Craniometric Data Supports Demic Diffusion Model for the Spread of Agriculture into Europe

BACKGROUND:The spread of agriculture into Europe and the ancestry of the first European farmers have been subjects of debate and controversy among geneticists, archaeologists, linguists and anthropologists. Debates have centred on the extent to which the transition was associated with the active migration of people as opposed to the diffusion of cultural practices. Recent studies have shown that patterns of human cranial shape variation can be employed as a reliable proxy for the neutral genetic relationships of human populations. METHODOLOGY/PRINCIPAL FINDINGS:Here, we employ measurements of Mesolithic (hunter-gatherers) and Neolithic (farmers) crania from Southwest Asia and Europe to test several alternative population dispersal and hunter-farmer gene-flow models. We base our alternative hypothetical models on a null evolutionary model of isolation-by-geographic and temporal distance. Partial Mantel tests were used to assess the congruence between craniometric distance and each of the geographic model matrices, while controlling for temporal distance. Our results demonstrate that the craniometric data fit a model of continuous dispersal of people (and their genes) from Southwest Asia to Europe significantly better than a null model of cultural diffusion. CONCLUSIONS/SIGNIFICANCE:Therefore, this study does not support the assertion that farming in Europe solely involved the adoption of technologies and ideas from Southwest Asia by indigenous Mesolithic hunter-gatherers. Moreover, the results highlight the utility of craniometric data for assessing patterns of past population dispersal and gene flow

Restored Agricultural Wetlands in central Iowa: Habitat Quality and Amphibian Response

Amphibians are declining throughout the United States and worldwide due, partly, to habitat loss. Conservation practices on the landscape restore wetlands to denitrify tile drainage effluent and restore ecosystem services. Understanding how water quality, hydroperiod, predation, and disease affect amphibians in restored wetlands is central to maintaining healthy amphibian populations in the region. We examined the quality of amphibian habitat in restored wetlands relative to reference wetlands by comparing species richness, developmental stress, and adult leopard frog (Lithobates pipiens) survival probabilities to a suite of environmental metrics. Although measured habitat variables differed between restored and reference wetlands, differences appeared to have sub-lethal rather than lethal effects on resident amphibian populations. There were few differences in amphibian species richness and no difference in estimated survival probabilities between wetland types. Restored wetlands had more nitrate and alkaline pH, longer hydroperiods, and were deeper, whereas reference wetlands had more amphibian chytrid fungus zoospores in water samples and resident amphibians exhibited increased developmental stress. Restored and reference wetlands are both important components of the landscape in central Iowa and maintaining a complex of fish-free wetlands with a variety of hydroperiods will likely contribute to the persistence of amphibians in this landscape

Effects of Terrestrial Buffer Zones on Amphibians on Golf Courses

A major cause of amphibian declines worldwide is habitat destruction or alteration. Public green spaces, such as golf courses and parks, could serve as safe havens to curb the effects of habitat loss if managed in ways to bolster local amphibian communities. We reared larval Blanchard's cricket frogs (Acris blanchardi) and green frogs (Rana clamitans) in golf course ponds with and without 1 m terrestrial buffer zones, and released marked cricket frog metamorphs at the golf course ponds they were reared in. Larval survival of both species was affected by the presence of a buffer zone, with increased survival for cricket frogs and decreased survival for green frogs when reared in ponds with buffer zones. No marked cricket frog juveniles were recovered at any golf course pond in the following year, suggesting that most animals died or migrated. In a separate study, we released cricket frogs in a terrestrial pen and allowed them to choose between mown and unmown grass. Cricket frogs had a greater probability of using unmown versus mown grass. Our results suggest that incorporating buffer zones around ponds can offer suitable habitat for some amphibian species and can improve the quality of the aquatic environment for some sensitive local amphibians

Pulse Disturbance Impacts from a Rare Freeze Event in Tampa, Florida on the Exotic Invasive Cuban Treefrog, \u3cem\u3eOsteopilus Septentrionalis\u3c/em\u3e, and Native Treefrogs

This study documented exotic invasive Osteopilus septentrionalis and native treefrog use of artificial refugia in Tampa, Florida, USA, spanning approximately 3 years, with sampling from 1 year before and after (August 2008–November 2011) a record low temperature of −4 °C on January 11, 2010. Six pipes were inserted into the ground along the upland ecotone of 15 cypress domes located along a gradient of urban land use. Over 1000 treefrogs observations were made, with O. septentrionalis representing \u3e 70 % of total counts. Treefrog captures peaked in January–February 2009 and were temporally auto-correlated per site. O. septentrionalis counts declined following each freeze, and a fitted smoothing function for month indicated declines were cumulative, with a significant minimum in counts during the last freeze in February 2011. A concurrent seasonal peak in native treefrog counts led to a temporary loss of O. septentrionalis dominance from January to March 2011. Temperatures of −4 °C were sufficient to cause mortality of O. septentrionalis in PVC refugia; however, after autocorrelation was addressed no significant trend in native treefrogs was observed during the study. Multiseason occupancy models indicated probability of extinction for O. septentrionalis between freeze events did not differ significantly from native treefrogs, whereas a high probability of colonization between freeze events indicated O. septentrionalis may be resilient even to rare freezes. Trends in O. septentrionalis presence were not significant, and it was captured at 14/15 sites following the third freeze event, suggesting extirpation from freezing temperature may be unlikely for O. septentrionalis