Ecophysiology and genetic diversity in species of the bamboo Chusquea in the high Andes, Venezuela

Background: Woody bamboos of the genus Chusquea grow along a broad range of elevations in the Venezuelan Andes. Their growth-form and density vary along the cloud forest ? p?ramo gradient. In this article, we related ecophysiological traits and population genetic diversity information to explain the distribution of growth-form patterns of Chusquea in the Merida Andes, Venezuela. Aims: We quantified differences in the ecophysiological response and genetic diversity of scandent cloud forest and shrub-like p?ramo bamboos of the genus Chusquea, taking in account the differences in their flowering patterns, growth-form and habitat. Methods: We related low temperature resistance, water relations and leaf gas exchange variables to the growth-form, habitat, flowering patterns and genetic diversity in species of Chusquea. The genetic diversity study was based on Inter Sequence Simple Repeats and Random Amplified Polymorphic DNA markers analysis of cloud forest and p?ramo populations. Results: Scandent cloud forest and shrub-like p?ramo species of Chusquea had a very similar ecophysiological response for all the variables analysed during wet and dry seasons and were capable of enduring freezing temperatures through moderate supercooling. Species associated with the cloud forest ? p?ramo gradient maintained low stomatal conductance and transpiration rates that favoured high leaf water potentials, without limiting photosynthetic rates. Shrub-like bamboos growing above the continuous forest line had a small decline in net photosynthesis rates, associated with an increase in water use efficiency. Both scandent and shrub-like bamboos had a remarkably high genetic diversity, comparable to non-clonal species. Conclusions: Species of Chusquea in the Venezuelan Andes are a physiologically relatively homogeneous group across a broad elevation gradient. Population genetic diversity appears to be more related with their flowering pattern and habitat conditions than with their growth form.