FAU Institutional Repository http://purl.fcla.edu/fau/fauir This paper was submitted by the faculty of FAU’s Harbor Branch Oceanographic Institute. Notice: ©1980 Elsevier B.V. This manuscript is an author version with the final publication available at http://www.sciencedirect.com/science/journal/03043770 and cited as: Eiseman, N. J., & McMillan, C. (1980). A new species of seagrass, Halophila johnsonii, from the Atlantic coast of Florida. Aquatic Botany, 9, 15‐19. doi:10.1016/0304‐3770(80)90003‐0 ,~ \'1 \ Aqu.ti,Bowny. 9(198~" t'fIJJ1 .".~ Elsevier Scientific Publishing Company; Amsterdam - Printed in The Netherlands A NEW SPECIES OF SEAGRASS, HALOPHILA JOHNSONII, FROM THE ATLANTIC COAST OF FLORIDA N.J. EISEMAN Harbor Branch Foundation, Fort Pierce, FL 33450 (U.S.A.) CALVIN MCMILLAN Department ofBotany and Plant Ecology Research Laboratory, Uniuersity of Texas at Austin, Austin, TX 78712 (U.S.A.) (Accepted 21 January 1980) ABSTRACT Eiseman, N.J. and McMillan, C., 1980. A new species of seagrass, Halophila johnsonii, from the Atlantic coast of Florida. Aquat. Bot., 9: (5-1-9. Plants that occur in shallow lagoons from Sebastian Inlet to Biscayne Bay on the Atlantic coast of Florida are described as a new species, Halophila johnsonii, in section Halophila. Pistillate flowers have been observed from April to July and fruits in August, but staminate flowers have not been collected, suggesting that H. johnsonii may be apomictic. The plants have previously been referred to as H. decipiens Ostenfeld, a pantropical spe­ cies that is found at depths of 20 m on the continental shelf along the Atlantic coasts of Florida. INTRODUCTION There has long been confusion over the species of Halophila present in Florida. The Indian River lagoon on the Atlantic Coast of Florida was ex­ plored for seagrasses by Phillips (1960) who referred plants described here as a new species to H. baillonis Aschers. Den Hartog (1970) in "The Sea-Grasses of the World", included the reference by Phillips in the synonymy for H . decipiens Ostenfeld but did not cite any specimens from the Indian River. All of the Florida specimens examined by den Hartog were from deeper wa­ ter (18-32 m) in the Florida Keys . Phillips (1960) included a photograph, referred to by den Hartog (1970), of plants collected in the Indian River near St. Lucie Inlet and mentioned that he had also found the species in both shal­ low water, 16 km south of St. Lucie Inlet at Jupiter Inlet, and in deeper wa­ ter 18 km offshore in the Guif of Mexico, in the vicinity of Tarpon Springs. Phillips ~ 1 9 6 0 ) also cited collections by Humm (1956) from deeper water in the Gulf of Mexico as far west as Pensacola, Florida, and by Taylor (1928) from the Dry Tortugas, but did not discuss populational differences between , 0304-3Tio/80/0000-Q000/$02.25 © 1980 Elsevier Scientific Publishing Company 16 plants of the Indian River and those of deeper sites. Den Hartog (1959) has pointed out that Halophila baillonis Aschers. ex Dickie in Hook. til. should be applied to plants in section Americanae and that the plants which were included by Phillips (1960) in H. baillonis should be referred to section Halophila. Section Americanae is characterized by plants having short-shoots bearing a pair of scales halfway up and a pseudo­ whorl of 4 to 8 leaves at the top. Section Halophila has plants with extreme­ ly short shoots bearing a single pair of leaves. Den Hartog (1970) cites H. baillonis only from sites south of Florida, ranging from St. Croix in the Caribbean to Panama and Brazil. Phillips' plants from the Indian River repre­ sent another species in section Halophila. This species, described below, has since been found at a number of additional sites. Halophila johnsonii Eiseman sp. nov. Halophila baillonis auct. non Aschers.: Phillips, pro parte Florida State Board of Conservation, Prof. Pap., 2 (1960) pp. 63~4 , f. 64; Halophila decipiens auct. non Ostenfeld: Tomlinson, Aquacul­ ture, 4 (1974) 122-124, Fig. 8. Internodia caulium 1-2 em longa. Stipulae 3-4 mm longae, glabrae, margine integrae. Petioli 10-20 mm longi; laminae lineares 5-25 mm longae, 1-4 mm latae, glabrae margine integrae costis prominentis ad basin elongate cuneatae basem versus gradatim angustatae; venae transversae utroque costae latere' 5:-10 angulis 45° divergentes;juncturae venarum transversarum nervos intramarginales 0.1-0.2 mm marginibus remotae, Flores unisexuales, floribus masculinis ignotis, femineis ovariis 5 mm longis; fructus lateraliter ellipticus. Holotypus: N.J. Eiseman, May 23, 1975, ad locum Bessie Cove, Hutchinson Island, Martin Co ., Florida, dictum, lat. 27° 15' Sept., long. 800 12' Occid. lectus; numero 003411 (HBFH). Isotypus: HBFH, TEX, US. Foliage leaves two at a node, with long petioles, 10-20 mm when mature, blades linear with a very prominent midrib, slightly asymmetrical, 5-25 mm long, 1-4 mm wide, margin entire, not at all serrate, upper and lower sur­ faces glabrous, base elongate--cuneate, tapering gradually into the petiole, petiole not sheathing, secondary veins irregularly alternate to nearly opposite, occasionally anastomosing, in 5-10 pairs (Fig . 