Table Of Content—
RHODORA,
Vol. 105, No. 923, 260-281, 2003
pp.
AND ON
CONSPECTUS NOTES THE GENUS
CANADA
AMARANTHUS
IN
MlHAI COSTEA^ AND
pRANfOIS TaRDIF^
J.
Department
of Plant Agriculture, University of Guelph,
NIG
Guelph, 2W1, Canada
Ontario,
[email protected];
e-mail: ^ftardif@uoguelph,ca
The Amaranthus
ABSTR.^cT. spp. collections from the largest Canadian herbaria
were reviewed and a conspectus was prepared. Tlie genus represented Canada
is in
by
14 species (eight naturalized, four cultivated, and two rare adventive) and by
New
six hybrids. records for the Canadian flora include: Amaranthus caudatus,
A. powellii subsp. bouchonii, A. hybridus subsp. qidtensis, A. blitum subsp.
X X
emarginatus, A. tricolor, A. poweHii A. hybrid A. powellii A, tuberculatus, and
its,
X
A, albus A. hlitoides. The presence of the previously reported dioecious species A.
palmeri and A. cannabinus not confirmed by herbarium The taxonomy
is material. of
the most problematic taxa discussed and a key provided Canadian
is is for all species
and Morphology
subspecies. of fruits, seeds, and pollen belonging A. albus and
to
A. californicus was compared and their taxonomic relationship discussed. The
infraspecific variability of A. tuberculatus was analyzed and a new nomenclalural
combination proposed
A, tuberculatus var. rudis.
Key
Words:
Amaranthus, Canada, weeds,
exotic plants
The
amon
and
ornamentals (Brenner
weed
taxonomists,
and
scienrists, horticulturists because taxa are
its
extremely polymorphic and
often not easy
to identify; additionally the
Canada
cuinvated or adventive and the genus has never been The
reviewed.
purpose of paper
this is to provide a of Amaranthus
list species
that
occur Canada and
in to discuss their taxonomy. The most
important
weed
species of the genus Canada
in have been
treated in detail for
the ''Biology of Canadian Weeds"
series. Tliey include: A. albus, A.
and
Tardif, in press) and A,
retroflexus,
and
(Costea
et al., unpubl. manuscript).
maps
Distribution
as well
as relevant biological and
ecological
information
260
—
2003] Costea and Tardif Amaranthiis Canada
in 261
MATERIAL AND METHODS
The
fo
HAM
DAO,
OTT
?
QUE, SASK, SFS, TRT, TRTE, TUP, UAC, UBC, UNB, USAS, UWO, UWPG, WAT,
V,
and
WIN. Furthermore, the Canadian collections deposited more than
in
40
herbaria in the United States (Costea, Sanders, and Waines 2001)
were
also examined. Detailed notes on the nomenclature and
most
descriptions for of the species can be found Sauer
in (1950,
1955, 1967); Costea, Sanders, and Waines (2001); and Costea, Waines,
and Sanders The morphology
(2001). of and seeds belonging
fruits to
Amarauthus californicus and A. alhus was comparatively studied from
Canadian
herbarium specimens (Appendix).
FurthenTiore, accessions
ARS
from the U.S.D.A., germplasm collection were examined
as well;
alhus—Ames Ames
A, 137 888 and 18499; A. colifornicus—Pl 595319
ARS
(U.S.D.A., 2002). The Scanning Electron Microscopy (SEM) was
Hummer
done
with a Hitachi S-570 10 and 15 kV, using an Anatech
at
VII sputter-coater. Twenty-five fmits and seeds were collected from
each herbarium specimen or per accession examined (Appendix). The
same number of pollen grains per herbarium specimen was
(25)
analyzed morphology
in order to assess the of the pollen grains in the
A
two
species (Appendix). of representative specimens examined
list
was
Appendix most
included in the for the problematical taxa. Plants
with mature fruits are necessary for accurate determinations. It is
important between and and
to distinguish tepals bracteoles, floral parts
should be examined magnifications higher than 30X. In the key
at
''tepals" refers to those of female flowers only.
