ABSTRACT
Evolutionary theory suggests that mating systems should have substantial effects on gene dynamics of local populations. In polygynous species, local 'breeding groups' may produce significant genetic structure, due to genetic differences among groups, and rate of loss of genetic variation from such populations may be considerably slowed. We examined possible influences of the variable mating system and family group structure on genetic properties of a population of plateau pikas (Ochotona curzoniae). Pika gene dynamics were examined via F-statistics and effective population sizes (N(e)), calculated from genetic correlations within and among individuals and families. Genetic correlations were estimated from mating patterns, population demography, and dispersal patterns. Substantial genetic structure within the population was indicated by a strongly positive F(LS). Genetic influence of natal dispersal out of pika families was indicated by a strongly negative inbreeding statistic (F(IL)=-0.34). Effective size of the population was not greatly different from the census population, whereas a traditional estimate of effective size of the population was much lower, indicating that the family structure of the pikas results in a slowed loss of genetic variation over time. Thus, even though mating patterns of plateau pikas were variable, family structure had a strong influence on pika gene dynamics.
ABSTRACT
We studied mate choice in the wandering albatross, Diomedea exulans, using data from 32 years of banding returns in the population of the Crozet Islands. We studied mating choices in a single year, when the Crozet Islands population was male biased (8:5, males:females). Thus, we expected that females might show great flexibility of choice of partners. Because age and experience might influence mate choice, we tested the expectation that females would choose the oldest and most experienced males for pair bonding. Pair bonds usually last until one member of the pair dies (0.3% of the birds 'divorce'), so mate choice should be especially important. We found that the ages of males and females in both displaying and bonded (breeding) pairs were significantly correlated. These age-associated pairings were not a passive phenomenon, but appeared to be due to an active process of selection of mates of similar age. First-time breeders sought mates of similar age, but preferred those with the most experience. Remating, experienced birds whose mates had died did not pair with individuals of significantly similar age, but predominantly paired with other widowed birds that, on average, were also relatively old. Mate fidelity in wandering albatrosses may be due to the cost of finding and bonding with a new mate. Pair bonds, and thus breeding, took an average of 3.2 and 2.3 years to establish, for males and females, respectively. Thus, remating exerts a potential average reproductive cost of about 15% of lifetime reproductive success. Copyright 1999 The Association for the Study of Animal Behaviour.
