Estimates Of Total Species Richness Research Articles

Impact of specimen type on findings for bacterial composition within the intestinal tract of dogs and cats with and without chronic enteropathy.

To compare bacterial diversity and community composition among fecal, rectal swab, and colonic mucosal biopsy specimens from dogs and cats with and without chronic enteropathy (CE). 9 healthy dogs, 8 dogs with CE, 8 healthy cats, and 9 cats with CE. In a cross-sectional study design, fecal, rectal swab, and colonic mucosal biopsy specimens were obtained by colonoscopy from healthy dogs and dogs and cats with CE. Fecal and rectal swab specimens were collected from healthy cats. Genomic DNA was extracted, the 16S rRNA V4 gene region was amplified, and sequencing was performed by use of primers 515F to 806R on a paired-end platform. For healthy dogs and dogs and cats with CE, bacterial diversity based on the Chao1 estimate of total species richness was higher for colonic mucosal biopsy specimens than for fecal specimens. Analysis of similarities by use of the Bray-Curtis dissimilarity index revealed that the bacterial communities captured in rectal swab specimens were similar to those captured in fecal specimens for healthy dogs and dogs with CE and similar to those captured in colonic mucosal biopsy specimens for both dog groups and cats with CE. Rectal swab and colonic biopsy specimens were successfully used to characterize the bacteriome of the intestinal tract in dogs and cats by 16S rRNA gene sequencing. Although the specimen types evaluated in this study were not interchangeable in results, rectal swab specimens were practical to collect from dogs and cats to study bacterial composition within the intestinal tract and may provide an alternative to colonic mucosal biopsy and fecal specimens.

Comparability and complementarity of reef fish measures from underwater visual census (UVC) and baited remote underwater video stations (BRUVS)

The much-publicized threats to coral reef systems necessitate a considered management response based on comprehensive ecological data. However, data from large reef systems commonly originate from multiple monitoring programs that use different methods, each with distinct biases that limit united assessments of ecological status. The effective integration of data from different monitoring methods would allow better assessment of system status and hence, more informed management. Here we examine the scope for comparability and complementarity of fish data from two different methods used on Australia's Great Barrier Reef (GBR): underwater visual census (UVC) and baited remote underwater video stations (BRUVS). We compared commonly reported reef fish measures from UVC and BRUVS on similar reef slope habitats of three central GBR reefs. Both methods recorded similar estimates of total species richness, although ~30% of recorded species were not common to both methods. There were marked differences between methods in sub-group species richness, frequency of species occurrences, relative abundances of taxa and assemblage structure. The magnitude and orientation of inter-method differences were often inconsistent among taxa. However, each method better categorized certain components of fish communities: BRUVS sampled more predatory species in higher numbers while UVC was similarly better at sampling damselfishes (Pomacentridae). Our results suggest limited scope for direct or adjusted comparisons of data from UVC and BRUVS. Conversely, complementary aspects of the two methods confirm that their integration in monitoring programs will provide a more complete and extensive assessment of reef fish status for managers than from either method alone.

Rotifera of various aquatic environments of Costa Rica in reference toCentral American rotifer fauna

Detailed surveys on rarely examined aquatic ecosystems often lead to the discovery of new species of high conservation value. This study directed towards the recognition of a variety of aquatic environments in Costa Rica 40 habitats, including lakes, wetlands, and small aquatic systems, e.g., ponds, ditches, puddles, tree holes, and bromeliads established the presence of 105 species of Monogononta representing 33 genera. In total, 91 species and 19 genera were found to be new for Costa Rica, including 29 species recorded for the first time in Central America e.g., Ascomorpha klementi, Beauchampia crucigera, Brachionus mirabilis, Cephalodella panarista, Filinia saltator, Horaella brehmi, Lecane amazonica, Lecane pawlowskii, Lepadella lindaui, and Mytilina acanthophora . The application of 2 estimates of total species richness allowed us predict that 70 new rotifer species may potentially be found in Costa Rica. Thus, we assume that only about 60% of the potential Costa Rican rotifer diversity was ascertained in our study. The most diverse genus was Lecane with 36 species. Among the most frequent rotifers there were some lecanid species, e.g., Lecane bulla, Lecane hamata, Lecane closterocerca and Lecane leontina, and also Colurella obtusa, Plationus patulus, Anuraeopsis fissa, and Platyias quadricornis.

