Decay of similarity of gamasid mite assemblages parasitic on Palaearctic small mammals: geographic distance, host-species composition or environment

Aim The similarity between parasite assemblages should decrease with increasing geographic distance between them, increasing dissimilarity in environmental conditions, and/or increasing dissimilarity of the local host fauna, depending on the dispersal abilities of the parasites and the intimacy of their associations with the host. We tested for a decay in the similarity of gamasid mite assemblages parasitic on small mammals with increasing geographic, ‘environmental’ and ‘host faunal’ (= ‘host’) distances. Location We used data on assemblages of haematophagous gamasid mites (superfamily Dermanyssoidea) parasitic on small mammals (Insectivora, Lagomorpha and Rodentia) from 26 different regions of the northern Palaearctic. Methods Similarity in mite assemblages was investigated at the compound community level across all regions, and at the component community level, across populations of the same host species for each of 11 common host species. Similarity between pairs of mite communities was estimated using both the Jaccard and the Sorensen indices. Environmental distance was estimated as the dissimilarity between locations in a composite measure of climatic variables, and host faunal distance was simply taken as the reciprocal of indices of similarity between the composition of host faunas in different locations. Generalized Linear Models (GLM) and Akaike's Information Criterion were used to select the best model of decay in similarity as a function of geographic, ‘environmental’ and ‘host faunal’ distances. Results Overall, despite slight differences among host species, the similarity in mite assemblages decreased with both increasing ‘environmental’ distance and increasing ‘host faunal’ distance, but was generally unaffected by geographic distance between regions. The similarity of component communities of gamasid mites among host populations was determined mainly by similarity in the physical environment, whereas that of compound communities varied mainly with host‐species composition. Main conclusions Our results indicate that the general decay in community similarity with increasing geographic distances does not apply to assemblages of gamasid mites; it is possible that they can overcome great distances by means of passive dispersal (either by phoresy or wind‐borne), or more likely they occur wherever their hosts are found as a result of tight cospeciation in the past. Mite assemblages on small mammalian hosts seem to be affected mainly by local environmental conditions, and, to a much lesser extent, by the species composition of local host communities.     

Species assemblages as descriptors of mesohabitats

Eight mesohabitats, visually distinct units of habitat withinthestream, were sampled seasonally in a lowland chalkstreamreach. Theaim of the study was to test if mesohabitats defined asstructuralunits were inhabited by particular species assemblages and howthese varied with season. Classification (Bray-Curtisdissimilarityindex and UPGMA) and ordination analyses (DCA) of thedistributionof 258 species in 230 samples, were first used to check theagreement between the subjectively-selected mesohabitat andtheirassociated faunal assemblages. There was a goodcorrespondence, andmesohabitat samples were grouped into 5 major groups (Ranunculusin spring, silt, sand, gravel and macrophytes)whichwere further sub-divided to give a total of 11 groups whenseasonaldifferences were considered. Spearman rank correlation betweenthespatial distribution of mesohabitat groups with environmentalvariables revealed that water velocity and flow dynamicstogetherwith the nature of the substratum, influenced the distributionofthe benthic communities. To evaluate qualitative andquantitativedifferences in taxa composition among mesohabitats,informationstatistics tests and analyses of variance were used incombinationwith the Tukey honestly significant difference test. The 11groupswere characterised by abundance and frequency indicatorspecies.Inverse analysis of dominant species of the community showed agoodequivalence with mesohabitat groups and their indicatorspeciesobtained by direct analysis. The resulting species assemblagesrepresent faunal adaptation to the particular mesohabitats inrelation to natural environmental fluctuations. Themesohabitatscale provides a convenient structural ecological unit toexaminethe functional dynamics of faunal communities inrivers.     

The spread of grass-dominated habitats in Turkey and surrounding areas during the Cenozoic: Phytolith evidence

The arrival of hipparionine horses in the eastern Mediterranean region around 11 Ma was traditionally thought to mark the simultaneous westward expansion of savanna vegetation across Eurasia. However, recent paleoecological reconstructions based on tooth wear, carbon isotopes, and functional morphology indicate that grasses played a minor role in Late Miocene ecosystems of the eastern Mediterranean, which were more likely dry woodlands or forests. The scarcity of grass macrofossils and pollen in Miocene floras of Europe and Asia Minor has been used to support this interpretation. Based on the combined evidence, it has therefore been suggested that Late Miocene ungulate faunal change in the eastern Mediterranean signals increased aridity and landscape openness, but not necessarily the development of grass-dominated habitats.

