Abstract:
Within population variation in plant density can affect reproductive success and breeding systems. We examined such effects in Listera cordata R. Br., a north temperate terrestrial orchid, in a subalpine population in Colorado, USA. Hand pollinations showed that L. cordata was self-compatible as all pollinations produced fruits. Cross-pollinations differed significantly from self-pollinations, and had a higher number of seeds per capsule and higher % of fertilized ovules. Together they could compensate for the transmission advantage of self-pollinations. Average number of flowers per inflorescence was 4.2-4.4 and average fruit set was 20.7-23.7%. By establishing 36 plots with varying plant densities (1, 4, 8 and 16) and emasculating all flowers in target plants of a set of 20 plots, we estimated density effects on fruit and seed production. Plant density had no effect on the amount of reproduction except in reduced seed production of highly dispersed plants. Our results suggest that inbreeding depression may be an important selective factor in L. cordata. Further studies are needed to define its role in the evolution of mating systems in this species.

Author Keywords:
Orchidaceae, Listera, plant reproductive biology, geitonogamy, inbreeding depression, cross-pollination

KeyWords Plus:
INBREEDING DEPRESSION, SELF-FERTILIZATION, OUTCROSSING RATES, FRUIT PRODUCTION, PLANT-DENSITY, SEED-SET, IPOMOPSIS-AGGREGATA, POPULATION-DENSITY, MATING SYSTEMS, POLLINATION

Addresses:
Melendez-Ackerman EJ, Univ Puerto Rico, Inst Trop Ecosyst Studies, POB 363682, San Juan, PR 00936 USA
Univ Puerto Rico, Inst Trop Ecosyst Studies, San Juan, PR 00936 USA
Univ Puerto Rico, Dept Biol, San Juan, PR 00931 USA

Publisher:
SPRINGER-VERLAG WIEN, SACHSENPLATZ 4-6, PO BOX 89, A-1201 VIENNA, AUSTRIA

IDS Number:
435MQ

ISSN:
0378-2697