Agalinis auriculata (Michx.) Blake
Eared False Foxglove
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Gerardia auriculata, Tomanthera auriculata
Basis for Listing
Agalinis auriculata is a poorly understood species that appears to be rare or infrequent wherever it occurs, even in the center of its range. It is now considered extirpated from a number of states where it once occurred. Fewer than 10 populations are known to exist in Minnesota, and all of the populations are quite small and occur in vulnerable prairie habitats. The size of these populations varies from one or two individuals to several hundred, but most populations have fewer than 50 plants. The extent of prairie habitats in southern Minnesota has declined as much as 99% since European settlement. The few remaining remnants tend to occur in railroad rights-of-way where their continued existence is uncertain. Agalinis auriculata was listed as an endangered species in Minnesota in 1984.
Flowers of A. auriculata are 2.5-5 cm (1-2 in.) long and grow opposite each other on an unbranched flowering stalk. The 5-cleft purple flowers have a pale-pink throat and red-purple spots. The upper 2 lobes are smaller than the lower 3, giving the flower a slightly asymmetric appearance. Mature plants are covered with short, stiff hairs. The unbranched, 4-angled stems grow from 15-90 cm (6-35 in.) in height. The opposite leaves bear a clasping auricle, or ear, from which the species derives its scientific name. It is the only member of the genus Agalinis with a retrorse-hispid stem and auricled leaves.
Early collection records of A. auriculata in Minnesota were from wet meadows in the Minnesota River valley. Those habitats are largely gone now, or have been degraded to the point where they no longer support a significant number of native species. More recent records include prairies, particularly prairie remnants along railroad rights-of-way.
Biology / Life History
Agalinis auriculata is an annual that flowers in August and early September. The earliest documented flowering in Minnesota was on the 12th of August and the latest was on the 4th of September. Most records show clustered flowering during the last few days of August. The flower structure is that of an insect-pollinated species, and bees have been suggested as the pollinators. Greenhouse studies indicate that the species is also capable of self-pollination. Laboratory studies demonstrate that seeds are dormant by October, require cold stratification and light for germination, and can persist in the soil for up to four years (Baskin et al. 1991). Agalinis auriculata is reputed to be a hemiparasite, obtaining part of its nutrition from the roots of other plants. Several grasses and composites have been imputed as hosts, but the identity of all possible host plants is not known. Field observations across the range suggest that light and certain soil conditions are limiting factors for this species. However, it is unknown how these factors interact to affect population dynamics.
Conservation / Management
Because A. auriculata is an annual species and maintains a seed bank in the soil, failure to relocate plants at a site where it was previously documented does not necessarily mean that it has been extirpated from that site. The population may be existing entirely as dormant seeds, waiting for favorable conditions to break dormancy and begin growing. The necessary stimulus is not known, but could be provided by animal activity such as gopher digging or ant mound building that might expose the seeds to light. Attempts to artificially stimulate the germination of a buried seed bank have never been successful and could be very harmful to the population or habitat. The best approach to management may be to allow natural ecosystem processes to proceed, possibly augmented by a regimen of spring burns during the dormant season (prior to plants greening up) that serve to control competing woody vegetation.
Conservation Efforts in Minnesota
In 2000, the Minnesota DNR's Natural Heritage and Nongame Research Program conducted a status survey for A. auriculata, revisiting sites found by the DNR's Minnesota Biological Survey in 1999 and searching an additional 40 sites in 8 counties. Results were poor, but because the species can maintain a seed bank, it is possible that it will eventually be found in habitats where it was not found during previous searches. This provides an excellent basis for conservation efforts, though as of 2009, no specific conservation actions had been undertaken.
Baskin, J. M., C. C. Baskin, P. D. Parr, and M. Cunningham. 1991. Seed germination ecology of the rare hemiparasite Tomanthera auriculata (Scrophulariaceae). Castanea 56:51-58.
NatureServe. 2006. NatureServe Explorer: An online encyclopedia of life [web application]. Version 5.0. NatureServe, Arlington, Virginia.
Pennell, F. W. 1935. The Scrophulariaceae of eastern temperate North America. Academy of Natural Sciences of Philadelphia Monograph 1. 650 pp.
Rawinski, T. J. 1990. Final status survey report: The distribution and abundance of eared false foxglove (Tomanthera auriculata). Unpublished report submitted to the U.S. Fish and Wildlife Service, Region 5, Newton Corner, Massachusetts. 4 pp.
Sather, N. P. 2000. Interim status survey report for Agalinis auriculata in Minnesota. Unpublished report submitted to the U. S. Fish and Wildlife Service, Twin Cities Field Office, Bloomington, Minnesota.