When it comes to organisms that reproduce sexually, the consequences of inbreeding are generally undesirable. In order to produce genetically fit offspring, sexual reproduction must occur between two genetically dissimilar individuals. When two genetically related individuals reproduce, the resulting offspring are likely to develop genetic diseases that make them unfit for reproducing themselves. Therefore, in order for any species to survive and avoid extinction, mating must occur between individuals who are not genetically related. Social insects serve as an exception to this rule. In the case of social insects, it is not the fitness of the individual insect that is of primary importance; instead it is the fitness of the colony that matters. This is why termite colonies are referred to as “superorganisms,” and each individual colony member is merely a component of this superorganism. However, inbreeding is not the norm for termites, as termite colonies are comprised of asexual siblings that result from mating between a queen and king termite, or primary reproductives. These siblings are not physically equipped for sexual reproduction, but if a queen becomes absent, some of these siblings develop sexual organs in order to continue reproducing for the colony. These new reproductives are referred to as secondary reproductives, and they produce only inbred offspring. In order for termite colonies to maintain fitness, the rate of inbreeding between secondary reproductives is held in check. Surprisingly, recent studies have shown that even moderate inbreeding between secondary reproductives can have a lasting negative impact on the overall health of a colony.
Researchers found that the Zootermopsis angusticollis termite species became more vulnerable to disease after one single generation of inbreeding. The first generation of inbred termites demonstrated impaired social abilities that are essential for termite survival. For example, termites indulge in group-wide grooming in order to cleanse themselves of disease-causing pathogens, but this social behavior had clearly been compromised in the inbred group of termites as a consequence of inbreeding. This lack of grooming made the inbred termites susceptible to colony-wide diseases. A study on Formosan subterranean termites in Louisiana and Hawaii showed that inbreeding can lead to smaller-sized workers that cannot perform their foraging duties as effectively as workers that are not inbred. In most cases, inbreeding must occur over several generations before termite colonies become disadvantaged as a result, but different termite species have varying degrees of tolerance to inbreeding.
Do you believe that inbreeding can be beneficial to termite colonies in some circumstances?