Sexual dimorphism in immunity: a test using insects (Coleoptera, Diptera, Lepidoptera, Odonata)

Evolutionary theory indicates that 3 3 should allocate more resources to increase mating efficiency trading off longevity while 9 9 would actually do the reverse to gain in egg production and laying. One recent hypothesis dictates that these differences would lead 9 9 to invest more in immunity (to increase longevity) than 3 3 (which will invest more in courtship traits). This difference should be more accentuated in spp. whose 9 9 mate multiply, in which 3 3 will invest less to immunity than in spp. where 9 9 mate once. Here, this was tested by using 8 insect spp. with varying sexual selection pressure, that belong to 4 orders. For each order, one sp. was used in which 9 9 accept one (or close to) mating during their life and another in which 9 9 mate multiply. Encapsulation ability, phenoloxidase activity and hydrolytic enzymes were examined. Animals were virgin, sexually mature and well-fed. Comparative analyses provided restricted support as for 9 9 having higher immune values and that this pattern should be more evident in relation to sexual selection intensity when both pairs of spp. per order and all spp. were analyzed. This study calls for a reformulation of current assumptions of immune costs in relation to gender life history differences.