Upscaling biodiversity: estimating the species–area relationship from small samples

AbstractThe challenge of biodiversity upscaling, estimating the species richness of a large area from scattered local surveys within it, has attracted increasing interest in recent years, producing a wide range of competing approaches. Such methods, if successful, could have important applications to multi‐scale biodiversity estimation and monitoring. Here we test 19 techniques using a high quality plant data set: the GB Countryside Survey 1999, detailed surveys of a stratified random sample of British landscapes. In addition to the full data set, a set of geographical and statistical subsets was created, allowing each method to be tested on multiple data sets with different characteristics. The predictions of the models were tested against the “true” species–area relationship for British plants, derived from contemporaneously surveyed national atlas data. This represents a far more ambitious test than is usually employed, requiring 5–10 orders of magnitude in upscaling. The methods differed greatly in their performance; while there are 2,326 focal plant taxa recorded in the focal region, up‐scaled species richness estimates ranged from 62 to 11,593. Several models provided reasonably reliable results across the 16 test data sets: the Shen and He and the Ulrich and Ollik models provided the most robust estimates of total species richness, with the former generally providing estimates within 10% of the true value. The methods tested proved less accurate at estimating the shape of the species–area relationship (SAR) as a whole; the best single method was Hui's Occupancy Rank Curve approach, which erred on average by <20%. A hybrid method combining a total species richness estimate (from the Shen and He model) with a downscaling approach (the Šizling model) proved more accurate in predicting the SAR (mean relative error 15.5%) than any of the pure upscaling approaches tested. There remains substantial room for improvement in upscaling methods, but our results suggest that several existing methods have a high potential for practical application to estimating species richness at coarse spatial scales. The methods should greatly facilitate biodiversity estimation in poorly studied taxa and regions, and the monitoring of biodiversity change at multiple spatial scales.

“Pollard-walk” Butterfly Survey does not Warrant the Equity of Sampling-completeness among Butterfly Families: A Case Study with Tropical Butterfly Fauna in Bhutan

Complete or even sub-complete inventories of biodiversity often remain well out of reach, especially when dealing with speciose taxonomic groups, such as insects in general and butterfly fauna in particular. Moreover, it is even uncertain that similar completeness levels may be reached among taxonomic subsets within a same surveyed taxonomic group. For example, one can wonder whether sampling butterfly fauna according to the commonly implemented Pollard walk consistently ensure a similar recording efficiency (i.e. similar sampling completeness) according to the different butterfly families. To address this issue and quantify the possible unevenness of sampling completeness between five main butterfly families, we consider a Pollard walk butterfly survey of tropical butterfly fauna, carried out along Sankosh River (Bhutan) by Arun P. Singh. Reasonably accurate estimates of the true total species richness and the corresponding sampling completeness were derived, for each butterfly family, by implementing the recently developed procedure of least-biased extrapolation of the species accumulation curve. Whereby, a reliable evaluation of the level of sampling completeness is obtained for each butterfly family. For the inventory under consideration, a significant scatter of sampling completeness levels between the five families is highlighted: sampling completeness levels range from 65% for Lycaenidae to quasi exhaustivity for Papilionidae, with intermediate levels for the other three families. 2 These findings revealed that Pollard walk survey may lead to appreciable differences of sampling completeness level among the different butterfly families. Besides, this study provides a reliable estimate of the total species richness of butterfly fauna in the surveyed ecosystem, amounting to no less than 280 species concentrated in a rather reduced area along Sankosh River.

SESGOS ASOCIADOS A CENSOS VISUALES DE PECES ARRECIFALES EN EL PACÍFICO ORIENTAL TROPICAL: IMPLICACIONES DEL USO DE TRANSECTOS SENCILLOS O DE TAMAÑO MIXTO, DE LA EXPERIENCIA DE LOS BUZOS Y DE LA ESTIMACIÓN DE LA TALLA

