Diversity and distribution of Odonata (Insecta) larvae along an altitudinal gradient in Coalcomán mountains, Michoacán, Mexico.

Evaluating components of landscape diversity is essential for the implementation of efficient conservation strategies. We evaluated the diversity of Odonata larval assemblages from the Coalcomán mountains (CM), Michoacán, Mexico, and related it to local (site-level) habitat variables. Larvae were collected from shores, riffles and pools in five streams, counted and identified to species, twice per season during 2005. The Shannon Diversity Index (H'), Margalef's Richness Index (R), Simpson's Index as a dominance measure (D) and Pielou's Equitability (J) were used to describe the assemblages, and Renyi's Diversity Profiles were used to order diversity. A Bray-Curtis Similarity Index (BC) was used to evaluate beta diversity. Theoretical richness was estimated using non-parametric and parametric methods. A Canonical Correspondence Analysis (CCA) was applied to explore the relationships of species with site-level environmental variables. A total of 12 245 larvae from 75 species, 28 genera and 8 families were recorded. Over all sites, the dominant species were Erpetogomphus elaps, Macrothemis pseudimitans and Argia pulla. The number of species per locality ranged from 18 to 36, and a high number of species (76%) occurred with relative abundances lower than 1%. A differential distribution of species and abundance in streams, time and strata was observed. Renyi's diversity profiles showed diversity was higher in spring and on shores. Most BC similarity values were smaller than 25%, indicating a high turnover rate in the CM. The high turnover rate reflects a differential distribution of the species along the altitudinal gradient, supporting the hypothesis of Mexico as a betadiverse country. According to the slope of Clench's curve, a reliable list of species was gathered. The CM larval assemblage is currently the largest reported for Mexico, and our results support previous proposals of the CM as a species-rich area for conservation.

Association of study type, sample size, and follow-up length with type of recommendation produced by the National Institute for Health and Clinical Excellence Interventional Procedures Programme.

OBJECTIVES: The association between type and amount of clinical evidence and type of National Institute for Health and Clinical Excellence recommendations for interventional procedures was examined. METHODS: The evidence about 736 studies (including 183,729 patients) relating to 130 different interventional procedures and about relevant recommendations was analyzed. Associations were examined between type of recommendation ("normal arrangements" or "cautionary guidance") and evidence type, total number of treated patients, and mean follow-up length. Evidence type was categorized as (a) randomized, (b) nonrandomized controlled, and (c) case series/reports. The main outcome measures were frequency of evidence type, total number of patients treated, and mean follow-up length, by type of recommendation. RESULTS: "Normal arrangements" recommendations were made for 70 (54 percent) procedures and "cautionary guidance" was issued for 60 (46 percent) procedures. Procedures supported by at least one randomized study (34 percent, n = 44) were more likely to receive a "normal arrangements" recommendation (relative risk 1.38, p = .063). Overall, there were 85 (12 percent), 135 (18 percent), and 516 (70 percent) studies in categories a-c, respectively. The number of treated patients was significantly larger among procedures with "normal arrangements" (median, 605; range, 26-6,842) than among those with "cautionary guidance" (median, 240; range, 1-3,261; p < .001) recommendation. Mean follow-up length was longer in studies relating to procedures with "normal arrangements" recommendation (median, 16.7; range, 0-84 months) compared with those with "cautionary guidance" (median, 14.6; range, 0-67 months; p = .160). CONCLUSIONS: Procedures supported by randomized studies, and with larger numbers of patients and longer follow-up length, were more likely to receive positive guidance. Future research and development on interventional procedures should aim to produce better and more relevant evidence to optimize the possibility of such procedures being accepted by policy makers.