Fig. 3

Theoretical outline proposing potential pathways for the evolution and spread of worthless nuptial gifts in spider populations under benign, moderate, and highly stressful environmental conditions. (I) In a scenario of benign conditions, prey are abundant and individuals have relatively low costs of body maintenance, and survival, hence, nutritive nuptial gifts are expected to be the dominant tactic adopted by males. (II) Under moderate stressful conditions, prey becomes occasionally limited, and the cost of individuals’ body maintenance and survival becomes relatively high. Males would reduce costs of gift production by offering worthless gifts as an alternative mating tactic. Males eventually improve deception by adding more silk, which increases female attraction. By receiving worthless gifts, large females would suffer costs and a reduction in fitness success; hence, they are expected to favor paternity of males offering nutritive gifts over those with worthless gift. Worthless gifts would be maintained in low percentage in the population. (III) Under highly stressful conditions, prey becomes constantly limited, and the cost of individuals’ body maintenance and survival becomes extremely high. Selection would favor small sizes in the population, maximizing individual fitness in the environment. Males would reduce costs of gift production by offering worthless gifts as an alternative mating tactic. Because of size reduction, small females would not suffer fitness costs when receiving worthless gifts, and hence, they are expected to favor paternity of males regardless of gift content. Worthless gifts would be favored, spread, and be maintained in high percentages in the population