ISOETES PROTOTYPUS (ISOETACEAE) IN THE UNITED STATES

7 Pages·1993·2.9 MB·English

by  Daniel F Brunton

RHODORA,
No. 122-128, 1993
Vol. 95, 882, pp.
PROTOTYPUS
ISOETES (ISOETACEAE) IN
THE UNITED STATES
Daniel Brunton and Donald M. Britton
F,
ABSTRACT
Isoetes prototypus Britton, an endemic of the Atlantic Maritime Ecozone of
Northeastern North America, reported for the time in the United States
is first
from Acadia National Park, Maine. a rare species throughout range, being
It is its
known elsewhere (in Atlantic Canada) from only five populations. For reasons of
site requirements and possibly dispersal limitations, Isoetes prototypus is unlikely
to be found in the United States away from the coastal region of Maine. It warrants
designation as Critically Imperiled (GlSl) throughout range.
its
Key Words: Isoetes prototypus, Isoetaceae, Maine, Acadia National Park, distri-
bution, conservation
INTRODUCTION
The member
rarest of the pteridophyte genus Isoetes in north-
eastem North America the Prototype Quillwort, prototypus
is /.
Britton (Britton and Goltz, 99 one of the few northeastern
It is
1 1),
=
North American
diploid (2n increasing
Isoetes species its
22),
which
value for evolutionary investigations of a group in allo-
and
ploidy autoploidy are considered be important for speci-
to
ation (Taylor and Hickey, 1992). Isoetes prototypus also has a
variety of morphological characteristics which are rare and in
some
unique North American and Goltz,
cases, in Isoetes (Britton
and
1991) (Figures 2
3).
Isoetes prototypus has been previously reported from only four
A
an
lakes, in Atlantic Canada.^ specimen representing ad-
all
and from outside
ditional locality constituting the record
first
Canada was
discovered in material taken in Acadia National Park,
The
Maine. following describes that population and considers
aspects of the ecology, geography and conservation significance
of
the
species.
populatio
M.
23 August
1990, OAC)
122
—
Brunton and
1993] Bri tton Isoetes 2 3
1
METHODS
A
recent review of
a set oi Isoetes specimens collected in Acadia
National Maine
Park,
resulted in the discovery of specimen
a of
The
prototypus. was subsequently and
/. site visited investigations
o^
Isoetes population and Com-
size ecology were undertaken.
site
>
parison of
these data with those gathered
in earlier studies
(e.g.,
and
Britton Goltz, 1991) was undertaken
order
in to assess eco-
»
similarities
nadian
populations.
RESULTS
Despite recent surveys of most northeastern Isoetes material
for several studies (including Kott and Britton, 1983; Taylor
et
1993 and (1989-1992) maritime Canada and
al., pers. obs. in
New
England), prototypus remained unrecorded in the United
/.
we
States until identified a collection from the north end of Bubble
Pond, Acadia National Park, Maine W. Greene 1782. 18
(C.
A
August
1987, HcoA,OAc), subsequent search of the uncov-
site
ered a large population of prototypus there (D. F. Brunton and
/.
K. L. Mcintosh 11,347, 19 September 1992, oac, dfb, can, dao,
MIL, bm).
m
Pond
Bubble asl—
a small, spring-fed lake at 101 a rela-
is
The
tively high elevation along the coastal plain. lake situated
is
in a broad Palaeozoic volcanic and intrusive bedrock trough.
Its
profile characterized by a broad, shallow shelf of silty-sand/
is
m
coarse sand extending 4 40 out from shore which pitches
to
much
steeply darker water (Figure
into deeper, noticeably
1).
Isoetes prototypus was found growing through dense Eriocaulon
cm
septangulare mats in a 20-30 thick layer of loose, silty ooze
over
sand in deep cool, oligotrophic water at the top of the steep
slope to deener water. The nlants were not observed in water less
m
than 1.5-> from
2.0 deep, although label data
were water
lection reports those plants collected in ca. 1.0
that
m
cm
Bubble Pond prototypus has unusually long leaves— 12.5
/.
cm
compared
(average of 15 plants)—
New
Nova and Brunswick)
from
Scotia
otherwise
tremely sharp
straight,
stiff,
Rhodora
124 95
[Vol.
Figure North end of Bubble Pond, Acadia National Park, Maine. Isoetes
1
.
>
prototypus abundant well out from shore, from the point where water depth
is
m
achieved (dark
1.5 is area).
leaves with mahogany-coloured bases and a velum completely
and
covering the sporangium. Megaspores are small (< 500 /im)
ornamented by an obscure, network of low, broad,
reticulate
smooth
'meandiform,' mound-like markings on an
essentially
surface. These are typical of the megaspores of/, prototypus (Fig-
ure
2),
commonly
tuckermanii A. Br. occurs the north end outlet
at
/.
cm
Pond warm
of Bubble in 2 to 10 deep fresh, water on silty-
The
sand/coarse sand none was observed deeper water.
in
flats;
presence of Bubble Pond, macrospora
a third Isoetes species in
/.
Dur., indicated by the single up-rooted plant of the hybrid
is
X x
Isoetes harveyi A. A. macrospora tuckermanii).
Eat, (== It
/.
common
a hybrid within mixed populations of the parent
is sterile
and company
species always occurs in the of both parents (Britton,
1991), Both of these species (and their hybrid) can be readily
separated from prototypus by more recurved,
their delicate,
/.
mega-
reddish-green leaves and ornamented
larger, intricately
band of
spores (high-walled, densely reticulate pattern with a
more equator— Kott
small, or less distinct spines along the
cf.
and
Britton, 1983).
Brunton and
1993] Bntlon—Isoetes
125
--—" -»-^'^^^
Figure
2. Isoetes prototypus megaspore with irregular pattern of tubercles and
low, meandiform (TOPOTYPE/PARATYPE, New
York
Brunswick;
ridges Co.,
UNB
Hinds =
77-41
28537) (bar 100 /im).
This
habitat comparable Canadian evidence
to First of
is sites.
prototypus by washed up on
/. is usually offered plants shore
because
the typically abundant deep water populations are not
readily apparent from the surface (Britton and Goltz, 1991). Sim-
ilarly, prototypus was not apparent during an unaided search
/.
We
from
the surface of Bubble Pond. examined that population
with
the aid of a glass-bottomed box to improve underwater
We
viewing and swimming down have had
by
to the plants.
dragg
across bottom and
the lake
collecting
readily
float to the surface thereafter.
survey
other apparently suitable lakes in Acadia National Park in Sep-
tember 1992; nearby Jordan Pond appears to be a particularly
likely candidate but has received considerable botanical attention
for over a century without providing evidence of this species.
Rhodora
95
126 [Vol.
(TOPOTYPE/
Figure Densely fine-spinulose Isoetes prototypus microspore
3.
UNB -
PARATYPE, New
York Brunswick; Hinds 77-41 28537) (bar 10
Co.,
Mm).
DISCUSSION
Few
washed-up plants were evident Bubble Pond, in contrast
at
to other prototypus lakes we have examined. Boating and swim-
/.
ming
are prohibited in this lake, perhaps lessening the disturbance
We
to the bottom by motors, and swimmers. also
fishing lines
suspect that bottom-feeding waterfowl and Muskrats, wintering
and may
reptiles amphibians, and/or spawning be responsible
fish
for producing massive shore 'wracks' (accumulations of washed-
up
vegetation) consisting of various species of Isoetes plants, but
this has not been confirmed. Such Isoetes wracks are regularly
Amer-
encountered along the Atlantic coast and western North
in
ican Cordillera—
pers. obs.
