niche dynamic models. In a common garden, we examined trait divergence by growing seeds collected across three ranges with highly distinct demographic histories. Heterozygosity–fitness associations were used to explore the effect of invasion history on potential success. We accounted for nonadaptive population differentiation using 11 598 single nucleotide polymorphisms.
We revealed a centroid shift to warmer, wetter climates in the introduced ranges. We identified repeated latitudinal divergence in life‐history traits, with European and Australian populations positioned at either end of the native clines.
Our data indicate rapid and repeated adaptation to local climates despite the recent introductions and a bottleneck limiting genetic variation in Australia. Centroid shifts in the introduced ranges suggest adaptation to more productive environments, potentially contributing to trait divergence between the ranges.
Palm leaves represent one of the most important non-timber forest products in tropical and subtropical regions. Brahea aculeata is an endemic palm of northwest Mexico, whose leaves are intensively exploited for roof thatch and handcrafts. As part of a long-term defoliation experiment, we evaluated the effects of different leaf harvest on foliar and reproductive traits of adults and attributes of their progeny. We conducted a six-year manipulative experiment and applied three harvesting treatments to adults: high harvest, low harvest and no harvest (control). We recorded leaf production and size, flower and fruit production, seed germination and seedling growth. We also explored trade-offs among foliar and reproductive traits.
Harvested palms exhibited drastically reduced reproductive activity, producing fewer flowers and fruits (up to 80 and 90% fewer than unharvested palms). However, individuals in both harvest treatments had larger leaves and increased leaf production rates, compared to control palms. For harvested palms, we registered first a slight increase in leaf traits and a decline in reproductive attributes. These traits showed a gradual reduction and for six period attained very low proportional values compared to control palms (~0.10), however individuals in the harvested treatments maintained the greatest leaf lengths and leaf production rates. Seed germination and seedling growth rates of progeny from harvested palms were significantly lower than control palms, with seeds from the high harvest treatment having the lowest seed production and germination rates. Relationships among leaf (size/production) and reproductive traits (flower/fruit production) were positive during the fourth year, but showed negative relationships for the fifth year suggesting a trade-off between reproduction and growth functions. Leaf harvesting in B. aculeata seems to alter patterns of resource allocation away from reproduction as reflected in a decrease in the probability of reproduction, seed number, germination, and vigor, causing a strong decrease in the reproductive success of this species. Results showed that the consequences of long-term leaf harvest not only affect harvested individuals, but also the fitness and vigor of progeny. This type of long-term studies is essential to understand the population dynamics of non-timber forest products and helps inform sustainable harvesting programs considering intensity, frequencies and periods for recovery from defoliation. Also results may help to explain how intensive and non-planned management schemes may negatively affect vital rates and long-term dynamics of populations from non-timber forest products and other components of the ecosystem.
A decomposition experiment of Populus purdomii litter, a commonly used afforestation species in the Qinling Mountains, China, was conducted. Water extracts of five conifer litters were used to treat P. purdomii litter and its soil. The P. purdomii litter was incubated at room temperature (20–25 °C) and constant soil moisture for 6 months. During the decomposition period, the dynamics of litter mass and nutrient contents were detected to investigate the impacts of plant secondary metabolites. The results indicate that litter extracts of Pinus tabuliformis, Platycladus orientalis, Pinus armandii and Larix principis-rupprechtii significantly inhibited the overall nutrient release of P. purdomii litter, while the last three types of litter extracts simultaneously inhibited its decomposition. Conversely, the litter extracts of Picea asperata significantly accelerated the overall nutrient release of P. purdomii. Generally, most of the conifer species, whose litter released terpenoids, phenolics, steroids, and aliphatic acids, will inhibit the decomposition and/or nutrient release from P. purdomii litter. Their negative effects on the decomposers and soil enzymatic activities indicates that planting diversity should be lower when mixed planted with P. purdomii. © 2018, Northeast Forestry University and Springer-Verlag GmbH Germany, part of Springer Nature.
