Males exhibit striking variation in the degree to which they invest in offspring, from merely provisioning females with sperm, to providing exclusive post-zygotic care. Paternity assurance is often invoked to explain this variation: the greater a male's confidence of paternity, the more he should be willing to provide care. Here, we report a striking exception to expectations based on paternity...

Munida subrugosawas sampled monthly from November 1997 to November 1999 in the Beagle Channel by means of an epibenthic trawl. The reproductive cycle started in May, re£ected by the occurrence of ovigerous females. Maximum size of oocytes, maximum value of gonadosomatic index in females (16.8 gmmcarapace length [CL]71) and males (1.6 gmmCL71), and the proportion ( 70%) of ovigerous females with...

Indirect fitness benefits gained through kin-selected helping are widely invoked to explain the evolution of cooperative breeding behavior in birds. However, the impact of helpers on productivity of helped broods can be difficult to determine if the effects are confounded by territory quality or if the benefit of helpers is apparent only in the long term. In riflemen Acanthisitta chloris, helpi...

In birds, different types of predators may target adults or offspring differentially and at different times of the reproductive cycle. Hence they may also differentially influence incubation behaviour and thus embryonic development and offspring phenotype. This is poorly understood, and we therefore performed a study to assess the effects of the presence of either a nest predator or a predator ...

Combining George C. Williams' idea that evolutionary constraints prevent asexual mutants from arising more frequently in low fecundity organisms, like mammals and birds, with an earlier one by David Lack that the brood size of these organisms has an optimum, and producing larger broods reduces their fitness, leads to a novel hypothesis about the maintenance of sex in them. All else equal, the e...

Anopheles cruciansWiedemann(sensu lato)was investigated for thepresenceof cryptic species using rDNA ITS2 sequences. This complex of species presently contains the named species An. crucians, An. bradleyi King, and An. georgianus King. Adult female mosquitoes were collected at 28 sites in Alabama, Florida, Georgia, North Carolina, Mississippi, and Louisiana, resulting in 245 progeny broods. Spe...

The potential capacity of larval growth and immune response traits of the autumnal moth to adapt to heavy metal polluted environment was tested experimentally. Both the relative growth rate (RGR) and pupal weight were significantly higher in control trees than on polluted trees, indicating that metal pollution prevented the insect from achieving maximal growth on birch leaves. Larval growth rat...

In birds, the offspring of females in socially monogamous species can be sired not only by their social partner (within-pair mating) but also by other males (extra-pair mating), resulting in broods of mixed paternity. Several hypotheses have been proposed which attempt to explain the adaptive significance of this behavior, including the genetic diversity hypothesis, the good genes hypothesis, t...

-Survival characteristics of 25 broods of Mallards (Anas platyrhynchos) were determined on a study area in the Missouri Coteau of south-central North Dakota in 1976-1977. Radio-equipped Mallard hens fledged at least one duckling in 7 of 16 (44%) broods produced in 1976, 5 of 9 (55%) in 1977, and 12 of 25 (48%) for both years combined. Of the 13 broods in which all young were lost, 11 (85%) were...