Exploiter

∞ generated and posted on 2016.12.15 ∞

Organism that gains fitness advantages at the expense of other organisms.

In terms of interspecific interactions, exploiters can be predators, parasites, pathogens, herbivores, etc. The exploited organism is the victim.

Exploiter-victim interactions can be viewed as plus-minus, that is, the exploiter gains while the victim loses. This contrasts with, for example, the plus-zero interactions one sees with a commensal relationship, which also can occur between two organisms, that is, where one organism gains but the other organism neither loses nor gains. It also contrasts with mutualisms which instead may be classified as plus-plus for each of the two or more individuals involved in the relationship.

Plus and minus designations often are described in terms of organism fitness though this is not necessarily essential to the idea nor reflecting longer-term versus shorter-term fitness considerations (such as parasitic interactions that lead to evolutionary dead ends for the parasite but nonetheless are beneficial to the parasite more immediately). In addition, surrogates for fitness can be used, and done so especially for sake of convenience. For example, whether one of the organisms in these relationships is gaining more or less food given the relationship, where food is the surrogate indicator, versus necessarily producing more or fewer progeny, which is closer to the concept of Darwinian fitness.

Figure legend: Exploiters gain from ecological interactions with victims. Most fundamentally those gains can be measured in terms of increases in the Darwinian fitness of the exploiter, that is, in terms of the number of offspring that are produced and which survive to produce offspring of their own. Similarly, the victims, in exploiter-victim interactions, are the individuals that lose from the interaction, particularly in terms of the victim's Darwinian fitness. These sorts of ecological relationships between organisms are most prominently though not exclusively seen with predator-prey interactions since the prey, by definition, die, while the predator gains a meal.

To be successful in exploiting, generally an exploiter must first identify in some manner a potential victim. That victim then must be 'captured', which, e.g., for a parasite could mean attached to or attached to in an appropriate location on or in the victim. Victim 'handling' must then ensue, with the 'handling time' being the duration that the victim is exploited over the course of the interaction. Subsequently, a post-exploitation interval can occur, such as that associated with digestion, though more generally this is a wait during which the exploiter is either not-yet able or less able to resume these four steps and/or otherwise is assimilating the 'spoils' of its exploitation.

Exploitation can result in coevolutionary interactions where a victim's exploitation-interfering adaptations can be countered by adaptations on the part of exploiters and vice versa. Of course, victim-exploiter interactions also can occur in the course of intraspecific interactions versus the interspecific ones described here.

In the following video a tarantula hawk is exploiting – capture or handling phase – a tarantula (with much drama on the part of the photographer):