Color in nature presents a striking dimension of variation, though understanding its function and evolution largely depends on our ability to capture the perspective of relevant viewers. This goal has been radically advanced by the development and widespread adoption of color spaces, which allow for the viewer-subjective estimation of color appearance. Most studies of color in camouflage, aposematism, sexual selection, and other signaling contexts draw on these models, with the shared analytical objective of estimating how similar (or dissimilar) color samples are to a given viewer. We summarize popular approaches for estimating the separation of samples in color space and use a simulation-based approach to test their efficacy with common data structures. We show that these methods largely fail to estimate the separation of color samples by neglecting 1) the statistical distribution and within-group variation of the data and/or 2) the discriminability of groups relative to the observer's visual capabilities. Instead, we formalize the 2 questions that must be answered to establish both the statistical presence and theoretical magnitude of color differences, and propose a 2-step, permutationbased approach that achieves this goal. Unlike previous methods, our suggested approach accounts for the multidimensional nature of visual model data and is robust against common color-data features such as heterogeneity and outliers. We demonstrate the pitfalls of current methods and the flexibility of our suggested framework using an example from the literature, with recommendations for future inquiry.
Our understanding of how climate influences species distributions and our ability to assess the risk of introduced species depend on the assumption that species' climatic niches remain stable across space and time. While niche shifts have been detected in individual invasive species, one assessment of ~50 plants in Europe and North America concluded that niche shifts were rare, while another concluded the opposite. These contradictory findings, limited in species number and geographic scope, leave open a need to understand how often introduced species experience niche shifts and whether niche shifts can be predicted. We found evidence of climatic niche shifts in 65-100% of 815 terrestrial plant species introduced across five continents, depending on how niche shifts were measured. Individual species responses were idiosyncratic, but we generally saw that niche shifts reflected changes in climate availability at the continent scale and were largest in long-lived and cultivated species. Smaller intercontinental niche shifts occurred within species' native ranges. Overall, the climatic niches of terrestrial plant species were not conserved as they crossed continents. These results have major consequences for applying environmental niche models to assess the risk of invasive species and for predicting species responses to climate change. Our findings challenge the tenet that species' niches are conserved aspects of their ecology.
Many endemic Cape plant species are commercially valuable, but information required to manage the resources is often lacking. Here I consider the potential genetic risk that the transition to cultivation may pose for Cape endemic plants and use honeybush – which is based on the members of the Cape endemic genus Cyclopia – as an example. The honeybush industry is expanding, in part driven by the transition from wild harvesting to cultivation. This change offers substantial environmental and economic benefits but may pose risks to wild populations through genetic contamination. I discuss (1) the importance of maintaining genetic diversity and structure of wild populations, (2) the levels of genetic structuring we might expect within the members of the genus Cyclopia, (3) the potential threats to genetic diversity, (4) suggestions for minimising genetic contamination of wild populations by cultivated plantations, and (5) why these issues may be important for the honeybush industry.
One of the frequent questions by users of the mixed model function lmer of the lme4 package has been: How can I get p values for the F and t tests for objects returned by lmer? The lmerTest package extends the 'lmerMod' class of the lme4 package, by overloading the anova and summary functions by providing p values for tests for fixed effects. We have implemented the Satterthwaite's method for approximating degrees of freedom for the t and F tests. We have also implemented the construction of Type I - III ANOVA tables. Furthermore, one may also obtain the summary as well as the anova table using the Kenward-Roger approximation for denominator degrees of freedom (based on the KRmodcomp function from the pbkrtest package). Some other convenient mixed model analysis tools such as a step method, that performs backward elimination of nonsignificant effects - both random and fixed, calculation of population means and multiple comparison tests together with plot facilities are provided by the package as well.
