Evol Ecol Res 18: 323-333 (2017)     Full PDF if your library subscribes.

Weaver ants shift nest location in response to the selective pressures
of habitat disturbance and torrential rain in Sri Lanka

Leonard A. Freed¹ and Dulan R. Vidanapathirana²

¹Department of Biology, University of Hawaii at Manoa, Honolulu, Hawaii, USA and ²Herpetological Foundation of Sri Lanka, Wattala, Sri Lanka

Correspondence: L.A. Freed, Department of Biology, University of Hawaii at Manoa, Honolulu, HI 96822, USA. email: lfreed@hawaii.edu

ABSTRACT

Background: Weaver ants in central Sri Lanka endure two monsoon seasons per year and mowing of the understory in coconut palm plantations.

Hypothesis: Mowing of the understory and torrential rain represent selective pressures.

Organisms: Weaver ants (Oecophylla smaragdina).

Field sites: Two coconut palm (Cocos nucifera) plantations.

Methods: We documented mowing in June as one selective pressure, and torrential rain in October to December as the second selective pressure. One farmer postponed mowing by a month, although he had mowed in June in previous years. We tagged understory plants and trees and counted weaver ant nests.

Results: Weaver ants suffer nest losses on understory plants but not on trees due to torrential rain. We documented movement onto coconut palms the month before mowing even when not mowed. Altogether, 145 out of 326 palms had weaver ants; 60 of these 145 palms had active ant nests less than 2 m away, suggesting polydomy.

Conclusions: Mowing the understory is a human-caused selective pressure. Torrential rain is a natural selective pressure. The movement of the ants under protective foliage in trees protects their nests because trees are not mowed. This movement enables the ants to persist in the plantations.

Keywords: habitat disturbance, switch in nest sites, torrential rain, weaver ants.

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