True Species Richness Research Articles

Assessing electrofishing effort required to estimate species richness of fishes in nonwadeable rivers of Alabama, USA

AbstractObjectiveMuch of the fish biodiversity in the southeastern USA is found in lotic systems, but assessment of fish community structure in large nonwadeable rivers has lagged compared to streams. Sampling designs that adequately estimate species richness are a prerequisite to creating bioassessment metrics but thus far has not been attempted in highly biodiverse rivers in the southeastern USA east of the Mississippi River.MethodsFish communities in four nonwadeable rivers across Alabama spanning catchments of 2046–57,415 km2 were sampled using electrofishing in summer and fall of 2015 and 2016. All rivers were sampled during day; two rivers were also sampled at night to assess diel changes in species accumulation.ResultIn total, 55,239 fishes were collected across rivers, representing 106 species in 24 families. Species collected continued to increase as sampling increased in all river‐season combinations, rarely displaying an asymptote. Species generally accrued more quickly and accumulation curves showed more tendency to asymptote in fall than summer in all but the largest river. Species accumulated faster at night than during the day in both rivers during summer but was similar between diel periods in fall. On average, 95% of the species observed were collected in eight subreaches in fall but not until nine during summer; however, observed number of species was generally one to six species lower than mean estimates of true species richness. Sampling efforts collected approximately similar species assemblages across transects, years, season, and diel periods. Extrapolation of species accumulation curves suggested that 6–17 km of sampling distance would be required to collect all species present.ConclusionResults of this study demonstrate that assessing fish communities in species nonwadeable rivers requires an inordinate amount of sampling effort, which may be unattainable for many agencies. Further study is warranted to develop innovative solutions to overcome these logistical challenges.

A Brief Description of Avian Communities in Sungai Tongod Forest Reserve, Tongod, Sabah, Malaysia

A rapid assessment of the avifauna of Sungai Tongod Forest Reserve (STFR), a logged-over forest, was conducted in Tongod district in central Sabah, Malaysia. A modified MacKinnon List method was used to assess species diversity. The four-day survey recorded a total of 15 MacKinnon lists, with 342 individuals detected. A total of 85 species from 38 families were recorded, with H=4.07 and EH=0.70. True species richness was estimated (using SuperDuplicates® online calculator) to be approximately 114 species, with about 30 species not detected. There were 10 Bornean endemics, half of which were listed as Least Concerned, two as Near Threatened, and one as Vulnerable, in the IUCN Red List of Threatened Species. The Pellorneidae, Pycnonotidae and Nectariniidae were represented by eight, seven and six species respectively. The family Pycnonotidae had the highest number of individuals at 40 followed by Pellorneidae with 35. The five most detected species comprised 42.4 % of all individuals. The most detected species were the Bold-striped Tit-babbler (17 individuals), Green Iora (15), Pink-necked Green Pigeon (15), Black-and-yellow Broadbill (12), and Black-headed Bulbul (12). Most of the species detected (77) were forest-dependent, of which 62 were strictly forest birds. Insectivores comprised the most dominant dietary guild, i.e., 25 species (from 22 families). Frugivores ranked second with 25 species from 10 families.

Invertebrate richness, diversity and hatching patterns from a semi-arid pool in peninsular India using field sampling and sediment re-hydration

Effective methods for finding the true species richness are necessary for biodiversity research. Such assessments are especially difficult for short-lived freshwater invertebrates found in arid and semi-arid temporary habitats. However, many of these animals produce “resting eggs” that remain viable for a long time and hatch when the habitats refill with water. This aspect can be used to assess the true species richness of these assemblages. We performed a simple, fast, cost-effective, and reliable method of laboratory sediment rehydration along with standard field sampling to understand the richness, diversity and hatching patterns of invertebrates like rotifers, cladocerans, copepods and ostracods and large branchiopods from a temporary pool located in the semi-arid part of peninsular India. Twenty-two rotifers, 5 large branchiopods and 6 micro-crustaceans were found in the study of which 4 species were only found from the rehydrated sediment. Variation in the species composition was higher in the field samples than the lab ones. Field and laboratory species communities were distinct from each other. Species community comparison with a similar habitat nearly 150 km away showed a dissimilarity of 0.70 between the two. Contrasting environmental conditions between the field and lab combined with temporal variation in the hatching patterns of species might explain the dissimilarities seen in the fauna. We propose that the sediment rehydration method along with the field sampling can be used to reveal the true species richness of the local temporary water bodies.

