Status and ecology of Agalinis Kingsii (Scrophulariaceae), a rare endemic to the Cayman Islands (Caribbean Sea)

11 Pages·2003·4.4 MB·English

by  A Diochon

RHODORA,
Vol. 105, No. 922, pp. 178-188, 2003
STATUS AND ECOLOGY OF AGALINIS KINGSH
A RARE ENDEMIC
(SCROPHULARIACEAE),
CAYMAN
TO THE ISLANDS (CARIBBEAN
SEA)
Amanda
Diochon
Department of Biology, Francis Xavier University,
St.
B2G
Nova 2W5, Canada
Antigonish, Scotia,
Burton
Frederic
J.
Cayman
National Trust for the Islands,
SMB,
Box 31116 Grand Cayman, West
P. O. British Indies
David Garbary*
J.
Department of Biology, St Francis Xavier University,
B2G
Nova 2W5, Canada
Antigonish, Scotia,
^Corresponding Author; e-mail: [email protected]
ABSTRACT. AgoUnis kingsii (Scrophulariaceae) a rare Grand Cayman species
is
known
that is poorly taxonomically and ecologically. Sampling in 1999 suggested
that approximately 43,000 individuals occurred within a single 500,000 m^ sedge
wedand
habitat in the Salina Reserve and that approximately 500 plants occurred
in
m
Mangrove Wedand.
a 9 location in the Central For every tenth individual located
during the population count in the Salina Reserve, vegetation community asso-
ciations, environmental parameters, and individual morphology were noted. Based on
we
the findings, suggest that rarity is a consequence of habitat availability. Since both
populations were found within a narrow geographic and ecological range, we
may
conclude that this species be sensitive to extinction via a stochastic event.
Key
Words: Agalinis kingsii, Caribbean Sea, endemism, endangered Grand
species,
Cayman,
Scrophulariaceae
Agalinis kingsii Proctor (Scrophulariaceae) one of 21 endemic
is
species of vascular plants reported from the Cayman Islands (Caribbean
Sea; Proctor 1994). Proctor (1977) described A. based on
kingsii a single
by Kings
collection in 1935, but the exact location of the type locality
The
and
>/
small, but stable population of A. kingsii was later reported by Davies
(1994) based on unpublished observations by Burton Both
1988.
in
accounts reported the species growing on ground Conocarpus
drier
in
erectus L. swamps. These limited reports are the onlv known accounts
178
—
Diochon
2003] et Agalinis kingsii 179
al.
of and
the species bring to light the lack of taxonomic, biogeographic,
and
ecological information on
A.
kingsii.
The
aforementioned
Agalinis kingsii populations are small and
found within a narrow geographic and ecological range. According
to
Gilfedder et al. (1997) and van Treuren et (1993), narrowly endemic
al.
species with small populations are vulnerable to extinction due to sto-
commonly
chastic events. Translocation techniques are used ensure
to
the survival of self-sustaining populations in the wild (Gilfedder
et
al.
Watson
Cayman
botanical garden on Grand
exists
rapidly disappearing (Davies 1994) and
tl
agement unknown.
needs of the species are In order to effectively
knowled
species in natural environment essential (Gilfedder al 1997;
its is et
Watson
The
phological and ecological description of Agalinis kingsii; 2) evaluate
the distribution and abundance of A. kingsii on Grand Cayman; 3) con-
human
sider the long-term survival of A. kingsii in light of the impact of
and primary and suggest
activities frequent disturbance in habitat; 4)
its
manaeement enhance the lone-term survival of A. kingsii.
strategies to
AND METHODS
MATERIALS
Study The
area-
Grand Cayman, West
inland off the northeast coast of British
The was
W.L- 19''2rN, 8r07'E; Fisure area established
1).
grant
man and
Islands
The
and
and
livestock grazing.
wetland
former
(Conocarpus erectus) swamp, possibly brought to its present state
disturbance (National Trust for the
because of or anthropogenic
fire
Cayman The wetland a mosaic of communities, and has
Islands 1997). is
been likened to the Florida Everglades (Diochon, pers. obs.; National
Cayman
Trust Islands 1997).
for the
Rhodora
[Vol. 105
180
Map
Figure Location of study area. A. of Caribbean Sea showing location of
1.
Cayman Cuba
Grand (arrow), and positions of Florida (F), (C) and Jamaica B.
(J).
Cayman
Detail of Grand showing location of the Salina Reserve (S) and Central
Mangrove Wetland (M) populations of Agalinis kingsii. C. Detail of Salina Reserve
showing location of sedge wetland (W) and area examined for population count
(arrow).
