Germination ecology of the clonal herb Knautia arvensis: Regeneration strategy and geographic variation

Abstract

Abstract. We investigated germination responses and seed recruitment in the clonal grassland herb Knautia arvensis (Dipsacaceae) throughout its distributional range in Norway. Four predicted relationships between germination responses and field regeneration behaviour were tested using phytotron experiments and experimental and observational field studies. Seedlings appeared in all experimental microsites in the field, corroborating phytotron predictions that gap‐ or depth‐sensing strategies should be absent in the species. Seasonal timing patterns were predicted from a cold stratification response in the phytotron, but these were not supported in the field. The relationship between dormancy, germinability during storage, and seed carry‐over in the field largely conformed to expectations. Seeds from four different geographical regions responded differently to temperature and cold stratification and storage. Dormancy and seed carry‐over was higher in seeds from a coastal population, where winters are relatively mild and the probability of repeated freeze‐thaw events is high, than in populations from mountain and inland areas, where winters are colder. This is discussed against two alternative hypotheses about the relationship between climate and dormancy in seasonal climates.

Seed germination of Pilosocereus arrabidae (Cactaceae) from a semiarid region of south‐east Brazil

“…Seedling survival may be greatly increased if germination avoids times and places when/where mortality risks are comparatively high. This 'avoidance strategy' depends on the ability of seeds to appropriately sense and react to environmental signals that decrease the probability of encountering inadequate growth conditions following germination (Angevine & Chabot 1979;Kitajima & Fenner 2000;Vandvik & Vange 2003).…”

A comparison of life-history characters of arctic and alpine populations of the annual Koenigia islandica

“…Divergence in response to differences in environmental characteristics is substantiated for many traits. Plant populations in dissimilar environments have been shown to differ in seed germination traits-such as temperature requirements (Meyer et al, 1989;Meyer and Monsen, 1991;Schutz and Milberg, 1997), light requirements (Meyer et al, 1990;Milberg and Andersson, 1998), response to wet-cold stratification (Dome, 1981;Meyer and Monsen, 1991;Cavieres and Arroyo, 2000;Vandvik and Vange, 2003) and dormancy (Meyer et al, 1989;Cavieres and Arroyo, 2000;Vandvik and Vange, 2003)-as well as growth, morphology and reproductive traits (Hickman, 1975;Antonovics and Primack, 1982;Potvin, 1986;VanTienderen andVan derToorn, 1991a, 1991b;Gurevitch, 1992a;Winn and Gross, 1993;Li et al, 1998;Joshi et al, 2001;Santamaria et al, 2003;Macel et al, 2007), phenology (Potvin, 1986;Van der Toorn, 1991a, 1991b;Winn and Gross, 1993;Li et al, 1998), reproductive allocation (Hickman, 1975(Hickman, , 1977Antonovics, 1981, 1982;Potvin, 1986) and physiology (Gurevitch, 1992b). These differences can be found not only among plant populations (see citations above) but also among individuals of the same populations growing in different microenvironments (Linhart, 1974;Waser and Price, 1985;Galen et al, 1991;…”

“…Studies on intraspecific variability as a response to dissimilar environmental characteristics in arctic-alpine annuals are lacking. Most studies on among-population divergence in perennials (Potvin, 1986;Meyer et al, 1989;Meyer et al, 1990;Winn and Gross, 1993;Schiitz and Milberg, 1997;Santamaria et al, 2003;Vandvik and Vange, 2003;Macel et al, 2007; see also citations in Section 1.6), and annuals (Nagy and Rice, 1997), are from temperate regions. Studies on arctic and alpine plants have found that plants inhabiting both environments adapt mostly by evolving ecological races rather than generalist strategies.…”

“…Despite similarities between arctic and alpine environments, the gradients of latitude and elevation along this extensive range create important differences in environmental characteristics of tundra (see Section 1.4), differences to which arctic-alpine plant species, including arctic-alpine annuals, germinating in these different environments should have adapted (Bliss, 1956). Differences in germination characteristics of populations of the same species inhabiting dissimilar environments are a widespread feature (Milberg and Andersson, 1998), and adaptations of seed germination to latitudinal and altitudinal climatic differences are well documented in polycarpic perennials Meyer et al, 1989;Meyer and Monsen, 1991;Schutz and Milberg, 1997;Vandvik and Vange, 2003;Gimenez-Benavides et al, 2005).…”