Biogeographical patterns of benthic macroinvertebrates in the Southeastern Pacific littoral

Aim To use new collections and taxonomic reviews of the Chilean coastal biota, and studies on biodiversity on a reappraisal of Southeastern Pacific littoral biogeography. Location The temperate coastline of the Southeastern Pacific, extending over 6000 km from northern Peru to the southern tip of Chile. Methods Records of coastal macroinvertebrates were assigned to ten geographic zones along the Chilean coast. The Spearman rank correlation coefficient, ρ, was used to establish the relationship between the total number of species and the number of single records for each zone. Regions and underlying faunal gradient were verified via an unweighted paired group method using arithmetic averages (UPGMA), and ordination non-metric multidimensional scaling (nMDS) analysis based on a disagreement distance matrix of presence/absence data. Abundance down-weighting was preferred to rare species down-weighting, owing to the nature of the records, where a larger number of references for a given taxon did not necessarily indicate a greater abundance or commonness. The dissimilarity matrices between the different zones were used to establish the degree of agreement between the different levels of analysis, using a weighted Spearman rank correlation coefficient ρ_w. Statistical significance was established using a randomization (permutation) test. Main conclusions Analysis of new macroinvertebrate data and taxonomic reviews of the Chilean coastal fauna indicates a Transitional-Temperate Region for the Southeastern Pacific littoral, located between 35°S and 48°S where a gradual mixing and replacement of species negates previous hypotheses on the existence of a marked distributional break at 42°S.     

Geographical patterns in species richness of the benthic polychaetes in the continental shelf of the Gulf of California, Mexican Pacific

The present study is the first attempt to describe meso-scale patterns in the species richness of polychaetes along the Gulf of California, which stretches from about 23°N to 31°N. We examine herein the spatial changes in species distribution and explore the overlapping of species’ ranges towards the centre of the Gulf, to test whether the mid-domain effect (MDE) could explain an expected mid-domain peak in species richness. The faunal composition and the latitudinal range of 244 species of polychaetes recorded along the continental shelf of the Gulf of California were analysed in latitude bands of 1°. The species composition changes around the Gulf’s archipelago (~29°N), and the highest values of species richness are found at the 25° (197 species) and 26° (193 species) of latitude. Although the species richness pattern could be described by a parabolic shape, the regional trend was not strongly consistent with the peak of diversity at 27°N (176–191 species) predicted by the mid-domain effect: the random sorting of species’ ranges within spatial domain does not explain satisfactorily the geographical patterns of diversity. Nevertheless, a partial contribution of MDE to these natural patterns of diversity could be detected, and the increase in species richness towards middle latitudes was basically determined by species with distribution ranges larger than 6°. The low level of significance between the empirical species richness pattern and the mid-domain model prediction for polychaetes in the Gulf does not restrict their use as a model for exploring the randomness of the diversity patterns.     

Biogeographic patterns of metazoan parasites of the bigeye flounder, Hippoglossina macrops, in the southeastern Pacific coast

We examined the metazoan parasite fauna of the bigeye flounder, Hippoglossina macrops, in a latitudinal gradient of the southeastern Pacific (ca. 25 degrees S-33 degrees S) to assess whether their parasites show latitudinal and/or biogeographical patterns, and to determine if these patterns agree well with those observed for free-living organisms. In total, 331 fish from 6 localities were analyzed. Eighteen parasite species, including 5 ecto- and 13 endoparasites, were found in the bigeye flounder. Neoheterobothrium chilensis, Floridosentis sp., and Corynosoma australe were the most prevalent parasite species. Ecto- and endoparasites of H. macrops showed different latitudinal patterns. Only endoparasite species show a distributional pattern concordant with biogeographic areas recognized for free-living organisms; this finding was supported by cluster analyses showing 2 major divisions. The first joined the most northern localities (25 degrees S-26 degrees S), and the second consisted of 2 subgroups: (1) 28 degrees S-30 degrees S, and (2) 31 degrees S-32 degrees S. A multivariate analysis of infracommunities showed significant differences in the parasitic load of H. macrops from different latitudes. The latitudinal differences in the prevalence and abundance of the parasites might be explained by differing oceanographic conditions in water masses. These physical conditions could affect the dispersal ability of the infective stages of ecto-parasites, and produce zoogeographical breaks that could affect the distribution of intermediate hosts (invertebrate and vertebrate prey), subsequently affecting the transmission of endoparasites.     

