Sex Ratio and Reproductive Effort in the Dioecious Juniperus communis subsp. alpina (Suter) Čelak. (Cupressaceae) Along an Altitudinal Gradient

The hypothesis that reproductive cost differs between sexes was tested in Juniperus communis subsp. alpina along an altitudinal gradient. Sex ratio (male : female) increased significantly with elevation, and above 2600 m it was significantly male-biased. The reproductive effort was markedly greater...

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Bibliographic Details
Published in:Annals of botany 2002-02, Vol.89 (2), p.205-211
Main Authors: ORTIZ, PEDRO LUIS, ARISTA, MONTSERRAT, TALAVERA, SALVADOR
Format: Article
Language:English
Subjects:
Acclimatization - physiology
Altitude
Ecology
Female animals
Fruit - growth & development
Juniperus - growth & development
Juniperus communis alpina
Male animals
Plant growth
Plants
Pollination
Population ecology
Reproduction - physiology
Seed cones
Seeds
Seeds - growth & development
Segregation
Sex ratio
Spain
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Summary:The hypothesis that reproductive cost differs between sexes was tested in Juniperus communis subsp. alpina along an altitudinal gradient. Sex ratio (male : female) increased significantly with elevation, and above 2600 m it was significantly male-biased. The reproductive effort was markedly greater for females than for males at all elevations. However, over 3 years of study, the growth of the females, measured as elongation of the main axes, was similar to that of the males. In both sexes, growth decreased with increasing elevation. Neither size of the ripe seed cones, nor the number of developed seeds per cone varied with elevation. The percentage of filled seeds was significantly greater at higher elevations indicating more favourable conditions for wind pollination in these stands. However, cone production decreased with elevation and so, reproductive success of J. communis subsp. alpina in Sierra Nevada decreases towards both upper and lower altitudinal distribution limits. The results do not support the hypothesis of differential reproductive cost between sexes; thus, alternative arguments to explain the altitudinal variation of sex ratio are discussed.
ISSN:0305-7364
1095-8290
DOI:10.1093/aob/mcf028