POLLINATION ECOLOGY OF
SEVEN SPECIES OF
BAUHINIA L.
(LEGUMINOSAE:
CAESALPINIOIDEAE)^
OmairaHokche^andNelsonRamirez^
Abstract
Pollination
and
floral
biology
of
seven
species
of
Bauhinia
were
analyzed
between
1982
and
1983
in
different
Venezuelan
plant
communities.
Bauhinia
species
are
grouped
two
insections:
Pauletia,
which
includes
trees,
and
Tylotaea,
which
includes
lianas.
The
species
of
sect.
Pauletia
included
in
this
study
(B.
aculeata,
B,
mult
iner
via,
B.
pauletia,
B.
ungulata)
have
comparatively
large,
white
flowers,
while
the
species
of
sect.
Tylotaea
{B.
glabra,
B.
guianensis,
B.
rutdans)
exhibit
different
colors
of
flowers
and
variations
in
form
and
color
of
the
upper
petal.
Nectar
analyses
were
made
for
six
Bauhinia
species
for
sugar
and
amino
acid
composition.
The
species
of
sect.
Tylotaea
produce
less
nectar
with
higher
a sugar
concentration
than
those
of
sect.
Pauletia.
Hexose
dominant
is
in
species
of
sect.
Pauletia
except
in
Bauhinia
aculeata,
where
sucrose
Is
dominant.
The
species
of
sect.
Tylotaea
have
comparatively
small
diurnal
flowers
and
are
visited
great
by
a variety
bees,
of wasps,
butterflies,
and
hummingbirds;
those
sect.
of Pauletia
are
mainly
nocturnal
and
bat-pollinated,
but
Bauhinia
aculeata
showed
different
behavior
and
could
be
intermediate
between
the
two
sections.
The
flower
morphology,
floral
biology,
pollinator
species,
nectar
composition,
and
secretion
tend
to
be
associated
with
the
life
form
of
the
two
sections
of
Bauhinia.
In
an
ecological
context,
caesalpinioid
legume
lous,
and
Arroyo
(1981
suggested
)
that
many
other
flowers
are
less
specialized
than
their
mimosoid
and
species
of
Bauhinia
are
probably
sphingophilous.
papilionoid
counterparts.
Caesalpinioid
flowers
are
The
flowers
of
neotropical
Bauhinia
species
exopen,usuallywithexposedpollenandnectaravail-hibitgreatdiversityinform,size,andcolor,which
abletospecializedandnonspecializedpollenvec-hasbeenpoorlystudiedfromanadaptiveviewtors.Onlyinsomeoftheadvancedgeneraarepoint.ThespeciesofBau/^mmaregroupedinthree
conservation
and
pollinator
selection
evsections
according
to
Stuard
da
Fonseca
Vaz(
1979).
ident
(Arroyo,
1981).
The
Caesalpinioideae
exhibit
Section
Pauletia
comprises
trees
and
shrubs;
in
agreatvarietyofpollinatingagentsandmecha-contrast,speciesofsects.TylotaeaandSchnella
nisms
with
an
entomophilous
trend
(Arroyo,
1981).
comprise
climbing
plants.
For
all
Bauhinia
species
For
example,
many
Cassia
species
are
bee-pollistudied,
the
flowering
periods
occur
during
the
dry
season.
nated(Delgadoetah,1977).Inthissense,orniThe
following
study
provides
information
about
thophily
and
chiropterophily
are
scarce
(Arroyo,
thefloralbiologyandpollinatoractivityofseven
1981).
Studies
of
chiropterophily
have
paid
comparaspecies
of
Bauhinia
belonging
to
sects.
Pauletia
livelymoreattentiontothelegumesoftheNewandTylotaeafoundindifferentplantcommunities
WorldthanoftheOldWorld(Frankie&Baker,ofVenezuela.Thechemicalcomposition,secretion,
1974;Heithausetal.,1974,1975;Howell,1975;andvolumeofthenectarsproducedwereanalyzed
Bernhardt,1982;Ramirezetal.,1984;Prance,forcomparingbothsectionsofBauhinia,
1985).
