Hybrid species are on the march – with the help of humans

First paragraph: Species that evolved far apart have been thrown together by worldwide transport, global warming, deforestation and farming. This is increasing the rate at which plant hybrids are being produced and these new species can dramatically affect local plants, animals and ecosystems. Access this article on The Conversation website: https://theconversation.com/hybrid-species-are-on-the-march-with-the-help-of-humans-5964

Revealed: the first ever flower, 140m years ago, looked like a magnolia

First paragraph: Although most species of plants on Earth have flowers, the evolutionary origin of flowers themselves are shrouded in mystery. Flowers are the sexual organs of more than 360,000 species of plants alive today, all derived from a single common ancestor in the distant past. This ancestral plant, alive sometime between 250m and 140m years ago, produced the first flowers at a time when the planet was warmer, and richer in oxygen and greenhouse gases than today. A time when dinosaurs roamed primeval landscapes

Genomics of invasion: Diversity and selection in introduced populations of monkeyflowers (Mimulus guttatus)

Global trade and travel is irreversibly changing the distribution of species around the world. Because introduced species experience drastic demographic events during colonization and often face novel environmental challenges from their native range, introduced populations may undergo rapid evolutionary change. Genomic studies provide the opportunity to investigate the extent to which demographic, historical and selective processes shape the genomic structure of introduced populations by analysing the signature that these processes leave on genomic variation. Here, we use next-generation sequencing to compare genome-wide relationships and patterns of diversity in native and introduced populations of the yellow monkeyflower (Mimulus guttatus). Genome resequencing data from 10 introduced populations from the United Kingdom (UK) and 12 native M.guttatus populations in North America (NA) demonstrated reduced neutral genetic diversity in the introduced range and showed that UK populations are derived from a geographic region around the North Pacific. A selective-sweep analysis revealed site frequency changes consistent with selection on five of 14 chromosomes, with genes in these regions showing reduced silent site diversity. While the target of selection is unknown, genes associated with flowering time and biotic and abiotic stresses were located within the swept regions. The future identification of the specific source of origin of introduced UK populations will help determining whether the observed selective sweeps can be traced to unsampled native populations or occurred since dispersal across the Atlantic. Our study demonstrates the general potential of genome-wide analyses to uncover a range of evolutionary processes affecting invasive populations

Selection through female fitness helps to explain the maintenance of male flowers

Andromonoecy, the production of both male and hermaphrodite flowers in the same individual, is a widespread phenomenon that occurs in approximately 4,000 species distributed in 33 families. Hypotheses for the evolution of andromonoecy suggest that the production of intermediate proportions of staminate flowers may be favored by selection acting through female components of fitness. Here we used the andromonoecious herb Solanum carolinense to determine the pattern of selection on the production of staminate flowers. A multivariate analysis of selection indicates that selection through female fitness favors the production of staminate flowers in at least one population. We conclude that this counterintuitive benefit of staminate flowers on female fitness highlights the importance of considering female components of fitness in the evolution of andromonoecy, a reproductive system usually interpreted as a "male" strategy

Il y a 140 millions d’années, la toute première fleur ressemblait à un magnolia

First paragraph: La majorité des plantes qui peuplent la Terre disposent de fleurs. Mais l’histoire de leur origine reste largement mystérieuse. Les fleurs constituent aujourd’hui les organes sexuels de plus de 360000espèces de plantes vivantes, toutes issues d’un unique ancêtre commun

Mimulus peregrinus (Phrymaceae): A new British allopolyploid species

Polyploidization plays an important role in species formation as chromosome doubling results in strong reproductive isolation between derivative and parental taxa. In this note I describe a new species, Mimulus peregrinus (Phrymaceae), which represents the first recorded instance of a new British polyploid species of Mimulus (2n = 6x = 92) that has arisen since the introduction of this genus into the United Kingdom in the 1800’s. M. peregrinus presents floral and vegetative characteristics intermediate between M. guttatus and M. luteus, but can be distinguished from all naturalized British Mimulus species and hybrids based on a combination of reproductive and vegetative traits. M. peregrinus displays high pollen and seed fertility as well as traits usually associated with genome doubling such as increased pollen and stomata size. The intermediate characteristics of M. peregrinus between M. guttatus (2n = 2x = 28) and M. luteus (2n = 4x = 60-62), and its close affinity with the highly sterile, triploid (2n = 3x = 44-45) hybrid taxon M. × robertsii (M. guttatus × M. luteus), suggests that M. peregrinus may constitute an example of recent allopolyploid speciatio

