Carex Working Group

The Carex tiogana controversy (March 2008)

Carex tiogana was described recently (Taylor and Mastrogiuseppe 1999) from high mountains near Yosemite National Park. It is a dwarf, alpine relative of C. capillaris with small perigynia and relatively prominent “spines” (stout but tiny hairs) on the leaf margins and tips and the pistillate scale midribs. It seems restricted to calcareous substrates botanists have found additional populations by using geological maps to select potential sites.

Carex capillaris itself is not found in California, but does occur in the Wallowa Mountains of northeast Oregon and in the mountains of northern Washington. Its Californian relative C. tiogana may have been isolated for millennia.

Carex Working Group members collected dwarf Carex capillaris/tiogana-like plants in alpine cirques on Steens Mountain in 2001, and a few years later Peter Zika revisited the sites and collected more samples. This find sucked the Carex Working Group into the C. capillaris taxonomic controversy vortex.

Carex capillaris is variable enough that it is sometimes divided into subspecies (two to four of them) or species. Flora of North America (FNA) recognizes two species that perhaps intergrade somewhat; boreal C. capillaris up to 60 cm tall, with 2 4 lateral spikes, the terminal spike usually staminate, and the perigynia 2.3 3.5 mm long; and arctic/alpine C. krausei up to 15 (-35) cm tall, with usually 4 10 lateral spikes, the terminal spike usually gynecandrous, and the perigynia 1.5 3.3 mm long.

Carex tiogana was originally described as being up to 7.3 cm tall (with leaves longer than culms), with usually 2 3 lateral spikes, the terminal spike staminate and the perigynia (1.2-) 1.3 1.8 (-1.9) mm long. In other words, it has the staminate terminal spikes of C. capillaris and the tiny perigynia of C. krausei. Dean Taylor (pers. comm.) has said that recently discovered populations have increased the known variability of C. tiogana.It can be up to about 15 cm tall. Distinctive traits of C. tiogana include the translucent or whitish pistillate scales (brown in both C. capillaris and C. krausei,but sometimes quite pale in C. capillaris) and the “spiny” edges and midribs of leaves (down to mid-length or lower) and midribs of pistillate scales. Carex capillaris can have “spines” on the margins and midrib at the leaf tip and, rarely, along the midrib of the pistillate scales but if present these “spines” are less dense and shorter than in C. tiogana . The “spininess” of C. tioganalooks like an intensification of the C. capillaris condition, made more conspicuous because all the other plant parts in C. tiogana are miniaturized.

Should C. tioganabe considered a species or a part of C. capillaris? Taylor and Mastrogiuseppe argue that although some C. capillaris plants may have one or another of the traits they consider typical of C. tiogana, the combination of traits observed in C. tiogana is unique. Principal components analysis (PCA) based on 31 morphological traits found that Californian C. tiogana was distinct. Geological evidence suggests thatC. tiogana may have been isolated from C. capillaris ancestors for at least 120,000 years. They have a good point.

Other botanists argue that C. tiogana should be considered merely an alpine ecotype of variable C. capillaris. None of its traits are unique. (Well, the small perigynia are shared with arctic C. krausei, not C. capillaris itself, but those taxa aren’t cleanly differentiated.) Its most distinctive traits are seen again in arctic plants living in habitats similar to those of alpine C. tiogana, so those traits may result from local selection pressures that may have little to do with speciation. These botanists consider Carex tiogana is just one more local oddity in a highly variable species. They have a good point, too.

When we wrote our Field Guide to the Sedges of the Pacific Northwest, we wavered about the taxonomic status of C. tiogana. First we treated it as a species. Then we were swayed by the arguments for lumping it with C. capillaris. (At that point, the book went to press.) Now we think it better to treat geographically isolated C. tioganawith its unique combination of traits as a species.

If we recognize C. tiogana, the next question is, are the Steens Mountain plants C. capillaris or C. tiogana? In general, the morphology fits C. tiogana, though it stretches the range of measurements somewhat. Culms are 1.1 14 cm long, and the longer culms (more than 3 cm long) are longer than the leaves. Leaves are 1.5 3 mm wide. Lateral spikes have 3 11 perigynia each. Perigynia are 1.6 2.2 mm long, usually abruptly but sometimes more gradually tapering to the beak tip. Their habitat is similar to C. tiogana habitat in the central Sierra Nevada (rocky benches with thin soil kept wet by snowmelt) but the substrate is different. However, limestone-inhabiting plants of the Sierra Nevada may be restricted to limestone because of the competition with other plants that can’t live on it, not because they require limestone. All in all, the Steens Mountain plants are like C. tiogana but somewhat intermediate between that taxon and more typical C. capillaris.

To summarize: The Carex Working Group now treat C. tiogana as a species (though we understand opposing arguments) and we think that the isolated Steens Mountain plants are C. tiogana(though they are not growing on limestone). But we might be wrong.

(Update, June 2008. We are growing a Steen Mountain plant in a pot in Corvallis, Oregon. The plant was collected in 2007. This spring the small plant produced very C. tiogana-like fertile shoots about 12 cm tall with tiny perigynia. Now the pot is producing some very large sterile shoots but are they from the same plant or another species such as C. haydeniana? We hope to have another update next year.)

Key to distinguish C. capillaris from C. tiogana:

1a. Plants from Steens Mountain or south of there; perigynia (1.2-) 1.5 2.2 mm long, usually abruptly contracted to the beak that is usually 0.3 0.7 mm long; pistillate scales usually colorless to whitish with strongly scabrous green or gold midrib; habitat alpine C. tiogana

1b. Plants from the Wallowa Mountains or north or east of there; perigynia (1-) 2.2 4+ mm long, gradually tapered to the beak that is 0.5 2.0 mm long; pistillate scales pale or medium brown with midrib usually smooth; habitat montane to subalpine C. capillaris

Reference: Taylor, Dean W., and Joy Mastrogiuseppe. 1999. Carex tiogana (Cyperaceae), a new sedge from the Sierra Nevada, California. Novon 9: 120-123