Psychophily and Evolutionary Considerations of Cadaba Fruticosa L. (Capparaceae)

5 Pages·2002·3.1 MB·

by  J S R Aluri

PSYCHOPHILY AND EVOLUTIONARY CONSIDERATIONS
OF CADABA FRUTICOSA (CAPPARACEAE)
L. 1
J.S.R. Aluri and S.P. Rao2
Key words: Cadabafruticosa androgynophore, nectarial tube, Colotis eucharis,
,
C. danae, psychophily, co-evolution
Cadabafruticosa is a perennial shrub, which flowers almost round the year. Floral characters,
such as the opening of the flower during early hours of the day, green colour of the flower, a
nectarial tube with good amount of nectar, and this tube along with the androgynophore and
petals serving as landing place for the probing flower visitors, conform to psychophily.
C. fruticosa breeds through geitonogamy and xenogamy only, and the pollination is effected
exclusively by pierid butterflies, namely Colotis eucharis, C. danae and Anaphaeis aurota. This
study concludes that Cadaba and Colotis have co-evolved and any disturbance in the habitat is
bound to affect both.
Introduction flower and the foraging details of pierid
butterflies are presented and discussed from the
Certain plant species possess highly perspective ofpsychophily and co-evolution.
specialized floral forms and structures associated
with particular species of insect pollinators. Material and Methods
Specialization nearly always tends towards
enabling the plant to adapt to a limited range of Cadabafruticosa plants growing wild near
pollinating insects. The specialized forms of the Indira Gandhi Zoological Park at
N
plants develop through morphological Visakhapatnam (17° 42' and 82° 18' E) were
adaptations over a period oftime. observed periodically. The phenology of their
The specialized floral forms adapted to flowering was recorded. To study the flower
butterfly-pollination have been scantily reported production and life of an inflorescence, the
in literature (Cruden and Hermann-Parker 1979, opening of flowers of20 marked inflorescences
Dronamraju 1960, Dronamraju and Spurway were recorded every day. Floral events, such as
1960, Hawkswood 1985, Ilse and Vaidya 1956, flower opening and anther dehiscence were
Jennerston 1984, Khare 1975, Levin 1972, Reddi recorded through continuous observation. The
and Meerabai 1984). These workers showed that nectar, accumulated in flowers covered with
the butterflies could serve as efficient pollinators, butter paper bags, was quantified usinggraduated
because the floral forms are specialized for micropipettes. Its sugar concentration and
foraging exclusively by them. composition were determined by a refractometer
In the present study, it was found that an and paperchromatography respectively. Presence
adaptive relationship existed between the flowers of proteins and amino acids was determined by
of Cadaba fruticosa and the pierid butterflies spot tests as per Baker and Baker 973) Method.
(1
i.e. both partners exhibit interdependency. Number of pollen grains per anther, pollen
Structural and functional aspects of C. fruticosa viability, stigma receptivity and mode of
reproduction, natural fruit set, seed set and
'AcceptedNovember,2001
fecundity were determined as per Aluri and Reddi
departmentofEnvironmentalSciences,
AndhraUniversity, Visakhapatnam 530003, (1994) and Aluri et al. (1998). butterflies of
AndhraPradesh,India. the Indian region (Wynter-Blyth 1957) was used
JOURNAL, BOMBAY NATURAL HISTORY SOCIETY, 99(1), APR. 2002 59
PSYCH0PH1LYANDEVOLUTIONOFCADABAFRUTICOSA
L.
to identify butterflies captured at flowers of C. Floral Events: Flowers begin to open
fruticosa. The number of foraging visits made slowly from 0130 hrs and proceed to unfold the
in a single foraging bout was recorded for each sexual organs in about 2!4 hours. The flowers
butterfly species, and number ofvisits per minute with exposed sex organs are available from
were counted using a stopwatch. The relative 0345 hrs onwards on sunny days and an hour
frequency of visits of different butterfly species later on cloudy and rainy days. Anther dehiscence
was determined through censuses on different occurs after sunrise at 0730 hrs in flowers under
days at different plants. The behaviour of sunshine, and an hour later in flowers which are
butterflies atthe flowers was also noted carefully. in shade. The pollen grains are spheroidal with
The floral characters and foraging behaviour of psilate exine, separable into two size classes,
butterflies were thoroughly examined for their 28 pm and 19.4 pm. Their number per anther
adaptive relationship. ranged from 7,870-8,240 (x - 8,080). In vivo
tests showed that the pollen grains remain viable
Results for 27 hours after anther dehiscence; the grains
stored for 1 5 hours have 80% fruit set. Pollen-
Flowering Phenology: It is a perennial ovule ratio is 3000:1. In the early flower-life,
shrub which flowers almost round the year. the style and stigma are curving while the
Flowering ofdifferent conspecific individuals is dehisced anthers stand erect. Gradually, the
largely synchronous during the rainy season from stigma uncurves, stands erect and attains equal
June to September, and asynchronous during the height with the stamens at 1100 hrs and remains
rest ofthe year. Intense flowering occurs during so till the flower withers. In vivo tests showed
the rainy season. The inflorescence is a fascicle that the stigma receptivity lasts for 89 hours. The
with solitary and axillary flowers, and bears an nectar secreting tubular structure secretes 5 pi
=
average of9 flowers that mature over 14-30 (x ofnectar during the life ofthe flower. The sugar
22) days. The mature flower buds that arise from concentration of the nectar varied from 18 —to
the axial point do not all mature on the same day. 26%. It contained three common sugars
Flower Morphology: Flowers pedicellate, sucrose, glucose and fructose, in that order of
oriented horizontally. Thalamus elongated into dominance. The nectar also contained amino
a slender structure on which floral parts occur at acids with a histidine score of 5.5 and proteins.