Avifaunal Survey of Bukit Balingkadus, A Small Fragmented Forest in Ranau, Sabah, Malaysia

An avifaunal survey was carried out at Bukit Balingkadus Forest Reserve in Ranau, Sabah, Malaysia. The MacKinnon List method was used to assess species diversity. The four-day survey recorded a total of 16 MacKinnon lists with 388 individuals detected. A total of 86 species from 37 families were recorded, with H=3.89 and EH=0.65. True species richness was estimated (using SuperDuplicates® online calculator) to be approximately 114 species, with approximately 28 species not detected. There were 13 species of Bornean endemics, two of which were listed as Vulnerable in the IUCN Red List of Threatened Species. Pycnonotidae was the most speciose family with 10 species. Cuculidae and Megalaimidae were ranked second with 6 species each. Zosteropidae had the highest number of individuals at 47. The top ten most detected species made up 49.5 % of all species detected. The most detected species was the Chestnut-crested Yuhina (Zosteropidae). The majority of the species detected (81) were forest-dependent, of which 60 were strictly forest birds. Insectivores made up the most dominant dietary guild, i.e., a total of 41 species (from 22 families). Frugivores ranked second with 29 species from 10 families.

Unexpectedly high diversity of trypanosomes in small sub-Saharan mammals

The extremely species-rich genus Trypanosoma has recently been divided into 16 subgenera, most of which show fairly high host specificity, including the subgenus Herpetosoma parasitizing mainly rodents. Although most Herpetosoma spp. are highly host-specific, the best-known representative, Trypanosoma lewisi, has a cosmopolitan distribution and low host specificity. The present study investigates the general diversity of small mammal trypanosomes in East and Central Africa and the penetration of invasive T. lewisi into communities of native rodents. An extensive study of blood and tissue samples from Afrotropical micromammals (1528 rodents, 135 shrews, and five sengis belonging to 37 genera and 133 species) captured in the Central African Republic, Ethiopia, Kenya, Malawi, Mozambique, Tanzania, and Zambia revealed 187 (11.2%) trypanosome-positive individuals. The prevalence of trypanosomes in host genera ranged from 2.1% in Aethomys to 37.1% in Lemniscomys. The only previously known trypanosome detected in our dataset was T. lewisi, newly found in Ethiopia, Kenya, and Tanzania in a wide range of native rodent hosts. Besides T. lewisi, 18S rRNA sequencing revealed 48 additional unique Herpetosoma genotypes representing at least 15 putative new species, which doubles the known sequence-based diversity of this subgenus, and approaches the true species richness in the study area. The other two genotypes represent two new species belonging to the subgenera Ornithotrypanum and Squamatrypanum. The trypanosomes of white-toothed shrews (Crocidura spp.) form a new phylogroup of Herpetosoma, unrelated to flagellates previously detected in insectivores. With 13 documented species, Ethiopia was the richest region for trypanosome diversity, which corresponds to the very diverse environments and generally high biodiversity of this country. We conclude that besides T. lewisi, the subgenus Herpetosoma is highly host-specific (e.g., species parasitizing the rodent genera Acomys and Gerbilliscus). Furthermore, several newly detected trypanosome species are specific to their endemic hosts, such as brush-furred mice (Lophuromys), dormice (Graphiurus), and white-toothed shrews (Crocidura).

