Recent evidence indicates that meiosis arose very early in eukaryotic evolution, which suggests that essential features of meiosis were already present in the prokaryotic ancestors of eukaryotes. Furthermore, in extant organisms, proteins with central functions in meiosis are similar in sequence and function to key proteins in bacterial transformation. In particular, RecA recombinase—which performs the central functions of DNA homology search and strand exchange in bacterial transformation—has orthologs in eukaryotes that carry out similar functions in meiotic recombination. Both transformation and meiosis (including meiotic recombination) in eukaryotic microorganisms are induced by stressful conditions, such as overcrowding, resource depletion, and DNA-damaging conditions, suggesting that these processes are adaptations for dealing with stress. If such environmental stresses were a persistent challenge to the survival of early microorganisms, then continuity of selection through the prokaryote to eukaryote transition probably would have followed a course in which bacterial transformation naturally gave rise to the recombination process that is central to eukaryote meiosis.

Few biological studies have investigated the hadal depths within oceanic trenches that plummet from 6000 meters (m) to the full ocean depth of almost 11,000 m. Here we present the deepest known in situ observations of fish: a hadal snailfish, Pseudoliparis amblystomopsis (Andriashev 1955), from 7703-m deep in the Japan Trench, which was obtained using a baited video lander. The maximum number of fish we observed was unexpectedly higher than trawl catch records of any known hadal fish. We describe changes in fish abundance and associated behaviors over time, including feeding, resting, and swimming. In light of these new observations, we reappraise the occurrence and diversity records of hadal fishes that have been constructed from fragmentary and often misleading information derived from historical explorations and global data sets. This reappraisal suggests that hadal fish diversity may be lower—although some hadal fish species may attain much larger populations—than previously thought.

Humans, in conjunction with natural top-down processes and through a sequence of cascading trophic interactions, may have contributed to the Pleistocene megafaunal extinctions. The arrival of the first humans, as hunters and scavengers, through top-down forcing, could have triggered a population collapse of large herbivores and their predators. We present evidence that the large mammalian herbivores of the North American Pleistocene were primarily predator limited and at low densities, and therefore highly susceptible to extinction when humans were added to the predator guild. Our empirical evidence comes from data on carnivore dental attrition, proboscidean age structure, life history, tusk growth rates, and stable isotopes from the fossil record. We suggest a research agenda for further testing of this hypothesis that will provide a more detailed comprehension of late Pleistocene megafaunal ecology, and thereby allow us to better understand and manage remaining megafauna.

Many traditional farmers and environmentalists subscribe to the popular idea that the natural world offers ecosystem services that contribute to the stability, productivity, and sustainability of agriculture. Opponents of this view argue that the farm is not an environment to be stewarded by romantic environmentalists, but rather is a battlefield on which the enemies of production must be vanquished. Contemporary research in ecosystem complexity offers a new platform on which to adjudicate between these two points of view. Through particular network structuring, nonlinearity, and stochasticity, and especially with the added dimension of space, recent theoretical and empirical research reveals that ecological systems persist and generate ecosystem services as a result of complex interacting components. Here we report on our research into the ecological dynamics of a collection of species related to key problems in pest control, a critical ecosystem service in coffee production.

Progress in understanding and achieving sustainability requires addressing it as both a scientific and an ethical issue. If sustainability is defined as “meeting human needs in a socially just manner without depriving ecosystems of their health,” most of the words in its definition are normative or value laden. Depending on how critical normative terms such as “human needs” and “ecosystem health” are defined, sustainability could mean anything from “exploit as much as desired without infringing on the future ability to exploit as much as desired” to “exploit as little as necessary to maintain a meaningful life.” We suggest that there are five key areas of sustainability. By examining how recent university cluster hires in sustainability compare with these five areas, we show not only how hiring has been radically lopsided but also how ethics has been entirely ignored. Lack of attention to the ethical dimension of sustainability is stifling progress toward sustainability.

Wildlife populations are affected by habitat loss and fragmentation resulting from actions undertaken by various parties across broad geographic scales. One way to account for these effects is through cumulative effects analysis (CEA), a legal requirement under the National Environmental Policy Act that has been a persistent challenge for natural resource agencies. This article provides an overview of the CEA requirement, and uses the US Forest Service's approach as a platform for assessing the promises and pitfalls of connecting CEA to effective wildlife conservation planning. I conducted a case study analysis, using document analysis and interviews, to investigate CEA practice and its associated challenges. I found that current CEA practice relies on habitat-based measurements and fails to account for long-term or broad-scale impacts, resulting in a disconnect between the approaches taken to CEA and accurate understanding of biological effects. Insufficient monitoring stands out as the primary impediment to improving CEA. Increased monitoring, improved knowledge of species-habitat relationships, and the development of scientifically credible assessments are potential ways forward.