Seed morphometrics and adaptive geographic differentiation

David L Venable, Eric Dyreson, Daniel Piñero, Judith X. Becerra

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

Adaptive geographic differentiation is documented for seed morphology of 36 populations of Heterosperma pinnatum Car. (Asteraceae), a seed heteromorphic annual plant in the central highlands of Mexico. Achenes (single-seeded fruits) vary continuously within heads but are classified by shape and position as central, intermediate, or peripheral morphs and as having adhesive awns or not. Here we quantify shape as a principal component score contrasting log length and width of achenes. Heads and their variation among populations are described in terms of maximum, minimum, and range of shape scores; the number of achenes per head; quantitative indices of the abruptness of shape shift; where in the head the most abrupt change in shape occurs; and what achene shapes have awns. First and second principal components of these descriptors summarize 86% of among-population variation in achene and head morphology and correlate strongly with percent central achenes per head (%C) and percent of achenes with awns (%A), respectively. Awns are associated with greater dispersibility and achene shape is correlated with speed of dormancy loss. We hypothesized that dispersal morphology would be associated with vegetation attributes indicative of population ephemerality and that dormancy morphology would be associated with precipitation patterns during the early germination season. Morphological distance matrices were calculated using Euclidean distances among populations in %A and %C. Geographic distances among populations were calculated, as were genetic distances based on isozyme frequencies from 29 bands of six enzymes. Vegetation was classified as open or closed and early spring (germination season) and summer precipitation means were determined for each site. Closed vegetation was assumed to provide only ephemeral habitats for H. pinnatum. Partial matrix correlations between morphology and environment controlled for geographic but not genetic distance among sites, since the latter was not significantly correlated with either morphology or geography. A significant relationship was found between %A and closed vegetation, lower spring, and higher summer precipitation. %C was only correlated with lower spring precipitation. Independence of isozyme and morphological traits is interpreted in terms of selection on the latter but not the former.

Original languageEnglish (US)
Pages (from-to)344-354
Number of pages11
JournalEvolution
Volume52
Issue number2
StatePublished - 1998

Fingerprint

Seeds
seed
achene
fruits
seeds
Head
Population
vegetation
Germination
dormancy
Isoenzymes
genetic distance
isozymes
germination
Controlled Environment
Asteraceae
Geography
dispersibility
annual plant
matrix

Keywords

  • Adaptation
  • Dispersal
  • Dormancy
  • Ecotypic differentiation
  • Genetic distance
  • Germination
  • Heterosperma pinnatum
  • Morphometrics
  • Seed heteromorphism

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Agricultural and Biological Sciences (miscellaneous)
  • Ecology, Evolution, Behavior and Systematics
  • Genetics
  • Ecology
  • Genetics(clinical)

Cite this

Venable, D. L., Dyreson, E., Piñero, D., & Becerra, J. X. (1998). Seed morphometrics and adaptive geographic differentiation. Evolution, 52(2), 344-354.

Seed morphometrics and adaptive geographic differentiation. / Venable, David L; Dyreson, Eric; Piñero, Daniel; Becerra, Judith X.

In: Evolution, Vol. 52, No. 2, 1998, p. 344-354.

Research output: Contribution to journalArticle

Venable, DL, Dyreson, E, Piñero, D & Becerra, JX 1998, 'Seed morphometrics and adaptive geographic differentiation', Evolution, vol. 52, no. 2, pp. 344-354.
Venable DL, Dyreson E, Piñero D, Becerra JX. Seed morphometrics and adaptive geographic differentiation. Evolution. 1998;52(2):344-354.
Venable, David L ; Dyreson, Eric ; Piñero, Daniel ; Becerra, Judith X. / Seed morphometrics and adaptive geographic differentiation. In: Evolution. 1998 ; Vol. 52, No. 2. pp. 344-354.
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