To shed new light on the Miocene evolution of eastern Mediterranean ecosystems, we used phytolith assemblages preserved in direct association with faunas as a proxy for paleovegetation structure (grassland vs. forest). We extracted phytoliths and other biogenic silica from sediment samples from well-known Early to Late Miocene ( 20–7 Ma) faunal localities in Greece, Turkey, and Iran. In addition, a Middle Eocene sample from Turkey yielded phytoliths and served as a baseline comparison for vegetation inference.

Phytolith analysis showed that the Middle Eocene assemblage consists of abundant grass phytoliths (grass silica short cells) interpreted as deriving from bambusoid grasses, as well as diverse forest indicator phytoliths from dicotyledonous angiosperms and palms, pointing to the presence of a woodland or forest with abundant bamboos. In contrast, the Miocene assemblages are dominated by diverse silica short cells typical of pooid open-habitat grasses. Forest indicator phytoliths are also present, but are rare in the Late Miocene (9–7 Ma) assemblages. Our analysis of the Miocene grass community composition is consistent with evidence from stable carbon isotopes from paleosols and ungulate tooth enamel, showing that C₄ grasses were rare in the Mediterranean throughout the Miocene. These data indicate that relatively open habitats had become common in Turkey and surrounding areas by at least the Early Miocene ( 20 Ma), > 7 million years before hipparionine horses reached Europe and arid conditions ensued, as judged by faunal data.     

Benthische Foraminiferen auf dem Island-Schottland Rücken: Umwelt-Anzeiger an der Grenze zweier ozeanischer Räume

Surface sediment samples taken by box corer from 32 stations on the Iceland-Scotland Ridge have been investigated for their benthic foraminiferal content. The live (Rose Bengal stained) benthic foraminiferal fauna was differentiated from empty tests comprising the foraminiferal death assemblage. Principal component analysis of both the live and dead faunal data from the Iceland-Scotland Ridge reveals eight live species assemblages and six corresponding dead assemblages. Bottom water current conditions, surface sediment characteristics, particulate organic matter supply, and to some extent also the bottom water temperatures are the main factors limiting and governing the composition and distribution of live benthic foraminiferal species assemblages on the Iceland-Scotland Ridge. On the Atlantic slope of the Iceland-Scotland Ridge the dead species assemblages differ greatly from the foraminiferal fauna living there today due to winnowing processes and redeposition of Pleistocene sediments. In this area an investigation of distribution patterns of the empty tests only would lead to wrong results concerning ecologic interrelations between benthic foraminiferal species assemblages and their environment.     

The ecology of two intermittent streams in Victoria, Australia

1. We compared aquatic macroinvertebrate assemblage composition within and between habitats (pools and riffles) at four sites on two intermittent streams in Victoria, Australia during a drought year followed by a wetter year to see how different spatial and temporal scales influenced patterns of community structure detected by multivariate techniques of ordination and classification. We also examined the fit between faunal groups and ‘flow phases’ characterized by multivariate analyses of physicochemical variables in an earlier paper. 2. Pools contained more taxa and individuals than riffles. At the more temporary site, there was considerable overlap between the faunal composition of pools and riffles, whereas habitat-specific assemblages consistently occurred at the more permanent sites. Most taxa were either tolerant, permanent stream forms able to persist in streams that dry briefly, or facultative species that occur in lotic or lentic habitats. Few species appeared specifically adapted to temporary waters. 3. Within habitats, there were some matches between faunal groups and flow phases, especially with the onset of the ‘diminishing flow’ phase, characterized by rising water temperature and conductivity, and declining pH and dissolved oxygen. However, disjunctions among faunal groups were less marked than those between flow phases, and were absent at an intermediate scale when habitats were pooled within sites. At the broadest scale of analysis (within habitats between sites and years), historical events (e.g. whether pools upstream dried completely during the previous summer) apparently influenced community composition as much as site-specific abiotic differences.     

