Scouleria siskiyouensis (Scouleriaceae), A New Rheophytic Moss Endemic To Southern Oregon, USA

2014·9.9 MB·English

by  James R Shevock

Madrono, VoL 61, No. 1, pp. 137-143, 2014
SCOULERIA SISKIYOUENSIS (SCOULERIACEAE), A NEW RHEOPHYTIC MOSS
ENDEMIC TO SOUTHERN OREGON, USA
James R. Shevock
California Academy of Sciences, Department of Botany, 55 Music Concourse Dr., Golden
CA
Gate Park, San Francisco, 94118-4503
shevock@calacademy org
j .
Daniel H. Norris
University Herbarium, 1001 Valley Life Sciences Building, University of California,
CA
Berkeley, 94720-2465
Abstract
Scouleria siskiyouensis Shevock & D. H. Norris, a new species restricted to rivers and streams in
southwestern Oregon is described and illustrated. This species appears related to the widespread S'.
aquatica Hook, in Drummond ofwestern North America but is distinguished by a combination of
featuresincludinglaminabistratoseexcept forafewcellsatimmediate leafmargin unistratose, leaves
lanceolate to ovate-lanceolate and with leafapex acute to acuminate.
Key Words: Aquatic mosses, rheophytes, Scouleria aquatica, Scouleria marginata.
Scouleria Hook, is a very distinctive genus of leaves. These two species rarely grow sympatri-
rheophyticmosses. Described by Hookerin 1829, cally. Scouleria marginata prefers larger river
the dark coloration and growth habit resem- systems and generallylowerelevations whereas S.
blance to certain rheophytic Racomitrium Brid. aquatica has a much broader range ofecological
s.l. {Codriophorus P. Beauv. and Bucklandiella attributes occurring from near sea level to the
Roiv.) and Schistidium Bruch & Schimp. species headwaters oftributary streams.
probably contributed to its initial placement by For over 150 yr Scouleria remained in the
early bryologists in the Grimmiaceae. The Grimmiaceae but the largelymorphological work
presence of systylious capsules is also similar to conducted by Churchill (1985) convincingly
species of Schistidium. Scouleria is immediately elevated Scouleria to family status. Recent
recognized in the field by its habitat (aquatic in molecular evidence also supports the recognition
rapidly flowing streams and rivers); by its size of this family of rheophytic mosses (Tsubota
and coloration (drying nearly black with leaves et al. 2003; Carter et al. 2014).The other genus
mm
mostly about five or more broad); and by its attributed to this family, Tridontium Hook, f., is
capsule morphology (nearly sessile, large and monospecific, and is endemic to Australia and
globose with very thick capsule walls and New Zealand. Scouleria is a genus that is easily
presence ofa columella). recognized in the field. It is restricted to rapidly
As a rheophytic genus, Scouleriahas one ofthe flowing unpolluted rivers and streams where
most unusual distributions of bryophytes: west- plants are seasonally submerged then exposed
ern North America, North Asia (Siberia and the on boulders and rock walls as rivers decrease in
Russian Far East), and southern South America flow. When hydrated, Scouleria is dark green in
(Churchill 2007). In North America, Scouleria color but upon drying becomes nearly black.
primarily occurs along the Pacific Slope from Scouleria generally occurs in large patches and
Alaska to California with scattered disjunct when in a dry state these blackened Scouleria
populations inward to Montana but is not found populations can be recognized on large boulders
in the eastern half of the continent. Only two and rock walls from a distance ofseveral meters.
species of Scouleria have been recognized for On a worldwide basis all members of Scouleria
North America. These two species are readily seem to be the ultimate rheophyte, annually
recognized in the field by a hand-lens examina- receiving severe scouring during peak flows when
tion ofthe leaf border. In Scouleria aquatica the sediment yields are increased, deep submersion,
border is merely thickened but flat caused by an extended period in white water rapids,
either enlarged cells or by the development of a followed by a period ofdesiccation during which
bistratose layer at the margin. However, in they are generally exposed in full sun during the
Scouleria marginata E. Britton, the margin hottest months ofthe year.
