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Selected AbstractsLate Devonian tetrapod remains from Red Hill, Pennsylvania, USA: how much diversity?ACTA ZOOLOGICA, Issue 2009Edward B. Daeschler Abstract The remains of Late Devonian tetrapods from the Red Hill locality in Pennsylvania help to elucidate the early stages of tetrapod evolution. Red Hill is a particularly informative site that preserves a diverse fauna and flora within a depositional setting suggesting penecontemporaneous deposition of locally derived material. Here, for the first time, we report on the full suite of early tetrapod remains from Red Hill and consider the implications for tetrapod diversity within the Red Hill ecosystem. Previously described material is reviewed and considered in relation to newly reported specimens. New material described includes isolated skull elements (two jugals, a postorbital, a lacrimal and a coronoid) and postcranial elements (a femur and a gastral scale). The characteristics of many of the Red Hill tetrapod specimens conform to the morphological expectations of Late Devonian forms. Several elements, however, illustrate more derived characteristics and strongly suggest the presence of the oldest known whatcheeriid-like tetrapod. This study demonstrates the difficulty in making taxonomic associations with isolated remains, even when found in close proximity to one another. Exploration of the characteristics of each element, however, demonstrates the presence of at least three early tetrapod taxa at the Red Hill site. [source] Environmental epigenomics in human health and diseaseENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 1 2008Dana C. Dolinoy Abstract The epigenome consists of the DNA methylation marks and histone modifications involved in controlling gene expression. It is accurately reproduced during mitosis and can be inherited transgenerationally. The innate plasticity of the epigenome also enables it to be reprogrammed by nutritional, chemical, and physical factors. Imprinted genes and metastable epialleles represent two classes of genes that are particularly susceptible to environmental factors because their regulation is tightly linked to epigenetic mechanisms. To fully understand the etiology of the most devastating diseases that plague humans, the full complexity of the human epigenome will ultimately need to be characterized. Moreover, the elucidation of the interaction of the environment with the epigenome should allow for the development of novel epigenetic-based diagnostic, prevention, and therapeutic strategies for human diseases. Herein, we introduce the emerging field of environmental epigenomics, discuss the importance of imprinted genes and metastable epialleles as epigenetically labile genomic targets, and endorse the genome-wide identification of the full suite of epigenetically labile targets in both the mouse and human genomes. Environ. Mol. Mutagen., 2008. © 2008 Wiley-Liss, Inc. [source] Nutritional ecology and diachronic trends in Paleolithic diet and healthEVOLUTIONARY ANTHROPOLOGY, Issue 5 2003Bryan Hockett Modern nutritional studies have found that diverse diets are linked to lower infant mortality rates and longer life expectancies in humans. This is primarily because humans require more than fifty essential nutrients for growth and cell maintenance and repair; most of these essential nutrients must come from outside food sources rather than being manufactured by the body itself; and a diversity of food types is required to consume the full suite of essential nutrients necessary for optimal human health. These principles and their related affects on human adaptations and demography are the hallmarks of a theoretical paradigm defined as nutritional ecology. This essay applies concepts derived from nutritional ecology to the study of human evolution. Principles of nutritional ecology are applied to the study of the Middle-to-Upper Paleolithic transition in order to broadly illustrate the interpretive ramifications of this approach. At any stage in human evolution, those hominid populations that chose to diversify their subsistence base may have had a selective advantage over competitors who restricted their diet principally to one food type, such as terrestrial mammals. [source] Interpreting the smells of predation: how alarm cues and kairomones induce different prey defencesFUNCTIONAL ECOLOGY, Issue 6 2009Nancy M. Schoeppner Summary 1.,For phenotypically plastic organisms to produce phenotypes that are well matched to their environment, they must acquire information about their environment. For inducible defences, cues from damaged prey and cues from predators both have the potential to provide important information, yet we know little about the relative importance of these separate sources of information for behavioural and morphological defences. We also do not know the point during a predation event at which kairomones are produced, i.e. whether they are produced constitutively, during prey attack or during prey digestion. 2.,We exposed leopard frog tadpoles (Rana pipiens) to nine predator cue treatments involving several combinations of cues from damaged conspecifics or heterospecifics, starved predators, predators only chewing prey, predators only digesting prey or predators chewing and digesting prey. 3.,We quantified two behavioural defences. Tadpole hiding behaviour was induced only by cues from crushed tadpoles. Reduced tadpole activity was induced only by cues from predators digesting tadpoles or predators chewing + digesting tadpoles. 4.,We also quantified tadpole mass and two size-adjusted morphological traits that are known to be phenotypically plastic. Mass was unaffected by the cue treatments. Relative body length was affected (i.e. there were differences among some treatments), but none of the treatments significantly differed from the no-predator control. Relative tail depth was affected by the treatments and deeper tails were induced only when tadpoles were exposed to cues from predators digesting tadpoles or cues from predators chewing + digesting tadpoles. 5.,These results demonstrate that some prey species can discriminate among a diverse set of potential cues from heterospecific prey, conspecific prey and predators. Moreover, the results illustrate that the cues responsible for the full suite of behavioural and morphological defences are not induced by tadpole crushing nor can they be induced by generalized digestive chemicals produced when predators digest their prey. Instead, both prey damage and predator digestion of conspecific tissues appear to be important for communicating predatory risk to phenotypically plastic anuran prey. Importantly, the production of chemical cues by predators may be unavoidable and prey have evolved the ability to eavesdrop on these signals. [source] Twenty years of rest returns grazing potential, but not palatable plant diversity, to Karoo rangeland, South AfricaJOURNAL OF APPLIED ECOLOGY, Issue 4 2010Colleen L. Seymour Summary 1.,Up to 73% of the world's rangelands are degraded, and increasing demand for meat in developing countries and a growing human population are likely to exert even greater pressures on rangelands in the next 20,50 years. Restoration of rangeland grazing potential and resilience is therefore important, particularly in the face of climate change. 