Ecophysiology and genetic diversity in species of the bamboo <i>Chusquea</i> in the high Andes, Venezuela

<b>Background</b>: Woody bamboos of the genus <i>Chusquea</i> grow along a broad range of elevations in the Venezuelan Andes. Their growth-form and density vary along the cloud forest – páramo gradient. In this article, we related ecophysiological traits and population genetic diversity information to explain the distribution of growth-form patterns of <i>Chusquea</i> in the Merida Andes, Venezuela. <b>Aims</b>: We quantified differences in the ecophysiological response and genetic diversity of scandent cloud forest and shrub-like páramo bamboos of the genus <i>Chusquea</i>, taking in account the differences in their flowering patterns, growth-form and habitat. <b>Methods</b>: 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 <i>Chusquea</i>. The genetic diversity study was based on Inter Sequence Simple Repeats and Random Amplified Polymorphic DNA markers analysis of cloud forest and páramo populations. <b>Results</b>: Scandent cloud forest and shrub-like páramo species of <i>Chusquea</i> 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 – páramo 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. <b>Conclusions</b>: Species of <i>Chusquea</i> 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.