Environmental Controls on River Assemblages at the Regional Scale: An Application of the Elements of Metacommunity Structure Framework

Understanding factors that structure regional biodiversity is important for linking ecological and biogeographic processes. Our objective was to explore regional patterns in riverine benthic invertebrate assemblages in relation to their broad positioning along the river network and examine differences in composition, biodiversity (alpha and beta diversity), and environmental drivers. We up-scaled methods used to examine patterns in metacommunity structure (Elements of Metacommunity Structure framework) to examine faunal distribution patterns at the regional extent for 168 low-mountain stream invertebrate assemblages in central Germany. We then identified the most influential environmental factors using boosted regression trees. Faunal composition patterns were compartmentalised (Clementsian or quasi-Clementsian), with little difference from headwaters to large rivers, potentially reflecting the regional scale of the study, by crossing major catchment boundaries and incorporating different species pools. While idealised structures did not vary, environmental drivers of composition varied considerably between river sections and with alpha diversity. Prediction was substantially weaker, and the importance of space was greater, in large rivers compared to other sections suggesting a weakening in species sorting downstream. Further, there was a stronger transition in composition than for alpha diversity downstream. The stronger links with regional faunal composition than with richness further emphasises the importance of considering the alternative ways in which anthropogenic stressors are operating to affect biodiversity patterns. Our approach allowed bridging the gap between local (or metacommunity) and regional scales, providing key insights into drivers of regional biodiversity patterns.     

Investigating the environmental drivers of deep‐seafloor biodiversity: A case study of peracarid crustacean assemblages in the Northwest Atlantic Ocean

The deep‐sea benthos covers over 90% of seafloor area and hosts a great diversity of species which contribute toward essential ecosystem services. Evidence suggests that deep‐seafloor assemblages are structured predominantly by their physical environment, yet knowledge of assemblage/environment relationships is limited. Here, we utilized a very large dataset of Northwest Atlantic Ocean continental slope peracarid crustacean assemblages as a case study to investigate the environmental drivers of deep‐seafloor macrofaunal biodiversity. We investigated biodiversity from a phylogenetic, functional, and taxonomic perspective, and found that a wide variety of environmental drivers, including food availability, physical disturbance (bottom trawling), current speed, sediment characteristics, topographic heterogeneity, and temperature (in order of relative importance), significantly influenced peracarid biodiversity. We also found deep‐water peracarid assemblages to vary seasonally and interannually. Contrary to prevailing theory on the drivers of deep‐seafloor diversity, we found high topographic heterogeneity (at the hundreds to thousands of meter scale) to negatively influence assemblage diversity, while broadscale sediment characteristics (i.e., percent sand content) were found to influence assemblages more than sediment particle‐size diversity. However, our results support other paradigms of deep‐seafloor biodiversity, including that assemblages may vary inter‐ and intra‐annually, and how assemblages respond to changes in current speed. We found that bottom trawling negatively affects the evenness and diversity of deep‐sea soft‐sediment peracarid assemblages, but that predicted changes in ocean temperature as a result of climate change may not strongly influence continental slope biodiversity over human timescales, although it may alter deep‐sea community biomass. Finally, we emphasize the value of analyzing multiple metrics of biodiversity and call for researchers to consider an expanded definition of biodiversity in future investigations of deep‐ocean life.     

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.     

Faunal assembly in chironomids (Diptera): generic association and spread

Faunal assembly in chironomids was analysed using published data in the fauna of three rivers in southern England and of Great Britain as a whole. Two questions, both relating to the generic composition of local faunal assemblages, were asked: (i) to what extent are faunas from different sites within a single geographical area associated in terms of the occurrence of genera ('generic association'); (ü) given the total number of species observed, is the number of different genera represented ('generic spread') more than would be expected by chance. The latter question relates to the hypothesis that if interspecific competition is a strong organizing force of local faunal assemblages, species would be more likely to occur as widely spread out among different genera, thus decreasing overlap in resource use and hence the possibility of outright competition. Null models of species occurrence were constructed through Monte Carlo simulation to evaluate quantitatively these two questions. Generic association of faunal assemblages from three localities was statistically significant, though there was some variation among different subfamilies of Chironomidae. No evidence of generic diversification (more genera occurring in the fauna than expected by chance) was found. These results and the original questions were given critical considerations in the discussion.     

