Temporal patterns of reproduction and outcrossing in weedy populations of Echium plantagineum

Single and multilocus estimates of outcrossing rates were made in three populations of Echium plantagineum. Despite spatial separation, variations in population size (though not density) and reproductive output, no statistically significant difference was detected in outcrossing rates between the populations. Similarly, only slight differences in outcrossing rates were detected within populations when estimates were based on seed collected from flowers open at different times in the flowering season. The earliest flowers tended to have a lower estimated rate of outcrossing. In all cases, multilocus outcrossing rates were high, ranging from 0.81 to 1.05.
In all three populations flower production extended over a period of more than 2 months but the majority of seed was produced by flowers that opened during the first third of the (lowering season. This was largely caused by a high rate of flower production during the early part of the season and not changes in the number of seeds set per flower. The average number of seeds produced per flower varied both between individuals within populations, and between the different populations, but neither of these differences were significant.
Controlled pollination of flowers with self or outcross pollen, applied either singly or together, failed to detect any differences in the likelihood that either type of pollen would give rise to fertile seeds.