Agricultural intensification and climate change are rapidly decreasing insect biodiversity.

Major declines in insect biomass and diversity, reviewed here, have become obvious and well documented since the end of World War II. Here, we conclude that the spread and intensification of agriculture during the past half century is directly related to these losses. In addition, many areas, including tropical mountains, are suffering serious losses because of climate change as well. Crops currently occupy about 11% of the world's land surface, with active grazing taking place over an additional 30%. The industrialization of agriculture during the second half of the 20th century involved farming on greatly expanded scales, monoculturing, the application of increasing amounts of pesticides and fertilizers, and the elimination of interspersed hedgerows and other wildlife habitat fragments, all practices that are destructive to insect and other biodiversity in and near the fields. Some of the insects that we are destroying, including pollinators and predators of crop pests, are directly beneficial to the crops. In the tropics generally, natural vegetation is being destroyed rapidly and often replaced with export crops such as oil palm and soybeans. To mitigate the effects of the Sixth Mass Extinction event that we have caused and are experiencing now, the following will be necessary: a stable (and almost certainly lower) human population, sustainable levels of consumption, and social justice that empowers the less wealthy people and nations of the world, where the vast majority of us live, will be necessary.

Vertebrates on the brink as indicators of biological annihilation and the sixth mass extinction.

The ongoing sixth mass species extinction is the result of the destruction of component populations leading to eventual extirpation of entire species. Populations and species extinctions have severe implications for society through the degradation of ecosystem services. Here we assess the extinction crisis from a different perspective. We examine 29,400 species of terrestrial vertebrates, and determine which are on the brink of extinction because they have fewer than 1,000 individuals. There are 515 species on the brink (1.7% of the evaluated vertebrates). Around 94% of the populations of 77 mammal and bird species on the brink have been lost in the last century. Assuming all species on the brink have similar trends, more than 237,000 populations of those species have vanished since 1900. We conclude the human-caused sixth mass extinction is likely accelerating for several reasons. First, many of the species that have been driven to the brink will likely become extinct soon. Second, the distribution of those species highly coincides with hundreds of other endangered species, surviving in regions with high human impacts, suggesting ongoing regional biodiversity collapses. Third, close ecological interactions of species on the brink tend to move other species toward annihilation when they disappear-extinction breeds extinctions. Finally, human pressures on the biosphere are growing rapidly, and a recent example is the current coronavirus disease 2019 (Covid-19) pandemic, linked to wildlife trade. Our results reemphasize the extreme urgency of taking much-expanded worldwide actions to save wild species and humanity's crucial life-support systems from this existential threat.

Genome skimming provides new insight into the relationships in Ludwigia section Macrocarpon, a polyploid complex.

PREMISE OF THE STUDY: Interpreting relationships within groups containing polyploids, which are frequent in angiosperms, can be greatly assisted by genomic techniques. In this study, we used a genome-skimming approach to investigate the evolutionary relationships and origins of polyploids in the monophyletic group, Ludwigia section Macrocarpon (Onagraceae), which includes diploid, tetraploid, and hexaploid taxa. METHODS: We sampled all known taxa and ploidy levels in the section and conducted shotgun sequencing. We assembled plastomes, mitochondrial sequences, and completed nuclear ribosomal regions, reconstructed phylogenies, and conducted comparative genomic analyses for plastomes to gain insights into the relationships among studied taxa. KEY RESULTS: Within the section, results showed that the South American diploid taxa L. bonariensis and L. lagunae were closely related. We reported the first chromosome count (2n = 4× = 32) for L. neograndiflora, which is closely related to the two South American diploid taxa, although its exact origin remains unclear. The samples of the widespread, polyploid taxon L. octovalvis do not form a monophyletic group. Both tetraploid and hexaploid L. octovalvis lineages have originated more than once. At least one tetraploid in the L. octovalvis lineage may have been involved in the origins of hexaploids. One or more extinct/unsampled intermediate tetraploids in the L. octovalvis lineages had also likely been involved in the origins of hexaploids. CONCLUSIONS: Genome skimming provided important insights into the complex evolutionary relationships within sect. Macrocarpon, but additional sampling and data from single-copy nuclear regions are necessary to further elucidate the origins of the polyploids in this section.

GM crops, the environment and sustainable food production.

Today, over 7.1 billion people rely on the earth's resources for sustenance, and nearly a billion people are malnourished, their minds and bodies unable to develop properly. Globally, population is expected to rise to more than 9 billion by 2050. Given the combined pressures of human population growth, the rapidly growing desire for increased levels of consumption, and the continued use of inappropriate technologies, it is not surprising that humans are driving organisms to extinction at an unprecedented rate. Many aspects of the sustainable functioning of the natural world are breaking down in the face of human-induced pressures including our individual and collective levels of consumption and our widespread and stubborn use of destructive technologies. Clearly, agriculture must undergo a redesign and be better and more effectively managed so as to contribute as well as possible to feeding people, while at the same time we strive to lessen the tragic loss of biodiversity and damage to all of its productive systems that the world is experiencing. For GM crops to be part of the solution, biosafety assessments should not be overly politically-driven or a burdensome impedance to delivering this technology broadly. Biosafety scientists and policy makers need to recognize the undeniable truth that inappropriate actions resulting in indecision also have negative consequences. It is no longer acceptable to delay the use of any strategy that is safe and will help us achieve the ability to feed the world's people.

