Spartina densiflora Brongn., Voy Monde 2(2): 14. 1829.

Saarela, Jeffery M., 2012, Taxonomic synopsis of invasive and native Spartina (Poaceae, Chloridoideae) in the Pacific Northwest (British Columbia, Washington and Oregon), including the first report of Spartina xtownsendii for British Columbia, Canada, PhytoKeys 10, pp. 25-82 : 40-42

Spartina densiflora Brongn., Voy Monde 2(2): 14. 1829.

Spartina densiflora Brongn., Voy Monde 2(2): 14. 1829. Type. CHILE. D’Urville s.n. (holotype: P [P02243277!]; isotype: US [US92018!] (fragm. ex P & photo)).

Chauvinia chilensis Steud., Syn. Pl. Glumac 1: 362. 1854. Type. CHILE. Concepcion, J.S.C.D. D’Urville s.n. (holotype: P [P02243276!]; isotype: US [US865687A!] (fragm. ex P)).

Description.

Culms to 96 cm tall, cespitose from hard knotty bases, rarely with short rhizomes, forming dense tufts. Sheaths glabrous, often purple-tinged; ligules 1-2 mm long; blades to 32 cm long × 1-2 mm wide, involute for most or all of their length, wider proximally when flat, adaxial surfaces scabrous, abaxial surfaces glabrous, margins scabrous. Inflorescences 10.5-17 cm long × 6-8(-10) mm wide at midpoint, with (2-)6-9(-15) branches; branches 3-6(-7.5) cm long × 2-3 mm wide, appressed, conspicuously decreasing in length towards inflorescence apex, rachises 0.8-1 mm wide between spikelets, not extending beyond terminal spikelet, glabrous, margins glabrous or scabrous. Spikelets 9-13 mm long × 1.5-2 mm wide, tightly appressed, strongly overlapping; calluses 1-1.5 mm long. Glumes glabrous or scabrous, when present hairs <0.1 mm long, keels scabrous, teeth 0.1-0.2 mm long, margins usually purple-tinged; lower glumes 4-7 mm long × 0.5-0.7 mm wide, 1-veined; upper glumes 7.5-11.5 mm long × 1-1.5 mm wide, 1-veined; lemmas 6-9 mm long, glabrous or minutely scabrous, keels scabrous distally, glabrous proximally; paleas exceeding lemmas by 0.5 mm, glabrous; anthers 3-4 mm long, yellowish, exserted at maturity, pollen fertile. 2 n = 70 ( Ayres et al. 2008, Fortune et al. 2008)

Common name.

Austral cordgrass.

Etymology.

The epithet densiflora refers to the densely-flowered inflorescences of the species.

Illustration.

Barkworth 2003:251.

Distribution.

Native to South America in temperate coastal regions of southern Brazil, Uruguay, Argentina, and on the coast of Chile ( Bortolus 2006). Introduced in Spain, Portugal, the Mediterranean (see Castillo et al. 2000, Nieva et al. 2005), United States (California, Washington), and Canada (British Columbia).

Comments.

The taxonomy, biogeography, and natural history of Spartina densiflora is reviewed by Bortolus (2006). The synonymy presented here is not complete; several taxa described from South America are considered to be synonyms by Mobberley (1956), including Spartina montevidensis Arech. (see Carrasco et al. 2002 for the location of a probable type specimen), Spartina patagonica Speg., and several taxa described by St-Yves (1932). A modern taxonomic revision is needed for Spartina densiflora to clarify its taxonomy and morphological variation throughout its range ( Bortolus 2006), particularly given its rapidly increasing global footprint.

In North America, Spartina densiflora is present in California, Washington, and British Columbia. It was first established in California. It occurs in Humboldt Bay, where it is thought to have been introduced by shipping in the late 1800s ( Spicher and Josselyn 1985, Kittleson and Boyd 1997). Prior to the early 1980s, this population was erroneously thought to be a native form of Spartina foliosa ( Bortolus 2008), and seed collected from plants growing in Humboldt Bay was introduced to San Francisco Bay (see Faber 2000), and independently to Richardson Bay. Hybrids between Spartina densiflora and Spartina foliosa have been confirmed recently from San Francisco Bay in a region where both parental species are present ( Ayres et al. 2008). These are not well characterized morphologically in the literature.