appears inflated and rounded due to thickened All species of Scouleria have a prominent
multistratose cells along the margin forming a morphologic feature that exhibits an unusual
more prominent border, especially seen on older structure for a moss leaf. In addition to the usual
MADRONO
138 [VoL 61
feature of alar cells and median laminal cells in S. marginata, a species endemic to the Pacific
(isodiametric and thick-walled in Scouieria) there Slope of North America from British Columbia
is an area of several rows of elongate and to California with isolated populations in Idaho
glistening white-walled cells which is seen as an and Montana (Lawton 1971; Christy et al 1982;
intramarginal limbidium. This intramarginal lim- Churchill 1985, 2007; Norris and Shevock2004a).
bidium seems to be unique to the genus but its Kurbatova (1998) states that the seta is longer in
prominence varies greatly from leaf to leaf even S. aquaticavar.puicherrima, butwehavenot seen
on a single stem. Some leaves may have only a Russian Scouieria with capsules for comparison
few cells between the alar and median cells while to North American taxa.
other leaves may have an intramarginal limbi- Fieldwork contributing toward a bryoflora of
dium that comprises most ofthe area ofthe leaf. California (Norris and Shevock 2004a) led to the
The variability in the prominence of the intra- collection of many bryophytes, especially from
marginal limbidium does not seem to be related the northern extension ofthe California Floristic
to species differences within the genus, and it Province within southern Oregon. This area is
seems also unrelated to apparent habitat differ- well-known as one of the biodiversity hot spots
ences. This limbidium although often is the for vascular plants and contains a high level of
dominant visual feature ofsome leaves apparent- endemism (Norris 1997). The area of the
ly has no taxonomic importance beyond merely Kaimiopsis Wilderness on the Siskiyou portion
signaling the generic identification. An additional of the Rogue River-Siskiyou National Forest is
genericcharacter for Scouieria is the frequency of exceptionally important as an evolutionary refu~
rhizoids on the abaxiai base ofthe costa. gium. The same area is also rich in bryophyte
While the genus is easy to determine, the diversity. Following examination of Scouieria
recognition of species has been more difficult. collections from that general region it was
The actual number of species based solely on determined that an undescribed species was likely
morphological features has ranged from three to at hand based on vegetative leaves that are
five species, and part of this recognition was strikingly more lanceolate and acute at apex.
based on geography rather than a good set of Under a compound microscope, a cross section
morphologicalcharacters. Likemanyrheophytes, displayed far greater development ofbistratosity
the aquatic growth form creates a large array of across the lamina than seen previously in the
morphological character variations generally genus. However, describing a new Scouieria from
useful for identification purposes such as leaf North America was deemed to require a critical
shape, leaf size and leaf border. Most keys examination of S', aquatica throughout its range
developed to separate Scouieria species have including plants from the Russian Federation.
relied on cross sections of leaves to describe the Due to the view of extreme plasticity displayed
patterns and locations of various levels of among morphological features of rheophytes in
bistratosity. Crosby et ai. (2000) treat the genus general and wide variation reported within the S.
as comprised of three species; two species in the aquatica complex in particular, this issue was not
Northern Hemisphere and one in the Southern pursed further at that time although this entity
Hemisphere. However, two additional species, S. was referenced in the Scouieria key as "species A’
rschewinii Lindb. & Arnell described in 1890 and (Norris and Shevock 2004b). Eventually a molec-
S. puicherrima Broth, described in 1916 from ular studywas initiated to determine the affinities
Siberia and the Russian Far East were subse- of Scouieria within its geographical range. That
quently reduced to synonymy within the geo- study (Carter et al. 2014) confirmed that the
graphically widespread S. aquatica (Churchill Russian species are worthy of species rank, S.
1985), As late as 1970, sporophytes were un- aquatica is restricted to North America, and that
known for these two Russian taxa (Savic- the southwestern Oregon plants represent a
Ljubickaja and Smirnova 1970). However, species new to science and is described herein.
