D3162: The recent invasion of southern California by the big-headed ant (Pheidole megacephala): Implications for future expansion

Monday, November 11, 2024

9:00 AM – 5:00 PM MST

Location: Phoenix Convention Center, Exhibit Hall 6, PCC

Presenting Author(s)

Mandy Frazer, M.S.

Early Career Entomologist
Recent UC San Diego Grad
Lakeside, California

Co-Author(s)

DH

David A. Holway

University of California
La Jolla, California

The big-headed ant, Pheidole megacephala, is an ecologically destructive invader of tropical and subtropical environments worldwide. In April 2014 an established infestation of P. megacephala was discovered in a residential neighborhood in Costa Mesa, Orange County, and a second infestation was found in a residential neighborhood in San Diego, San Diego County in 2019. Although big-headed ants are regularly detected in commerce in California, the records from Costa Mesa and San Diego represent the first known established infestations in the state. To learn more about the distribution of P. megacephala in California and to assess its potential for further spread, we delineated both known infestations and compared this species to another widespread invader, the Argentine ant (Linepithema humile) with respect to desiccation tolerance and trophic position. Both known P. megacephala infestations extend over multiple hectares of suburban development, with the San Diego infestation exceeding 100 ha and the Costa Mesa infestation exceeding 10 ha. Both infestations are spatially continuous and encompassed by established populations of the Argentine ant. The big-headed ant overlapped broadly with the Argentine ant both in terms of desiccation tolerance and trophic position (𝛿15N). These similarities suggest that the big-headed ant could continue to spread in urban environments in coastal southern California and impact these areas to a degree comparable to impacts resulting from invasion by the Argentine ant.