The ability of a woody plant to coppice and remain vigorous largely depends on the severity of disturbances, resource availability and the mobilisation of stored reserves. There is limited information about the role played by resource limitation on the recovery of cut trees. This study investigated the effects of water and nutrient supplementation on coppice growth responses of resprouting cut trees in a semi-arid savannah in South Africa. Cut trees were exposed to different levels of water and nutrient (nitrogen and phosphorus) supplementation over a period of 2 years in a factorial experimental design. We hypothesised that adding water and nutrients would result in an increased coppice growth response and replenishment of stored structural reserves. Adding water and nutrients significantly increased shoot diameter, shoot length and resprouting ratio for the initial 12 months after cutting but not stored structural reserves. Such a response pattern suggests that the initial growth of resprouting shoots may be strongly resource-limited, while resources are concentrated on supporting fewer resprouting shoots compared to a higher number.
Conservation implications: If practicing rotational tree harvesting, trees resprouting in resource-poor locations need a longer resting period to recover stored reserves and to also recover lost height after cutting.
A higher frequency of natural selection is expected in populations of organisms with shorter generation times. In fire-prone ecosystems, populations of seeder plants behave as functionally semelparous populations, with short generation times compared to populations of resprouter plants, which are truly iteroparous. Therefore, a stronger signature of natural selection should be detected in seeder populations, favoured by their shorter generation times and higher rates of population turnover. Here we test this idea in Erica coccinea from the Cape Floristic Region, which is dimorphic for post-fire regeneration mode. We measured three floral traits supposedly subject to natural selection in seeder and resprouter populations. We then compared phenotypic trait variation with neutral genetic variation in each group of populations using PST–FST comparisons to detect signatures of natural selection in seeders and resprouters. We found a strong signature of selection in seeder populations, but not in resprouters. Furthermore, anthers of seeders were more exserted (and larger) than those of resprouters. These differences were maintained at sites where seeders and resprouters co-occurred, suggesting that phenotypic plasticity or adaptation to different growth environments are unlikely explanations for trait variation. These results provide empirical support for the hypothesis that the genetic signature of natural selection is certainly more intense in seeder than in resprouter populations, favoured by their comparatively faster generation turnovers. Increased frequency of natural selection would increase differentiation among populations, thus promoting speciation in pyrophytic seeder lineages of the Cape flora.
Despite the strong relationship between insect vision and the spectral properties of flowers, the visual system has been studied in detail only in few insect pollinator species. For instance, wavelength discrimination thresholds have been determined in two species only: the honeybee (Apis mellifera) and the butterfly Papilio xuthus. Here, we present the wavelength discrimination thresholds (Δλ) for the hawkmoth Macroglossum stellatarum. We compare the data with those found for the honeybee, the butterfly P. xuthus and the predictions of a colour discrimination model. After training moths to feed from a rewarded disk illuminated with a monochromatic light, we tested them in a dual choice situation, in which they had to choose between the light of the training wavelength and a novel unrewarded wavelength. To characterise the Δλ function, we decreased the difference between wavelengths in subsequent tests. We also varied the light intensity to test its effect on the discrimination capacity. In agreement with the predictions of the model, we found two expected minima of discrimination where photoreceptor sensitivities overlap, as well as a minor third unpredicted minimum around the peak of the blue photoreceptor. M. stellatarum is capable to discriminate lights with a wavelength difference of 1 to 2 nm. These discrimination minima are similar to those found for the tetrachromatic P. xuthus, and are better than those of the honeybee. The moth is also capable to use achromatic information to discriminate between lights of long wavelengths.
Lignotubers are swollen woody structures located at the root-shoot transition zone and contain numerous dormant buds and starch reserves. This structure enables the plant to resprout prolifically after severe disturbances that remove the aboveground biomass. These are considered adaptive traits in ecosystems with highly frequent and severe disturbances—such as fire-prone ecosystems. In this paper, we aim to contribute to the knowledge of lignotubers in the Mediterranean basin and highlight the evolutionary implications. We first summarise existing knowledge on lignotuber species in the Mediterranean basin. We then provide a detailed morpho-anatomical description of early lignotubers in two common woody species (Arbutus unedo L. and Phillyrea angustifolia L.). Finally, we compare our anatomical results with those obtained in studies conducted with other lignotuberous species from different Mediterranean regions. Lignotubers were verified in 14 species in the Mediterranean basin; all being from lineages with origins dating to the Tertiary and thus pre-dating the Mediterranean climate. In A. unedo and P. angustifolia, lignotubers are macroscopically discernible in 4- and 2-year-old saplings, respectively. In these two species, the lignotubers have numerous buds protected by hypertrophied scales, and have a contorted xylem containing abundant starch. Our results challenge the traditional idea that pre-Mediterranean lineages suffered evolutionary inertia; instead, lignotuberous species may be considered examples of plants that adapted to the increased fire activity that occurred throughout the Tertiary and Quaternary. We also highlight the use of morpho-anatomical traits to unambiguously distinguish between lignotuberous and non-lignotuberous resprouting species.