Churchill (2007) acknowledges that much varia-
tion exists within the S', aquatica complex and Taxonomic Treatment
other taxonomic arrangements at variety or
species level may be warranted through future Scouieria sisMyouensis S—hevock & D, H. Norris,
molecular study. While sporophytic characters sp. nov. (Figs. 1-2). TYPE: USA, Oregon,
can be highly informative between members Douglas Co., Coos Bay District, Bureau of
within agenus, in Scouieria capsules are generally Land Management, Middle Fork Coquille
infrequently produced, are ofshort duration and River along highway 42 west of Roseberg at
look basically the same in shape and color. Even milepost 26, former site of Bear Creek Recre-
when capsules are present on herbarium speci- ationArea,T30S, R9W, section9,42°58'9.2"N,
mens they are rather fragile and peristome teeth 123°45'57.8''W, 850 ft, 19 Mar 2005, Shevock
or their remnants are easily lost or detached. The and Keiiman 26365 (holotype: CAS; isotypes:
only distinction in capsule morphology described H, HYO, KRAM, MHA, MO, NY, OSC,
in the genus to date is the lack ofperistome teeth UBC, VBGI, UC).
2014] SHEVOCK AND NORRIS: NEW RHEOPHYTIC MOSS 139
Fig, 1. ScouieriasiskiyouensisShevock&D. H.Norris. 1„ Fertileplant,wet. 2. Portionofstemtransversesection.
3-6. Leaves. 7-14. Leaftransverse sections. (Allfrom Shevock26365, isotype, KRAM). Scale bars: a- 100 jam (7-
14); b - 1 mm (3-6); c - 100 pm (2); d - 0.5 cm (1).
MADRONO [VoL 61
140
Fig 2. Scouleria siskiyouensis Shevock & D. H. Norris. L Fertile plant, dry. 2-3. Leafapices. 4. Middeafcells.
51.2.MiOdpedrecauflacetlelscaatpsmualregiwni.th6.cBaalsyaptlraa,ngwuelta.rc1e3l.ls.Op7e.rBcauslaaltejucxatpascuolset,alwceetl.ls.148--1150.. PYeoriucnhgaetsiyasltylleiaovuess.c1a1p.suCkalsy,ptdrray..
16. Old capsules with destroyed peristome, dry. 17. Exothecial cells at base ofurn. 18. Mid-urn exothecKiaRlAcMel)ls..
S1c9.alEexobtarhse:ciaal—ce1llmsmat(o1r,if1ic1e—1a6n);dbpo—rt1iomnmof(p8e—r1i0s)t;omce—. 2100-024p.mSp(o1r7e—s24.)(;Aldl—fr1o0m0Sphmev(o2c—k7)2.6365, isotype,
1
2014] SHEVOCK AND NORRIS: NEW RHEOPHYTIC MOSS 141
Plants aquatic, usually in rapid water of Creek Falls, Rogue River-Siskiyou National
streams and rivers, often ratherclosely branched, Forest, 165 ft, 21 Mar 2005, Shevock 26421
mostly to 8 cm long. Plants dark green to (CAS, CONC, H, KRAM, LE, MO, NY, UBC,
brownish-green in younger portions, glossy black UC); Same location, 14 Jun 2005, Wagner ml697
in olderportions, frequently with most ofthe leaf (CAS, OSC); Myrtlewood Grove Campground,
laminae removed by water scouring, leaving only 375 ft, 21 Mar 2005, Shevock 26438 (CAS, MO,
the costa. Leaves to 5 mm long, 1.5-3,5: 1, not NY, UC). CurryCo.: ElkRiverRoad about 17mi
decurrent. Leaf apex acute to acuminate with E of highway 101, Rogue River-Siskiyou Na-
apex not cucullate. Leaves broadly keeled above tional Forest, 8 Mar 1972, Norris 21977 (UC);
midleaf. Leaf margins serrulate to serrate to Elk River Road about 17 mi E of highway 101,
finely dentate, usually plane. Leaves mostly Rogue River-Siskiyou National Forest, 8 Mar
bistratose, but with margins unistratose for 1972, Norris 21979 (UC); about 10 mi SE of
