Summary
Seeds of the Panamanian shrub, Hybanthus prunifolius (Schult.) Schulze (Violaceae) are dispersed at different times in different years ((March to June) and are exposed to the irregular rainfall of the dry season in some years. Fluctuations in soil moisture in the dry season represent suboptimal conditions for germination and seedling survival. There are no mechanisms to prevent germination prior to the arrival of consistent rains in the wet season.
Among three natural cohorts of seeds followed in two years, the cohort experiencing the longest time from sowing to consistent rains had the highest germination, but it also had the longest time lag from sowing to, beginning of germination, longest germination period, and lowest survival of seedlings 3 months after sowing.
Seeds were also induced experimentally to germinate under 14 different moisture patterns. The patterns encompassed 1) varying lengths of moisture before a dry period, 2) inconsistent moisture, and 3) varying lengths of dryness prior to any moisture.
Mortality of seeds by fungal infection occurred if the wet period was delayed. But germination was less affected by fluctuations than was seedling survival. Length of the first wet period and frequency of occurrence of the wet period both affected germination levels. Survival and development of seedlings was influenced by the number of days exposed to dry conditions and by the stage of development at the beginning of the dry period. Young seedlings suffered attrition due to drought stress, and older seedlings died from fungal attack.
Results from field and experimental sowing of seeds both indicate that this perennial species has minimal defense against germination when conditions are suboptimal for seedling survival. Undoubtedly there is more recruitment in some years than in others.
Similar content being viewed by others
References
Baskin, J.M., Baskin, C.C.: Germination of winter annuals in July and survival of the seedlings. Bull. Torrey Bot. Club 98, 272–276 (1971)
Baskin, J.M., Baskin, C.C.: Physiological ecology of germination of Viola rafinesqui. Am. J. Bot. 59, 981–988 (1972)
Baskin, J.M., Baskin, C.C.: Some eco-physiological aspects of seed dormancy in Geranium carolinianum L. from Central Tennessee. Oecologia (Berl.) 16, 209–219 (1974)
Caplenor, D.: Temperature control of germination of Helenium amarum seeds. Ecology 48, 661–664 (1967)
Cohen, D.: Optimizing reproduction in a randomly varying environment when a correlation may exist between the conditions at the time a choice has to be made and the subsequent outcome. J. Theoret. Biol. 16, 1–14 (1967)
Cruden, R.W.: The adaptive nature of seed germination in Nemophila menziesii aggr Ecology 55, 1295–1305 (1974)
Duke, J.A.: On tropical seeds, seedlings, systems, and systematics. Ann. Mo. Bot. Gard. 56, 125–161 (1969)
Fretwell, S.D.: Populations in a seasonal environment. Princeton U. Press. Princeton, N.J. 217 p. (1972)
Guevera, S., Gomez-Pompa, A.: Seeds from surface soils in a tropical region of Veracruz, Mexico. J. Arnold Arb. 53, 312–335 (1972)
Levins, R.: Evolution in changing environments; some theoretical explorations. Princeton: Princeton University Press (1968)
Tevis, L.J.: Germination and growth of ephemerals induced by sprinkling a sandy desert. Ecology 39, 681–688 (1958a)
Tevis, L.J.: A population of desert ephemerals germinated by less than one inch of rain. Ecology 39, 688–695 (1958b)
Went, F.W.: Ecology of desert plants. I. Observations on germination in the Joshua Tree National Monument, Calif. Ecology 29, 242–253 (1948)
Went, F.W.: Ecology of desert plants. II. The effect of rain and temperature on germination and growth. Ecology 30, 1–13 (1949)
Williams, W.A., Elliott, J.R.: Ecological significance of seed coat impermeability to moisture in crimson, subterranean and rose clovers in a Mediterranean-type climate. Ecology 41, 733–742 (1960)
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Augspurger, C.K. Irregular rain cues and the germination and seedling survival of a Panamanian shrub (Hybanthus prunifolius). Oecologia 44, 53–59 (1979). https://doi.org/10.1007/BF00346397
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00346397