Extrapolation of Total Species Richness from Incomplete Inventories: Application to the Gastropod Fauna Associated to Coral Reefs in ‘Mannar Gulf Biosphere Reserve’, India

2018

AIR

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The total number of co-occurring species ("true species richness") and the way their respective abundances are distributed ("species abundance distribution") are two major descriptive traits of species assemblages, in numerical terms. Moreover, beyond mere description, the species abundance distribution may help to infer how ecological factors/constraints are currently shaping the hierarchical structure of species assemblages and thereby, may contribute to shed light upon general traits regarding the functional organisation within communities of species. Unfortunately, both total species richness and exhaustive abundance distributions are not available when dealing with more or less incomplete species inventories, a situation which becomes increasingly frequent with the generalisation of the so-called "quick surveys" and "rapid biodiversity assessments", which are almost unavoidable when addressing very species-rich assemblages, such as, for example, invertebrate communities. Hence, the necessity of extrapolating with minimum bias (i) the species accumulation curve, thereby deriving reliable estimates of the total species richness of sampled assemblage and (ii) the species abundance distribution to get an exhaustive pattern including the Method Article

mentioning

confidence: 81%

How to Extrapolate Species Abundance Distributions with Minimum Bias When Dealing with Incomplete Species Inventories

2018

AIR

Self Cite

“…The three communities have rather similar estimated total species richness: 'Koswari': 53 species, 'Vaan': 51 species, 'Hare' 49 species (Table 1, [16]). In this respect, the spatial distance between communities does not seem to have any influence: the (slight) difference of species richness is the same between 'Hare' (49 species) and 'Vaan' (51 species), separated by > 100 km, than between 'Koswari' (53 species) and 'Vaan' (51 species), although distant by 3 km only.…”

Section: Estimated Total Species Richness Of Each Communitymentioning

confidence: 94%

“…Moreover, the expected additional sampling effort that would be required to progressively unveil the taxonomical identities of the still unrecorded species is provided by the numerically extrapolated Species Accumulation Curve of each community, as already reported in [16].…”

Section: Total Species Richness and Abundance Distributionmentioning

confidence: 98%

“…Hereafter, I report and discuss the results derived from the numerical extrapolations applied to the partial inventories of three marine Gastropod communities associated to tropical coral reefs surrounding three small islands within Mannar Gulf Biosphere Reserve (south-eastern coast of India). Partial samplings were carried out by Mohanraj and co-workers [15], while the estimates of the true (total) species richness of each of these three communities were already reported by Béguinot [16].…”

Section: Introductionmentioning

confidence: 99%

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The Full Hierarchical Structuration of Species Abundances Reliably Inferred from the Numerical Extrapolation of Still Partial Samplings: A Case Study with Marine Snail Communities in Mannar Gulf (India)

2018

AJEE

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The detailed analysis of Species Abundance Distributions ("S.A.D.s") can shed light on how member-species organize themselves within communities, provided that the complete distribution of species abundances is made available first. In this perspective, the numerical extrapolation applied to incomplete "S.A.D." can effectively compensate for S.A.D.s incompleteness, when having to deal with substantially incomplete samplings. Indeed, almost as much information can be released from extrapolated "S.A.D.s" as would be obtained from truly complete "S.A.D.s", although the taxonomic identities of unrecorded species remain of course ignored by numerical extrapolation. To take full advantage of this new approach, a recently developed procedure allowing the leastbiased numerical extrapolation of "S.A.D.s" has been applied to three partially sampled gastropods communities associated to coral-reef in Mannar Gulf (S-E India). The following main results were derived from the three numerically completed "S.A.D.s": (i) once AJEE, 7(3): 1-27, 2018; Article no.AJEE.43918 2 completed, all three numerically "S.A.D.s" fairly well comply with the log-normal model, suggesting that, in all three communities, the process of hierarchical structuration of species abundances likely involves the combined contributions of many independent factors; (ii) moreover, the same holds true for each of the two coexisting feeding guilds (primary and secondary consumers) considered separately; (iii) when compared to secondary consumers, the guild of primary consumers has a much lower species richness but, on the other hand, exhibits a more strongly structured distribution of species abundances, which materializes not only in term of the apparent unevenness of species abundances but also after having disentangled the genuine intensity of the underlying process driving the hierarchical structuration. All the preceding features are shared in common by the three communities studied, in line with the similarity of their environmental contexts. Only minor features can actually slightly distinguish between communities, reflecting the difference in distances between them. Original Research Article

“…Partial samplings of three Gastropod communities associated to coral-reefs surrounding small islands in Mannar Gulf were numerically extrapolated for evaluation of total species richness S t [27] and, then, numerically extrapolated to infer the complete Species Abundance Distribution (BÉGUINOT unpublished). Derived from this inference, the degree U of abundance unevenness and the intensity I str of the structuring process are plotted against the species richness S t in Fig.…”

Section: Gastropod Communities Associated To Coral Reefs In Mannar Gumentioning

confidence: 99%

The Hierarchical Structuring of Species Abundances within Communities: Disentangling the Intensity of the Underlying Structuring Process behind the Apparent Unevenness Pattern

2018

AIR

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Besides species richness, the hierarchical structuration of species abundances is the second major characteristic that numerically specifies a community of species. However, while the meaning of species richness is simple and straightforward, the hierarchical structuration of abundances is a less simple concept, where the pattern-i.e. the straightforwardly observed level of unevenness of species abundance distribution-does not reliably mirror the genuine intensity of the structuring process itself. This is because the level of unevenness is also mathematically dependent upon species richness. Accordingly, when specifying numerically a community of species, I advocate not to be satisfied, as usual, by considering only the total species richness and the degree of unevenness (whatever the expression chosen to quantify unevenness). A third parameter should be further considered: the genuine intensity of the structuring process itself, defined freed from the purely mathematical influence of species richness and, thereby, accurately reflecting the functional contribution to the hierarchical structuration of species abundances. The level of unevenness is thus Method Article