Knowledge gaps in invasive species infections: Alien mammals of European Union concern as a case study

Invasive Alien Species (IAS), i.e. species introduced by humans outside their natural geographic range, may act as host or vectors of pathogens of both human and animal health relevance. Although it has been recognized that IAS should deserve more attention from a public and animal health perspective, data on the pathogens hosted by these species are not systematically collected and this prevents accurate assessments of IAS-specific risks of disease transmission.To support the future development of disease risk assessments, we systematically reviewed the scientific literature related to the pathogens of the eleven mammal species included in the European list of IAS of concern to gain insight in the amount and quality of data available. Data were analyzed to assess the current knowledge on the pathogens harbored by mammal IAS in natural conditions, through the identification of the main factors associated with research intensity on IAS pathogens and with the IAS observed pathogen species richness, the estimation of the true pathogen species richness for each IAS, and a meta-analysis of prevalence for the pathogens of health relevance.While the review confirmed that mammal IAS harbor pathogens of human and animal health relevance such as rabies virus, West Nile Virus, Borrelia burgdorferi and Mycobacterium bovis, results also highlighted strong information gaps and biases in research on IAS pathogens. In addition, the analyses showed an underestimation of the number of pathogens harbored by these species and the existence of high levels of uncertainty in the prevalence of the pathogens of health significance identified.These results highlight the need towards more efforts in making the available information on IAS pathogens accessible and systematically collected in order to provide data for future investigations and risk assessments, as well as the need of relying on alternative sources of information to assess IAS disease risk, like expert opinions.

A Universal Key to Rationally Select Which, Among Nonparametric Species Richness Estimators, Performs Best According to Each Particular Incomplete Sampling

Since most samplings of local species communities are bound to remain substantially incomplete for practical reasons, a wide variety of nonparametric estimators of the number of unrecorded species have been proposed over the past fifty years. Unfortunately, the distinct formulations of each of these estimators naturally lead to substantially divergent estimates. The will to try to select, in each case, the estimator expected to be the more accurate has long been carried out only on a purely empirical, even arbitrary, basis (as is evident from the extensive consultation of much of the past literature on estimating species richness of incompletely sampled communities). So that extrapolating the true species richness of a community from its incomplete survey has long remained quite unsatisfactory. Indeed, the definition of a truly rational procedure for selecting the most accurate (least-biased) estimator actually requires a solidly established theoretical framework, involving to conform, as best as possible, to the general mathematical characteristics of the Species Accumulation Function. Accordingly, unveiling, first of all, these mathematical characteristics of the Species Accumulation Function was a decisive step forward in this perspective. Thereby making it now possible to propose an objective key to rationally select the one, within the series of various estimators, which, depending on each particular sampling, happens to be the least biased in this particular case, thus providing the most accurate estimate of the number of still unrecorded species. And, consequently, making it possible, now, to deliver the best estimate of the true species richness of a local community, despite its being incompletely surveyed.

Braun Blanquet Skalasından Doğru Tür Zenginliğinin Kestirimi

Aim of study: The goal of the study was to estimate true species richness from Braun Blanquet (BB) scale data.
 Area of study: Yazılı Canyon Nature Park (YCNP) located in the Mediterranean Region of Turkey.
 Material and methods: A bias-corrected approach was adapted based on the Good-Turning frequency formula to estimate true species richness (S_est ) for 9 vegetation plots under three scenarios (Rare species are singletons: with 1/1 probability 〖(Sc〗_1), with 1/2 probability (〖Sc〗_2), with 1/3 probability 〖(Sc〗_3)).
 Main results: The results indicate that with increasing uncertainty about the number of singletons, the difference between expected species richness and observed species richness decreases. To estimate the species richness of the plots taken from YCNP, scenario III (〖Sc〗_3 ) seems to be the best option due to existing maximum uncertainty concerning the number of singletons.
 Highlights: All the proposed bias-corrected estimators have been developed by considering the abundance or the incidence-based data except for S_est. For employing S_est, all the data consists of the number of singletons (f_1 ) and super doubletons (f_(2+) ). f_1 and f_(2+) can be obtained from BB scale because its "r" code usually corresponds to f_1. However, some scientists prefer to use "r" in description of a few species. That causes an uncertainty about f_1. Using S_est, this study offers an approach and a spreadsheet program to estimate true species richness even though the number of singletons is uncertain.
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Habitats and benthic biodiversity across a tropical estuarine–marine gradient in the eastern Kimberley region of Australia