Biodiversity and functioning of polychaetes in benthic sediments

Polychaetes are well represented in most marine and estuarine environments, both in terms of number of individuals and species, and they typically contribute a significant percentage of the total macrofaunal diversity. They exhibit considerable variations in recruitment in both time and space, which is then often reflected in adult distributions. Whilst families and genera of polychaetes have wide distributions, normally species have discrete distributions. Polychaetes are often classified according to their diverse feeding guilds. They play a major role in the functioning of benthic communities, in terms of recycling and reworking of benthic sediments, bioturbating sediments and in the burial of organic matter. Some species form dense tubiculous colonies which can radically change recruitment patterns of other infaunal organisms. Polychaetes, by their burrowing and feeding activity, may considerably enhance various sedimentary processes. However, much remains to be learnt as to how benthic communities function, and how they may change in function as they are increasingly being impacted especially in coastal waters adjacent to centres of population.     

Biogeographical distribution and ecological ranges of benthic cyanobacteria in East Antarctic lakes

For the first time, the cyanobacterial diversity from microbial mats in lakes of Eastern Antarctica was investigated using microscopic and molecular approaches. The present study assessed the biogeographical distribution of cyanobacteria in Antarctica. Five samples were taken from four lakes spanning a range of different ecological environments in Larsemann Hills, Vestfold Hills and Rauer Islands to evaluate the influence of lake characteristics on the cyanobacterial diversity. Seventeen morphospecies and 28 16S rRNA gene-based operational taxonomic units belonging to the Oscillatoriales, Nostocales and Chroococcales were identified. The internal transcribed spacer was evaluated to complement the 16S rRNA gene data and showed similar but more clear-cut tendencies. The molecular approach suggested that potential Antarctic endemic species, including a previously undiscovered diversity, are more abundant than has been estimated by morphological methods. Moreover, operational taxonomic units, also found outside Antarctica, were more widespread over the continent than potential endemics. The cyanobacterial diversity of the most saline lakes was found to differ from the others, and correlations between the sampling depth and the cyanobacterial communities can also be drawn. Comparison with database sequences illustrated the ubiquity of several cyanobacterial operational taxonomic units and their remarkable range of tolerance to harsh environmental conditions.     

Elevational gradients in ant species richness: area, geometry, and Rapoport's rule

Studying the distributions of plants and animals along environmental gradients can illuminate the factors governing and maintaining species diversity. There are two general predictions of how species richness and elevation are related: either species richness decreases monotonically with increasing elevation or richness peaks at mid-elevations. Several processes might contribute to this pattern. In this paper, I examine patterns in ant species richness along elevational gradients in three states in the western US: Colorado, Nevada, and Utah. I test for the effects of available area and the geometric constraints model on species richness patterns. I also test Rapoport's rescue hypothesis, which relates the extent of species' elevational ranges to patterns in species richness. In each state, species richness peaked at mid-elevations. Area explained more variation in species richness than the geometric constraints model in Colorado and Utah, but not in Nevada. Area and geometric constraints together explained 90%, 99%, and 57% of the variation in species richness in Colorado, Nevada, and Utah, respectively. Even though there were peaks at mid-elevations, I still found a strong Rapoport effect. This work suggests that the influences of area and geometric constraints cannot be overlooked when examining patterns in species richness along environmental gradients.     

