New Zealand Journal of Botany abstracts
Pollinator behaviour, not increased resources, boosts seed set on forest
edges in a New Zealand Loranthaceous mistletoe
Benjamin R. Montgomery1*
Dave Kelly1†
Alastair W. Robertson2
Jenny J. Ladley1
1Department of Plant and Microbial Sciences
University of Canterbury
Private Bag 4800
Christchurch, New Zealand
*Present address: Department of Ecology and Evolutionary Biology, University
of Michigan, Ann Arbor, MI 48109-1048, USA.
†Author for correspondence. Email: dave.kelly@canterbury.ac.nz
2Ecology Group
Institute of Natural Resources
Massey University
Private Bag 11222
Palmerston North, New Zealand
Abstract The endemic New Zealand mistletoe Peraxilla
tetrapetala (Loranthaceae) has previously been shown to be pollinator
limited, and to experience higher fruit set in increasingly fragmented habitats,
but the mechanism for higher fruit set on edges has not been studied. Edges
could affect plant resources (through higher light) and/or pollinator behaviour.
This study measures the degree to which pollination and resource limitation
affect female reproductive success along a gradient of increasing exposure
to the forest edge. Forty-two plants in pairs at varying distances from the
forest edge were selected from within two Nothofagus forest fragments
in the 1999/2000 season; and on one plant in each pair, all ripe undamaged
flowers were hand-pollinated. Light levels and the degree of edge exposure
were measured for each plant, and path analysis was used to determine the
relationship of these variables to proportion fruit set. In agreement with
previous studies, unmanipulated plants were found to be strongly pollen limited,
especially in shady locations. However, on plants receiving hand-pollination,
fruit set was uniformly high and was unaffected by edge exposure or light
levels. Direct observation of flower visitation rates by birds in the 2000/01
season showed that edge flowers were visited twice as often as interior flowers.
These results show that the higher fruit set on edges is due to visitation
patterns of pollinators, and not due to greater resource availability on edges.
This improved pollination on edges may help to buffer this declining plant
against local extinction.
Keywords bird pollination; edge effects; fragmentation;
Loranthaceae; mistletoe; Peraxilla; pollinator limitation; resource
limitation
B02049 Received 4 July 2002; accepted 18 February 2003; published 11 June
2003
New Zealand Journal of Botany, 2003, Vol. 41: 277-286
0028-825X/03/4102-0277 $7.00 © The Royal Society of New Zealand
2003
PDF file of entire paper: Print-quality (114K) |
screen-quality (64K)
This year's abstracts |
Journal home page |
All abstracts |
Publishing home page
