Disjunctions in the Diptera (Insecta) fauna of the Mediterranean Province and southern Africa and a discussion of biogeographical considerations : ecological overview article
- Kirk-Spriggs, A H, McGregor, Gillian K
- Authors: Kirk-Spriggs, A H , McGregor, Gillian K
- Date: 2009
- Language: English
- Type: text , Article
- Identifier: vital:6880 , http://hdl.handle.net/10962/d1011636
- Description: This paper explores disjunctions in the Diptera fauna of the Mediterranean Province and southern Africa, drawing from eight families of Diptera, the more ancient Psychodidae and Vermileonidae, and the more recent Acroceridae, Asilidae, Bombyliidae, Dolichopodidae, Pipunculidae and Sciomyzidae. Information from recent published revisions is geo-referenced and plotted onto maps using GIS software. These distribution patterns are interpreted and probable means and routes of dispersal between the two regions are discussed. The concept of an Afrotropical sub-Saharan boundary is outlined and it is argued that although the vast, arid and virtually abiotic Sahara acts as a barrier to dispersal today, relict floral and faunal populations of Mediterranean provincial origin still occur on the Hoggar and Tibesti Mountains of the central Sahara, indicating that the aridification of the Sahara is a very recent event. The presence of extensive palaeolakes formerly covering ca 10% of the present-day Sahara is regarded as evidence in support of this hypothesis. These lakes and their associated catchments, situated in basins between the central Saharan mountains, could clearly have acted as a humid route of dispersal as recently as 4000 BP, when these lakes began to recede, and this route is here regarded as a "central high Africa corridor"; a filter-bridge between the Mediterranean Province and southern Africa. Examples of Mediterranean provincial species of Ephydridae and the muscid genus Lispe Latreille, 1796, occurring as far south as the AÏr Massif in northern Niger are cited as examples of relict montane Diptera of Mediterranean provincial origin in the southern Hoggar Mountains; these groups being associated with the margins of standing water. Balinsky's (1962) concept of an "arid corridor" is also re-examined, using examples from the larger, less mobile Diptera, and it is concluded that such a pattern may not be the result of aridity, but represent an "eastern high Africa corridor", broadly corresponding to the "African Supers well". Other perceived distribution pathways between the Holarctic and Afrotropical Regions are mapped. Anemochore dispersal is considered, and the extent of the Afrotropical Region is discussed. Mediterranean tectonic evolution on both a globe of constant size and on a smaller Jurassic globe is also considered. It is concluded that if all the transitional zones between the zoogeographical regions are to be given more-or-less equivalent treatment, we must avoid setting boundaries based on earlier faunal distributions. For this reason the current boundary between the Palaearctic and Afrotropical Regions, arbitrary as it is, should be retained, despite evidence suggesting recent continuity between sub-Saharan Africa, North Africa and the Arabian Peninsula, corresponding broadly to the African and Arabian lithospheric plates.
