Evaluating the costs and benefits of systematic data acquisition for conservation assessments

Effective decision‐making in conservation often is constrained by data quality. Uncertainties associated with poor quality or sparse data can lead to the misuse of limited resources and potentially the failure of conservation practice. Data acquisition, which can help improve decision‐making, is constrained by limited budgets and time. This is especially concerning for rare species, the most in need of conservation, but the most difficult to accurately represent in conservation plans. Here we test the suitability of three different sampling design strategies (two systematic vs random) designed to improve the quality of information available for conservation planning involving rare species. We modelled the spatial distribution of freshwater fish species in a data rich area in northern Australia using a large dataset (representing the best attainable data or true distribution) and simulate increasing subsets of data acquired through the three alternative sampling designs. We then evaluated omission and commission errors in conservation planning outcomes, efficiency and return on investment of data acquisition for conservation planning outcomes obtained from the different data availability × sampling design strategies. Even though we were able to find new species more effectively through systematic sampling designs, this did not 1) translate into reduced errors in conservation planning outcomes for rare species and 2) meet our goal of enhancing cost‐effectiveness of conservation planning. Our results suggest that collecting more biodiversity data, irrespective of the sampling design used, does not necessarily reduce data uncertainty issues and could lead to the misuse of the limited resources and ultimately the failure of conservation practice.     

Molecular coevolution among cryptically simple expansion segments of eukaryotic 26S/28S rRNAs

The set of "expansion segments" of any eukaryotic 26S/28S ribosomal RNA (rRNA) gene is responsible for the bulk of the difference in length between the prokaryotic 23S rRNA gene and the eukaryotic 26S/28S rRNA gene. The expansion segments are also responsible for interspecific fluctuations in length during eukaryotic evolution. They show a consistent bias in base composition in any species; for example, they are AT rich in Drosophila melanogaster and GC rich in vertebrate species. Dot-matrix comparisons of sets of expansion segments reveal high similarities between members of a set within any 28S rRNA gene of a species, in contrast to the little or spurious similarity that exists between sets of expansion segments from distantly related species. Similarities among members of a set of expansion segments within any 28S rRNA gene cannot be accounted for by their base-compositional bias alone. In contrast, no significant similarity exists within a set of "core" segments (regions between expansion segments) of any 28S rRNA gene, although core segments are conserved between species. The set of expansion segments of a 26S/28S gene is coevolving as a unit in each species, at the same time as the family of 28S rRNA genes, as a whole, is undergoing continual homogenization, making all sets of expansion segments from all ribosomal DNA (rDNA) arrays in a species similar in sequence. Analysis of DNA simplicity of 26S/28S rRNA genes shows a direct correlation between significantly high relative simplicity factors (RSFs) and sequence similarity among a set of expansion segments. A similar correlation exists between RSF values, overall rDNA lengths, and the lengths of individual expansion segments. Such correlations suggest that most length fluctuations reflect the gain and loss of simple sequence motifs by slippage-like mechanisms. We discuss the molecular coevolution of expansion segments, which takes place against a background of slippage-like and unequal crossing-over mechanisms of turnover that are responsible for the accumulation of interspecific differences in rDNA sequences.      

Role of light in the in vivo and in vitro synthesis of spinach thioredoxin f

Upon continuous illumination of dark-grown spinach ( Spinacia oleracea L. cv. Winter Giant) seedlings, the thioredoxin f (Td f) content (ELISA) showed a steep rise, which can be evaluated after 3 and 36 h illumination as 3 times and 10 times the dark value, respectively. These figures correspond to 0.03% and 0.1% of total soluble protein, which means a higher biosynthetic rate for Td f compared to the average of total proteins in the earlier steps of plant development. After 40-50 h light the Td f level reached its highest value which remained stable for an additional 40 h and then decreased. Pulse-chase in vivo experiments with [³⁵S]-methionine also showed this sharp increase of Td f in the dark-light transition. From the pattern of decay of [³⁵S]-labelled Td f, a half-life of 7 h was determined for this chloroplast protein. In vitro translation experiments with poly(A)-mRNA isolated from illuminated young spinach seedlings, coupled to a wheat-germ synthesizing system, showed the appearance of a labelled fraction of ca 19 kDa molecular mass, recognizable by a specific Td f antiserum. When intact spinach chloroplasts were added to the translation assay medium, and then illuminated, the 19 kDa band disappeared, with a parallel increase of an internalized 13 kDa labelled polypeptide, also recognized by the Td f antiserum. These results are good evidence for a nuclear-coded synthesis of a Td f precursor, which travels through the chloroplast envelope, leaving the functional protein inside the organelle after the loss of a 6 kDa transit peptide.     

