w ww ww w. .f fr ro on nt ti ie er rs si in ne ec co ol lo og gy y. .o or rg g E dgar Anderson proclaimed that "man carries whole RESEARCH COMMUNICATIONS RESEARCH COMMUNICATIONS Effects of urbanization on plant species diversity in central ArizonaJ Ja as so on n S S W Wa al lk ke er r 1 1* * , , N Na an nc cy y B B G Gr ri im mm m 1 1 , , J Jo oh hn n M M B Br ri ig gg gs s 1 1, ,2 2 , , C Co or ri in nn na a G Gr ri ie es s 3 3 , , a an nd d L La au ur ra a D Du ug ga an n 4 4Modern urban development provides an excellent laboratory for examining the interplay among socioecological relationships. We analyzed how the rapidly urbanizing Phoenix, Arizona metropolis has affected plant species diversity and community composition at a regional scale. Species diversity and plant density probably result from abiotic sorting in undeveloped desert sites, but not in urban sites. We found that species richness at the plot scale was higher for desert as opposed to urban sites; however, the estimated total species pool in the urban ecosystem is higher than that in the desert, as a result of the increased importation of introduced species through the nursery trade. Ordination of plant communities suggests three unique groupings of species based on land-use type of the site (desert, urban, and agriculture) and two unique groupings of urban sites based on landscaping aesthetics (mesic or xeric). We therefore recognize both bottom-up and top-down controls of plant biodiversity within the urban ecosystem.

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A large‐scale survey of the Central Arizona‐Phoenix Long‐Term Ecological Research study area was conducted in which many kinds of samples were collected (e.g., plant, insect, soil). The plant samples were of a smaller size than typical herbarium accessions due to limitations in personnel, storage space, available plant materials, and time. The vouchers were identified in the field if possible. The vast majority of the rest were identified in the herbarium morphologically after the survey; less than 5% of the vouchers remained unidentified. Of these, a subset were subjected to molecular analysis using sequences of the nuclear ribosomal ITS region and to a BLAST search of sequences in GenBank to find closely related taxa. The close relatives along with the unknown specimens were subjected to maximum parsimony analysis to identify the potential phylogenetic relationships of the unknown specimens. Through this analysis nine unknown plant accessions were identified to family, tribe, genus, and species. Once this level of identification was established, some specimens were reexamined morphologically and compared with potentially related taxa in the herbarium to confirm or improve identifications. We outline an efficient method for surveying and collecting plant vouchers for a large sampling area. We also demonstrate that one can combine morphological and molecular data in the identification process to produce more complete datasets.

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