The recognition that animals sense the world in a different way than we do has unlocked important lines of research in ecology and evolutionary biology. In practice, the subjective study of natural stimuli has been permitted by perceptual spaces, which are graphical models of how stimuli are perceived by a given animal. Because colour vision is arguably the best-known sensory modality in most animals, a diversity of colour spaces are now available to visual ecologists, ranging from generalist and basic models allowing rough but robust predictions on colour perception, to species-specific, more complex models giving accurate but context-dependent predictions. Selecting among these models is most often influenced by historical contingencies that have associated models to specific questions and organisms; however, these associations are not always optimal. The aim of this review is to provide visual ecologists with a critical perspective on how models of colour space are built, how well they perform and where their main limitations are with regard to their most frequent uses in ecology and evolutionary biology. We propose a classification of models based on their complexity, defined as whether and how they model the mechanisms of chromatic adaptation and receptor opponency, the nonlinear association between the stimulus and its perception, and whether or not models have been fitted to experimental data. Then, we review the effect of modelling these mechanisms on predictions of colour detection and discrimination, colour conspicuousness, colour diversity and diversification, and for comparing the perception of colour traits between distinct perceivers. While a few rules emerge (e.g. opponent log-linear models should be preferred when analysing very distinct colours), in general model parameters still have poorly known effects. Colour spaces have nonetheless permitted significant advances in ecology and evolutionary biology, and more progress is expected if ecologists compare results between models and perform behavioural experiments more routinely. Such an approach would further contribute to a better understanding of colour vision and its links to the behavioural ecology of animals. While visual ecology is essentially a transfer of knowledge from visual sciences to evolutionary ecology, we hope that the discipline will benefit both fields more evenly in the future.
Floral colour mediates plant–pollinator interactions by often signalling floral resources. In this sense, hummingbird‐pollinated flowers are frequently red‐coloured, and there are two tentative hypotheses to explain this pattern: 1. hummingbirds are attracted to red due its easier detection and 2. bees are sensorially excluded from red flowers. The second hypothesis is based on bees’ red colour blindness, which lead them to be less frequent and less important than hummingbirds as pollinators of red‐reflecting flowers.
Here, we untangled the role of different flower traits mediating plant–pollinator interactions and empirically tested the above hypotheses. We chose C ostus arabicus due to its synchronopatric white‐ and pink‐flowered individuals and its bee and hummingbird pollination system. Although pink flowers are not totally achromatic as pure red ones, they show an achromaticity degree that could drive bee exclusion. Specifically, we tested whether differences on red reflectance work attracting hummingbirds or excluding bees and the consequent implications for the plant's reproduction.
Flower colour morphs of C. arabicus do differ neither in morphology nor in nectar sugar content. Moreover, white and pink flowers can be discriminated by the bees’ and hummingbirds’ colour vision system. Both groups are able to discriminate the red colour variation morph on the flower petals, the white flowers being more easily detected by bees and the pink flowers by hummingbirds. Bees preferentially visited the white flowers, whereas hummingbirds visited both colours at the same rate – both patterns corroborating the second hypothesis.
Pollen loads deposited on stigmas did not differ between flower colour morphs, indicating that bees and hummingbirds play a similar role in the overall pollen deposition. However, bees are more likely to self‐pollinate than hummingbirds. Self‐pollination limits C. arabicus reproduction, and red‐reflecting flowers may be better pollinated by discouraging bee visitation. Therefore, the intraspecific colour variation is driving flowers to show colour‐related different levels of generalization.