Some
neotropical
Bauhinia
species
are
bat- Dates
and
Methods
pollinated(Heithausetal.,1974;Ramirezetal.,
Bauhinia
is
widely
distributed
in
several
eco1984).
However,
Vogel
(1954)
reported
that
BauhiniagalpiniiandB.mucronataaresphingophi-systemsinVenezuela.Thelocalitiesforthisstudy
We
' thank
S.
Tillet,
W.
S.
Armbruster,
S.
Renner,
P.
Berry,
A.
Castillo,
and
P.
Bernhardt
for
comments
on
the
manuscript.
We
are
also
especially
grateful
to
R.
Wunderlin
for
help
with
plant
identifications,
and
to
F.
Fernandez
Yepez,
J.
A.
Clavijo,
G.
C.
Eickwort,
and
0.
Mielke
for
help
with
insect
identifications.
Special
thanks
are
due
H.
Baker
and
I.
Baker
for
the
chemical
nectar
analyses.
We
extend
gratitude
to
Y.
Brito,
A.
Seres,
N.
G.
Leal,
C.
Gil,
M.
Lopez,
L.
Camero,
H.
Farinas,
and
S.
Gomez
for
assistance
in
the
field.
Departamento
de
Botanica,
Escuela
de
Biologia,
Facultad
de
Ciencias,
Universidad
Central
de
Venezuela,
Aptdo.
47114,
Caracas,
Venezuela.
Reprint
requests
Ramirez.
N.
to
Ann.MissouriBot.Card.77:559-572.1990.
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Hokche
Ramirez
&
Pollination
Ecology
of
Bauhinia
Species
Volume
77,
Number
3
1990
were
chosen
in
accordance
with
the
flowering
and
fruiting
periods
indicated
on
specimens
in
the
Herbario
Nacional
de
Venezuela
(VEN)
and
through
field
observations
(Table
1)
in
various
regions.
Fieldobservationsweremadeofthelifeform
andheightofplants,andpollinationandfloral
biology
were
analyzed
in
1982-1983
during
the
flowering
and
fruiting
periods
of
each
species.
00
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CHARACTERISTICS
FLORAL
The
floral
parts
(corolla,
pistil,
stigma,
and
petal
lengths)
were
measured
using
samples
preserved
in70%ethanolfor20flowersfromfivetoten
individual
plants
of
each
Bauhinia
species.
CM
o
§
? E CM
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561
FLORAL
BIOLOGY
Flowers
were
observed
in
situ
to
record
anthesis:
inflorescences
with
buds
about
to
open
were
marked
before
anthesis,
and
progress
of
anthesis
was
observedevery30minutes.Thepatternofnectar
production
was
measured
periodically
with
microcapillariesinsertedinthehypanthiumcavityof
bagged
flowers.
Solute
concentration
of
the
nectar
wasmeasuredwithamanualBausch&Lomb
refractometer
(range
030%).
The
presence
of
sugar,
proteins,
amino
acids,
lipids,
and
other
compoundswasdetectedfromnectaronfilterpaper
byDrs.Irene&HerbertBaker(Universityof
California,
Berkeley,
California,
U.S.A.).
Pollinator
activity
was
observed
and
recorded
during
five
days
foreachBauhiniaspecies.Thevisitingagents
observed
were
captured
with
hand
nets
and
mist
nets
and
were
examined
for
pollen
load.
Results
MORPHOLOGY
FLORAL
The
inflorescences
of
Bauhinia
are
axillary
and/
or
terminal.
The
sect,
Pauletia
species
have
comparatively
large,
white
flowers;
the
stamens
are
dimorphic:fivearelargeandfiveshort(Table2).
However,thistrendwasnotclearforallspecies
ON of
this
section.
In
Bauhinia
pauletia
short
stamens
are
represented
by
five
staminodes.
The
flowers
of
CO shortandlongpistilswerefoundonthesametree
ofB.aculeata.Theshortpistilflowersarenot
locatedintheinflorescence.In100flowersoffive
individuals
the
large/short
pistil
ratio
was
15:1.
Floral
dimorphism
is
associated
with
pistil
length,
with
significant
a
difference
between
the
two
morphs
(tjg
o
=
12.26;
P
<
0.0005).
