scholarly journals 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)

2019 ◽  
pp. 1-18
Author(s):  
Jean Béguinot
Keyword(s):  
Species Richness ◽  
Species Composition ◽  
Species Abundance ◽  
Species Abundance Distribution ◽  
Abundance Distribution ◽  
Marine Gastropods ◽  
Total Species Richness ◽  
Species Recruitment ◽  
Total Species

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.

scholarly journals An Algebraic Derivation of Chao’s Estimator of the Number of Species in a Community Highlights the Condition Allowing Chao to Deliver Centered Estimates

2014 ◽  
Vol 2014 ◽  
pp. 1-6
Author(s):  
Jean Béguinot
Keyword(s):  
Species Richness ◽  
Lower Bound ◽  
Species Abundance ◽  
Nonparametric Estimator ◽  
Species Abundance Distribution ◽  
Abundance Distribution ◽  
Limited Size ◽  
Total Species Richness ◽  
Log Normal ◽  
Total Species

Anne Chao proposed a very popular, nonparametric estimator of the species richness of a community, on the basis of a limited size sampling of this community. This expression was originally derived on a statistical basis as a lower-bound estimate of the number of missing species in the sample and provides accordingly a minimal threshold for the estimation of the total species richness of the community. Hereafter, we propose an alternative, algebraic derivation of Chao’s estimator, demonstrating thereby that Chao’s formulation may also provide centered estimates (and not only a lower bound threshold), provided that the sampled communities satisfy a specific type of SAD (species abundance distribution). This particular SAD corresponds to the case when the number of unrecorded species in the sample tends to decrease exponentially with increasing sampling size. It turns out that the shape of this “ideal” SAD often conforms approximately to the usually recorded types in nature, such as “log-normal” or “broken-stick.”. Accordingly, this may explain why Chao’s formulation is generally recognized as a particularly satisfying nonparametric estimator.

Species richness in the Phanerozoic: an investigation of sampling effects

Paleobiology ◽  
1978 ◽  
Vol 4 (4) ◽  
pp. 394-406 ◽  
Author(s):  
Philip W. Signor
Keyword(s):  
Species Richness ◽  
Species Abundance ◽  
Strongly Correlated ◽  
Species Abundance Distribution ◽  
Sediment Volume ◽  
Total Species Richness ◽  
Cenozoic Sediments ◽  
The Impact ◽  
The Relationship ◽  
Total Species

Given estimates of the variation in total standing species richness through the periods of the Phanerozoic, mean species duration, and the relative intensity of the sampling of the fauna from each of the periods, the expected number of described species can be predicted for each period of the Phanerozoic using an analytic sampling model. This model is based on the assumption that the relative abundances of species in any geologic period can be approximated by the canonical (lognormal) species-abundance distribution.Three commonly cited models of standing species richness (Valentine, 1973; Gould et al., 1977; Bambach, 1977) each suggest different patterns of species richness in the Phanerozoic. By assuming that sampling of the fossil record is proportionate to sediment volume, it can be shown with the sampling model that the Empirical, Equilibrium, and Species-Richness Models each predict that the number of described species will be strongly correlated with sediment volume. Equally high correlations are predicted if it is assumed that sampling is proportionate to sediment area or to paleontological interest. The correlations predicted for each of the three models are remarkably similar. The impact of sampling effects is so strong that the variations in species richness postulated by these three models are almost completely obscured. Preservational biases will probably only further obscure the relationship between the number of described species and total species richness. Therefore, it seems likely that analysis of trends in the total number of described species will be of little use in determining trends in worldwide species richness in the Phanerozoic.Comparison of the actual patterns of variation in the number of described species and the expected numbers of described species predicted by the sampling model reveals that more species are known from the Cenozoic than would be predicted from the abundance of Cenozoic sediments or from the amount of paleontological interest in the Cenozoic. This might have resulted from the Cenozoic sediments remaining relatively free of diagenetic effects which might have destroyed the fossils entombed in the sediments.

