Journal Article

Sun/shade conditions affect recruitment and local adaptation of a columnar cactus in dry forests

Antonio Miranda-Jácome, Carlos Montaña and Juan Fornoni

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 111, issue 2, pages 293-303
Published in print February 2013 | ISSN: 0305-7364
Published online December 2012 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcs255
Sun/shade conditions affect recruitment and local adaptation of a columnar cactus in dry forests

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Background and Aims

Facilitation among plants in water-limited environments (i.e. where evapotranspiration overcomes the availability of water during the growing season) has been considered a local adaptation to water and light conditions. Among cacti, early life-history stages can benefit from the facilitative effects of nurse plants that reduce solar radiation and water stress. However, whether light condition itself acts as an agent of selection through facilitation remains untested. The aim of this study was to determine (1) whether light conditions affect seedling recruitment, (2) whether the positive effect of shade on seedling recruitment is more intense under more stressful conditions and (3) whether shade condition (facilitation) reduces the magnitude of local adaptation on seedling recruitment relative to full sunlight conditions.

Methods

A reciprocal transplant experiment, coupled with the artificial manipulation of sun/shade conditions, was performed to test for the effects of local adaptation on germination, seedling survival and growth, using two demes of the columnar cactus Pilosocereus leucocephalus, representing different intensities of stressful conditions.

Key Results

Full sunlight conditions reduced recruitment success and supported the expectation of lower recruitment in more stressful environments. Significant local adaptation was mainly detected under full sunlight conditions, indicating that this environmental factor acts as an agent of selection at both sites.

Conclusions

The results supported the expectation that the magnitude of local adaptation, driven by the effects of facilitative nurse plants, is less intense under reduced stressful conditions. This study is the first to demonstrate that sun/shade conditions act as a selective agent accounting for local adaptation in water-limited environments, and that facilitation provided by nurse plants in these environments can attenuate the patterns of local adaptation among plants benefiting from the nurse effect.

Keywords: Dry forest; facilitation; germination; local adaptation; Mexico; nurse-plant syndrome; Pilosocereus leucocephalus; reciprocal transplant experiment; seedling growth; seedling survival

Journal Article.  6842 words.  Illustrated.

Subjects: Plant Ecology

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