How a subsocial intertidal beetle,Bledius spectabilis,prevents flooding and anoxia in its burrow

Summary All stages of Bledius spectabilis Kratz (Staphylinidae) dig wine-bottle shaped burrows in the intertidal Salicornia zone. The adult female lays her eggs around her burrow and, by remaining with them, prevents both flooding by the tide and anoxia. Flooding is prevented by an ever-ready burrow which exploits a surface tension effect and by blocking the burrow once the tide comes in. The burrow has a narrow neck (about 2 mm in diameter) leading to a living chamber 5 mm in diameter. Tides over artificial tubes in agar showed that a critical minimum neck diameter of 2–3 mm prevented sudden flooding, giving time to block the neck with mud. Blocking took about four minutes. Ensuring the burrow is reopened at each low tide is a vital role of the brooding female in anaerobic or impermeable soils. Field models of burrows became anoxic in 4 days, much less than the 4 week long egg stage. A lab model system with anaerobic agar and calculations of oxygen uptake and diffusion supported this conclusion. Mortality of orphaned larvae may be much lower, however, in burrows within large Bledius aggregations because of mitigating good drainage and soil aeration: larval mortality from physical causes in these burrows did not increase over 3 weeks but without the mother, 14% of the eggs were attacked by mould, and two burrows were taken over by a predatory carabid, Dichierotrichus gustavi, and all larvae eaten. The surface tension effects of small air-filled openings may be used by small air-breathing animals in many intertidal habitats. Like Bledius, other intertidal animals, including large ones, may block their burrows at high tide to keep them full of air. Maternal care, in particular the combination of behaviours which protect the brood from the tide and anoxia, enables this airbreathing insect to colonise the inhospitable habitat of the intertidal saltmarsh.     

Temporal and spatial components of variability in benthic recruitment,a 5-year temperate example

Deployment of artificial substrata is a common method of investigating early community development and recruitment, but rarely are such experiments of long enough duration to include even year time scales. We placed replicate, machined-slate panels (15×15 cm) in the intertidal and at depths of 6 and 12 m at two sites of differing flow rate at Lough Hyne, SW Ireland. These were serially replaced every 30–60 days for a period of 5 years (1997–2002), except in the intertidal (2000–2002). The number and identity of all recruits were recorded. Recruitment varied over several orders of magnitude both on temporal and spatial scales. The greatest source of variability was between the intertidal (with few species or recruit numbers) and the subtidal zones (many species, some with thousands of recruits per panel per 30 days). Highest levels of recruitment occurred at the low-flow site (Labhra Cliff). Here, recruitment was dominated by the serpulid polychaete, Pomatoceros sp., reaching ~4000 individuals per panel per 30 days. Highest species richness occurred, however, at the high flow site (Whirlpool Cliff). At this site more colonial forms (e.g. bryozoans) settled. Season was found to be the dominant pattern explaining subtidal recruit and species number variability. Year, however, was the dominant temporal pattern explaining change in diversity (Shannon–Wiener H). In space, depth explained most variability of recruit numbers, whereas site explained more variation in species richness. Both these spatial factors contributed similarly to variability of diversity (H). Recruitment has long been known to vary considerably over large spatial scales, such as with latitude and isolation, but we that show changes of a similar magnitude in recruitment can occur across small spatial scales. Individual taxa showed varied temporal patterns of recruitment including continuous, regular seasonal fluctuations and irregular pulses in particular years.     

