Biotic invasions are one of the most important reasons for changes in biodiversity. We made a descriptive study to document annual fluctuations in spider density of the genus Argiope (A. lobata and A. bruennichi), after we observed an invasion of these species in the Natural Park of the Columbretes islands (Mediterranean, Spain) during summer 2004. Since then, both species have been present in the island until 2008, with the exception of 2007 when no individuals of A. bruennichi were observed during the censuses that were conducted during the month of August of each year. The percentage of A. lobata spiders was higher than that for A. bruennichi during five consecutive years. Our results suggest that the biotic and abiotic conditions of the island must be more favourable for A. lobata than for A. bruennichi. Alternatively, high competition may occur among species. The density of both Argiope species has decreased along the years, suggesting that the conditions and habitat of the island may not be adequate for these species. Our observations suggest that the presence of Argiope in Columbretes should not represent a threat for the endemic arthropod species in the island or the endemic lizard Podarcis atrata. Nevertheless, this is something that should be supported with empirical data. It is therefore highly recommended to conduct long term studies to monitor the density of their populations, to examine their diet and their interactions with other species in the island. Future studies should be also focused towards the knowledge of the invasion patterns and mechanisms of successful or unsuccessful spider invasions in insular ecosystems.
|Number of pages||10|
|Journal||Bolleti de la Societat d'Historia Natural de les Balears|
|Publication status||Published - 2010|
- Conservation Columbretes islands
- Global change
ASJC Scopus subject areas