several cells along the border. Laminal cells of highway 101 east of Port Orford, 300 m, 25 Jan
median limb isodiametric, about 10 pm or nearly 1995, Norris84649 (CAS, H, LE, UC); Elk River
so, smooth. Laminal cells ofmedian portions of Road 1.4 mi E of fish hatchery, 530 ft, 1 Mar
the sheathing base to 12 pm broad, short- 2013, Shevock 41901 (CAS, CONN, DUKE, E,
rectangular, mostly 2-3: 1, thick-walled with F, H, KRAM, LE, MHA, MO, NY, OSC, UBC,
lumen; wall ratio 1-2: 1, mostly not pitted. Costa UC, US); Bear Creek at confluence with Elk
on adaxial side having 6-8 cell rows ofrectangu- River 2.2 mi E of fish hatchery, 550 ft, Shevock
lar epidermal cells, filling more than 20% ofleaf, 41906 (BOL, CAS, COLO, CONC, E, H, KUN,
tapering very little to the subpercurrent apex, MO, NY, OSC, UC); Bear Creek at confluence
with rhizoids cloaking its abaxial basal 1/5 or with Elk River 10 mi E of fish hatchery, 850 ft,
more. A broad and almost white to pale infra- Shevock 41910 (CAS, CONC, CONN, H, HO,
marginal limbidium usually present, often re- KRAM, L, LE, MHA, MO, NY, OSC, TNS,
stricted to proximal one quarter of leaf, but UBC, UC, US); Redwood State Park about 8 mi
sometimes extending to near leaf apex with this E of Brookings, along Chetco River, 3-9 Sep
variability in extent shown even on leaves of the 1950, Koch 3245 (UC); Redwood State Park
same clone. Axillaryhairs 5-6 cells longto 100 pm about 8 mi E of Brookings, along Chetco River,
with 2 short but concolorous basal cells, cylindric 3-9 Sep 1950, Koch 3270 (UC); Redwood State
and ofconstantdiameterthick-walled (lumen: wall Park about 8 mi E of Brookings, along Chetco
ratio 1.5-3: 1). Rhizoidsred-brownwithsomewhat River, 3-9 Sep 1950, Koch 3290 (UC); Chetco
warty surfaces, to 35 pm in diameter at insertion, River, Siskiyou National Forest, T39S, R12W,
mostly on oldest parts of stem, and also on the SI3, 400ft, 17 Oct2002, Jones3954 (OSC); South
adaxial face of the costa, mostly below mid-leaf. Fork Chetco River just above confluence with
Plants presumed dioicous, perigonia not seen; Chetco River, at milepost 8, Rogue River-
perichaetial leaves generally reduced in length Siskiyou National Forest, 155 ft, 19 Jan 2013,
and width compared to vegetative leaves. Seta Shevock and Lambio 41752 (BOL, CAS, COLO,
mostly less than 1 mm long straight and smooth DUKE, E, F, H, HO, KRAM, L, LE, MHA,
emerging from a short vaginulum with a heavy MO, NY, OSC, UBC, UC, US); Winchuck River
cover ofparaphyses; calyptra covering halfor less at forest boundary, 0.5 mi west of Winchuck
of maturing capsule, cucullate, smooth, naked. Campground, Rogue River-Siskiyou National
Capsule systylious, mostly 2.5-3 mm long, nearly Forest, 175 ft, 19 Jan 2013, Shevock and Lambio
globose when young and operculate but shrinking 41759 (CAS, CONC, H, KRAM, LE, MHA,
and becoming ring-like after dehiscence of apicu- MO, NY, OSC, UBC, UC). Josephine Co.: South
late operculum, then becoming 2-3 times broader Fork Taylor Creek along forest road 25 near Tin
than tall with the longitudinally ribbed columella Can Campground, Rogue River-Siskiyou Na-
occupyingthecentralaxis ofthe shortenedcapsule tional Forest, 1000 ft, 28 Feb 2013, Shevock and
and with the spores surrounding that columella. Loring 41881 (CAS).