The
short
pistils
are
as<
sociatedwithreductionofthegynophore(X=
1.12,SD=0.24inlarge-pistilflowersandX=
0.54,SD=0.09inshort-pistilflowers),ofstyle
Annals
of
the
Missouri
Botanical
Garden
562
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Volume
77,
Number
3
1990
2.40,SD=0.20;X=1.08,SD
0.18,
:tivelv).
The
number
of
ovules
ner
similar
in
both
morphs
but
the
ovules
of
short-pistil
flowers
are
abortive.
In
Bauhinia
multinervia
there
were
no
floral
variations
(Table
2).
The
flowers
of
both
sections
are
zygomorphic,
the
petals
are
diff^erent
in
form
and
size.
In
general,
theinferiorandlateralpetalsaresimilarinform,
while
their
areas
are
slightly
different
(Table
3).
Theflowersofsect.Tylotaeaaresmallerthan
thoseofsect.Pauletia;theaverageflorallength
variesfrom1.83to2.26cm.Thegynophoreand
hypanthium
are
also
shorter
than
in
sect.
Pauletia.
InBauhiniapauletia,B.multinervia,andB.
ungulata,oneortwoflowersopenpernightper
inflorescence
(Table
4).
Antbesis,
petal
expansion,
occursatduskbetween1700and1900hours,
andtheprocessisquickandsynchronic(Fig.1).
Bauhinia
aculeata
has
nocturnal
antbesis
but
is
comparatively
asynchronous
(2100-0300)
and
showedtwopeaksduringantbesis(Fig.1).Inthe
species
of
sect.
Pauletia
anthers
dehisce
before
anthesis.
In
the
species
of
sect.
Tylotaea
(lianas),
anthesis
diurnal,
is occurring
approximately
between
0730
and1130hours.Petalexpansionisslower,and
the
number
of
opened
flowers
per
inflorescence
per
dayishigherthanintreespeciesofsect.Pauletia
(Fig.1).ThepinkflowersofBauhiniarutilans
showedtwopeaksduringanthesis(Fig.1).AlthoughwedidnotrecordanthesisinBauhinia
guianensiSy
occurs
it
in
the
morning
between
0900
and1100hoursandisprobablysimilartothatin
B.
rutilans
(pers.
obs.).
563
Hokche
Ramirez
&
Pollination
Ecology
of
Bauhinia
Species
{X
SECRETION
NECTAR
In
the
arborescent
Bauhinia
species
nectar
is
produced
and
accumulated
in
the
hypanthium
of
flowers.
Nectar
production
starts
immediately
after
anthesis;however,inB.multinerviatherewasa
little
nectar
before
anthesis.
The
average
volumes
werehighforB.multinervia(102.42ml)andP.
pauletia
(47.32
ml);
nectar
concentration
was
relatively
low
and
similar
in
the
species
studied
(Table
5).
The
nectar
of
B.
aculeata
was
produced
during
day
and
night;
the
average
nocturnal
production
is
significantly
less
than
the
diurnal
production
(t^,
=8.55;P<0.0005).Thisdifferencewasassociatedwithadiurnalfloralactivityhigherthan
nocturnal.
The
solute
concentration
of
nectar
increasedfromthefirsthoursafteranthesisuntil
midnightinB.pauletiaandB.multinervia,while
inB.aculeatathehigherconcentrationofnectar
occurred
during
the
night
period.
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volume
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Number
3
1990
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Annals
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566
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Volume
77,
Number
3
1990
duced
can
exceed
the
volume
of
the
hypanthium
cavity,
and
without
pollinating
visits,
nectar
starts
dripping
down
or
out.
Bauhinia
aculeata
produced
nectarfor19hours,whereasinB,pauletiaand
multinervia,
B.
production
lasted
approximately
13hours.Thesecretionrate,estimatedasthe
volumeproducedpertimeunit,washighestinB.
multinervia{X=7.88ml/hr.),followedbyfi.
pauletia{X=3.61ml/hr.)andB.aculeata(X
=0.27ml/hr.).Thefirsttwospeciesarecharacterized
by
nocturnal
secretion.