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.     

Late pleistocene paleoclimatology: Planktonic foraminiferal analyses of sediment cores from the central North Atlantic

Planktonic foraminiferal analyses of six deep-sea sediment cores from the central North Atlantic east of the Azores Islands between 37°N and 40°N show distinct oscillations in planktonic foramineferal assemblages during the last 300,000 years. A paleoclimatic curve has been constructed using “Total Fauna Analysis” that reveals three glacial and four interglacial episodes. Relatively minor climatic oscillations are superimposed upon the major glacial-interglacial episodes. The paleoclimatic curve is similar to previous paleoclimatic curves from the Atlantic and adjacent areas. Minor paleoclimatic fluctuations are more distinct in paleoclimatic curves from high latitudes of the Atlantic.The faunal assemblages are transitional between subarctic and subtropical assemblages. During portions of the interglacial episodes, the assemblage is dominated by Globorotalia inflata. Neogloboquadrina pachyderma (dextral-coiling) or Globigerina bulloides dominate during the remainder of the interglacial episodes and during the glacial episodes. Glacial episodes are also marked by particularly high frequencies of Globigerina quinqueloba and Globorotalia scitula. Interglacial episodes are also marked by increases in Globorotalia truncatulinoides, Globigerinoides ruber, and Globigerinella aequilateralis.The planktonic foraminiferal faunal oscillations in the cores are complex and cannot be entirely explained by temperature variation. Other parameters such as salinity, nutrients and biological competitin must influence the faunal oscillations.The faunas suggest no major planktonic foraminiferal faunal boundaries migrated across the area between 37°N and 40°N in the central North Atlantic during the last 300,000 years.     

Comparaisons taphonomiques de sites magdaléniens du Bassin parisien : les faunes de Ville-Saint-Jacques (Seine-et-Marne) et Étiolles (Essonne)

The preservation of faunal remains in the Magdalenian sites of the Paris Basin only occurs for one third of the cases. This taphonomic bias is very likely in relation with the open-air locations where the majority of regional sites have been discovered. Nevertheless, the Magdalenian settlement shows a certain variability across the landscape: lowland sites, hillside sites, rock shelter sites. This paper aims to highlight the potential interactions between such physical context variability and the taphonomical features of Magdalenian faunal preservations. The issues presented here mainly focus on the comparison of the two faunal remains’ assemblages of Étiolles (a lowland site of the Seine valley) and Ville-Saint-Jacques (hill side site closed to the Seine valley). These faunal assemblages have been studied using the same set of qualitative and quantitative criteria in order to facilitate direct comparisons. This paper must be viewed as the first step of a more systematical survey of Magdalenian faunal assemblages in the Paris Basin. Finally, the main goal of this survey aims to point out the respective zooarchaeological potential of such sites, and by the way, to reach their global socioeconomic significations.     

Changing subsistence practices at the Dorset Paleoeskimo site of Phillip's Garden, Newfoundland

A comparison of identified faunal assemblages from the Dorset site of Phillip's Garden indicates that harp seal hunting was the main focus of activity throughout the site's occupation. Despite the highly specialized nature of site use, it appears that reliance on harp seal decreased over time while fish and birds became increasingly important. These changes may reflect longer seasonal occupations at the site in later centuries, and/or a decrease in the local availability of harp seal. The observed shift coincides with the onset of a local climatic warming trend, which might have affected harp seal movements in the area. Dorset subsistence and settlement patterns in Newfoundland are still poorly understood due to a lack of preserved faunal assemblages in the region. The temporal trend illustrated here indicates that we cannot assume that these patterns were static throughout the Dorset occupation of the island.     