Post-fire succession during the long-term absence of fire in coastal heathland and a test of the chronosequence survey method

2015 ◽  
Vol 63 (7) ◽  
pp. 572 ◽  
Author(s):  
Marc Freestone ◽  
Timothy J. Wills ◽  
Jennifer Read
Keyword(s):  
Species Richness ◽  
Fire History ◽  
Species Abundance ◽  
Tree Cover ◽  
Survey Method ◽  
Total Species Richness ◽  
Historical Factor ◽  
Declining Species ◽  
Total Species

Post-fire vegetation succession in long-unburnt heathland in south-east Australia is not well understood. In the present study we investigated temporal change in vegetation along a 37-year post-fire chronosequence in coastal heathland in the Gippsland Lakes Coastal Park, Victoria, Australia. Fourteen sites were surveyed for vegetation characteristics approximately 10 years after an initial chronosequence survey, enabling an extension of the chronosequence to cover a longer fire-free interval as well as testing predictions of declining species richness and diversity from the initial chronosequence study. Total species richness, mean species richness, mean diversity and mean evenness declined with time since fire across the 14 sites. However, only diversity (H) and evenness (E) decreased within sites as predicted in the original chronosequence study. No decrease in species richness within sites was observed. The chronosequence correctly predicted changes in species abundance but not the number of species present. Tree cover also increased, suggesting that the heathland was becoming a woodland in the long-term absence of fire. Fire history, which is an uncontrolled historical factor, provides the most likely explanation for why species richness did not decrease as predicted by the initial chronosequence. This study advocates caution in using the chronosequence method to predict species richness during post-fire succession.

scholarly journals Species richness and interacting factors control invasibility of a marine community

2015 ◽  
Vol 282 (1812) ◽  
pp. 20150439 ◽  
Author(s):  
M. L. Marraffini ◽  
J. B. Geller
Keyword(s):  
Species Richness ◽  
Native Species ◽  
Biotic Resistance ◽  
Marine Species ◽  
Indigenous Species ◽  
Total Species Richness ◽  
Species Recruitment ◽  
Non Indigenous Species ◽  
Total Species

Anthropogenic vectors have moved marine species around the world leading to increased invasions and expanded species' ranges. The biotic resistance hypothesis of Elton (in The ecology of invasions by animals and plants , 1958) predicts that more diverse communities should have greater resistance to invasions, but experiments have been equivocal. We hypothesized that species richness interacts with other factors to determine experimental outcomes. We manipulated species richness, species composition (native and introduced) and availability of bare space in invertebrate assemblages in a marina in Monterey, CA. Increased species richness significantly interacted with both initial cover of native species and of all organisms to collectively decrease recruitment. Although native species decreased recruitment, introduced species had a similar effect, and we concluded that biotic resistance is conferred by total species richness. We suggest that contradictory conclusions in previous studies about the role of diversity in regulating invasions reflect uncontrolled variables in those experiments that modified the effect of species richness. Our results suggest that patches of low diversity and abundance may facilitate invasions, and that such patches, once colonized by non-indigenous species, can resist both native and non-indigenous species recruitment.

scholarly journals Assemblages of drosophilids (Diptera, Drosophilidae) in mangrove forests: community ecology and species diversity

2010 ◽  
Vol 100 (2) ◽  
pp. 133-140 ◽  
Author(s):  
Hermes J. Schmitz ◽  
Paulo R. P. Hofmann ◽  
Vera L. S. Valente
Keyword(s):  
Species Richness ◽  
Species Composition ◽  
Species Abundance ◽  
Mangrove Forests ◽  
Species Abundance Distribution ◽  
Conservation Areas ◽  
Apparent Lack ◽  
Breeding Sites ◽  
Richness Estimators ◽  
Harsh Conditions

