Polygala lewtonii Small (Polygalaceae)
Common Name: Lewton’s polygala, Lewton’s milkwort

Distribution: Lewton’s polygala occurs in Ocala National Forest (on the Mount Dora Ridge in Marion County) and on the Lake Wales Ridge in Lake, Osceola, Orange, Polk and Highlands Counties, Florida.

Habitats: Lewton’s polygala occurs on yellow sands in sandhill, turkey oak sandhill and oak-hickory scrub.

Life History: Lewton’s polygala is a short-lived perennial (usually < 5 years) to 20 cm in height. Plants produce multiple stems from a central root crown. Stems may be prostrate, ascending or erect. Lewton’s polygala has three kinds of flowers. Chasmogamous (open-pollinated) flowers are borne on many-flowered terminal racemes. Belowground cleistogamous (self-pollinated) flowers are produced on few-flowered racemes up to 40 cm long, which occur a few centimeters below the surface of the sand. Lewton’s polygala also occasionally produces solitary aboveground cleistogamous flowers in the axils of the lower leaves. The fruit is a capsule containing two seeds. Each seed has a fleshy appendage that attracts ants and is believed to aid in seed dispersal.

Phenology: Seedling recruitment occurs throughout the year, but is greatest during the cooler dry-season months. Peak chasmogamous flowering occurs in March and April. Several (usually 5-10) flowering stems may be produced annually, each stem usually with 20-25 flowers. Fruits mature in April and May. The phenology of belowground flowering is unknown.

Breeding System and Pollination: The flowers of Lewton’s polygala are bisexual. The chasmogamous flowers are pink to pale purple in color and attract a variety of insect visitors. In the absence of insect pollination, spontaneous selfing (autogamy) probably occurs. The cleistogamous flowers are necessarily autogamous.

Genetics: The genetics of Lewton’s polygala has not been investigated.

Population Dynamics: Aboveground populations of Lewton’s polygala fluctuate widely in response to fire frequency and rainfall. Individuals are killed by fire but there is dramatic postfire seedling recruitment from a persistent (and apparently long lived) seedbank. The number of postfire individuals often exceeds the number of prefire individuals by an order of magnitude. Between fires, population sizes fluctuate in response to annual rainfall patterns but with an overall downward trend.

Interesting Facts: Lewton’s polygala is amphicarpic. Amphicarpy, a rare breeding system known from fewer than 100 flowering plant species, is characterized by the production of both aboveground chasmogamous flowers and belowground cleistogamous flowers. While ant dispersal is common in many pyrogenic communities, it is apparently rare in Florida xeric upland ecosystems. Ants of several species are known to collect Lewton’s polygala seeds, but the fate of these seeds is still unknown.

Data Collected by Archbold Biological Station’s Plant Ecology Lab: The Plant Ecology Lab has investigated several aspects of the biology, autecology and demography of Lewton’s polygala. We have been following several populations at Lake Wales Ridge State Forest since 1996 and recently added a large new study site at the Lake Wales Ridge National Wildlife Refuge (Carter Creek Sandhill). A preliminary study of the breeding system was conducted in 1998 and additional work is planned for 2003. Lewton’s polygala’s habitat requirements have been documented and quantified. A multi-year germination experiment is currently being conducted to determine the effects of seed depth and time-since-sowing on seed germination and dormancy. We are also studying the fire ecology and seed dispersal of this species.

Data Availability: Data are not currently available.

Contact Person: Carl W. Weekley

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