Our results support the ‘bee avoidance’ rather than the ‘hummingbird preference’ hypothesis. Sensory exclusion of bees seems to be the pressure for red‐reflecting flowers evolution, driving specialization in hummingbird‐pollinated flowers due to the costs of bee pollination on plant reproduction.
Flower color variation among plant populations might reflect adaptation to local conditions such as the interacting animal community. In the northwest Iberian Peninsula, flower color of Gentiana lutea varies longitudinally among populations, ranging from orange to yellow. We explored whether flower color is locally adapted and the role of pollinators and seed predators as agents of selection by analyzing the influence of flower color on (i) pollinator visitation rate and (ii) escape from seed predation and (iii) by testing whether differences in pollinator communities correlate with flower color variation across populations. Finally, (iv) we investigated whether variation in selective pressures explains flower color variation among 12 G. lutea populations. Flower color influenced pollinator visits and differences in flower color among populations were related to variation in pollinator communities. Selective pressures on flower color vary among populations and explain part of flower color differences among populations of G. lutea. We conclude that flower color in G. lutea is locally adapted and that pollinators play a role in this adaptation.
The formal honeybush tea industry in South Africa is relatively new, and has tremendous growth potential. However, as with other cultivated crops, production and yield can be adversely affected by fungal diseases. A number of Diaporthe species are recognised as causal agents of plant disease symptoms such as dieback, twig blight and branch cankers. For the past few years, such symptoms have been observed on Cyclopia (honeybush) species in cultivated fields located in two districts in the Western Cape province of South Africa. In this study, Diaporthe species associated with honeybush dieback symptoms were identified. One hundred and fifteen isolates recovered from C. genistoides, C. longifolia and C. subternata exhibited cultural characteristics typical of Diaporthe. Representative isolates of the morphological groups were identified to species level, based on the sequence analysis of the rDNA internal transcribed spacer (ITS) region, β-tubulin (tub2), histone 3 (his3) and the translation elongation factor 1-alpha (tef1-α) genes. Seven Diaporthe species were found to be associated with honeybush, namely, D. aspalathi, D. cynaroidis, D. foeniculina, D. heterophyllae, D. inconspicua, D. nebulae and D. sojae. The isolates of each species used in the pathogenicity tests were all pathogenic on C. subternata. Diaporthe heterophyllae was the most virulent species, causing the longest internal lesions as well as typical dieback symptoms. Diaporthe nebulae was moderately virulent in comparison to D. heterophyllae, while the other species were significantly less virulent.
Mesic grasslands in South Africa (> 650 mm a À 1 MAP) are rich in herbaceous forbs, which outnumber grass species by more than 5 to 1. Many of these forbs are geophytes with underground storage units (USOs), such as thickened rootstocks, rhizomes, bulbs, or corms, that provide resources (non-structural carbohydrates, minerals, and water) enabling them to resprout after dry, frosty winters, and fire. However, despite their extensive biomass and reserves ostensibly protected underground, mesic grassland geophytes can be severely depleted or extirpated by chronic trampling and grazing of their aerial parts by livestock. This study examined a possible explanation for the demise of grassland geophytes in overgrazed grassland by investigating , in a pot trial, whether the growth of a geophyte and the size of its USOs are negatively affected by simulated green leaf loss. In a 2 £ 2 factorial (clipped vs. unclipped x spring regrowth in the dark vs. light), five replicate plants of Hypoxis hemerocallidea, a common mesic grassland geophyte that resprouts from a corm, were subject to six severe (clipped to 80 mm) defoliations during the growing season and regrown in spring under full or restricted light to measure stored reserve contribution to regrowth. Defoliated plants were resilient to defoliation during the growing season, matching the total biomass production of unclipped plants, though cutting reduced the number of leaves by :60% and flowers by almost 85%. Spring regrowth on stored reserves equalled that from reserves plus concurrent photosynthesis, indicating the value of USOs for regrowth. However, there was a marked carry-over effect of previous season defoliation, resulting in a one-third reduction in shoot growth and 40% fewer inflorescence in spring. Crucially, corm mass was more than halved by clipping, which resulted in lower spring biomass and inflorescence production. It was concluded that buried stored reserves are not protected from recurrent defoliation and mechanical damage to aerial plant parts and that continued diminishment of USOs under chronic disturbance by overgrazing or frequent mowing would weaken and likely eventually kill plants, reducing overall forb species richness. Lenient management by infrequent summer mowing or grazing at moderate stocking rates combined with periodic rota-tional full season resting and dormant-season burning is recommend to maintain the USOs and vigour of grassland geophytes in mesic grassland.