Faunal structures among European butterflies: evolutionary implications of bias for geography, endemism and taxonomic affiliation

European butterfly species have been classified, using four multivariate classification techniques, to faunal groups (a collection of species having similar distributions) each group having a unique geography (faunal element). Concordance occurs for 94% of species for at least three of the techniques. The faunal groups are brassed in geography, endemicity and taxonomic affiliation, indicating that they have historical and evolutionary significance. The inference is that a species by belonging to one faunal group, rather than to another, has a higher probability of being an endemic, and if it is not an endemic, then of evolving into one. This probability is influenced by affiliation to higher taxa, such as butterfly families, and thus by phylogenetic constraints. We argue that the fidelity of a species to a faunal element will affect its evolutionary pathway since, by belonging to a faunal element, a species is subject lo the distinctive processes linked to a unique landscape and its environmental conditions. Species have the capacity of switching between faunal groups owing to environmental changes impinging on their geographical ranges and epigenotypes. However, transfer of species across different groups are not of equal likelihood, being greatest between contiguous land elements and least between those restricted to islands. We suggest that conservation biology gives more attention to faunal structures: faunal groups have unique geography, are vulnerable to different macroevolutionary pressures and effectively underpin community assemblages within specific biotopes.     

Nestedness of butterfly assemblages in the Zhoushan Archipelago,China: area effects,life-history traits and conservation implications

The nested subset pattern (nestedness) of faunal assemblages has been a research focus in the fields of island biogeography and conservation biology in recent decades. However, relatively few studies have described nestedness in butterfly assemblages in oceanic archipelago systems. Moreover, previous studies often quantified nestedness using inappropriate nestedness metrics and random fill algorithms with high Type I errors. The aims of this study are to examine the existence of nestedness and underlying causal mechanisms of butterfly assemblages in the Zhoushan Archipelago, China. We used the line-transect method to determine butterfly occupancy and abundance on 42 study islands from July to August 2014. We obtained butterfly life-history traits (wingspan, body weight and minimum area requirement) by field work and island geographical features (area and isolation) from the literature. We used the recently developed metric WNODF to estimate nestedness. Partial Spearman rank correlation was used to evaluate the associations of nestedness and island geographical features as well as butterfly life-history traits related to species extinction risk and colonization ability. The butterfly assemblages were significantly nested. Island area and minimum area requirement of butterflies were significantly correlated with nestedness after controlling for other independent variables. In contrast, the nestedness of butterflies did not appear to result from passive sampling or selective colonization. However, multi-year studies are needed to confirm that target effects are not muddling these results. Our results indicate that selective extinction may be the main driver of nestedness of butterfly assemblages in our study system. From a conservation viewpoint, we should protect both large islands and species with large area requirement to maximize the number of species preserved.     

Ammonite and inoceramid radiations after the Santonian-Campanian bioevent in Sakhalin, Far East Russia

Study of several marine Santonian-Campanian successions from Sakhalin Island, Far East Russia, has revealed that evolution of the ammonites and inoceramid bivalves proceeded at different rates after the major faunal turnover at the (locally defined) Santonian-Campanian boundary. Sometimes changes in the inoceramid assemblages were more frequent and rapid than changes in the ammonite assemblages, and sometimes vice versa. Significant levels of inoceramid turnover and radiation events have been identified at the (locally defined) Santonian-Campanian and lower-upper Campanian boundaries. Changes in ammonite and inoceramid diversity, and in the proportions of endemic and cosmopolitan species, were investigated in the context of the local relative sea-level curve and inferred environmental changes. In Far East Russia, the main ammonite and inoceramid radiation after the local Santonian-Campanian faunal turnover occurred in the early Late Campanian Pachydiscus (P.) aff. egertoni ammonite Zone and the coeval Schmidticeramus schmidti inoceramid Zone. This condensed interval of ammonite and inoceramid maximum diversity provides a perfect stratigraphic marker that is recognizable in Sakhalin, North-East Russia and Japan. The succession of Santonian-Campanian assemblages identified in Sakhalin enabled the establishment of seven ammonite and six inoceramid zones, which correlate relatively well with those of North-East Russia and Japan. The problems of placing the Santonian-Campanian boundary in Sakhalin and in the adjacent Japanese island of Hokkaido are reviewed.     