The Kimberley coast situated in north-western Australia has been recognised as one of the world’s least human-impacted coastal areas as well as being rich in wilderness and biodiversity values. However, the region is vast and patchily surveyed with many knowledge gaps remaining about the diversity and extent of marine life in nearshore habitats. The King George River, in the far north-east of the region is an area where knowledge is lacking and consequently, to fill these gaps, a multi-taxon biodiversity and habitat survey was conducted in 2014. The survey extended from the base of the King George River twin waterfalls, which mark the upstream limit of marine influence, to the mouth of the river and 15 km offshore into the Timor Sea. At least eleven habitat types were identified. These include extensive stands of mangroves, rocky shores and sandy beaches extending out through the estuary and along the coast. Offshore from the estuary, Lesueur Islet is a low, vegetated islet surrounded by a fringing coral reef that supports a diverse benthic invertebrate fauna and algal flora. Deep-water sedimentary and hard-bottom filter-feeder communities also occur between the estuary and Lesueur Islet and around it. A total of 1374 animal and plant lots were collected, comprising about 3500 specimens with 796 species recorded. There were at least nine new species discovered of which five have since been named. The new species included five crustaceans and four echinoderms. In addition, there were at least twelve new records for Australia (one cnidarian, two echinoderms, nine crustaceans and some molluscs). Eighteen new records of crustaceans were made for Western Australia. Species accumulation curve analyses suggest true species richness may be higher than observed here if greater sampling were conducted on deep hard-bottom substrates in the region. Nevertheless, these results confirm this region contains a highly diverse community of regional and national significance.

Avifaunal survey of Mengilan Forest Reserve and its surrounding areas in Pensiangan, Sabah, Malaysia

An avifaunal survey was carried out at Mengilan Forest Reserve. The MacKinnon List method was used to assess species diversity. The three-day survey recorded a total of 18 lists with 486 individuals detected. Seventy-five species from 33 families were recorded, with H=3.86 and EH=0.62. True species richness was estimated (using SuperDuplicates® online calculator) to be approximately 91 species, with approximately 16 species not detected. The seven Bornean endemics detected were: Black-crowned Pitta, Bornean Leafbird, Bornean Black Magpie, Bornean Necklaced Partridge, Dusky Munia, White-crowned Shama and Yellow-rumped Flowerpecker. Pellorneidae (jungle babblers) and Pycnonotidae (bulbuls) were the most speciose families with six species. Nectariniidae (sunbirds and spiderhunters) and Cuculidae (cuckoos) each had five species. Timaliidae had four species. Apodidae (swifts), Pycnonotidae and Cisticolidae (warblers) had the highest percentages of individuals detected with 10.7%, 9.7% and 8.4%, respectively. The five species with the highest relative abundance index were Silver-rumped Spinetail (0.084), Dusky Munia (0.058), Yellow-bellied Prinia (0.045), Blue-crowned Hanging Parrot and Green Iora (both 0.043) and the Eurasian Tree Sparrow (0.039). The majority of the species detected (68) were forest-dependent species. Of these, 55 species were strictly forest birds. Insectivores made up the most dominant dietary guild, i.e., a total of 46 species (from 21 families) with 41 species in 18 families being strict insectivores.

PRELIMINARY CHECKLIST OF FRESHWATER FISHES OF ULU PAIP ECO-PARK FOREST, KEDAH, PENINSULAR MALAYSIA

This report is the first on freshwater fishes of Ulu Paip Eco-Park Forest, Kedah, which aims to document the fish species richness in this recreational forest. All species were collected from the main stream, Sungai Karangan, and its unnamed tributaries. In total, 20 species of fishes from 10 families were recorded. Cyprinidae is the most dominant family with six species followed by Danionidae with three species. Other families contribute at least one species each. Most of the species recorded here are commonly found in the northern part of Peninsular Malaysia. Further studies should be expected to record more species and the utilization of various sampling gear such as electro fishing technique would be able to recordthe true species richness of fishes in this area.

