In January of 2011 U.gibba began to appear in the water of a land contour supplied dammed pond which had been constructed mid way through 2010. These photos taken last week highlight the proliferation of the species over the course of 12 months.
This is the Far North form as discovered in a single location by Bruce Salmon in the late 1990's and described by him in his book Carnivorous Plants of New Zealand, 2001 (Ecosphere Publications). With readily produced seed without the need for a natural pollinator and a spur that is shorter than the three lobed lower collora it resembles the U.gibba form found in Eastern Australia being distinct from the more common West Coast form found in locations north and south to the west of Auckland, New Zealand, the two forms being separated by significant geographical distance. With good foundation Salmon concludes that the form arrived via migrating wading birds from the east coast of Australia. It has been spreading about the far north region of the North Island and the population in the pond featured here likely owes its existence in the location to transient Anas platyrhynchos, the Mallard duck. The other possible vector for the spread of the form is the human introduction to ponds of water lillies which can contain sections of the bladderwort. As can be seen, although on a working farm rather than a lifestyle property, this pond has a water lilly in it.
U.gibba is listed by the Auckland Council as a plant pest and it is illegal under biosecurity legislation to propagate, distribute, sell or spread the species within New Zealand. There is evidence that U.gibba is displacing the aquatic reluctant pollen producer U.australis in the far north region (Salmon). However, drought patterns in recent years in the region may have contributed to the reduction of U.australis.
The final photo here taken at the same time in 2011 gives a clear indication of just how vigorously U.gibba Far North form has established itself over the intervening 12 months.
Edited by Kiwi Earl, 03 February 2012 - 09:34 AM.