The Bubble Pond
station of/, prototypus constitutes the south-
ernmost
population for this endemic of the Atlantic Maritime
Ecozone Wiken,
(cf. 986). Its occurrence in a deep, cold, nutrient-
1
may
poor
lake reflect a particularly of requirements
strict set site
and/or
the species' inability to tolerate significant competition.
Brunton and
1993] Brixxon—Isoetes 127
We
typically find Isoetes prototypus in such sites either growing
alone or with very few
associates (such as Eriocaulon septangulare
With., macrospora x
Isoetes or Isoetes heterospora A. A.
Eat.).
Such and
a distinctive restrictive habitat requirement likely also
restricts the distributional potential of prototypus, contributing
/.
may
to global Dispersal such be by
its rarity. to sites limited the
existence of its complete sporangial velum which reduces the ease
of and
separation rupture of sporangium from
the the sporophyll,
perhaps reducing the of microspores and mega-
availability free
spores for transport by water currents, animal activity or other
dispersal agents.
seems remain
It likely that prototypus will a rare species in
/.
the United States, found only in the cold, clear Palaeozoic-bed-
rock based lakes in the Atlantic Maritime Ecozone along and near
the Atlantic coastal plain in Maine. Given the greater intensity
New
of botanical investigation in England than in Atlantic Can-
commonly
ada, seems unlikely evidence of distributed
that
it
American when documen-
populations would have been missed
tation of comparable Canadian populations dates back to the early
of
years
this century.
The
conservation of prototypus meets the high priority
status L.
scheme
designation of Nature Conservancy ranking (Morse,
the
Gl
Argus and warrants
1987; the species likely
Pryer, 1990);
Im-
warrants
(Critically Imperiled) Similarly, Critically
status. it
New
Nova
Bruns-
periled Provincial/State status (SI) for Scotia,
wick and
Maine.
The and
of populations of species the general vul-
rarity this
nerability of aquatic Isoetes to water pollution strongly suggests
Endangered Vulnerable)
that prototypus warrants (or at least
/.
Canada and United
Species designation both the States.
in
ACKNOWLEDGMENTS
An-
Our Allan
thanks congenial and expert field associates
to
who
derson and Karen Mcintosh have contributed a great deal
L.
to our throughout the range of the species.
on-site investigations
We
Acadia Na-
of examining the
opportunity
also appreciate the
Park
Acadia National botanist
Park by
tional material afforded
Linda Gregory. The second author thanks the National Sciences
grant
of
research.
ft
{
Rhodora
128 95
[Vol.
LITERATURE
CITED
Argus, G. W. and K. M. Pryer. 1990. Rare Vascular Plants in Canada: Our
Museum
Natural Heritage. Botany Division, Canadian of Nature, Ottawa.
A
M. North
Britton, D. 1991. hybrid Isoetes, x harveyi, in northeastern
/.
America. Can. 634-640.
Hot. 69:
J.
AND GoLTz. new from
P. 1991. Isoetes prototypus, a diploid species
J.
eastern Canada. Can. Bot. 69: 277-281.
J.
KoTT, L. AND D. M. Britton. 1983. Spore morphology and taxonomy of Isoetes
in northeastern North America. Can. Bot. 61: 3 140-31 63.
J.
Morse, Rare Conservancy The Nature Con-
L. E. 1987. plant protection, style.
servancy Magazine 10-15.
37(5);
Taylor, W. C, N. T. Luebke, D. M. Britton, R. Hickey and D. F. Brunton.
J.
1993. Isoetaceae H. G. L. Reichenbach— Quill wort Family. In: N. Morin,
Ed., Flora of North America, Vol. Oxford University Press (in press).
1.
AND
Hickey. and Ann.
1992. Habitat, evolution, speciation in Isoetes.
J.
Missouri Bot. Gard. 79: 613-622.
WiKEN, E. 1986. Terrestrial Ecozones of Canada. Ecological Land Classification
No. Environment Canada,
Series 19, Ottawa.
ROAD
LINCOLN HEIGHTS
2 6
1
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