Visual censuses on belt transects implemented to assess reef fish populations in the Eastern Tropical Pacific (ETP) vary greatly in the size of sampling units and census protocols. To examine the effects of such variation on estimates of species richness and density, and to help identify an appropriate (accurate, precise and efficient) protocol, we compared two belt transect methods: a single-size transect (one 30 x 2 m band) and a mixed-size transect (two bands, a 50 x 5 m band for large, mobile fishes, and a 50 x 1 m band for small or cryptic fishes). Three observers with different experience conducted 72 visual censuses on three fixed transects at El Arrecife coral formation in Malpelo Island, Colombia, following a factorial design to evaluate the effect of methods, observers and fish size estimation on the accuracy and precision of species richness and density estimates. Additionally, we examined the efficiency (cost in time in relation to the accuracy and precision) of each method. The Mixed Transect (MT) yielded more precise estimates of population and community parameters and more accurate estimates of species richness. However, it had a high implementation cost (25 min/census) and consistently underestimated total density and the density of species recorded in the 50 x 5 m transect (probably due to its greater band width and associated decrease in species detectability). The Single Transect (ST) was more cost-efficient (14 min/census) and produced more accurate estimates of total and specific density for most species (except cryptic or small ones). Both methods were biased by the estimation of fish size during the censuses and by observer inexperience, so they should be implemented under oceanographic conditions that facilitate carrying out visual censuses and by divers with prior training. Alternatively, random sampling can be performed independently of visual censuses to estimate size frequency distributions without affecting estimates of abundance and species richness. Given the generally poor visibility in the ETP and insufficient funding for research and monitoring projects, the ST protocol is more suitable for conducting surveys of multiple species. In addition to producing more accurate estimates of total and specific density for most species, the greater cost-efficiency of STs allows to increase the number of replicates and thus to improve the estimate of total species richness and the precision of all population and community estimates. However, due to the greater accuracy of the MT to assess total species richness and density of small and cryptic species, an alternative would be to use a MT of at least 30 m length, with a maximum width of 2 m for censusing large and mobile species, and of 1 m for small and cryptic species.

Comparison of Two Sampling Designs for Fish Assemblage Assessment in a Large River

AbstractWe compared the efficiency of stratified random and fixed‐station sampling designs to characterize fish assemblages in anticipation of dam removal on the Penobscot River, the largest river in Maine. We used boat electrofishing methods in both sampling designs. Multiple 500‐m transects were selected randomly and electrofished in each of nine strata within the stratified random sampling design. Within the fixed‐station design, up to 11 transects (1,000 m) were electrofished, all of which had been sampled previously. In total, 88 km of shoreline were electrofished during summer and fall in 2010 and 2011, and 45,874 individuals of 34 fish species were captured. Species‐accumulation and dissimilarity curve analyses indicated that all sampling effort, other than fall 2011 under the fixed‐station design, provided repeatable estimates of total species richness and proportional abundances. Overall, our sampling designs were similar in precision and efficiency for sampling fish assemblages. The fixed‐station design was negatively biased for estimating the abundance of species such as Common Shiner Luxilus cornutus and Fallfish Semotilus corporalis and was positively biased for estimating biomass for species such as White Sucker Catostomus commersonii and Atlantic Salmon Salmo salar. However, we found no significant differences between the designs for proportional catch and biomass per unit effort, except in fall 2011. The difference observed in fall 2011 was due to limitations on the number and location of fixed sites that could be sampled, rather than an inherent bias within the design. Given the results from sampling in the Penobscot River, application of the stratified random design is preferable to the fixed‐station design due to less potential for bias caused by varying sampling effort, such as what occurred in the fall 2011 fixed‐station sample or due to purposeful site selection.

Impacts of data quality on the setting of conservation planning targets using the species–area relationship

AbstractAimThe species–area relationship (SAR) is increasingly being used to set conservation targets for habitat types when designing protected area networks. This approach is transparent and scientifically defensible, but there has been little research on how it is affected by data quality and quantity.LocationEnglish Channel.MethodsWe used a macrobenthic dataset containing 1314 sampling points and assigned each point to its associated habitat type. We then used the SAR‐based approach and tested whether this was influenced by changes in (i) the number of sampling points used to generate estimates of total species richness for each habitat type; (ii) the nonparametric estimator used to calculate species richness; and (iii) the level of habitat classification employed. We then compared our results with targets from a similar national‐level study that is currently being used to identify Marine Conservation Zones in the UK.ResultsWe found that targets were affected by all of the tested factors. Sample size had the greatest impact, with specific habitat targets increasing by up to 45% when sample size increased from 50 to 300. We also found that results based on the Bootstrap estimator of species richness, which is the most widely used for setting targets, were more influenced by sample size than the other tested estimators. Finally, we found that targets were higher when using broader habitat classification levels or a larger study region. However, this could also be a sample size effect because these larger habitat areas generally contained more sampling points.Main conclusionsHabitat targets based on the SAR can be strongly influenced by sample size, choice of richness estimator and the level of habitat classification. Whilst setting habitat targets using best‐available data should play a key role in conservation planning, further research is needed to develop methods that better account for sampling effort.

Repeated sampling reveals differential variability in measures of species richness and community composition in planktonic protists

Diversity metrics and descriptors of protistan community structure were calculated from 12 samples of 10 l each collected from the Bay of Villefranche in the NW Mediterranean Sea. Variability of the sampling was on scales of minutes and meters. The individual samples were compared with each other and compared with a pooled data set from the total volume of 120 l, considered as the 'true' community. We focused on a single group of planktonic protists, tintinnids, a coherent functional and phylogenetic group in which morpho-species identifications by light microscopy are unambiguous. Tintinnid abundance in the samples ranged from 217 to 321 cells of 16-21 species with the number of rare species in a sample (< 1% of abundance) positively related to species richness of the sample. Rarefaction estimates of total species richness in the 12 samples ranged from 21 ± 3.5 to 37 ± 3.6 compared with the 34 species of the pooled data set. The measures of similarity reflected the differences between samples in both the numbers and identities of the least abundant or rare species. The species abundance distribution using pooled data was best fit by a log-series or geometric distribution; eight species accounted for about 90% of total cells and most species, the remaining 22 out of 34, were 'rare' (concentration < 1% of total cells). Among the samples, 5 were best fit by a geometric model, 1 by a log-series distribution, 2 by a log-normal or log-series model, and 4 could not be clearly assigned a particular distribution. Our results suggest that single sample estimates of species richness are relatively robust compared with measures of taxonomic similarity and species abundance distribution. When measuring differences among populations sample variability should be considered.

Influence of Sampling Effort on the Estimated Richness of Road-Killed Vertebrate Wildlife

Road-killed mammals, birds, and reptiles were collected weekly from highways in southern Brazil in 2002 and 2005. The objective was to assess variation in estimates of road-kill impacts on species richness produced by different sampling efforts, and to provide information to aid in the experimental design of future sampling. Richness observed in weekly samples was compared with sampling for different periods. In each period, the list of road-killed species was evaluated based on estimates the community structure derived from weekly samplings, and by the presence of the ten species most subject to road mortality, and also of threatened species. Weekly samples were sufficient only for reptiles and mammals, considered separately. Richness estimated from the biweekly samples was equal to that found in the weekly samples, and gave satisfactory results for sampling the most abundant and threatened species. The ten most affected species showed constant road-mortality rates, independent of sampling interval, and also maintained their dominance structure. Birds required greater sampling effort. When the composition of road-killed species varies seasonally, it is necessary to take biweekly samples for a minimum of one year. Weekly or more-frequent sampling for periods longer than two years is necessary to provide a reliable estimate of total species richness.

Estimating total plant species richness in depressional wetlands in the longleaf pine ecosystem

We evaluated methodology for estimating total plant species richness in seasonally inundated depressional wetlands of the longleaf pine (Pinus palustris Mill.) ecosystem. Our objectives were to assess non-parametric estimators of plant species richness based on species incidence plot samples and to determine the minimum sampling requirement for accurate extrapolation of species richness. We quantified species accumulation in varying sample plot areas and spatial distribution within nine depressional wetlands. We recorded species presence on 1 m2, 4 m2, and 100 m2 plots along transects extending across each wetland. Increasing sample area from 1 m2 to 4 m2 plots resulted in an increase in mean species richness up to 33%. EstimateS was used to estimate total species richness for each wetland and sampling method. Species accumulation curves did not reach a plateau and none of the estimates showed a convergence of estimated and observed richness. Due to the large number of unique species and the heterogeneous distribution of species in these hyperdiverse wetlands, we conclude that the most commonly used non-parametric estimators are not effective as tools to obtain accurate estimates of total species richness.

The impacts of past cultivation on the reptiles in a South African grassland

Habitat transfonnation is the primary anthropogenic threat to global biodiversity. Fragmentation of reptile populations following habitat transfonnation within a landscape can lead to the extirpation of species. We investigated the effects of land-use on the species richness and abundance of reptile assemblages in three habitat types (two natural and one modified) in the grasslands of Gauteng, South Africa. Using trap arrays, we surveyed reptiles in primary grassland with little or no rock cover, primary grassland with large quartzite outcrops and scattered rocks, and secondary grasslands that were historically ploughed and cropped. We measured vegetation height and vegetation cover at these same localities. We caught significantly fewer reptile species in the historically cultivated sites than in either of the two natural habitat types. Differences in the reptile assemblage of each habitat type were not explained by either the spatial location or the vegetation structure of our trap sites but were well explained by the sites' habitat type. Estimates of total species richness indicated that we were able to adequately sample the reptile assemblages in the three habitat types, further supporting our observation of reduced species richness in the secondary grasslands. We infer that habitat transfonnation associated with cultivation e.g., rock removal, has had a detectable, negative impact on the species richness and composition of the local reptile assemblages. We recommend that land-use planning in Gauteng emphasise the need for areas of inter-connected, untransfonned habitat in order to mitigate the negative impacts of habitat transfonnation on the local reptile diversity.

Spatial patterns of meiofauna and diversity of nematode species assemblages in the Uvea lagoon (Loyalty Islands, South Pacific)

Meiofauna assemblages were investigated at 15 stations on triplicated samples in the Uvea Atoll (Loyalty Islands) in relation to 9 selected environmental parameters. Spatial patterns and variability of meiofauna density were quantified according to location, macrofauna and nematode species assemblages. Meiofauna was dominated by ciliates and nematodes. Densities of total meiofauna and of most of the meiofauna taxa were significantly higher in the back reef North Pléiades stations than the leeward side of the Island. The highest correlation between biotic patterns and environmental parameters that best explains the pattern was with sediment thickness and to a lesser extent organic matter, C/N ratio and depth. One hundred and thirty-four nematode species were identified with four dominant species Chromadora macrolaimoides, an undescribed species of Bolbonema, Daptonema svalbardense and Prochromadorella septempapillata. Three significantly different nematode species assemblages were detected in two of the previously described macrofauna assemblages by cluster analysis and multidimensional scaling methods suggesting that nematodes are more sensible ecological indicators than macrofauna. Diversity indices based on dominance were not significantly different among the three nematode species assemblages but indices based on species richness and rarefaction were significantly higher leeward of Uvea Island. Estimates of total species richness showed no sign of stabilizing with sample size. However, rare species stabilized very quickly, whereas abundant species were added with increasing sampling coverage, indicating a high spatial variability of the local composition of nematodes.

Estimating Sampling Effort for Biomonitoring of Nearshore Fish Communities in Small Central Minnesota Lakes

AbstractI estimated the sampling effort required to sufficiently describe the species richness and composition of fish inhabiting the nearshore (wadeable) zone of lakes and compared 10 species richness estimators in 56 similarly sized (small) central Minnesota lakes. A systematic sampling design was employed wherein 10 stations were equally spaced around each lake and the first station was selected randomly. Sampling methods consisted of a combination of backpack electrofishing and shoreline seining. Using sample‐based rarefaction curves, eight sampling stations produced at least 90% of the sampled species in 96% of the study lakes. Less sampling effort (four to six stations) was needed to describe the composition of the nearshore fish assemblage, as measured by similarity of species composition or species relative abundances in cumulative samples. The effort needed to sufficiently describe nearshore species richness was not related to observed species richness but was negatively correlated with species evenness among sampling stations. Estimates of total nearshore species richness were made using an asymptotic accumulation function, a log‐linear model, two abundance‐based nonparametric estimators, and six incidence‐based nonparametric estimators. All estimates of total species richness were correlated with observed species richness. Estimated total species richness exceeded observed species richness; however, this difference was smallest when species evenness was high. Nonparametric methods produced unrealistically high richness estimates if many species were encountered infrequently. Observed richness varied among lakes and was positively related to measures of lake integrity. Observed richness, estimated total richness, and sufficient effort levels were similar for lakes sampled twice, suggesting that both the sampling method and estimated levels of sufficient effort were robust. The results of this study suggest that more intensive nearshore sampling with seines and backpack electrofishing will be of limited benefit unless the detection of rare species is the major goal of sampling; alternative sampling gears may be needed to detect new species.

Spatial pattern in species richness of demersal fish assemblages on the continental shelf of the northern Mediterranean Sea: a multiscale analysis

The species richness pattern of groundfish species in the entire northern Mediterranean Sea was examined at 3 spatial scales: region, large biogeographical zone and basin. We analysed 1914 trawl hauls collected using a single sampling design in the trawlable areas of the continental shelves between the Strait of Gibraltar and the Strait of Dardanelles (from 36.3 to 45.7° N and 5.3° W to 28° E). Spatial pattern in species diversity was assessed using complementary methods (Chao2 estimates of total species richness, mean species richness and beta diversity). No matter which scale was used, the expected longitudinally decreasing trend in species richness, which has been widely described in previous studies, did not appear when comparing estimates of total species richness per unit of area. Only the mean species richness pattern showed a moderate eastwards decrease at the largest spatial scale, but the trend progressively disappeared as the scale of analysis was reduced. In contrast to what is usually expected, our results suggest that Atlantic inflow does not play a key role in the present spatial pattern of fish species richness within the northern Mediterranean Sea. Further- more, we show that the Aegean Sea can no longer be considered the least species-diverse zone in the northern Mediterranean Sea. Our results provide the first description of a quantitative 'reference state', with which the temporal changes in species richness patterns throughout the entire northern Mediterranean Sea can be compared in the future.

Seed dispersal into wetlands: Techniques and results for a restored tidal freshwater marsh

Although seed dispersal is assumed to be a major factor determining plant community development in restored wetlands, little research exists on density and species richness of seed available through dispersal in these systems. We measured composition and seed dispersal rates at a restored tidal freshwater marsh in Washington, DC, USA by collecting seed dispersing through water and wind. Seed dispersal by water was measured using two methods of seed collection: (1) stationary traps composed of coconut fiber mat along an elevation gradient bracketing the tidal range and (2) a floating surface trawl net attached to a boat. To estimate wind dispersal rates, we collected seed from stationary traps composed of coconut fiber mat positioned above marsh vegetation. We also collected a small number of samples of debris deposited along high tide lines (drift lines) and feces of Canada Goose to explore their seed content. We used the seedling emergence method to determine seed density in all samples, which involved placing the fiber mats or sample material on top of potting soil in a greenhouse misting room and enumerating emerging seedlings. Seedlings from a total of 125 plant species emerged, during this study (including 82 in river trawls, 89 in stationary water traps, 21 in drift lines, 39 in wind traps, and 10 in goose feces). The most abundant taxa includedBidens frondosa, Boehmeria cylindrica, Cyperus spp.,Eclipta prostrata, andLudwigia palustris. Total seedling density was significantly greater for the stationary water traps (212±30.6 seeds/m2/month) than the equal-sized stationary wind traps (18±6.0 seeds/m2/month). Lower-bound estimates of total species richness based on the non-parametric Chao 2 asymptotic estimators were greater for seeds in water (106±1.4 for stationary water traps and 104±5.5 for trawl samples) than for wind (54±6.4). Our results indicate that water is the primary source of seeds dispersing to the site and that a species-rich pool of dispersing propagules is present, an interesting result given the urbanized nature of the surrounding landscape. However, species composition of dispersing seeds differed from vegetation of restored and natural tidal freshwater marshes, indicating that planting is necessary for certain species. At other restoration sites, information on densities of dispersing seeds can support decisions on which species to plant.

