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Geranium pusillum L. (Geraniaceae): A Newly Naturalized Plant in Taiwan

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Chih-Hsiung Chen
Chih-Hsiung Chen
Chih-Hsiung Chen
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Chiu-Mei Wang
Chiu-Mei Wang
Chiu-Mei Wang
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Abstract and Figures

Geranium pusillum L., an annual or biennial herb mainly native to Europe, northern Africa, and western Asia, has recently become naturalized in mountain regions of central Taiwan at about 1,800-2,300 m in elevation. This species is very similar to G. molle, which was also recently found to have become naturalized in Taiwan; however, the former has smaller flowers and scabrous fruits. In the present work, we provide a taxonomic description, an illustration, photographs, and scanning electron micrographs to facilitate identification. Furthermore, a key to the taxa of the genus Geranium in Taiwan is also provided.
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Taiwania, 52
(3): 270-275, 2007
Geranium pusillum L. (Geraniaceae): A Newly Naturalized Plant
in Taiwan
Chih-Hsiung Chen
(1)
and Chiu-Mei Wang
(1,2)
(Manuscript received 14 November, 2006; accepted 10 May, 2007)
ABSTRACT: Geranium pusillum L., an annual or biennial herb mainly native to Europe, northern
Africa, and western Asia, has recently become naturalized in mountain regions of central Taiwan at
about 1,800-2,300 m in elevation. This species is very similar to G. molle, which was also recently found
to have become naturalized in Taiwan; however, the former has smaller flowers and scabrous fruits. In
the present work, we provide a taxonomic description, an illustration, photographs, and scanning
electron micrographs to facilitate identification. Furthermore, a key to the taxa of the genus Geranium in
Taiwan is also provided.
KEY WORDS: Geraniaceae, Geranium pusillum, naturalized plant, Taiwan, taxonomy.
INTRODUCTION
Geranium L. is a cosmopolitan genus, with about
420 species being recognized in three subgenera and
eighteen sections (Aedo et al., 1998a). Five native
and one naturalized species are recorded in the Flora
of Taiwan, 2nd edition (Huang, 1993; Peng, 1978),
and are mainly distributed in the central mountains.
Recently, G. molle was also found to have been
naturalized in the mountain regions in Taiwan (Chen
and Wang, 2005). In our botanical exploration of the
Central Mountain Range, we recognized G. pusillum
L., an unrecorded species of Geranium which was
collected. In preparation for the forthcoming Field
Guide to Geraniums of Taiwan, we have examined
specimens from HAST, TAI, TAIF, and TNM. The
earliest collection date was 10 May, 2001 by Y. Y.
Huang et al. 395 (HAST, TNM). Hence we
concluded that the species has only recently become
naturalized in montane regions of central Taiwan at
about 1,800-2,300 m in elevation.
Geranium pusillum belongs to the section
Batrachioidea of the subgenus Robertium (Yeo,
1984, 1990). This species is distributed in Europe,
northern Africa, and western Asia (Aedo, 1998b),
and was introduced to the Americas and East Asia
where it has become a weed (Aedo et al., 1998a).
MATERIALS AND METHODS
__________________________________________
1. Department of Botany, National Museum of Natural Science, 1,
Guancian Rd., Taichung 404, Taiwan.
2.
Corresponding author. Tel: 886-4-23226940 ext. 520; Fax:
886-4-23258684; Email: cmwang@mail.nmns.edu.tw
Materials used in the studies were collected from
the fields in Taiwan, and were pressed and dried as
voucher specimens in the herbarium of TNM. Fruits
and seeds for scanning electron microscopy (SEM)
were from fresh capsules and flowers of C. M. Wang
et al. 8308 (G. pusillum) and C. H. Chen et al. 7397
(G. molle). All materials used for SEM were coated
with gold and examined under Hitachi S300N.
SYSTEMATIC TREATMENT
Geranium pusillum L., Syst. nat. ed. 10, 2:1144.
1759 May-June (Burm. f., Spec. Bot. Geran. 27.
1759 Aug). 小花牻牛兒苗 Figs. 1 & 2
Annual or biennial herb, erect, 15-35 cm tall; stem
pilose, somewhat reddish with glandular hairs.
Leaves round or circular with deeply palmate lobes,
surface pubescent, 1.2-5.5 cm broad, petioles
2-10(12) cm long; stipules 4 at each node. Flowers 2,
axillary or subterminal, actinomorphic, 5-7 mm in
diameter; peduncles somewhat reddish, 0.5-1.2(1.5)
cm long, pilose; pedicels 0.6-1.4 cm long, pilose;
bracts 2, linear to linear-triangular, ca. 1.5 mm long;
sepals 5, pilose on outside, 2.5-3.5 mm long; petals 5,
bilobed, pink to magenta, 2.5-4 mm long. Stamens
10, 2-whorled, anthers ellipsoid, 0.5-0.8 mm long.