- Full Text:
- Date Issued: 2009
- Authors: Kirk-Spriggs, A H , McGregor, Gillian K
- Date: 2009
- Language: English
- Type: text , Article
- Identifier: vital:6880 , http://hdl.handle.net/10962/d1011636
- Description: This paper explores disjunctions in the Diptera fauna of the Mediterranean Province and southern Africa, drawing from eight families of Diptera, the more ancient Psychodidae and Vermileonidae, and the more recent Acroceridae, Asilidae, Bombyliidae, Dolichopodidae, Pipunculidae and Sciomyzidae. Information from recent published revisions is geo-referenced and plotted onto maps using GIS software. These distribution patterns are interpreted and probable means and routes of dispersal between the two regions are discussed. The concept of an Afrotropical sub-Saharan boundary is outlined and it is argued that although the vast, arid and virtually abiotic Sahara acts as a barrier to dispersal today, relict floral and faunal populations of Mediterranean provincial origin still occur on the Hoggar and Tibesti Mountains of the central Sahara, indicating that the aridification of the Sahara is a very recent event. The presence of extensive palaeolakes formerly covering ca 10% of the present-day Sahara is regarded as evidence in support of this hypothesis. These lakes and their associated catchments, situated in basins between the central Saharan mountains, could clearly have acted as a humid route of dispersal as recently as 4000 BP, when these lakes began to recede, and this route is here regarded as a "central high Africa corridor"; a filter-bridge between the Mediterranean Province and southern Africa. Examples of Mediterranean provincial species of Ephydridae and the muscid genus Lispe Latreille, 1796, occurring as far south as the AÏr Massif in northern Niger are cited as examples of relict montane Diptera of Mediterranean provincial origin in the southern Hoggar Mountains; these groups being associated with the margins of standing water. Balinsky's (1962) concept of an "arid corridor" is also re-examined, using examples from the larger, less mobile Diptera, and it is concluded that such a pattern may not be the result of aridity, but represent an "eastern high Africa corridor", broadly corresponding to the "African Supers well". Other perceived distribution pathways between the Holarctic and Afrotropical Regions are mapped. Anemochore dispersal is considered, and the extent of the Afrotropical Region is discussed. Mediterranean tectonic evolution on both a globe of constant size and on a smaller Jurassic globe is also considered. It is concluded that if all the transitional zones between the zoogeographical regions are to be given more-or-less equivalent treatment, we must avoid setting boundaries based on earlier faunal distributions. For this reason the current boundary between the Palaearctic and Afrotropical Regions, arbitrary as it is, should be retained, despite evidence suggesting recent continuity between sub-Saharan Africa, North Africa and the Arabian Peninsula, corresponding broadly to the African and Arabian lithospheric plates.
- Full Text:
- Date Issued: 2009
The extent of public green space and alien plant species in 10 small towns of the sub-tropical Thicket Biome, South Africa
- McConnachie, Matthew M, Shackleton, Charlie M, McGregor, Gillian K
- Authors: McConnachie, Matthew M , Shackleton, Charlie M , McGregor, Gillian K
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6713 , http://hdl.handle.net/10962/d1006755
- Description: Urban areas in developing countries will accommodate nearly 90% of the projected world population increase between 1995 and 2030. Despite this, few studies, especially in smaller towns, have been carried out on urban green space areas in the developing world. This paper makes a first step in this regard, reporting on the extent and state of urban green spaces within 10 small towns in the Eastern Cape (South Africa). After measuring the size and state (in terms of woody plant cover) of public green space, we then sought patterns across the 10 towns between green space attributes, such as area, density, mean size and proportion of alien or indigenous, with socio-economic attributes of the towns. The area and state of current public green space varied markedly between the towns, with the poorer towns faring the worst. Lower income levels were significantly negatively correlated with the area and quality of public green space. Despite this, human population density and per capita green space were the best predictors of the proportion and mean area of public green space present in the towns. The proportion of town green space and the per capita green space were the best predictors of changes in woody plant composition and density.
- Full Text:
- Date Issued: 2008
- Authors: McConnachie, Matthew M , Shackleton, Charlie M , McGregor, Gillian K
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6713 , http://hdl.handle.net/10962/d1006755
- Description: Urban areas in developing countries will accommodate nearly 90% of the projected world population increase between 1995 and 2030. Despite this, few studies, especially in smaller towns, have been carried out on urban green space areas in the developing world. This paper makes a first step in this regard, reporting on the extent and state of urban green spaces within 10 small towns in the Eastern Cape (South Africa). After measuring the size and state (in terms of woody plant cover) of public green space, we then sought patterns across the 10 towns between green space attributes, such as area, density, mean size and proportion of alien or indigenous, with socio-economic attributes of the towns. The area and state of current public green space varied markedly between the towns, with the poorer towns faring the worst. Lower income levels were significantly negatively correlated with the area and quality of public green space. Despite this, human population density and per capita green space were the best predictors of the proportion and mean area of public green space present in the towns. The proportion of town green space and the per capita green space were the best predictors of changes in woody plant composition and density.
- Full Text:
- Date Issued: 2008
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