How and why do bees buzz? Implications for buzz pollination

Buzz pollination encompasses the evolutionary convergence of specialised floral morphologies and pollinator behaviour in which bees use vibrations (floral buzzes) to remove pollen. Floral buzzes are one of several types of vibrations produced by bees using their thoracic muscles. Here I review how bees can produce these different types of vibrations and discuss the implications of this mechanistic understanding for buzz pollination. I propose that bee buzzes can be categorised according to their mode of production and deployment into: (1) thermogenic, which generate heat with little mechanical vibration; (2) flight buzzes, which combined with wing deployment and thoracic vibration, power flight, and (3) non-flight buzzes in which the thorax vibrates but the wings remain folded, and include floral, defence, mating, communication, and nest-building buzzes. I hypothesise that the characteristics of non-flight buzzes, including floral buzzes, can be modulated by bees via modification of the biomechanical properties of the thorax through activity of auxiliary muscles, changing the rate of activation of the indirect flight muscles, and modifying flower handling behaviours. Thus, bees should be able to fine-tune mechanical properties of their floral vibrations, including frequency and amplitude, depending on flower characteristics and pollen availability to optimise energy use and pollen collection

Riverbanks as battlegrounds: why does the abundance of native and invasive plants vary?

The abundance of invasive alien plants (IAPs) can vary dramatically over small spatial scales for reasons that are often unclear. Understanding these could offer key insights for containing invasions, accepting that eradication is often no longer feasible. This study investigated determinants of IAP cover on riverbanks, a well-known hotspot of invasion, using Impatiens glandulifera, a prolific invader across the Northern hemisphere, as a model species. Within this framework we included the potential for dominant native vegetation cover, mediated by favourable environmental conditions, to resist invasion by I. glandulifera through negative association. Our analyses, using structural equation modelling, showed that I. glandulifera is more sensitive to environmental conditions, than dominant native vegetation. High soil moisture was a key determinant of I. glandulifera cover, having negative effects across the riparian zone. Spatially, I. glandulifera and dominant native vegetation responded differently to environmental conditions. Sites with steeper banks had less dominant native vegetation at the water's edge, potentially favouring I. glandulifera cover through reduced competition. In general, greater abundance of dominant native vegetation presented a more invasion-resistan

Quantifying the potential of 'on-farm' seed priming to increase crop performance in developing countries. A meta-analysis

Low-input agriculture in marginal areas of developing countries faces considerable challenges during crop development. A key stage in crop growth is seed germination, which is often constrained by abiotic factors such as low water potential, high temperatures and soil crusting, which can result in poor establishment. This is exacerbated by low soil fertility, salinity, drought, pests and diseases, which ultimately leads to reduced yields. Over the last 20 years, the potential of 'on-farm' seed priming, a traditional, low-cost technique, consisting of soaking seeds in water prior to sowing, has been applied to different crops and conditions with varying degrees of success. To understand the significance of this potentially transformative agronomic strategy, we have conducted a global meta-analysis of on-farm seed priming by quantifying (i) the rate of emergence, (ii) final emergence and (iii) total yield from 44 published papers on 17 crops across 10 countries. Our results show that on-farm seed priming has a significantly positive effect on crop performance: seeds emerge 22% faster, with an increased final emergence of 11%, with total yields 21% higher than conventionally sown seeds. Furthermore, sub-group analyses demonstrated that on-farm seed priming is more advantageous under stressful abiotic conditions with case studies categorized as being either 'nutrient deficient', 'salinity-stressed' or 'dry climates' gaining the highest yield improvements (22–28%). On-farm seed priming can be particularly beneficial to resource-poor farmers working in low-input agricultural systems where yield potential is limited by intrinsically stressed agronomic environments. Here, we demonstrate for the first time that on-farm seed priming is perfectly adapted to local situations in developing countries. Our results provide the evidence that on-farm seed priming could be effectively adopted by resource-poor farmers as a strategy to increase food security in some of the most marginal agricultural areas

Bee and floral traits affect the characteristics of the vibrations experienced by flowers during buzz pollination

During buzz pollination, bees use their indirect flight muscles to produce vibrations that are transmitted to the flowers and result in pollen release. Although buzz pollination has been known for >100 years, we are still in the early stages of understanding how bee and floral characteristics affect the production and transmission of floral vibrations. Here, we analysed floral vibrations produced by four closely related bumblebee taxa (Bombus spp.) on two buzz-pollinated plants species (Solanum spp.). We measured floral vibrations transmitted to the flower to establish the extent to which the mechanical properties of floral vibrations depend on bee and plant characteristics. By comparing four bee taxa visiting the same plant species, we found that peak acceleration, root mean-squared acceleration (RMS) and frequency vary between bee taxa, but that neither bee size (intertegular distance) nor flower biomass (dry mass) affects peak acceleration, RMS or frequency. A comparison of floral vibrations of two bee taxa visiting flowers of two plant species showed that, while bee species affects peak acceleration, RMS and frequency, plant species only affects acceleration (peak acceleration and RMS), not frequency. When accounting for differences in the transmission of vibrations across the two types of flower, using a species-specific ‘coupling factor’, we found that RMS acceleration and peak displacement do not differ between plant species. This suggests that bees produce the same initial acceleration in different plants but that transmission of these vibrations through the flower is affected by floral characteristics