McMullen, Conley K.

Naranjo, Sandra J.

English

Aquatic Commons

April1994 NOTICIAS DE GALÁPAGOS 25
R.I. Bowman, M. Buson &A.E. Leviton. pacifîc
Division of the AAAS. pp 539-568.
Patton, J.L., Yang, S.Y. & Myers, p.lg7S. Genetic
and morphologic divergence among introduced
rat populations (Ranus rattus) of the Galápagos
Archipelago, Ecuador. Syst. Zool. 2 4(3):296-310.
Peterson, R.I. 1966. Recent mammal records from
the Galápagos islands. Mammalia. 30(3):441- tA5.
Sivinta-Mena" Byron. 1 988. Ecologia de la rata norue-
ga Rattus norvegicus, especie de reciente
establecimiento en Puerto Ayora, Santa Cruz,
Galápagos. Unpublished thesis, UniversidadTéc-
nica de Ambato, Ecuador.
Snell, H., Snell, H. & Stone, p. 1993. Accelerated
mortality of Opuntia on Isla plaza Sur: Another
Threat from an Introduced Vertebrate? Unpub-
lished Report, Estación Cientffica Charles Dar-
win.
Snow, D. L964. Untitled note. Noticias de Galápa-
gos. 3: p 20.
S teadman, D.W. & Ray, C .8. 1982. The relationships
of Megaoryzomys curioi, an extinct Cricetine ro-
dent (Muroidea: Muridae) from the Galápagos
Islands, Ecuador. Smithsonian Contributions to
Paleobiology. No.51.
Trillmich, F. 1 986. The future of rhe Fernandina rice
rats: extinction or captive breeding? Noticias de
Galápagos. M:15-16.
Gillian Key Biological Sciences, Manchester Met-
ropolitan Universit¡ Manchester MlsGD, UK.
EdgarMuñoz Heredia, Charles Darwin Research
Station,Isla Santa Cruz, Galápagos, Ecuador.
POLLINATION OF SCALESIA BAURT SSP. HOPKINSII
(ASTERACEAE) ON PINTA ISLAND
By: Conley K. McMullen and Sandra J. Naranjo
Previous studies in the genusScalesiahave shown
that,S. affinis Hooker f., S. helleri Robinson, S. pe-
dunculata Hooker f., and S. asperaAndersson can
reproduce by aurogamy (automatic self-pollination)
(Rick 1966; McMullen 1987, 1990). In addition, the
first three of these, as well as an unidentified species
thought to be S. reffoflexaHemsley, a¡e known to be
pollinated by the endemic carpentff bee Xylocopa
darwini Cockerell (Hymenoptera: Apidae) (Linsley
et al. 1966; Rick 1966; Eliasson 1974; McMullen
1985). The flowers of S. pedunculata onsanra Cruz
Island are alsovisitedbythe Galápagos fritillary but-
terfly Agraulis vanillae galapagensjs Holland
(Lepidoptera: Nymphalidae) (personal observation).
Pollination studies on an additional member of
this genus, Scalesia baurii Robinson & Greenman
ssp. hopkinsii (Robinson) Eliasson, were conducted
on Pinta Island from 28 June - 20 July 1990 (Fig. l).
Pintais one of the northern islands in the archipelago
that the carpenter bee does not inhabit. Fifteen indi-
viduals, located between 15-67 maltitude on pinta's
southem sþe, were selected for this study. One
hundredinfl orescences were bagged before theirflow-
ers had opened to determine if the plants could
reproduce autogamously. One hundred open-polli-
nated inflorescences were marked as well, and then
covered after being exposed for one week. All polli-
nation bags werecollectedon the lastday of the study
and fruit counts were made. Flower observations
were conducted to discover what insects made visits
NOTICIAS DE GALAPAGOS No.5326
Figure 1. Inflorescence and leaves of Scalesia baurií ssp. hopkinsü on Pinta Island.
to these plants and might act as pollinators. These
visits were timed and recorded. The maximum stay
listed for any one insect was 15 minutes. After this,
the insectwas eithercaptured, or anotherobservation
was begun so as not to spend an excessive amount of
time watching one individual.
Table 1 shows the results of the bagging studies'
Flower counts were not made, so an actual percent-
age of fruit set cannot be given. Eliasson (1974)
mentions that approximately 50 bisexual disc-flow-
ers are typically found in an inflorescence, although
as many as 100 or more may be present' Ray-flowers
are also present, but these are sterile. In any case,
both treatmentsproduced numerous fruits. The mean
number for bagged inflorescences was 45.2, while
thatforopen-pollinatedinflorescences was 38.2. The
reason for the latter having a lower fruit set is prob-
ably because of their exposue to predators before
being bagged. Finches wereoften seen attheseplants,
and one inflorescence was actually obsewed being
eaten. Ten of the bags were not recove¡ed after this
study. One explanation for this might be that they
were overlooked during the final collection. Howev-
er, anotherpossibility is thatthese bags weredesEoyed
by the Galápagos hawk (Buteo galapagoensis). This
hawk removed and tore apart pollination bags from
other plant species that were being studied during the
same period.
Theprimary insectvisitors to theseplants arenoted
in Table 2. A species of Mythenteles (Diptera: Bom-
byliidae) was most fiequently observed, with 5 1 visits
and a total of 28,49 4 seconds spent on infl orescences.
These bee flies wouldoftenvisitmore than one flow-
er per inflorescence, and appeared to be probing for
nectar. In fact, one was observed trying to force its
way down into a corolla tube. Pollen was clearly
visible on its wings andthorax during this visit. Second
in occurrence was Lepidanthrax tinctus Thomas
April 1994 NOTICIAS DE GALÁPAGOS 27
