The North Pacific is the largest cold-water source of lineages spreading to other modern marine temperate biotas. How this status was achieved remains unclear. One hypothesis is that functional innovations of large effect, defined as departures from the norm in temperate clades and which confer competitive or defensive benefits, increase resource availability, and raise performance standards in the biota as a whole, evolved earlier and more frequently in the North Pacific than elsewhere in the temperate zone. In support of this hypothesis, phylogenetic and fossil evidence reveals 47 temperate marine innovations beginning in the latest Eocene, of which half arose in the North Pacific. Of the 22 innovations of large effect, 13 (39%) evolved in the North Pacific, including basal growth in kelps and bottom-feeding herbivory and durophagy in mammals. Temperate innovations in the Southern Hemisphere and the North Atlantic appeared later and were less consequential. Most other innovations arose in refuges where the risks of predation and competition are low. Among temperate marine biotas, the North Pacific has the highest incidence of unique innovations and the earliest origins of major breakthroughs, five of which spread elsewhere.

Molluscan shells exhibit a high and largely neglected diversity of serrations and crenulations at the growing margin. A survey of living and Cenozoic fossil bivalves indicates that serrations, in which the external ribs or interspaces between ribs extend radially beyond the general contour of the valve margin, may be symmetrical or asymmetrical. Projections whose adumbonal edge more nearly parallels the shell edge than the abumbonal edge occur on the posterior valve margins of many limids, cardiids and donacids, as well as in the arcid Anadara and a few concentrically ridged tellinids. In many cardiids, posterior serrations form as extensions of ribs, whereas ventral and anterior projections are extensions of rib interspaces. Asymmetrical serrations are almost always found on shell edges that are polished, indicating that the mantle extends slightly over the valve margin to the outside. I tentatively suggest that asymmetrical serrations enable the valves to close around siphons or other mantle extensions without injuring these soft tissues, so that the bivalve can maintain sensory contact with the environment even while the shell is shut. A preliminary comparison with brachiopods indicates that the diversity of conditions at the shell edge is much higher in bivalves. Together with the largely warm-water and marine distribution of marginal modifications in bivalves, these comparisons reflect the higher metabolic potentials of bivalves relative to brachiopods, and show that the shell edge is a rich source of evidence about function and mode of life in fossils.©The Author 2013. Published by Oxford University Press on behalf of The Malacological Society of London, all rights reserved.

Oysters, whose inner shell layer contains chambers, vesicles, and sometimes chalky deposits, often have extraordinarily thick shells of large size, prompting the idea that there is something unusual about the process of shell fPormation in these and similarly structured bivalves with the oyster syndrome. I propose the hypothesis that calcifying microbes, especially sulfate-reducing bacteria growing on organic substrates in fluid-filled shell-wall chambers, are responsible for shell calcification away from the shell-secreting mantle of the host bivalve. Other phenomena, including the formation of cameral deposits in fossil cephalopods, the cementation of molluscs and barnacles to hard substrata, the formation of a calcified intriticalx on the shell's exterior, and cementation of objects by gastropods on the shell for camouflage, may also involve calcifying bacteria. Several lines of inquiry are suggested to test these hypotheses. © 2014 The Paleontological Society. All rights reserved.

Evolution has produced an astonishing array of organisms, but does it have limits and, if so, how are these overcome and how have they changed over the course of time? Here, I review models for describing and explaining existing diversity, and then explore parts of the evolutionary tree that remain empty. In an analysis of 32 forbidden states among eukaryotes, identified in major clades and in the three great habitat realms of water, land and air, I argue that no phenotypic constraint is absolute, that most constraints reflect a limited time-energy budget available to individual organisms, that natural selection is ultimately responsible for both imposing and overcoming constraints, including those normally ascribed to developmental patterns of construction and phylogenetic conservatism, and that increases in adaptive versatility in major clades together with accompanying new ecological opportunities have eliminated many constraints. Phenotypes that were inaccessible during the Early Palaeozoic era have evolved during later periods while very few adaptive states have disappeared. The filling of phenotypic space has proceeded cumulatively in three overlapping phases characterized by diversification at the biochemical, morphological and cultural levels.

Future environments may resemble conditions that have not existed for millions of years. To assess the adaptive options available to organisms evolving under such circumstances, it is instructive to probe paleophysiology, the ways in which ancient life coped with its physical and chemical surroundings. To do this, we need reliable proxies that are based on fundamental principles, quantitatively verified in living species, and observable in fossil remains. Insights have already come from vertebrates and plants, and others will likely emerge for marine animals if promising proxies are validated. Many questions remain about the circumstances for the evolution of environmental tolerances, metabolic rates, biomineralization, and physiological responses to interacting species, and about how living organisms will perform under exceptional conditions.

