Reproductive interference
Reproductive interference has been found within a variety of taxa, including insects, mammals, birds, amphibians, marine organisms, and plants.
All types have fitness costs on the participating individuals, generally from a reduction in reproductive success, a waste of gametes, and the expenditure of energy and nutrients.
These costs are variable and dependent on numerous factors, such as the cause of reproductive interference, the sex of the parent, and the species involved.
[1] Jamming can occur by signals emitted from environmental sources (e.g. noise pollution), or from other species.
[7] Auditory signalling in the gray treefrog (Hyla versicolor) and the Cope's gray treefrogs (Hyla chrysoscelis) – The success of reproduction is dependent on a female’s ability to correctly identify and respond to the advertisement call of a potential mate.
However, female Cope’s gray treefrogs prefer conspecific male signals that have less overlap (i.e. less interference).
Instead, they are pursued potentially due to being mistaken for a rival conspecific as they share similar characteristics in size, colour, and flight height.
The heterospecific pursuit is costly for the male as they waste energy and time, have a higher risk of injury, and may lose opportunities to defend their territory against subsequent intruders.
[1] The misdirection is caused by a mistake during species recognition, or by an attraction towards heterospecifics that possess desirable traits.
[12] Costs associated with misdirecting courtship for males include the wasted energy investment in the attempt to court heterospecifics, and a decrease in mating frequency within species.
Costs associated with heterospecific mating attempts include wasted energy, time, and potentially gametes if sperm transfer occurs.
The reproductive success of the Cepero’s grasshopper decreases when housed within the same enclosure as high numbers of the slender groundhopper.
The reduction of reproductive success stems from an increase in mating attempts by the Cepero's grasshopper towards the slender groundhopper, which may be due to their larger body size.
Erroneous female choice has costs, including energy wastage, and increases in predation risk when searching for a conspecific.
Additionally, it is highly costly when the mistake leads to heterospecific mating, which involves the wastage of gametes.
The lack of ability to differentiate between the calling songs is proposed to be due to the weak selective pressure on the females.
After the male transfers his sperm into the heterospecific female, different processes can occur that may change the outcome of the copulation.
In addition to the wastage of energy, time, and gametes, the inability to produce female offspring after heterospecific mating skews the sex ratio of the co-existing populations.
Females of both species that mate heterospecifically have a large reduction in fecundity compared to conspecific pairings.
Both individuals suffer a large fitness cost from the wastage of energy, time, and gametes, as they unsuccessfully pass on their genes.
However, females may be able to offset this cost through multiple mating, as they receive nutritional benefits from consuming a nuptial food gift from the male, otherwise known as the spermatophylax.
[29] The frequency of hybridisation increases if it is hard to recognise potential mates, especially when heterospecifics share similarities, such as body size,[30] colouration,[31] and acoustic signals.
[32] Costs associated with hybridisation are dependent on the level of parental investment and on the product of the pairing (hybrid).
[33] Compared to each individual parent species, they hold a different combination of characteristics that can be more adaptable and 'fit' within particular environments.
[34] If an inviable product is produced, both parents suffer from the cost of unsuccessfully passing on their genes.
[35] Barred tiger salamanders were then introduced by humans to California, and the mating between these two species led to the formation of a population of hybrids.
[36] Hybrids pose both ecological and conservation consequences as they threaten the population viability of the native California tiger salamanders, which is currently listed as an endangered species.
[37] The hybrids may also affect the viability of other native organisms within the invaded regions, as they consume large quantities of aquatic invertebrate and tadpole.
