Does the execution of gynes by Linepithema humile? workers, also happens at its native area?

SILVIA ABRIL; CAROLINA PARIS; DIEGO SHALOM; SOL BIROLO

Buenos Aires

Congreso; I Reunión de Biología del Comportamiento del Cono Sur; 2017

In the last 37 years the invasive ant, Linepithema humile, was extensively studied. Surprisingly, its life cycle was only studied at invaded areas. There, it was reported that during spring workers execute 90% of gynes (= reproductive females) of its highly polygynous colonies. We wondered if this behavior happens at the native area. To answer this, every month at Natural Reserve of Otamendi, we counted all gynes and males of 2L of soil (n= 4 nests). Workers, larvae and pupae were counted from a subsample of 200g of soil. Larvae appeared among all months except on June and peaked on September. As in previous studies at invaded areas, male pupae appeared only in spring, one month before gynes pupae were found. On June, the proportion of gynes per 1000 workers, an index of colony investment in reproduction, rises probably as consequence of nest regrouping at the beginning of winter. However, this index dropped to less than one in the following winter months, to rise 9 times at the beginning of spring. At middle spring, this index dropped drastically, from 6.06 to 1.61 to slightly rise again at the end of spring and summer. At this moment, we found that gyne pupae peaked and found several virgin gynes. Our results suggest that Linepithema humile workers also execute theis gynes at the native area, as gyne/worker proportion followed previous reported pattern at invaded area. Apparently, this behavior was not an adaptation to an invasive context as it was suggested up to know.