Significantly
in
B.
aculeata
no
difference
between
diurnal
(0.17
ml/hr.)
and
nocturnal
(0.22
ml/hr.)
secretion
rates
was
found.
The
species
of
sect.
Tylotaea
produced
less
volumeofnectarwithahighersugarconcentration
thanthoseofsect.Pauletia(Table5).InBauhinia
glabrathevolumewaslessthantheminimalcapacityofmicrocapillariesandonlyastickysapat
thebaseofstamensandpistilwasdetected.In/i.
rutilans
nectar
secretion
took
place
during
seven
hoursandtheratewas0.27ml/hr.,similartothat
inB.aculeata(sect.Pauletia)^withatotalof1.88
ml
per
flower.
Hokche
Ramirez
&
Pollination
Ecology
of
Bauhinia
Species
k>oi
soo-lo
50100-
567
glabra
8(16
Nrutllant
6
18
NpQUlfttla
B.
40
N>
o
lE
0)
O
30-
oculAata
8.
N-II2
00
97
iao8 13:0016:00I9O0ee^oOt'OO
Time
(hr)
Figure
1.
Anthesis
expressed
as
the
percentage
of
open
flowers
during
half-hour
intervals.
cumulative,
%
D
non-cumulative.
%
COMPOSITION
NECTAR
The
nectar
of
six
Bauhinia
species
contained
rheproportionsof20aminoacidsanalyzed
proteins,
amino
acids,
phenols,
and
alkaloids,
but
differed
in
the
nectar
of
different
Bauhinia
species,
nolipidsweredetectedinthenectarofanyofthe
andvariedfrom3to>10,usingarelativescale
species
studied
(Table
6).
Alkaloids
appeared
in
low (Table
6).Thescalefrom1to10isbasedon
quantitiesonlyinthenectarsofB.aculeataand
standard
concentrations
of
histidine.
A
value
of
10
rutilans.
B.
is
equivalent
to
3.9
mg
histidine/ml,
and
each
Onlytracesofproteinweredetectedinthenecsuccessive
unit
below
10
represents
a
halving
of
tarofB.multinervia(sect.Pauletia)^whileinB.
concentration
(9
=
1.95
mg/ml;
8
=
0.975
mg/
glabraandB.rutilans(sect.Tylotaea)itwas
ml; dsoforth)(Baker&Baker,1975).The
detected
in
low
quantities.
The
proportion
of
sugar
analyses
showed
that
there
was
no
difference
in
in
the
nectar
of
sect.
Pauletia
showed
that
sucrose
the
presence
of
essential
amino
acids.
Proline
was
isdominantinB.aculeata,whileB.multinervia
dominant
in
all
species
except
B.
multinervia.
Only
and
B.
ungulata
were
hexose-dominant
with
simone
species
studied,
B.
rutilans,
had
lysine
inthe
ilar
proportions
of
glucose
and
fructose.
The
pronectar
(Table
8).
portionofglucosewassimilartosucroseinB.
glabrabuttherewasahigherproportionofboth
POLLINATOR
ACTIVITY
sugars
than
of
fructose
(Table
7).
In
bat-pollinated
species
of
Bauhinia
the
flowers
Thereisatemporalchangeoftheproportionof
sucrose,glucose,andfructoseinthenectarsduringareexposedonthetopofthefoliage,andpetals
thesecretionperiod,withadecreaseinthepro-areseparated,leavingtheanthersexposed.The
portionofsucroseovertimeinthetreespecies.pollenadherestotheheadandventralpartofthe
At
the
beginning
of
nectar
secretion,
the
proportion
animal.
The
feeding
activity
and
hence
pollination
ofsucrosewas2.74timeshigherthan12hourslastonlysecondswiththemaximumoccurringat
laterinfi.pauletia,B.multinervia(bothsect.duskandinthefirstnighthours.Duringthevisit,
Pauletia)^
and
B.
rutilans
(sect.
Tylotaea);
when
Phyllostomus
discolor
and
Glossophaga
soricina
sucrose
decreases,
fructose
and
glucose
increase
seize
the
flowers
and
inflorescences
so
that
the
inquantityandthesucrose/glucose+fructosebranchesarebentdownbytheweightoftheanimal.
ratio
decreases
(Table
7)
Nocturnal
visits
were
made
by
Sphingidae
and
but-
Annals
of
the
Missouri
Botanical
Garden
568
Table
5.
Average
volume
and
solute
concentration
of
nectar
for
five
Bauhinia
species.
Secti
ion
Species
Patilctia
(trees)
ariilcdtn
B.
multincnid
B.
pauletia
B.
TyloUiea
(lianas)
glabra
B.
B.
rut
Hans
Total
volume
nectar
of (ml/flower)
X
SD
Range
0.95
5.03
3.96
5.81
60.37-138.01 102.42 36.41
47.32 37.12
14.18
87.44
1.06-2.36
0.24
1.88
0.57
Solute
concentration
(%)
X
Range
SD
12.0
28.0
16.4-21.0
13.0
18.0
19.35
19.34
16.23
4.85
1.62
2.07
26.0-30.0
30.00
28.25
1.81
terflies,
and
phyllostomatid
bats
were
observed
on
solampis
mosqiiitus
took
nectar
from
the
flower
fi.niiilUncrvlaandB.pauletiaflowers.Phyllusto-inthemorningbetween0600and0730hoursand
rnusdiscolorandGlossophagasoricinahatswereatduskbetween1600and1830hours,
considered
efifective
pollinators
because
they
carThe
species
of
sect.
Tylotaea
have
comparariedpollenontheirheadsandbodies(Taiale4).tivelysmallflowers,whichwerevisitedbyagreat
Duringtheday,theflowersof/?.midtinerviaandvarietyofbees,wasps,butterflies,andhurnmingB.pauletiawerevisitedbybutterflies,wasps,andbirdsduringthetimeofstigmareceptivity(Table
lUfi
hummingbirds,
though
there
was
little
nectar
and
pollen.Inaddition,B.multinerviawasvisitedbe-andPseudaiigochloropsissp.Theseinsectsartween0530and0800hoursbyPhaethornisagutirivedattheflowersposingontheinferiorandlateral
(Trochilidae)totakenectarofopenflowersfrompetals,introducingtheirbodyintotheflower,while
Bomhussp.insertsonlyitsheadintotheflower.
the
previous
night.
llift
AdifferentbehaviorwasshownforBauhinia
aculeata
(sect.
Pauletia)'.
during
the
night,
flowers
Bombus
sp.
during
the
morning.
Bauhinia
gulanensis
was
visited
by
Xyioropa
were
visited
by
Sphingidae
{Euniorpha
lahrnscae
andE.vitis)andinfrequentlybyNoctuidae.But-sp.andSynorrasurinamainthemorningand
terflies,
wasps,
bees,
and
hununingbirds
were
abunafternoon.
These
bees
carried
pollen
on
the
legs
dantduringtheday.Thebees,Xyioropa{Neoxy-andhead.Aspeciesofbutterflies{Xaslrainsignis.
Hesperiidae)tooknectaraboutnoon,butitwas
llifi
and
several
species
of
Pieridae
(e.g.,
Anteos
clorinnot
a
pollinator.
In
addition,
one
unidentified
humdai\Ganyramcnciae)carriedpollenofB.acu-mingbirdwasobservedforalongtimevisitingthe
leata.Theseinsectsinsertedtheirheadsinsidetheflowers.Bauhiniarutilanswasvisitedbybees,
flower
and
imbibed
nectar.
The
hummingbird
Chrywasps,
and
hununingbirds;
Xylocopa
sp.
and
BomTaBLE
Proportion
6.
organic
of
compounds
nectar
in six
ofBauhinia
species
(arrows
indicate
temporary
trends
anthesis).
after
Section
Phenols
Amino
acids
Species
Pauletia
(trees)
6
tr
aculeata
B.
+
10
5
multinervia
B.
3 7
tr
pauletia
B,
6
tr
ungulata
B.
Tylotaea
(lianas)
+
6 >10
glabra
B.