Selection of Multiple Umbrella Species for Functional and Taxonomic Diversity to Represent Urban Biodiversity

Surrogates, such as umbrella species, are commonly used to reduce the complexity of quantifying biodiversity for conservation purposes. The presence of umbrella species is often indicative of high taxonomic diversity; however, functional diversity is now recognized as an important metric for biodiversity and thus should be considered when choosing umbrella species. We identified umbrella species associated with high taxonomic and functional biodiversity in urban areas in Switzerland. We analyzed 39,752 individuals of 574 animal species from 96 study plots and 1397 presences of 262 plant species from 58 plots. Thirty‐one biodiversity measures of 7 taxonomic groups (plants, spiders, bees, ground beetles, lady bugs, weevils and birds) were included in within‐ and across‐taxa analyses. Sixteen measures were taxonomical (species richness and species diversity), whereas 15 were functional (species traits including mobility, resource use, and reproduction). We used indicator value analysis to identify umbrella species associated with single or multiple biodiversity measures. Many umbrella species were indicators of high biodiversity within their own taxonomic group (from 33.3% in weevils to 93.8% in birds), to a lesser extent they were indicators across taxa. Principal component analysis revealed that umbrella species for multiple measures of biodiversity represented different aspects of biodiversity, especially with respect to measures of taxonomic and functional diversity. Thus, even umbrella species for multiple measures of biodiversity were complementary in the biodiversity aspects they represented. Thus, the choice of umbrella species based solely on taxonomic diversity is questionable and may not represent biodiversity comprehensively. Our results suggest that, depending on conservation priorities, managers should choose multiple and complementary umbrella species to assess the state of biodiversity. Selección de Múltiples Especies Paraguas para la Diversidad Funcional y Taxonómica para Representar la Biodiversidad Urbana     

Predictability of marine nematode biodiversity

In this paper, we investigated: (1) the predictability of different aspects of biodiversity, (2) the effect of spatial autocorrelation on the predictability and (3) the environmental variables affecting the biodiversity of free-living marine nematodes on the Belgian Continental Shelf. An extensive historical database of free-living marine nematodes was employed to model different aspects of biodiversity: species richness, evenness, and taxonomic diversity. Artificial neural networks (ANNs), often considered as “black boxes”, were applied as a modeling tool. Three methods were used to reveal these “black boxes” and to identify the contributions of each environmental variable to the diversity indices. Since spatial autocorrelation is known to introduce bias in spatial analyses, Moran's I was used to test the spatial dependency of the diversity indices and the residuals of the model. The best predictions were made for evenness. Although species richness was quite accurately predicted as well, the residuals indicated a lack of performance of the model. Pure taxonomic diversity shows high spatial variability and is difficult to model. The biodiversity indices show a strong spatial dependency, opposed to the residuals of the models, indicating that the environmental variables explain the spatial variability of the diversity indices adequately. The most important environmental variables structuring evenness are clay and sand fraction, and the minimum annual total suspended matter. Species richness is also affected by the intensity of sand extraction and the amount of gravel of the sea bed.     

Multiple determinants of community structure in shallow marsh habitats,Cape Fear River estuary,North Carolina,USA

The nekton of tidal creeks was studied at 17 sampling localities from September 1977 through August 1978, in the Cape Fear River estuary, North Carolina, USA. Prior to these dates, collections were made at 9 stations beginning in January 1977; these data were used to supplement conclusions drawn from the larger effort. Species recruited from the ocean utilized marsh habitats only temporarily and dominated the catches with over 70% of the total abundance. Their distribution was influenced by salinity gradients and to a lesser extent by substrate characteristics. In addition, temporal habitat partitioning with associated size differences of related species played an important role in structuring marsh nekton communities. A clearly defined ecotone was associated with the mesohaline-polyhaline transition zone, in slainities between 14 and 21 S. Numerous marine stenohaline forms were restricted to salinities above 16 S, thus increasing species richness in high salinity marshes. Despite differences in freshwater flows in 1977 and 1978, major features of the various marsh communities (species associations and relative abundances) exhibited little change throughout the Cape Fear estuary, indicating that these communities were relatively persistent in time. Standing crops for ocean-spawned species at the end of the growing season indicated that considerable annual export in the form of living biomass of fish and shellfish takes place from the marshes. Since most individuals of these species return to the ocean in the fall, an important energy link between the marshes and nearshore marine environment is demonstrated.     

