A Contribution to the Nematode Fauna of Two Agamid Lizards from Afghanistan.

Information on the recent herpetological and related parasitological collections are very rarely available for Afghanistan. We examined two species of the family Agamidae, Laudakia nuristanica and Paralaudakia caucasia for the presence of the intestinal helminth fauna. Overall, we examined 13 specimens of these lizards and found three species of helminths (Abbreviata achari, Thelandros masaae, T. taylori) in a single specimen of L. nuristanica and four species (A. achari, T. baylisi, T. taylori, P. kasauli) in three specimens of P. caucasia. Here in, we present the first report on the helminth fauna from L. nuristanica, record a new helminth host for P. caucasia and three new country records for the helminth fauna of Afghanistan.

Multilocus species-delimitation in the Xerotyphlops vermicularis (Reptilia: Typhlopidae) species complex.

Scolecophidia (worm snakes) are a vertebrate group with high ecomorphological conservatism due to their burrowing lifestyle. The Eurasian or Greek blindsnake Xerotyphlops vermicularis is their only European representative, a species-complex with an old diversification history. However, its systematics and taxonomy has remained untouched. Here, we extend previous work that relied heavily on mitochondrial markers, following a multi-locus approach and applying several species-delimitation methods, including a Bayesian coalescence-based approach (STACEY). Four "species" delimitation analyses based on the mtDNA (ABGD, bGMYC, mPTP, parsimony networks) returned 14, 11, 9 and 10 clusters, respectively. By mitotyping twice as many specimens as before, we have a complete picture of each cluster's distribution. With the exception of the highly-divergent Levantine lineage, the three independent nuclear markers did not help with phylogenetic resolution, as demonstrated in haplotype networks, concatenated and species-trees, a result of incomplete lineage sorting. The prevailing model from the coalescence-based species-delimitation identified two species: the lineage from the Levant and all others. We formally recognize them as distinct species and resurrect Xerotyphlops syriacus (Jan, 1864) to include the Levantine blindsnakes. Finally, X. vermicularis and X. syriacus may represent species-complexes themselves, since they include high levels of cryptic diversity.

Spatial filters of function and phylogeny determine morphological disparity with latitude.

The drivers of latitudinal differences in the phylogenetic and ecological composition of communities are increasingly studied and understood, but still little is known about the factors underlying morphological differences. High-resolution, three-dimensional morphological data collected using computerized micro-tomography (micro-CT) allows comprehensive comparisons of morphological diversity across latitude. Using marine bivalves as a model system, this study combines 3D shape analysis (based on a new semi-automated procedure for placing landmarks and semilandmarks on shell surfaces) with non-shape traits: centroid size, proportion of shell to soft-tissue volume, and magnitude of shell ornamentation. Analyses conducted on the morphology of 95% of all marine bivalve species from two faunas along the Atlantic coast of North America, the tropical Florida Keys and the boreal Gulf of Maine, show that morphological shifts between these two faunas, and in phylogenetic and ecological subgroups shared between them, occur as changes in total variance with a bounded minimum rather than directional shifts. The dispersion of species in shell-shape morphospace is greater in the Gulf of Maine, which also shows a lower variance in ornamentation and size than the Florida Keys, but the faunas do not differ significantly in the ratio of shell to internal volume. Thus, regional differences conform to hypothesized effects of resource seasonality and predation intensity, but not to carbonate saturation or calcification costs. The overall morphological differences between the regional faunas is largely driven by the loss of ecological functional groups and family-level clades at high latitudes, rather than directional shifts in morphology within the shared groups with latitude. Latitudinal differences in morphology thus represent a complex integration of phylogenetic and ecological factors that are best captured in multivariate analyses across several hierarchical levels.

Common latitudinal gradients in functional richness and functional evenness across marine and terrestrial systems.

Functional diversity is an important aspect of biodiversity, but its relationship to species diversity in time and space is poorly understood. Here we compare spatial patterns of functional and taxonomic diversity across marine and terrestrial systems to identify commonalities in their respective ecological and evolutionary drivers. We placed species-level ecological traits into comparable multi-dimensional frameworks for two model systems, marine bivalves and terrestrial birds, and used global species-occurrence data to examine the distribution of functional diversity with latitude and longitude. In both systems, tropical faunas show high total functional richness (FR) but low functional evenness (FE) (i.e. the tropics contain a highly skewed distribution of species among functional groups). Functional groups that persist toward the poles become more uniform in species richness, such that FR declines and FE rises with latitude in both systems. Temperate assemblages are more functionally even than tropical assemblages subsampled to temperate levels of species richness, suggesting that high species richness in the tropics reflects a high degree of ecological specialization within a few functional groups and/or factors that favour high recent speciation or reduced extinction rates in those groups.

