Trait stasis versus adaptation in disjunct relict species: Evolutionary changes in seed dormancy-breaking and germination requirements in a subclade of Aristolochia subgenus Siphisia (Piperales)

Christopher A. Adams, Jerry M. Baskin, Carol C. Baskin

Research output: Contribution to journalArticlepeer-review

36 Scopus citations

Abstract

There are two ideas regarding changes in the physiological and ecological tolerances and requirements within plant lineages through geological time. One is that these attributes have changed very little, or not at all (trait stasis), and the other is that they have undergone considerable change (adaptation), as plants shifted to new climatic and vegetation zones. We tested these ideas for seed dormancy-breaking and germination requirements of four species in a subclade of Aristolochia subgenus Siphisia: the three temperate species, A. macrophylla and A. tomentosa (the basal species in the subclade) of eastern USA and A. manshuriensis of East Asia, and the Mediterranean-climate species A. californica endemic to California, USA. A long period at cold-stratifying temperatures was required for growth of the underdeveloped embryo and seed germination in A. californica, whereas embryos grew and seeds germinated in the other three species at warm temperatures, either before or after they were cold stratified. Thus, seeds of A. californica have either intermediate or deep complex morphophysiological dormancy (MPD), whereas those of the three temperate species have either morphological dormancy or non-deep simple MPD. Further, there were quantitative differences in temperature requirements for dormancy-break and germination between the Appalachian A. macrophylla, which did not differ from its sister species A. manshuriensis, and the lowland A. tomentosa. Thus, within this lineage there has been both trait stasis and divergence (adaptation) in the physiology and ecology of seed dormancy and germination.

Original languageEnglish
Pages (from-to)161-173
Number of pages13
JournalSeed Science Research
Volume15
Issue number2
DOIs
StatePublished - Jun 2005

Bibliographical note

Funding Information:
We thank Wayne Chester (Department of Biology, Austin Peay State University), Rob Schlising (Department of Biology, Chico State University), Victor Bulgakov and Olga Koren (Vladivostok, Russia) for collecting seeds of Aristolochia, and Kingsley Dixon, Tetsuya Kondo and Jeffrey Walck for their helpful comments on the manuscript. Funding for this project was provided by the University of Kentucky Departments of Plant and Soil Science and of Biology, the Southern Appalachian Botanical Society and the Kentucky Natural History Society.

Keywords

  • Aristolochia
  • Embryo growth
  • Evolutionary changes in a lineage
  • Morphological seed dormancy
  • Morphophysiological seed dormancy
  • Trait stasis
  • Underdeveloped embryo

ASJC Scopus subject areas

  • Plant Science

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