+ +
3 7
rutilans
B.
not
breakdown
during
the
night;
ND detected;
tr =traces;=
' suggests
abundant.
^
quantities;
+
=
moderate;
+
Alkaloids
slightly
+
ND
ND
ND
Proteins
ND
tr
ND
ND
ND
tr
+
slightly
+
scalefrom1to10ofrelative
Volume
77,
Number
3
1990
Hokche
Ramirez
&
Pollination
Ecology
of
Bauhinia
Species
569
Table
7.
Proportion
of
nectar
sugars
and
their
temporal
variation
(variations
in
time
are
in
the
direction
of
the
arrows
after
anthesis).
Sucrose/
Proportion
sugars
of
Secti
ion
glucose
+
Melezitose
Maltose sucrose
Glucose Fructose fructose
Species
Pauletia
(trees)
aculeata
B.
0.552
0.241
0.208
1.279multinervia
B.
0.005 0.111
0.167 0.211
0.329
0.446
0.368
0.460
0.203
0.413
0.188 0.516
0.279
0.463
0.206
pauletia
B.
0.349
0.246
0.153
0.016 0.006 0.185
0.443
0.350
ungulata
B.
0.233''
Tylotaea
(lianas)
0.007
0.330
0.388
glabra
B.
0.274
0.499'
B.
rut
Hans
0.365 0.558
0.234
0.369
0.208
0.224
0.573
1.261
asucrose
dominant,
hexose
'' dominant,
intermediate
'
between
and
ab.
bussp.wereabundantcollectingpollenduringtheetal.,1980),Lafoensiapacari(Lythraceae)(Samiddleoftheday.Theflowerswerevisitedfre-zima&Sazima,1975),andBauhiniaungulata
#
(Ramirez
et
al.,
1984).
In
Passijlora
mucronata
pollen
was
collected
on
their
bills.
In
addition,
the
(Passifloraceae)
anthesis
occurs
between
0100
and
flowerswereperforatedexternallyatthebaseby0200hours,withadurationoflessthan12hours
anunidentifiednectar-robbingspeciesofhum-(Sazima&Sazima,1978).Thenocturnalflowers
mmgbird.
ofBauhiniacanbeconsideredassynchronicin
anthesisbecausemorethan50%oftheflowers
open
within
30
minutes.
The
total
process
occurs
Discussion
intwoandone-halfhours,AnthesisofBauhinia
Tliemorphology,color,andscentofflowersareglabraandB.rutilansisdiurnal,unimodal,and
associated
with
size
and
behavior
of
pollinators.
asynchronous,
the
peak
of
flower
opening
involving
Chiropterophilous
flowers
are
often
white,
exposed
less
than
40%
of
the
flowers.
abovethefoliage,nectarcontinuously,shownoc-InBauhiniaacu/ea^a,anthesisisnocturnaland
turnalanthesis,andhaveadisagreeablesmell(e.g.,asynchronous,withtwopeaksoflessthan40%
Heithaus
et
al.,
1974;
Sazima
&
Sazima,
1975,
each;
this
asynchronic
anthesis
could
promote
cross1978;Vossetal.,1980;Howell&SchropferRoth,fertilization;theflowersarevisitedbyavarietyof
1981;Ramirezetal.,1984).Entomophilouspollinators.Bauhiniaaculeatashowedacombispecies,includingthoseofBauhinia,haveflowersnationoffloralfeatures;thefloralmorphology,
ofsmallersize,ofvariedcolor,fragance,diurnalnectarchemistry,timingofanthesis,andthepatanthesis,andlownectarproduction.Inaddition,ternofnectarproductioncannotbeplacedwith
bee
flowers
often
have
dense
inflorescences
(e.g.,
the
other
species
studied.
Bauhinia
aculeata
could
Bolten&Feinsinger,1978;Frankieetal.,1983).beintermediatebetweennocturnalanddiurnalpolSuch
floral
characteristics
as
flower
size
and
time
lination
because
great
a number
of
specialized
and
ofanthesisofthestudiedBauhiniaspeciescanbeunspecializeddiurnalandnocturnalfloralvisitors
related
to
their
different
pollination
systems.
