Original Paper

Biodiversity and Conservation

, Volume 17, Issue 6, pp 1465-1473

First online:

Why have endemic pollinators declined on the Ogasawara Islands?

  • Tetsuto AbeAffiliated withForestry and Forest Products Research Institute Email author 
  • , Shun’ichi MakinoAffiliated withForestry and Forest Products Research Institute
  • , Isamu OkochiAffiliated withForestry and Forest Products Research Institute

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Abstract

Flower visitors recently decreased in the Ogasawara Islands which are subtropical Pacific oceanic islands located 1,000 km south from Japan mainland. The aim of this study was to determine the main cause of this pollinator decline. We assumed four hypothesis, (i) honeybee competition hypothesis, (ii) forest decline hypothesis, (iii) agricultural insecticides hypothesis, and (iv) anole predation hypothesis. They were tested by distribution survey in the field, historical survey using literature, and predation experiment using mesh cages. As a result, the factors affecting the distribution among the islands and the timing of observed declines of native pollinators supported the anole predation hypothesis rather than other hypotheses. In addition, result of experimental predation test well explained the composition of flower visitors in the main islands (Chichi-jima and Haha-jima). So, we concluded that one invasive predator (the anole) has changed the pollination network in the Ogasawara Islands. To conserve the native pollination network, eradication of this invasive predator should take priority over the eradication of honeybees.

Keywords

Alien predator Anolis carolinensis Biological invasions Distributional pattern Introduced honeybee Oceanic islands Pollination disruption