Latitudinal Variation in Reproductive Timing of a Short‐Lived Monocarp, Daucus Carota (Apiaceae)

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 reproduction; (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.

Adaptation and colonization history affect the evolution of clines in two introduced species

“…The establishment of clines is a feature of many species invasions and has been interpreted as a hallmark example of adaptive evolution in action (Johnston & Selander, 1964;Lacey, 1988;Weber & Schmid, 1998;Huey et al, 2000;Kollmann & Banuelos, 2004;Maron et al, 2004Maron et al, , 2007Leger & Rice, 2007;Etterson et al, 2008;Montague et al, 2008). In our study, divergence was often observed in excess of the neutral expectation generated by ancestry, offering particularly strong evidence that the clines are adaptive.…”

Hybrids between cultivated and wild carrots in natural populations in Denmark

“…For example, seed used in Denmark is produced in regions with a warmer climate, such as Southern Europe, California, Chile and Australia. From their wild southern fathers, the hybrids inherit a potential for flowering in their first year (annuality) (Lacey, 1988;Hauser and Bj rn, 2001), and they therefore often flower (bolt) in root-crop fields if not weeded away. From these plants, pollen and seeds may disperse into neighbouring wild populations.…”

COST OF REPRODUCTION IN POLEMONIUM VISCOSUM: PHENOTYPIC AND GENETIC APPROACHES

“…For perennials, ecotypic variation in reproductive schedules, growth, and longevity has been documented in Plantago lanceolata (van Groenendael 1985) and Daucus carota (Lacey 1988). Yet, even though variation within populations is most relevant to selection, studies of genetic differences in the timing and consequences of reproduction in perennial plants are lacking at the population scale.…”