The fate of Corydalis cava elaiosomes within an ant colony of Myrmica rubra: elaiosomes are preferentially fed to larvae

Abstract

The diaspores of many plant species are adapted to dispersal by ants (myrmecochory). The ants carry the diaspores into their nests where the appendages of the diaspores (elaiosomes) are consumed. Little is known, however, about the fate of diaspores in the colony, i.e., whether elaiosomes are consumed only by the larvae or also by the workers. In this study, the distribution of Corydalis cava (Fumariaceae) elaiosomes was monitored between the larvae and the working caste of laboratory colonies of Myrmica rubra (Formicidae, Myrmicinae). In the first part of the study, 15 N labelled elaiosomes were found to be mainly consumed by larvae. To find out whether elaiosomes are a more attractive food source than an artificial, nutritionally optimized diet for ants (Bhatkar diet), a combined 13 C and 15 N labelling experiment was conducted. Ants were offered 15 N labelled elaiosomes for two days (pulse labelling), while being continuously fed with 13 C labelled Bhatkar diet over 19 days. Under the given laboratory conditions, elaiosomes proved to be a far more attractive diet for the larvae than Bhatkar diet, contributing 87 ± 2 % of the daily nitrogen and 79 ± 3 % of daily carbon incorporation of larvae during the first four days of the experiment. The mean elaiosome incorporation met 73 ± 5 % of nitrogen and 63 ± 6% of carbon demand of workers during the first four days of the experiment. Generally, incorporation rates in workers (per dry body mass) were lower both for carbon and nitrogen during the experiment -by a factor of 6.8 for nitrogen and by a factor of 6.2 for carbon compared to larvae. On a colony basis, workers received 39 % and larvae 61 % of the elaiosome nitrogen. The results indicate that elaiosomes are a major food source for growing larvae and thus support the hypothesis that elaiosomes play an important role in the life cycle of temperate ants.

Ant-seed interactions: combined effects of ant and plant species on seed removal patterns

“…Indeed, benefits due to myrmecochory are far less known for ants. While more than two hundred papers tell us about plant benefits, only seven studies have shown so far that ants can benefit from elaiosomes by using them to feed their larvae (Handel, 1976;Morales and Heithaus, 1998;Bono and Heithaus, 2002;Fischer et al, 2005;Gammans et al, 2005;Marussich, 2006;Fokuhl et al, 2007) what may increase gynes production in some ant species (Morales and Heithaus, 1998) or increase larval weight (Gammans et al, 2005).…”

Stable N-isotope signatures of central European ants – assessing positions in a trophic gradient

“…While quite a number of stable isotope studies have been published for tropical ants (e.g., Fisher et al, 1990;Sagers et al, 2000;Fischer et al, 2002;Blüthgen et al, 2003;Davidson et al, 2003;Tillberg and Breed, 2004;Blüthgen et al, 2006), there is a surprising paucity of such investigations in the temperate zones (but see Fischer et al, 2005;Mooney and Tillberg, 2005;Platner, 2006;Tillberg et al, 2006). Moreover, based on in-depth analysis of intracolonial and intraspecific variation of N and C isotopes in temperate-zone ants, notes of caution have recently been sounded regarding the interpretation of stable isotope data in social insects in general (Tillberg et al, 2006).…”

Dispersal of non-myrmecochorous plants by a “keystone disperser” ant in a Mediterranean habitat reveals asymmetric interdependence

“…This appendage elicits ants to transport the elaiosomebearing diaspores back to their nest. After it has been consumed mostly by the larvae (Fischer et al, 2005), the ants discard the intact seed with other food remains. By transporting the vulnerable seeds soon after their release, ants allow plants to colonize new habitats (Gorb and Gorb, 2003), reduce intraspecific competition and decrease mortality by predation and fire (Heithaus, 1981;Bond and Slingsby, 1984;Hughes and Westoby, 1992;Boulay et al, 2007aBoulay et al, , 2009a.…”