Spatial mismatch between wild bee diversity hotspots and protected areas

Wild bees are critical for multiple ecosystem functions but are currently threatened. Understanding the determinants of the spatial distribution of wild bee diversity is a major research gap for their conservation. We modeled wild bee α and β taxonomic and functional diversity in Switzerland to uncover countrywide diversity patterns and determine the extent to which they provide complementary information, assess the importance of the different drivers structuring wild bee diversity, identify hotspots of wild bee diversity, and determine the overlap between diversity hotspots and the network of protected areas. We used site-level occurrence and trait data from 547 wild bee species across 3343 plots and calculated community attributes, including taxonomic diversity metrics, community mean trait values, and functional diversity metrics. We modeled their distribution with predictors describing gradients of climate, resource availability (vegetation), and anthropogenic influence (i.e., land-use types and beekeeping intensity). Wild bee diversity changed along gradients of climate and resource availability; high-elevation areas had lower functional and taxonomic α diversity, and xeric areas harbored more diverse bee communities. Functional and taxonomic β diversities diverged from this pattern, with high elevations hosting unique species and trait combinations. The proportion of diversity hotspots included in protected areas depended on the biodiversity facet, but most diversity hotspots occurred in unprotected land. Climate and resource availability gradients drove spatial patterns of wild bee diversity, resulting in lower overall diversity at higher elevations, but simultaneously greater taxonomic and functional uniqueness. This spatial mismatch among distinct biodiversity facets and the degree of overlap with protected areas is a challenge to wild bee conservation, especially in the face of global change, and calls for better integrating unprotected land. The application of spatial predictive models represents a valuable tool to aid the future development of protected areas and achieve wild bee conservation goals.     

Community structure in Florida Escarpment seep and Snake Pit (Mid-Atlantic Ridge) vent mussel beds

Comparisons between invertebrate communities hosted by similar foundation species under different environmental conditions permit identification of patterns of species distributions that might be characteristic of the different ecosystems. Similarities and differences in community structure between two major types of chemosynthetic ecosystems were assessed by analyzing samples of invertebrates associated with Bathymodiolus heckerae Gustafson et al. mussel beds at the Florida Escarpment seep (Gulf of Mexico, 26°01.8N; 84°54.9W; October 2000) and B. puteoserpentis von Cosel et al. mussel beds at the Snake Pit vent (Mid-Atlantic Ridge, 23°22.1N; 44°56.9W; July 2001). Macrofaunal species richness was nearly twice as high in the seep mussel bed compared to the vent mussel bed, and only a single morphospecies, the ophiuroid Ophioctenella acies Tyler et al., was shared between the sites. Similarities between the two faunas at higher taxonomic levels (genus and family) were evident for only a small percentage of the total number of taxa, suggesting that evolutionary histories of many of these seep and vent macrofaunal taxa are not shared. The taxonomic distinctiveness of the seep and vent mussel-bed macrofaunal communities supports the hypothesis that environmental and oceanographic barriers prevent most taxa from occupying both types of habitats. Macrofaunal community heterogeneity among samples was similar in seep and vent mussel beds, indicating that spatial scales of processes regulating community variability may be similar in the two types of ecosystems. Suspension feeders were not represented in the macrofauna of seep or vent mussel beds. Primary consumers (deposit feeders and grazers) contributed more to the total abundance of macrofauna of seep mussel beds than vent mussel beds; secondary consumers (polychaetes and shrimp) were more abundant in the vent mussel beds.Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00227-004-1304-z.Communicated by J.P. Grassle, New Brunswick     