A
May
This study was conducted from August 1999. population
to
when
count was completed during July 1999 the plants were most
A
conspicuous. portion of the sedge wetland was selected based on
was
accessibility, and a grid established in this area for a concurrent
on community
study the structure of the wetland. All plants of Agalinis
kingsii in the grid were counted and the search was expanded into the
surrounding area for A. kingsii individuals. Care was taken to mark the
boundaries of the area examined to facilitate area calculation using
CA)
a Trimble (Sunnyvale, global positioning system and Arc View GIS
software (ESRI, Redlands, CA).
Data The
collection- relative position of every tenth Agalinis
—
kingsii individual (N 101) was noted in conjunction with the number
—
of individuals in the immediate area (N 1014). For every tenth
following environmental and were
individual, the biological factors
—
Diochon
2003] et Agalinis kingsii 181
al.
recorded: percent (%) shade at the soil surface, estimated by the
1)
percentage of biomass cover from
at the soil surface; 2) the distance soil
surface to the water table; plant height, measured as the distance from
3)
the soil surface to tip of peduncle; 4) number of flowers on peduncle; 5)
number number
of branches; average of flowers on
lateral 6) lateral
% m
branches; 7) associated species and cover in a quadrat using the
1
community
individual as the center; 8) association; 9) evidence of
previous generations; 10) evidence of defoliation herbivory); and
(i.e.,
was
the presence of ants in or on the corolla. If the tenth individual
1 1)
a no were
juvenile, data recorded.
Continuous monitoring for potential pollinators entering the corolla
was undertaken for the duration of the study between the hours of 0730
A
Monday
and 1630, to Saturday. qualitative description of flower
morphology was developed based on both observations and mea-
field
microscope and
surements of flower structures using a dissecting a
Flower
standard ruler on 20 flowers transported in alcohol. structure
measurements included: length and position of stamens; 2) length,
1)
width, and morphology of ovary; and 3) length of style and stigma.
marked was monitored
phenology of 20 individuals
In addition, the
To one
throughout determine the species self-fertilized,
the study. if
was bagged with nylon mesh,
flower on each of 10 of these individuals
and the bag was until the flower wilted and/or detached.
left
Mature seeds were collected on an ongoing basis from the Salina
(month/day: 06/09; 06/12; 06/16; 06/23; 07/02; 07/19; 07/16; 07/23; 07/
Seeds were also collected from a second population in the Central
29).
Mangrove Wetland 07/29; Figure The length and width of
(07/22; 1).
=
were measured using
mature seed capsules (N 100), not yet dehisced,
The number of seeds was
a dissecting microscope and a standard ruler.
and measurements of length and width were
counted from each capsule,
microscope
recorded 50 randomly selected seeds using a dissecting
for
herbarium
and Voucher specimens for seeds are deposited in the
ruler.
Cayman Grand Cayman).
(caym;
Islands
of National Trust for the
the
whole
of Agalinis plant
Because of concern over the status kingsii,
the
specimens were not collected.
Seed morphology has been recognized for its value in the systematic
Mann
Musselman and
1976;
(Canne 1979, 1980;
analysis of Agalinis
To provide a more detailed description of
Pennell 1913, 1929, 1935).
was examined
morphology of mature seeds using
the species, surface
(SEM). Seeds (unfixed and without
microscopy critical
scanning
electron
point drying) were mounted on a sticky carbon stub, sputter-coated with
SEM.
JSM-5300
examined on
and a Joel
gold (2-60 cycles),
sec.
Rhodora
182
105
[Vol.
Data were analyzed using the descriptive package SPSS
statistics in
Windows
(SPSS
8.0 for Inc., Chicago, XL). Values given in text are
±
ranges and means SE. The nomenclature used in this paper follows
Proctor
(1984).
RESULTS
Description of Agalinis kingsii. Agalinis kingsii individuals ranged
The
sometimes and blackened upon The
violet, drying.
and
ascend. All lobes of the corolla spread and were pubescent within the
at
tenor lobes. There were between 5 and 13 flower;
0-7
flowers on each 0-7
lateral branch, with
branches
The was membranous
corolla
The
and the calyx lobes were always less than the length of the tube. There
mm)
were two mm)
shorter (4-5 and two longer (8-9 stamens
that at-
The
ovary
4^5
mm
mm
Ions and 11-13
and contained 196-205 unknown
seeds of
viabiUty. Seeds were 0.6-
mm
mm
0.9 long and 0.2-0.3 wide (Figure The shape was
2). angular
and
bluntly trapezoidal (Figure The outer seed was
3). coat black and
and
(Fig
The
The
radial walls were uniformly
The
variable
Abundance and
ecology. In the 17,764 m^ area examined
in the
\52A
Salina, Agalinis
kingsii individuals were
located, equaling a density
10"^
of 8.57 individuals m~^. The
area of the sedge wedand where
A.
m"
kingsii occurred 491,040 and
an
is extrapolation of
the data suggests
the existence of approximately 42,000
individuals growing
in the Salina
The
Wedand
<
population was observed on dry ground
with 1000
individuals a
in
m
X
open
3 3 area with a few scattered
individuals observed
along
a path
to this site.
