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Oxygen limitation has been proposed as one of the key factors that limits body size at high temperatures (the oxygen-temperature hypothesis). Geographic patterns in body size are thought to be driven in part by the effects of temperature on oxygen supply and demand, particularly when the increased oxygen demand of tissues at higher temperatures outpaces the ability of large organisms to supply internal tissues with oxygen. We tested the effects of temperature on the rate of oxygen consumption of two temperate sea spider (Pycnogonida) species, Achelia chelata and Achelia gracilipes, across a range of body sizes. We measured oxygen consumption at 5 temperatures: 12, 16, 20, 24, and 28 [degrees]C. Oxygen consumption of both species increased significantly with temperature, but the effect did not depend on body size; thus, we found no evidence to support the oxygen-temperature hypothesis. While previous interspecific studies on Antarctic pycnogonids have found that larger-bodied animals have more porous cuticles, thus potentially offsetting their higher aerobic metabolic demand by increasing oxygen diffusivity, the pore area of the cuticle of the two temperate species did not change with body size. This suggests that the generally small size of warm-water sea spiders may be due to selective factors other than oxygen limitation., Introduction Almost all aspects of an organism's physiology are influenced by body size (Kingsolver and Huey, 2008). As a result, the physiological and environmental factors that underlie evolutionary or acclimatory [...]

A study published in Functional Ecology explores the constraints on the dispersal of forest-dwelling tropical birds. The researchers found that species with long, slender, and pointed wings, as well as proportionally small eyes, were better able to fly across open habitats. The study also revealed that environmental filtering played a role in shaping the phenotypes of bird species in fragmented forests. The findings highlight the need for further research on the biomechanical and physiological mechanisms that affect dispersal ability in tropical birds. [Extracted from the article]

The evolution of nest site use and nest architecture in the non-avian ancestors of birds remains poorly understood because nest structures do not preserve well as fossils. Nevertheless, the evidence suggests that the earliest dinosaurs probably buried eggs below ground and covered them with soil so that heat from the substrate fuelled embryo development, while some later dinosaurs laid partially exposed clutches where adults incubated them and protected them from predators and parasites. The nests of euornithine birds—the precursors to modern birds—were probably partially open and the neornithine birds—or modern birds—were probably the first to build fully exposed nests. The shift towards smaller, open cup nests has been accompanied by shifts in reproductive traits, with female birds having one functioning ovary in contrast to the two ovaries of crocodilians and many non-avian dinosaurs. The evolutionary trend among extant birds and their ancestors has been toward the evolution of greater cognitive abilities to construct in a wider diversity of sites and providing more care for significantly fewer, increasingly altricial, offspring. The highly derived passerines reflect this pattern with many species building small, architecturally complex nests in open sites and investing significant care into altricial young. This article is part of the theme issue 'The evolutionary ecology of nests: a cross-taxon approach'. [ABSTRACT FROM AUTHOR]