The
and
pollinators
are
associated
with
this
species.
white-flowered
Bauhinia
pauletia
and
B.
multiIn
bat-pollinated
plants,
higher
production
of
nerviaarechiropterophilous,andB.glabraandnectarhasbeenreportedthaninhummingbirdB.
guianensis
are
entomophilous,
whUe
the
pink
and
butterfly-pollinated
plants,
and
nectar
producflowerswithredbractsofB,rutilanswerevisitedtioniscontinuous(Cruden,1976;Baker,1978).
frequentlybyhummingbirds,whichcarrypollen.NectarproductioninBauhiniapauletiaandfl.
In
most
chiropterophilous
species,
anthesis
seems
multinervia
is
higher
than
in
Ochroma^
Parkia,
tooccuratdusk(1800-2000hours)(HeithausetChiranthodendron,andLafoensiapacari,which
al.,1974;Sazima&Sazima,1975;Gould,1978;produce5to20ml/flowerorinflorescence(HeitLack,1978;Ramirezetal,,1984).Anthesisofhausetal.,1975;Sazima&Sazima,1975;Voss
BauhiniapauletiaandB.multinerviaoccurredetal.,1980).
at
similar
evening
hours.
The
flowers
last
one
night.
Flowers
visited
by
bees
frequently
produce
low
similartoMarkeaneurantha(Solanaceae)(Vossnectarquantities.Frankieetal.(1983)founddif-
570
Annals
of
the
Missouri
Botanical
Garden
Table
8.
Amino
acid
composition
in
nectar
of
six
species
of
Bauhinia.
Section
Species
ferentflowersizesassociatedwiththedailynectarmorefrequentatthefirsthoursafteranthesis.In
production.
These
authors
defined
moderate
nectar
contrast,
nectar
concentrations
melitophilousof
produclionas1.0to8.0fx\/dayandhighnectarornithophilousspecies{B.glabraandB,rutilans,
productionasonaveragehigherthan8.0fA/day.respectively)increasedatthemiddayhours,Tlie
In
addition,
bee
plants
with
elevated
concentrations
increase
of
nectar
concentrations
and
the
higher
ofsoluteshavesmallflowersandlownectarpro-pollinationactivitiescouldberelatedtothetemduction
(Hainsworth
&
Wolf,
1972;
Baker,
1975).
perature
elevation
during
midday
hours
and
conHowever,BauhiniaglabraandB,rutilansdiffercomitantevaporationfromthenectar.Beesand
fromthisexpectationsincetheyproducehigherhummingbirdsprefernectarupto20%or40%of
volumes
of
nectar
than
those
reported
by
Frankie
sugar
concentration
(Percival,
1974;
Baker,
1975).
The
flowers
of
sect.
Pauletia
produce
nectar
etal.(1983).Inaddition,thevisitsandpollenload
et
al.
on
Schislis
geoffroyi
(Trochilidae)
suggest
the
imduring
approximately
12
hours.
Heith
portanceofbirdsinthepollinationsystemsofB.(1974)reportedarateofnectarsecretionof0.5
rutilansatthecanopylevel,sothisspeciescannotml/hr.forthefirsthoursofproduction(from1800
beconsideredasastrictlymelitophilousspecies.to2300)inB.pauletia;however,thetotalrate
Thesoluteconcentrationofbat-pollinatedflow-ofnectarsecretionwas3.16ml/hr.Bauhinia
ersisfrequentlylow(Howell,1975,1978;Baker,pauletiaandB.multinerviashowedahigherrate
1978;Steiner,1983),andanincreaseofsolutesthanB,ungulata(Ramirezetal.,1984).The
fromearlytolaterhoursafteranthesishasbeendiff'erencecouldbeassociatedwiththegreaterflowreported,e.g.,inLafoensiapacarifrom6.8%toerandhypanthiumcavitysizesofthefirsttwo
11.0%(Sazima&Sazima,1975).Bycontrast,species.
