Latitudinal variation in reproductive timing of a short-lived monocarpic, Daucus carota: (Apiaceae)

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Elizabeth P. Lacey, Professor (Creator)
Institution
The University of North Carolina at Greensboro (UNCG )
Web Site: http://library.uncg.edu/

Abstract: A reciprocal transplant experiment was conducted to examine several aspects of life-history variation in Daucus carota along its latitudinal range in eastern North America. Seeds collected from natural populations at 36°, 42°, and 45° N were sown onto plots at each of the three latitudes. Marked seedlings were followed for 3 yr to examine (1) genetic and environmental components of variation in growth, survival, and year of re-production; (2) size and age at time of reproduction; and (3) the roles that density- and age-dependent selection may play in producing the variation in age of reproduction. Mean age of reproduction increased clinally from south to north but showed no pattern of variation among different-aged populations within the same latitude. The clinal variation has likely arisen since the introduction of D. carota into North America in the 17th century and has developed independently of any role that growth rate plays in determining age of reproduction. Density influences age of reproduction both directly and indirectly by affecting plant size. Age-specific survival varied strongly over plot latitude but not among populations planted in the same latitude. The ratio of percent germination and survival of 1-yr-olds to percent survival of 2-yr-olds was ˜ 3:1, 0.2:1, and 0.15:1 for plots at 36°, 42°, and 45° N, respectively. The experiment suggests that latitudinal variation in age-specific mortality patterns is helping to maintain clinal variation in age of reproduction. Density-independent factors contribute more strongly to age-specific mortality than do density-dependent factors. Age classes are based on times of peak flowering rather than on times of growing seasons. Such intervals allow for better evolutionary interpretation of demographic data.

Additional Information

Publication
Ecology 69(1): 220-232
Language: English
Date: 1988
Keywords
age-specific selection, Daucus carota, density-dependent selection, genetic variation, growth, latitudinal variation, life-history evolution, monocarp, reproductive timing, survival