Eastern lilaeopsis (Lilaeopsis chinensis) COSEWIC assessment and status report: chapter 6
Biology
General
L. chinensis is placed in the family Apiaceae. It is a semi-aquatic perennial herb found in maritime environments, growing on the shoreline in the intertidal zone. The species is a facultative brackish water species, known to grow well in a controlled environment when provided with freshwater only (Affolter 1985). Densities are known to be very high at three sites in Nova Scotia (Keddy 1987, pers. obs.). More specific aspects of the species’ biology are provided below.
Reproduction and physiology
L. chinensis produces small clusters of five to seven tiny white flowers within an umbel, which emerges several centimetres from a node along a thin rhizome. Flowering takes place in August and September, and with most plants producing seed by mid-September in Nova Scotia (Keddy 1987).
Reproduction is through asexual and presumably sexual means. Most plants are thought to arise from a rhizome through vegetative reproduction, which is thought to be the main means of reproduction necessary for maintaining populations. Self-pollination of flowers is also known to occur in a controlled environment, without artificial manipulation (Affolter 1985). Mechanisms of cross-pollination are not known.
Germination success, seed viability and seed production have not been quantified for L. chinensis, but with an assumed production success of 100%, five to seven seeds per umbel would be produced; it is expected germination success would be a lot lower, as qualitatively noted by Affolter (1985), perhaps closer to the 28-60% germination success he found for the related L. carolinensis. All populations in Nova Scotia found by Keddy (1987) and during the recent investigation had flowering plants that had produced seeds. Germination is assumed to be epigeous (embryo cotyledon or seed leaf appears above ground as in most other dicot species and as in the related L. carolinensis (Affolter 1985)).
With respect to edaphic requirements, L. chinensis has been found growing in both muddy environments and those covered with fine gravel. Although the species appears to grow well in semi-aquatic environments, submerged under several metres of water for up to half of every day, Affolter (1985) found plants grew well under relatively well-drained conditions without any submergence. L. chinensis grows well in controlled environments with pure freshwater, but its upper limit of salinity tolerance is unknown. L. chinensis appears to exhibit a fair amount of phenotypic plasticity dependent on light exposure and submergence, such as number, density and length of leaves and number of flowers, but linkage between these effects and fitness have not been made (Affolter 1985). L. chinensis was the least plastic of the Lilaeopsis species cultivated by Affolter (1985).
Survival
Based on personal observations of this species, “recruitment” would appear to be mainly through vegetative growth; it is expected to have the ability to remain viable for short periods even if no or little growth is possible during a given year. Certainly, recruitment through sexual reproduction or self-pollination need not be significant for L. chinensis to sustain populations. However, nothing has been noted regarding individual survivorship, mainly due to the nature of its growth; plants grow as masses of rhizomes in high densities, which makes it very difficult to quantify survivorship of an “individual”. Through management (i.e., introduction into other areas), population growth and range expansion could be facilitated if thought to be necessary. Natural population growth and range expansion is possible, although is presumably slow and at a fine spatial scale.
Dispersal
Dispersal of individuals is mainly at a fine spatial scale through vegetative growth, spreading vegetatively over a scale of several decimetres within a growing season (Affolter 1985). Clumps of vegetation disrupted through wave action or other water movement may provide the means for colonization and dispersal (Stevenson 1947). Seeds are presumably dispersed through tidal fluctuations and water current, aided by the spongy tissue in the seed that allows them to remain buoyant for considerable time (Affolter 1985). There is the potential for birds to be dispersal vectors over long distances (Affolter 1985). Mechanisms of pollination are unknown.
Rarity at northern locales reduces the expectancy of successful natural recolonization from American populations, with a slim likelihood of this happening. Dispersal and reproduction in this species needs to be researched further.
Nutrition and interspecific interactions
Little is known regarding the nutrient requirements of L. chinensis. However, Affolter (1985) found plants produced more flowers and leaves in well-drained and sunnier sites than in shady or submerged conditions.
Although interspecific competition has been thought to limit the distribution of this species (Stevenson 1947, Affolter 1985), restricting it to the intertidal environment, evidence suggests this is not entirely true. Keddy (1987) found L. chinensis growing in high densities both in open mudflats and within dense stands of much taller S. alterniflora. At some sites, it has been found in association with this species and up to three others (Glaux maritima, Plantago maritima, Solidago sempervirens). Without detailed maps showing change over time, it is difficult to determine if these associations are stable or representative of a transitional take-over of habitat by larger plants. However, L. chinensis was found more often within stands of S. alterniflora than outside of these stands during recent field investigations, with no apparent difference in leaf health or flowering density.
Adaptability
It is apparent through previous surveys that L. chinensis can withstand sometimes hostile and widely fluctuating environments. Wave action, periodic weather events (e.g., high water levels, strong winds, ice), and fluctuations in temperature, moisture and salinity at both short and long temporal scales provide a dynamic and unstable environment in which L. chinensis grows. Populations have withstood anthropogenic changes in water flow and nearby disturbance at one site in southern Nova Scotia. However, the extent of its tolerance to human disturbance is largely unknown.
Plants have been successfully grown in controlled, greenhouse environments (Affolter 1985), and individuals could be introduced from such sources. Transplants of L. chinensis have not been attempted.
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