Model estimation of energy flow in North American grassland bird communities

Summary The energy demands and general food consumption rates of bird populations breeding in North American grasslands are estimated using a simulation model which employs information on population natural history and individual metabolism gathered from several study locations. The total breeding season energy demand of the grassland/shrub-steppe avifaunas ranged from 0.89 kcal m^-2 season^-1 in arid shrub-steppe to 2.92 kcal m^-2 season^-1 in a mesic tallgrass prairie. There was substantial variation between years and between census plots, however, and in general the average avian community energy demands did not differ significantly over the range of locations. Production accounted for 0.9 to 1.5% of the total seasonal energy demand. Roughly 11 to 18% of the seasonal energy flow was required in the production of eggs and maintenance and growth of nestlings and fledglings.On the average, between 209 and 386 kg dry wt km^-2 of prey were consumed by the bird communities breeding in the grassland locations. Seeds contributed more to the total biomass consumed at the drier plots, but in general, animal prey types comprised roughly 80% of the total biomass eaten. Phytophagous insects were the major component of the animal prey.These low magnitudes of energy flow and biomass consumption attest to the relatively minor role of birds in the processing of energy and biomass in grassland ecosystems. If these populations do play an importnat role in the functioning of grassland ecosystems, it must be quite subtle and indirect.     

Songs versus colours versus horns: what explains the diversity of sexually selected traits?

Papers on sexual selection often highlight the incredible diversity of sexually selected traits across animals. Yet, few studies have tried to explain why this diversity evolved. Animals use many different types of traits to attract mates and outcompete rivals, including colours, songs, and horns, but it remains unclear why, for example, some taxa have songs, others have colours, and others horns. Here, we first conduct a systematic survey of the basic diversity and distribution of different types of sexually selected signals and weapons across the animal Tree of Life. Based on this survey, we describe seven major patterns in trait diversity and distributions. We then discuss 10 unanswered questions raised by these patterns, and how they might be addressed. One major pattern is that most types of sexually selected signals and weapons are apparently absent from most animal phyla (88%), in contrast to the conventional wisdom that a diversity of sexually selected traits is present across animals. Furthermore, most trait diversity is clustered in Arthropoda and Chordata, but only within certain clades. Within these clades, many different types of traits have evolved, and many types appear to have evolved repeatedly. By contrast, other major arthropod and chordate clades appear to lack all or most trait types, and similar patterns are repeated at smaller phylogenetic scales (e.g. within insects). Although most research on sexual selection focuses on female choice, we find similar numbers of traits (among sampled species) are involved in male contests (44%) and female choice (55%). Overall, these patterns are largely unexplained and unexplored, as are many other fundamental questions about the evolution of these traits. We suggest that understanding the diversity of sexually selected traits may require a shift towards macroevolutionary studies at relatively deep timescales (e.g. tens to hundreds of millions of years ago).     

Molecular cross-talk between sponge host and associated microbes

Marine organisms especially those that live sessile, as sponges, are well known to have specific relationships with a great variety of microorganisms including bacteria and fungi. As most simple metazoan phylum, the Porifera, which emerged first during the transition from the non-Metazoa to the Metazoa from the common ancestor, comprise wide arrays of recognition molecules, both for Gram-negative bacteria and for Gram-positive bacteria as well as for fungi. They react specifically with effector molecules to inhibit or kill the invading microorganisms. The elicitation and the subsequent effector reactions of the sponges towards these microbes are outlined. However, besides of the elimination of bacteria and fungi, some of those taxa are kept as symbionts of the sponges, allowing them, for example, to accumulate the essential element manganese or to synthesize carotinoids. The sponges produce low-molecular-weight bioactive compounds, secondary metabolites, to eliminate the microorganisms. In addition, they are armed with cationic antimicrobial peptides allowing them to defend against invasive microorganisms and, in parallel, to kill or repel also metazoan invaders. The broad range of chemically and functionally different compounds qualifies the Porifera as the most important animal phylum to be exploited as a source for the isolation of new potential drugs. First molecular biological strategies have been outlined to obtain those compounds in a sustainable way, by producing them recombinantly.     

A synthetic biology approach for the fabrication of functional (fluorescent magnetic) bioorganic–inorganic hybrid materials in sponge primmorphs

During evolution, sponges (Porifera) have honed the genetic toolbox and biosynthetic mechanisms for the fabrication of siliceous skeletal components (spicules). Spicules carry a protein scaffold embedded within biogenic silica (biosilica) and feature an amazing range of optical, structural, and mechanical properties. Thus, it is tempting to explore the low-energy synthetic pathways of spiculogenesis for the fabrication of innovative hybrid materials. In this synthetic biology approach, the uptake of multifunctional nonbiogenic nanoparticles (fluorescent, superparamagnetic) by spicule-forming cells of bioreactor-cultivated sponge primmorphs provides access to spiculogenesis. The ingested nanoparticles were detected within intracellular vesicles resembling silicasomes (silica-rich cellular compartments) and as cytosolic clusters where they lent primmorphs fluorescent/magnetic properties. During spiculogenesis, the nanoparticles initially formed an incomplete layer around juvenile, intracellular spicules. In the mature, extracellular spicules the nanoparticles were densely arranged as a surface layer that rendered the resulting composite fluorescent and magnetic. By branching off the conventional route of solid-state materials synthesis under harsh conditions, a new pathway has been opened to a versatile platform that allows adding functionalities to growing spicules as templates in living cells, using nonbiogenic nanoscale building blocks with multiple functionalities. The magnet-assisted alignment renders this composite with its fluorescent/magnetic properties potentially suitable for application in biooptoelectronics and microelectronics (e.g., microscale on-chip waveguides for applications of optical detection and sensing).