Dietary shift drives patterns in trophic position and morphology of invasive African big-headed ant in habitat contrasts

Pheidole megacephala is a global widespread invasive species. It is also omnipresent in urban and forest ecosystem. This study aims to examine the feeding ecology and intraspecific trait variations that underlying their survival in urban ecosystems. δ¹³C and δ¹⁵N of ants were examined using stable isotope analysis. Four morphology traits, i.e., Weber’s length, head width, inter-eye distance and mid-femur length were measured to evaluated the morphology plasticity in both habitats. We found that the isotopic values of carbon and nitrogen did not display significant difference between April and October, indicating the types of diet intake by the ant in urban and peri-urban forest were consistent across seasons. Our results indicated that the values of δ¹⁵N was significant higher in urban compared with peri-urban forest. P. megacephala population in urban areas has an expanded diet range as indicated by the wide range of the δ¹³C value. These results suggested that man-made and insect-based food may be important nitrogen resources for ants in urban areas. All of the four morphological traits revealed significant higher values in urban areas. This was indicative of that ants form urban areas possess larger body size compared with peri-urban forest populations. Additionally, the urban ant populations had higher coefficient of variations of these morphological traits. In summary, our study provides an insight into local adaption strategy of invasive ant in urban ecosystems.