title: Postglacial migration and adaptation for dispersal in pitch pine (Pinaceae).
abstract: OBJECTIVE
  Variation in a species is a blend of adaptive, random, and migratory responses. Pitch pine (Pinus rigida), a highly variable eastern conifer, has occupied multiple glacial refugia, whose harsh conditions favored adaptations enhancing subsequent dispersal and recolonization of newly deglaciated sites. We assessed phenotypic diversity in long-term growth trials to elucidate both the adaptations and likely refugia.
  
  
  METHODS
  Pitch pine progeny from 31 areas were grown in common gardens in six locations, from eastern Massachusetts to Korea.
  
  
  RESULTS
  Survival increased with source latitude, but seedlings from southern latitudes were tallest in the first (postplanting) year, but that advantage dissipated in later years. Progeny from northern latitudes were precocious, highly fecund, had smaller seeds, and more seeds per cone. Seed mass decreased with latitude in both parents and progeny. Serotinous cones were notably common in the New Jersey Pine Plains and Acadia National Park. Various disease agents and frost burn exhibited latitudinal trends that were nonlinear, with a break in the regression slope at about 40°N latitude. Cluster analysis identified both northern and southern groups, largely split between unglaciated and deglaciated terrain, but with Acadia and the Pine Plains as unique outliers. Within the southern group, provenances were organized into contiguous subgroups, but geographic structure was less evident in the northern group.
  
  
  CONCLUSIONS
  The present range of pitch pine was colonized by migrants from at least three different refugia, including at least one on the exposed continental shelf during the Last Glacial Maximum.
authors.affiliation: Department of Plant Sciences, University of California, Davis, California 95616 USA.
authors.forename: F Thomas
authors.initials: FT
authors.lastname: Ledig
authors.affiliation: Department of Ecology, Evolution and Natural Resources, Rutgers University, 14 College Farm Road, New Brunswick, New Jersey 08901 USA smouse@aesop.rutgers.edu.
authors.forename: Peter E
authors.initials: PE
authors.lastname: Smouse
authors.affiliation: Northern Research Station, USDA Forest Service, 11 Campus Boulevard, Newtown Square, Pennsylvania 19073 USA.
authors.forename: John L
authors.initials: JL
authors.lastname: Hom
mesh_terms: D000064:Acclimatization; D028223:Pinus / Q000254:growth & development / Q000502:physiology*; D063148:Plant Dispersal; D011792:Quebec; D012098:Reproduction; D014481:United States
keywords: Pinaceae; Pinus rigida; clutch size; fecundity; glacial refugia; precocity; seed mass; serotiny