Natural selection acts on phenotypic trait variation. Understanding the mechanisms that create and maintain trait variation is fundamental to understanding the breadth of diversity seen on Earth. Flower colour is among the most conspicuous and highly diverse traits in nature. Most flowering plant populations have uniform floral colours, but a minority exhibit within-population colour variation, either discrete (polymorphic) or continuous. Colour variation is commonly maintained by balancing selection through multiple pollinators, opposing selection regimes, or fluctuating selection. Variation can also be maintained by heterozygote advantage or frequency-dependent selection. Neutral processes, or a lack of selection, may maintain variation, although this remains largely untested. We suggest several prospective research directions that may provide insight into the evolutionary drivers of trait variation.
This paper reports the dissimilar floral spectral reflection of invasive and non-invasive angiosperms. Hyper spectral floral reflectance of 22 non-invasive and 8 invasive, co-habiting and co-flowering angiosperm from Trivandrum, India were measured from 350 to 700 nm. using hand-held spectroradiometer. The ultraviolet, blue and green portions of the electromagnetic spectrum was converted to corresponding photoreceptor excitation values, and insect pollinator (bee) perceived colours respectively. The colour distance between invasive and non-invasive flowers was calculated. Spectral similarity and principal component analysis carried out on photoreceptor excitation values in the ultraviolet, blue and green region reveal the markedly different floral colour perception rendered by invasive species from that of their co-flowering, non-invasive counterparts. Floral spectral reflection in the ultraviolet and blue region was the least similar.
Floral traits are hypothesized to evolve primarily in response to selection by pollinators. However, selection can also be mediated by other environmental factors. To understand the relative importance of pollinator‐mediated selection and its variation among trait and pollinator types, we analyzed directional selection gradients on floral traits from experiments that manipulated the environment to identify agents of selection. Pollinator‐mediated selection was stronger than selection by other biotic factors (e.g. herbivores), but similar in strength to selection by abiotic factors (e.g. soil water), providing partial support for the hypothesis that floral traits evolve primarily in response to pollinators. Pollinator‐mediated selection was stronger on pollination efficiency traits than on other trait types, as expected if efficiency traits affect fitness via interactions with pollinators, but other trait types also affect fitness via other environmental factors. In addition to varying among trait types, pollinator‐mediated selection varied among pollinator taxa: selection was stronger when bees, long‐tongued flies, or birds were the primary visitors than when the primary visitors were Lepidoptera or multiple animal taxa. Finally, reducing pollinator access to flowers had a relatively small effect on selection on floral traits, suggesting that anthropogenic declines in pollinator populations would initially have modest effects on floral evolution.
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We used locally-sourced and other relevant information to value ecosystem services provided by South Africa's terrestrial, freshwater and estuarine habitats. Our preliminary estimates suggest that these are worth at least R275 billion per annum to South Africans. Notwithstanding benefits to the rest of the world, natural systems provide a major source of direct income to poor households, and generate significant value in the economy through tourism and property markets, as well as providing considerable non-market benefits. Higher values correspond both to areas of higher biomass, which have higher capacity to supply ecosystem services, and areas of higher population densities, which generate demand as well as threats. The value of regulating services is higher for natural systems closer to population centres. Amenity values are highest in cities and protected areas, with the fragmented green open space areas within cities have among the highest values per ha. Even if the gaps are taken into account, our estimates are far lower than estimates based on average global values, but are likely to be more accurate, relevant and tractable to policymakers. Nevertheless, some services have large global values, the recognition of which is important in developing strategies for financing biodiversity conservation.