Progressive Recovery of a Marine Gastropod Community Following Atmospheric Nuclear Tests in French- Polynesia: A Socio-ecological Interpretation

Aims: The way species-richness is accommodated and how species-abundance distribution is organized in a hierarchic pattern is central to community ecology. Yet, the process by which species-richness and species-abundances are progressively accommodated can hardly be monitored, in practice, at a sufficiently large spatial scale. Fortunately, the progressive recovery of marine communities, after their complete destruction by atmospheric nuclear tests, yet offered unique opportunity to monitor the full process of accommodation of increasing species-richness and the associated, transient development of strong interspecific competition, all along the process of recovery.
 Methods: Taking full advantage of such monitoring yet requires, first, to relevantly overcome two important practical issues: 1) achieving reliable numerical extrapolations of the usually unavoidably incomplete samplings in order to accurately estimate both the true species-richness and the completed distribution of species-abundances, including the abundance of undetected species and 2) disentangling (i) the positive contribution of improved niche-diversification to species-richness and species-abundance evenness from (ii) the negative contribution of increasing interspecific-competition, all along the recovery progress. This, indeed, is a rather tricky challenge, yet relevantly solved by using the newly developed “standardized unevenness index”, conceptually based upon MacArthur approach to interspecific-contest at niche overlaps.
 Results: Applying both tools above to the monitored recovery of a reef-associated Gastropod community, entirely wiped-out previously by severe nuclear blasts, had allowed a deeper understanding of the dynamic interplay between species-recruitment, niche-diversification and interspecific-competition in the regeneration of the community. In particular, along the recovery process, a transient, metastable phase – involving severe interspecific-competition at niche-overlaps – precedes a gradual return to dynamic stability, with the virtual extinction of interspecific competition

The value of novel ecosystems: Disclosing the ecological quality of quarry lakes

Intense sand and gravel mining has created numerous man-made lakes around the world in the past century. These small quarry lakes (1–50 ha) are usually hydrologically isolated, often deep (6–40 m) and stratify during summer and in cold winters. Due to their small size, these deep man-made lakes are usually not included in the regular monitoring campaigns, e.g. as required for the European Water Framework Directive (WFD). Therefore, not much is known about the ecological functioning of these novel ecosystems. During two summers, we determined the macrophyte diversity and measured a range of physico-chemical and biological parameters in 51 quarry lakes in the catchment area of the rivers Meuse and Rhine. We compared the results of this campaign to the chemical and macrophyte sampling as performed for the WFD in the immediate surrounding shallow standing waters. Alpha (local) and beta diversity (regional), and local contribution to beta diversity were calculated for the whole region of which beta diversity was further partitioned into a true species replacement and richness difference component. Quarry lakes contain higher water quality reflected by lower nutrient and chlorophyll-a concentration compared with shallow water bodies. Additionally, quarry lakes contribute significantly to the regional macrophyte diversity pool by harboring distinctly different macrophyte communities (beta diversity — replacement). Specifically quarry lakes with a total phosphorus concentration in the water column below 35 μg P/l contribute most to beta diversity among quarry lakes.Novel ecosystems such as deep quarry lakes are often perceived as less valuable ecosystems, with strong implications regarding their management. Our results show that quarry lakes are in general of better chemical and biological quality compared with shallow standing waters. We therefore call for a more integrated assessment of the quality of quarry lakes and corresponding management strategy of these waters by water managers.

Odonata fauna in adjoining areas of Amirthi Zoological Park in Vellore District, Tamilnadu, India