different levels. Androphore is a part of the The stamens dropped off after 36 hours, sepals
thalamus between the perianth and the stamens, and petals after another 36 hours. Then the
whereas gynophore is present between the stigma gradually withered and dropped off 20
stamens and the gynaecium. The entire structure hours later. The nectar harbouring tubular
is known as an androgynophore. Additionally, structure remained throughout fruit formation
there is a nectar-secreting tubular structure and fell off subsequently.
separated from the base ofthe androgynophore. Breeding behaviour: Hand-pollination
Four free sepals arranged in two whorls of two tests for the modes of breeding showed that the
each (two median sepals in the outer whorl and plant does not breed through autogamy but
two inner sepals transverse). Four free, clawed through geitonogamy and xenogamy;
petals arranged in one whorl alternate with the geitonogamy is less successful than xenogamy
four stamens. Gynaecium raised up on a (Table 1). The fruiting success rate in open-
prominent gynophore, bicarpellary, syncarpous, pollinated flowers is limited, compared to the
unilocular, with an average of ovules arranged success rate of hand-pollinated flowers
1 1
on the parietal placentation. (Table 2).
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Table
1
RESULTS OF BREEDING EXPERIMENTS FOR CADABA FRUTICOSA
Treatment No. of No. of No. of Fruitset Seedset Fecundity
flowerspollinated flowerssetfruit ovulessetseed (%) (%) (%)
Autogamy 25 0 0 0 0 0
Geitonogamy 25 21 126 84 54 46
Xenogamy 25 23 207 92 82 75
Cadabafruticosa. They foraged for nectar from
Table2 0630-1500 hrs, with intense activity between
NATURAL FRUIT, SEEDAND FECUNDITY RATES 0900 and 1200 hrs. Ofthese, Colotis eucharis is
IN CADABA FRUTICOSA
the most frequent and regular forager and made
Studyarea No. of Fruitset Seed set Fecundity an outstanding percentage of visits during the
'
flowers (%) (%) (%) study period. C. danae came second, and made
observed
more visits than A. aurota (Table 3).
OutsideZooPark 145 14 76 16 Colotis eucharis and C. danae, with an
mm
InsideZoo Park 189 5 58 3 average proboscis length of 17 each and A.
InteriorsofZoo Park 98 15 93 8 aurota with an average proboscis length of 20
mm
probed and succeeded in obtaining the
Table3 nectar from the nectarial tube (Table 4). To
PERCENTAGE OF BUTTERFLY SPECIES VISITS obtain the nectar, butterflies land on the nectarial
TOCDABA FRUTICOSA FLOWERS
tube itself or the androgynophore or petals. In
this case, they landed mostly on the
Dateof Mean Mean Colotis Colotis Anaphaeis
observation temp. relative eucharis danae aurota androgynophore. Contact between anthers and
humidity stigma, and the wings of foraging butterflies
takes place if they use the androgynophore or
Oct. 1999 28.3 67 70 20 10
1,
Nov. 18, 1999 25.6 74 73 13 14 nectarial tube; even this contact is achieved only
Nov. 30, 1999 25.2 83 91 7 2 when the gynaecium is erect and stands parallel
Dec. 11, 1999 24.3 68 90 8 2 to the level of the anthers. No such contact is
Apr. 9,2000 25.6 83 49 19 32
made if the butterflies land on the petals.
Examination of the 119 foraging visits of
Table4 butterflies to the 20 open flowers indicated that
PROBOSCIS LENGTH OF DIFFERENT BUTTERFLY wing contact with the anthers and stigma was
SPECIES VERSUSNECTARIALTUBE LENGTH
made in only 66 and 47 visits respectively, while
OF CADABA FRUTICOSA
in 6 visits no contact was made with either. The
Butterflyspecies No. of Mean Nectarial butterflies visited an average of2-4 flowers per
samples (mm) tubelength foraging bout. C. eucharis foraged more flowers
(mm)
per minute compared to C. danae and A. aurota
(Table 5). All three butterfly species foraged
Colotiseucharis 5 17
C. danae 5 17 10 flowers of different conspecific plants very
Anaphaeisaurota 5 20 frequently. Only those visits where there was
contact between the stigma and anthers resulted
Flower-visitors and pollination: The in pollination. Since the plant lacks autogamy,
pierid butterflies Colotis eucharis, C. danae and such visits are required to bring about either
Anaphaeis aurota are the exclusive foragers on geitonogamy or xenogamy.
