Diagnostic Characteristics
In the past, Dodecatheon frenchii was thought to be a variety or ecological morph of Dodecatheon meadii. Detailed scientific work by Voigt and Swayne (1955) and Olah and Defilipps (1968) respectively determined that D. frenchii was a distinct taxon based upon phenotypic and genotypic differences.
Habitat
Dodecatheon frenchii has a small geographic range extending from southern Illinois to eastern Missouri and Arkansas, Indiana and western Kentucky (Hauser et al. 1981). It is found in close association to sandstone ledges, overhangs and bluffs, preferring north and east-facing exposures (Tucker 1982, Mohlenbrock 1978). French's shooting-star grows in habitats which yield little competition from other plant species, often growing alone in bare soil.
In Arkansas, Dodecatheon frenchii is found occasionally in large numbers in areas that have not been impacted by timber management (Tucker pers. comm.). To date, the species is found in only two counties within the state, Newton (numerous occurrences) and Cleburne (one occurrence).
All occurrences of D. frenchii within Kentucky are known from sandstone rock-shelters, ranging in size from very small overhangs to large shelters (Evans pers. comm.). Substrates on which the species occurs are composed typically of sandy soil. Often, the species grows by itself, with no associated plant species.
In Illinois, D. frenchii has been reported within a 10-mile wide belt in the extreme southern portion of the state (Voigt and Swayne 1955). The species has been found under sandstone ledges or "rock houses" (Schwegman pers. comm., Olah and DeFilipps 1969) in canyons of streams that flow predominantly southward (Voigt and Wayne 1955). It is apparently found most frequently under north and east-facing bluffs, growing in areas where light readings are 14-25 percent less than the 5000-6000 foot candles recorded for D. meadii habitat. Soil layers upon which the plants grow are composed primarily of sandy residuum or unweathered loess (Kurz and Bowles 1981). Parietaria pensylvanica is a common associate (Schwegman pers. comm.). Additional associates include Cardamine arenicola, Cardemine pensylvancia and Samolus parviflorus in wet sites, and Chenopodium hybridum in dry sites (Kurz and Bowles 1981).
Extant populations in Indiana are known from Crawford and Perry Counties (Hauser et al. 1981). Within the state, French's shooting-star occupies the sides of steep, moist sandstone cliffs, often under overhangs. Plants occur on all aspects but typically remain shaded due to overhanging sandstone ledges (Homoya pers. comm.). Associates include Lycopodium selago-patens, Hydrangea arborescens, Asplenium pinnatifidum, Sedum ternatum, Polypodium vulgare and Heuchera parviflora (Hauser et al. 1981). Lycopodium selago-patens and Heuchera parviflora appear to be excellent indicators.
In Missouri, D. frenchii is apparently restricted to the lowest sandstone ledges and shelves of north-facing overhangs (Nelson 1979). Such environments are cool, moist, humid and relatively dark. Associates include cinnamon fern (Osmunda cinnamomea), hayscented fern (Dennstaedtia punctiloba) and lady fern (Athyrium filix-femina).
Ecology
French's shooting-star is a diploid (2n = 44) species (Olah and DeFilipps 1968). Since D. meadii is a tetraploid (2n = 88), hybrid sterility is likely as a barrier to interbreeding between the two taxa. High stainability of pollen (indicating fertility) is evident in both species. Both characteristics (different ploidy levels and high pollen fertility levels) lend credence to the specific elevation of both taxa (Olah and DeFillips 1968).
French's shooting-star typically grows as a pioneer species, protected beneath sandstone overhangs. Buffered from outside influences, D. frenchii begins seasonal development early in the spring. According to Biotic Consultants (1976), the average date for the appearance of the first leaf is between the 13th and 28th of February. Individual plants may form as many as 10 basal leaves. Flowering occurs as early as mid-March and can continue until late April. In southern Illinois, flowering occurs between March 14 and April 27 (Mohlenbrock 1978). A given plant can produce as many as 15 flowers, but this is not common. Seed capsules begin to form before the petals have withered away. By the end of May, leaves have begun to turn yellow and fruits are relatively large (up to 6 mm in length). Seeds mature by the end of June and are shed immediately. By early July, most plants have died (Biotic Consultants 1976).
The breeding system of D. frenchii is unknown, but it is assumed to be cross-pollinated by insects, as are most other species of the genus (Tucker 1982). The only insects that have been observed visiting D. frenchii flowers in Arkansas have been very small Dipterans and some small bees (Tucker 1982). According to Tucker (1982), extensive visitation by insects to D. frenchii flowers apparently does not occur. In a study of the pollination ecology of the closely related D. amethystinum, however, small bees and flies were frequently seen visiting the flowers, but none were actually involved with the pollination of the plants (Macior 1970). The only effective pollinators of D. amethystinum were the queens of Bombus affinis, B. griseocollis, B. impatiens, B. vagans and B. nevadensis auricomus, with the exception of B. bimaculatus, where queens and drones were equally effective (Macior 1970). Similar and/or identical species may effectively pollinate D. frenchii flowers as well. For an in-depth description of the foraging and pollination behavior of Bombus bees on D. amethystinum, see Macior (1970).
Seed dispersal occurs as capsules open, releasing the seeds (Tucker 1982). It is thought that seeds accumulate within the soil forming a seed bank within close proximity to the parent plants. Ant-lions and ants have been frequently observed in close proximity to seedlings, but it is not known whether they play a role in seed dispersal (Tucker 1982).