Brazilian fauna of drosophilids has been researched in various ecosystems, but those in mangrove forests remain overlooked in Brazil and elsewhere. The present study attempts to characterise the assemblages of drosophilids of this environment, based on 28 collections taken in three mangrove areas in Santa Catarina Island, southern Brazil. The three mangroves surveyed were different in their surroundings, which varied from highly urbanised areas to conservation areas with natural vegetation. Overall, 69 species were collected, and no remarkable difference was detected in species composition and abundances or in the richness, evenness and heterogeneity between sites. The species abundance distribution observed fitted to a theoretical lognormal distribution in the three mangroves. The species richness scored and the performance of the species richness estimators showed an unexpectedly high diversity, considering the very low floristic diversity and the harsh conditions of the environment. Regarding species composition and abundances, the drosophilid mangrove assemblages were shown to be more similar to those found in open environments, with a marked dominance of exotic species. Finally, considering the apparent lack of feeding and breeding sites, we suggest that mangrove forests are acting as sink habitats for the drosophilids populations.

Diversity, abundance and distribution of grasshopper species (Orthoptera: Acrididea) in three different types of vegetation with different levels of anthropogenic disturbances in the Littoral Region of Cameroon

2020 ◽  
Vol 14 (1) ◽  
pp. 16-33 ◽  
Author(s):  
YETCHOM-FONDJO JEANNE AGRIPPINE ◽  
KEKEUNOU - SÉVILOR ◽  
KENNE - MARTIN ◽  
MISSOUP ALAIN DIDIER ◽  
SHENG-QUAN XU
Keyword(s):  
Species Richness ◽  
Species Abundance ◽  
Anthropogenic Disturbances ◽  
Species Abundance Distribution ◽  
Abundance Distribution ◽  
Distribution Models ◽  
Eyprepocnemis Plorans ◽  
Grasshopper Species ◽  
Littoral Region ◽  
Abundance And Distribution

Grasshoppers have been identified as excellent monitors of landscape use. Despite their importance, their composition and distribution in the highly disturbed Littoral Cameroon is still unknown. The aim of this study was to determine the effect of human activities on diversity, abundance and distribution of grasshopper species in the Littoral region of Cameron. We investigated three types of vegetation differing remarkably on the level of anthropogenic impact (farmlands, fallows and forests), using sweep netting. The eight non-parametric estimators for specific richness, abundance, α and β diversity indices and species abundance distribution models, were used to compare the structure of communities among vegetation. Overall, 38 species belonging to three families and ten subfamilies were recorded. The Acrididae was the most diverse family. The species richness, abundance and diversity were higher in farmlands than in fallows and in forests. Five species occurred exclusively in farmlands, one in fallows and four in forests. Eyprepocnemis plorans, Coryphosima stenoptera, Serpusia opacula were overall the most abundant species respectively in cultivated farms, fallows and forests. Species abundance distribution fitted the Motomura model in all sites. Serpusia opacula is considered as a useful indicator since its presence and abundance significantly depend on the rate of forest naturalness. The farmlands were characterized by short vegetation while the fallows and forests were dominated by tall grasses and tall trees respectively. Anthropogenic disturbances promote the species richness, diversity and abundance of open meadow species, while it is detrimental to forest species which are sensitive, specialized and have limited dispersal abilities. Key words: Grasshopper, diversity, abundance, distribution, bioindicator

Rarefaction and rarefiction—the use and abuse of a method in paleoecology

Paleobiology ◽  
1979 ◽  
Vol 5 (4) ◽  
pp. 423-434 ◽  
Author(s):  
John C. Tipper
Keyword(s):  
Species Richness ◽  
Species Abundance ◽  
Species Abundance Distribution ◽  
Abundance Distribution ◽  
Rarefaction Curve ◽  
Rarefaction Curves ◽  
Species Abundance Distributions

