Observations on Acalypha deamii (Euphorbiaceae) in Ohio

Castanea, Jun 2003 by Becus, Marjorie S

ABSTRACT

Acalypha deamii was rediscovered in Ohio after almost 50 years. Six populations were found in southwest Ohio. The growth habit and habitat of these populations are described. Acalypha deamii reputedly has drooping leaves, but that is not a reliable character. Acalypha deamii is likely to be more common than reported and found throughout southern Ohio.

INTRODUCTION

Acalypha deamii (Weath.) H.E. Ahles is a little-known species reportedly restricted to four states: Arkansas, Indiana, Ohio and Tennessee (Gleason and Cronquist 1991). Recent investigations by Dr. Geoffrey Levin of the Center of Biodiversity, Illinois Natural History Survey, however, revealed the range to be far more extensive. Levin indicates A. deamii occurs from Virginia and Alabama north and west to Iowa and Kansas (Levin, pers. comm. 2002).

Much confusion has existed over the taxonomy of A. deamii. Some references list it as A. virginica L. var. deamii Weath. (Cooperrider 1995, Cooperrider et al. 2001); others, as A. rhomboidea Raf. var. deamii (Weath.) Weath. (Deam 1940, Fernald 1950). Levin (1999) clearly demonstrated that this taxon merits specific rank, a view shared by Mohlenbrock (1975) and Gleason and Cronquist (1991). Acalypha deamii differs from other members of the genus in North America by the combination of two carpels per flower and seeds exceeding 2.1 mm in length. This species has been stated to be characterized by drooping leaves (Deam 1940, Fernald 1950, Gleason and Cronquist 1991), a feature discussed later in this article.

Acalypha deamii was listed as presumed extirpated in Ohio (ODNAP 2000), having not been known from the state for nearly 50 years. I discovered a population of this species during a plant inventory of a Hamilton County park, Trillium Trails Wildflower Preserve, in southwest Ohio. (I made an A. deamii collection from this same location in 1985, but identified it as Acalypha sp.) Although the plants had two carpels and large seeds, and thus obviously were A. deamii, they lacked the drooping leaves mentioned in most descriptions of the species. In late August 2001, I decided to investigate two questions: 1) how rare or local is A. deamii in Ohio, and 2) are drooping leaves a reliable character for this species?

METHODS

I conducted a survey for Acalypha species in Hamilton County, which included counting and measuring fruits, recording habitat notes and collecting A. deamii specimens. Seven parks containing habitat similar to Trillium Trails Wildflower Preserve were selected in various parts of the county. This informal survey involved hiking wooded trails between August 30 and September 3, 2001 when the plants would be in fruit. Initially, any Acalypha found during the survey was scrutinized by counting and measuring fruits on site with a ruler. Although only two-seeded plants were suspected of being A. deamii, fruits were measured on numerous other

Acalypha plants. In early September the survey was expanded to include adjacent Clermont and Warren counties.

Herbarium specimens were collected and the largest local herbaria representative of the region where the A. deamii occurs were searched for material of this species (CINC, MICH, MU, OS). Specimens at the University of Cincinnati herbarium were annotated as appropriate. Appendix I lists known specimens of this species from Ohio.

On September 16, 2001, I transplanted two A. deamii plants from the Clermont County site to a garden at my house in order to observe the growth and habits of these plants.

RESULTS

Six populations of Acalypha deamii were discovered in southwestern Ohio. Voucher specimens were collected from three counties, Clermont, Hamilton, and Warren, from late August through October 2001.

Habitat patterns and general appearance characters were recorded and used for further searches. The plants occurred in mesic wooded habitats as well as rocky sandbars of Halls Creek, and the sandy shore of the Little Miami River. Acalypha deamii plants were often growing along the edge of a trail or a road, possibly for the additional sunlight not available further in the woods.

Acalypha deamii was always growing with robust Pilea pumila (L.) A. Gray; usually the two were interspersed in moist, wooded soil. This became a signal plant for appropriate habitat for A. deamii. Other associates included Laportea candensis (L.) Wedd., Amphicarpaea bracteata (L.) Fern., Eupatorium rugosum Houttuyn., and Acalypha rhomboidea Raf. Two or more of these species invariably would be present.

This assemblage of plants is an important field characteristic. When viewing Acalypha deamii interspersed with P. pumila, L. canadensis and A. rhomboidea, the plants have similar appearances with only slight differences in shades of green, glossiness, and leaf margins. When this assemblage is encountered, the individual plants can be examined and the number of carpels and length of seeds determined for the Acalypha members. To identify A. deamii plants in the field, one must fold the upper leaves out of the way and examine the fruits for two large seeds surrounded by leafy bracts.