Diversity and seasonal variation of ground and understory spiders from a tropical mountain cloud forest.

We made intensive samplings to study the seasonal response of spiders across different forest strata (ground and understory) in a tropical mountain cloud forest from Mexico. We sampled spiders from ten plots in six sampling events during the dry and rainy season, to analyze their abundance, structure (distribution of abundance among species), diversity and the response of the five dominant species at each stratum. Results demonstrated that seasonal patterns of spider communities differed among strata, revealing a complex spatiotemporal dynamic. Abundance, structure, diversity of ground spiders, as well as the responses of four dominant species at this stratum, showed low seasonal variations. In contrast, a strong seasonal variation was observed for the understory assemblage, with lowest abundance and highest diversity in the rainy season, and different assemblage structures for each season. Seasonal patterns of each assemblage seem linked to the responses of their dominant species. We found high co-occurrence among most of the ground dominant species with similar habitat use and with multivoltine patterns, contrasting with low co-occurrence among most of the understory dominant species with similar habitat use and univoltine patterns. Our results showed that the spiders' assemblages of tropical mountain cloud forest (opposed to what is found in temperate and boreal forests) increase their species richness with the height, and that their responses to seasonal change differ between strata. Management programs of these habitats should consider the spatial and temporal variations found here, as a better understanding of their ecological dynamics is required to support their sustainable management.

Interactions between abundant fungal species influence the fungal community assemblage on limestone.

The assembly of fungal communities on stone materials is mainly influenced by the differential bioreceptivity of such materials and environmental conditions. However, little is known about the role of fungal interactions in the colonization and establishment of fungal species. We analyzed the effects of intra- and interspecific interactions between 11 species of fungi in oligotrophic and copiotrophic media and on limestone coupons. In a previous study, these species were the most frequently isolated in the epilithic biofilms of limestone walls exposed to a subtropical climate. In the culture media, we found a greater frequency of intra- and interspecific inhibitory effects in the oligotrophic medium than in the copiotrophic medium. On the limestone coupons, all fungi were able to establish; however, the colonization success rate varied significantly. Cladosporium cladosporioides had a less extensive colonization in isolation (control) than in dual interactions (coexistence) with other species. Phoma eupyrena exhibited the highest colonization success rate and competitive dominance among all tested species. X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses revealed that Pestalotiopsis maculans and Paraconiothyrium sp. produced calcium oxalate crystals during their growth on coupon surfaces, both in isolation and in dual interactions. Our results demonstrate that interactions between abundant fungal species influence the fungal colonization on substrates, the biomineralization and the fungal community assemblage growing in limestone biofilms.

Succession of fungi colonizing porous and compact limestone exposed to subtropical environments.

Little is known about the dynamics of succession of fungi on limestone exposed in subtropical environments. In this study, the colonization of experimental blocks of compact and porous limestone by a fungal community derived from natural biofilms occurring on Structure X from the archaeological site of Becán (México), was studied using a cultivation-dependent approach after short-term (9 m) exposure in order to provide a preliminary insight of the colonization process under seminatural conditions. Microbial growth seen as the change of colour of stone surfaces to black/dark green was more abundant on the porous limestone. There was a fairly clear difference in microbial colonization between the onset of the experiment and the 6th month for both limestone types, but no significant increase in the colonization of coupons occurred between months 6 and 9. This could be related to the low rainfall expected for this period, corresponding to the dry season. A total of 977 isolates were obtained. From these, 138 sterile fungi were unidentified, 380 could only be assigned to the order Sphaeropsidales; the remaining isolates (459) were grouped into 27 genera and 99 different species. Nearly all detected fungal species belonged to the Ascomycota (90 %). Rare taxa (species represented by one to three isolates) included the recently described genus Elasticomyces, several species of genera Hyalodendron, Monodyctis, Papulospora, Curvularia, and Septoria. Other taxa were Minimedusa and Gliomastix luzulae, which have not been previously described for stone environments. Abundant fungi included several species of the common genera Cladosporium, Alternaria, and Taeniolella typical for a range of habitats. Succession of populations was observed for certain taxa, this shift in the composition of fungal communities was more evident in porous limestone. After 6 m of exposure, species of the genera Scolecobasidium, Hyalodendron, and Taeniolella were predominant, while after 9 m, the predominant species belonged to the genera Curvularia and Alternaria, particularly on porous stone. These results suggest that Curvularia and Alternaria replaced other fungi, due to a higher tolerance towards low levels of available water during the dry season. Higher levels of water within the porous stone, keep longer periods of microbial activity, minimizing the impact of desiccation. This study contributes to understand the diversity of fungal communities in stone surfaces in subtropical settings and the dynamics of colonization on limestone.

Effects of Phyllophaga (phytallus) hoegei larval density (coleoptera: melolonthidae) on plant and herbivore growth

La herbivoría subterránea ha recibido poca atención. La respuesta de las plantas a la herbivoría subterránea es variable y mediada parcialmente por la identidad y densidad del rizófago. En este estudio se evaluaron 1) los efectos de la herbivoría subterránea de dos densidades de Phyllophaga (Phytalus) hoegei en la biomasa de la planta y el contenido de nitrógeno de tallos y raíces del pasto nativo dominante Muhlenbergia quadridentata, y 2) los efectos de esas dos densidades de larvas en la supervivencia y crecimiento de esta especie. El experimento se llevó a cabo en un área de bosque de pino a 3200msnm. Las plantas se establecieron en macetas en el campo y estuvieron sujetas a herbivoría subterránea (tres niveles) en un diseño completamente al azar con diez repeticiones por tratamiento. Altas densidades del rizófago disminuyeron significativamente la biomasa de raíces y la proporción raíz/tallo, pero no varió la concentración de nitrógeno en los tejidos de las plantas. La sobrevivencia de las larvas de Phyllophaga hoegei no fue afectada por la densidad a la que crecieron, pero en altas densidades, la larva rizófaga disminuyó su tasa de crecimiento relativa y la ganancia de peso.

Soil macrofauna of two successional evergreen cloud forest stages from the cerro huitepec nature reserve San Cristóbal de Las Caras Chiapas México

Se estudió la composición de la macrofauna del suelo en dos estados sucesionales del bosque mesófilo. Uno es un bosque que tuvo uso forestal hace 17 años con un dosel <8m, densidades entre 900 y 1200 árboles con DAP >5cm; el otro es un bosque no manejado con un dosel entre 30 y 35m con densidades de 1600 a 1800 árboles con DAP >5cm. Chilopoda, Oligochaeta y Diplopoda constituyeron el 70 por ciento del total de la macrofauna en ambos ambientes. Los Oligochaeta endógeos fueron el grupo más abundante en ambos tipos de bosque, representando 54 por ciento del total de degradadores en el bosque maduro y su densidad fue significativamente mayor en comparación con el bosque incipiente. La disminución en la densidad de Oligochaeta se relacionó con menor cobertura del dosel, aumento en la temperatura del suelo y disminución en su humedad. El año de muestreos sugiere que después de 17 años desde que fue cortado el bosque, hay pocos impactos negativos sobre la macrofauna del suelo asociados al uso del bosque para la producción de carbón