National Red Listing Beyond the 2010 Target

Abstract: Following creation of the 2010 Biodiversity Target under the Convention on Biological Diversity and adoption of the United Nations Millennium Development Goals, information on status and trends of biodiversity at the national level has become increasingly important to both science and policy. National red lists (NRLs) of threatened species may provide suitable data for reporting on progress toward these goals and for informing national conservation priority setting. This information will also become increasingly important for developing species‐ and ecosystem‐based strategies for climate change adaptation. We conducted a thorough global review of NRLs in 109 countries and analyzed gaps in NRL coverage in terms of geography and taxonomy to determine priority regions and taxonomic groups for further investment. We then examined correlations between the NRL data set and gross domestic product (GDP) and vertebrate species richness. The largest geographic gap was in Oceania, followed by middle Africa, the Caribbean, and western Africa, whereas the largest taxonomic gaps were for invertebrates, fungi, and lichens. The comprehensiveness of NRL coverage within a given country was positively correlated with GDP and negatively correlated with total vertebrate richness and threatened vertebrate richness. This supports the assertion that regions with the greatest and most vulnerable biodiversity receive the least conservation attention and indicates that financial resources may be an integral limitation. To improve coverage of NRLs, we propose a combination of projects that target underrepresented taxa or regions and projects that provide the means for countries to create or update NRLs on their own. We recommend improvements in knowledge transfer within and across regions as a priority for future investment.     

Higher Taxa as Surrogates of Plant Biodiversity in a Megadiverse Country

Abstract:  An important question in conservation biology is the extent to which the number of taxonomic supraspecific categories can serve as surrogates of species richness. This issue has been little explored in highly diverse areas. We used 113 floristic inventories from throughout Mexico, a megadiverse country, to evaluate the potential of higher-taxon richness for predicting local species richness of vascular plants. This large biodiversity data set includes the main vegetation types found across the country. In all, 247 families, 2,398 genera, and 11,890 species were used for the analysis, representing 99.6%, 90.2%, and 53.2% of the respective totals recorded in the country. We hypothesized that the number of genera and species would be accurately predicted by the richness of the higher taxon. To avoid getting spurious regressions resulting from the logical increase in lower-taxon richness as a higher taxon becomes richer, we calculated new response variables by subtracting from the number of elements in the lower taxon group the number of those in the higher taxon; these variables were "excess species" (number of species minus number of genera or families) and "excess genera" (number of genera minus number of families). Our results indicate that genera provide very effective surrogates for estimation of local species richness ( R ²= 0.85), whereas families have a more limited potential for this purpose ( R ²= 0.64). The predictive capacity of the diversity of higher taxon increased when the analyses were constrained to particular vegetation types (maximum R ²= 0.95 for genera). This surrogate method may be a valuable tool in locating and designing representative systems of protected areas for vascular plant diversity, especially in megadiverse countries, where conservation efforts are hindered by the lack of complete inventories and insufficient resources.     

Latitude or biogeographic breaks? Determinants of phenotypic (co)variation in fitness-related traits in Betaeus truncatus along the Chilean coast

Ectothermal organisms distributed along environmental gradients in a wide geographical distribution display extensive phenotypic variation. This is particularly pervasive along latitudinal clines, which are linked to gradual changes in environmental factors. Widespread species may also be distributed among biogeographic breaks, which in contrast to smooth clines, often show abrupt changes in phenotypic traits. In species with widespread latitudinal distribution that also encompass important biogeographical breaks, it is not clear which of those factors prevails on shaping the phenotypic variation or if some traits are particularly more sensitive to one or the other. To evaluate this, we measured 4 fitness-related traits in 6 populations of the intertidal snapping shrimp Betaeus truncatus, as its distribution along Chile expands over 40° in latitude and three major biogeographical provinces. Here, we statistically evaluated the role of both, latitude and biogeographic breaks, on mean population values of fitness-related traits but also on the variances and covariances (i.e., P-matrix) between them. Overall, our results (1) indicate that latitude is more important than breaks in shaping the phenotypic variation of most of these fitness-related traits, (2) show that the differences in the variance–covariance relationship among traits between the extremes of the gradient arises from gradual increases in variance and rather sharp changes in covariance at mid-latitudes and (3) show that at present, it is difficult to unambiguously determine whether natural selection or plasticity is responsible for the observed pattern in means, variances and covariances and only further work might disentangle these possibilities.     

