Tagged: facilitation

Improving overyielding in legume-based mixtures

A major challenge when supporting the development of intercropping systems remains the design of efficient species mixtures. The ecological processes that sustain overyielding of legume-based mixtures compared to pure crops are well known, but their links to plant traits remain to be unravelled. A common assumption is that enhancing trait divergence among species for resource acquisition when assembling plant mixtures should increase species complementarity and improve community performance. Taking Faverjon et al. (2019a) as the starting point, Gaëtan Louarn and colleagues used a modelling approach to investigate the determinants of overyielding in legume-based forage mixtures. The first aim was to...

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Examples of habitat and representative herbaceous species at the study sites.

Floral colour structure in two Australian herbaceous communities

Pollinator-mediated interactions between plant species may affect the composition of angiosperm communities. Floral colour signals should play a role in these interactions, but the role will arise from the visual perceptions and behavioural responses of multiple pollinators. Recent advances in the visual sciences can be used to inform our understanding of these perceptions and responses. Shrestha and colleagues outline the application of appropriate visual principles to the analysis of the annual cycle of floral colour structure in two Australian herbaceous communities. The authors used spectrographic measurements of petal reflectance to determine the location of flowers in a model of hymenopteran...

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Vascular plants in an alpine cushion

Functional traits of vascular plants colonizing alpine cushions

Global warming threatens species living in the highest and coldest areas. Alpine cushion plants are potentially endangered by stronger species expanding from lower elevations. This can be inferred from their ecological strategies. Dolezal et al. analyse traits and habitat preferences of plants colonizing Thylacospermum caespitosum (Caryophyllaceae), a dominant pioneer of Himalayan subnival zones. Successful colonizers are fast-growing, clonal graminoids and forbs, sharing the syndrome of competitive species with broad elevation ranges typical for the late stages of primary succession. Since climate change in the Himalayas favours these species, highly specialized cushion plants may face intense competition and a greater risk...

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Illustrations of the cosexual artificial flowers used in the experiments.

Pollination quantity and purity

If you share a pollinator with another plant species in your location, is it a good idea to flower at the same time? You can only use pollen from another plant in the same species. If a bee arrives loaded with another species’s pollen, then what you get is junk. Similarly, if you load a bee with pollen, and it doesn’t visit another flower of your species, you’ve wasted your effort. On the other hand, if you’re next to a more attractive species, you might get more visits than you would alone. You get poorer quality pollen, but so much...

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Namaqualand in bloom

How do pollinators paint the landscape with colour?

When you look at a patch of flowers, you often see clusters of colour. Even when a single species can have many different colours, you get patches. Why? How does a plant know to grow with this colour and not that colour? The answer is it doesn’t. The colour is set by the genes in its seed, so how do those genes get there? Are pollinators somehow involved in creating these patches of similar colours? This is a problem that Jurene Kemp and colleagues have been investigating. The flowers that the team studied are daisies in Namaqualand, South Africa. Namaqualand...

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Positive and negative interactions on a dioecious grass species performance

Dioecious plants are of particular concern in view of global environmental changes because reproductive females are more sensitive to abiotic stresses, thus compromising population viability. Positive interactions with other plants may counteract the direct effects of any abiotic environmental stress, allowing them to thrive and maintain a viable population in suboptimal habitats, although this process has not been tested for dioecious species. Furthermore, almost no data are available on the outcome of such species interactions and their link with local spatial patterns and sex ratios. Graff et al. find that facilitation, mediated by shrub canopies, help females of the native...

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Caragana versicolor

Stress or Strain Gradient Hypothesis?

The Stress Gradient Hypothesis (SGH) proposes that competition prevails in undisturbed and productive environments, and shifts to facilitation in disturbed or stressful environments. Yet the environmental condition where facilitation or competition prevails is highly debated. Liancourt et al. investigate variation in plant interactions, by analysing how Caragana versicolor species and associated community perceive and respond to the ambient level of stress, over the species’ entire elevation range in the arid Trans-Himalayas. The authors propose a double-sided interpretation of SGH: the Stress Gradient Hypothesis that predicts where facilitation should prevail at the community level and, on the other side of the...

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Sun/shade conditions and seedling recruitment in a cactus

Sun/shade conditions and seedling recruitment in a cactus

Early life-history stages of cacti can benefit from the facilitative effects of nurse plants that reduce solar radiation and water stress. Miranda-Jácome et al. conduct a reciprocal transplant experiment, coupled with the artificial manipulation of sun/shade conditions, to test for the effects of local adaptation on germination, seedling survival and growth of the columnar cactus Pilosocereus leucocephalus. They find that significant local adaptation is mainly detected under full sunlight conditions, indicating that sun/shade acts as a selective agent in water-limited environments. Facilitation provided by nurse plants in these environments can attenuate the patterns of local adaptation among plants benefiting from nurse...

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