Extinction risk in extant marine species integrating palaeontological and biodistributional data.

Extinction risk assessments of marine invertebrate species remain scarce, which hinders effective management of marine biodiversity in the face of anthropogenic impacts. To help close this information gap, in this paper we provide a metric of relative extinction risk that combines palaeontological data, in the form of extinction rates calculated from the fossil record, with two known correlates of risk in the modern day: geographical range size and realized thermal niche. We test the performance of this metric-Palaeontological Extinction Risk In Lineages (PERIL)-using survivorship analyses of Pliocene bivalve faunas from California and New Zealand, and then use it to identify present-day hotspots of extinction vulnerability for extant shallow-marine Bivalvia. Areas of the ocean where concentrations of bivalve species with higher PERIL scores overlap with high levels of climatic or anthropogenic stressors should be considered of most immediate concern for both conservation and management.

Cutaneous features of pseudoxanthoma elasticum in a patient with generalized arterial calcification of infancy due to a homozygous missense mutation in the ENPP1 gene.

BACKGROUND: Pseudoxanthoma elasticum (PXE) manifests with cutaneous lesions consisting of yellowish papules coalescing into plaques of inelastic skin. Histopathology demonstrates accumulation of pleiomorphic elastic structures with progressive mineralization. The classic form of PXE is caused by mutations in the ABCC6 gene. OBJECTIVES: A 2-year-old patient with PXE of the neck, inguinal folds and lower abdomen, and with extensive tissue mineralization, was evaluated for the underlying mutations in candidate genes known to be involved in ectopic mineralization disorders. METHODS: The patient's genotype was studied by sequencing ABCC6, MGP and ENPP1 genes, encoding proteins which harbour mutations in ectopic mineralization disorders. RESULTS: No pathogenetic mutations were found in the ABCC6 or MGP genes. Sequencing of ENPP1 disclosed a homozygous missense mutation, p.Y513C, associated with generalized arterial calcification of infancy. CONCLUSIONS: This study demonstrates the presence of the cutaneous features of PXE in a genetically distinct disease, generalized arterial calcification of infancy, and thus expands the spectrum of PXE-related disorders.

Feasibility study for a passive trip system to prevent a runaway reaction in a batch reactor.

Reactors for carrying out exothermic reactions are amongst others equipped with trip systems. Normally these are active systems requiring a number of components such as sensors, pumps or valves to function for a successful trip. They may, for example, use the injection of a reaction inhibitor or the dumping of the reactor contents into a knock-out tank. The availability of such systems, i.e. their probability of functioning on demand, largely depends on their degree of redundancy. However, the possibility of common cause failures places a limit on increasing their availability by raising their degree of redundancy. Nevertheless, a trip system may reach a high availability if instead of stepping up its redundancy a passive system is used. The design of such a passive trip system for batch reactors is described and its feasibility is demonstrated by experimental investigations of three different types of reactions.

Lessons from the past: evolutionary impacts of mass extinctions.

Mass extinctions have played many evolutionary roles, involving differential survivorship or selectivity of taxa and traits, the disruption or preservation of evolutionary trends and ecosystem organization, and the promotion of taxonomic and morphological diversifications-often along unexpected trajectories-after the destruction or marginalization of once-dominant clades. The fossil record suggests that survivorship during mass extinctions is not strictly random, but it often fails to coincide with factors promoting survival during times of low extinction intensity. Although of very serious concern, present-day extinctions have not yet achieved the intensities seen in the Big Five mass extinctions of the geologic past, which each removed > or =50% of the subset of relatively abundant marine invertebrate genera. The best comparisons for predictive purposes therefore will involve factors such as differential extinction intensities among regions, clades, and functional groups, rules governing postextinction biotic interchanges and evolutionary dynamics, and analyses of the factors that cause taxa and evolutionary trends to continue unabated, to suffer setbacks but resume along the same trajectory, to survive only to fall into a marginal role or disappear ("dead clade walking"), or to undergo a burst of diversification. These issues need to be addressed in a spatially explicit framework, because the fossil record suggests regional differences in postextinction diversification dynamics and biotic interchanges. Postextinction diversifications lag far behind the initial taxonomic and morphological impoverishment and homogenization; they do not simply reoccupy vacated adaptive peaks, but explore opportunities as opened and constrained by intrinsic biotic factors and the ecological and evolutionary context of the radiation.

