New Zealand Journal of Botany abstract
Seed production in Festuca novae-zelandiae: the effect of altitude and
pre-dispersal predation
J. M. LORD
Botany Department
University of Otago
P.O. Box 56
Dunedin, New Zealand
D. KELLY
Department of Plant and Microbial Sciences
University of Canterbury
Private Bag 4800
Christchurch, New Zealand
Abstract Festuca novae-zelandiae is a New Zealand
endemic bunchgrass that occurs from near sea-level to 1400 m. In a study
of seed production at a range of altitudes, flowering plants were found to
produce between 0 and 967 seeds. On average, 28.3% of florets were attacked by
invertebrate seed predators and a further 46.2% of ovules failed to produce a
mature seed for reasons other than predation. The most common, identifiable,
predators were Dipterid larvae, including the flightless
Diplotoxa
moorei. Seed set was most strongly related to the number of florets
initiated, but was also significantly related to rates of ovule failure and
pre-dispersal predation. Seed set did not vary systematically with altitude,
but ovule failure rate showed a significant increase and predation rate a
significant decrease with increasing altitude. Predation rate was also
positively related to plant density; altitude and plant density together
accounted for 56% of variation in predation rate. Path analysis showed that the
near-zero direct correlation between seed set and altitude was the product of
an indirect positive effect, via a strong negative effect on predation rate,
being cancelled out by indirect negative effects via reduced floret initiation
and increased ovule failure rates with increasing altitude.
Keywords reproduction; seed predation; altitude; Festuca
novae-zelandiae; Poaceae
B99004
Received 27 January 1999; accepted 19 April 1999
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