Diversity: taxonomic

Across diverse taxonomic groups of marine organisms there are several classes of compounds that absorb UV and act as putative sunscreens. These include scytonemin (Figure 15.9), an extracellular cyanobacterial sheath pigment, and the mycosporine-like amino acids (MAAs, Figures 15.3-15.6) that are usually located intracellularly in cyanobacteria, algae, invertebrates, and fish. These compounds are the major focus of this chapter and will be discussed in detail below. 

Annex V of the WFD lists the three main parameters of the macroinvertebrate community to be focused on for ecological assessment diversity, taxonomic composition and abundance, and the ratio of disturbance-sensitive taxa to insensitive taxa. Restoration from moderate to at least good status is required when these parameters differ from type-specific reference conditions to an extent coincident with the absence of major taxonomic groups. These parameters are not exclusive and others may be included to achieve the overall aim of an ecological status designation of the WFD as an expression of the quality of the structure and functioning of aquatic ecosystems (WFD, Article 2). 

Global patterns of moss diversity taxonomic and molecular inferences. Taxon 54,337-352. 

Studies of microbial degradation of toxicants in the root zone of plants have included a variety of plemt types from diverse taxonomic families (Table 1). These studies have been generated from examination of agrochemicals, aquatic systems, and industrial chemicals and are summarized below. Recently, two reviews on microbial degradation of organic compounds in the rhizosphere and the beneficial effects of vegetation at contaminated sites have been published [17,18]. 

Wickerham, L.J. 1958. Sexual agglutination of heterothallic yeasts in diverse taxonomic areas. Science 158 1504-1505. 

Other groups of biota are able to bring about transformation of structurally diverse compounds and limited investigations have revealed the metabolic potential of taxonomically diverse eukaryotic organisms ... 

Periphyton are microscopic and macroscopic algae that attach to and grow on solid surfaces, such as lake bottoms, rooted aquatic vegetation, and submerged woody debris. Periphyton form part of the base of littoral food webs in lakes. Periphyton communities are taxonomically diverse and the attached communities contain other organisms, such as bacteria and zooplankton, as well as detrital material. Periphyton vary seasonally and annually in both abundance and species composition. 

Contrary to the structure similarity of the pheromones secreted by taxonomical related moths, some differences are necessary for their sexual communication systems to play an important role in their reproductive isolation. In addition to further modifications of the various structures, diversity of the lepidopteran sex pheromones is generated by blending multiple components. Innumerable pheromone blends are based not only on combinations of different components but also on variations in the mixing ratio. A pioneer study with Adoxophyes spp. (Tortricidae Tortricinae) had already proposed this concept in the early 1970s. While the smaller tea tortrix (A. honmai) and the Japanese summerfruit tortrix (A. oranafasciata) had been considered to be variant strains with different host preferences in the same species, Tamaki et al. found that females of the former pest insect in the tea garden secreted Z9-14 OAc and Zll-14 OAc in a ratio of 7 4 but females of the latter defoliator of apple trees secreted them in a ratio of 13 4 [127,128]. Furthermore, two other components (Ell-14 OAc and MelO-12 OAc) were subsequently identified from the former species [129]. 

Plants produce an amazing diversity of secondary metabolites that not only play important biological roles in their adaptation to environments but also provide humans with dyes, flavors, drugs, fragrance, and other useful chemicals. However, many of the secondary metabolic pathways are found or are amplified only in limited taxonomic groups. In addition, the compounds are often restricted to a particular... 

The taxonomic diversity of freshwater macroalgae represents a counterpoint to the diversity of these groups in marine systems. Fewer than 3% of the 4,000 species of rhodophytes occupy freshwater habitats, and most occur in lotic, or flowing-water, systems (Sheath 2003). Similarly, only five of the seven species of freshwater brown algae (Phaeophyceae) have been recorded from North America (Wehr 2003). In contrast, more than 75% of the over 4,000 species of aquatic chlorophytes have been isolated from freshwater habitats, including many filamentous and colonial forms (Graham and Wilcox 2000). 

For those who are impatient, I note Amann s estimate that If there are just [emphasis added] one million species that ultimately can be cultured and if their complete taxonomic description proceeds at a rate of 1,000 species/year it would take roughly the next miUenium to get a fairly complete overview on microbial diversity. My own experience tells me that if there are, say, 50,000 truly distinctive bacterial species still unknown, their isolation and characterization will be a long time in coming. 

The conclusion is that the taxonomic diversity is larger in the sea than on land. 

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