Effects of sampling standardization on estimates of Phanerozoic marine diversification.

Global diversity curves reflect more than just the number of taxa that have existed through time: they also mirror variation in the nature of the fossil record and the way the record is reported. These sampling effects are best quantified by assembling and analyzing large numbers of locality-specific biotic inventories. Here, we introduce a new database of this kind for the Phanerozoic fossil record of marine invertebrates. We apply four substantially distinct analytical methods that estimate taxonomic diversity by quantifying and correcting for variation through time in the number and nature of inventories. Variation introduced by the use of two dramatically different counting protocols also is explored. We present sampling-standardized diversity estimates for two long intervals that sum to 300 Myr (Middle Ordovician-Carboniferous; Late Jurassic-Paleogene). Our new curves differ considerably from traditional, synoptic curves. For example, some of them imply unexpectedly low late Cretaceous and early Tertiary diversity levels. However, such factors as the current emphasis in the database on North America and Europe still obscure our view of the global history of marine biodiversity. These limitations will be addressed as the database and methods are refined.

Invariant size-frequency distributions along a latitudinal gradient in marine bivalves.

In the most extensive analysis of body size in marine invertebrates to date, we show that the size-frequency distributions of northeastern Pacific bivalves at the provincial level are surprisingly invariant in modal and median size as well as size range, despite a 4-fold change in species richness from the tropics to the Arctic. The modal sizes and shapes of these size-frequency distributions are consistent with the predictions of an energetic model previously applied to terrestrial mammals and birds. However, analyses of the Miocene-Recent history of body sizes within 82 molluscan genera show little support for the expectation that the modal size is an evolutionary attractor over geological time.

Dissecting latitudinal diversity gradients: functional groups and clades of marine bivalves.

The latitudinal diversity gradient, with maximum taxonomic richness in the tropics, is widely accepted as being pervasive on land, but the existence of this pattern in the sea has been surprisingly controversial. This is partly due to Thorson's influential claim that the normal latitudinal diversity gradient occurs in marine epifauna (taxa living on the surface of the substratum) but not in infauna (burrowing or boring into the substratum), a contrast he attributed to the greater spatial and temporal environmental homogeneity of infaunal habitats. In an analysis of 930 species of north-eastern Pacific marine shelf bivalves, we found that bivalves as a whole, and both infauna and epifauna separately, show a strong latitudinal diversity gradient (measured as number of species per degree latitude) that is closely related to mean sea surface temperature (SST), even in analyses of residuals and first differences. This agrees with results for marine gastropods, but contradicts Thorson's environmental homogeneity hypothesis. The relationship between SST and diversity is consistent with a species-energy hypothesis, but the linkages from SST to diversity remain unclear. Most bivalve clades within broad functional groups conform to the general latitudinal trend, except for the deposit-feeding protobranchs. This group's non-directional pattern may be related to its mode of development, because a similar effect is seen in several other groups locked into this low-fecundity, non-feeding larval mode.

The future of the fossil record.

The fossil record provides a powerful basis for analyzing the controlling factors and impact of biological evolution over a wide range of temporal and spatial scales and in the context of an evolving Earth. An increasingly interdisciplinary paleontology has begun to formulate the next generation of questions, drawing on a wealth of new data, and on methodological advances ranging from high-resolution geochronology to simulation of morphological evolution. Key issues related to evolutionary biology include the biotic and physical factors that govern biodiversity dynamics, the developmental and ecological basis for the nonrandom introduction of evolutionary innovations in time and space, rules of biotic response to environmental perturbations, and the dynamic feedbacks between life and the Earth's surface processes. The sensitivity of evolutionary processes to rates, magnitudes, and spatial scales of change in the physical and biotic environment will be important in all these areas.

Fossils, molecules and embryos: new perspectives on the Cambrian explosion.

The Cambrian explosion is named for the geologically sudden appearance of numerous metazoan body plans (many of living phyla) between about 530 and 520 million years ago, only 1.7% of the duration of the fossil record of animals. Earlier indications of metazoans are found in the Neoproterozic; minute trails suggesting bilaterian activity date from about 600 million years ago. Larger and more elaborate fossil burrows appear near 543 million years ago, the beginning of the Cambrian Period. Evidence of metazoan activity in both trace and body fossils then increased during the 13 million years leading to the explosion. All living phyla may have originated by the end of the explosion. Molecular divergences among lineages leading to phyla record speciation events that have been earlier than the origins of the new body plans, which can arise many tens of millions of years after an initial branching. Various attempts to date those branchings by using molecular clocks have disagreed widely. While the timing of the evolution of the developmental systems of living metazoan body plans is still uncertain, the distribution of Hox and other developmental control genes among metazoans indicates that an extensive patterning system was in place prior to the Cambrian. However, it is likely that much genomic repatterning occurred during the Early Cambrian, involving both key control genes and regulators within their downstream cascades, as novel body plans evolved.