Median exothecial cells to 15 pm wide, 1-2.5:
rather thick-walled, arranged in regular longitudi- Taxonomic Relationships
nal rows. Peristome of32 fragile, short, triangular
teeth, to 400 pm long, reddish when young, aging Scouleriasiskiyouensishasgoneundetecteddue
brown, inserted 1-2 cells below mouth ofcapsule, to its similarity to other Scouleria species in
smoothwith prominentdorsal trabeculae, blunt at southern Oregon. The plants form robust colo-
apices, reflexed when dry, slightly incurved when nies similar in appearance to populations of
wet. Teeth cover only a very small portion ofthe both S. aquatica and S. marginata. These taxa,
capsule mouth. Spores spherical, generally light however, are readily separated. When sporo-
brown, to40pmindiameter, ornamentedwithlow phytes are present, S. siskiyouensis has 32 fragile
anastamosing ridges. peristome teeth reflexed on the mouth of the
Paratypes: USA, OREGON. Coos Co.: South capsule while peristome teeth are absent in S.
Fork Coquille River along forest road 33 at Elk marginata. Gametophytically the leaves in S.
MADRONO
142 [VoL 61
i
siskiyouensis are primarily bistratose across the while sporophytes are maturing. However,
median region butcells adjacent to the border are among North American Scouleria, S. siskiyouen-
unistratose. Scouleria marginata on the other sis produces sporophytes considerably more
hand is unistratose across the lamina (rarely with frequentlywithmaturecapsules appearingduring
bistratose streaks) but the leaf margins are the winter season and sporophytes also appear to
multistratose and appear considerably thickened develop in series as water levels fluctuate between
called ‘pseudocostae’ by Churchill (1985). Scou- winter storms. Sporophytes of Scouleria sis-
leria aquatica resembles S. siskiyouensis but it is kiyouensis have been observed in all of the
generally smaller in stature with a more rounded populations documented to date. In S. aquatica
leaf apex. Sporophytes appear to be identical and S', marginata, sporophytes are generally
between these two species although they are produced later in the year depending on eleva-
exceedingly more common in S. siskiyouensis tion, however, based on our field observations
compared to S. aquatica. A leaf cross-section is both species produce sporophytes more frequent-
the most reliable method of species recognition ly in Oregon than in adjacent California.
between these related taxa. Scouleriaaquaticacan Among rheophytic mosses the peristome teeth
be distinguished from S. marginata by the in Scouleria are rather unusual. The role of the
marginal cells of the vegetative leaves that are peristome is traditionally understood as a means
in only one layer or occasionally with bistratose offacilitating spore dissemination by opening of
streaks and are somewhat enlarged and thin- the capsule mouth at times when environmental
walled compared to the 4+ layers of stereid like conditions are favorable for spore release. Peri-
cells in S. marginata. This feature of having stomate bryophytes differ in the patterns of
multistratose borders can be observed with a reflexing and inflexing generally based upon
hand-lens in S. marginata. Scouleria aquatica has ambient humidity. In Scouleria, the peristome
peristome teeth, which differ from the eperisto- seems to haveneitherfunction. Peristometeethin
mate S. marginata. Based on a recent molecular Scouleria are so small and fragile that they are
study (Carter et al. 2014), Scouleria siskiyouensis unlikely to carry their unusually large spores
is sister to S. aquatica. toward thecapsule mouth to aid indispersal. The
mouth of the capsule is exceedingly broad in
Habitat and Ecology relation to the tiny ring of peristome teeth, and
therefore, these teeth provide no means of
Scouleria siskiyouensis is restricted to fast restriction of the capsule mouth. The release of
flowing, unpolluted rivers and streams with large spores in Scouleria actually occurs when the
boulders. Plants seem to require seasonal sub- systylious globose capsule shrinks longitudinally
mergence, an extended period in the splash zone, from the operculum and columella like a donut
then a period of complete desiccation. Several causing the bulk ofthe spores to be forced out by
other rheophytic mosses can be associated with this compression action. The remaining spores
Scouleriasiskiyouensis. Scleropodium obtusifolium lodged in thebase ofthe capsule are disseminated
(Mitt.) Kindb. and to a lesser degree Codrio- as the capsule wall disintegrates. Additional
phorus aciculare (Hedw.) P. Beauv. and Schisti- spores can also are removed from the opened
dium rivulare (Brid.) Podp., are themostcommon capsules in the event water levels rise again after
associates. Scouleria is a genus that requires capsule dehiscence. The peristome teeth in
seasonal submersion, cold, clean water, and Scouleria are but mere ornamentations and seem
periods of desiccation during the dry summer to be a useless structure, normally reflexed along
months. Changes in such hydrologic function the capsule wall. Of the six species of Scouleria
could rapidly cause the extirpation ofthis species worldwide, peristome teeth have been lost in only
from those locations. Scouleria can also be very S. marginata.
