Germ banking: Bet-hedging and variable release from egg and seed dormancy

Margaret E.K. Evans, John J. Dennehy

Research output: Contribution to journalReview articlepeer-review

140 Scopus citations


Many species produce eggs or seeds that refrain from hatching despite developmental preparedness and favorable environmental conditions. Instead, these propagules hatch in intervals over long periods. Such variable hatch or germination tactics may represent bet-hedging against future catastrophes. Empiricists have independently recognized these approaches in diverse species. Terms such as seed banking, delayed egg hatching, and embryonic diapause have been used to describe these tactics, but connections between fields of study have been rare. Here we suggest a general term, germ banking, to incorporate all previous terms, unifying many seemingly disparate biological strategies under a single definition. We define the phenomenon of germ banking and use several biological examples to illustrate it. We then discuss the different causes of variation in emergence timing, delineate which constitute germ banking, and distinguish between germ banking and optimal timing of diapause. The wide-ranging consequences of germ banking are discussed, including modification of the age structure of a population, the alteration of microevolutionary dynamics, the migration of alleles from the past, the maintenance of genetic and species diversity, and the promotion of species coexistence. We end by posing questions to direct future research.

Original languageEnglish (US)
Pages (from-to)431-451
Number of pages21
JournalQuarterly Review of Biology
Issue number4
StatePublished - Dec 2005
Externally publishedYes


  • Adaptive coin-flipping
  • Bet-hedging
  • Delayed hatching
  • Diapause
  • Dormancy
  • Emergence
  • Environmental variability
  • Geometric mean
  • Germination
  • Maternal effects
  • Seed bank
  • Storage hypothesis
  • Temporal dispersal

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)


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