Mother trees, altruistic fungi, and the perils of plant personification.

There are growing doubts about the true role of the common mycorrhizal networks (CMN or wood wide web) connecting the roots of trees in forests. We question the claims of a substantial carbon transfer from 'mother trees' to their offspring and nearby seedlings through the CMN. Recent reviews show that evidence for the 'mother tree concept' is inconclusive or absent. The origin of this concept seems to stem from a desire to humanize plant life but can lead to misunderstandings and false interpretations and may eventually harm rather than help the commendable cause of preserving forests. Two recent books serve as examples: The Hidden Life of Trees and Finding the Mother Tree.

Rethinking primate origins again.

In 1974, Cartmill introduced the theory that the earliest primate adaptations were related to their being visually oriented predators active on slender branches. Given more recent data on primate-like marsupials, nocturnal prosimians, and early fossil primates, and the context in which these primates first appeared, this theory has been modified. We hypothesize that our earliest primate relatives were likely exploiting the products of co-evolving angiosperms, along with insects attracted to fruits and flowers, in the slender supports of the terminal branch milieu. This has been referred to as the primate/angiosperm co-evolution theory. Cartmill subsequently posited that: "If the first euprimates had grasping feet and blunt teeth adapted for eating fruit, but retained small divergent orbits…" then the angiosperm coevolution theory would have support. The recent discovery of Carpolestes simpsoni provides this support. In addition, new field data on small primate diets, and a new theory concerning the visual adaptations of primates, have provided further evidence supporting the angiosperm coevolution theory.

How the living world evolved and where it's headed now.

The growth of life on Earth over more than 4 billion years has experienced five major extinction events, each followed by a period of rapid increase in species number. When organisms first invaded the land about 480 million years ago, another explosive proliferation of species followed. Our species, Homo sapiens, appeared some 300 000 years ago, developed agriculture about 11 000 years ago and grew rapidly to some 7.8 billion people, who are currently consuming about 175% of the sustainable productivity available worldwide. By mid-century (2050), we will have grown to about 9.9 billion. Wealth is very unequally distributed. Meanwhile, the Earth's mean temperature has increased by 1.1°C above pre-industrial levels, and we are on track for a total increase of 2.6 to 3.9°C. We are driving species to extinction at a rate unprecedented for the past 66 million years. These changes promise to be disastrous for the maintenance of civilization. Indeed, our only hope for a sustainable future will be for us to find a way to overcome our unremitting greed at all levels and to love one another while building social justice. This article is part of the theme issue 'Ecological complexity and the biosphere: the next 30 years'.

Embryology of the Irvingiaceae, a family with uncertain relationships among the Malpighiales.

The Irvingiaceae, one of 40 families of the Malpighiales, comprise a small woody family of 10 species in three genera distributed in Old World tropics. Its relationships with other families are unclear, although recent molecular analyses suggest affinities with Linaceae, Caryocaraceae, Erythroxylaceae, and Rhizophoraceae. To gain insight into family relationships, we investigated 63 embryological characters of two previously unstudied African species, Irvingia gabonensis and I. smithii, and compared them with other Malpighiales and the sister group Oxalidales. Embryologically, Irvingia is characterized by the absence of an integumentary tapetum and by having a non-multiplicative inner integument, a multiplicative testa, many discrete fascicles of vascular bundles running in the testa from the raphe to antiraphe (each fascicle comprised several strands arranged in a concentric manner), and a fibrous exotegmen. Comparisons showed that Irvingia did not resemble any of the Linaceae, Caryocaraceae, Erythroxylaceae, Rhizophoraceae, or any of the other malpighialean families for which embryological data are available. The genus rather resembled Huaceae and Connaraceae (Oxalidales) in seed coat structure. However, 18 families (45%) of the Malpighiales are still poorly understood embryologically, and therefore additional studies are required for further critical comparisons.

Phylogenetic patterns suggest frequent multiple origins of secondary metabolites across the seed-plant 'tree of life'.