localized even in river and stream systems where
it occurs. Plants are found on large boulders or Distribution
walls ofbedrockmicro-siteswheretheycannot be
displaced during floods or periods ofpeak flows. Populations of Scouleria siskiyouensis are
Populations can occupy up to a meter wide band currently restricted to southwestern Oregon,
in the water column depending on river flow. primarily in the Siskiyou portion of the Rogue
Generally, Scouleria occurs just below the high River-Siskiyou National Forest within the Coast
water zone. A period of time in the splash zone Range Ecoregion. Population elevations range
among white-water rapids appears to be critical from 150 to 1000 feet. This species is a very
for the establishment ofsporophytes. Being both narrow rheophytic endemic with the distance
dioicousand arheophytemayaccountforlimited between the northern and southern occurrences
success ofsporophyte production. As an aquatic being only 68 air miles. We anticipate additional
moss, fertilization has to occur while the plant is populations of S. siskiyouensis within this range
hydrated and free water is readily available and will be discovered as more bedrock river and
plants need to stay hydrated (in the splash zone) stream habitats are surveyed along the western
2014] SHEVOCK AND NORRIS: NEW RHEOPHYTIC MOSS 143
and northern boundaries ofthe Siskiyou portion Acknowledgments
aodfjtahceenRtoBguLeMRiCvoeors-SBisakyiyDiosutrNiacttiloannadls.FoArletshtoaungdh wonWdeertfhualnkillHuasltirantaioBnedplnaatresekf-oOrchtyhirsarfeomraprrkoadbulceinpglatnht.e
the southernmost Oregon occurrence along the ColleaguesDavidWagnerand ScotLoringprovideddata
Winchuck River isjust 1.75 air miles north ofthe on Oregon Scouleria populations and specimens for
California/Oregoe border, we are of the opinion whichwearemostgrateful. Aloan ofOregon Scouleria
that locating a California occurrence may be from OSC was very helpful in determining species ranges
limited. We were unable to locate S. siskiyouensis and is appreciated. We also thank the various land
during field sampling in the adjacent Smith River management agencies for collecting permits to develop
watershed in California although both N. aqua- baseline data on California and Oregon bryophytes,
tica and S. marginata are present but as small, primarily the Rogue River-Siskiyou and Six Rivers
isolated populations. The riparian zone within National Forests. Comments provided by David Wagner
the Smith is not optimum habitat for the new andtwoanonymousreviewersenhancedthefinalversion.
Scouleria taxon due to the dominance ofserpen- Literature Cited
tine geology resulting in less riparian vegetation
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2014. Arevisitationofspeciescircumscriptionsand
evolutionary relationships in Scouleria (Scouleria-
Conservation Implications
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zaki, Japan.
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peristome teeth..........Scouleria aquatica USSR. The Komarov Botanical Institute, Lenin-
2'. Leaf margins prominently thickened grad, Russia.
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