Ovary 4-8 mm long; styles 5, ca. 1 mm long.
Capsules light brown to brown, scabrous, 0.9-1.2 cm
long. Seeds light brown, oblong, 1.4-1.8 mm long,
glabrous.
Distribution: Native to Europe, northern Africa,
Western Asia, Soviet Middle Asia, and the Caucasus.
Introduced to the north-central Pacific, the Americas,
September, 2007 Chen & Wang: Geranium pusillum in Taiwan 271
Fig. 1. Geranium pusillum L. A: Habit. B: Stem. C: Bract. D: Flower. E: Petal. F: Stamen. G: Style. H: Ovary with calyx. I: Dehiscing fruit.
J: Capsule. K: Seed. (C. M. Wang 8244).
eastern Asia, and New Zealand (Aedo et al., 1998a).
This species is naturalized in Japan and has been
recorded as an alien species for decades (Nagata,
1972). In Taiwan, it occurs at about 1,800-2,300 m in
elevation in the Central Mountain Range, and is
usually found in open grasslands near roadsides or
vegetable farms.
Specimens examined:
Taichung Co., Hoping Township:
Huan Shan. elev. 1,850 m, May 10, 2001, Y. Y. Huang et al. 395
(HAST, TNM); Nantou Co., Jenai Township: Central-Cross-Island
Highway # 103.2 Km, elev. 2,250 m, Apr. 16, 2002, C. M. Wang
5473 (TNM), Jenai Township: Chiyanchung. elev., 2,250 m, Sep.
15, 2005, C. M. Wang 8244 (TNM); Oct. 12, 2005, C. M. Wang et
al., 8308 (TNM).
272 TAIWANIA Vol. 52, No. 3
Fig. 2. Geranium pusillum L. A: Habit. B: Branch and inflorescence. C: Leaf. D: Flower. E: Fruits. Scale bar A = 5 cm; bars B and C = 1 cm;
bars D and E = 5 mm.
Notes: This species was found in exposed area,
and is sometimes distributed near the similar species
G. molle in Taiwan. Both species are in the subgenus
Robertium, which is characterized by the
“carpel-projection” type fruit discharge (other
congeners in Taiwan also have fruit of the
“seed-ejection” type), and are also in the same
section Batrachioidea by the shallowly divided
leaves and blue pollens.
Geranium pusillum and G. molle are very similar
and easy misidentificatied if only the vegetative
body is examined. The former species differs from
the latter in having smaller flowers (5-7 vs. 8-10 mm
in diameter). From examination of scanning
electron-micrographs, the capsule surface of G.
pusillum is scabrous, but that of G. molle is rugose
(Figs. 3A, B, E & F). The seed shape of the former is
narrower than the latter (long-ovoid vs. subglobose),
September, 2007 Chen & Wang: Geranium pusillum in Taiwan 273
Fig. 3. Comparison of scanning electron micrographs between Geranium pusillum (left panels) and G. molle (right panels). A & E: Fruits. B &
F: Enlarged fruit-coat. C & G: Seed. D & H: Sculpturing of seed-coat. Scale bars A, E, C & G = 0.5 mm; bars B, F, D & H = 0.1 mm.
274 TAIWANIA Vol. 52, No. 3
and G. pusillum has a more-obvious ridge near the
hilum (Figs. 3C & G). Both of these species have
similar reticular sculpturing on seed-surface (Figs.
3D & H).
Key to the taxa of Taiwanese Geranium
1. Capsules with seed discharged from stalk when mature ............ 2
1. Seeds directly ejected from capsules when mature ................... 4
2. Leaves ternately divided ……………………… G. robertianum
2. Leaves simple, 5~7 divided ....................................................... 3
3. Capsule surface scabrous, flowers less than 7 mm in diameter ....
.…............................................................................. G. pusillum