Rarefaction is a method for comparing community diversities that has consistently been abused by paleoecologists: here its assumptions are clarified and advice given on its application. Rarefaction should be restricted to comparison of collections from communities that are taxonomically similar and from similar habitats: the collections should have been obtained by using standardised procedures. The rarefaction curve is a graph of the estimated species richness of sub-samples drawn from a collection, plotted against the size of sub-sample: it is a deterministic transform of the collection's species-abundance distribution. Although rarefaction curves can be compared statistically, it may be more efficient to compare the species-abundance distributions directly. Both types of comparison are discussed in detail.

scholarly journals Family Cruciferae Juss. (Brassicaceae Burnett) of SAKHA (Yakutia) Republic

VAVILOVIA ◽  
2020 ◽  
Vol 2 (4) ◽  
pp. 3-34
Author(s):  
V. I. Dorofeyev
Keyword(s):  
Species Richness ◽  
Species Composition ◽  
Geographical Distribution ◽  
Endemic Species ◽  
Taxonomic Composition ◽  
The Arctic ◽  
New Combinations ◽  
Total Species Richness ◽  
Total Species ◽  
Cruciferae Family

The paper offers a new revision of the species composition of the Cruciferae family in Yakutia, which is supplemented by information on the geographical distribution and taxonomic composition. In the present work, the crucifers of Yakutia are represented by 39 genera and 102 species. Among them, there are two endemic species (Boechera falcata (Turcz.) Al-Shehbaz and Smelowskia jacutica (Botsch. et Karav.) Al-Shehbaz et Warwick), and one subendemic (Isatis jacutensis (N. Busch) N. Busch). Traditionally, the genus Draba is the richest in the number of species in the territories reaching into the Arctic. At present, taking the latest processing of the genus by V. V. Petrovsky (Petrovsky, 2018) into account, it numbers 32 species, which amounts to about 1/3 of the total species richness of this family in Yakutia. The paper summarizes the nomenclature changes that have affected a number of representatives of this family in recent years, and proposes new combinations in the genus Boechera (B. pendula (L.) V. I. Dorof. Comb. Nov.) and Thellungiella (T. bursifolia (DC.) V. I. Dorof. Comb. Nov.). An analysis of the diversity of crucifers made it possible to assert that the flora of Yakutia is obviously insufficiently studied in its northwest and northeast reaches, and to suggest that the floristic zoning of Yakutia should be supplemented by outlining three supra-regions, namely the Verkhoyansk (eastern), Vilui (western) and Arctic (northern) supra-regions.

scholarly journals Influence of Coral Architecture on Species Richness and the Hierarchical Structuration of Species Abundances in Reef Fish Communities: A Case Study in the Eastern Tropical Pacific

2019 ◽  
pp. 1-21
Author(s):  
Jean Béguinot
Keyword(s):  
Species Richness ◽  
Fish Community ◽  
Fish Communities ◽  
Total Species Richness ◽  
Species Abundances ◽  
Hierarchical Structuring ◽  
Complex Architecture ◽  
Total Species

The role of coral reef architecture on species richness and the internal structuration of the associated fish communities has already been addressed several times. The reported results, however, usually remain controversial, possibly because they are based upon incomplete field data issued from partial inventories. Indeed, incomplete samplings are almost unavoidable in practice with such species-rich communities having very uneven distribution of abundances. In this context, the numerical extrapolation of incompletely sampled communities may serve as a reliable surrogate. Accordingly, numerical extrapolations were implemented, here, to compare two fish-communities respectively associated to coral reefs that sharply differ from each-other by their topographic architectures. Both a higher total species richness and a sharper unevenness of species abundances were found to characterize the fish community associated to the more tormented reef habitat exhibiting the more complex architecture. Yet, paradoxically, the true intensity of the underlying process of hierarchical structuring of abundances proves being insensitive to the architecture of coral habitats. This apparent opposition between the unevenness pattern and the underlying structuring process results, in fact, from the additional negative dependence of abundance unevenness upon species richness.

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