The objective of the present study is to explore the diversity of dragonflies and damselflies (Odonata) in Amirthi Forest Division, Vellore District. Dragonfly watching and recording has been done in each line transect during a week. A total of 37 species belonging to 29 genera and 6 families viz. Lestidae, Platycnemididae, Coenagrionidae (under suborder Zygoptera) and Coenagrionidae, Platycnemididae and Libellulidae (under suborder Anisozygoptera) were recorded. The maximum number of Odonates were found in Libellulidae (n=20), followed by Coenagrionidae (n=11 species), Aeshnidae (n=2 species), Lestidae (n=3 species), Platycnemididae (n=1 species) and Gomphidae (n=1 species). Out of the Site -1 Urban areas, Site -2 Agricultural areas, Site -3 wet land areas and Site - 4 Amirthi park areas are selected study sites, the highest number of Odonate species (28) was recorded in S3 and S2 ranked second with 24 species. Species richness was comparatively low in the remaining Study sites: S4 with 21 species and S1 with 18 species. The result of high species richness in the particular study sites (S3 and S2) may be due to the intensity and duration of longer surveys, rather than true ecological species richness. Among the selected Sites the diversity of dragonflies was high in Agricultural areas and wet land areas. Out of the 37 Odonates recorded from the district, 35 species come under the IUCN Red List of Threatened Category. Among them 37 species comes under Least Concern (LC) Category, one species under Data Deficient (DD) and three species is not evaluated. The present study is to encourages the wide range conservation of dragonfly species in the study area.

How steady is the nested pattern in saline grassland true bug communities? Effects of sampling effort and data completeness on nestedness

Nestedness is currently one of the most explored structural patterns of biological communities, especially since its major application in studies on ecological networks. Research on the nested pattern, as a spatial structural descriptor of communities, was mostly focused on theoretical background in the conservation of habitat islands. Here, we explore, to what extent nested true bug communities are present in saline grassland fragments of the Pannonian ecoregion and what are the reasons for their nestedness. In 2015 and 2017, we sampled true bugs from 17 saline pastures in northern Serbia. We applied three different sampling procedures (i.e. gradient in sampling effort) for collecting true bugs: along 20 m long transect, 3 × 30 m long parallel transects and total inventory. Analyses showed significant nestedness of the true bug communities and consistency of the pattern regardless of the data type (binary vs. weighted data) and applied metrics (NODF vs. spectral radius, WNODF vs. spectral radius). However, with the decrease of sampling effort and/or the exclusion of grass feeders, all metrics gradually detect less frequently significant nestedness. The only constant factor which was found to induce nestedness in true bug communities was true bug species richness. Plant cover features showed a weak influence on the nested pattern and landscape features did not take part at all. We believe nestedness of true bugs was the result of differences in habitat complexity among sampling sites, but detailed studies are needed to reveal which abiotic and/or biotic factors are responsible for it. For further studies, priority should be given to investigating the influence of management of saline grasslands on the nestedness in true bug communities.

Tuning parameter selection for a penalized estimator of species richness

Our goal is to estimate the true number of classes in a population, called the species richness. We consider the case where multiple frequency count tables have been collected from a homogeneous population and investigate a penalized maximum likelihood estimator under a negative binomial model. Because high probabilities of unobserved classes increase the variance of species richness estimates, our method penalizes the probability of a class being unobserved. Tuning the penalization parameter is challenging because the true species richness is never known, and so we propose and validate four novel methods for tuning the penalization parameter. We illustrate and contrast the performance of the proposed methods by estimating the strain-level microbial diversity of Lake Champlain over three consecutive years, and global human host-associated species-level microbial richness.

A review of the African snake-eyed skinks (Scincidae: Panaspis) from Angola, with the description of a new species.

The genus Panaspis in Angola is represented by four species, most of them part of taxonomically and nomenclaturally challenging species-complexes. We present a taxonomic revision of the group in the region and describe one new species, Panaspis mocamedensis sp. nov., endemic to the lowland areas of the Namibe province, southwestern Angola. Phylogenetic analysis using a combination of mitochondrial (16S, cytb) and nucleares (RAG1, PDC) markers, as well as morphological and meristic data support the recognition of the new species. In addition, these data support the presence of nominotypical Panaspis cabindae, P. wahlbergi and P. maculicollis in Angola. Reexamination of the Angolan population of P. breviceps was based on morphological analysis, as no molecular data from Angola is available for this species. According to our results, this population likely represents the nominotypical form, but due to its complex taxonomic and nomenclatural history and the lack of molecular data, this population needs to be reconsidered when molecular data become available. The description of a new species and revision of the Angolan Panaspis contributes to a better understanding of the true species richness of the Angolan herpetofauna, as well as to understanding the major biogeographic patterns of the region. A key to Angolan Panaspis species is also presented.

