No abstract

No abstract

Mycotoxins are secondary metabolites produced by many important phytopathogenic and food spoilage fungi including Aspergillus, Fusarium and Penicillium species. The toxicity of four of the most agriculturally important mycotoxins (the trichothecenes, and the polyketide-derived mycotoxins; aflatoxins, fumonisins and sterigmatocystin) are discussed and their chemical structure described. The steps involved in the biosynthesis of aflatoxin and sterigmatocystin and the experimental techniques used in the cloning and molecular characterisation of the genes involved in the pathway are described in detail. The biosynthetic genes involved in the fumonisin and trichothecene biosynthetic pathways are also outlined. The potential benefits gained from an increased knowledge of the molecular organisation of these pathways together with the mechanisms involved in their regulation are also discussed.

No abstract

1. Ecological convergence in morphology among taxa of distinct evolutionary histories is a common illustration of the efficacy of natural selection. Ecological convergence is often enabled by functional redundancy of complex morphological structures, such that modification of existing morphologies in response to similar functional requirements can lead to the development and evolution of morphological diversity. Thus, studies of the mechanisms that enable the development of similar adaptations in taxa with distinct morphologies provide important insights into both the evolution of past adaptations and patterns of future evolutionary divergence. 2. Here, we examine mechanisms that have enabled ecological convergence in foraging morphology among four geographically isolated and morphologically distinct populations of shrews: southeastern Arizona and north-central New Mexico populations of the montane shrews (Sorex monticolus) and northern California and north-central Montana populations of the vagrant shrew (S. vagrans). 3. We show that despite overlap in diet, populations had distinct skeletal and muscular morphologies of the mandible. This association between ecological convergence and morphological uniqueness among populations was enabled by versatility of foraging morphologies that generated similar functional outputs. 4. In addition, we found that populations exhibited unique skeletal and muscular correlations with diet suggesting that distinct muscular and morphological components of the complex foraging apparatus can be used for a particular resource. This result corroborates a previous finding that extensive modularity in mandibular development allows diverse morphologies to generate equivalent functions and utilize similar resources across taxa. 5. Synthesis. We conclude that the observed functional and ecological convergences resulted from population-specific musculoskeletal interactions, and suggest that the differences in skeletal and muscular morphologies observed among these populations reflect evolved differences in plasticity of the skeletal and muscular components of the mandible.