Discriminant function and cluster analyses were performed on 19 morphometric variables of the aculeus, wing and mesonotum to determine whether populations of Anastrepha fraterculus (Wiedemann) from different parts of Mexico could be distinguished from populations from South America. Samples were collected from seven localities across Mexico, two from Brazil, and one each from Colombia and Argentina. Results showed there were statistically significant differences between Mexican and South American populations with respect to the aculeus (tip length, length of serrated section, mean number of teeth) and wing (width of S-band and connection between S- and V-bands). The degree of morphological variation observed among Mexican populations was extremely low, and as a consequence, the Mexican populations were identified as a single morphotype by discriminant analysis. The 'Andean morphotype'consisting of the Colombian population, and the 'Brazilian morphotype'consisting of the two Brazilian populations plus the single Argentinian population were also distinguished. It was concluded that the macro-geographical morphotypes from Mexico, Colombia, and Brazil plus Argentina correspond to three distinct taxonomic entities. Comparisons of results with those obtained from behavioural, karyotypic, isozyme and DNA studies suggest that sufficient evidence now exists to name a new Mexican species from within the A. fraterculus complex. This will be done in a separate publication. A provisional key to the morphotypes of A. fraterculus studied is provided.

The composition and temporal changes of edaphic microarthropods in both litter layer and soil were analyzed in a tropical dry forest ecosystem in Western Mexico. Sampling was carried out from June 1991 to July 1992 in two small watersheds at the Chamela Biological Station (Jalisco State, Mexico). At each watershed 10 random cores samples, 11 cm in diameter and 5 cm depth, were taken monthly from each biotope from an area of 100 m 2 . Fauna was extracted by Berlese-Tullgren funnels and preserved in 75% ethanol. The total abundance of arthropods was 96,338 specimens, belonging to 33 taxa. Numerically dominant groups were Prostigmata, Cryptostigmata, Collembola and Mesostigmata, which constituted 92.6% of the total abundance. The effect of current monthly precipitation and temperature on density of total Arthropoda and different Orders was also investigated. Precipitation and temperature were significantly correlated with Collembola and Mesostigmata densities and also with total arthropod. The seasonal variation in the amount of litterfall was also significantly related to the abundance of arthropod in the litter layer biotope.

Odonate diversity in the Coalcomán Mountain Range (CMR), Michoacán State, Mexico, was surveyed, and samplings were made during 2 years in eight streams along an altitudinal gradient. Presence-absence data were analyzed using non-parametric and parametric methods. Beta and gamma diversities were estimated using Whittaker's and Lande's formulae, respectively. A total of 2,526 adults and 489 larvae were captured, yielding 116 species (c diversity), 44 genera and 9 families. Five new species were discovered. The genus Argia was the most important contributor to Zygoptera diversity and total richness (c diversity), yielding 40.4 and 14.7%, respectively. The non-parametric estimator Chao2 provided the closest theoretical estimate of species richness, and Clench's model fit the data well (R 2 ranged from 99.44 to 99.99) to explain a high proportion of the variance (98.8). We conclude that beta diversity is important at the landscape scale, supporting the hypothesis that Mexico is a beta diverse country. Our results triple the number of known species of Odonata for Michoacán. Given the considerable richness of odonates at local and landscape scales, our results support the proposal of the Coalcomán Mountain Range as a priority area for conservation and related research.

1. Assessing species richness (SR) and diversity along environmental gradients is important to see whether abiotic differences alter patterns of species distribution and composition.2. We examined distributions of odonate SR, average taxonomic distinctness (ATD) and functional diversity (FD) (using the Shannon Index on proportions of plant-dependent and non-dependent species) with elevation and slope provided from an exploratory survey along a transect in the Sierra de Coalcoma´n Mountains, Michoaca´n State, Mexico. Adults were collected along both sides of a 500 m stream segment for 6 h day )1 site )1 in each of eight sites, and these species lists were complemented by collecting mature larvae.3. Species richness and FD declined with elevation among windward sites, while ATD increased. Among leeward sites, SR peaked at mid-elevation, and there was no trend for FD or ATD with elevation. Leeward sites were similar in species composition, whereas windward sites were dissimilar. Slope was correlated with elevation among windward sites, and influenced most variables, but not among leeward sites. FD was negatively correlated with ATD among sites along both aspects. Mean values of SR, ATD and FD between aspects were similar.4. The Energy-Richness Hypothesis best explained the species distributions along the windward aspect. Local abiotic influences appeared more important in community assembly among windward sites. Among leeward sites, the potential for Mid-Domain and Rapoport Effects suggest interspecies interactions control community assembly; providing greater potential for expansion of species elevational ranges, and an increase in range expansion of alien and non-endemic species along this aspect.

Resumen. Se describen y comparan los ensamblajes de coleópteros de las temporadas de lluvias y sequía del bosque mesófi lo de montaña de Tlanchinol, Hidalgo, que se obtuvieron en 8 recolectas mensuales usando trampas de intercepción de vuelo. Para la descripción de los ensamblajes se tomó en cuenta su riqueza, composición, diversidad, equidad y dominancia y se compararon con base en los perfi les de diversidad de Renyi. El recambio de especies se evaluó usando el índice de similitud de Bray-Curtis. Se estimó la riqueza teórica del ensamblaje total y por temporada, se exploró la relación entre los taxa y los meses de recolecta, y las especies se ubicaron en grupos funcionales. Los 3 308 ejemplares recolectados pertenecen a 50 familias y 352 especies, siendo Staphylinidae, Curculionidae y Nitidulidae las familias con el mayor número de especies. La riqueza, abundancia y diversidad de la época de sequía fueron signifi cativamente mayores que las de lluvias. La mayoría de las especies poseen abundancias inferiores a 1% conformando las especies raras. Teóricamente aún faltan taxa por recolectarse en Tlanchinol. La mayoría de las especies se ubicaron en la categoría de los depredadores (43%) y fi tófagos (20%). Los resultados resaltan la gran biodiversidad de estos bosques y su urgente necesidad de protección.