02852nas a2200169 4500008004100000245013300041210006900174260005200243490001000295520224200305653001802547653002602565653001302591653001802604100001902622856004102641 2014 eng d00aThe Effect of Soil Moisture on the Susceptibility to Invasion by the Argentine Ant (Linepithema humile) in Chaparral Communities0 aEffect of Soil Moisture on the Susceptibility to Invasion by the aSan Marcos, CaliforniabCSU San Marcosc04/20140 vPh.D.3 a

The Argentine ant (Linepithema humile) is a successful invasive species found throughout the world. It is commonly associated with urban areas and invades habitats that have favorable conditions, such as adequate moisture levels. Urban areas in the xeric regions of Southern California that use supplemental irrigation create artificially moist habitats that are thought to serve as a permanent refuge for the Argentine ant. Invasion is a three step process of introduction, establishment, and spread; for Argentine ants to invade, they must first be introduced to an area. This study was designed to determine if Argentine ants seasonally spread into habitats that have high soil moisture for only a portion of the year, and to access the role that soil moisture, seasonality, proximity to the urban edge, and proximity to a permanent water source play in determining which areas the Argentine ant will spread into, and where they are likely to successfully invade. This study examined three different habitat types on two reserves that differed in water availability: mesic (permanently wet), xeric (upland areas without a permanent water source), and seasonally moist (intermittently wet). Sampling cups were set out in each habitat during the wet and dry season for a period of two years. Measurements were taken on Argentine ant abundance, native ant species abundance, distance to the urban edge, and distance to a permanent water source. Argentine ants were found in mesic sites throughout the study period in both wet and dry seasons. No Argentine ants were found at the xeric sites in either wet or dry seasons. Out of six seasonally moist sites, one that was in close proximity to permanent water had Argentine ants year round, while the other seasonally moist sites had no Argentine ants. Distance to a permanent water source was the best predictor for Argentine ant abundance, followed by soil moisture. Seasonal spreading was not observed in any habitat type. Based on these findings, intermittent water does not seem to be a risk factor for Argentine ant invasion, but permanent water is a risk factor for invasion. Dry-season urban runoff will potentially lead to increased Argentine ant invasions in this region.

10aArgentine ant10achaparral communities10ainvasion10asoil moisture1 aSodeman, Brian uhttp://hdl.handle.net/10211.3/11937702523nas a2200205 4500008004100000022001400041245009100055210006900146300000900215490000700224520194000231653001102171653001302182653001802195653001302213653001802226653001602244100001802260856003902278 2014 eng d a1536-244200aQuantification of supercolonial traits in the yellow crazy ant, Anoplolepis gracilipes0 aQuantification of supercolonial traits in the yellow crazy ant A a1-210 v143 a

Supercoloniality is a social structure displayed by many invasive ant species, but there has been surprisingly little research quantifying the extent to which individual species display traits underlying such social organisation. This study quantifies three traits for the yellow crazy ant,Anoplolepis gracilipes Smith (Hymenoptera: Formicidae): little or no aggression between workers from different nests; the exchange of workers among nests; and resource exchange among nests, as well as supercolony structure arising from patterns of distribution and density of detections. Supercolonies displayed a structural continuum from being small (< 10 ha) and “aggregated” with great continuity among detections through to being large (> 10,000 ha) and “diffuse” with little continuity among detections. Smaller supercolonies had greater ant densities than larger supercolonies. In laboratory trials, no aggression was observed between workers from different nests sourced from different supercolonies, and paired nests merged within 24 hours. Workers lacked nest fidelity by rapidly populating artificial nests containing alien queens. The daily worker turnover rate per nest was estimated to be below 20%. Resources were readily moved among nests, with a resource being detected up to 13 m away from a source within 24 hours, and as far as 32 m after four days. The rate and distance of resource movement increased with increasing worker and nest density. This research has demonstrated that A. gracilipes displays supercoloniality equivalent to that of the well-studied Argentine ant Linepithema humile. Quantification of these traits is required for other supercolonial species to improve our understanding of this social strategy, especially for invasive ants to aid in understanding factors that promote invasion success and to improve management.

10acolony10ainvasion10anest fidelity10apolygyny10aresource flow10asupercolony1 aHoffmann, B D uhttp://www.insectscience.org/14.25