A phytogeographical characterization of the vine flora of the Sonoran and Chihuahuan deserts

Aim This study presents a phytogeographical characterization of the vine fl ora of two lower North American desert regions as a biogeographical framewo rk for further ecological inquiry into desert vines. Location The phytogeography of the vine flora of the Sonoran and Chihuahuan Deserts was characterized based on 263 known species. Methods Checklists of the vines of each desert were developed. Represented genera were then grouped into 10 phytogeographical elements based on worldw ide distribution patterns. To compare the floristic composition of the dese rt floras, an index of species similarity was calculated. Results About a third more species of vines occur in the Sonoran Desert tha n in the Chihuahuan Desert. Based on the analysis, cosmopolitan genera are the only group more numerous in absolute terms in the Chihuahuan Desert tha n in the Sonoran Desert. Tropical elements are represented in about the sam e proportion in each desert as the number of species, however, nearly twice as many pantropical and neotropical genera are represented in the Sonoran Desert as in the Chihuahuan Desert. Proportionately, more genera of tempera te elements occur in the Chihuahuan Desert than in the Sonoran desert, alth ough the absolute number of genera is slightly higher in the latter. Main conclusions As these deserts are relatively recent ecological formatio ns and as vines evolved in forest ecosystems, the composition of the desert vine floras is the result of the interaction between historical vegetation types, their constituent taxa and climatic and geological history. The mai n differences in the vining floras of the present-day Sonoran and Chihuahua n Deserts appear to be the result of greater historical influence in the So noran Desert of (1) tropical vegetation types and (2) the emergence of the Gulf of California. The Chihuahuan Desert vine flora seems to be the result of (1) a more pronounced historical temperate vegetation, (2) the lack of an important isolating event, such as the creation of the Baja California p eninsula, and (3) a cooler climate with shorter growing seasons.