Concerted evolution of body mass and cell size: similar patterns among species of birds (Galliformes) and mammals (Rodentia).

Cell size plays a role in body size evolution and environmental adaptations. Addressing these roles, we studied body mass and cell size in Galliformes birds and Rodentia mammals, and collected published data on their genome sizes. In birds, we measured erythrocyte nuclei and basal metabolic rates (BMRs). In birds and mammals, larger species consistently evolved larger cells for five cell types (erythrocytes, enterocytes, chondrocytes, skin epithelial cells, and kidney proximal tubule cells) and evolved smaller hepatocytes. We found no evidence that cell size differences originated through genome size changes. We conclude that the organism-wide coordination of cell size changes might be an evolutionarily conservative characteristic, and the convergent evolutionary body size and cell size changes in Galliformes and Rodentia suggest the adaptive significance of cell size. Recent theory predicts that species evolving larger cells waste less energy on tissue maintenance but have reduced capacities to deliver oxygen to mitochondria and metabolize resources. Indeed, birds with larger size of the abovementioned cell types and smaller hepatocytes have evolved lower mass-specific BMRs. We propose that the inconsistent pattern in hepatocytes derives from the efficient delivery system to hepatocytes, combined with their intense involvement in supracellular function and anabolic activity.

Functioning grouped soil microbial communities according to ecosystem type, based on comparison of fallows and meadows in the same region.

Predicting the composition and function of microbial communities at a bio-geographical scale, across ecosystems, is challenging. We compared six abandoned fields to six meadows to see whether soil microbial community structure and activity are more similar within the ecosystem type than between the types. We implemented bacteria and fungi phylogenetic markers profiling, phospholipids analysis, fluorescence counts of total bacteria and algae and microscopy of arbuscular mycorrhizal fungi (AMF). The functional performance of microbial communities was assessed using enzymes activity measurements as well as culturing and incubation experiments. The studied fallows and meadows had similar biomass and general structure of soil microbial communities. However, the AMF root colonization frequency was higher in the meadows than in the fallows. The AMF colonization was promoted in meadows characterised by lower availability of NO3-, P and K as well as higher soil pH, which additionally hampered plant acquisition of P at the P-limited ecosystem. Fallow and meadow microbial communities showed characteristic functional traits. Meadow soils exhibited higher basal respiration rate, while cellulose decomposition and nitrogen mineralization were faster in fallows. Even when no major differences in community structure could have been detected soil microbial communities adapted to local and/or instantaneous environmental conditions and formed functionally-specific ecotypes. This work points out the relevance of preserving meadows as reservoirs of plant diversity, which cope excellent in nutrient depleted conditions and in mountain regions thanks to microbial components of ecosystem.

Automated measurement of ommatidia in the compound eyes of beetles.

The size of the ommatidia that compose the insect compound eye is linked to visual capacity, physiological performance, and cell size. Therefore, rapid and reliable methods for measuring ommatidia can advance research on insect ecology and evolution. We developed an automated method to measure ommatidia in nail polish imprints of the eyes of three Carabidae beetle species using the widely available, free software ImageJ. Our automated method was equivalent to a traditional manual method in terms of accuracy but had the advantage of being 70 times faster. We provide access to our algorithm, which can be used to investigate biological phenomena ranging from the functional architecture of the compound eye to the cellular basis of the evolution of body size and metabolic rates.

How to time growth and reproduction during the vegetative season: an evolutionary choice for indeterminate growers in seasonal environments.

Indeterminate growers such as plants, mollusks, fish, amphibians, and reptiles are highly diversified with respect to the seasonal timing of growth and reproduction. Current life-history theory does not offer a consistent view on the origin of this diversity. We use dynamic optimization to examine resource allocation in seasonal environments, considering that offspring produced at different times of the season have unequal future prospects. Reduction of these prospects during the season produced indeterminate growers that grew mostly after maturation, achieving large final body sizes. It also changed the optimal timing of growth and reproduction during a season, from grow-first-reproduce-later, as usually predicted by life-history theory, to the reproduce-first-grow-later tactic; other tactics were produced by the interactive effects of winter survival and unequal offspring prospects. The results suggest that devaluation of offspring production provides conditions for the evolution of capital breeding, even in fully predictable seasonal environments. Thus, the unequal fate of newborns from different parts of a season may explain the origin of diversity of reproductive phenologies, growth patterns, and capital breeding in nature.