Behavioral Isolation

Behavioral Isolation

Destini Bates

Normally, we as human do not expect species such as fish and birds to mate but sometimes even very closely related species do not mate either. This is due to reproductive barriers, which are biological features of organisms that prevent species from reproducing and having offspring. There is two types of Reproductive Barriers that exist. The types are Prezygotic barriers and Postzygotic barriers.  Prezygotic barriers prevent mating from even occurring and Postzygotic barriers reduce the likelihood that an offspring will survive after mating has occurred. One Prezygotic Reproductive barrier is Behavioral Isolation. This is a reproductive barrier based on behavior usually in the form of mating rituals and signals.

Signals that attract mates to each other is one of the most important factors determining whether closely related species mate with each other or not. There is many examples of behavioral isolation in nature.  For example, Fireflies, the cue is presented in the form of a distant pattern of light pulses. Male fireflies of a variety of species signal to their female counterparts by flashing their lights in a specific pattern. Females will only respond to the signals flashed by their own species, preventing them from mating with other closely related firefly species. Many species have elaborate courtship rituals to help indicate to each other that they are the correct ones to mate with. An example of this is the Blue-footed Booby. Male Boobies perform a very elaborate dance that shows off his bright blue feet. This helps identify him to female boobies as a potential mate.

        Visual signals are not the only things that create behavioral barriers. Frog calls are very unique to each species in both pitch and pattern. These specific vocalizations create reproductive barriers for frogs that are not of the same species. For a more detailed example of frogs I read in an article, where two scientist studied the frogs of two differ species.. The reproductive behavior of two broadly sympatric, interfertile tree frogs, Hyla cinerea and Hyla gratiosa, was studied. Field observations corroborated the conclusions of a previous study regarding the incompleteness of ecological and temporal isolation and the significance of the species difference in calling position. Both species have more than one kind of call but discrimination experiments showed that in each species, one call is most important as a mate attractant. In single-stimulus experiments some females of both species responded to the calls of the other species. However, in discrimination experiments females of both species responded almost exclusively to conspecific mating calls when those of the other species were equally accessible. Females of Hyla cinerea also chose the pulsed, presumably territorial calls of conspecific males over the mating calls of Hyla gratiosa. Our analyses of the spectra of the calls of the two species differ significantly from those previously published in that two distinct spectral peaks are found. The two peaks have species-specific locations and are important for call recognition by female frogs.