Pattern of ant diversity in Korea: An empirical test of Rapoport's altitudinal rule

Two diversity patterns (hump-shaped and monotonic decrease) frequently occur along altitude or latitude gradients. We examined whether patterns of ant species richness along altitudes in South Korea can be described by these patterns and whether ranges of ant species follow Rapoport's altitudinal rule. Ants on 12 high mountains (> 1100 m) throughout South Korea (from 33° N to 38° N) were surveyed using pitfall traps at intervals of 200–300 m altitude. The temperatures at the sampling sites were determined from digital climate maps. Ant species richness decreased monotonically along the altitudinal gradient and increased along the temperature gradient. However, species richness of cold-adapted species (highland species) showed a hump-shaped pattern along altitude and temperature gradients. The altitude and temperature ranges of ant species followed Rapoport's rule. Sampling site temperature ranges were significantly correlated with coldness. Therefore, Rapoport's rule can be explained by high cold-tolerance of species inhabiting high altitudes or latitudes.     

Deep-water polychaetes (Annelida) from the southeastern Gulf of California, Mexico

Polychaetes inhabiting deep-sea soft bottoms from the southeastern Gulf of California were collected during four oceanographic cruises during 2000 and 2001. Sampling of benthic organisms was performed with a benthic sledge to collect epifauna and a Karling dredge for epifauna and infauna, in a depth range from 732 to 2 250 m. A list of the polychaetes that were collected and their distribution are presented here. A total of 73 species (distributed among 33 families) were identified. Moreover, 11 species were identified only to genus level and 20 species only to family level. With the exception of Ancistrosyllis hartmanae and Melinnampharete eoa, all identified species have been previously reported in soft bottoms of the Gulf of California or in adjacent areas. Additional previously unreported information is provided herein regarding depth ranges, geographical distribution, morphology and tubes inhabited by the organisms. The morphology of the ampharetids Amage sp. and Samytha sp. does not coincide with that of other species in these genera reported for the Gulf of California, which suggests that they are probably undescribed species.     

Grazing patterns in Siphonaria gigas (Mollusca,Pulmonata) on the rocky Pacific coast of Panama

The pulmonate limpet Siphonaria gigas is the most abundant molluscan grazer in the mid zone on rocky, wave-exposed shores of the Pacific coast of Panama. Erect macroalgae and sessile invertebrates are rare; crustose algae cover ～90% of the rock. The relative abundance of a common blue-green algal crust (Schizothrix calcicola?) is negatively correlated with Siphonaria's abundance. Large-scale removals of the limpet cause rapid increases in percent cover of Schizothrix and concomitant decreases in other crusts, but no changes in the abundance of erect algae or sessile invertebrates. Removing Siphonaria also (1) increases recruitment of crustose algae and barnacles onto new rock and plexiglass substrata, and (2) decreases the abundance of a calcified form of Schizothrix. Harsh conditions during daytime low tides and foraging by fishes at high tide control the microdistribution of most of this region's mobile and sessile benthic organisms. Wave action and substratum heterogeneity modify these constraints: Siphonaria is rare or absent in sheltered areas, especially on homogeneous surfaces, and is most abundant at wave-exposed sites. However, at extremely wave-beaten sites, Siphonaria and other benthic consumers are rare and ineffective. Crustose algae are reduced in abundance and space is dominated by erect macroalgae and/or barnacles. These normally rare species can outcompete crusts only when thermal or desiccation stress and the effects of benthic consumers and fishes are drastically reduced.     

Early Devonia benthic communities of the Alexander Terrane, southeastern Alaska

Emsian (upper Lower Devonian) limestones exposed on Kasaan, Round, and Wadleigh Islands in southeastern Alaska are part of an allochthonous suitc of island are deposits preserved within the accrctionary Alexander Terrane. Ten benthic marine communities, including several new brachiopod associations, are defined on the basis of field data correlated with a cluster analysis. Biologic and sedimentologic evidence is integrated with community group assignments in order to substantiate the paleoecology and evolutionary history of each community. These faunas were adapted to a spectrum of quiet and rough water habitats, including restricted, shallow subtidal areas nearshore, offshore biostromal banks, and open and restricted portions of a lagoon or shelf. Comparisons with coeval assemblages from the Cordillera and elsewhere reveal that these communities are unique to southeastern Alaska. Their origin within an early Paleozoic island are appears to have led to biogeographic isolation from other parts of the Cordillera and the development of a distinct biota at a site offshorc from the ancient continental margin. ▭ Emsian, paleocommunities, community groups, cluster analysis, Alexander Terrane.     