Large-scale biodiversity patterns in freshwater phytoplankton

Our planet shows striking gradients in the species richness of plants and animals, from high biodiversity in the tropics to low biodiversity in polar and high-mountain regions. Recently, similar patterns have been described for some groups of microorganisms, but the large-scale biogeographical distribution of freshwater phytoplankton diversity is still largely unknown. We examined the species diversity of freshwater phytoplankton sampled from 540 lakes and reservoirs distributed across the continental United States and found strong latitudinal, longitudinal, and altitudinal gradients in phytoplankton biodiversity, demonstrating that microorganisms can show substantial geographic variation in biodiversity. Detailed analysis using structural equation models indicated that these large-scale biodiversity gradients in freshwater phytoplankton diversity were mainly driven by local environmental factors, although there were residual direct effects of latitude, longitude, and altitude as well. Specifically, we found that phytoplankton species richness was an increasing saturating function of lake chlorophyll a concentration, increased with lake surface area and possibly increased with water temperature, resembling effects of productivity, habitat area, and temperature on diversity patterns commonly observed for macroorganisms. In turn, these local environmental factors varied along latitudinal, longitudinal, and altitudinal gradients. These results imply that changes in land use or climate that affect these local environmental factors are likely to have major impacts on large-scale biodiversity patterns of freshwater phytoplankton.     

Small-scale pattern of a California current zooplankton assemblage

The small-scale vertical (10s of meters) and horizontal (100s to 1000s of meters) distribution of zooplankton in the California Current near Guadalupe Island, Baja California, Mexico was studied. Vertical distributions were sampled using a vertically-towed Longhurst-Hardy Plankton Recorder (LHPR) which gave a sequence of samples, each integrated over about 5 m, from 250 m to the surface. Because of the sampling biases of the LHPR, details in vertical structure of less than 15 to 20 m were not considered. The pattern of the vertical tows and the variability of the integrated counts of species were used to infer horizontal distribution. Four series of 8 tows each were taken around noon and midnight over a 2-day period. Four of the 8 tows in each series were randomly positioned within 2000 m of a parachute drogue (first day) or a fixed geographic position (second day); four were replicate tows taken at the drogue or the fixed position. Sixty-seven taxonomic categories were counted. The replicate tows, separated by no more than a few hundred meters, gave more similar vertical profiles for species than did the random tows, with separations of 100s to 1000s of meters. The night replicate tows showed less variability in depth distribution than did either the night random or any of the day tows, leading to the hypothesis that the vertical distributions observed were generated by interactions of the organisms' diel behavior with internal waves. Variability of abundance estimates using the integrated counts was the same for both replicate and random tows, indicating that horizontal patches may be smaller than 100 m. No evidence was found for a day-night change in patch size, or for a consistent overlapping of patches of different species. Replicate tows gave more similar estimates of community structure (relative proportions of species) than did random tows. Overall day community structure was more similar between tows than night structure. Similarities in species' proportions of any random tow to the replicate tows or to other random tows of a series decreased with increasing distance between the tows being compared. This decrease was greater for the night samples, suggesting that community structure is more heterogeneous at night.This study is based in part on a dissertation submitted in partial fulfillment of the requirements for the Ph.D. degree at the University of California, San Diego, and was supported by National Science Foundation Grant GB 12413 and the Marine Life Research Program of the Scripps Institution of Oceanography.     

Endolithic invertebrate communities and bioerosion rates in southwestern Atlantic intertidal consolidated sediments

