Evolution of sexual cannibalism in mantises
The evolution of sexual cannibalism in praying mantises is of much debate (Suttle 1999). The difficulty understanding why this species has evolved to behave in such a way is largely due to sexual cannibalism taking on many different forms in respect to the role and behavior of each sex, the potential benefit to each sex and the timing of when the courtship/copulation takes place (Suttle 1999). There is a large array of hypotheses that suggest why this phenomenon has evolved within praying mantises, with all theories expressing substantial evidence that they may be correct.
The first theory of why mantises have thought to have evolved to cannibalize includes the evolutionary theory that the sexual cannibalism phenomenon provides benefits to both sexes (Thornhill 1976). Therefore it is suggested cannibalism in mantises is an adaptive 'male' strategy evolved as an extreme form of paternal investment for his offspring, where the sacrifice of his own life benefits the mother of his offspring to increase fecundity and health (Thornhill 1976) (Suttle 1999).
The second theory proposed by (Elgar & Nash 1998) represents a model to explain the premating sexual cannibalism as a mechanism used by the female mantis for mate rejection and choice (Prenter et al' 2006). According to this theory females asses potential mates and then cannibalize or mate depending on phenotypic characteristics that vary among males of the species (such as body size) (Prenter et al' 2006) Thus suggesting females should mate with larger males to produce larger offspring, assuming that the larger body size of the male mantis chosen is an indication of superiority and heritable foraging capabilities (Suttle 1999). This also suggests smaller males are only used for courtship to be consumed and used for fitness and fecundity benefits.
Another model (Newman & Elgar 1991) attempting to explain sexual cannibalism, suggests it has evolved through foraging considerations. This model suggests the two most important factors for the evolution of sexual cannibalism are ecological; the expected number of males encountered by a female and the amount of mass gained from consumption of the male drive and determine cannibalism (Suttle 1999). Therefore this model suggests females are more likely to cannibalize males when the male encounter rate is high and the food availability from other sources is low (Barry et al' 2008).
A final possible theory that does not discuss sexual cannibalism in terms of adaptive value for either sex, is the assumption sexual cannibalism evolved for adult mantises due to indirect behaviors that are adaptive in previous life history stages, but none adaptive or even maladaptive in adults (Suttle 1999). Thus identifying sexual cannibalism may carry over into adult mantises due to genetic constraints on life history aggression.
It appears the evolution of sexual cannibalism in praying mantis, and other similar behavioral species is still of much debate. In conclusion the majority of theories lead towards the phenomenon taking place to allow for a benefit largely towards the female sex, with consumption of the male resulting in an increase in her health and nutritional needs, fecundity and the fitness of her offspring. Therefore it is likely sexual cannibalism in the mantis species here has evolved to satisfy dietary requirements needed by the female to produce the fittest offspring possible, as well as maintain her own body condition to allow for copulation to take place at later stages in her life.
The first theory of why mantises have thought to have evolved to cannibalize includes the evolutionary theory that the sexual cannibalism phenomenon provides benefits to both sexes (Thornhill 1976). Therefore it is suggested cannibalism in mantises is an adaptive 'male' strategy evolved as an extreme form of paternal investment for his offspring, where the sacrifice of his own life benefits the mother of his offspring to increase fecundity and health (Thornhill 1976) (Suttle 1999).
The second theory proposed by (Elgar & Nash 1998) represents a model to explain the premating sexual cannibalism as a mechanism used by the female mantis for mate rejection and choice (Prenter et al' 2006). According to this theory females asses potential mates and then cannibalize or mate depending on phenotypic characteristics that vary among males of the species (such as body size) (Prenter et al' 2006) Thus suggesting females should mate with larger males to produce larger offspring, assuming that the larger body size of the male mantis chosen is an indication of superiority and heritable foraging capabilities (Suttle 1999). This also suggests smaller males are only used for courtship to be consumed and used for fitness and fecundity benefits.
Another model (Newman & Elgar 1991) attempting to explain sexual cannibalism, suggests it has evolved through foraging considerations. This model suggests the two most important factors for the evolution of sexual cannibalism are ecological; the expected number of males encountered by a female and the amount of mass gained from consumption of the male drive and determine cannibalism (Suttle 1999). Therefore this model suggests females are more likely to cannibalize males when the male encounter rate is high and the food availability from other sources is low (Barry et al' 2008).
A final possible theory that does not discuss sexual cannibalism in terms of adaptive value for either sex, is the assumption sexual cannibalism evolved for adult mantises due to indirect behaviors that are adaptive in previous life history stages, but none adaptive or even maladaptive in adults (Suttle 1999). Thus identifying sexual cannibalism may carry over into adult mantises due to genetic constraints on life history aggression.
It appears the evolution of sexual cannibalism in praying mantis, and other similar behavioral species is still of much debate. In conclusion the majority of theories lead towards the phenomenon taking place to allow for a benefit largely towards the female sex, with consumption of the male resulting in an increase in her health and nutritional needs, fecundity and the fitness of her offspring. Therefore it is likely sexual cannibalism in the mantis species here has evolved to satisfy dietary requirements needed by the female to produce the fittest offspring possible, as well as maintain her own body condition to allow for copulation to take place at later stages in her life.