title: Lack of divergence in seed ecology of two Amphicarpaea (Fabaceae) species disjunct between eastern Asia and eastern North America.
abstract: OBJECTIVE
  Many congeneric species are disjunct between eastern Asia and eastern North America. No previous study has compared the seed biology of closely related disjunct taxa of legumes or of a diaspore-heteromorphic species. Our objective was to compare seed dormancy in two such sister species in the genus Amphicarpaea (Fabaceae).
  
  
  METHODS
  We investigated the ecology and ecophysiology of aerial and subterranean seeds of the amphicarpic species Amphicarpaea edgeworthii from China and compared the results to those published for its sister species A. bracteata from eastern North America.
  
  
  RESULTS
  The seed coat of aerial seeds of A. edgeworthii is well developed, whereas the seed coat of subterranean seeds is not. Aerial seeds have combinational dormancy (physical dormancy [PY] + physiological dormancy [PD]) broken by scarification followed by cold stratification or by after-ripening and scarification; whereas subterranean seeds have PD broken by cold stratification. Aerial seeds formed a persistent soil seed bank, and subterranean seeds a transient soil seed bank. Aerial seeds of A. bracteata also have PY+PD and subterranean seeds PD. Subterranean seeds of both species are desiccation intolerant.
  
  
  CONCLUSIONS
  Dormancy in neither aerial nor subterranean seeds of both species has diverged over geological time. Compared to subterranean seeds, aerial seeds of both species dispersed over longer distances. Seed dispersal ability and degree of dormancy of neither species fits the high-risk/low-risk (H-H/L-L) strategy found in many diaspore-dimorphic species. Rather, both species have an H-L/L-H strategy for these two life history traits.
authors.affiliation: State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China University of Chinese Academy of Sciences, Beijing 100039, China.
authors.forename: Keliang
authors.initials: K
authors.lastname: Zhang
authors.affiliation: Department of Biology, University of Kentucky, Lexington, Kentucky 40506 USA.
authors.forename: Jerry M
authors.initials: JM
authors.lastname: Baskin
authors.affiliation: Department of Biology, University of Kentucky, Lexington, Kentucky 40506 USA Department of Plant and Soil Sciences, University of Kentucky, Lexington, Kentucky 40546 USA.
authors.forename: Carol C
authors.initials: CC
authors.lastname: Baskin
authors.affiliation: State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
authors.forename: Xuejun
authors.initials: X
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
authors.forename: Zhenying
authors.initials: Z
authors.lastname: Huang
mesh_terms: D044822:Biodiversity; D018533:Biomass; D007887:Fabaceae / Q000033:anatomy & histology* / Q000528:radiation effects; D005202:Asia, Eastern; D018525:Germination / Q000528:radiation effects; D006813:Humidity; D008027:Light; D009656:North America; D009929:Organ Size / Q000528:radiation effects; D058614:Seed Dispersal / Q000528:radiation effects; D012639:Seeds / Q000033:anatomy & histology*; D012987:Soil; D013045:Species Specificity; D013696:Temperature; D014867:Water
chemical_list: D012987:Soil; D014867:Water
keywords: Amphicarpaea bracteata; Amphicarpaea edgeworthii; amphicarpy; diaspore heteromorphism; eastern Asian–eastern North American disjunct distribution pattern; seed dispersal; seed dormancy; soil seed bank