3. Capsule surface rugose, flowers more than 8 mm in diameter .....
…......................................................………………… G. molle
4. Flower solitary; bracts 2 ............................................................ 5
4. Flowers 2; bracts 4 .................................................................... 6
5. Stipules 4 at each node; flowers yellow …..........……. G. suzukii
5. Stipules 2 at each node; flowers pink to purple …. G. hayatanum
6. Pedicels less than 1 cm long; flowers in a compact cluster ...........
.....................................................................….. G. carolinianum
6. Pedicels longer than 1 cm long; flowers in a loose cluster ......... 7
7. Stem hairy with glandular hairs; flowers purple ……..................
.…………..................................... G. nepalense ssp. thunbergii
7. Stem glabrous or tomentose on the upper portion; flowers white
.................................................................................. G. wilfordii
ACKNOWLEDGEMENTS
We thank Ms. H. H. Yang for the excellent line
drawing, and Mr. C. S. Chiu for the assistance with
SEM-photography. We also thank the curators of
herbaria of HAST, TAI, TAIF, and TNM for
facilitating specimen examination. This work was
supported by a grant (NSC94-2311-B-178-002) from
the National Science Council, ROC.
LITERATURE CITED
Aedo, C., F. M. Garmendia and F. Pando. 1998a.
World checklist of Geranium L. (Geraniaceae).
Ann. Jard. Bot. Madrid 56: 211-252.
Aedo, C., J. J. Aidasoro and C. Navarro. 1998b.
Taxonomic revision of Geranium sections
Batrachioidea and Divaricata (Geraniaceae).
Ann. Missouri Bot. Gard. 85: 594-630.
Chen, C.-H. and C.-M. Wang. 2005. Geranium molle
L. (Geraniaceae), a newly naturalized plant in
Taiwan. Coll. and Res. 18: 11-14.
Huang, T.-C. 1993. Geraniaceae. In: Huang, T.-C. et
al. (eds.), Flora of Taiwan 2nd ed. 3: 403-409.
Editorial Committee, Dept. Bot., NTU, Taipei,
Taiwan.
Nagata, T. 1972. Illustrated Japanese alien plants.
Hokuryu-Kan Tokyo, Japan. p. 110. (in Japanese)
Peng, C.-I. 1978. Some new records for the flora of
Taiwan. Bot. Bull. Acad. Sin. 19: 83-86.
Yeo, P.-F. 1984. Fruit-discharge-type in Geranium
(Geraniaceae): its use in classification and its
evolutionary implications. Bot. J. Linn. Soc. 89:
1-36.
Yeo, P.-F. 1990. The classification of Geraniaceae.
In: Vorster, P. (ed.), Proceeding of the
International Geraniaceae Symposium, Univ. of
Stellenbosch, Republic of South Africa. pp. 1-22.
September, 2007 Chen & Wang: Geranium pusillum in Taiwan 275
臺灣新歸化牻牛兒苗科植物－小花牻牛兒苗
陳志雄
(1)
、王秋美
(1,2)
(收稿日期：2006 年 11 月 14 日; 接受日期：2007 年 5 月 10 日)
摘 要
主要原產於歐洲、北非、西亞的牻牛兒苗科植物－小花牻牛兒苗（Geranium pusillum
L.），新歸化於台灣中部山區，為一年或二年生草本。小花牻牛兒苗與最近歸化於臺灣
山區的柔毛牻牛兒苗形態相似，但是花較小，且果實表面粗糙具短毛而可區分。本文提
供分類特徵描述，手繪圖，照片與檢索表以供區分鑑定。
關鍵詞：牻牛兒苗科、小花牻牛兒苗、歸化植物、臺灣、分類。
________________________________________________________________________________________________
1. 國立自然科學博物館植物學組，404 台中市館前路 1 號，臺灣。
2. 通信作者。Tel: 886-4-23226940 ext. 520; Email: cmwang@mail.nmns.edu.tw
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  • Jan 1998
  • C Aedo
  • F M Garmendia
  • F Pando
Aedo, C., F. M. Garmendia and F. Pando. 1998a. World checklist of Geranium L. (Geraniaceae).
Taxonomic revision of Geranium sections Batrachioidea and Divaricata (Geraniaceae)
  • Jan 1998
  • C Aedo
  • J J Aidasoro
  • C Navarro
Aedo, C., J. J. Aidasoro and C. Navarro. 1998b. Taxonomic revision of Geranium sections Batrachioidea and Divaricata (Geraniaceae).
Some new records for the flora of Taiwan
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  • 83-86
  • C.-I Peng
Peng, C.-I. 1978. Some new records for the flora of Taiwan. Bot. Bull. Acad. Sin. 19: 83-86.
The classification of Geraniaceae
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  • P.-F Yeo
Yeo, P.-F. 1990. The classification of Geraniaceae. In: Vorster, P. (ed.), Proceeding of the International Geraniaceae Symposium, Univ. of Stellenbosch, Republic of South Africa. pp. 1-22.