Biogeographical patterns of bacterial and archaeal communities from distant hypersaline environments

Microorganisms are globally distributed but new evidence shows that the microbial structure of their communities can vary due to geographical location and environmental parameters. In this study, 50 samples including brines and sediments from Europe, Spanish-Atlantic and South America were analysed by applying the operational phylogenetic unit (OPU) approach in order to understand whether microbial community structures in hypersaline environments exhibited biogeographical patterns. The fine-tuned identification of approximately 1000 OPUs (almost equivalent to “species”) using multivariate analysis revealed regionally distinct taxa compositions. This segregation was more diffuse at the genus level and pointed to a phylogenetic and metabolic redundancy at the higher taxa level, where their different species acquired distinct advantages related to the regional physicochemical idiosyncrasies. The presence of previously undescribed groups was also shown in these environments, such as Parcubacteria, or members of Nanohaloarchaeota in anaerobic hypersaline sediments. Finally, an important OPU overlap was observed between anoxic sediments and their overlaying brines, indicating versatile metabolism for the pelagic organisms.     

Climatic Niche Conservatism and Biogeographical Non-Equilibrium in Eschscholzia californica (Papaveraceae), an Invasive Plant in the Chilean Mediterranean Region

Species climate requirements are useful for predicting their geographic distribution. It is often assumed that the niche requirements for invasive plants are conserved during invasion, especially when the invaded regions share similar climate conditions. California and central Chile have a remarkable degree of convergence in their vegetation structure, and a similar Mediterranean climate. Such similarities make these geographic areas an interesting natural experiment for testing climatic niche dynamics and the equilibrium of invasive species in a new environment. We tested to see if the climatic niche of Eschscholzia californica is conserved in the invaded range (central Chile), and we assessed whether the invasion process has reached a biogeographical equilibrium, i.e., occupy all the suitable geographic locations that have suitable conditions under native niche requirements. We compared the climatic niche in the native and invaded ranges as well as the projected potential geographic distribution in the invaded range. In order to compare climatic niches, we conducted a Principal Component Analysis (PCA) and Species Distribution Models (SDMs), to estimate E. californica''s potential geographic distribution. We also used SDMs to predict altitudinal distribution limits in central Chile. Our results indicated that the climatic niche occupied by E. californica in the invaded range is firmly conserved, occupying a subset of the native climatic niche but leaving a substantial fraction of it unfilled. Comparisons of projected SDMs for central Chile indicate a similarity, yet the projection from native range predicted a larger geographic distribution in central Chile compared to the prediction of the model constructed for central Chile. The projected niche occupancy profile from California predicted a higher mean elevation than that projected from central Chile. We concluded that the invasion process of E. californica in central Chile is consistent with climatic niche conservatism but there is potential for further expansion in Chile.     

Biogeographical and anthropogenic determinants of landscape-scale patterns of raptors in West African savannas

Strong raptor population declines have recently been reported in sub-Saharan West Africa, where the pressure on wildlife and their supporting habitats is particularly high. This makes it imperative to understand the role of land-use on landscape-scale patterns of raptors and to define priority areas for conservation. We examine landscape-scale community patterns of raptors in biogeographical zones with different degrees of anthropogenic land-use and assess the role of protected areas in maintaining such patterns. We recorded raptors along road transects in Cameroon’s savannas, covering four years and 7,340–7,700 km in wet and dry seasons, in three biogeographical zones: the relatively well-preserved Inundation and Guinea zones to the north and south of the heavily exploited Sudan zone. The Inundation zone had the largest species pool and Palearctic raptor richness and abundance. The Guinea zone had the largest Afrotropical raptor species pool, while raptor diversity and richness were higher there than in the Sudan zone. The abundance of only one species (Fox Kestrel) peaked in the Sudan zone and only one large-bodied raptor (Hooded Vulture) with a Sudan-centered distribution was more common there than in the other zones. Our results suggest that land-use as determined by protected areas and human exploitation may override the role of biogeographical zonation in shaping raptor assemblages. Comparable patterns of raptor richness and diversity inside and outside protected areas suggest that both protected areas and partly cultivated peripheral zones act as important foraging and source areas, ensuring the preservation of diverse raptor assemblages at the landscape scale. Finally, our data illustrate the comparatively high richness of Cameroon’s and West Africa’s savanna raptor communities on a continental and global scale, underlining their importance for raptor conservation.     

