Area and habitat relationships in island land snail faunas: an Aegean case study exploring the choros model

WA Museum Records and Supplements | Updated 7 years ago

ABSTRACT – In the present paper we study the biogeography of land snails in the Skyros archipelago (central Aegean) using both conventional species-area analysis and the newly-developed choros model. The choros model is a simple mathematical relationship, which analyses species richness as a function of area and of environmental heterogeneity, quantified by assessing the number of defined habitats present on each island. We surveyed land snails on 12 islands of the archipelago of Skyros in the central Aegean Sea (Greece). The different types of habitats were defined based on the ecology and biology of each species distributed in the archipelago. Forty-two land snail species were recorded living in 11 different habitat types. The z-values from both models, the choros and the classic species-area relationship, place the archipelago in the "within biogeographic province" category, mainly due to the recent formation of the archipelago. This recent formation resulted in a group of small islands still behaving as parts of a continuous landmass. The recorded extinction of land snails in the archipelago follows the general pattern of extinctions of this animal group in the Aegean area. The choros model gave a better fit to the data than the classic species-area model, indicating that the range of habitats available plays a significant role in determining faunal diversity independently of area. The availability of knowledge on the ecology of each species in most islands of the Aegean enabled us to recognise the key environmental features on which we based the definition of the habitat types. Such background knowledge is essential if island studies are to progress beyond the simple demonstration of a species! area relationship.