Life-history monographs of Japanese plants. 2: Trillium camschatcense Ker-Gawl. (Trilliaceae)

Abstract

The life-history characteristics and demography of Trillium camschatcense (Trilliaceae) were studied and are described here. T. camschatcense, a typical polycarpic perennial, is a representative of the spring plants growing in temperate broad-leaved deciduous forests in the lowlands of Hokkaido and northern Honshu, and adjacent Far East regions. Flowering takes place in early to late April. T. camschatcense typically has three white petals and three sepals, is primarily pollinated by bumblebees (Bombus and Andrena spp.) and beetles (Carpophilus and Aphthonaltica spp.), with pollen/ovule ratios of 2200, and is a conditional outbreeder. Occasional inbreeders are also known in the north-eastern populations of Hokkaido. Capsules mature in late summer, late July to August. Light-brown seeds, 2–3 mm long, with a soft juicy elaiosome containing sugars such as fructose, glucose and saccharose attracts ants and beetles, but only ants are effective dispersal agents for Trillium seeds. Our long-term monitoring study has continued for 25 years from 1980 to 2004, and most of the flowering individuals turned out to be extremely long-lived, at ages of well over 20 years. Notably, frequent switches in growth stages occur, not only proceeding from the single-leaf sterile stage to the three-leaved sterile-stage but also reverting to earlier growth stages.