Inflorescences and cones of serotinous (canopy-stored seed) Proteaceae are extensively harvested by the wildflower industry from natural stands in fynbos of the Agulhas Plain, South Africa. This study investigated the impacts of harvesting on seed bank size and seed set of Protea susannae Phill., P. obtusifolia Beuk ex Meisn., Leucadendron coniferum (L.) Meisn. and L. meridianum I. Williams. Harvesting of inflorescences or cones by the stem-cutting method reduced the following season's infructescence (called ‘cones') production in all species except P. susannae. Remaining current year cones of the harvested Protea spp. had greater insect predation levels, and unaltered or lower seed set, than those of unharvested plants. The seed set findings are not consistent with the hypothesis that seed numbers are nutrient-limited, since inflorescence harvesting represents a sink removal, and increased nutrients remaining in the plant would be available for increased seed set. Since repeated annual harvesting of 70% of current year inflorescences or fruit was estimated to result in severe seed bank depletion, it is suggested that lower levels of harvesting (not more than 50% of current inflorescences or cones) be performed in alternate years.
Invasive non‐native plants form interactions with native species and have the potential to cause direct and indirect impacts on those species, as well as the functioning of invaded ecosystems.
Many entomophilous invasive plants form interactions with resident pollinators; sometimes, these interactions are necessary for the reproductive success of the invader. However, the direct role native pollinators play in plant invasion is not well understood and varies according to invasive plant traits, including breeding system and pollination syndrome.
The majority of studies addressing impacts on plant–pollinator mutualisms have focussed on the indirect impacts of plant invasion for native plant pollination. Fewer studies have focussed on the direct effects of invasive plants on native flower visitors.
Impacts of invasive plants on native pollinators can occur at a range of scales: from the individual flower visitors (in terms of nutrition, health and fitness), to populations (size, density and growth rates), communities (richness, diversity and composition) and community‐level interactions (insect–flower interaction networks). Most research to date has focussed on community‐level impacts, with almost nothing known about the effects of invaders on native flower visitor individuals or populations.
Invasive plant traits, including reward quantity and quality, spatial and temporal availability and accessibility, modulate effects on native flower visitors, and thus, different plant species have different impacts. Similarly, flower visitors do not all respond in the same way to invasive plants. Thus, generalizations are difficult to make, but understanding impacts at the individual and population level for different visitor taxa is key to explaining community‐level impacts.
There have been varied approaches to determining impacts, with most studies attempting to compare invaded vs. non‐invaded habitats. The pros and cons of different approaches are discussed.
Since it is impractical to study every invasive plant in every ecological context in which it occurs, we recommend a better understanding of relevant individual‐level traits to predict direct interactions between invasive plants and native pollinators.
A Lay Summary is available for this article.
Tools for performing model selection and model averaging. Automated model selection through subsetting the maximum model, with optional constraints for model inclusion. Model parameter and prediction averaging based on model weights derived from information criteria (AICc and alike) or custom model weighting schemes.
[Please do not request the full text - it is an R package. The up-to-date manual is available from CRAN].
No information is available on the phenological phases between and within genotypes of Cyclopia (honeybush). This information is important to understand the timing of plant development and growth, species co-existence, and growth dynamics of the genus. The study spanning 2 years determined the monthly genotypic variation, the time of the start of a growth phase, and duration of budding, flowering, fruiting, and seed dispersal in C. subternata and C. genistoides. The results indicated differences in phenology between and within species and that initiation period among individuals of a phenological phase is inversely proportional to that duration of that phenophase. Budding, flowering, fruiting, and seed dispersal peaked in the months of July, September, October, and December, respectively. Compared to C. genistoides, C. subternata genotypes had a shorter time (days) from start of observation to start of flowering (25.9 versus 51.2), fruiting (46.1 versus 61.5), and seed dispersal (96.3 versus 110.0). However, the duration (days) of flowering (13.2 versus 24.3), fruiting (45.6 versus 52.2), and seed dispersal (4.3 versus 8.9) was shorter in C. genistoides. Using observational qualitative analysis, phenology of these Cyclopia species was categorised into three groups; early, intermediate, and late. The findings serve as a platform for investigating factors affecting the reproductive phases, morphology, and physiology in these and other Cyclopia species. It will assist farmers and researches to time crop requirements and management practices, thus having practical implications in the cultivation of the species.