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u
PSYCHOPHILYANDEVOLUTIONOFCADABAFRUTICOSA
L.
Table5 same or conspecific plants is imperative for
TIME SPENT BYTHE BUTTERFLIES ATTHE
geitono- or xenogamous pollination.
FLOWERS OF CADABA FRUTICOSA
The flowers of C. fruticosa with
Butterflyspecies No. of No. of Average psychophilous characters have been observed to
flowers visits time be foraged and pollinated exclusively by three
visited per spent pierid butterfly species, namely Colotis eucharis
in asingle minute (x) perflower ,
C. danae and Anaphaeis aurota. The foraging
bout (x) (sec)
behaviour, mobility rate and foraging frequency
Colotis eucharis 4.0 6.5 1.2 of these three butterflies were seen to effect
C. danae 2.0 4.6 2.0 geitono- and xenogamous pollination, and on this
Anaphaeis aurota 2.3 3.3 3.1
basis, these butterflies may be treatedas exclusive
pollinators. However, C. eucharis with its greater
Discussion foraging frequency is a dominant pollinator. The
nectarial tube of the flower is perfectly tailored
Butterfly pollination has been reported in to the length ofthe butterfly’s proboscis, enabling
Rhianthus hirsutus (McLean and Cook 1956), C. eucharis to withdraw the nectar easily while
Asclepias syriaca (Percival 1965), Phlox species excluding other flower-visitors. Although the
(Grant and Grant 1965, Levin and Berube 1972), flower is exclusively suited for butterfly
Dianthus and Gymnadenia (Proctor and Yeo pollination, butterflies do not effect pollination
1972), Anguria (Gilbert 1975), Platanthera in each visit. Ofthe total visits, only 40% effect
ciliaris (Smith and Snow 1976), Caesalpinia pollination, 55% carry pollen and 5% simply
pulcherrima (Cruden and Hermann-Parker deplete nectar. The butterflies contact the stigma
1979), Cnidoscolus urens (Bawa et al. 1983) and and anthers with their wings only, and this
Tridaxprocumbens (Balasubramanian 1989). In contact is directly related to the place of landing
Cadabafruticosa also, floral characters such as on the nectarial tube, androgynophore and petals,
opening ofthe flower during daytime, production and also to the relative position between them.
of a good amount of nectar, a separate nectar- The butterflies effect pollination or carry pollen
hosting tubular structure, and a nectarial tube, only if they use either the nectarial tube or the
androgynophore and petals providing a platform androgynophore. Even this pollination is effected
for landing, all conform to psychophilous only when the gynaecium is erect and stands
pollination syndrome sens Meeuse and Morris parallel to the level of the anthers. These
(1984). limitations, and the observed foraging frequency
C. fruticosa exhibits weak protandry and of butterflies, are bourrd to influence natural
the anthers are viable for a short period when reproductive success. The natural fruit set, seed
compared to the lengthy duration of stigma set and fecundity rates recorded in the study are
receptivity. This floral sexual behaviour in tune with the above observations.
facilitates autogamy for a briefperiod; but hand Nevertheless, and whatever be the limitations,
pollination tests showed the absence ofautogamy. C. fruticosa is an excellent example of
Further, the hand pollination tests performed for psychophilous pollination syndrome.
geitonogamy and xenogamy showed that the C. fruticosa flowers almost throughout the
plant is capable of breeding through these two year and the butterflies forage on this plant all
modes of reproduction, xenogamy being more through the year for their nectar requirement,
successful. The study of breeding behaviour while occasionally foraging on associated plant
reveals that pollen flow between flowers of the species such as Tridax procumbens Justicia
,
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L.
procumbens Borreria hispida and Lantana Colotis as a co-evolved system. The A. aurota -
,
camara, which flower largely in the rainy season. C. fruticosa system appears to be a one sided
The study clearly indicates that Cadabafruticosa adaptation, as the plant allows only butterflies
is the adult’s principal nectar host plant. Further, ofA. aurota to feed on its nectar and pollinate it,
it is foundthat the two Colotis butterflies oviposit and not the larvae.
on the leaves and flower buds of C. fruticosa The C. fruticosa-Colotis relationship
and their larvae feed on the same leaves. On the appears to be a specialized system and any
other hand, Anaphaeis aurota does the same on disturbance in the habitat is bound to affect the
Capparis spinosa which occurs in the same study existence of both. It is imperative to protect the
,
area. Therefore, the study considers the plant habitats where these two partners occur, in order
Cadaba and the pierid butterflies belonging to to ensure their perpetuation.
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