lunes, 13 de julio de 2009

Research interest

Research interest

Ants interact with many other organisms through their feeding preferences, nesting and foraging activities: with plants, with honeydew-producing insects (aphids, whiteflies, scales, some butterfly larvae and mealybugs), with other insects and with microorganisms. In particular, ant species that tend honeydew-producing insects may change the abundance, diversity and fitness of those organisms involved in the interaction. My main interests are: how does the mutualism between ant species and honeydew-producing insects vary on time and space? How does the outcome of this mutualism change according to the particular species of tending ant and honeydew-producer involved? There are costs and benefits for each organism related, directly or indirectly, with the mutualistic interaction between tending ants and honeydew-producers (Fig 1). 

Fig. 1. This is a general overview of the mutualism between tending ants and honeydew producing insects (tended insects). Red arrows represent negative interactions towards the target organism, green arrows represent a positive interaction, and black arrows represent interactions that can be negative or neutral. The dotted violet arrow asks about the net effect (outcome) of ants on plants due their mutualism with tended insects. For detailed explanation see the text bellow.

       Usually, ants have a positive effect on honeydew producers’ abundance by protecting them against predators, parasitoids and providing them with hygienic services i.e. collecting honeydew stuck to its bodies. Although sometimes there is a cost of the fitness for the tended insect or even the ants prey them tended insects. As a consequence of this mutualism, sap consumption increases and fitness plant may be negatively affected. In some particular systems, ants may deter or prey herbibores from plants where they tend insects. This leads to a positive effect of ants on plants in spite they tend insects. The balance, between positives and negatives effects, of this mutualism will determinate the outcome for plants. This nest effect for plant is context- and species-dependant, and changes with time. Plant defences against tended insect and/or herbivores are costly and its production depends also on the net effect that tending ants have on plants.

      An extra question arises when a leaf cutting ant is the main herbivore of the arthropod community, because the two ant species would indirectly compete for their resource (i.e., the plant). Leaf cutting ants need the leaves to cultivate the fungi from which they feed, while tending ants need a healthy plant from which honeydew-producing insects can produce enough honeydew. So, what happens at the same plant species when leaf cutting ants meet an aggressive tending ant? Two general situations may appear when the main herbivore in the system is a leaf cutting ant and there are also tending ants (Fig 2).

The figure shows the two general situations that may appear when the main herbivores in the system are a leaf cutting ants. Red arrows represent negative interactions towards the target organism and green arrows represent positive interactions (dotted arrows represent indirect effect). For figure explanation please see text bellow.

   Both, ant species have positive and negative effects on plants. Leaf cutting ants indirectly increase soil nutrient content but, this effect occurs at a small-scale (in external o internal refused damp material). It had been demonstrated that plants growing close to nest or on external dump use these nutrients to increase its biomass and leaf quality compared with plants far away of the nest. On other hand, leaf cutting ants have a negative effect if we consider the herbivory of these ants. But, when the tending ant displaces leaf cutting ants the situation could become as the one showed in figure 1. The outcome for the herbivored plant will depend on the net effect of the mutualism between tending ants and honeydew producing insects and the net effect of the herbivory of leaf cutting ants.

     Additionally, I am strongly interested in ant taxonomy as a tool to put research of mutualism in a broader context by considering the composition of the whole ant community where these mutualisms develop. Taxonomy is also interesting because ants are good candidates for bioindicators of conservation stage in natural areas and of several processes such as soil restoration.

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