AND
RESULTS DISCUSSION
The Canadian genus Amaranthus. Based on
species of the the
Canada
herbarium collections surveyed, in there are eight naturalized,
The
four and two adventive species of Amaranthiis.
cultivated, rare
number Canada fewer
of Amaranthiis spp. in than in floras of
is
same
significantly smaller countries from the latitude in Europe. For
example, approximately 25 Amaranthiis
Karlsson (2001) listed spp.
from cool-temperate northern countries such as Sweden, Denmark, and
may
Norway. The low number of species Canada be explained two
in in
ways. Firstly, in Canada the disturbed habitats in which amaranths thrive
common
comparative European where
are not as to countries, the
density of human settlements higher. Secondly, amaranths in Canada
is
262 Rhodora
[Vol. 105
number
are undercollccted; the total of Canadian specimens deposited in
Canadian and United States herbaria does not exceed 3000. Therefore,
number Amaranthus and from
the oi spp. their inferred distribution the
available herbarium material probably incomplete, especially one
is if
takes into account that there are about 40 species reported from the
NRCS
United States (U.S.D.A., 2002).
The Amaranthus Watson
dioecious amaranths, palmeri and A.
S.
cannabinus Sauer mentioned by Scoggan and might
(L.) are (1978)
occur Canada, but presence not confirmed by any herbarium
in their
is
Some
evidence. monoecious species that are widely distributed in the
United States and Europe, such as A. defiexus L., if not already
introduced Canada, be found
in are ver}^ likely to in the future.
KEY TO THE AMARANTHUS OCCURRING CANADA
SPECIES
IN
Plants dioecious A.
1. \, tubercidatiis
monoecious
Plants
1.
(2)
Rowers
2. in a tenninal spicifonn or paniculiform inflorescence
may
(axillary clusters be present as well)
(3)
3. Axils of stem leaves bearing a pair of spines; female flowers
distributed only at the base of each inflorescence branch
A. spitwsus
8.
3. Axils of stem leaves without spines; female flowers evenly
distributed the inflorescence
in
(4)
Tepals
4. 3
(5)
5. Tepals longer than the with a long, pale awn
fruit,
. . .
14. tricolor
/i.
Tepals shorter or equaling without an awn
5. the
fruit,
. .
(6)
Leaves somewhat
6, acute; tepals shorter than or
equaling the brownish, strongly muricate
fruit
. ,
13. viridis
.4.
Leaves much
emarginate
6. to bilobed; tepals shorter
than the green, almost smooth
fruit
blitum
12.
/4.
-
Leaves
7. not fleshy, deeply emarginate bilobed
to
at
apex; terminal inflorescence long, thin and
mm
flexuous; fruit 1.2-1.8 long; seeds 0.8-1.1
mm
diameter
in
12b. A. blitum subsp. emarginatiis
—
2003] Costea and Tardif Amaranthus Canada 263
in
Leaves
7. fleshy, emarginate but never bilobed;
terminal inflorescence and
short, thick dense;
mm mm
fruit 1.7-2.6 (-3) long; seeds 1-1.2
in
diameter
12a. A. blitum subsp. hlitum
Tepals 3-5 on same
4. the plant, or constantly 5
(8)
8. Tepals spathulate to obovate
(9)
9. Cultivated ornamentals or cereals, sometimes escaped
in ruderal places, with large and conspicuous red,
yellow, or whitish inflorescences; bracteoles
shorter than stigma branches; tepals shorter than
fruit (10)
cm
10. Inflorescence with a terminal part 10-30 (^0)
long, thick and pendent; tepals wide-obovate to
spathulate, the outer ones overlapping laterally
±
and narrowed
outcur\xd; gradually
fruit
toward apex; stigma branches spreading ....
A. caudatus
,' 2.
.
many
Inflorescence usually with patent (±
10. lateral,
on
perpendicular inflorescence axis) or ascen-
narrow-obovate,
dant, thin branches; tepals
and
not overlapping; abruptly
straight fruit
narrowed toward apex in a thin rostrum; stigma
branches
erect
A. cruentus
3.
Weeds
with green inflorescences; bracteoles longer
9.
than stigma branches; tepals longer than the
(11)
fruit
below
Stem
sparsely hairy inflorescence; inflo-
11.
many
rescence with lateral, patent, thin
beyond
midribs extending apex
branches; tepal
mucro
into the
4b. A. hybridus subsp. qidtensis
11. Stem densely hairy below inflorescence; inflores-
cence usually with short, thick, ascendant or
branches; tepal midribs ending below
erect
apex (although apex often mucronate)
A.