Patchiness of local species richness and its implication for large-scale diversity patterns: an example from the middle Miocene of the Paratethys

The best hope for understanding global diversity patterns is to compare local assemblages, which are mostly preserved in taphonomically-complex shell beds. The present study investigates the variability in faunal composition and diversity at the scale of a single outcrop. A total of 152 species (3315 shells) occurred in 25 samples from 5 tempestitic shell beds. Although sampling intensity was high, total species richness was not captured by far at the hierarchical levels present (outcrop, shell beds, samples) because the majority of species is rare. In contrast, sampling intensity was sufficient to cover the most abundant species, as indicated by stable evenness values. Four taxa dominate the assemblage, but their rank order differs strongly between individual shell beds and individual samples; significant differences between some shell beds are evident for faunal composition, and one shell bed differs from all others with respect to species accumulation curves. Within shell beds, rarefaction curves are generally characterized by strongly overlapping confidence intervals, but outliers occur in three of five shell beds. Patchiness is additionally indicated by a wide scatter of diversity indices in some shell beds and by a wide scatter of samples of one shell bed in an ordination on faunal composition. Most of the outcrop-scale variability in faunal composition and diversity can be related to differences between shell beds. This suggests that sampling a single shell bed of the outcrop is insufficient to characterize the local fauna and its diversity, even when sampling intensity (i.e. the number of samples and shells) within the shell bed was high. Similarly, a single sample from such a shell bed may not be sufficient to characterize its diversity, even when the number of counted shells was high. It is therefore confirmed that sampling strategy and sampling intensity are crucial to confidently characterize the shelly assemblages at such a small spatial scale and that dispersed sampling effort with many small replicate samples will characterize a local assemblage and its diversity better than a few large samples. Diversity comparisons of individual samples between localities must account for the high variability present at the smaller spatial scale, as observed in our study.     

Asteroids,ophiuroids and holothurians from the southeastern Weddell Sea (Southern Ocean)

Until the early 1980s, the composition and distribution of the asteroid (starfish), ophiuroid (brittle star) and holothurian (sea cucumber) bottom fauna of the southeastern Weddell Sea was virtually unknown. This southernmost part of the Atlantic sector of the Southern Ocean is a typical high-latitude Antarctic region located in the circumpolar permanent pack-ice zone. It became accessible for large-scale scientific surveys only through the availability of modern ice-breaking research vessels, such as the German RV “Polarstern”. Here, we describe a dataset of the faunal composition and abundance of starfish, brittle star and sea cucumber assemblages in this area, based on collections from trawl catches carried out during three “Polarstern” cruises in 1983, 1984 and 1985. The set comprises a total of 4,509 records of abundances of 35 asteroid species (with a total of 2,089 specimens) and 38 ophiuroid species (with a total of 18,484 specimens) from 34 stations, as well as of 66 holothurian species (with a total of 20,918 specimens) from 59 stations including zero-abundances (absences). A synthesizing zoogeographical community analysis confirms the presence of three distinct assemblages of asteroids, ophiuroids, and holothurians with highest species richness on the eastern shelf. Overall, starfishes, brittle stars and sea cucumbers were present at all sites investigated in the study area but composition and abundance of asterozoan (asteroids and ophiuroids together) and holothurian fauna varied considerably. A synthesizing zoogeographical community analysis confirms the presence of three distinct assemblages of asteroids, ophiuroids, and holothurians with highest species richness on the eastern shelf. In the case of asterozoans, water depth and latitude seemed to be the most important drivers of assemblage distribution and composition. One of the holothurian assemblages was part of the rich macrozoobenthic community dominated by a diverse and abundant epifauna, mainly sponges and gorgonians. Another one was mainly composed of vagrant deposit-feeding species inhabiting a predominantly non-colonised substratum. In addition, a mixed holothurian assemblage was identified.     

The Benthic Macrofauna Associated with the Oyster Reefs of the James River Estuary,Virginia, U.S.A.

Productive, natural oyster reefs within the James River estuary, were quantitatively sampled for associated macrofauna for a year. The 192 samples yielded 142 taxa. Mean faunal density on these reefs ranged from 5,757 to 57,857 m⁻². Over 770/0 of the individuals collected belonged to 11 taxa. The number of species and informational diversity (H') decreased up the estuarine gradient. The quality of available shell surface was deemed important in determining density. The spatial heterogeneity provided by the shell surface allowed development of a densely populated, diverse faunal assemblage which differs from soft-bottom assemblages principally in quantitative aspects. The assemblage is not spatially or temporally homogeneous and undergoes significant changes in community structure both seasonally and along the estuarine gradient.     

Functional convergence of fish assemblages in urban streams of Brazil and the United States

The aim of this study was describe functional faunal assemblages occurring in streams with high influence of urbanization in USA and Brazil to answer the question whether similar biological traits of fish assemblages would be found between streams with high influence of urbanization in USA and Brazil. We compiled data on the structure and composition of freshwater fishes in 46 urban streams in the USA and 10 urban streams in Brazil. Data on functional traits was established in accordance with ordinal data on abundance. Cluster analysis was conducted to examine relationships among species composition across all sites sampled and to uncover patterns in functional traits of the fish assemblages by nonmetric multidimensional scaling (NMS). The cluster analysis separated the biogeographic regions in relation to the fish fauna composition. However, the ordination analysis (NMS) did not reveal differences between functional traits in Brazil and USA urban fish assemblages, suggesting functional similarity of very disparate zoogeographic assemblages.     

