@article {33513, title = {Infiltration of a facultative ant{\textendash}plant mutualism by the introduced Argentine ant: effects on mutualist diversity and mutualism benefits}, journal = {Ecological Entomology}, year = {2015}, month = {Jan-04-2015}, pages = {n/a - n/a}, abstract = {

1. Ant\–plant mutualisms have been the focus of considerable empirical research, but few studies have investigated how introduced ants affect these interactions. Using 2\ years of survey data, this study examines how the introduced Argentine ant [Linepithema humile(Mayr)] differs from native ants with respect to its ability to protect the extrafloral nectary-bearing coast barrel cactus (Ferocactus viridescens) in Southern California.

2. Eighteen native ant species visited cacti in uninvaded areas, but cacti in invaded areas were primarily visited by the Argentine ant. The main herbivore of the coast barrel cactus present at the study sites is a leaf-footed bug (Narnia wilsoni).

3. Herbivore presence (the fraction of surveys in which leaf-footed bugs were present on individual cacti) was negatively related to ant presence (the fraction of surveys in which ants were present on individual cacti). Compared with cacti in uninvaded areas, those in invaded areas were less likely to have herbivores and when they did had them less often.

4. Seed mass was negatively related to herbivore presence, and this relationship did not differ for cacti in invaded areas versus those in uninvaded areas.

5. Although the Argentine ant might provide superior protection from herbivores, invasion-induced reductions in ant mutualist diversity could potentially compromise plant reproduction. The cumulative number of ant species on individual cacti over time was lower in invaded areas and was associated with a shortened seasonal duration of ant protection and reduced seed mass. These results support the hypothesis that multiple partners may enhance mutualism benefits.

}, keywords = {Ant{\textendash}plant interaction, cactus, extrafloral nectaries, facultative mutualism, herbivory, invasion, mutualist}, doi = {10.1111/een.12206}, url = {http://doi.wiley.com/10.1111/een.12206}, author = {LUDKA, JOHN and LEVAN, KATHERINE E. and Holway, David A.} } @article {33509, title = {Testing the effects of ant invasions on non-ant arthropods with high-resolution taxonomic data}, journal = {Ecological Applications}, year = {2015}, month = {Feb-03-2017}, pages = {150326212114006}, abstract = {

Invasions give rise to a wide range of ecological effects. Many invasions proceed without noticeable impacts on the resident biota, whereas others shift species composition and even alter ecosystem function. Ant invasions generate a broad spectrum of ecological effects, but controversy surrounds the extent of these impacts, especially with regard to how other arthropods are affected. This uncertainty in part results from the widespread use of low-resolution taxonomic data, which can mask the presence of other introduced species and make it difficult to isolate the effects of ant invasions on native species. Here, we use high-resolution taxonomic data to examine the effects of Argentine ant invasions on arthropods on Santa Cruz Island, California. We sampled arthropods in eight pairs of invaded and uninvaded plots and then collaborated with taxonomic experts to identify taxa in four focal groups: spiders, bark lice, beetles, and ants. Spiders, bark lice and beetles made up approximately 40\% of the 9868 non-ant arthropod individuals sampled; the majority of focal group arthropods were putatively native taxa. Although our results indicate strong negative effects of the Argentine ant on native ants, as is well documented, invaded and uninvaded plots did not differ with respect to the richness, abundance or species composition of spiders, bark lice and beetles. One common, introduced species of bark louse was more common in uninvaded plots than in invaded plots, and including this species into our analyses changed the relationship between bark louse richness versus L. humile abundance from no relationship to a significant negative relationship. This case illustrates how failure to differentiate native and introduced taxa can lead to erroneous conclusions about the effects of ant invasions. Our results caution against unqualified assertions about the effects of ant invasions on non-ant arthropods and more generally demonstrate that accurate assessments of invasion impacts depend on adequate information about species identity.

}, issn = {1051-0761}, doi = {10.1890/14-0952.1}, url = {http://www.esajournals.org/doi/10.1890/14-0952.1}, author = {Hanna, Cause and Naughton, Ida and Boser, Christina and Holway, David A.} }