A phytochemical study has been carried out on the aerial parts of Salvia pachyphylla and S. clevelandii. From S. pachyphylla, the known diterpenes carnosol (2), rosmanol, 20-deoxocarnosol (3), carnosic acid, isorosmanol (4), 7-methoxyrosmanol, 5,6-didehydro-O-methylsugiol (5), 8beta-hydroxy-9(11),13-abietadien-12-one (6), 11,12-dioxoabieta-8,13-diene, and 11,12-dihydroxy-20-norabieta-5(10),8,11,13-tetraen-1-one were isolated, together with the new diterpene pachyphyllone (1). From S. clevelandii, the known diterpenes rosmadial (7), 16-hydroxycarnosol (8), abieta-8,11,13-triene, and taxodone were obtained, together with carnosol (2), rosmanol, and carnosic acid. The structure of the new compound (1) was identified on the basis of spectroscopic data analysis. Several of these compounds (1-8) were evaluated against a small panel of human cancer cell lines.

Through tabular and average linkage cluster analyses, 737 phytosociological relevés were classified. Based on these relevés, we described and typified the associations, alliances, orders, and classes grouping the coastal plant communities of the Baja California peninsula. Diagnostic tables, classification by average linkage clustering, and climatic, edaphic, and biogeographical data were used to establish floristic affinities among these syntaxa and to interpret their distributions. Syntaxa were characterized by their floristic composition, physiognomy, and biogeographical distribution, along with their positions in halophilous and psammophilous gradients. Thirtythree associations were identified, of which 22 are here described for the first time. Our syntaxonomical proposal includes descriptions of nine new alliances, seven new orders and four new classes: Allenrolfeetea occidentalis, Atriplici julaceae-Frankenietea palmeri, Euphorbio leucophyllae-Sporoboletea virginici and Achyronichio cooperi-Abronietea villosae.

In this study of the Pacific coast of North America, from Baja California to Alaska, we evaluated the hypothesis that the floristic composition of azonal vegetation determines areas and distribution limits similar to those of the corresponding zonobiomes (ZB), and does so in response to the same macroclimatic changes occurring on the continental scale. To this end, 686 vascular plants of the different habitats found in 279 sites along this coastal strip were recorded. Using an objective classification system (Average Linkage Clustering) and factorial analysis, floristic data acquired in fieldwork were classified into groups, which were in turn related to regional macroclimates. Our main finding was that the azonal coastal vegetation follows a distribution model that is closely linked to the corresponding macroclimate. The four ZB of the northern Pacific coast show a flora and azonal vegetation characteristic to each zonobiome; the latitudinal limits of the azonal vegetation practically coinciding with those already established for the zonal vegetation. The Boreal and Temperate ZB show high percentages of broadly distributed elements. The floristically richest zonobiome in terms of endemic taxa is the Mediterranean zonobiome, whereas the flora of Baja California is characterized by a high number of taxa related to Neotropical flora, especially to those showing links with South America. Data on the geographical distribution and habitats of the 247 most significant coastal species are also provided.

Aim The absence of Sonoran Desert plants in late Pleistocene‐aged packrat middens has led to speculation that they survived glacial episodes either in refugia as intact associations (Clementsian community concept) or in dry microsites within chaparral or woodland according to individualistic species responses (Gleasonian community concept). To test these hypotheses, we developed a midden record from one likely refugium in north‐eastern Baja California, Mexico. We also measured stomatal guard cell size in fossil leaves to further evaluate site‐level individualistic responses of Larrea tridentata (creosote bush) ploidy races to climatic changes, including monsoonal history, over the late Quaternary. Location Sierra Juárez, Lower Colorado River Basin, north‐eastern Baja California, Mexico. Methods Packrat (Neotoma) middens were collected from ˂ 300 m elevation on the eastern piedmont of the Sierra Juárez. Plant macrofossils and pollen were analysed from 50 dated middens, including determination of Larrea tridentata ploidy races. Results Pleistocene middens dating back to > 55,000 cal. yr bp contained a mix of extralocal species characteristic of chaparral and pinyon–juniper–oak woodland, along with some modern desert elements. Many other desert taxa were absent during the Pleistocene, although most had arrived by the beginning of the Holocene 11,700 years ago. Main conclusions The assemblage of chaparral, woodland and select desert elements refutes the hypothesis that the Lower Colorado River Basin served as a late Pleistocene refugium for Sonoran Desert flora. The rapid arrival of most missing desert species by the early Holocene suggests they did not have far to migrate. They probably survived the last glacial period as smaller, disparate populations in dry microsites within chaparral and pinyon–juniper–oak woodlands. Diploid and tetraploid races of Larrea tridentata were present during the Pleistocene, but hexaploids did not appear until the mid‐Holocene. This demonstrates that individualistic responses to climate involved genetic variants, in this case cytotypes, and not just species.

