Dynamics and genetic structure of Argentine ant supercolonies in their native range.

Some introduced ant populations have an extraordinary social organization, called unicoloniality, whereby individuals mix freely within large supercolonies. We investigated whether this mode of social organization also exists in native populations of the Argentine ant Linepithema humile. Behavioral analyses revealed the presence of 11 supercolonies (width 1 to 515 m) over a 3-km transect. As in the introduced range, there was always strong aggression between but never within supercolonies. The genetic data were in perfect agreement with the behavioral tests, all nests being assigned to identical supercolonies with the different methods. There was strong genetic differentiation between supercolonies but no genetic differentiation among nests within supercolonies. We never found more than a single mitochondrial haplotype per supercolony, further supporting the view that supercolonies are closed breeding units. Genetic and chemical distances between supercolonies were positively correlated, but there were no other significant associations between geographic, genetic, chemical, and behavioral distances. A comparison of supercolonies sampled in 1999 and 2005 revealed a very high turnover, with about one-third of the supercolonies being replaced yearly. This dynamic is likely to involve strong competition between supercolonies and thus act as a potent selective force maintaining unicoloniality over evolutionary time.

Special report on the City of Norwalk for the period July 1, 2006 through April 9, 2008

Special report on the City of Norwalk for the period July 1, 2006 through April 9, 2008

Special report on the Woodbury County Sheriff’s Office for the period December 1, 2004 through December 31, 2007

Special report on the Woodbury County Sheriff’s Office for the period December 1, 2004 through December 31, 2007

Immigration, family responsibilities and the labor supply of skilled native women

This paper investigates the effects of Spain s large recent immigration wave on thelabor supply of highly skilled native women. We hypothesize that female immigration led to an increase in the supply of affordable household services, such as housekeeping and child or elderly care. As a result, i) native females with high earnings potential were able to increase their labor supply, and ii) the effects were larger on skilled women whose labor supply was heavily constrained by family responsibilities. Our evidence indicates that over the last decade immigration led to an important expansion in the size of the household services sector and to an increase in the labor supply of women in high-earning occupations (of about 2 hours per week). We also find that immigration allowed skilled native women to return to work sooner after childbirth, to stay in the workforce longer when having elderly dependents in the household, and to postpone retirement. Methodologically, we show that the availability of even limited Registry data makes it feasible to conduct the analysis using quarterly household survey data, as opposed to having to rely on the decennial Census.

Special investigation of the City of Searsboro for the period July 1, 2000 through October 9, 2006

Special investigation of the City of Searsboro for the period July 1, 2000 through October 9, 2006

Special investigation of the City of Grinnell Police Department for the period January 1, 2006 through April 30, 2008

Special investigation of the City of Grinnell Police Department for the period January 1, 2006 through April 30, 2008

Special investigation of the City of Vinton Parks and Recreation Department for the period July 19, 2001 through August 30, 2007

Special investigation of the City of Vinton Parks and Recreation Department for the period July 19, 2001 through August 30, 2007

Special investigation of selected transactions at Perry High School for the period July 1, 2005 through November 30, 2007

Special investigation of selected transactions at Perry High School for the period July 1, 2005 through November 30, 2007

Report on a special investigation of the West Marshall Community School District for the period January 1, 2001 through June 30, 2007

Report on a special investigation of the West Marshall Community School District for the period January 1, 2001 through June 30, 2007

Report on a special investigation of the City of Durant for the period July 1, 2000 through May 6, 2008

Report on a special investigation of the City of Durant for the period July 1, 2000 through May 6, 2008

Report on a special investigation of the City of Macedonia for the period June 26, 2006 through September 30, 2008

Report on a special investigation of the City of Macedonia for the period June 26, 2006 through September 30, 2008

Report on a special investigation of the City of Halbur for the period July 1, 1995 through June 30, 2008

Report on a special investigation of the City of Halbur for the period July 1, 1995 through June 30, 2008

Report on a special investigation of the Fairfield Parks and Recreation Department (Parks and Recreation) for the period January 1, 2007 through April 8, 2008

Report on a special investigation of the Fairfield Parks and Recreation Department (Parks and Recreation) for the period January 1, 2007 through April 8, 2008

Special investigation of the Cedar Rapids Veterans Memorial Commission and Valor, Inc. (Valor) for the period January 1, 2006 through October 31, 2007

Special investigation of the Cedar Rapids Veterans Memorial Commission and Valor, Inc. (Valor) for the period January 1, 2006 through October 31, 2007

Report on a special investigation of the Assistant Director of the Camp Adventure program at the University of Northern Iowa for the period January 1, 2006 through March 31, 2008

Report on a special investigation of the Assistant Director of the Camp Adventure program at the University of Northern Iowa for the period January 1, 2006 through March 31, 2008