The phylogenetic status of arthropods, as inferred from 18S rRNA sequences

Partial 18S rRNA sequences of five chelicerate arthropods plus a crustacean, myriapod, insect, chordate, echinoderm, annelid, and platyhelminth were compared. The sequence data were used to infer phylogeny by using a maximum-parsimony method, an evolutionary-distance method, and the evolutionary-parsimony method. The phylogenetic inferences generated by maximum-parsimony and distance methods support both monophyly of the Arthropoda and monophyly of the Chelicerata within the Arthropoda. These results are congruent with phylogenies based on rigorous cladistic analyses of morphological characters. Results support the inclusion of the Arthropoda within a spiralian or protostome coelomate clade that is the sister group of a deuterostome clade, refuting the hypothesis that the arthropods represent the "primitive" sister group of a protostome coelomate clade. Bootstrap analyses and consideration of all trees within 1% of the length of the most parsimonious tree suggest that relationships between the nonchelicerate arthropods and relationships within the chelicerate clade cannot be reliably inferred with the partial 18S rRNA sequence data. With the evolutionary-parsimony method, support for monophyly of the Arthropoda is found in the majority of the combinations analyzed if the coelomates are used as "outgroups." Monophyly of the Chelicerata is supported in most combinations assessed. Our analyses also indicate that the evolutionary-parsimony method, like distance and parsimony, may be biased by taxa with long branches. We suggest that a previous study's inference of the Arthropoda as paraphyletic may be the result of (a) having two few arthropod taxa available for analysis and (b) including long-branched taxa.      

Neutron crystallographic evidence of lipase-colipase complex activation by a micelle.

The concept of lipase interfacial activation stems from the finding that the catalytic activity of most lipases depends on the aggregation state of their substrates. It is thought that activation involves the unmasking and structuring of the enzyme's active site through conformational changes requiring the presence of oil-in-water droplets. Here, we present the neutron structure of the activated lipase-colipase-micelle complex as determined using the D2O/H2O contrast variation low resolution diffraction method. In the ternary complex, the disk-shaped micelle interacts extensively with the concave face of colipase and the distal tip of the C-terminal domain of lipase. Since the micelle- and substrate-binding sites concern different regions of the protein complex, we conclude that lipase activation is not interfacial but occurs in the aqueous phase and is mediated by colipase and a micelle.     

Inertial vestibular coding of motion: concepts and evidence

Central processing of inertial sensory information about head attitude and motion in space is crucial for motor control. Vestibular signals are coded relative to a non-inertial system, the head, that is virtually continuously in motion. Evidence for transformation of vestibular signals from head-fixed sensory coordinates to gravity-centered coordinates have been provided by studies of the vestibulo-ocular reflex. The underlying central processing depends on otolith afferent information that needs to be resolved in terms of head translation related inertial forces and head attitude dependent pull of gravity. Theoretical solutions have been suggested, but experimental evidence is still scarce. It appears, along these lines, that gaze control systems are intimately linked to motor control of head attitude and posture.     

Fine filaments in lymphatic endothelial cells

Several and various types of cells contain fine cytoplasmic filaments closely resembling the myofilaments of muscle cells (2, 18, 23, 24). In many of these cells and especially when cultured, it has been demonstrated that some of these filaments react with heavy meromyosin (HMM) in the same way as do the actin filaments of muscle cells (3, 6 7). This suggests that these filaments may be actinoid and form part of a contractile system. As fine intracytoplasmic filaments do occur in lymphatic endothelial cells (2, 14), we undertook an electron microscope investigation of their fine structure and their reaction on incubation with HMM and EDTA. We postulated that lymphatic endothelial cells possess a contractile filamentous system to which these filaments belong.