Browsing by Author "Scodanibbio, Lucia"

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    Is aquatic invertebrate endemism in the Western Cape region of South Africa related to the fynbos blackwaters?
    (2002) Scodanibbio, Lucia; Day, Jenny
    The south-western Cape of South Africa has a very endemic, specialized terrestrial flora and aquatic fauna. It has been argued that the high degree of endemism is related to the origin of the fauna, the multiplicity of habitats present and the harsh water chemistry characterized by low pH. The aim of this project was to look at the relationship between pH and endemism. Specifically I asked if there is a trichopteran and ephemeropteran fauna confined to the Cape and if this is true, I attempted to find out whether it is the acidic waters or its biogeographical origin that limits its distribution. I also attempted to identify a group of species that occurs at a wide range of pH values (i.e. pH insensitive) and another group that is intolerant of acidic waters. This was done by looking at historical data on species distribution and the pH ranges at which they were found, and these data then re-analysed in the light of fieldwork performed on the Breede River in the western Cape. A number of species within different genera ( e.g. Lithogloea, Leptecho and Agapetus) appears to be confined to the Cape. Their distribution is determined by both their origin and water chemistry conditions, which are characterised by low pH and pure, silt-free water. A warm stenothermal group, comprising Leptonema, Elassoneuria and Eatonica spp. is limited to the subtropical regions of South Africa, where water is alkaline. A eurythermal, pH-insensitive group that includes Castanophlebia calida, Ecnomus and Cheumatopsyche spp has a widespread distribution throughout the country. Lastly, there appears to be another eurythermal group ( e.g. Pseudopannota macu/osa, Pseudocloeon glaucum) that is intolerant of low pH values. As research is continuously discovering new species and new distribution records for old ones, it is likely that the above categories will need revision as more data are collected.
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    Pollination ecology of Mesembs
    (2002) Scodanibbio, Lucia; Bond, William J; Colville, Jonathan F
    Mesembryanthemaceae is one of the main plant families in the Succulent Karoo biome of South Africa. While its pollination ecology still remains largely unstudied, the system is thought to be overall generalised. This study sought to verify whether Mesemb species flowering during September and October in Vrolijkheit Nature Reserve have generalised or specialised pollination interactions. The determinants of insect choice to a particular plant species were investigated and possible mechanisms adopted by different plant species to prevent interspecific pollen transfer were explored. The system was found to have a generalisation level of 24.7%, indicating that one of four possible interactions actually took place. A relatively high degree of overlap in insect visitors was found between the three white-flowered species (Mesemhryanthemum longistylum, Phylloholus grossus and P. splendens). Colour was one of the main determinants of insect choice, whereby Drosanthemurn speciosum, the only red-flowered species in the study showed the highest degree of specialisation. Both scent and nectar production were relatively important in attracting flower visitors. Seasonality in flowering appeared to be a very important mechanism used to reduce overlap in insect visitors, especially among intrageneric species and those that had flowers of the same colour. Daily patterns in scent and nectar production also appeared to play a role in lowering pollinator-sharing. Given the general floral structure of most Mesemb flowers, these mechanisms are likely to be very important in contributing to species reproductive isolation and the low occurrence of hybrids recorded in natural conditions.