Sexual Selection In Crickets

Sexual selection is one of the defining characteristics of any given species. Female organisms select their mates based on a multitude of different factors based on their species, including size, color, displays of power, and mating or calling sounds. The process of mate selection is very important for organisms because through it they are trying to ensure the best levels of fitness for their future offspring. Mate selection can be divided into two arenas: preference functions, the varying significance of different male characteristics, and choosiness, the lengths a female will go to in time and energy to find and select a mate (Judge, Ting, & Gwynne, 2014). In most species, the males perform displays of power or aggression, making calling sounds, or have attractive colors or other physical characteristics in order to attract female mates. One of the key factors in sexual selection for crickets is the calling song which is
created when a male cricket scrapes his forewings against each other. These songs are used for long distance attraction and for recognition of mates from the same species.
Phonotaxis, moving in response to a sound, toward the male making the calling sound is the first step in mate selection for female crickets, which further shows their importance in the process of sexual selection for female crickets. (Hirtenlehner & Römer, 2014). These calling songs are specific to male crickets of different species and differ in frequency, pulse and chirp pattern. Different preference profiles exist for each species of cricket based on these three characteristics and others like rate duration, pausing and cycling and this allows the female crickets to differentiate between their own species and others (Hennig, Blankers, & Gray, 2016). Speciation is process in which organisms become reproductively isolated and thus form different species. Differences in sexual selection are one of the factors that contribute to this isolation and thus differences in male phenotype related to sexual selection are expected between different
species.
The three species compared in this experiment were Acheta domesticus, Gryllus asimilis, and Gryllus fultoni. As visible in the attached phylogenetic tree (Huang, Ortı́, Sutherlin, Duhachek, & Zera, 2000), all three species share a common ancestor but are separated by different phylogenetic distances. Acheta domesticus is separated from Gryllus asimilis by four node but separated from Gryllus fultoni by five nodes. This means that Acheta domesticus is more evolutionarily similar to Gryllus asimilis than it is to Gryllus fultoni. Thus it would be suspected that the calling song of Acheta domesticus would be more similar to the song of Gryllus asimilis than it is to the song of Gryllus fultoni. It would follow that female Acheta domesticus crickets would be more attracted to the Gryllus asimilis calling song than they are to the Gryllus fultoni calling song. The purpose of this investigation is so test the null hypothesis that differing calling songs will have no effect on female Acheta domesticus behavior and thus female crickets will spend 19.1% a five-minute trial period, 57.3 seconds, inside a zone that comprises 19.1% of the area of the arena regardless of what calling sound is played. The alternate hypothesis is that differing calling songs will effect female Acheta domesticus behavior and thus female crickets not spend 19.1% a five-minute trial period, 57.3 seconds, inside the zone that comprises 19.1% of the area of the arena when different calling sounds are played but will instead spend more time in the designated area when songs of species with less phylogenetic distance are being played.