2.,We investigated the influence of past stocking rates (from 1910 to 1987), rainfall, and current grazing regimes (from 1988 to 2008) on plant assemblages, grazing potential, and diversity of palatable species in southern Karoo rangelands, South Africa. 3.,We used herbivore exclusion experiments to test whether resting rangeland for 20 years enables recovery of plant assemblages (where seed sources are present within 50 m), regardless of previous grazing history. Mean annual rainfall over this period was 15% higher than the mean annual rainfall for the preceding 80 years and included two exceptionally wet years. 4.,While rainfall was a primary driver of total vegetation cover, grazing history explained differences in plant species composition: plots with shared historical grazing intensity were more similar than plots with the same grazing regimes between 1988 and 2008. 5.,In historically heavily-grazed exclusion plots, cover of the palatable species Tripteris sinuata (formerly Osteospermum sinuatum) returned to levels comparable to that in both exclusion and lightly-grazed plots with a moderate grazing history. Five palatable species (Pteronia empetrifolia, Tetragonia spicata, Berkheya spinosa, Hereroa latipetala and Ruschia spinosa) failed to re-establish, however, despite the presence of seed-producing plants nearby. Furthermore, only cover of P. empetrifolia increased significantly in historically moderately-grazed plots. Cover of unpalatable plants (e.g. Pteronia pallens) increased in all plots over time. 6.Synthesis and applications. These findings suggest that present species composition of arid shrublands reflects historical management at time scales greater than 20 years. Despite high rainfall enabling the return of grazing potential through recovery of a single forage species, rest alone did not ensure the return of all palatable species, with implications for rangeland resilience. Restoring the full suite of palatable species over management timeframes will require more complex interventions such as reseeding or selective clearing. [source] Support for a metapopulation structure among mammalsMAMMAL REVIEW, Issue 3 2009PIETER I. OLIVIER ABSTRACT 1The metapopulation metaphor is increasingly used to explain the spatial dynamics of animal populations. However, metapopulation structure is difficult to identify in long-lived species that are widely distributed in stochastic environments, where they can resist extinctions. The literature on mammals may not provide supporting evidence for classic metapopulation dynamics, which call for the availability of discrete habitat patches, asynchrony in local population dynamics, evidence for extinction and colonization processes, and dispersal between local populations. 2Empirical evidence for metapopulation structure among mammals may exist when applying more lenient criteria. To meet these criteria, mammals should live in landscapes as discrete local breeding populations, and their demography should be asynchronous. 3We examined the literature for empirical evidence in support of the classical criteria set by Hanski (1999), and for the more lenient subset of criteria proposed by Elmhagen & Angerbjörn (2001). We suggest circumstances where metapopulation theory could be important in understanding population processes in mammals of different body sizes. 4The patchy distribution of large (>100 kg) mammals and dispersal often motivate inferences in support of a metapopulation structure. Published studies seldom address the full suite of classical criteria. However, studies on small mammals are more likely to record classic metapopulation criteria than those on large mammals. The slow turnover rate that is typical for medium-sized and large mammals apparently makes it difficult to identify a metapopulation structure during studies of short duration. 5To identify a metapopulation structure, studies should combine the criteria set by Hanski (1999) and Elmhagen & Angerbjörn (2001). Mammals frequently live in fragmented landscapes, and processes involved in the maintenance of a metapopulation structure should be considered in conservation planning and management. [source] Early ontogenetic trajectories vary among defence chemicals in seedlings of a fast-growing eucalyptAUSTRAL ECOLOGY, Issue 2 2010CLARE MCARTHUR Abstract Ontogenetic changes in leaf chemistry can affect plant,herbivore interactions profoundly. Various theoretical models predict different ontogenetic trajectories of defence chemicals. Empirical tests do not consistently support one model. In Eucalyptus nitens, a fast-growing tree, we assessed early developmental changes to seedlings, in foliage concentrations of nitrogen and the full suite of known secondary (defence) chemicals. This included the terpene, ,-pinene, whose impact on marsupial herbivory is unknown. To test for the influence of abiotic conditions on the ontogenetic trajectories we overlaid a nutrient treatment. Ontogenetic trajectories varied among compounds. Sideroxylonals and cineole were barely detected in very young seedlings, but increased substantially over the first 200 days. Total phenolic concentration increased fourfold over this time. In contrast, ,-pinene concentration peaked within the first 60 days and again between 150 and 200 days. Nutrients altered the degree but not the direction of change of most chemicals. A shorter trial run at a different season showed qualitatively similar patterns, although ,-pinene concentration started very high. We investigated the effect of detected levels of ,-pinene and cineole on food intake by two mammalian herbivores, common brushtail possums (Trichosurus vulpecula) and red-bellied pademelons (Thylogale billardierii). Under no-choice conditions neither terpene reduced intake; but with a choice, possums preferred ,-pinene to cineole. The ontogenetic trajectories of most compounds were therefore consistent with models that predict an increase as plants develop. Published data from later developmental stages in E. nitens also confirm this pattern. ,-Pinene, however, was the only secondary compound found at significant levels in very young seedlings; but it did not constrain feeding by marsupial herbivores. Models must allow for different roles of defensive secondary chemicals, presumably associated with different selective pressures as plants age, which result in different ontogenetic trajectories. [source] | |||||||||||||||||||