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Infaunal Benthic Communities from the Inner Shelf off Southwestern Africa Are Characterised by Generalist Species.

Steffani N, Sedick S, Rogers J, Gibbons MJ - PLoS ONE (2015)

Bottom Line: Although the fauna was dominated by polychaetes and peracarid crustaceans, patterns in community structure could only weakly be explained by the measured environment (~35%).This is attributed to the generalist nature of the species recovered, which were widely distributed amongst different sediments, water-depths and latitudes.The fauna is dominated by species that enjoy a widespread regional and global distribution and is characterised by relatively low diversity, which is discussed.

View Article: PubMed Central - PubMed

Affiliation: 21 Skippers End, Zeekoevlei, Cape Town, South Africa.

ABSTRACT
Infaunal communities of benthic macro-organisms (≥ 1mm length) were studied from 81 samples collected across nine sites to the north and south of the Orange River in the Benguela upwelling ecosystem in 2003, with a view to describing communities and understanding the drivers of regional community structure, as well as to document diversity and to examine geographic affinities. Although the fauna was dominated by polychaetes and peracarid crustaceans, patterns in community structure could only weakly be explained by the measured environment (~35%). This is attributed to the generalist nature of the species recovered, which were widely distributed amongst different sediments, water-depths and latitudes. The fauna is dominated by species that enjoy a widespread regional and global distribution and is characterised by relatively low diversity, which is discussed.

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Related in: MedlinePlus

Two-dimensional visualisations of faunal communities.(A) MDS plot of the similarity in the species composition of macrofaunal (> 1mm length) samples collected off southern Namibia and off Namaqualand during 2003. (B) Multivariate multiple regression dbRDA performed on the macrofaunal species composition of samples collected off southern Namibia and off Namaqualand during 2003, and environmental predictors: vectors show the direction and strength of the environmental gradients. The location of the samples, by site, is indicated by symbols.
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pone.0143637.g003: Two-dimensional visualisations of faunal communities.(A) MDS plot of the similarity in the species composition of macrofaunal (> 1mm length) samples collected off southern Namibia and off Namaqualand during 2003. (B) Multivariate multiple regression dbRDA performed on the macrofaunal species composition of samples collected off southern Namibia and off Namaqualand during 2003, and environmental predictors: vectors show the direction and strength of the environmental gradients. The location of the samples, by site, is indicated by symbols.

Mentions: Samples from the shallower mid-shelf sites group to the right of the MDS plot (Fig 3A), whilst those from the deeper sites can be seen to the left. In general, samples from the same site tend to group fairly close together. Patterns were clearer when the data were analysed separately by identified species (stress value = 0.18), than by genus (0.19) or family (0.22), although there was a high level of concordance between the similarity matrices, as determined by the relate statistic (species-genus R = 0.932, species-family R = 0.859, genus-family R = 0.933). The results of the marginal DistLM tests on the identified species-level data indicate that all but one (% gravel) of the predictor variables had a significant impact on the structure of the communities (with water-depth, latitude/site and distance from the Orange River being most important, followed by mud and sand content respectively). And though the overall model included all variables, it could only explain 42.2% of the pattern (Table 4). This is shown graphically in the dbRDA plot (Fig 3B), the first two (of eight) axes of which explain ~67% of fitted variation and ~33% of total variation, and separate samples by water-depth (dbRDA1) and latitude/site (dbRDA2). Essentially similar patterns are shown whether the data are analysed by genus (DistLM adj R2 = 0.42: data not shown) or family (DistLM adj R2 = 0.40: data not shown). Interestingly, there appears to be less variability between samples within sites, from the deeper than shallower areas.


Infaunal Benthic Communities from the Inner Shelf off Southwestern Africa Are Characterised by Generalist Species.

Steffani N, Sedick S, Rogers J, Gibbons MJ - PLoS ONE (2015)

Two-dimensional visualisations of faunal communities.(A) MDS plot of the similarity in the species composition of macrofaunal (> 1mm length) samples collected off southern Namibia and off Namaqualand during 2003. (B) Multivariate multiple regression dbRDA performed on the macrofaunal species composition of samples collected off southern Namibia and off Namaqualand during 2003, and environmental predictors: vectors show the direction and strength of the environmental gradients. The location of the samples, by site, is indicated by symbols.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664413&req=5

pone.0143637.g003: Two-dimensional visualisations of faunal communities.(A) MDS plot of the similarity in the species composition of macrofaunal (> 1mm length) samples collected off southern Namibia and off Namaqualand during 2003. (B) Multivariate multiple regression dbRDA performed on the macrofaunal species composition of samples collected off southern Namibia and off Namaqualand during 2003, and environmental predictors: vectors show the direction and strength of the environmental gradients. The location of the samples, by site, is indicated by symbols.
Mentions: Samples from the shallower mid-shelf sites group to the right of the MDS plot (Fig 3A), whilst those from the deeper sites can be seen to the left. In general, samples from the same site tend to group fairly close together. Patterns were clearer when the data were analysed separately by identified species (stress value = 0.18), than by genus (0.19) or family (0.22), although there was a high level of concordance between the similarity matrices, as determined by the relate statistic (species-genus R = 0.932, species-family R = 0.859, genus-family R = 0.933). The results of the marginal DistLM tests on the identified species-level data indicate that all but one (% gravel) of the predictor variables had a significant impact on the structure of the communities (with water-depth, latitude/site and distance from the Orange River being most important, followed by mud and sand content respectively). And though the overall model included all variables, it could only explain 42.2% of the pattern (Table 4). This is shown graphically in the dbRDA plot (Fig 3B), the first two (of eight) axes of which explain ~67% of fitted variation and ~33% of total variation, and separate samples by water-depth (dbRDA1) and latitude/site (dbRDA2). Essentially similar patterns are shown whether the data are analysed by genus (DistLM adj R2 = 0.42: data not shown) or family (DistLM adj R2 = 0.40: data not shown). Interestingly, there appears to be less variability between samples within sites, from the deeper than shallower areas.

Bottom Line: Although the fauna was dominated by polychaetes and peracarid crustaceans, patterns in community structure could only weakly be explained by the measured environment (~35%).This is attributed to the generalist nature of the species recovered, which were widely distributed amongst different sediments, water-depths and latitudes.The fauna is dominated by species that enjoy a widespread regional and global distribution and is characterised by relatively low diversity, which is discussed.

View Article: PubMed Central - PubMed

Affiliation: 21 Skippers End, Zeekoevlei, Cape Town, South Africa.

ABSTRACT
Infaunal communities of benthic macro-organisms (≥ 1mm length) were studied from 81 samples collected across nine sites to the north and south of the Orange River in the Benguela upwelling ecosystem in 2003, with a view to describing communities and understanding the drivers of regional community structure, as well as to document diversity and to examine geographic affinities. Although the fauna was dominated by polychaetes and peracarid crustaceans, patterns in community structure could only weakly be explained by the measured environment (~35%). This is attributed to the generalist nature of the species recovered, which were widely distributed amongst different sediments, water-depths and latitudes. The fauna is dominated by species that enjoy a widespread regional and global distribution and is characterised by relatively low diversity, which is discussed.

Show MeSH
Related in: MedlinePlus