The genus Lysipomia Kunth comprises approximately 40 species restricted to the paramo and wet puna of the northern and central Andes from 3000 to 5000 meters in elevation. Andean paramo and puna are areas above tree-line that superficially resemble alpine tundra, but are unique because of the extreme temperature fluctuations. This habitat is also characterized by high winds, large amounts of precipitation, and increased UV light levels. Due to these environmental extremes, Lysipomia has evolved specific morphological features such as short stature, thick stems, and persistent leaf bases. Using standard anatomical techniques, we investigated leaf anatomy of Lysipomia in order to discover whether specific anatomical features are synapomorphies or whether they have evolved independently many times in response to harsh environmental conditions. To test for homology vs. homoplasy anatomical features were mapped onto a cladogram that was derived from morphological and molecular data sets. Characters were compared among the species such as stomatal placement, presence of trichomes, thickness of epidermal layers, and variation of the pallisade parenchyma and spongy mesophyll throughout the leaf. The leaves of some species showed unique features that have not been reported elsewhere in the family Campanulaceae. The only species that lacked stomata and exhibited a majority of aerenchyma, L. aquatica, is found in submerged aquatic habitats. Lignified trichomes in L. lehmannii and L. aretiodes have independently evolved possibly in response to the high winds associated with the barren ridges they inhabit. Stalked stomata and highly thickened epidermal layers are found only in four species found in southern Ecuador and can be used as a synapomorphy for the clade. The anatomical study of Lysipomia illustrates how leaves in a tropical alpine plant can be modified in response to certain environmental conditions but not all of the novel adaptations are useful in phylogenetic analyses.

Key words: Andes, Campanulaceae, harsh environments, leaf anatomy