1, rctroflcxus
Tepals oblong-linear to lanceolate
8. (12)
ornamentals sometimes
Cultivated or cereals,
12.
escaped in ruderal places, with large and
264 Rhodora
[Vol. 105
conspicuous 3—4
red inflorescences; pericarp with
cell layers; bracteoles shorter than stigma
branches
(13)
13. Fruit abruptly narrowed toward apex in a thin
rostrum; stigma branches
parallel, erect;
in-
many
florescence usually with patent or
lateral,
ascendant, branches
thin
A. cruentus
3.
apex
13. Fruit truncated, rostrum absent, stigma
branches divergent from
the base; inflores-
cence
usually with
stiff, thick, erect or
ascendant branches
A. hypochondriaciis
5,
Weeds
with green 2-3
12. inflorescences; pericarp with
cell layers; the bracteoles surpassing stigma
the
branches
(14)
few
14. Inflorescence with a and widely
rigid, erect,
spaced branches or with many ascendant or
erect, thick branches; leaves broadly
elliptic to
rhombic
or lanceolate; tepals 3-5, very un-
equal with
yellowish midveins; fmit apex
gradually narrowed
(15)
.
±
Inflorescence and
15. unbranched
stiff erect,
or with a few widely spaced, long
mm
branches;
bracteoles 5-7.5
(-8) long;
fruit circumcissile, irregularly wrinkled
above
the dehiscence ....
line
6a. A. powellii subsp. powellii
15. Inflorescence not more
strictly erect, lax,
many
with
lateral branches; bracteoles
mm
3.5-5
long;
fruit indehiscent or
±
irregularly dehiscent, smooth
6b. A. powellii subsp. hoiichonii
14. Inflorescence usually with many
patent, short
and
thin branches
or with only few
a
thin,
flexuous and
long
branches; leaves broadly
ovate
to rhombic-ovate;
tepals subequal with
5,
mid
green
veins; apex
fruit abruptly nar-
rowed
(15)
Tepals
16. erect, shorter than
the
fruit
4a. A. hyhhdiis subsp. hyhridus
—
2003] Costea and Tardif Amaranthus Canada
265
in
Tepals
16. erect or outcurved, longer than the
fruit
4b. A. hyhridlis subsp. quitensis
2. All flowers in axillary cyniose clusters, terminal inflorescence
absent
(17)
17. Perianth with (4-) 5 tepals A. bUtoidcs
\\,
17. Perianth with 3 tepals or reduced to 1-2 tepals
(18)
18. Leaves emarginate or slightly bilobed; bracteoles
folia-
ceous; indehiscent
fruit
(19)
mm
19. Fruit 1.7-2.6 (-3) long, pericarp 4-!ayered; seeds
mm
1-1.2 diameter
in
12a. A. hlitum subsp. hlitum
mm,
19. Fruit 1.2-1.8 pericarp 3-layered; seeds 0.8-Ll
mm
diameter
in
12b. blitum subsp. emarginatiis
i4.
18. Leaves not emarginate; bracteoles spinescent;
fruit
circumcissile
(20)
many
Stems from and mat
20. the base, prostrate
forming, sometimes ascendant; stem and leaves
male
glabrescent, often fleshy-turgescent; flowers
with 1-2 stamens; bracteoles short, thin, equaling
the fruit; perianth of female flowers with linear-
1
membranous
and
lanceolate, tepal (-2) tepals
1
reduced or absent
that are
10. A. californicus
20. Stems usually single, divaricately branched, ascen-
dant bone-like, usually scurfy
to erect, rigid,
villous or pubescent; leaves not fleshy; male
flowers with (2-) 3 stamens; bracteoles 1.5-2X
longer than spinescent, subulate,
fruits, rigid;
membranous
female flowers perianth with 3
A. alhus
tepals 9.
TAXONOMIC TREATMENT
Subgenus Acnida Aellen ex K. R. Robertson, Arnold Arbor.
L.)
I. J.
(
62: 283. 1981.
L
Amaranthus (Moq.) D. Sauer, Madroiio
tiihoxidatiis 13: 18. 1955;
J.
Madrono
A. D. Sauer, 21: 428. 1972.
incl. riidis J.
Rhodora
266
105
[Vol.
Pratt and Clark (2001) showed that Amaranthus tubercidatus and A.
rudis as defined by Sauer 955) are the morphological extremes of a single
( 1
variable waterhemp species continuum. However, the authors admitted
that the morphologic variation of female flowers exhibits a geographical
separation, which follows Sauer's concept of two waterhemp entities
(Sauer 1955). The westem specimens correspond to the A, rudis race,
while northern and eastern North American populations can be ascribed to
typical A. tubercidatus. The two forms have a different ecology. Sauer
grow
(1955) observed that although they in similar habitats (e.g., margins
of inland bodies of water), A. rudis (= A. tamariscimis) has "a very
weedy compared
definite tendency" to A. tuberculatus. Furthermore, the
pericarp of the indehiscent fruits (in typical A. tuberculatus) provided
is
more
with extensive intercellular air spaces allowing a effective water
dispersal of the seeds than of the plants having circumcissile
fruits (in
typical A. rudis\ Costea et unpubl. data). Only in the midwestem
al.,
populations (Iowa, Illinois, and Missouri) might diagnostic
traits
segregate in populations and form a unique and inseparable morpholog-
ical, isoenzymatical (Pratt and Clark 2001; Sauer 1955) and, most
probably, ecological complex. Uline and Bray combined
(1895) also the
two waterhemps Acnida W.
in a single species, tamariscina (Nutt.) A.
Wood,
but the authors recognized them The
as varieties. latter solution
seems to be the most appropriate because would allow a distinction of the
it
two on morphology
entities (based the of the female flowers and
their
ecology) outside Midwest.
the
Amaranthus
tuberculatus
la. var. tuberculatus.
Female flowers with one or two lanceolate or linear tepals; the fruit
is
indehiscent. It has been collected since the last century from Ontario and
Quebec, where grows
it is native. It along lake shores, ponds, and rivers
(Appendix).
Amaranthus &
tuberculatus
lb. var. rudis D. Sauer) Costea
(J.
comb, Amaranthus
Tardif, nov. rudis D. Sauer, Madrono 428.
21:
J.
Aug
Type: u.s.a. Kansas: Riley Co., 6 895, 5. Norton 428 (holotype:
/.
1
MO
1740436!).
Female
flowers with absent or
vestigial tepals; the dehiscent.
fruit
is
This invasive weed,
often
resistant to various herbicides, has been
m
recently introduced southern Lambton
Ontario, County, and few
in a
specimens were from
collected ruderal places Bumaby,
in British
Columbia
(Appendix).
—
—
Costea and Tardif Amaranthus Canada 267
2003J in
Subgenus Amaranthus,
II.
The most problematic group of species in this subgenus referred to
is
Amaranthus
in the literature as the hybridiis aggregate. includes six
It
extensively studied species, today almost cosmopohtan in distribution
(A. hybridiis, A. powellii, A. hypochondriaciis, A. cruentus, A. caiidatus,
and A. qidtensis), and a number of other species, poorly known,
restricted to the southern parts of North America and to Central and
South America (Costea, Sanders, and Waines 2001; Sauer 1950, 1967).
Amaranthus retroflexus usually separated from this complex. In our
is
opinion, should be included here as well because hybridizes readily
it it
with of the above-mentioned species. Cytological studies indicate
all
genomic homology between and members
a close A. retroflexus other
of the A, hybridus complex A. cruentus and A. powellii; Pandey
(e.g.,
1999). Molecular (Xu and Sun 2001) and morphological studies (Costea
DeMason Waines
and 2001; Costea, Sanders, and 2001) have, in
Amaranthus
proved of (seven with
general, the distinction the six
retroflexus) species. However, such studies have necessarily based their
A
number
conclusions on a limited of populations and/or accessions.
worldwide survey of thousands of Amaranthus herbarium specimens
some and an
has revealed especially subtropical tropical regions,
that, in
may
between
overlapping pattern of variation occur species (Costea,
unpubl. Nonetheless, including these six (or seven) species in
data).
a broadly defined A. hybridus may be a premature solution. Other
concepts of hybridus which only one or several species are
A, in
included in A. hybridus, while the others are separately maintained or
combined various ways, are also unacceptable because they provide
in
an Therefore, until the pattern of variation within
arbitrary classification.
known
this group, including the less species, is properly understood, the
maintain them specific rank.
best solution to at
is
2. Amaranthus caudatus L., Sp. PI. 990. 1753.
This South American species, reported here for the first
distinctive
time Canada, sometimes cultivated as an ornamental (Appendix).
in
is
The Amaranthus caudatus, A. hypochondriacus, and
amaranths
grain
—
A. cruentus have generated a great interest in recent years as
agricultural crops in the United States and other regions of the world,
due to the exceptionally high nutritional value of their seeds and leaves.
For comprehensive review of the genetic and breeding resources of
a
these species, see Brenner et al. (2000).
268 Rhodora
[Vol. 105
Amaranthus
3. cnientiis L., Syst. Nat. ed. 10, 1269. 1759.
from America, and Canada name
This species native Central in the
is
has been frequently misapplied to Amaranthus hypochondhacus.