Livelihood status, smallholder farming and climate change are directly interconnected in Sub-Sahara Africa. Simulations predict that yields of main crops will decrease and will be negatively impacted due to climate change within the next 30 to 40 years. The results of a simulation and survey about land use management and demography reveal the competitiveness of drought adapted pearl millet varieties concerning yields and the potential impact on sustainable smallholder farming in a semi-arid region of Kenya. We highlight the ability of adapted crops to improve livelihood through increased income generation and food security with the help of optimized farm management.
Contrasting flower color patterns that putatively attract or direct pollinators towards a reward are common among angiosperms. In the deceptive orchid Anacamptis morio, the lower petal, which makes up most of the floral display, has a light central patch with dark markings. Within populations, there is pronounced variation in petal brightness, patch size, amount of dark markings, and contrast between patch and petal margin. We tested whether pollinators mediate selection on these color traits and on morphology (plant height, number of flowers, corolla size, spur length), and whether selection is consistent with facilitated or negative frequency-dependent pollination. Pollinators mediated strong selection for increased petal brightness (Δβpoll = 0.42) and contrast (Δβpoll = 0.51). Pollinators also tended to mediate stabilizing selection on brightness (Δγpoll = -0.27, n.s.) favoring the most common phenotype in the population. Selection for reduced petal brightness among hand-pollinated plants indicated a fitness cost associated with brightness. The results demonstrate that flower color traits influence pollination success and seed production in A. morio, indicating that they affect attractiveness to pollinators, efficiency of pollen transfer, or both. The documented selection is consistent with facilitated pollination and selection for color convergence towards co-occurring rewarding species. This article is protected by copyright. All rights reserved.
Phenotypic convergence is rampant throughout the tree of life. While recent studies have made significant progress in ascertaining the proximate mechanisms underlying convergent phenotypes, less is known about the frequency and predictability with which convergent phenotypes arise via the same or multiple pathways at the macroevolutionary scale. We investigated the proximate causes and evolutionary patterns of red flower color in the tomato family, Solanaceae, using large-scale data mining and new sequence data to reconstruct a megaphylogeny of 1341 species. We then combined spectral and anatomical data to assess how many times red flowers have evolved, the relative contribution of different pathways to independent origins of red, and whether the underlying pathway is predicted by phylogenetic relatedness. We estimated at least 30 relatively recent origins of red flowers using anthocyanins, carotenoids, or a dual production of both pigments, with significant phylogenetic signal in the use of anthocyanins and dual production, indicating that closely related red-flowered species tend to employ the same mechanism for coloration. Our study is the first to test whether developmental pathways exhibit phylogenetic signal and implies that historical contingency strongly influences the evolution of new phenotypes.
© 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.
I. II. III. IV. References SUMMARY: Floral traits often show correlated variation, both within and across species. One explanation for this pattern of floral integration is that different elements of floral phenotypes are controlled by the same genes, that is, that the genetic architecture is pleiotropic. Recent studies from a range of model systems suggest that the pleiotropy is common among the loci responsible for floral divergence. Moreover, the effects of allelic substitutions at these loci are overwhelmingly aligned with direction of divergence, suggesting that the nature of the pleiotropic effects was adaptive. Molecular genetic studies have revealed the functional basis for some of these effects, although much remains to be discovered with respect to the molecular, biochemical and developmental mechanisms underlying most quantitative trait loci (QTL) responsible for floral differences. Developing a detailed understanding of the nature of pleiotropic mutations and their phenotypic consequences is crucial for modeling how the genetic architecture of trait variation influences the tempo and trajectory of floral evolution.
© 2015 The Author. New Phytologist © 2015 New Phytologist Trust.