Marine latitudinal diversity gradients: tests of causal hypotheses.

Latitudinal diversity gradients are first-order expressions of diversity patterns both on land and in the oceans, although the current hypotheses that seek to explain them are based chiefly on terrestrial data. We have assembled a database of the geographic ranges of 3,916 species of marine prosobranch gastropods living on the shelves of the western Atlantic and eastern Pacific Oceans, from the tropics to the Arctic Ocean. Western Atlantic and eastern Pacific diversities are similar, and the diversity gradients are strikingly similar despite many important physical and historical differences between the oceans. This shared diversity pattern cannot be explained by: (i) latitudinal differences in species range-length (Rapoport's rule); (ii) species-area effects; or (iii) recent geologic histories. One parameter that does correlate significantly with diversity in both oceans is solar energy input, as represented by average sea surface temperature. If this correlation is causal, sea surface temperature is probably linked to diversity through some aspect of productivity. In this case, diversity is an evolutionary outcome of trophodynamic processes inherent in ecosystems, and not just a byproduct of physical geographies.

Geographic variation in the molluscan recovery from the end-cretaceous extinction

Biotic recovery patterns after the end-Cretaceous mass extinction differ among the molluscan faunas of the North American Gulf Coast, northern Europe, northern Africa, and Pakistan and northern India. In contrast to the Gulf Coast, the other three regions lack a rapid expansion and decline of "bloom taxa" and have lower proportions of invaders early in the recovery phase. The anomalous Gulf Coast patterns, distinct from extratropical Europe and the tropical regions, provide evidence for the biogeographic and macroevolutionary complexity of biotic recoveries and may have implications for present-day biotas.

Paleobiology, community ecology, and scales of ecological pattern.

The fossil record provides a wealth of data on the role of regional processes and historical events in shaping biological communities over a variety of time scales. The Quaternary record with its evidence of repeated climatic change shows that both terrestrial and marine species shifted independently rather than as cohesive assemblages over scales of thousands of years. Larger scale patterns also show a strong individualistic component to taxon dynamics; assemblage stability, when it occurs, is difficult to separate from shared responses to low rates of environmental change. Nevertheless, the fossil record does suggest that some biotic interactions influence large-scale ecological and evolutionary patterns, albeit in more diffuse and protracted fashions than those generally studied by community ecologists. These include: (1) the resistance by incumbents to the establishment of new or invading taxa, with episodes of explosive diversification often appearing contingent on the removal of incumbents at extinction events; (2) steady states of within-habitat and global diversity at longer time scales (10(7)-l0(8) yr), despite enormous turnover of taxa; and (3) morphological and biogeographic responses to increased intensities of predation and substratum disturbance over similarly long time scales. The behavior of species and communities over the array of temporal and spatial scales in the fossil record takes on additional significance for framing conservation strategies, and for understanding recovery of species, lineages, and communities from environmental changes.

Developmental evolution of metazoan bodyplans: the fossil evidence.

Evidence from the fossil record, developmental biology and metazoan phylogeny demonstrates that the rapid origination of major metazoan bodyplans during the late Neoproterozoic and earliest Cambrian was intimately associated with a series of innovations in developmental control mechanisms that included the Hox gene cluster. The interval between about 565 Ma (million years ago) and 530 Ma evidently includes the protostome-deuterostome branching, diversification of independent higher metazoan clades, diversification of important developmental control systems, and formation of higher metazoan bodyplans. Comparative paleontological and developmental studies will allow further tests of alternative models for the sequence of these events, illuminating the association between developmental and bodyplan evolution.

Scales of climatic variability and time averaging in Pleistocene biotas: implications for ecology and evolution.

Biotic responses to Pleistocene climatic fluctuations have traditionally been analyzed in the context of glacial-interglacial cycles on the scale of 10000-100 000 years. However, emerging evidence indicates that short-term, high-amplitude, climatic 'flickers', close to the limits of the resolving power of the fossil record, occurred within the glacial and interglacial substages. Because species shift geographically in response to the climate flickers, community structures are fluid, with changes absorbed ecologically and not mediated macroevolutionarily. The rapidity of these shifts may also explain anomalous fossil assemblages.