—
Diochon
aL Agalinis
2003J et kingsii 183
,
and
A. Habit of mature plant with flowers, fruits
Figure Agalinis kingsii. (f),
2.
=
branches Scale 4 cm. B. Stem section indicating terete transverse
lateral (a).
= =
section. Scale 0.5 cm. C. Leaf. Scale 2 cm. D. Section of flower showing two
stamens
—
cm
dehiscent
on Scale 0.4 Partially fruit
dorsally petal tips.
=
cm.
Mature Scale 0.05
F. seed.
when
clumped and
Agalinis kingsii had a distribution located, there
were 2-28 m^. In the Salina A, kingsii could be found
individuals in
1
stem submerged standing water, but was gen-
with the base of the in
± cm
found 4.2 0.9 above the water table. Agalinis kingsii was
erally
common
and
most
jamaicense community (Table Individuals were located
the C. 1).
184 Rhodora
[Vol. 105
Figures 3-6. Scanning electron microscopy
of seeds of Agalinis
kiniisii. 3.
=
Whole
seed. Scale bar 100 ^m. Shape and
4. relative depth of outer seed coat
cells
=
and
pattern of wall thickening. Scale bar 50
^im. 5. Surface features of radial walls
(arrows)
-
50
^tm.
(arrows) 50 um.
m
frequently (74.3%) on the side of small (< 5 diameter) Conocarpus
erectus-Cladium
jamaicense
tree islands. Agalinis was
kingsii found
=
associated with jamaicense
C. [frequency
100%], Eleocharis
(f)
cel-
=
=
hilosa Torr. (f 54.5%), Metastelma palustre
(Pursh)
Schltr. (f 8.8%),
1
bifl 3%), and Acrostichum
=
aureiun
L. 3%).
(f
Growth
time from emergence
to flowering was 16-21
days.
Flowering
of each pair of buds was
consecutive (1-2 days between
and each was
pairs) pair viable for day. Accordingly,
1 Agalinis
kingsii
probably began emerging
in mid-April and continued
until early Sep-
tember. Flowering began May
in early and climaxed Upon
in July.
emergence, growth A
of the peduncle was
rapid. raceme formed and
beg n produce
to flower buds. Each
pair of buds
(or single for
the terminal bud), flowered
in the eariy morning, which common
is in
genus
the (Dieringer 1991, 1992). Flowers wilted and
detached
in the
afternoon on the day of emergence. Seed began
set approximately
18
—
Diochon
2003] Agalinis
et kingsii 185
al.
.
Table Frequency
1. table for presence of past year(s) individuals, ants on stem or
N =
in corolla, defoliation, and general habitat for Agalinis kingsii. 100.
Ecological Feature Frequency
{%)
Presence of
past year(s) individuals 90
Presence of ants on stem or in corolla 99
Presence of defoliation 47
m
Presence on small tree islands r< 5 78
m
medium
Presence on (5-10
tree islands diam.) 15
m
Presence on large tree islands (> 10 diam.) 6
The
and
Individuals from the previous year(s), as evidenced by dead standing
biomass, were present at 90.1% of the sites where Agalinis kingsii oc-
curred (Table There was evidence of defohation on 46.5% of plants,
1).
larvae
Pupae
Wetland
were only
entering the corollas during the study. Flightless ants the
insects observed entering the corolla and they were present in the corolla
99% examined
or on the stem of of the individuals (Table Ants,
1).
Bagged
covered in pollen, were regularly seen exitmg the corollas.
1-2
and ovary detached days.
flowers did not the after
self-fertilize
Several environmental factors were significantly correlated with
showed
growth, and number of flowers per plant significant cor-
the
with
relations with size. Percent shade at the soil surface correlated
= <
0J53,p and distance from the plant base
individual height 0.05),
(r
to the water table correlated with plant height from base to tip of the
= <
As number on
peduncle p well, the of flowers the
0.378, 0.05).
(r
= <
-0.301, p
peduncle correlated with height of the plant (r 0.05).
These may have significant hnplications for species per-
relationships
forthcoming
sistence and their importance will be addressed in the
discussion.
