Experimental transport of Trichomanes speciosum spores on Azorean woodpigeon feathers as a possible explanation for interisland dispersal

Abstract

AbstractTrichomanes speciosum is a protected fern whose sporophyte generation is abundant on the island of Terceira (Azores archipelago, Portugal) but whose dispersal mechanism has never been directly documented. Based on its distribution, bird‐mediated epizoochory is a likely mechanism for spore dispersal, but there is no evidence to support this hypothesis. Laboratory experiments were performed to test the transportability of T. speciosum spores by the woodpigeon (Columba palumbus azorica), by observing the persistence of artificially added spores to feather samples that had been exposed to treatments of different wind speeds (2, 4, 6, and 8.25 m s−1) to simulate flight. The spores attached readily to the woodpigeon feathers, and 47% of the spores, on average, were lost after applying the maximum wind speed of the experiment. Spore loss was significantly related to wind speed but not to time of exposure. These findings suggest that if a fern spore adheres to the feathers of a woodpigeon, it has a probability of around 53% to remain there during flight and to eventually be dropped away from its origin. This study not only sheds new light on the possibility of T. speciosum spores being dispersed by woodpigeons, but also provides mechanistic evidence for spore retention on bird surfaces more generally.