Wild hyacinth (Camassia scilloides) COSEWIC assessment and status report: chapter 6
Biology
General
Wild hyacinth flowers in mid-spring (mid to late May) when pollinating insects are abundant. Similar to other woodland spring ephemerals, leaves and fruiting stalks die down by mid-summer. From field observations, seeds are produced in large numbers and germination occurs the next spring as the soil warms (the latter from author’s garden observations). Seed dispersal appears to be directly from the dry, dehiscent capsules on the tall fruiting stalks; the dry hard seeds do not seem to be attractive to woodland dispersal agents (such as ants) that would take the seeds further. Vegetative proliferation from bulb offsets is recorded as not usual (Oldham, 1988). Recent field observations supported this.
Reproduction
Flowers were observed with a variety of insect visitors on sunny days: butterflies, bumblebees, metallic green/bronze bees, small solitary bees, bee flies, syrphid flies, hover flies, but few or none on cloudy/rainy days.
During the field work for this study a group of hyacinths was excavated to observe indications of possible vegetative reproduction. Several mature bulbs were closely examined and no signs of vegetative offshoots or bulblets were seen. However, numerous small bulbs were among the mature flowering size bulbs and clearly separate from them, suggesting that these were seedlings of different ages. This conclusion was supported by the occurrence of mixed flower colours within colonies (white to very pale blue to pale blue), an indication of genetic variation that would not be expected with colonies developed only from vegetative proliferation.
Survival
Individual plants are likely long-lived, with little change in location from different observations over the past two decades. Natural threats to survival have only recently been noted, due to the rapid proliferation of Cormorant colonies on the smaller islands (their high numbers and direct impact on the ground as well as their rich excrement kills much of the vegetation including trees where they nest, and later supports a dense, competitive weed population). As recently as 1993 cormorant nesting areas were mapped as “rare animal sites” on Middle Island. The Camassia population on Middle Island has been severely reduced and apparently lost on East Sister Island, as observed in May of 2001. No indication of significant herbivory or uprooting of bulbs was observed at any of the populations.
Dispersal
Seeds are dispersed from dry dehiscent seed capsules, some of which fall over before opening, suggesting that seeds are not dispersed very far from the colony of flowering bulbs. The dry hard angular seeds appear to have no further dispersal adaptation once they leave the capsule. The clustering of plants, the mixed flower colours and numerous non-flowering plants within the colony supports this interpretation. Within a habitat there may be several colonies in dense clusters; it is uncertain what dispersal mechanism originates a new colony.
Nutrition and Interspecific Interactions
Robust colonies occur on sites of rich soil under partial shade, but often with no more than 10 cm of soil (Stone Road Alvar population observations). Pollinating insects are likely important for good seed development, but comparisons with bagged flowers excluding pollinators would confirm this.
Double-crested Cormorants are having a devastating effect on populations on East Sister Island (no sign of survivors in 2000 (M.J. Oldham, pers. comm.) and May of 2001 during field observations for this report, and greatly reducing the population on Middle Island (May 2001 observations).
Adaptability
On the Erie Islands the habitat for this species appears to be limited to rich soil over limestone, even though the soil may be thin in some areas, and generally under light to moderate shade from forest trees overhead. To the south it is reported in floodplain woods where the soil would be deeper.
Page details
- Date modified: