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IDENTIFICATION AND TAXONOMY OF TWO DIFFICULT MARITIME HYBRIDS WITH CAREX PALEACEA

Publication Type:Journal Article
Year of Publication:2000
Authors:Haines, A
Journal:Botanical Notes
Volume:4
Start Page:1
Pagination:1-6
Date Published:12/13/2000
URL:http://static.squarespace.com/static/5369617de4b054aef368005b/t/53d9d28be4b047a1cbd79124/1406784139190/Botanical_Notes_number_4.pdf
Full Text

Members of Carex section Phacocystis are well known
for taxonomic difficulties created by interspecific
hybridization. This situation appears to be pronounced
in coastal and estuarine areas of northeastern North
America (Lepage 1956, Cayouette and Morisset 1985).
Careful research has revealed a complex evolutionary
history in this section (Cayouette and Morisset 1985,
Standley 1990). Cayoette (1987) has shown that
misapplication of Phacocystis names has occurred in
the northeast due to hybrid-derived taxa simulating the
morphology of other species. The name C. salina
Wahlenb. has commonly been applied to a set of rare
plants from coastal Maine (Fernald 1950, Gleason and
Cronquist 1991). These individuals are now known to
consist of two, stabilized hybrid derivatives—C. recta
Boott and C. vacillans Drejer ex Hartman. This note
seeks to clarify the taxonomy of the two stabilized
hybrid species and present their identifying
characteristics.
Carex section Phacocystis (including sections Acutae
and Cryptocarpae) contains primarily perennial,
wetland species of small to moderate stature. This
section belongs to subgenus Carex, as evidenced by its
mostly unisexual spikes and entire or equally bifid
beaks (Standley 1985). It is somewhat unusual,
however, in that it possesses bicarpellate gynoecia (i.e.,
two carpels per flower), a trait usually associated with
subgenus Vignea. Members of section Phacocystis
were formally divided into two separate sections—
Acutae and Cryptocarpae. The former section was
generally identified by upright, sessile spikes, nonindented
achenes, and awnless carpellate scales, while
the latter section was identified by drooping, peduncled
spikes, commonly indented achenes, and carpellate
scales with long awns. Species with intermediate
morphology do occur. The discrepant placement of
Carex torta Tuckerman—a species with arching,
shortly-peduncled lower spikes and awnless carpellate
scales—by Fernald (1950) and Gleason and Cronquist
(1991) illustrates the difficulty of drawing section
boundaries. Based on intermediate taxa and the shared
character state of bicarpellate gynoecia, these two
sections are now considered to comprise one, variable
section (Phacocystis) (Standley 1985).
DESCRIPTION OF THE PARENTAL SPECIES
Following is a brief discussion of the three parental
species. Descriptions of the ecology and morphology is
provided, with focus on characters that allow for
discrimination of the stabilized hybrid taxa.
Carex paleacea Wahlenb. inhabits coastal salt marshes
of north temperate to arctic regions of eastern North
America. In Maine, it is commonly found in
association with Juncus gerardii Loisel.,
Schoenoplectus pungens, and Triglochin maritimum L.
Its flowering stems share morphological similarity with
C. crinita Lam. (i.e., spikes borne on drooping
peduncles and carpellate scales with conspicuous,
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scabrous awns) (Figure 1). Carex paleacea differs
from its inland counterpart, however, in its possession
of long rhizomes and lack of cespitose growth form.
This marit ime species has yellow-brown carpellate
scales and short-papillose perigynia with 0–5 obscure
nerves on each face. The inflorescence is overtopped
by a long, bract that subtends the lowest spike. The
achenes of C. paleacea normally have an evident
indention on one side (Figure 2).
Figure 1. Inflorescence of Carex paleacea.
Figure 2. Illustration of Carex paleacea achene. Note
indentation on left side.
Carex nigra (L.) Reichard is usually found growing in
open, sometimes disturbed, habitats near the Atlantic
coast. This includes meadows, lawns, and roadsides of
coastal towns and provinces. Carex nigra possesses an
inflorescence with sessile, erect spikes that are usually
not overtopped by the lowest bract (Figure 3). The
carpelllate scales are dark purple-brown with a very
narrow, pale midvein. The perigynia usually bear
several conspicuous nerves on each surface and are
densely long-papillose. The beak frequently has minute
scabrules around the orifice (Figure 4).
Figure 3. Infloresence of Carex nigra.
Figure 4. Carex nigra perigynium, apical portion. The
arrow points to scabrules about the orifice of the beak.
Note also the long papillae on the perigynium surface.
Carex aquatilis Wahlenb. is a polymorphic,
circumboreal species. In Maine, it normally inhabits
open, freshwater wetlands with moderate to high
mineral soil content (i.e., it is only infrequently found in
peatlands). This species is essentially non-maritime,
however, it plays a role in Phacocystis speciation with
maritime species. Carex aquatilis, similar to C. nigra,
possesses sessile, erect spikes. However, C. aquatilis
has a very long, primary bract that exceeds the height of
the inflorescence (Figure 5). It has red-brown to
purple-brown carpellate scales with a narrow midvein
and nerveless or inconspicuously nerved perigynnia that
lack prominent papillae on the surface. The orifice of
the beak is entire and lacks scabrules (Figure 6).
3
Figure 5. Inflorescence of Carex aquatilis. Note the
very long lowest bract of the inflorescence (bent to the
right) that, when straightened, would exceed the total
height of the inflorescence.
Figure 6. Carex aquatilis perigynium, apical portion.
Note the lack of scabrules around the beak orifice and
absence of long papillae on perigynium surface.
DESCRIPTION OF THE P ROBLEM
Carex section Phacocystis includes both estuarine and
palustrine species. The species are brought into contact
both spatially and phenologically in the coastal Maine
region. The proximity of fresh and brackish water
habitats coupled with shortened growing season of
higher latitudes is believed to contribute to the
extensive hybridization seen in this section.
Furthermore, storm and ice disturbances of this region
may contribute to bringing species together and
creating new habitats for hybrid plants (Standley 1990).
Most reported Phacocystis hybrids are short-lived firstgeneration
hybrids with reduced fertility (Standley
1990). Several hybrid taxa, however, appear to be
wide-spread and persistent, including C. recta and C.
vacillans. These two species demonstrate lower
fertility than their diploid progenitors, however, they
are capable of producing viable seeds and appear to
successfully utilize vegetative reproduction (Standley
1990).
The name Carex salina, which has been incorrectly
applied to Maine plants, has been shown to be the
stabilized hybrid derivative of C. paleacea and C.
subspathacea (Standley 1990). Evidence substantiating
this theory came from many sources, including
morphology, anatomy, allozymes, and chromosomal
behavior. Carex salina occurs in Canada and Eurasia,
but is not a member of the United States flora. Plants
formally referred to as C. salina from Maine need to be
identified as one of two species—Carex recta or C.
vacillans. These two species are similar to C. salina in
that they are stabilized hybrids that demonstrate slightly
disturbed mieotic pairing and lower pollen stainability
than parental species (such as C. paleacea) (Cayouette
and Morisset 1985). Carex recta is known to be the
hybrid derivative of C. aquatilis and C. paleacea, while
C. vacillans is the hybrid derivative of C. nigra and C.
paleacea. Figure 7 graphically summarizes the
relationship of the involved species.
Figure 7. Reticulogram showing relationship of Carex
aquatilis, C. ×neofilipendula, C. nigra, C. paleacea, C.
recta, Carex ×subnigra, and C. vacillans. First
generation hybrids (F1) are discussed later in the text.
As C. recta and C. vacillans share a common parent (C.
paleacea) they are morphologically similar and difficult
to distinguish without careful study. Both species
possess similarity in form, including ascending to
spreading lower spikes borne on short peduncles
(mostly 0.6–2.0 cm long) (Figure 8). They have
acuminately-pointed to shortly-awned carpellate scales.
Though producing rhizomes, C. recta and C. vacillans
sometimes have a subcespitose growth form,
particularly when substrate is limited (i.e., growing in
cracks of rock). Additionally, they normally possess an
elongate lowest bract that overtops the uppermost spike
of the inflorescence. Separation of C. recta and C.
vacillans requires detailed examination of floral scales,
perigynia, and achenes. Table 1 provides comparative
4
morphological information for maritime Phacocystis of
Maine. Synonyms are located at the end of the article.
Figure 8. Carex recta. General form of both C. recta
and C. vacillans. Note the spreading lower spike.
DESCRIPTION OF THE STABILIZED HYBRIDS
The term stabilized hybrid means that a taxon has been
shown to be of hybrid origin, but behaves as a species.
Traits often associated with stabilized hybrids include:
relatively uniform morphology; novel character states
not seen in first generation hybrids; ability to produce
some viable fruit; and/or reasonably widespread
distribution that includes occurrences where one or both
parental species are not present. Carex recta and C.
vacillans meet well the description of stabilized
hybrids.
Carex recta and C. vacillans occur in coastal habitats.
This includes tidal marshes, crevices in beach outcrops,
and open meadows of small islands. They are rarely, if
ever, sympatric with both parents in Maine (Haines,
personal observation). Both species are ranked S1 by
the Maine Natural Areas Program (1999).
Carex recta is the stabilized hybrid derivative of C.
aquatilis and C. paleacea. It, therefore, is relatively
intermediate in the morphology of its parental
progenitors. Its carpellate scales are normally bronze to
brown with a relatively wide central band that occupies
33–50 percent of the total scale width (Figure 9). The
wide midrib is prolonged and always reaches the apex
of the scale. Carex recta possesses obscurely nerved
perigynia that are short-papillose and lack scabrules
around the orifice of the beak (Figure 10). Its achenes,
observed by removing them from the perigynia, are
generally lustrous and folded on one surface (Figure
11). Observations of achene luster and shape must be
made on well-formed seeds. As C. recta may show a
high proportion of malformed and infertile achenes,
care must be taken to locate mature material.
Figure 9. Carpellate scale of Carex recta showing
relatively wide midvein.
Figure 10. Perigynium of Carex recta. Note the
absence of several prominent nerves.
Figure 11. Illustration of Carex recta achene. Note
fold across surface.
Carex vacillans is the stablized hybrid derivative of C.
nigra and C. paleacea. Though generally similar to C.
recta, the different parental combination has provided
several subtle clues to its identity. The carpellate scales
are usually dark brown to purple-brown and have a
narrow midrib occupying 10–33 percent of the total
scale width (Figure 12). In some collections, the midrib
is evanescent and does not reach the apex of the scale.
The perigynium of C. vacillans usually possesses 2–5
nerves of each face, is densely long-papillose, and often
will possess a few scabrules around the orifice of the
beak (Figure 13). The achenes are generally dull and
lack a constriction.
5
Figure 12. Carpellate scale of Carex vacillans showing
relatively narrow midvein.
Figure 13. Perigynium of Carex vacillans. Note the
several raised nerves.
_______________________________________________________________________________________________
Species Primary Bract Lowest Spike Carpellate Scales Perigynium Surface Achenes
_______________________________________________________________________________________________
C. nigra shorter than to erect and sessile dark purple -brown, densely long-papillose, whitesubequal
to without awns 3–9 nerves on each iridescent,
inflorescence surface not indented
C. paleacea longer than drooping on long yellow-brown, with short-papillose, 0–5 lustrous,
inflorescence peduncles up to 7.5 scabrous awns to obscure nerves on indented on
(rarely equal to) cm long 1 cm each surface one side
C. recta longer than ascending to bronze to brown, short-papillose, lustrous,
inflorescence spreading on peduncles pointed or with obscurely nerved folded on
(rarely equal to) 0.6–2.0 cm long short awns one face
C. vacillans longer than ascending to dark brown to long-papillose, dull, not
inflorescence spreading on peduncles purple-brown, 2–5 nerves on each indented
(rarely equal to) 0.6–2.0 cm long pointed or with surface
short awns
_________________________________________________________________________________________________
Table 1. Comparison of key morphological features of maritime Phacocystis in Maine.
Table 1 presents a somewhat simplified view of the
maritime Phacocystis morphologies likely to be
encountered in Maine. Complicating identification is
the fact that the stabilized hybrids do cross with the
other coastal progenitor species (C. nigra and C.
paleacea) to create an extremely complicated situation.
The reader is referred to Cayouette and Morrisett
(1985) for detailed morphological comparisons of many
hybrid combinations.
FIRST GENERATION HYBRIDS
It is important to note that the process that created
Carex recta and C. vacillans (interspecific
hybridization between respective Phacocystis species)
is an ongoing phenomenon. Therefore, the progenitor
species continue to produce the first generation hybrids
that gave rise to the stabilized hybrids. The first
generation hybrids are very similar to the stabilized
hybrids and likewise display morphological
intermediacy, reduced fertility, and chromosomal
abnormalities (e.g., disturbed mieotic pairing).
However, the stabilized hybrids (C. recta and C.
vacillans) do not demonstrate the severity of
chromosomal abnormalities or infertility as do the first
generation hybrids. Furthermore, Cayouette and
Morrisett (1985) have shown that the stabilized hybrids
are not perfectly intermediate in morphology between
their parental progenitor species. Rather, they show
one or more subtle, novel character states. For
example, as previously noted, the achenes of C.
aquatilis are not indented on one side whereas those of
C. paleacea are. Therefore, the hybrid (called C.
×neofilipendula) would be expected to show, and
commonly does, a slight indentation on one side of the
achene. However, C. recta, the stabilized hybrid of
6
these two species, possesses a transverse fold across
one surface of the achene. This character state is not
seen in either parent. Discriminating between first
generation hybrids and stabilized hybrids by
morphology alone is extraordinarily difficult without
intimate familiarity with these species. Recent trend
has been to consider first generation hybrids and
stabilized hybrids by the same name (Bruederle,
Cayouette, and Standley, in ed.). The first generation
hybrids, identified by the “×” symbol, and their parental
composition are provided in the following list of
synonyms.
IMPORTANT SYNONYMS
Carex recta
C. kattegatensis Fries ex Lindmann
C. salina Wahl. var. kattegatensis (Fries ex
Lindman) Almquist in Hartman
C. ×neofilipendula Lepage (C. aquatilis × C.
paleacea)
Carex vacillans
C. ×subnigra Lepage (C. nigra × C. paleacea)
C. ×super-goodenoughii (Kükenth.) Lepage (C.
nigra × C. recta)
Literature Cited
Bruederle, L., J. Cayouette, and L.A. Standley. in ed.
Carex section Phacocystis Dumort. in Flora of North
America Editorial Committee. Flora of North America.
Oxford University Press, NY.
Cayouette, J. 1987. Carex lyngbyei excluded from the
flora of eastern North America, and taxonomic notes on
related species and hybrids. Canadian Journal of
Botany 65: 1187–1198.
Cayouette, J. and P. Morisett. 1985. Chromosomal
studies on natural hybrids between maritime species of
Carex (sections Phacocystis and Cryptocarpae) in
northeastern North America, and their taxonomic
implications. Canadian Journal of Botany 63: 1957–
1982.
Fernald, M.L. 1950. Gray’s Manual of Botany, eighth
edition. Van Nostrand Reinhold Company, New York,
NY.
Gleason, H.A. and A.C. Cronquist. 1991. Manual of
Vascular Plants of Northeastern United States and
Adjacent Canada, second edition. The New York
Botanical Society, Bronx, NY.
Leepage, E. 1956. Études sur quelques plantes
américaines. IV. Carex-hybrides. Naturaliste Canad.
83: 105–156.
Maine Natural Areas Program. 1999. Elements of
Natural Diversity: Rare, Threatened, and Endangered
Plants. Department of Conservation, Augusta, ME.
Standley, L.A. 1985. Systematics of the Acutae group
of Carex (Cyperaceae) in the Pacific northwest.
Systematic Botany Monographs, volume 7.
_____. 1990. Allozyme evidence for the hybrid origin
of the maritime species Carex salina and Carex recta
(Cyperaceae) in eastern North America. Systematic
Botany 15(2): 182–191.
Acknowledgments
I would like to acknowledge the assistance of Lisa
Standley and Anton Reznicek in the preparation of this
note. Editorial comments from Georgia Hall, George
Kendrick, John Lortie, and Robert Roy are

appreciated.


Text, photographs, and illustrations contributed by
Arthur Haines

---------------------from: 1

Botanical Notes
A newsletter dedicated to dispersing taxonomic and ecological information useful for plant
identification and conservation in Maine
Available online at http://www.woodlotalt.com/publications/publications.htm
Number 4. 13 December 2000 122 Main Street, Number 3, Topsham, ME 04086
IDENTIFICATION AND TAXONOMY OF
TWO DIFFICULT MARITI ME HYBRIDS
WITH CAREX PALEACEA
M

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