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Mitotic chromosomes of 12 species ofCatasetumwere assessed to contribute with the karyotypic study of the subtribe Catasetinae (Orchidaceae), expanding the knowledge of this group in terms of chromosomes and supporting its taxonomic and evolutionary analysis. The species are maintained in cultivation in the greenhouse of the Department of Plant Biology/IB/UNICAMP and in the “Orquidário Frederico Carlos Hoehne” of the Botanical Garden of São Paulo. Chromosome counts ranged from 2n = 54 to 2n = 108. Karyotypes were prepared for all species studied, in which there was a predominance of metacentric chromosomes and some submetacentric ones. The chromosome size ranged from 0.5 to 4.9 μm, the total chromosome length ranged from 34.7 to 78.7 μm and the asymmetry index TF% ranged from 21.2 to 42.3. The results obtained so far favor the taxonomy of the genus, allowing to distinguish species with very similar external morphology. [ABSTRACT FROM AUTHOR]

: We do an analytical study of the statistical properties of an ecosystem composed of species that are coupled via pairwise interactions that are given by the Hebb rule and have deterministic self-interactions u. In the model each species is characterized by an infinite set of p = αN traits. As one of our main results, we observe that the ecosystem becomes less cooperative as the complexity of species (number of traits) is increased. [ABSTRACT FROM AUTHOR]

The statistical properties of an ecosystem composed of species interacting via pairwise, random interactions and deterministic, concentration limiting self-interactions are studied analytically with tools of equilibrium statistical mechanics of disordered systems. Emphasis is given to the effects of externally induced extinction of a fixed fraction of species at the outset of the evolutionary process. The manner the ecosystem copes with the initial extinction event depends on the degree of competition among the species as well as on the strength of that event. For instance, in the regime of high competition the ecosystem diversity, given by the fraction of surviving species, is practically insensitive to the strength of the initial extinction provided it is not too large, while in the less competitive regime the diversity decreases linearly with the size of the event. In the case of large extinction events we find that no further biotic extinctions take place and, furthermore, that rare species become very unlikely to be found in the ecosystem at equilibrium. In addition, we show that the reciprocal of the Edwards-Anderson order parameter yields a good measure of the diversity of the model ecosystem.

This manuscript is a review of the innovative methodologies that enable more precise evaluations of soil microbial diversity. Highlighting the molecular approach, which does not require the isolation of microorganisms and allows the inclusion of non-culturable genotypes in the analyses, the described methodologies revolutionised the environmental microbiology and opened gateways for an accurate understanding of the ecology and diversity of microorganisms. The application of techniques based on soil total DNA extraction, PCR amplification of genes or gene fragments, and sequence analysis revealed that the microbial universe is far more complex than ever imagined. Examples of applications of the molecular approach to study the diversity of soil diazotrophic bacteria are given.