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Parasite mediated competition facilitates invasion
  • Senay Yitbarek
Senay Yitbarek
University of California, Berkeley

Corresponding Author:senay@berkeley.edu

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Parasites  play an important role in invasion success with important consequences for  biodiversity and community structure. While much research has focused on direct  effects of parasites on biological invasions, parasites can also indirectly  influence interactions within the invaded community across trophic levels. For  instance, parasites can mediate competitive interactions between native and  exotic species through trait-mediated indirect effects. We consider the  interactions between the parasitoid fly Pseudacteon sp. (Diptera: Phoridae),  and its native host ant Linipethema  iniquum, and the exotic ant Wasmannia  auropunctata in the introduced range of Puerto Rico. We examined the  effects of phorid flies on the competitive outcome between the arboreal ants W. auropunctata and native ant L. iniquum. Furthermore, we investigate  the searching efficiency of phorid flies in detecting L. iniquum nests. To study the indirect effects on ant competition,  we monitored ant recruitment to baits over a 60-min time interval in the  presence and absence of phorid fly parasitoids. We then performed field  experiments and measured phorid arrival time to arboreal nests of L. iniquum located in both a) W. auropunctata patches and in b)  isolated patches dominated by L. iniquum  nests. We found that the presence of phorid fly significantly reduced  recruitment of L. iniquum workers to  baits through induced behavioral changes thereby increasing the ability of W. auropunctata to acquire resources. In  addition, we found that phorid arrival time in isolated patches of L. iniquum patches was faster as  compared to L. iniquum nests located  within W. auropunctata patches. Our  results show that phorid fly parasitoids indirectly may influence competitive  interactions by attacking the host-ant L.  iniquum and consequently providing an advantage to local spread of W. auropuntata populations in Puerto  Rico. However, the spatial dynamics of arboreal ants shows that L. iniquum seeks protection from phorid  fly parasotoids by moving their nests to W.  auropunctata dominated patches.