Supplementary methods, sample size information, and results from Obligately silent males sire more offspring than singers in a rapidly evolving cricket population

How sexual traits are gained and lost in the wild remains an important question in evolutionary biology. Pacific field crickets (Teleogryllus oceanicus) in Hawaii provide an unprecedented opportunity to investigate the factors facilitating evolutionary loss of a sexual signal in real time. Natural selection from an acoustically orienting parasitoid fly drove rapid evolution of a novel, silent male morph. While silent (flatwing) males enjoy protection from the fly, they face difficulty attracting mates. We tested how offspring production varies in association with three male attributes affected by the spread of flatwing: wing morph (flatwing or normal-wing), age (flatwings should survive longer than singers) and exposure to calling song during rearing (wild populations with many flatwings lack ambient calling song). Per mating event, flatwings sired more offspring than singers and older males were mounted more quickly by females when presented with standard courtship song. Despite prior work showing that male age and acoustic experience influence sperm characteristics associated with fertilization, age and song exposure had no influence on male offspring production per mating. This represents the first evidence that the silent male morph possesses a reproductive advantage that may help compensate for precopulatory barriers to mate attraction.