Thalidomide, mainly used for the treatment of leprosy, is a current teratogen in South America, and it is reasonable to assume that at present this situation is affecting many births in underdeveloped countries. Moreover, the potential re‐marketing of thalidomide for the treatment of a large variety of diseases may extend the problem to the developed world. When the drug is available, the control of its intake during early pregnancy is very difficult since most pregnancies are unintended. The ongoing occurrence of thalidomide embryopathy cases went undetected by the ECLAMC, due to several factors: (1) low populational coverage through this monitoring system; (2) pre‐existence of the teratogen with its effects present in both baseline (expected) and monitored (observed) materials; and (3) lack of a defined phenotype to be monitored. Thus, if thalidomide re‐enters the market throughout the world, due to the wide range of new applications, occurrence of phocomelia alone might not be sufficient to detect its effects. By a case‐reference approach, the ECLAMC registered 34 thalidomide embryopathy cases born in South America after 1965 whose birthplaces correspond to endemic areas for leprosy. Phocomelia was found in five of eleven fully described cases. Thus, phocomelia alone is neither specific nor sufficient to serve as a suitable phenotype to survey the teratogenic effects of thalidomide. Therefore, a thalidomide‐like phenotype, defined as any bilateral upper and/or lower limb reduction defect of the preaxial and/or phocomelia types, should be included in the routine surveillance of birth defects in all programmes. Teratology 54:273–277, 1996. © 1997 Wiley‐Liss, Inc.

Abbreviations cal yr BP = calibrated years before present; CHAR = charcoal accumulation rate; ENSO = El Niño/Southern Oscillation; PDSI = palmer drought severity index Nomenclature www.itis.gov AbstractObjective: To assess potential causes of woody plant encroachment into desert grassland systems using a 5500-yr-old sediment record from a ci enega in New Mexico.Location: Cloverdale Ci enega, southwestern New Mexico.Methods: Utilizing fossil pollen and charcoal preserved in wetland sediments, a long-term record of variations in vegetation composition and fire activity was generated. The record was compared to published data on drought, the El Niño/ Southern Oscillation (ENSO), carbon dioxide concentrations and known dates of grazing impacts to evaluate various hypotheses regarding the timing and causes of woody plant encroachment in desert grasslands. Results:The woody plant encroachment observed in the past 200 yrs is unprecedented in the context of the previous 5500 yrs of vegetation history. The observed increase in woody plant abundance was not related to droughts or changes in ENSO event frequency, and was contemporaneous with the rise in atmospheric CO 2 and known grazing impacts. Charcoal influx increased in conjunction with historic woody plant pollen abundance and therefore the encroachment was not related to fire exclusion. Conclusions:The long-term sediment record from Cloverdale Ci enega provides the context for evaluation of the various hypotheses for woody plant encroachment. At Cloverdale Ci enega we demonstrate that woody plant encroachment of the last 200 yrs is unprecedented and outside of the historic natural range of variability of the previous five millennia. We also demonstrate that woody plant encroachment is not related to climatological changes such as drought or increases in ENSO frequency. Increases in woody plant pollen are associated with increases in carbon dioxide, and high-intensity grazing during the late 19th and early 20th centuries.

The area between Ensenada and El Rosario (Baja California, Mexico) has long been considered as a transitional zone in which two great ecoclimatic regions (Mediterranean and Tropical-Desert) overlap. The floristic and biotypical diversity of this area was evaluated by analyzing its shrubland formations from a phytosociological point of view. This phytosociological study, carried out according to the Braun-Blanquet method and supported by cluster analysis, describes sixteen shrubland associations from Northwestern Baja California.Floristic diversity of the transitional zone was evaluated using two indices, endemic value (EV) and endemic community value (ECV), which are related to the degree of endemism in the flora and plant associations. The phytosociological analysis showed that the high number of shrubland associations found in this area reflected its transitional character. The closer the associations are to the transitional zone, the higher their biotypical and floristic diversity.

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