AbstractHistorians have debated whether pathways and events from the past to the present are influenced largely by contingency, the dependence of outcomes on particular prior conditions, or whether there is long-term emergent directional change. Previous arguments for predictability in evolutionary history relied on the high frequency of convergence, but the repeated evolution of widely favored adaptations need not imply long-term directionality. Using evidence from the fossil record and arguments concerning the metabolic evolution of organisms, I show here that power (total energy taken up and expended per unit time) has increased stepwise over time at ecosystem-level and global scales thanks to the ratchet-like, cumulative effects of competition and cooperation and to the disproportionate influence of powerful top competitors and opportunistic species on emergent ecosystem properties and processes. The history of life therefore exhibits emergent directionality at large ecosystem-wide scales toward greater power.

Land plants exhibit a wide variety of defences that deter the consumption of leaves and stems, including trichomes (hairs), thorns, and thick cuticles. In many plants, trichomes are hooked or inclined to the leaf or stem surface, and the teeth on leaf margins point either apically or more rarely toward the base. The role of these anisotropic structures as potential defences has been largely ignored. In the present study, it is proposed that apically oriented surface features function as ratchets directing the movements of small herbivores toward the leaf ends and ultimately off the leaf, whereas basally oriented protrusions interfere with the ascent of consumers to the upper parts of the plant. These proposed defencive functions do not exclude other potential benefits of anisotropic features, such as self-cleaning of surfaces. The proposed defencive role of apically oriented trichomes and teeth may represent an unusual class of physical defences that speed up rather than slow down encounters between enemies and their plant victims.

The shells of many marine gastropods have ventrally directed serrations (serial projections) at the edge of the adult outer lip. These poorly studied projections arise as extensions either of external spiral cords or of interspaces between cords. This paper describes taxonomic, phylogenetic, architectural and functional aspects of serrations. Cord-associated serrations occur in cerithiids, strombids, the personid Distorsio anus, ocenebrine muricids and some cancellariids. Interspace-associated serrations are phylogenetically much more widespread, and occur in at least 16 family-level groups. The nature of serration may be taxonomically informative in some fissurellids, littorinids, strombids and costellariids, among other groups. Serrated outer lips occur only in gastropods in which the apex points more backward than upward, but the presence of serrations is not a necessary byproduct of the formation of spiral sculptural elements. In hard-bottom gastropods that do not flee from predators, pointed serrations may resist shear when the shell is clamped firmly to the substratum. The functions of serration in other gastropods are less clear, but likely involve defence against predators with soft feeding structures in some cases. © 2014 The Author 2014.

Comparative economics—the description and underlying explanation of human and nonhuman variations on the relationship between life and its environment—seeks to discover how and to what extent the limitations that apply to some living systems can be overcome in others, including our own economy. It is founded on four phenomena, which collectively explain how life and its economic structures arise, how diversity of form and function come about, and how change occurs. These phenomena are self-organization, emergence (new properties and entities formed when parts combine), selection and adaptation, and feedback between living things and their surroundings. The systems of life vary in patterns of inheritance, the units among which selection takes place, resources, and size; these variables, in turn, affect patterns of history, adaptability, and innovation. Beneath the variation, all living systems are subject to local competition, cooperation, and evolution. Ten distinctive institutions and capacities have been thought to be unique to modern humans: cultural (non-genetic) inheritance of information and adaptations; cooperation among genetically unrelated individuals; markets in which enforceable contracts determine the quantities and prices of goods and services; utility, emergent goals and values informed by stable preferences; intentionality, deliberate action toward a predetermined goal; innovation by designing devices and institutions without historical precedents; symbolic thought; extrasomal extension, work performed beyond internal metabolism; and unsustainable exploitation of resources. These traits and capacities, which confer unprecedented power and reach, occur widely outside the human realm and have evolved independently in many organisms and ecosystems. They accelerate but do not fundamentally alter adaptation and innovation, and reduce but do not eliminate the constraints under which life in a finite world has persisted for three and a half billion years. Future civilization on Earth is therefore unlikely to forge an entirely new world order. Policies and predictions that are inconsistent with these universal realities are likely to fail. In particular: (1) local competition will remain necessary for successful adaptation and innovation; (2) an information-based economy will not replace an energy-based one, and energy use is unlikely to decline; and (3) redundancy of production in multiple sites must not be sacrificed through free trade and elimination of subsidies to achieve greater economic efficiency. Human survival requires that we work with nature, not against it.