Long-term studies at a benthic station off the coast of Northumberland

Biannual sampling (March and September) has been carried out over the period 1972 to 1985 at a muddy sand station, 55 m depth, with fauna belonging to the deeper offshore edge of Petersen's Amphiura filiformis community.During the period 1974 to 1980 the community exhibited a high degree of persistence stability. This stability was lost between 1980 and 1983, with rising total numbers and biomass and changes in species ranking. There is some evidence of a downward reversal between 1984–85.Evidence suggests that the principal stabilising process is density dependent mortality mediated by competition in a food limited environment. The principal destabilising process appears to be periodic fluctuations in the organic flux to the bottom. A secondary destabilising process is clearly concerned with fluctuating winter temperature. In competitive terms, cold winters favour increased survival in the dominant species at the expense of the lesser ranked species. This process is, however, more ephemeral and subject to adjustment within the time scale of a year.     

台湾维管束植物物种丰富度和种域宽度的海拔格局及对Rapoport法则的检验

物种丰富度和种域(即物种分布范围)沿环境梯度的变化是生物地理学和生物多样性研究的核心问题.岛屿由于受到地理隔离的作用.其物种分布、多样性格局及其成因的特殊性对于发展和检验生物地理学的假说具有重要意义.Rapoport法则提出,生物种域存在着随海拔上升而增大的趋势.台湾地区具有显著的海拔梯度和典型的岛屿环境,其植物区系丰富而独特.我们首次对台湾维管束植物的海拔分布进行研究,包括不同类群植物的物种丰富度和种域的海拔梯度格局,并检验了Rapoport法则的适用性.综合相关信息得到台湾维管束植物区系包含241科1,466属4,751种(含种下单位),对其中具有海拔分布范围信息的3,330种植物进行统计,结果表明:(1)台湾维管束植物科、属、种的丰富度总体上随海拔上升而减小,入侵植物丰富度具有类似格局,而台湾特有植物呈现明显的单峰格局;按照分类群计,蕨类植物和裸子植物为单峰格局,被子植物的3个生态类群均为单调递减格局.(2)物种种域海拔宽度与海拔的关系随不同类群和分析方法而异.其中,入侵植物的种域宽度和中点海拔具有显著的正相关关系,支持Rapoport法则,而全部植物和特有植物不支持;蕨类植物的海拔分布支持Rapopott法则,裸子植物不支持,其他分类群因方法不同而结果之间不一致.我们还比较了台湾和周边大陆和岛屿山地的物种丰富度海拔格局,认为它们物种丰富度海拔梯度模式的不同可能与降水海拔格局的差异有关;而关于Rapoport法则的检验表明,即使在同一山体,不同类群植物分布范围的海拔模式也可能取决于不同的因素和作用机制.     

Spatiotemporal variation in benthic polychaetes (Annelida) and relationships with environmental variables in a tropical estuary

Annelida constitute a dominant functional component in soft-bottom macrobenthic communities and reveal a wide range of adaptability to different marine and coastal habitats. Analyses in different polychaete assemblages and their responses to habitat conditions reflect the biological effects of marine pollution and habitat disturbance. The present study is designed to study colonization and community structure of polychaetes in two ecologically distinct locations of the Sundarban Biosphere Reserve on the northeast coast of India. Polychaete assemblages are characteristically different at the two sites in the extreme northern (Ghusighata) and southern (Gangasagar) portions of the Biosphere Reserve. Levels of heavy metals in polychaete body tissues also reveal interspecific and regional variations. The predominant polychaete fauna exhibited a distinct and unique assemblage of two types: (i) Mastobranchus indicus – Dendronereides heteropoda in the sewage-fed substratum at Ghusighata and (ii) Lumbrinereis notocirrata – Ganganereis sootai – Glycera tesselata at Gangasagar at the mouth of the Hugli estuary where chronic anthropogenic stress and contamination with agricultural and industrial effluents occur. The faunistic composition of polychaetes and their potential for the accumulation of heavy metals from the ambient medium are distinctly different. The study demonstrates that textural composition of the sediments, together with hydrodynamic and geotechnical properties, seem to have the greatest control to quantify the differences of the polychaete community in the two study stations. An in-depth comparative study of polychaete community structure at multiple spatial scales is strongly recommended for future environmental impact assessment in this fragile environment.     