Effects of Habitat Disturbance can be Subtle Yet Significant: Biodiversity of Hawkmoth-Assemblages (Lepidoptera: Sphingidae) in Southeast-Asia

Sphingid biodiversity was compared in a large number of light-trapping samples on Borneo and elsewhere in the Indo-Australian tropics, using our own quantitative light-trapping samples supplemented by other collectors’ published and unpublished data. No effects of anthropogenic habitat disturbance on the within-habitat diversity (measured as Fisher’s α) were observed, but the faunal composition of assemblages differs significantly under varying degrees of disturbance. Altitude, year of sampling and sampling regime (full night vs. part of the night) were identified as additional parameters that influence the composition of local samples. The frequency of subfamilies in samples varies under different disturbance regimes: Smerinthinae decline along a gradient from primary habitats to heavily disturbed sites, while Macroglossinae show the reverse trend. Connections between the reactions of subfamilies to disturbance and altitude and potential life-history differences between the subfamilies are discussed. Hypothetically, capital breeding Smerinthinae might be commoner and more speciose in stable primary habitats, whereas many income breeding Macroglossinae are probably adapted to thrive in ephemeral, disturbed habitats. Furthermore, we show that estimates from local samples fall short of the total known species richness of Borneo by about 10%.     

Distribution patterns of aquatic oligochaetes inhabiting watercourses in the Northwestern Iberian Peninsula

Distribution patterns of aquatic oligochaete assemblages, inhabiting largely unpolluted watercourses, in the Northwestern Iberian Peninsula, and their relationships with chemical and physiographical characteristics were analyzed by means of multivariate analyses. Qualitative and quantitative samples from 47 stations were obtained seasonally during 1983/84 and 1988/90. The variables included in this study were altitude, order number, distance from the origin, mean width, mean depth, substrate, current velocity, oxygen content, pH, conductivity, alkalinity and concentration of different ions.From a chemical point of view, major changes in the structure of oligochaete assemblages were related to water mineralization. The correlation between faunal distribution and environmental variables showed a great increase when physiographic parameters were included in the analyses. Substrate type and current velocity are the principal variables explaining the community structure.     

Radiolarian-based transfer functions for estimating paleooceanographic conditions in the south Indian Ocean

A quantitative analysis of 37 radiolarian species in 58 deep-sea surface-sediment samples from the subtropical to the polar regions of the Indian Ocean produced four geographically distinct faunal assemblages (transitional, antarctic, subtropical, subantarctic). Geographic distributions of these assemblages coincide with present-day patterns of sea-surface temperature and water masses. The antarctic factor is almost exclusively found south of today's Antarctic Polar Front. Highest concentrations of the transitional factor are recorded at sites positioned between today's Subtropical Convergence and the Polar Front. The subtropical factor is dominant in sites north of today's Subtropical Convergence.Values of these four faunal assemblages in the surface-sediment samples were regressed onto present-day summer and winter temperatures of the surface waters overlying each of the core-top sites. Resulting transfer functions yield temperature estimates which compare favorably with observed (present-day) summer and winter sea-surface temperatures, with low standard errors of estimate (< ± 1.9°C) and no clear geographic pattern in maps of the residuals (difference between observed and estimated sea-surface temperature).     

Bay and shoreface benthic communities in the Lower Cretaceous

Lower Cretaceous marine rocks exposed in New Mexico, southcastcrn Colorado, Oklahoma, and Kansas contain well-preserved faunal assemblages that formed either as in-place, disturbed-neighborhood, or transported assemblages. Five faunal associations characterize lithofacies of the bay-to-shoreface depositional model and possess uniquc structures. The Nucula-Nuculana association represents a speciediverse, infaunal detritus-suspension community occupying the open-bay muddy substrate. The Corbula-Breviarca association was a species-dominant, infaunal suspension feeding community on the lower shoreface. The Texigryphaea-Lopha community formed biostromes on the shoreface. The mid-shoreface supported a species-diverse, infaunol suspension feeding community of Scabrotrigonia and Turritella . The Arenicolites trace fossil association characterizes the upper shoreface-beach habitat.     