It is
cultivated as an ornamental (but less frequently than A. hypochon-
driacus) and sometimes escapes in ruderal places in Alberta, Ontario,
it
and Quebec (Appendix). In Canada, has usually been treated as
it
Scoggan
a variety of A. hyhridus (Boivin 1966; 1978).
Amaranthus PL
4. hyhridus L., Sp. 990. 1753.
Amaranthus
4a. hyhridus subsp. hyhridus, A. patulus Bertol.,
&
Comment.
Neapol. 1837. A. incurvatus Timeroy ex Gren.
Itin. 19.
FL
Godr., France Prosp. 1846.
8.
Originally from eastern North America, Mexico, and Central America,
now
taxon widespread over world weed
this is all the as a in cultivated
or ruderal places. In Canada, confined southwestern Ontario
to
it is
an
Winnipe
We
1957). were unable to prove this from herbarium material, altho
the presence of this taxon in other provinces likely to be expected.
is
&
Amaranthus
4b. hyhridus subsp. quitensis (Kunth) Costea
&
Carretero, Sida 19: 955. 2001. A, quitensis Kunth, Humb., Bonpl.
Kunth, Nov. Gen.
Sp. 2, folio: 156; ed. 4: 194. 1817.
new
This a record Canada, based on
is for a single collection:
A
Toronto, Bull grounds, 10 Sep 1904, W, Scott s.n. (trt). native of
tropical South America, where a noxious weed, be
it is this plant tends to
more warm
restricted to climates than subsp. hyhridus, and unlikely
is
it
become
to a pemianent of Canadian
part the flora in the future.
Amaranthus
hypochondriacus
5. L., Sp. PI. 991. 1753. A. hyhridus L.
subsp. hypochondriacus
(L.) Thell. [rankless] erythrostachys
&
(Moq.)
Thell., Asch. Graebn., Syn.
Mitteleur. 241. 1914.
Fl. 5:
Canada, Amaranthus
In hypochondriacus
has been considered
synonym
a of
A, hyhridus, but
the description of the species
latter
former
Canada
and
escapes
it in ruderal places in British Columbia, Alberta, Manitoba,
and Quebec
Ontario, (Appendix).
—
2003] Costea and Tardif Amaranthus Canada 269
in
Amarantlnis poweUii Watson, Amer.
Acad.
6. S. Proc. Arts. 10: 347.
1875
>^'
Watson)
(S. B. Boivin, Naturaliste Canad. 93: 641. 1966.
This subspecies native to North and South America and has
is
previously been shown be frequent Quebec and Ontario (Doyon
to in
et al. 1986; Frost 1971). The subspecies was also reported from British
Columbia Saskatchewan, and from Prince Edward Island (Boivin
to
Moss mentioned Amaranthus was on
1966). (1983) that powellii ''rare
waste ground" in Alberta. Based on the early reports of this species in
British Columbia and Alberta (which date from the 1800s), A.
late
may much
powellii be more frequent these provinces than currently
in
is
may Nova
believed and same occur Saskatchewan,
the situation in
New A
Scotia, and Brunswick. few specimens of A. powellii, previously
identified as A. retroflexus, were examined from these provinces.
&
Amaranthus bouchonii Costea
6b. powellii subsp. (Thell.)
Monde
Carretero, Sida 19: 964. 2001; A, bouchonii Thell., PI.
27(160): 1926.
4.
This
an
European where has frequently been accepted the
central countries, at
it
rank
banks
dispersal advantage conferred by indehiscent fruits. Afterwards, has
its it
may
invaded where compete efficiently with other
irrigated fields,
it
Waines, and Sanders
amaranths such as A. retroflexits. Costea, (2001)
based on morphology, reduced
reported from the United States and, its
it
The authors suggested two
to a subspecies of A. powellii. latter
it
North America. The one
hypotheses regarding presence in first
its
bouchonii was introduced from Europe;
suggests that A. powellii subsp.
had
the second hypothesis assumes that the indehiscence character
North America and Europe. This
developed simultaneously both
in
and by wide and
second supported by the early records the
hypothesis
is
North America
observed for these plants in
scattered distribution
However,
(Costea, Sanders, and Waines 2001; Appendix). this taxon
has acquired here the consistency observed in Europe.
apparently not
A
would
study using molecular markers be necessary to clarify the
between two subspecies using both European and
relationships these
North American source material.