Taphonomic analysis of the Middle Stone Age faunal assemblage from Pinnacle Point Cave 13B, Western Cape, South Africa

A detailed taphonomic analysis is provided for the mammalian and tortoise faunal assemblages from Pinnacle Point Cave 13B (PP13B). It is the first of several reports on the fauna from this site, and must necessarily precede analyses focused on higher level interpretations of Middle Stone Age (MSA) butchery, transport, and hunting behavior. The taphonomic work shows that the faunal assemblage is well preserved and there are discernable differences in the taphonomic pathways to which the fauna was subjected at PP13B between the Middle and Late Pleistocene, between the front and back of the cave, and between body size classes. The largest mammals (size classes 2-5, body weight >24?kg) were mainly accumulated by MSA hominins. Size class 1 ungulates also exhibit a degree of hominin modification consistent with some hominin accumulation of fresh carcasses, but this is more variable through time and includes an observable degree of independent carnivore contribution. Basic taxonomic comparisons reveal a low representation of small mammals, tortoises, and marine mammals at PP13B relative to larger (>4.5?kg) terrestrial mammals. This is a different pattern from other MSA sites along the southwestern coast of South Africa, where small mammals and tortoises are abundant. A microscopic study of the bone surfaces confirms that MSA hominins exploited these small faunal components opportunistically, while focusing most heavily on large terrestrial ungulates. All faunal components show evidence of carnivore scavenging of hominin food debris and a high degree of density mediated destruction. Raptors are at no point implicated as major accumulators of any fauna. The study demonstrates that the full spectrum of MSA faunal exploitation can only be understood when the large mammal, small mammal, and tortoise components of fossil assemblages have all been subjected to comprehensive taphonomic analyses.     

Cenozoic radiolarian paleobiogeography: Implications concerning plate tectonics and climatic cycles

A preliminary study of the paleobiogeographic patterns of radiolarian facies during the Paleogene and subsequent time shows that:(1) Through time radiolarian assemblages display distinct faunal provincialism reminiscent of modern faunal distributions correlated with planetary temperature gradients and surface oceanic conditions. The equatorial—tropical radiolarian fauna extended apparently unrestricted across the Pacific Ocean, the Caribbean Sea and the Atlantic Ocean through Early Miocene time. In the Caribbean Sea and the Atlantic Ocean, radiolarians reached their maximum abundance in the Eocene and Oligocene. Subsequently, they gradually declined to virtual disappearance in these areas in the early Miocene. Their Pacific counterparts remained practically undisturbed, except that post early Miocene assemblages there showed a marked trend toward decreasing test thickness. This trend has since been a worldwide characteristic of Neogene radiolarian assemblages and their modern equivalents. It is postulated that the disappearance of radiolarians in the Carribean Sea and the Atlantic Ocean at the end of the Paleogene is related to the onset of the emergence of the isthmus of Panama which interrupted the preexisting oceanic circulation between the Pacific and Atlantic Oceans.(2) Throughout the Paleogene there have been marked sequential fluctuations in the radiolarian assemblages of the Caribbean Sea which indicate intermittent incursions of higher-latitude fauna in this area. Associated with the faunal fluctuations are cyclic variations in the total carbonate of the sediment with patterns also comparable in duration to Pleistocene carbonate cycles in the equatorial Pacific known to have been induced by climatic changes. Based on similarities with Pleistocene climatic cycles in the equatorial Pacific and elsewhere, it is surmised that the faunal and lithologic fluctuations observed in Paleogene radiolarian sediments were also induced by the biologic and physico-chemical processes associated with worldwide changes in the climatic conditions of that time.     

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.     

河南灵井许昌人遗址普通马(Equus caballus)化石居群的死亡年龄曲线

普通马(Equus caballus)是河南灵井许昌人遗址动物群中的一个优势属种。本文基于这一动物属种牙齿材料的测量与分析, 初步完成了普通马个体死亡年龄的计算及其化石居群的生命表构建, 并与世界范围内多个动物群的相关材料进行了对比研究。该动物群普通马化石材料的死亡年龄曲线反映了这一时期古人类以普通马居群中的壮年个体为主要狩猎目标的选择性生存策略和狩猎能力。     

Low‐head dams induce biotic homogenization/differentiation of fish assemblages in subtropical streams