Scale dependence of diversity measures in a leaf‐litter ant assemblage

A reliable characterization of community diversity and composition, necessary to allow inter‐site comparisons and to monitor changes, is especially difficult to reach in speciose invertebrate communities. Spatial components of the sampling design (sampling interval, extent and grain) as well as temporal variations of species density affect the measures of diversity (species richness S, Buzas and Gibson's evenness E and Shannon's heterogeneity H). Our aim was to document the small‐scale spatial distribution of leaf litter ants in a subtropical dry forest of the Argentinian Chaco and analyze how the community characterization was best achieved with a minimal sampling effort. The work was based on the recent standardized protocol for collecting ants of the leaf litter (“A.L.L.”: 20 samples at intervals of 10 m). To evaluate the consistency of the sampling method in time and space, the selected site was first subject to a preliminary transect, then submitted after a 9‐month interval to an 8‐fold oversampling campaign (160 samples at interval of 1.25 m). Leaf litter ants were extracted from elementary 1 m2 quadrats with Winkler apparatus. An increase in the number of samples collected increased S and decreased E but did not affect much H. The sampling interval and extent did not affect S and H beyond a distance of 10 m between samples. An increase of the sampling grain had a similar effect on S than a corresponding increase of the number of samples collected, but caused a proportionaly greater increase of H. The density of species m−2 varied twofold after a 9‐month interval; the effect on S could only be partially corrected by rarefaction. The measure of species numerical dominance was little affected by the season. A single standardized A.L.L. transect with Winkler samples collected &lt;45% of the species present in the assemblage. All frequent species were included but their relative frequency was not always representative. A log series distribution of species occurrences was oberved. Fisher's α and Shannon's H were the most appropriate diversity indexes. The former was useful to rarefy or abundify S and the latter was robust against sample size effects. Both parametric and Soberón and Llorente extrapolation methods outperformed non‐parametric methods and yielded a fair estimate of total species richness along the transect, a minimum value of S for the habitat sampled.

Pteridophyte species richness in Andean forests in Bolivia

I assessed the magnitude and distribution of pteridophyte species richness on the eastern Andean slope in Bolivia based on 676 study plots of 400 m2 each in forest habitats at 65 study sites. In total 755 species were recorded, including 426 (56%) epiphytes and 598 (79%) terrestrials, with 266 species (35%) recorded under both groups. Mean number of species per plot at a given site varied from 0 to 31.1 for epiphytes, 0 to 20.9 for terrestrials, and 0 to 47.9 for all species combined. The highest numbers of species recorded at a given study site were 110 epiphytes, 101 terrestrials, and 167 species in total. While overall there were more terrestrial than epiphytic species, at individual sites and plots the reverse was true, indicating that terrestrial species tended to be more patchily distributed than epiphytes. Despite high survey intensity, many species went unrecorded; the minimum estimate of total species richness obtained through extrapolation was 975 species overall, including 559 epiphytes and 880 terrestrials. A correlation analysis of species richness to 14 environmental parameters revealed a highly positive correlation to mean annual precipitation and bryophyte cover on tree branches (a proxy for air humidity). Significant correlations to other parameters (e.g. human impact, canopy height, etc.) reflected the covariance of these factors with precipitation and bryophyte cover. Despite a lack of data on the pteridophyte communities from much of the Bolivian Andes, it appears that in most of the countries, pteridophyte diversity can be protected by focussing the most humid parts of the Andean forests.

Comparative performance of species richness estimation methods.

In most real-world contexts the sampling effort needed to attain an accurate estimate of total species richness is excessive. Therefore, methods to estimate total species richness from incomplete collections need to be developed and tested. Using real and computer-simulated parasite data sets, the performances of 9 species richness estimation methods were compared. For all data sets, each estimation method was used to calculate the projected species richness at increasing levels of sampling effort. The performance of each method was evaluated by calculating the bias and precision of its estimates against the known total species richness. Performance was evaluated with increasing sampling effort and across different model communities. For the real data sets, the Chao2 and first-order jackknife estimators performed best. For the simulated data sets, the first-order jackknife estimator performed best at low sampling effort but, with increasing sampling effort, the bootstrap estimator outperformed all other estimators. Estimator performance increased with increasing species richness, aggregation level of individuals among samples and overall population size. Overall, the Chao2 and the first-order jackknife estimation methods performed best and should be used to control for the confounding effects of sampling effort in studies of parasite species richness. Potential uses of and practical problems with species richness estimation methods are discussed.

Species-area curves and estimates of total species richness in an old-field chronosequence

Average species-area curves were generated for vascular plants in 20 old-fields that were sampled in 1983, 1989, and 1994. These curves were fit with a saturating function to estimate total species richness for each old-field. Additional estimates of total species richness were generated by fitting the same saturating function to subsets of the species area curves and with a first-order jackknife procedure. Estimates of total species richness were strongly correlated with observed species richness. There was limited evidence suggesting that greater sampling was necessary to identify the same proportion of species in older, more species-rich old-fields.