Threats to dragonflies on land islands can be as great as those on oceanic islands

Simple item page
dc.contributor.authorSamways M.J.
dc.contributor.authorPryke J.S.
dc.contributor.authorSimaika J.P.
dc.date.accessioned2011-05-15T15:58:54Z
dc.date.available2011-05-15T15:58:54Z
dc.date.issued2011
dc.description.abstractWe ask whether oceanic islands and equivalent-sized continental blocks, which we call here 'land islands', are similar or not in their species richness, number of range-restricted species, and in number of threatened species. We used sites in southern Africa and islands in the Western Indian Ocean. We chose dragonflies as they are taxonomically tractable, well surveyed, and provide a range of characteristics from narrow-range endemics to widely-spread and vagile opportunists. We then selected as many oceanic islands as possible where there were sufficient data to make comparisons with land islands of a similar area in African savanna, grassland and mountains rich in endemic species. Generalized Linear Mixed Models were used to analyse the overall, range-restricted and threatened species richness for all islands (both oceanic and land) and then for the two types of island separately. Species richness increased with island size, with oceanic and land island size relationships being similar. Land islands overall had significantly more range-restricted species. Species on land islands were as threatened as those on oceanic islands. However, the land islands of the Western Cape were under a higher level of threat than oceanic islands of comparative size. The large islands of Madagascar and Sri Lanka were outliers with very high levels of threat. Translated into conservation, the results illustrate that over-generalizations about island faunas being more threatened than continental ones are not necessarily valid. While not wishing to draw attention away from the urgent conservation action needed on many tropical islands, we argue that comparisons of oceanic versus land islands detract from the more urgent task of local conservation action based on the special needs of any particular area, whether land or oceanic. It is more meaningful to establish how threats operate and how to mitigate them on small populations rather than focusing purely on any particular island type per se. © 2011 Elsevier Ltd.
dc.description.versionArticle
dc.identifier.citationBiological Conservation
dc.identifier.citation144
dc.identifier.citation3
dc.identifier.issn63207
dc.identifier.other10.1016/j.biocon.2010.12.034
dc.identifier.urihttp://hdl.handle.net/10019.1/10902
dc.subjectconservation management
dc.subjectconservation planning
dc.subjectdragonfly
dc.subjectendangered species
dc.subjectendemic species
dc.subjectfloristics
dc.subjectisland biogeography
dc.subjectsavanna
dc.subjectspecies richness
dc.subjecttaxonomy
dc.subjectMadagascar
dc.subjectSouth Africa
dc.subjectSri Lanka
dc.subjectWestern Cape
dc.subjectAnisoptera (dragonflies)
dc.titleThreats to dragonflies on land islands can be as great as those on oceanic islands
dc.typeArticle
Files
Collections
Stellenbosch University - Scopus Publications