Table 1. Bagging experiment results, in number of fruits produced per inflorescence.
Bagged Inflorescences
Open-Pollinated
Inflorescences
MEAN
45.20
38.1 8
RANGE
0-76
o-67
Ð
18.06
16.78
N
99
91
Thble 2. Insect visitation times, in seconds, based on 24 hours of observation (6:00 A.M. - 6:00 p.M,
9 & tO July 1990).
TOTAL MEAN RANGE Ð
DIPTERA
Mythenteles sp.
(Bombyliidae)
Lepidanthrax tinctus
(Bombyliidae)
LEPIDOPTERA
Atteva hysginiella
(Yponomeutidae)
Pyralid Moth
(þralidae)
N
51
33
28,494
1,061
r,664
568
5s8.71
32.r5
208,00
189.33
30-900
2-r39
12-405
60-274
349.26
3r.63
155.68
1t3.78
(Diptera: Bombyliidae) with 33 visits, and a total
time of 1,061 seconds. A moth, Atteva hysginiella
Wallengen (Iæpidoptera Yponomeutidae), w as the third
most common insect with eight visits. However, its
total visitation time was 1,664 seconds. Thus, its
mean stay (208 seconds) was approximately 6.5 times
longer than that of L. tinctus. Both of these insects
appeared to probe for nectar just as the species of
Mythenteles. The least frequent visitor recorded dur-
ing the observation studies was apyralid moth (Lep-
idoptera: Pyralidae). This single individual visited
inflorescences three times, for a total of 568 seconds.
In addition, two untimed visits were made by a spe-
cies of Rhinacloa (Hemiptera: Miridae).
Most of the insects made their visits throughout
the day, although the pyralid morh did not appear
until after 4:00 P.M. Only Mythenr¿l¿s individuals
were observed spending more than 15 minutes on an
NOTICIAS DE GALAPAGOS No.5328
inflorescence during the timed studies.
Insufficient nectar was produced by the flowers
for micropipet collection. Howeve¡, the fact that all
of the insect visitors had mouthparts adapted for suck-
ing rather than chewing suggests that a small nectar
reward presumably is present.
These results indicate that S. baurii ssp. hopkinsü
is capable of autogamous reproduction, just as the
other members of this genus that have been studied.
In addition, even though the carpenter bee is absent
on Pinta, there afe other visitors that may promote
self- o¡ cross-pollination. Insects spending longer
periods of time on each inflorescence are probably
more important for selfing, since this behavior re-
sults in fewer visits to other plants. If this scena¡io is
correct, then t. t inc tus may be more important in the
cross-pollination of this plant than the other visitors
listed in Table2.
The breeding strategy of S. baurii ssp. hopkinsii
appears reasonable for a plant inhabiting an oceanic
island. Autogamy would promote initial establish-
ment, while visits by available insects might lead to
outcrossing. The flowers of this species a¡e well suited
to the small generalist insects found on Pinta Island'
Wind pollination, which demands profuse pollen
production, would be of little value, especially dur-
ing thecolonization period when only a few individuals
presumably would be present (McMullen and Close
1993).
ACKNOWLEDGMENTS
We wish to thank the following individuals for
their assistance: Daniel Evans, Aracelly Fajardo,
Fernando Hurtado, Gayle Davis-Merlen, Godfrey
Merlen, Cecilia Solis, Hugo Valdebenito, and Fion-
nuala Walsh. Appreciation is also extended to T.J.
Henry, R.W Hodges, and M. Lacey-Theisen of the
Systematic Entomology Laboratory United States
Department ofAgriculture, Beltsville, Maryland; S.B.
Peck and B.J. Sinclair of Carleton University, Otta-
wa, Canada; and N.L. Evenhuis of the Bemice P.
Bishop Museum, Honolulu, Hawaii for insect iden-
tif,rcations. As always,I would like to thank the staffs
of the CDRS and GNP for thei¡ gtacious assistance.
This work was supported by National Geographic
grant4327-90.
LITERATURE CITED
Eliasson, U. 1 974. Studies in Galápagos plants. XIV.
The genus Scalesia Arn. Opera Botanica 36:1-
rt7.
Linsley, E.G., C.M. Rick, and S.G. Stephens. 1966.
Observations on the floral relationships of the
Galápa gos c arpenter bee. Pan-Pacific Entomolo-
gist 42:1-18.
McMullen, C.K. 1985. Observations on insect vis-
itors to flowering plants of Isla Santa Cruz. I. The
endemic carpenter bee. Noticias de Galápagos
42:24-25.
McMullen, C.K. 1 987. Breeding systems of selected
Galápagos Islands angiosperms. American Jour-
nal of Botany 74:1694-L7O5.
McMullen, C.K. 1990. Reproductive biology of
Galápagos Islands angiosperms. Monographs in
Systematic Botany from the Missouri Botanical
Garden 32:35-45.
McMullen, C.K., andD.D. Close. 1993. Wind pol-
lination in the Galápagos Islands. Noticias de
Galápagos 52:12-17.
Rick, C.M. 1966. Some plant-animal relations on
the Galápagos Islands. Pp.215-224 in R.L Bow-
man (ed.)The Galápagos. Universityof California
Press, Berkeley.
Contey K. McMullen, Department of Biology and
Chemistr¡ West Liberty State College, West Lib'
erty, West Virginia, 26074, USA. Sandra J.
Naranjo, Escuela de Biologia, Universidad Cen-
tral del Ecuador, Quito, Ecuador.


Pollination of Scalesia baurii ssp. hopkinsii (Asteraceae)

on Pinta Island

http://aquaticcommons.org/6583/1/NG_53_1994_McMullen%26Naranjo_Pollination_of_Scalesia.pdf

Pollination of Scalesia baurii ssp. hopkinsii (Asteraceae) on Pinta Island

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