Composition and diversity of cyanobacteria-associated and free-living bacterial communities during cyanobacterial blooms

Lakes undergoing cyanobacterial blooms often exhibit differences between free-living (FL) and cyanobacteria-associated (CA) bacterial assemblages, but previous studies have not compared distinct FL and CA communities across multiple lakes. This project investigated whether FL and CA communities differ from each other in consistent ways across lakes. FL and CA communities were collected from three Ohio (USA) lakes on two sampling dates during cyanobacterial blooms. High-throughput sequencing was used to characterize the communities, and comparisons were made of the composition and diversity of FL and CA communities within and across lakes. Diversity estimates did not vary significantly among lakes nor between CA and FL assemblages. The taxonomic composition of CA communities differed significantly from that of FL communities in Buckeye and Harsha Lakes and in Maumee Bay on one of two sampling dates. CA communities from Buckeye and Harsha Lakes were more similar to each other than to their respective FL communities. Community composition in Maumee Bay on August 18 did not differ between FL and CA habitats. As the bloom progressed, the FL community remained similar in composition to samples collected on August 18, while the CA community became significantly dissimilar. This study is the first cross-lake comparisons of CA and FL communities, uncovering the impacts of habitat type, lake, and sampling date in determining community composition.     

Patterns in deep-sea macrobenthos at the continental margin: standing crop,diversity and faunal change on the continental slope off Scotland

Depth-related patterns of macrobenthic community structure and composition have been studied from box-core samples from the Scottish continental slope where deep-sea trawling and oil exploration are becoming increasingly important. There is a strong pattern of declining biomass and faunal abundance with increasing depth, but results also indicate reduced biomass and numbers of macrobenthos in the shallowest samples from just below the shelf edge where there are coarse sediments and a regime of strong bottom currents. There is also reduced species diversity at the shallowest stations, probably caused by hydrodynamic disturbance, but no clear mid-slope peak in species diversity as described from the northwest Atlantic. Taxonomic composition of the macrobenthic community shows most change between about 1000 and 1200 m, expressed as a major dichotomy in multivariate analysis by cluster analysis and ordination. It also shows up as a step-like increase in the rate of accumulation of new macrofaunal species. This corresponds to a change in hydrodynamic regime, from a seabed rich in suspension- and interface-feeding epifauna, to one where biogenic traces from large, burrowing deposit feeders are well developed, and visible epifauna rare in seabed photographs. It also corresponds to the depth zone where earlier study of megafaunal echinoderms in trawl and epibenthic sled samples also shows a clear peak in across-slope rate of change in faunal composition.     

Patterns and drivers of aquatic invertebrate diversity across an arid biome

Managing and restoring faunal diversity across large areas requires an understanding of the roles of connectivity and dispersal in driving community patterns. We sought to determine the influence of connectivity, water regime, water source, geographical location, and dispersal traits on patterns of aquatic invertebrate diversity across a continent‐wide arid biome. We compiled data on freshwater invertebrate assemblages from sites spanning the breadth of arid Australia. Univariate analyses (analysis of variance and rarefaction) revealed that alpha and gamma diversity across sites decreased as latitude increased. Multivariate analyses (ordination and analysis of similarity) revealed that community composition had considerable fidelity to geographic regions. Hydrological connectivity was strongly associated with riverine community composition although water rarely flowed (often less than annually). Hydrologically isolated sites (springs and rockholes) supported communities that were markedly dissimilar to hydrologically connected sites, and to each other. We investigated the influence of dispersal on diversity patterns by examining distance decay relationships for each of four dispersal trait groups (obligate aquatic and passive, weak, and strong aerial dispersers) on the basis of geodesic (shortest path) distances between pairs of sites and Mantel tests. We did not detect clear differences between dispersal traits and distance decay relationships at the continental scale, even for the two groups with the lowest dispersal ability (obligate aquatics and passive dispersers). Our results suggest that the loss of hydrological connectivity from water developments in arid lands (for example, the impoundment of intermittent rivers) is likely to affect macroinvertebrates. However, the exact flow mechanisms underlying such changes remain to be determined.     

