Biogeographic patterns in rocky intertidal communities in KwaZulu-Natal, South Africa

Sink, Kerry; Branch, G. M.; Harris, Julie M.

doi:10.2989/18142320509504070

Cited by 63 publications

(41 citation statements)

References 7 publications

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“…This steepening of the already strong temperature gradient in the northern portion of the ECTZ supports the conclusion of that it represents the transition from a tropical Indian Ocean seaweed flora in Mozambique to a temperate flora in the south. A similar pattern exists for the rocky intertidal biota in the region (Sink et al, 2005). The temperature of the coldest month of the year sufficiently accounts for the environmental gradient in all bioregions, except for in the BMP.…”

Section: Discussionsupporting

confidence: 57%

Seaweeds in Two Oceans: Beta-Diversity

Smit

Bolton

2017

Front. Mar. Sci.

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Several species assembly mechanisms have been proposed to structure ecological communities. We assess the biogeography of seaweeds along 2,900 km of South Africa's coastline in relation to a thermal gradient produced by the Agulhas Current, and contrast this with the environmental structure created by the Benguela Current. We subdivided the coastline into "bioregions" to examine the regional patterning. To investigate the assembly mechanisms, we decomposed Sørensen's β-diversity into "turnover" (β sim ) and "nestedness-resultant" (β sne ) dissimilarities, and used distance-based redundancy analysis (db-RDA) to relate them to the Euclidean thermal difference, d E , and geographical distance. Moran's eigenvector maps (MEM) were used as an additional set of spatial constraints. Variation partitioning was then used to find the relative strengths of thermal and spatially-structured thermal drivers. Spatial and environmental predictors explained 97.9% of the total variation in β sim and the thermal gradient accounted for 84.2% of this combined pool. β sim was the major component of overall β-diversity in the Agulhas Current region, suggesting niche influences (environmental sorting) as dominant assembly process there. The much weaker thermal gradient in the Benguela Current-influenced region resulted in a high amount of β sne that could indicate neutral assembly processes. The intensification of upwelling during the mid-Pliocene 4.6-3.2 Ma (i.e., historical factors) were likely responsible for setting up the strong disjunction between the species-poor west coast and species-rich south and east coast floras, and this separation continues to maintain two systems of community structuring mechanisms in the Atlantic and Indian Ocean influenced sides of South Africa.

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Section: Discussionsupporting

confidence: 57%

Seaweeds in Two Oceans: Beta-Diversity

Smit

Bolton

2017

Front. Mar. Sci.

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“…This is despite the fact there are major ports located all along the coastline that would have been exposed to centuries of shipping history from all global regions. Thus, it would initially appear that the combined climatic and oceanographic regimes that form the environmental backdrop within the different biogeographic regions (Bustamante and Branch 1996;Emanuel et al 1992;Lombard 2004;Sink and Branch 2005) are influential in bioinvasion success and spread along the South African coastline. Interestingly, a high number of introduced species are shared across bioregions, the majority of these being found on the west coast and within the transitional zone between the west and south-east coast, where there is a well-documented overlap of indigenous species (Griffiths and Branch 1991).…”

Section: Spatial Patterns Of Bioinvasionmentioning

confidence: 99%

Revealing the scale of marine bioinvasions in developing regions: a South African re-assessment

et al. 2011

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As recently as 2009 the number of introductions recorded for South Africa comprised 22 marine and estuarine species. This review aims to reassess the diversity and scale of introduced marine and estuarine species in the region. Accurate taxonomic and systematic work, broad review of historical records and new sampling surveys across selected marine habitats conducted by a team of local and international experts has effectively revealed the presence of previously misidentified, overlooked, or new introductions. A total of 86 introduced and 39 cryptogenic species are recognized, increasing known numbers four and twofold respectively within 1 year, although the current assessment is far from fully comprehensive. Additional species were revealed within the historic literature (76%), from surveys conducted post-2005 (11%) and following taxonomic resolution (13%). Temporal analyses confirmed discovery rates were increasing over time. Ship fouling and ballast water were the dominant vector pathways, accounting for 48 and 38% respectively. Spatial analyses revealed patterns of bioinvasion to be significantly higher on the west coast compared to the other coastal regions. Overall, 53% of introductions were concentrated within harbour areas with only 4 opencoast invaders detected at present. Introduced species found in the cool and warm-temperate provinces of the west and south coast mainly originated from the northern hemisphere (65%). In contrast, introductions located in the sub-tropical and tropical provinces of the east coast mainly originated from the southern hemisphere (18%), with the remaining 17% of introduced species being of unknown origin. The research approach described has proven pivotal, contributing massively toward revealing the true scale and patterns of bioinvasion for a developing region within a relatively short period of time.

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“…threats because they lie at the interface between terrestrial and subtidal habitats and thus bear the impact of both terrestrial and marine alterations. For these reasons, large to mesoscale survey efforts of benthic organisms are being conducted in temperate intertidal areas (Barry et al 1995, Sink et al 2005, Nakaoka et al 2006, Delaney et al 2008). …”

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confidence: 99%