To evaluate the phylogenetic patterns of the distribution and evolution of plant secondary metabolites (PSMs), we selected 8 classes of PSMs and mapped them onto an updated phylogenetic tree including 437 families of seed plants. A significant phylogenetic signal was detected in 17 of the 18 tested seed-plant clades for at least 1 of the 8 PSM classes using the D statistic. The phylogenetic signal, nevertheless, indicated weak clustering of PSMs compared to a random distribution across all seed plants. The observed signal suggests strong diversifying selection during seed-plant evolution and/or relatively weak evolutionary constraints on the evolution of PSMs. In the survey of the current phylogenetic distributions of PSMs, we found that multiple origins of PSM biosynthesis due to external selective forces for diverse genetic pathways may have played important roles. In contrast, a single origin of PSMs seems rather uncommon. The distribution patterns for PSMs observed in this study may also be useful in the search for natural compounds for medicinal purposes.

The distribution of biodiversity richness in the tropics.

We compare the numbers of vascular plant species in the three major tropical areas. The Afrotropical Region (Africa south of the Sahara Desert plus Madagascar), roughly equal in size to the Latin American Region (Mexico southward), has only 56,451 recorded species (about 170 being added annually), as compared with 118,308 recorded species (about 750 being added annually) in Latin America. Southeast Asia, only a quarter the size of the other two tropical areas, has approximately 50,000 recorded species, with an average of 364 being added annually. Thus, Tropical Asia is likely to be proportionately richest in plant diversity, and for biodiversity in general, for its size. In the animal groups we reviewed, the patterns of species diversity were mostly similar except for mammals and butterflies. Judged from these relationships, Latin America may be home to at least a third of global biodiversity.

The Fate of the World's Plants.

A recent report assessing the world's plant species finds continuing progress in completing the taxonomic catalog. However, many undescribed species remain. The report concludes that, presently, 21% of known species risk extinction. We show this statement applies to the short-term and ignores the as-yet undescribed species, which are also likely at risk of extinction. Human actions will extirpate many more by the end of this century.

An integrated assessment of the vascular plant species of the Americas.

The cataloging of the vascular plants of the Americas has a centuries-long history, but it is only in recent decades that an overview of the entire flora has become possible. We present an integrated assessment of all known native species of vascular plants in the Americas. Twelve regional and national checklists, prepared over the past 25 years and including two large ongoing flora projects, were merged into a single list. Our publicly searchable checklist includes 124,993 species, 6227 genera, and 355 families, which correspond to 33% of the 383,671 vascular plant species known worldwide. In the past 25 years, the rate at which new species descriptions are added has averaged 744 annually for the Americas, and we can expect the total to reach about 150,000.

Complete Plastome Sequence of Ludwigia octovalvis (Onagraceae), a Globally Distributed Wetland Plant.

Here, we present the first plastome of Ludwigia octovalvis (Onagraceae, Myrtales) as well as the first plastome in the subfamily Ludwigioideae. This genome is notable for its contracted inverted repeat regions and an expanded small single-copy region compared to other species in the orders Myrtales and Geraniales.

The correct name for a section of Ludwigia L. (Onagraceae).

In 1953, Hara provided new combinations for many sectional and species names when he combined Jussiaea L. with Ludwigia L., and at the time, Ludwigiasect.Oligospermum (Micheli) H.Hara was the correct name for one well-defined section. However, subsequent changes to/clarifications of the botanical code have necessitated a change for that name in that now an autonym is treated as having priority over the name or names of the same date and rank that established it. Since Hara's combination was based on Jussiaeasect.Oligospermum Micheli, the correct name for this section is Ludwigiasect.Jussiaea (L.) Hoch, W.L.Wagner, & P.H.Raven.

THE EVOLUTION OF POLLEN TETRADS IN ONAGRACEAE.

In Onagraceae, pollen is shed in mature tetrads in most Epilobieae, many species of Ludwigia (Jussiaeeae), and two closely related species of the large genus Camissonia (Onagreae). Mature tetrads of Camissonia cardiophylla and representative species of Epilobium and Ludwigia were examined with light, scanning, and transmission electron microscopes. Morphological diagnoses of monad units indicated that individual taxa could be readily distinguished. Statistical analyses of tetrads which remained after acetolysis treatment revealed significant differences in the strength of the binding mechanisms. Mechanisms of tetrad cohesion were found to consist of two principal types. Common to all taxa is cohesion of pollen wall surfaces at the aperture margins; this mechanism is well known in many angiosperm groups. With the exception of Camissonia, the remaining taxa also display binding by means of short exine fragments between adjacent pollen units. These fragments, termed bridges and reported here for the first time, are located in the area extending from the aperture margins to near the center of the proximal exine faces. Thin sections reveal that layers of the bridges are identical with those of the exine. Comparisons were made between bridges and viscin threads, both of which occur on the proximal faces of the grains. Viscin threads are present on all pollen grains in Onagraceae and exhibit distinctive morphologies, and bridges were viewed morphogenetically as related to viscin threads but including an endexine layer and occupying a position near the apertures where cohesion of wall surfaces also occurs. In an evolutionary sense, the formation of mature tetrads almost certainly occurred independently in Camissonia and may have done so in Ludwigia and the Epilobieae.