Eucharitid ant-parasitoid affects facultative ant-plant Leea manillensis: top-down effects through three trophic levels

Abstract

Facultative ant-plant mutualisms are variable systems, shaped by a number of biotic and abiotic factors. Especially in tropical ecosystems, the generally assumed mutualistic benefits are often hard to prove. We studied the system Leea manillensis on the Philippine island Panay and its indirect defence mechanism against herbivory by producing extrafloral nectar therewith attracting ants. Unexpectedly, we found an ant-parasitoid wasp from the genus Chalcura (Eucharitidae) to have a strong influence on the system, on ants as well as on plants. The parasitoid not only altered the behaviour of interacting ant species, but also directly and indirectly affected the plants' fitness. This study demonstrates how top-down effects may alter species interactions and have a massive effect on mutualisms and their beneficial outcome.

Biology and phylogenetic placement of a new species of Lasiokapala Ashmead from Argentina (Hymenoptera: Eucharitidae)

“…We observed the proposed host, Ectatomma brunneum, on both the plant host and soil surrounding the plant. Recent studies by Schwitzke et al () in the genus Chalcura (Old World Chalcura clade) suggest that planidia may attack and kill adult ants visiting the host plant. They sampled a variety of ants on the plant, but none were the likely ponerine host.…”

Hitchhikers at the dinner table: a revisionary study of a group of ant parasitoids (Hymenoptera: Eucharitidae) specializing in the use of extrafloral nectaries for host access

“…If this is the case, a new hypothesis may be that planidia are using non-host ants as an intermediate prey host, similar to other Orasema that potentially use immature thrips or auchenorrynchous hemipterans as intermediate hosts which are taken to the brood as prey items (Clausen, 1940b;Das, 1963;Johnson et al, 1986;Heraty, 2000). It was recently proposed that eucharitid planidia from the genus Chalcura Kirby (Eucharitinae) attach to non-host ants and cause their death (Schwitzke et al, 2015). Orasema planidia could possibly be playing a part in the death of their intermediate ant host, and Pheidole are scavenging ants that planidia have killed.…”

“…These Kapala planidia are common in the mouth cavity (infrabuccal pocket) of foraging Ectatomma, and are probably carried directly to the host larva. A species of Chalcura (Eucharitinae) oviposits into stipules of Leea manillensis (Leeaceae) and planidia concentrate around the plant EFN (Schwitzke et al, 2015). Within Orasema, species can be associated with potential prey (immature thrips and auchenorrynchans), and a monophyletic group of Camponotus (Formicinae) parasitoids (Obeza Heraty and Lophyrocera Cameron) oviposit into fruit being collected by the ant hosts (Das, 1963;Kerrich, 1963;Heraty & Barber, 1990;Torréns, 2013).…”