The Influence of Dry-season Conditions on the Bottom Dwelling Fauna of an East Australian Sub-tropical Estuary

Spatial patterns in benthic infaunal community structure of Port Curtis estuary (north-eastern Australia) were determined from quantitative grab samples and examined in relation to environmental variables. A total of 149 riverine, estuarine and open coastal stations were sampled during the winter survey, and 5744 individuals from 466 species identified. Filter-feeding organisms (primarily polychaetes, molluscs and crustaceans) dominated the benthos, and accounted for 50% of the total species abundance and 30% of the total species richness. Most taxa were uncommon, and 98% of species individually represented less than 2% of the total abundance. Distributional patterns in total species richness and abundance were highly correlated, and both parameters varied significantly with sediment grain size. Numbers of species and individuals were typically highest in coarse-sand and gravel sediments, and were lowest in fine, well-sorted, sands. Cluster analysis of species abundance data revealed nine community groupings characterised by small species sub-sets with restricted distributions. These groupings were primarily related to sediment grain size, sediment organic carbon content, salinity and depth. Not all variation in community structure was explained by these environmental variables, and it is likely that other unmeasured factors play an important role in determining benthic faunal composition in the estuary.     

Bird community composition in an actively managed savanna reserve, importance of vegetation structure and vegetation composition

The mosaic of trees, shrubs and open grassland in mesic African savannas is highly dynamic and strongly influenced by mammal herbivory and fire. We investigated the bird fauna in four different savanna habitats to help assess the impacts of vegetation change on this component of faunal diversity. Birds were censused, plant species were identified and vegetation structure was measured in four different vegetation types (Acacia nilotica woodland, Acacia nigrescens woodland, broadleaf thicket and open grassland) in the Hluhluwe-Umfolozi Park in northern KwaZulu Natal, South Africa. Multivariate ordination analyses were used to determine the relative importance of vegetation structure and floristic composition in defining bird assemblages. The bird communities of the grasslands, the acacia woodlands, and the broadleaf woodlands were clearly separated on the first axis of the detrended canonical correspondence analysis (DCCA). Canopy cover and foliage height diversity (FHD) were strongly correlated with the first axis of DCCA, possibly reflecting a secondary successional series from grassland to woodland, known as bush encroachment. Floristic composition (based on presence–absence data only) seemed to be less important for bird community composition than vegetation structure. The results indicate that changes in vegetation structure, caused by bush encroachment, could cause concomitant changes in bird community composition.     

Importance of historical factors on species richness and composition of butterfly assemblages (Lepidoptera: Rhopalocera) in a northern Iberian mountain range

ABSTRACT. The butterfly assemblages of three vegetation types (pasture, heathland and rocky outcrop with Genista spp.) and two geographical orientations (a northern slope and a sheltered gorge) were studied along an altitudinal gradient in the Picos de Europa in northern Spain. In order to study the effects or historical climatic changes on current butterfly assemblages, it was examined if changes in richness and faunal composition of assemblages were joined with changes in their biogeographical composition. The three vegetation types showed characteristic butterfly assemblages, but no difference in species richness and biogeographical composition was found. Species richness in the sheltered gorge was higher than in the northern slope. Faunal composition also varied between orientations and there were more widespread and Mediterranean species in the sheltered gorge than in the northern slope. Species richness declined with increasing altitude, though a midaltitudinal peak was observed. There was a faunal segregation between high and low localities. Species richness of widespread and Mediterranean butterflies decreased as altitude increased, whereas the reverse was true for montane species. Moreover, biogeographical elements differed in their climatic tolerances measured as altitudinal ranges. Therefore, changes in richness and composition of butterfly assemblages between both slopes and along the altitudinal gradient were joined in part with variation in their biogeographical composition. These results suggest that current species richness and composition of butterfly assemblages in the Picos de Europa might be the consequence of differential colonization of refuges during the past climatic changes.     

Vertical distribution of macrobenthic infauna from the shallow sublittoral zone of Admiralty Bay,King George Island,Antarctica

A 0.0625 m² mini-box corer (MBC) was used to study the vertical distribution of macrobenthos in the shallow sublittoral zone of Admiralty Bay, during the 2003/2004 summer, near the Brazilian Station Comandante Ferraz, and the Peruvian Station Machu Picchu. Sediment samples were taken from 20, 30 and 60 m, and stratified for particle-size, total organic matter (TOM) and faunal composition analysis. The most abundant taxa were Polychaeta, Oligochaeta, Amphipoda, Cumacea, Bivalvia and Gastropoda. In general, macrofauna were concentrated in the 0–4 cm layer (64% of total organisms). Correlations between sediment characteristics and faunal densities have not completely explained neither the aggregation of organisms at the surface sediment layers nor the differences in faunal composition between locations at 20 m depth. Analysis of parameters such as organic carbon, heavy metals, interstitial water, and species composition should contribute to a better understanding of the diversity patterns found in this study.