A Comparative Study of the Population Dynamics of Five Species of Veronica in Natural Habitats

Abstract

(1) The population dynamics of three annual species of Veronica (V. arvensis, V. hederifolia and V. persica) and two perennial species (V. serpyllifolia and V. chamaedrys) were compared in six sites in which one or more of the species grew naturally. (2) A survey of the populations of buried viable seeds in the sites showed that in some sites where growing plants were absent seeds of three or four of the species were present. The perennials generally contributed less to the buried seed population than the annuals, although some seeds of V. serpyllifolia were present in the soil of all the sites. (3) The species differed in times and rates of germination. The seeds of the two winter annuals V. hederifolia and V. arvensis germinated in the autumn and early spring. The time of germination of V. persica was much less specific and occurred at several periods during the autumn, spring and summer. Seedlings of the perennials V. chamaedrys and V. serpyllifolia were observed in the summer. (4) Many seeds of V. hederifolia, V. serpyllifolia and V. chamaedrys were lost from the populations between the time of seed dispersal and the subsequent winter. This contrasts with the behaviour of V. arvensis and V. persica in which significant mortality did not start until after seedling emergence. Seedlings of V. arvensis, V. serpyllifolia and V. persica were killed during winter but those of V. hederifolia were undamaged. (5) Flowering in V. arvensis and V. hederifolia started early in spring when some plants bore only one or two pairs of leaves, and seeds were produced shortly after flowering. In contrast, in V. persica seeds were produced more than one month after the first flowers opened. All plants of the annuals died after flowering-they produced no persistent vegetative shoots. (6) V. serpyllifolia was able to flower in its first year of growth in open habitats, although many plants remained vegetative until the second year; the population produced more seeds in its first year than were present in the sites at the beginning. Even in plants that flowered, however, a number of shoots remained vegetative. In grassland a much higher proportion of the plants remained vegetative. This species, which has a much more compact growth habit than V. chamaedrys, seems to maintain itself through production of numerous seeds and its perennial habit.