DISCUSSION
This account of the biology and the life history of Agalinis kingsii
designing more detailed ecological studies, as well as in
will aid
in
management
and strategies for A. kingsii
developing long-term survival
on
on Grand Cayman. The following discussion will focus under-
standing species-environment interactions, in the context of species
Rhodora
186
[Vol. 105
management
rarity, to further assist in the design of a plan
encourage persistence of the species.
The on
rarity of Agalinis kingsii the island
This
Thus
Mangrove Wetland
that suitable in terms
is
rm
was 100%
shade at the soil surface, but dead, overlying vegetation or
dense stands of Cladium jamaicense imposed The
typically shade.
this
data suggest that lower light at germination results in a taller individual
However,
at maturity. the taller the plant, the fewer flowers present
on The
the peduncle. relationship implies that, as competition for light
increases, reproductive of
fitness the individual decreases.
If fitness
may
is decreased, then there be fewer individuals recruited into these
small, rare populations.
many
known
Concomitantly,
rare species are to benefit from
disturbance (Grigore and Tramer 1996; Hartnett and Richardson
1989;
Jacobson Watson
et al. 1991; Lesica 1999; et al. 1994) and Agalinis
kingsii does not appear be an
to exception. Agalinis
kingsii in the Salina
was
found an (<
in area frequently 10 years) affected by
Fire
fire.
woody
growth
constrains the of species in the Salina and removes dead
an
The
recurrin
term stability of A. kingsii populations on Grand
The
Ions-term
Wetland,
without
recurrin
Man
plants in the Central
Wetland were found
very
in a limited
by
annually the Mosquito Research and
MRCU
maintenance
Disturbance, especially by fire and clearance, removes and
litter
and
The
table.
t
i
disturbance
disturbance
In the Salina, Agalinis kingsii was most often found growing
in the
Conocarpus
erectus-Cladium
jamaicense
community.
This community
differs from other communities
all in the sedge wetland
in soil
its
pH, water salinity, and distance from the water table (Diochon, unpubl.
Any
data). commercial developments undertaken mmpr
in the northea^^t
—
Diochon
2003]
et Agalinis kingsii 187
al.
of Grand Cayman have
the potential to influence hydrographic features
may
in the Salina. Alterations to the water table have a dramatic
effect
on community
structure, possibly similar to the alarming modifications
to the vegetation structure in the Florida Everglades subsequent
to
development
in the surrounding area (Jordan et 1997; Loveless
al.
Although Cayman
1959). the populations of A. kingsii on Grand are
may
small, but appear they be due narrow
stable, at risk to their geo-
graphic and environmental
range.
Conservation measures should be taken to ensure species survival.
Such
measures could include: continuous monitoring of the status of
1)
the populations; 2) a continuation of current disturbance regimes in the
Mangrove
Salina and Central Wetland; establishment of a seed bank;
3)
and Queen
4) introduction of the species to the Elizabeth II Botanic
Cayman
on Grand The
Park, located Island. authors are hopeful that this
account might encourage further systematic analysis of Agalinis kingsii
confirm endemic
to
status.
its
ACKNOWLEDGMENTS. The acknowledge
authors gratefully the finan-
Cayman The
cial support of the National Trust for the Islands. authors
also thank V. Partridge for assistance with scanning electron micros-
copy. This work was supported by research grants from the Natural
Canada
Sciences and Engineering Research Council of D.J.G.
to
LITERATURE CITED
A moiphology
Canne, M. 1979. scanning electron microscope study of seed
light
J.
281-296.
in Agalinis (Scrophulariaceae). Syst. Bot. 4:
Tomanthera and
Brachystigma,
1980. Seed surface features in Aiireolaria.
.
241-252.
South Kmrncon Agalinis (Scrophulariaceae). Syst. Bot. 5:
certain
Cayman
Da
VIES, E. 1994. Rare and endemic plants, animals and habitats in the
J.
527-541. M. A. Brunt and E. Davies,
Islands and related legislation, pp. In: J.
Kluwer Academic
The Cayman Natural History and Biogeography.
eds.. Islands:
The
Netherlands.
Publishers, Dordrecht,
flowering time and reproductive success
DiERTNGER, G. 1991. Variation in individual
Amer. 497-503.
Bot. 78:
(Scrophulariaceae).
oi Agalinis J,
strictifolia
and seed populations of Agalinis
effectiveness set in
1992. Pollinator
.
Amer. Bot. 79: 1018-1023.
(Scrophulariaceae). J.
strictifolia
AND
and
{Ranunculus prasinus): Ecology, conservation status intro-
buttercup
Township Lagoon Nature Reserve, Tasmania. Austral. Ecol.
duction to the J.
347-351.
22:
The
Tramer. 1996. short-term
Areas
perennis Nat.
(L.).