Organisms boring into intertidal consolidated sediments generate bioerosion. It is generally unknown, however, whether they can significantly contribute to coastline retraction. In this paper, we describe endolithic communities and estimate bioerosion and physical erosion rates at three southwestern Atlantic intertidal sites (37, 38, and 42°S; Argentina). In the northernmost site, we have also analyzed spatial variation in species richness and abundance as a function of height within the tidal slope, orientation of the rock surface in relation to breaking waves (i.e., facing or not), and rock hardness. The number of species and the combined abundance of individuals from the different species were larger at the low intertidal level but did not differ between surface orientations. The density of chemically boring organisms increased with increasing rock hardness and calcium carbonate content. In contrast, no correlation was found between rock hardness and the abundance of organisms that bore by mechanical means. Endolithic community composition and bioerosion rates differed among the three sites, the latter being higher at the site with the softer substrate. Bioerosion estimates were two orders of magnitude lower than physical erosion estimates at each site. The bivalve Lithophaga patagonica was the species that contributed the most to bioerosion at all these locations. While results suggest that bioerosion contributes little to overall coastal erosion at the three study sites, boring organisms might still facilitate physical erosion by weakening the rock either via chemical or mechanical means. Besides, their apparently inconsequential direct action as bioeroders can have positive consequences for biodiversity via increased habitat complexity.     

Latitudinal and bathymetric trends in body size of the deep-sea gastropod<Emphasis Type="Italic"> Troschelia berniciensis</Emphasis> (King)

Body size is a fundamental topic in ecology with important implications for community structure and biodiversity. Although there are numerous studies addressing patterns of geographic variation of body size in deep-sea benthos, results are conflicting. Thus geographic patterns of body size in deep-sea organisms remain poorly described. We analysed depth and latitudinal trends of body size in a species of gastropod, Troschelia berniciensis (King, 1846) from the eastern North Atlantic. We tested the hypotheses that (1) body size increases linearly with latitude and (2) body size increases with depth. Results partially supported the predictions. Firstly, there was a significant linear increase of body size with latitude, but this trend was weak. Secondly, body size decreased with depth. Environmental gradients that cause large-scale patterns of body-size variation in surface environments would have little effect on communities living at great depths. Latitudinal and depth clines may be produced by independent mechanisms that operate on different scales of time and space.Communicated by J.P. Thorpe, Port Erin     

Population and species diversity fluctuations in a rocky intertidal community relative to severe aerial exposure and sediment burial

From a series of 10 quarterly assessment between October 1975 and May 1978 (inclusive), fluctuations in abundance were determined for macroinvertebrates and macrophytes of a rocky intertidal community on Santa Cruz Island, California, USA. During afternoon low tides in late fall and winter of the first 2 yr of study, organisms of the upper and middle intertidal zones were subjected to prolonged aerial exposure. Many species there tolerated this exposure, but die-backs occurred for a barnacle (Chthamalus fissus/C. dalli) and several algae (Endocladia muricata, Pelvetia fastigiata f. gracilis, Corallina officinalis var. chilensis, Corallina vancouveriensis, Cylindrocarpus rugosus and Codium fragile). These die-backs were succeeded by blooms of Ulva californica and Porphyra perforata. In the upper and middle intertidal zones, the major cover organisms that could tolerate prolonged aerial exposure were disproportionately prevalent and appeared to be maintained by the periodic repression of species intolerant to such exposure. In February 1978, heavy rainfall caused sediment inundation of the middle and lower intertidal zones. This event was followed by declines in abundance of a barnacle (Tetraclita rubescens) and several algae (Pelvetia fastigiata f. gracilis and corallina spp.). Shannon-Wiener H species diversity fluctuated from a high in October to a low the following May during both 1975–1976 and 1976–1977 in conjunction with the period of increased daytime aerial exposure in late fall and winter. A further decline in diversity following sediment inundation in February 1978 contributed to a long-term trend of declining H species diversity (3.06 in October 1975 to 1.87 in May 1978). We hypothesize that predictable late fall to winter aerial exposure stresses, in combination with a random physical disturbance (sediment burial), exceeded an optimal intermediate level of disturbance predicted for maximal species diversity.     