Nectar
has
variety
a
of
nutritional
compounds
Ramirezetal.(1984)showedinBauhiniaungulataahighersoluteconcentrationimmediately(Percival,1965)andelementswithaselective
edfrom15.4%function(Baker&Baker,1975).Thealkaloidsin
before
anthesis,
which
then
d
Bauhiniaaculeata(sect.Pauletia)andB.ruti12.0%.
to
Percival(1965)foundanincreaseinsolutecon-lans(sect.Tylotaea)probablyreflectaselective
centrationwithflowerageinspeciesofsect.Ty-forceatpollinationlevel.Thehighdiversityof
lotaeaandfi.aculeata(sect.Pauletia),Thein-visitingagentspeciesinbothplantspeciescould
crease
in
nectar
concentration
can
Increase
the
be
selected
by
deterrent
compounds.
The
absence
exploitationefficiencyinflowerswithlowquantitiesofnectarproteinsinthespeciesofsect.Pauletia
of
nectar
(Hainsworth
&
Wolf,
1976).
The
nectar
is
related
to
bat
pollination
because
some
pollinating
concentrationofBauhiniamultinerviaandB,batspecieseatinsects(Heithausetal.,1975)and
pauletiaflowersdecreasedwithflowerage.Inthepollenasaproteinsource(Alvarez&Quintero,
chiropterophilousspeciesthevisitsareprobably1969;Howell,1974).Incontrast,thenectarsof
Hokche
Ramirez
&
Pollination
Ecology
of
Bauhinia
Species
Volume
77.
Number
3
1990
Table
Continued.
8.
PheO
Pro*
Amino
acids
Ser* TyrTreooTripoValo
+
+
+
+
+
+
ND
+
ND
tr
tr
+
ND
+
ND
+
tr
+
-I-i-
the
species
of
sect.
Tylotaea
have
some
proteins;
the
insects
that
visit
these
species
presumably
obtain
their
nitrogenous
requirement
mainly
from
nectar
and
pollen,
while
hummingbirds
obtain
their
nitrogenous
requirement
from
nectar.
Flowers
pollinated
by
butterflies
and
hummingbirdsarereportedasrichinsucrose,whilenectar
ofbatflowerslendstoberichinhexose(Baker,
1978),
and
the
nectar
of
bee
flowers
has
no
definite
pattern
in
sugar
proportions.
Bauhinia
multinervia,B.pauletia^andB.ungulataarehexosedominant
chiropterophilous
species
and
have
nocturnal
nectar
secretion.
In
these
species,
sucrose
decreases
with
time,
and
glucose
and
fructose
increase
simuhaneously.
This
pattern
suggests
a
breakdown
of
sucrose,
and
then
the
sucrose/glucose
fructose
+
ratios
decrease.
The
breakdown
ofsucrosecanbeconsideredanadvantagefor
pollination
because
bats
cannot
assimilate
sucrose
(Harborne,
1977).
This
pattern
has
been
found
in
B.
rutilans
but
was
associated
with
hummingbird
andbeepollination.Bauhiniaglabraisrichin
sucrose
and
glucose
and
has
an
entomophilous
pollination
system.
The
flower
morphology,
floral
biology,
pollinator
species,
nectar
composition,
and
timing
and
amount
of
secretion
are
associated
with
life
form
and
subgeneric
designation
of
the
Bauhinia
species
studied.
Thespeciesofsect.Paulctiaaretreesorshrubs,
frequently
pollinated
by
bats.
In
contrast,
the
species
of
sect.
Tylotaea
are
lianas,
pollinated
by
insects
and
birds.
The
polUnator
specificity
among
Bauhinia
species
with
similar
pollinators
is
achieved
basically
through
their
geographic
distributions.
Sympatric
distribution
and
overlapping
flowering
periodswerefoundonlyforBauhiniaspeciesof
diff'erent
sections.
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this
sense,
the
most
important
attribute
is
floral
morphology.
The
floral
characteristics
and
pollination
biology
provide
additional
characters
for
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systematics.
The
agree-
571
ment
among
reproductive
and
taxonomic
properties
could
be
related
to
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patterns
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the
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Species of Bauhinia L. (Leguminosae: Caesalpinioideae)." Annals of the
Missouri Botanical Garden 77, 559–572. https://doi.org/10.2307/2399520.
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