Abstract
The frequency of occurrence of abnormal, three- (or more) needle dwarf shoots of most southern and central European two-needle pine (<em>Pinus</em>) species were studied. No specimens with more than two-needle dwarf shoots were found in a population of <em>P. nigra </em>Arnold subsp. <em>salzmannii </em>(Dunal) Franco from the Iberian Peninsula and in two populations of <em>P. uliginosa</em> Neumann from the Sudeten Mountains in Central Europe. Single specimens were found within one population of <em>P. pinaster </em>Aiton from the Iberian Peninsula and among six populations of <em>P. sylvestris </em>L. from the Iberian Peninsula and Central Europe. Abnormal dwarf shoots mostly with three, but also four, five or six needles were found among 24 of 25 surveyed populations of <em>P. mugo </em>Turra and <em>P. uncinata </em>Ramond. The average frequency of specimens with at least one three-needle dwarf shoot was 24% for <em>P. mugo</em> and 20% for <em>P. uncinata</em>. The frequencies of occurrence varied significantly among studied populations and were highest in samples collected from the upper elevational range limits of the species in the mountains and near the northern limits of their ranges. The frequency of abnormal dwarf shoots in the same populations was significantly high in 2-3 consecutive years. Needles from three-needle dwarf shoots were not significantly shorter than those of two-needle shoots.
Highlights
IntroductionPinus mugo Turra and P. uncinata Ramond are closely related species, treated recently as subspecies of P. mugo sensu lato (= P. mugo complex, see Christensen 1987a)
Pinus mugo Turra and P. uncinata Ramond are closely related species, treated recently as subspecies of P. mugo sensu lato (= P. mugo complex, see Christensen 1987a).Both taxa and other pines belonging to subsection Sylvestres (Pinus sylvestris L. and P. uliginosa Neumann in Central Europe) normally have two needles per dwarf shoot
The occurrence of specimens of the Pinus mugo complex (P. mugo, P. uncinata and intermediate taxa) with three-needle dwarf shoots has recently been reviewed by Christensen (1987b)
Summary
Pinus mugo Turra and P. uncinata Ramond are closely related species, treated recently as subspecies of P. mugo sensu lato (= P. mugo complex, see Christensen 1987a). Both taxa and other pines belonging to subsection Sylvestres (Pinus sylvestris L. and P. uliginosa Neumann in Central Europe) normally have two needles per dwarf shoot. On the basis of herbarium materials, he concluded that three-needle dwarf shoots may be found throughout the natural range of the species, but mainly at the upper limit of their altitudinal range He found 27 specimens with abnormal number of needles among 249 examined herbarium sheets
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