Oxygen-binding by haemocyanins from an ecological series of amphipod crustaceans

The oxygen-binding properties of haemocyanins (Hc) from three species of gammaridean amphipods, Gammarus locusta (L.) (subtidal), Echinogammarus pirloti (Sexton and Spooner), (intertidal, marine) and E. marinus (Leach) (intertidal, estuarine), one species of hyalid amphipod Hyale nilsonni Rathke (high intertidal, marine) and the talitrid amphipod Orchestia gammarellus (Pallas) (semi-terrestrial) have been studied. All the species were collected from the Firth of Clyde, Scotland, during the spring of 1992. The oxygen-carrying capacity of haemolymph from each species was low, although variable, and was correlated with the low concentration of Hc present. The Hc oxygen-affinity of native gammarid haemolymph was relatively high [partial pressure of oxygen required for half-saturation, P₅₀=4 to 5 torr (0.53 to 0.67 kPa)] at their respective in vivo pH values. At equivalent pH, however, Hc from G. locusta displayed a lower O₂-affinity than either Echinogammarus species. Gammarid Hcs had a large Bohr effect ( log P₅₀/ pH=-1.16 to-1.47). Resuspended Hc isolated from whole H. nilsonni showed similar O₂-binding properties to those of the gammaridean amphipods [P₅₀=6.3 torr (1.44 kPa) at pH=8.0; log P₅₀/pH=-1.20]. Comparable data for haemolymph from O. gammarellus showed that the Hc had a lower affinity for O₂ [P₅₀=14.1 torr (1.87 kPa) at in vivo pH] and exhibited a more moderate Bohr effect ( log P₅₀/ pH=-0.79). To eliminate the possibility that these differences were due to the different haemolymph constituents, each of the Hcs were pelleted and resuspended in physiological saline. The differences noted above persisted, demonstrating that they were due to inherent O₂-binding properties of the Hc molecules themselves. An increase in L-lactate resulted in an increase in Hc oxygen-affinity for both Echinogammarus species but not for O. gammarellus. This study has confirmed that there is a clear difference between Hcs from aquatic and semi-terrestrial amphipod genera. The results lend further support to the hypothesis that the move on to land by amphipod crustaceans is accompanied by a decrease in Hc oxygen-affinity, a decrease in the Bohr effect and a decrease in effector (in this case L-lactate) sensitivity.     

Species-specific differences in pure tonal whistle vocalizations of five western North Atlantic dolphin species

Summary Pure tonal whistle vocalizations from five species of dolphins found in the western North Atlantic had consistent, species-specific characteristics. The degree of differences between species, as based on the results of multivariate discriminant analysis (Fig. 2), correlated with the taxonomic and zoogeographic relations of the five dolphin species. Congeneric species had more similar vocalizations than species of different genera. Differences between sympatric species were greater than differences between allopatric species. Of the six whistle parameters measured, maximum frequency had the lowest coefficient of variation for all five species, and duration and number of inflection points had the highest coefficients of variation for all five species.     

Role of competition and predation in determining habitat occupancy of Cerithiidae (Gastropoda: Prosobranchia) on the rocky,intertidal, Red Sea coasts of Sinai

Six cerithiid snail species occur on rocky intertidal flats along the Sinai coasts of the Red Sea: Clypeomorus moniliferum, Cerithium caeruleum, C. scabridum, C. columna, Clypeomorus tuberculatum and Cerithium echinatum. The present study, conducted at 22 stations covering almost the whole length of Sinai, covered the 4 yr period from October 1972 to August 1976, and describes the habitat occupancy of 5 of these species (C. echinatum is excluded for lack of data). Several of these species (sometimes all) often occur together, and in such cases are distincly segregated by habitat. However all species considerably overlap in their distribution along the axes of four major interrelated abiotic gradients, thus excluding the possibility that habitat segregation is determined by larval settlement preferences. Other distributional patterns observed at some sites, such as lack of overlap or contact between belts of the various species and the relative abundance of food available to all species, make postlarval competitive interactions unlikely. The existence and the degree of proximity of a coral reef with its associated predatory fishes, influence the cerithiids' distributional patterns. Differences between the cerithiid species in their vulnerability to fish predation, associated with differences between sites in the abundance and the accessibility of predatory fishes, and in the availability of refuges for each cerithiid species, can satisfactorily explain the observed distributional patterns including co-occurrence with habitat segregation. It is proposed that habitat segregation is caused by predation on young stages by generalist fishes which may totally eliminate a certain species at a given site; the same site may provide refuges for recruits of another species, allowing these to survive to an advanced age. In general, the flat's structural complexity is associated with its diversity of refuges from predation, and hence with the number of co-existing species. This mechanism for co-existence and habitat segregation in tropical Cerithiidae may also be instrumental in maintaining the high species diversity of other tropical benthic communities.Paper No. 12 in the series Colonization of the Eastern Mediterrancan by Red Sea species immigrating through the Suez Canal     

