Here we study the effect of ageing on several parameters related to individual fitness such as mortality, mating ability, reproductive rates, attractiveness and mate choice in the marine copepod Oithona davisae.
It would be helpful if we could identify the exact mechanism increasing female mortality after mating in this species.
The 25°C treatment of the sons is directly comparable to that of the fathers, and indeed residual longevity of their mates was similar in absolute terms in both data sets (Fig. 2a), as would be expected if female mortality after mating is due at least in part to wounds inflicted by males [ 42].
While some studies [ 24, 28] have shown evolution in males' ability to cause mortality in their mates without affecting their fecundity, others have not seen any measurable change in mate harming ability of males [ 31].
The calves have about a 20% mortality rate, so mating with bigger females could increase a male's chance of reproductive success by siring larger, hardier offspring, Pack says.
High female encounter rates in nature (>10 day−1), a rapid age-dependent decline in female fertility, and a high mortality cost of mating in males are conducive to the development of male choosiness.
Demographic Allee effects, defined as positive impacts of density on the total fitness of individuals (e.g., high rate of mortality and low mating success in sparse populations), have been hypothesized to strongly influence population dynamics and to help constrain geographic range boundaries [8], [11], [12].
It remains to be investigated whether this female adaptive behaviour (i.e., attacking males only after ensuring sperm) has evolved from selection imposed by males that preferentially approach non-aggressive females or because high male mortality during the mating season [28], [43], [47] entails a high risk of remaining unmated for females in natural populations.
In larger colonies, fighter tactics were associated with higher mortality and lower mating success.
On the other hand, M-males, which cause increased mortality in their mates, show significantly higher sperm defense ability.