1); stem a creeping rhizome, 1 mm diameter, internodes 1-2 ern long, nodes bearing scale leaves on the upper and lower surfaces; scales keeled, tip slightly notched, surface glabrous, margin entire; roots unbranched, one at a node, arising from the base of the ventral scale leaf; female flowers sessile, enclosed in a two-leaved spathe, 5 mm long, fruits longnecked, with a spindle-shaped base, male flowers un­ known. .. Brevard County. Sebastian Inlet, in firm shelly sand in the sand trap on the north side of the inlet, Florida, 27° 51'8"N, 80027'O"W, 25 January 1975, 1975, N.J. Eiseman (HBFH). St. Lucie County. In fine sandy sediment at less than 20 em depth at low tide at Pepper Park, north of Fort Pierce Inlet, Florida, 27°29'N, 80016'W, 9 June 1979, C. McMillan 1101 (TEX). Big Mud Creek 27°21'2"N, 80° 14'9"W, 9 ApriI1975,N.j. Eiseman (HBFH). 17 Fig. 1. Holotype of Halophila johnsonii. Lower right, leafy branch showing relative size and shapes of female flower, rhizome, roots and leaves. Bracts are shown around the flower. Lower left, leafshowingvenation pattern. Top, a fertile leaf axil showing a rhizome supporting two stipular bracts, two petioles and a flower surrounded by a bract (position of the ovary and style shown within the bracts). Dade County. Along Norris Cut, north end of Virginia Key, 6 m from shoreline at low tide, clumps associated with Halodule, 2 April 1974, George Avery and P.B. Tomlinson (TEX). Halophila johnsonii most closely resembles H. oualis (R.Br.) Hook. fil. as interpreted by den Hartog (1970). However, it differs in the exclusively lin- 18 ear-lanceolate blade with an elongate--cuneate base and alternate cross venation. Halophila johnsonii differs from H. decipiens in several characteristics. Linear leaves with entire margins separate it from the oblong-elliptic leaves with serrulate margins of H. decipiens (den Hartog, 1970). Halophila john­ sonii lacks hairs on the blade surface. H. decipiens rarely lacks hairs on at least one side of the blade. The cross veins of H. johnsonii diverge from the midrib at ca . 45° angles, those of H. decipiens at ca. 60° angles . The intra­ marginal nerves of H. johnsonii are 0.1-D.2 mm from the margin. Those of H. decipiens are ca. 0.5 mm from the margin. Irregularly shaped reddish blotches may occur on both sides of the midrib and extend over the entire length of the blade of H. johnsonii. Only pistillate flowers are known for H. johnsonii and it is possibly apomictic, whereas Halophila decipiens is mono­ ecious and H. ovalis is dioecious. Halophila johnsonii is apparently restricted to the coastal lagoons in east­ ern Florida from Sebastian Inlet (lat. 27° 50') to Virginia Key (lat. 25° 45') in Biscayne Bay. It is primarily an intertidal species growing with Halodule wrightii Aschers. but may occur in pure stands. The occurrences are usually in firm substrata composed of fine sand of 3.0-3.54> size (0.88-1.25 mm). Phillips (1960) reported that the abundance of Halophila varied seasonally. He noted vast quantities in late September 1957, but only sparse amounts in March of the following year. He reported varying amounts of plants at sever­ al stations in the Indian River in October 1958, and in March 1959. Phillips indicated that water depth ranged from "six inches at slack low tide to six feet at flood tide", and that water temperature ranged from 21.0-23.0°C in March to 28.5-36.0°C in late September. The salinity varied according to .Phillips from 24 .3 to 38°ko during his different observations. The present studies indicate that H. johnsonii occurs at all times of the year and at salin­ ities of up to 43%0 . Plants near Fort Pierce Inlet were transplanted to Texas and cultured un­ der controlled conditions with populations of diverse origin in section Halo­ phila (McMillan and Williams, 1980). The diagnostic characters of H. johnsonii remained relatively unchanged in the experimental cultures. The linear leaves under laboratory conditions continued to produce intramarginal nerves that were 0.1-D.2 mm from the margin. The reddish blotching along the midrib was characteristic of all of the leaves in the cultures. Differences in leaf shape that separate H. johnsonii from H. decipiens of St. Croix were maintained in artificial seawater under growth chamber conditions. Collections of Halophila johnsonii from the Indian River near Fort Pierce Inlet have been included within recent surveys of isozymes, flavonoids and sul­ phated phenolic compounds.