Fecundity of Parthenogenetic and Sexual Forms of the Flightless Weevil Scepticus insularis (Coleoptera: Curculionidae) with and without Effects from Mating

We measured the fecundity (number of eggs laid and number of eggs hatched) of the parthenogenetic and sexual forms of the weevil Scepticus insularis (Roelofs) with and without effects from mating, using one sexual and two parthenogenetic populations (one of the latter sympatric and the other allopatric with sexuals). When mated sexuals and unmated parthenogens were compared, the average number of eggs laid per female was largest for allopatric parthenogens (274 eggs), followed by sympatric parthenogens (223), and smallest for sexuals (169), with a significant difference only between allopatric parthenogens and sexuals (P < 0.05). The average number of eggs hatched per female was largest for allopatric parthenogens (136 hatchlings), followed by sexuals (119), and smallest for sympatric parthenogens (59), with a significant difference only between allopatric and sympatric parthenogens. In addition, mating significantly increased the reproductive output of sympatric parthenogens (59 vs. 188 hatchlings per female) by increasing egg productivity and hatching rate, but not that of allopatric parthenogens (136 vs. 133). The productivity of parthenogens of S. insularis is thus nearly equal to (in unmated sympatric parthenogens) or much higher (in other categories of parthenogens) than that of conspecific sexuals at the start of the larval stage, provided that the sex ratio of sexuals is 0.5 and all else being equal. Our results further showed that fecundity and other important aspects of the demography of parthenogenetic females may vary locally, or depending on whether they are sympatric or allopatric with sexuals.