Down under the southeastern Pacific: marine non-indigenous species in Chile

This article presents the first compilation of marine non-indigenous species (NIS) of algae and macro-invertebrates invading Chilean waters. A total of 32 cosmopolitan and non-cosmopolitan species are reported. Among them there are six species considered as extending their southern range of distribution in connection with El Niño events. The article highlights negative and positive impacts caused by marine NIS invasions. Among the first are Codium fragile var. tomentosoide, considered as a pest in Gracilaria chilensis aquaculture facilities in northern Chile, and Ciona intestinalis, a pest in scallop aquaculture installations. Among the second are bio-engineers species, such as the ascidian Pyura praeputialis and the sea grass Heterozostera tasmanica, which have caused an increase in local biodiversity and enhancement of nursery grounds via the creation of new habitats. Further more, invaders such as the algae Mastocarpus papillosus, Porphyra linearis and P. pseudolinearis represent new exploitable resources, extracted by coastal food gatherers along the coast (M. papillosus) or potential species to develop aquaculture. Additional information is presented on the anemone Anemonia alicemartinae, which appears to be a native species (?), having shown in the past 40–50 years, a geographical southward range extension of approximately 1900 km. The number of NIS reported for Chile is compared with those published for the southwestern Atlantic, South Africa, North America (Atlantic and Pacific coasts) and New Zealand. It is suggested that probably the low number of Chilean NIS is due to the fact that the Chilean coasts are environmentally less stressed than other coasts in the world, due to the scarcity of estuaries, gulfs, enclosed bays, lagoons and low human populations. These kinds of sheltered areas have been suggested as centers for bio-invasions, due to the high rate of human-mediated transfer and increase of pollutants. Furthermore, none of NIS reported from Chile show a fast geographical expansion rate (exception of A. alicemartinae), nor invading strategies such as those described for marine NIS in other latitudes, where notorious ecological unbalances following invasions have been observed. An alternative hypothesis is that the low number of marine NIS invading Chile is underestimated, since the modern list of species generated through specific taxonomically intensive port and harbor surveys is still lacking. Fifteen species (five invertebrate and 10 fish) have been deliberately imported to Chile for aquaculture. The invertebrates appear to be controlled within aquaculture facilities and have not established naturalized populations or caused direct ecological impacts on local communities. On the contrary, several millions of salmoniforms (and rainbow trout) have escaped from farming facilities in southern Chile and established naturalized populations. Studies on ecological impacts are lacking. These escapees are also playing a role in the enhancement of artisanal and sport fishery activities.     

Characterization of tidal pool algae in the Mexican Tropical Pacific coast

Tidal pools in the Mexican Tropical Pacific coast have received relatively little attention in spite of their considerable richness in species and wide distribution in the region.This paper presents the first characterization of the algal flora of this region. It analyzes the number and composition of species of the tidal pools of six localities with regard to geographical distribution and its seasonal variations as well as tidal level. 97 species are reported, 25 Chlorophyta, 23 Phaeophyta, 34 Rhodophyta and 15 Cyanophyta.Of that total of species, 63% were found in one locality, 23.7% in two, 11.3% in three and 1 % in 4 or 5 localities. Not one species was common to all of the pools.The highest number of species was found on pools of the middle and low intertidal where the Chlorophyta, Rhodophyta and Phaeophyta were the most abundant algae. Cyanophyta was more common in the supralittoral and high intertidal pools.