Diversity and evolution of Volcanalia in Seychelles

Seychelles archipelago consists of two very different types of islands. The "Inner Islands" are terrestrial peaks of a mainly submarine plateau which is a fragment of the former Gondwana continent, isolated about 75 million years ago. Multiple increase and decrease of the sea level led to multiple separation and reunion processes of the Inner Islands. The "Outer Islands" are geologically young coral atolls; they have never been connected with the granitic islands. Due to their continental history, age and isolation, the Seychelles host a diverse and archaic flora and fauna and have a very high endemism rate. Despite their great ecological and evolutionary significance the insect fauna of Seychelles has received relatively little attention. The only large-scale study carried out so far was based on material collected almost 100 years ago. Only recently the international research project "Indian Ocean Biodiversity Assessment 2000-2005" (IOBA) is realized. Our project will contribute to the IOBA. It focusses on the effects of long term isolation of the archipelago in combination with changing patterns of terrestrial habitats on the evolution and speciation of phytophagous insects. The model group for this study is Volcanalia, a palm-feeding genus of cixiid planthoppers (Hemiptera). Cixiids have colonised various island groups and there they show interesting radiation phenomenons. A group of Cixiidae that appears to have undergone adaptive radiation on Seychelles is the endemic genus Volcanalia, comprising 12 species. The project addresses the taxonomy, phylogeny, ecology and biogeography of this genus. The working hypothesis is: Volcanalia is an archaic, monophyletic taxon, which has gone through an adaptive radiation process on Seychelles (both allopatric and sympatric speciation), caused by multiple geographic seperation and reunion of islands and by host plant shift. To check this hypothesis, following questions are to be answered: (1) Which species belong to Volcanalia ? (redefinition of the genus on a phylogenetic basis) (2) Which species occur on which island(s) ? (3) Which plant species are utilized ? (4) What are the temporary and geographic pathways of speciation ? Field studies will be made to gain data on host plants and on distribution within islands. Morphological studies are necessary to clarify the taxonomy of the species and to get data for a phylogenetic analysis. This phylogenetic analysis will - in combination with geological evidence - enable us to reconstruct the radiation and speciation processes of Volcanalia on Seychelles.

Seychelles archipelago consists of two very different types of islands. The "Inner Islands" are terrestrial peaks of a mainly submarine plateau which is a fragment of the former Gondwana continent, isolated about 75 million years ago. Multiple increase and decrease of the sea level led to multiple separation and reunion processes of the Inner Islands. The "Outer Islands" are geologically young coral atolls; they have never been connected with the granitic islands. Due to their continental history, age and isolation, the Seychelles host a diverse and archaic flora and fauna and have a very high endemism rate. Despite their great ecological and evolutionary significance the insect fauna of Seychelles has received relatively little attention. The only large-scale study carried out so far was based on material collected almost 100 years ago. Only recently the international research project "Indian Ocean Biodiversity Assessment 2000-2005" (IOBA) is realized. Our project will contribute to the IOBA. It focusses on the effects of long term isolation of the archipelago in combination with changing patterns of terrestrial habitats on the evolution and speciation of phytophagous insects. The model group for this study is Volcanalia, a palm-feeding genus of cixiid planthoppers (Hemiptera). Cixiids have colonised various island groups and there they show interesting radiation phenomenons. A group of Cixiidae that appears to have undergone adaptive radiation on Seychelles is the endemic genus Volcanalia, comprising 12 species. The project addresses the taxonomy, phylogeny, ecology and biogeography of this genus. The working hypothesis is: Volcanalia is an archaic, monophyletic taxon, which has gone through an adaptive radiation process on Seychelles (both allopatric and sympatric speciation), caused by multiple geographic seperation and reunion of islands and by host plant shift. To check this hypothesis, following questions are to be answered: (1) Which species belong to Volcanalia? (redefinition of the genus on a phylogenetic basis) (2) Which species occur on which island(s)? (3) Which plant species are utilized? (4) What are the temporary and geographic pathways of speciation? Field studies will be made to gain data on host plants and on distribution within islands. Morphological studies are necessary to clarify the taxonomy of the species and to get data for a phylogenetic analysis. This phylogenetic analysis will - in combination with geological evidence - enable us to reconstruct the radiation and speciation processes of Volcanalia on Seychelles.