Story ideas from the Proceedings of the National Academy of Sciences

ARTICLE HIGHLIGHTS

• Determining dinosaur diets from fossil teeth
• Desert dust changes climate cues for mountain plants
• Hunger hormone may affect alcohol dependence

ALSO OF INTEREST

• Hungry, hungry hybrids
• Overestimating fishery evolution

Researchers have reconstructed the eating habits of the duck-billed dinosaur Edmontosaurus from patterns of scratches and wear on its fossil teeth. From these markings, Mark Purnell and colleagues determined that Edmontosaurus grazed on low-growing vegetation, as opposed to browsing on woody twigs and leaves. Dinosaurs like the plant-eating Edmontosaurus were some of the largest vertebrates during the Late Cretaceous period, and their foraging success has been attributed to the structure of their skull which allowed them, unlike most dinosaurs, to chew and grind their food. Although fossil vertebrate teeth can provide some dietary clues, it remains unclear exactly what types of food Edmontosaurus ate and how they chewed it. The researchers found that scratches on Edmontosaurus teeth indicated mainly up and down jaw movements, as well as some forward and back movements. This supports the view that there was a flexible hinge in the dinosaur's skull, and the scratch pattern indicates tightly controlled chewing motions. Although the fossil teeth are covered in scratches, they have no pits or chips, indicative of a pattern of wear that in living herbivores is characteristic of animals that graze on grasses, according to the authors.

Article #08-12631: "Quantitative analysis of dental microwear in hadrosaurid dinosaurs, and the implications for hypotheses of jaw mechanics and feeding," by Vincent Williams, Paul Barrett, and Mark Purnell

MEDIA CONTACT: Mark Purnell, Department of Geology, University of Leicester, Leicester, UNITED KINGDOM; tel: +44-116-252-3645; e-mail: map2@leicester.ac.uk

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Desert dust blown onto mountains may change how plants respond to climate cues that regulate their life cycles, researchers have found. Mountain dust levels have been increasing since the 19th century, largely due to increased human activity in the deserts. Heidi Steltzer and colleagues simulated dust effects on snowmelt in experimental plots in the Rocky Mountains in Colorado to measure dust's effect on the life cycles of alpine plants. Under normal conditions, the timing of snowmelt signals mountain plants to start growing and flowering. However, dust absorbs heat that pristine snow would otherwise reflect, thus enhancing the heating effect from sunlight and causing early snowmelt. This early snowmelt may lead to plants delaying their annual growth cycle until air temperatures warm. The authors predict that increasing amounts of dust could synchronize the greening and flowering times in the alpine tundra and potentially alter species interactions and nutrient cycling by influencing the availability of resources for pollinators and wildlife. Their results indicate that human changes in desert landscapes are linked to plant life cycles in the mountains, according to the authors.

Article #09-00758: "Biological consequences of earlier snowmelt from desert dust deposition in alpine landscapes" by Heidi Steltzer, Chris Landry, Thomas H. Painter, Justin Anderson, and Edward Ayres

MEDIA CONTACT: Heidi Steltzer, Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO; tel: 970-491-1565 (day), 970-494-0857 (evening), e-mail: steltzer@nrel.colostate.edu

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Ghrelin, a hormone produced in the stomach that helps induce hunger, may also play a role in the development of alcohol dependence. Elisabet Jerlhag and colleagues found that ghrelin administration to mice led to increased alcohol consumption, whereas blocking the action of ghrelin lowered alcohol intake. Previous research identified the presence of ghrelin receptors in specific areas of the brain important in recognizing reward. Because these mechanisms appear to mediate food and alcohol reward, the authors hypothesized that ghrelin might also mediate alcohol dependence. Direct administration of ghrelin into brain reward nodes of mice increased their alcohol consumption by approximately 45 percent compared to mice that received a saline solution. Alcohol consumption also declined when the authors administered either one of two compounds that interfered with ghrelin signaling. Mice with lower ghrelin signaling seemed less responsive to alcohol's reward properties because their brains produced less dopamine, according to the researchers. These rewarding effects of alcohol form an intimate part of the addiction process, and the ghrelin system provides a novel target for therapies, the authors conclude.

Article #08-12809: "Requirement of central ghrelin signaling for alcohol reward," by Elisabet Jerlhag, Emil Egecioglu, Sara Landgren, Nicolas Salomé, Markus Heilig, Diederik Moechars, Rakesh Datta, Daniel Perrissoud, Suzanne Dickson, and Jörgen Engel

MEDIA CONTACT: Elisabet Jerlhag, Department of Pharmacology, Institute for Neuroscience and Physiology, Göteborg, SWEDEN; tel: +46-31-786-3418; e-mail: elisabet.jerlhag@pharm.gu.se

Hungry, hungry hybrids

Hybrids of the native, threatened California Tiger Salamander and the introduced Barred Tiger Salamander have become major predators of pond-breeding species such as frogs and newts.

Article #09-02252: "Ecological consequences of introduced genes: Invasive tiger salamander genotypes impact native amphibians," by Maureen Ryan, Jarrett Johnson, and Benjamin Fitzpatrick

MEDIA CONTACT: Maureen Ryan, Department of Evolution and Ecology, University of California, Davis, CA; tel: 530-304-2266; e-mail: meryan@ucdavis.edu

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Commercial fisheries may not spur fish evolution as quickly as predicted by earlier studies.

Article #09-01690: "Expected rate of fisheries-induced evolution is slow," by Ken Andersen and Keith Brander

MEDIA CONTACT: Ken Andersen, National Institute of Aquatic Resources, Technical University of Denmark, Charlottenlund, DENMARK; tel: +45-3396-3340; e-mail: kha@aqua.dtu.dk