Spartina densiflora was documented in Washington a decade ago. The first collection was made in 2001 on Whidbey Island at the northern boundary of Puget Sound (Heimer 01-1 WTU, UBC). Caplow (2002) reported a 1/10 acre infestation of Spartina densiflora at the west end of Grays Harbor (46.9408°N, 124.04583°W) in the southeastern part of the state. By 2006 this infestation had expanded substantially, covering some 10 acres ( Murphy et al. 2007). Kozloff (2005) included Spartina densiflora in his Spartina treatment, noting only 'coastal salt marshes’ as its distribution.

Spartina densiflora is now invading British Columbia, where it was first found in 2005 in Bayne’s Sound, a channel between Vancouver Island and Denman Island ( Morgan and Sytsma 2010). It is not reported for the province in several recent floras that consider the region ( Douglas et al. 2001, Barkworth 2003, Kozloff 2005), but is included in the online E-Flora BC ( Anonymous 2011). In the Bayne’s Sound region, only a few herbarium collections documenting the species have been made; these are from Fanny Bay (Lomer 5723, CAN, Fig. 6 ) and the Buckley Bay Ferry Terminal (Lomer 7377, CAN). Some data on the extent of the invasion are given by Morgan and Sytsma (2010) and Dresen et al. (2010), who mapped the species in Bayne’s Sound where the extent of its local distribution ranges from individual plants to multiple five meter patches. Detailed characterization of this invasion has not otherwise appeared in the literature.

Morphology.

The description presented here is based on the few specimens that have been collected in Washington and British Columbia and deposited in herbaria (see Specimens Examined). Variation in some characters, particularly vegetative characteristics such as leaf length and culm height, is probably greater than recorded here. For example, Mobberley (1956) reported that culms in the species range to 1.5 m tall. For a description based on material from the native range of Spartina densiflora , see Mobberley (1956).

Spartina densiflora can be distinguished from Spartina alterniflora , Spartina anglica , and Spartina xtownsendii by the following combination of characters: plants cespitose [vs. strongly rhizomatous]; blades involute for all or most of their length [vs. blades flat proximally, involute distally]; blade margins scabrous [vs. blade margins smooth]; branch rachises not prolonged beyond the terminal spikelet [vs. branch rachises prolonged beyond the terminal spikelet as a bristle, rarely not prolonged]; glume margins often purple-tinged [vs. glume margins whitish, not purple-tinged] ( Fig. 7 ); and spikelets tightly appressed and strongly overlapping, concealing the rachis between spikelets [vs. spikelets weakly appressed and weakly to moderately overlapping, with portions of the rachis usually visible between spikelets]. In the field, the leaf margins of Spartina densiflora may feel smooth to the touch, as the involute blades often conceal the leaf margins where the scabrous teeth are located; these scabrous teeth are best observed with a microscope (F. Lomer, personal communication, 2012). Spartina densiflora is readily distinguished from Spartina gracilis , Spartina patens , and Spartina pectinata by its cespitose habit [vs. rhizomatous].

Specimens examined.

Canada. British Columbia: Vancouver Island, Fanny Bay, 500 m N of Waterloo Creek, 49°28.572'N, 124°47.494'W, 24 August 2005, F.Lomer 5723 (UBC, Fig. 6 ); Vancouver Island, 20 km south of Courtenay, Buckley Bay Ferry Terminal, north side of dock at high tide level, single clump, sea level, 49°31'32"N, 124°50'54.5"W, 12 July 2010, F.Lomer 7377 (CAN, Suppl. Fig. 23). United States of America. Washington: Island Co.: Whidbey Island, near Coupeville (T32E R2E S37), 14 Nov 2001, D.Heimer 01-01 (UBC [UBCV224048, Suppl. Fig. 24], WTU [WTUb349303, Suppl. Fig. 25]).

Figures

Figure 6. Photograph of a specimen of Spartina densiflora collected at Fanny Bay, Vancouver Island, British Columbia (Lomer 5723, UBC). Image published with the permission of the University of British Columbia Herbarium, Beaty Biodiversity Museum.

Figure 7. Spikelets of Spartina densiflora (Canada, British Columbia, Lomer 5723, UBC). Bar = 3 mm. Photo: J. M. Saarela.