Inferring True Species Richness and Complete Abundance Distribution in Six Reef-fish Communities from Red-sea, Using the Numerical Extrapolation of Incomplete Samplings

Even when ecological communities are incompletely sampled (which is most frequent in practice, at least for species-rich assemblages including many rare species), it remains possible to retrieve much more information than could be expected first, by applying numerical extrapolation to incomplete field data. Indeed, recently developed procedures of numerical extrapolation of partial samplings now allow to estimate, with fair accuracy, not only the number of the still unrecorded species but, moreover, the distribution of abundances of each of these unrecorded species, thereby making available the full range of the Species Abundance Distribution, despite dealing with incomplete data only. In turn, this allows to address a series of descriptive and functional aspects of the internal organization of species assemblages, which otherwise would have required disposing of truly exhaustive samplings.
 This approach is applied, here, to the previously reported partial samplings of six neighboring reef-fish communities from Tiran Island, Red Sea, with the goal of better understanding their internal organization in relation to their respective environments.
 In practice, the numerical completion contributes to avoid erroneous interpretations that would likely stem from considering only the incomplete field data. This point is especially relevant when studying reef-associated communities because accurate understanding of their organization will help guiding and refining at best the protective measures required by these particularly vulnerable communities.

Evaluating the distribution of freshwater fish diversity using a multispecies habitat suitability model to assess impacts of proposed dam development in Gabon, Africa

AbstractData scarcity impedes a comprehensive impact assessment of the 38 dams currently proposed within the highly biodiverse central African nation of Gabon. Here, we present a multiple‐species MaxEnt distribution modeling approach to assess species richness for freshwater fishes at the landscape level and demonstrate its utility in identifying proposed dam sites in Gabon that fall in highly diverse areas. We modeled habitat suitability for 202 of Gabon's fresh and brackish water fish species based on georeferenced presence data from museum specimens and a set of ecologically meaningful environmental conditions. We removed poor performing species from the model and compiled the distributions of 114 well‐performing species to generate a new metric, the species pseudorichness index (pR), defined as the cumulative number of species that are highly suited to the habitat in a given segment of river. We used pR as a proxy for true species richness and use this metric to evaluate the distribution of freshwater fish diversity relative to the proposed dam development in Gabon. We found that more than 80% of the proposed dams in Gabon overlap with areas of high pR, implying that planned hydroelectric development in Gabon may disproportionately affect high diversity areas. These dams deserve more focused baseline assessments and conservation action. This approach provides a rapid way to initiate a landscape‐scale assessment of freshwater fish diversity to inform conservation decisions in areas that are species rich, but data poor.

Variations in Total Species Richness and the Unevenness of Species Abundance Distribution between Two Distant Conus Communities (Neogastropoda): A Case Study in Mannar Gulf (India)

The genus Conus forms a conspicuous and rather homogeneous group within marine Gastropods. This makes it all the more interesting to focus on the sub-communities formed by Conus species and to analyze the potential specificities in the internal organization of species in these communities, in particular species richness, species abundance distribution and the effect of geographical distance between communities on differences in their respective species composition. Accordingly, two Conus communities along the coast in Mannar Gulf (India), separated by 80 km, are considered. Reliable analysis requires, first, to treat exhaustive data from complete samplings or, else – as here – to implement an appropriate extrapolation procedure to complete numerically the partial samplings. After numerical completion, substantial differences were highlighted between the two communities, not only in terms of true (total) species richness but, even more, as regards the profile and the average unevenness of the distributions of species abundance. Also, significant dissimilarity in species composition was found between the two communities, that may be tentatively attributed to either deterministic distance decay in similarity of species composition or, alternatively, to the persistence in the stochastic process of species recruitment from the regional stock of Conus planktonic larvae. This preliminary study yet requests to be complemented by other similar case studies, before drawing any safer interpretative conclusions.