DILLON, MICHAEL O. Botany Department, The Field Museum, Chicago, IL 60605-2496. - Biogeography and diversity of the Solanaceae in the lomas formations of Chile and Peru.
The western coast of South America [5-30°S lat] is dominated by desert
conditions that form a continuous, hyper-arid belt, broken only by
occasional river valleys. The native, non-riparian vegetation of these
deserts is largely confined to localities where recurring fogs meet
the near shore terrain. The fogs supply moisture for the development
of unique plant communities termed lomas formations. Over 100 of these
communities have been identified and they exist as terrestrial islands
within the ocean of arid habitat ranging over 3500 kms from northern
Peru to north-central Chile. Endemism reaches over 40% at some
localities. The combined vascular flora of the lomas formations
contains over 1400 species and the Solanaceae is represented by 19
genera and 129 species arrayed in five subfamilies: Cestroideae,
Nicotianoideae, Petunioideae, Schizanthoideae, and Solanoideae.
Lomas endemics are found in the following 11 genera:
Exodeconus, Grabowskia, Leptoglossis,
Lycopersicon, Lycium, Nolana, Nicotiana,
Reyesia, Salpiglossis, Schizanthus and
Solanum. Nolana, with 71 endemic lomas species,
stands out as the largest and most wide-ranging genus of the lomas
flora and the only one to be encountered in nearly all lomas
formations. A suite of Nolana species have been investigated
using ITS and matK sequence data to reconstruct phylogenies and
these have yielded conflicting results. Morphological and
physiological specializations that have allowed species
diversification were examined in relation to suggested phylogenies.
The biogeographic patterns within the Solanaceae lomas endemics
reflect different arrival times and origins for its members.
Short-term climatic fluctuations, such as El Niņo events, and
longer-term climatic change associated with glacial cycles, are
believed to have been influential in expansions and contractions in
the flora of Andean Cordillera and the coastal deserts and have helped
shape present-day distributional patterns.
Key words: Atacama Desert, biogeography, Lomas formations, Peruvian Desert, Solanaceae