Effects of site-selection bias on estimates of biodiversity change

Estimates of biodiversity change are essential for the management and conservation of ecosystems. Accurate estimates rely on selecting representative sites, but monitoring often focuses on sites of special interest. How such site-selection biases influence estimates of biodiversity change is largely unknown. Site-selection bias potentially occurs across four major sources of biodiversity data, decreasing in likelihood from citizen science, museums, national park monitoring, and academic research. We defined site-selection bias as a preference for sites that are either densely populated (i.e., abundance bias) or species rich (i.e., richness bias). We simulated biodiversity change in a virtual landscape and tracked the observed biodiversity at a sampled site. The site was selected either randomly or with a site-selection bias. We used a simple spatially resolved, individual-based model to predict the movement or dispersal of individuals in and out of the chosen sampling site. Site-selection bias exaggerated estimates of biodiversity loss in sites selected with a bias by on average 300–400% compared with randomly selected sites. Based on our simulations, site-selection bias resulted in positive trends being estimated as negative trends: richness increase was estimated as 0.1 in randomly selected sites, whereas sites selected with a bias showed a richness change of −0.1 to −0.2 on average. Thus, site-selection bias may falsely indicate decreases in biodiversity. We varied sampling design and characteristics of the species and found that site-selection biases were strongest in short time series, for small grains, organisms with low dispersal ability, large regional species pools, and strong spatial aggregation. Based on these findings, to minimize site-selection bias, we recommend use of systematic site-selection schemes; maximizing sampling area; calculating biodiversity measures cumulatively across plots; and use of biodiversity measures that are less sensitive to rare species, such as the effective number of species. Awareness of the potential impact of site-selection bias is needed for biodiversity monitoring, the design of new studies on biodiversity change, and the interpretation of existing data.     

Factors affecting macroalgal distribution in a eutrophic tropical lagoon in Taiwan

Factors affecting distribution of macroalgal periphyton were examined during a complete seasonal cycle in Tapong Bay, a eutrophic tropical lagoon in southern Taiwan. Water residence time varied from a few days to weeks. Total biomass and species richness declined with increasing residence time. However, they appeared to exhibit a unimodal seasonal pattern across all study sites, with blooms and greater richness in winter and spring and lower values in summer and fall. Nonmetric multidimensional scaling ordination of macroalgal communities reveals a clear gradual continuum of changes in species composition along the flushing gradient, suggesting the communities were primarily structured by site, and secondarily by season. The fast-flushing region was dominated by the chlorophycean genus Ulva, which was replaced by Enteromorpha intestinalis at mid-flushing levels, while the cyanobacterium Lyngbya majuscula was the dominant species in the slow-flushing region. Tissue nitrogen, but not tissue phosphorus, of these dominant species increased with increasing nutrient availability as a result of slow flushing. Our results suggest that water motion was an important selective factor for the spatial dominance of macroalgal species in Tapong Bay. This study demonstrates that species-dependent ordination is more sensitive in discriminating between sites than are species-independent measures such as total biomass and nutrient content when monitoring coastal eutrophication in the tropics. However, more-sensitive ordination provides only an early warning that a community is changing; less-sensitive measures are also required to indicate the magnitude and type of these environmental changes.Communicated by T. Ikeda, Hakodate