Extensive distribution of widespread species and the loss of native species driven by anthropogenic disturbances modify community similarity, resulting in a decrease or increase in community distinctiveness. Data from four basins in the Wannan Mountains, China, were used to evaluate the effects of low‐head dams on patterns of fish faunal homogenization and differentiation based on abundance data. We aimed to examine the spatial changes in taxonomic and functional similarities of fish assemblages driven by low‐head dams and to examine whether the changes in the similarity of fish assemblages differed between taxonomic and functional components. We found that low‐head dams significantly decreased the mean taxonomic similarity but increased the mean functional similarity of fish assemblages in impoundments using abundance‐based approaches, suggesting that taxonomic differentiation accompanied functional homogenization in stream fish assemblages. These results show the importance of population abundance in structuring fish faunal homogenization and differentiation at small scales, especially when the major differences among assemblages are in species abundance ranks rather than species identities. Additionally, we also found only a weak positive correlation between changes in mean taxonomic and functional similarities, and partial pairs exhibited considerable variation in patterns of fish faunal homogenization and differentiation for taxonomic and functional components. In conclusion, this study highlighted that the observed taxonomic differentiation of current fish assemblages (short‐term phenomenon) is probably an early warning sign of further homogenization in regions where native species are completely predominated and that changes in taxonomic similarity cannot be used to predict changes in functional similarity.     

Influence of the Late Ordovician glaciation on basin configuration of the Yangtze Platform in China

The Late Ordovician paleogeographic changes in the Yangtze Platform indicate a widespread regression and consequent subaerial exposure probably caused by the 'locking up' of substantial amounts of marine waters during the Late Ordovician glaciation. The subsequent rapid paleogeographic changes on the Yangtze Platform during the earliest Silurian suggest a rapid melting of the ice. The relatively cool waters in the partially closed Yangtze basin during the latest Ordovician were replaced by open and warm waters during the earliest Silurian. Sedimentation rates and composition of faunal assemblages underwent marked changes during latest Ordovician and Early Silurian. Glaciation, Ordovician, Silurian, Paleogeography, sedimentary rate, faunal change.     

UK intertidal foraminiferal distributions: implications for sea-level studies

Foraminiferal assemblages have been collected from ten intertidal study areas situated on the east, south and west coasts of the UK. The assemblages display a vertical zonation which indicates that the distribution of foraminifera in these intertidal environments is usually the direct function of altitude with the duration and frequency of intertidal exposure the most important factors. Multivariate analyses separate foraminiferal assemblages into two faunal zones: a high- and middle marsh zone consisting of differing abundances of Jadammina macrescens, Trochammina inflata and Miliammina fusca; and a low-marsh and tidal flat zone dominated by calcareous foraminiferal species, notably Elphidium williamsoni, Haynesina germanica and Quinqueloculina spp. These faunal zones are similar to those in other mid-latitude, cool temperate intertidal environments although there are spatial and temporal variations between areas. The altitudinal ranges of the faunal zones are employed to identify the vertical relationship of the local environment in which the assemblage accumulated to a reference tide level.     

Do faunal assemblages reflect the exchange intensity in groundwater zones?

The exchange of water with groundwater is a key determinant of water quality and faunal assemblage. Water exchange not only occurs with running waters, but also through percolation, interception (soil, porous alluvium), and evaporation. The aim of this study was to identify how different types of exchange were related to the groundwater faunal assemblage of an alluvial aquifer. Hydrological exchange is largely governed by pore space and thus ultimately by geological formation. In the Marbling Brook catchment of Western Australia the different geological formations did not eventuate in hydrochemically distinct groundwater zones. The cluster analysis of faunal assemblages revealed five groups within the faunal samples which did not reflect spatial patterns such as geological, chemical or topographic features. Discriminant analysis showed that these five groups were best characterized by a range of abiotic features including dissolved oxygen, land-use, and temperature. These variables signal different types and intensities of exchange with the surface. Handling editor: K. Martens     

Macrozoobenthic Assemblages of the Evros Delta (North Aegean Sea)

The composition of the macrozoobenthic assemblages of the Evros Delta (North Aegean Sea) has been investigated by means of 4 replicate quantitative samples, collected at 35 sites. The information obtained from the numerical analysis of the faunal samples and the analysis of other data (values of the main physico-chemical parameters) revealed the presence of a single community. The faunal composition of this community varies locally according mainly to the salinity and secondly to the particle size of the substrate. The community is described on the basis of its biological parameters and compared with corresponding assemblages from other areas.