Local versus regional species richness in tropical insects: one lowland site compared with the island of New Guinea

1. The overlap in species composition of Cercopoidea (Aphrophoridae, Cercopidae, and Machaerotidae), Flatidae, and Ricaniidae between two data sets, an almost exhaustive census from 13 Ficus species and a sample from diverse vegetation in the same area, led to the estimate for local species richness of 111 (SE 11.5) species (45 species of Cercopoidea, 36 species of Flatidae, and 30 species of Ricaniidae) at a lowland rainforest site in New Guinea. 2. Samples restricted to 13 species of Ficus contained 66 species, i.e. 59% of the estimated local species richness. This high proportion probably results from the high proportion of polyphagous and tourist (transient) species in the Cercopoidea, Flatidae, and Ricaniidae. 3. The two largest museum collections of New Guinean insects contained 327 species of Cercopoidea from New Guinea, including 23 of the 34 species collected in the field samples. This overlap led to the estimate of 483 (SE 97.2) species of Cercopoidea present in New Guinea. 4. The species found in the field samples were also 2.6 times more likely to be found in the museum collection than other species. This sampling bias can be due to a positive correlation between species local abundance and geographic distribution and/or similar patterns of species abundance at different sites. 5. The estimate of species richness of Cercopoidea in New Guinea increased to 1222 species when corrected for this sampling bias. Thus, only 4% of the New Guinean species were present locally, in the study area. Such high beta diversity is probably a consequence of the exceptional habitat and vegetation diversity in New Guinea, as well as its complex geological history.     

Isolation and biochemical characterization of two soluble iron(III) reductases from Paracoccus denitrificans.

Two soluble enzymes (FerA and FerB) catalyzing the reduction of a number of iron(III) complexes by NADH, were purified to near homogeneity from the aerobically grown iron-limited culture of Paracoccus denitrificans using a combination of anion-exchange chromatography (Sepharose Q), chromatofocusing (Mono P), and gel permeation chromatography (Superose 12). FerA is a monomer with a molecular mass of 19 kDa, whereas FerB exhibited a molecular mass of about 55 kDa and consists of probably two identical subunits. FerA can be classified as an NADH:flavin oxidoreductase with a sequential reaction mechanism. It requires the addition of FMN or riboflavin for activity on Fe(III) substrates. In these reactions, the apparent substrate specificity of FerA seems to stem exclusively from different chemical reactivities of Fe(III) compounds with the free reduced flavin produced by the enzyme. Observations on reducibility of Fe(III) chelated by vicinal dihydroxy ligands support the view that FerA takes part in releasing iron from the catechol type siderophores synthesized by P. denitrificans. Contrary to FerA, the purified FerB contains a noncovalently bound redox-active FAD coenzyme, can utilize NADPH in place of NADH, does not reduce free FMN at an appreciable rate, and gives a ping-pong type kinetic pattern with NADH and Fe(III)-nitrilotriacetate as substrates. FerB is able to reduce chromate, in agreement with the fact that its N-terminus bears a homology to the previously described chromate reductase from Pseudomonas putida. Besides this, it also readily reduces quinones like ubiquinone-0 (Q0) or unsubstituted p-benzoquinone.     

Transport across epithelia: A kinetic evaluation

Compartmental analysis of three models for solute transport across epithelial tissue is presented. The simplest model describes only one tissue compartment, the second incorporates the notion of a pore as a parallel pathway and the third model introduces a serial compartment corresponding to non-epithelial portions of the tissue. Experimental data were obtained, using a modified Ussing and Zerahn technique ((1951) Acta Physiol. Scand. 23, 110–127), for salicylate transport across rat jejunum in vitro and analyzed in terms of these three models. The conclusions based solely on the mathematical analysis of this rather simple experiment are: the tissue is not a homogeneous penetration barrier as often considered. Transport is not limited by unstirred layers either at the tissue surfaces or within the tissue itself. Salicylate is not passively transported. Parallel transport pathways do exist.     

Bimolecular systems: III. Catalytic systems

Amplification effect in the catalytic bimolecular systems is a consequence of the kinetic characteristic of the catalyst. Two types of the coefficient of amplification are defined. The applicability of these definitions is given by the type of the bimolecular system. In a simple example it is shown that the concept of amplification is meaningful in these systems. Furthermore, two rules, analogous to those for a coupling of amplifiers, are derived for the two basic modes of coupling of catalytic systems. Thus, in biological systems the catalytic reactions may be regarded as biologically effective amplifiers.     

Kinetics of cyclic AMP in toad bladder

Tissue distributions of cyclic [³H]AMP and [¹⁴C]inulin in toad bladder were determined and their kinetics analyzed. We found that both the epithelial and the other cells of the toad bladder handcle cyclic AMP similarly. Moreover, we found that the distribution of cyclic AMP did not differ from that of inulin, an extracellular marker. Kinetic analysis suggests that the rate of coefficient of cyclic AMP metabolism is much larger than the exchange rate coefficient, which explains why distribution of both cyclic AMP and inulin are similar.     

Bimolecular systems: II. Nonlinear systems of complexes

This paper deals with bimolecular systems in which also complex-complex interactions occur. Because of the complexity of the problem, an approximation in a form of coupled linear systems of complexes (Bull. Math. Biophysics,29, 1–16, 1967) is considered. Two types of couplings, serial and parallel, are studied. In the serial coupling the nonlinear system of complexes has the same behavior as its subsystems. An entity, initial sensitivity, has interesting properties: in serial coupling it is at most equal to the product and in parallel coupling, at most equal to the sum of partial initial sensitivities.     

Influence of tourism on dwarf pine (Pinus mugo) communities in the Vysoké Tatry Mountains

The attention was focussed on the evaluation of the impact of trampling on autochtonous dwarf pine communities in the Tatra National Park (Vysoké Tatry Mts.). Use was made of combined phytocoenological and production-ecological methods. Results are described and discussed according to floristic-phytocoenological analyses, production-ecological analyses and the basic parameters of total organic matter supply.