PALMS Meyer et al.: Invasive Palms Vol. 52(2) 2008

JEAN-YVES MEYER Délégation à la Recherche Time Bombs in B.P. 20981 Papeete, Tahiti Gardens: Invasive French jean- Ornamental [email protected]

Palms in Tropical CHRISTOPHE LAVERGNE Association Palmeraie- Islands, with Union Domaine de Palmahoutoff Emphasis on 97432 Ravine des Cabris La Réunion French Polynesia

(Pacific Ocean) AND and the DONALD R. HODEL University of California Mascarenes P.O. Box 22255 , California () 90022 USA

Although palms are much beloved handsome and striking components of tropical and subtropical gardens and landscapes, some , like many other ornamental , are invasive and can pose a threat to native ecosystems if they escape cultivation.

Invasive alien species are recognized to be one Pamplemousses in the island of in of the major causes of biodiversity loss. Because 1729 or the Cinchona Botanical Garden in of their long-term evolution in complete in 1868, have constituted major entry isolation, island biota are particularly points for a large number of non-native plants, vulnerable to foreign biological invasions. some of which became invasive (for example Humans have intentionally introduced a the Litsea glutinosa and the vine Hiptage majority of invaders as garden benghalensis in Mauritius or the tree Pittosporum ornamentals. Public or private botanic gardens, undulatum in Jamaica). Gardens still represent some of them established for many centuries continual sources of potential (or incipient) in the tropics, for example the Jardin des invasive plants.

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Some plant families are recognized as being literature survey and personal communi- “weedy” because they contain a high number cations of botanists, gardeners and palm of invasive species. Invasive legume collectors. We focused on French Polynesia, (Fabaceae), such as Leucaena leucocephala, especially the island of Tahiti (Society Islands), Acacia spp. or Prosopis spp., were widely and the Mascarenes, especially La Réunion and planted for forestry and/or soil improvement Mauritius islands. Potential (or incipient) in the past, and weedy grasses (Poaceae), such invasive palm species that might present a risk as Melinis minutiflora, were intentionally of becoming invasive in the near future are introduced as fodder or are accidentally also noted. introduced as contaminants. With the increase Major documented invasive palms of the trade and the recent development of the landscape industry (the Twelve palm species are recognized as invasive “green industry”), new “invasive families” are in tropical regions and islands (Tab. 1), emerging. For instance, several Acanthaceae meaning they are well established in the wild species, which are popular garden plants away from the original introduction sites, form because of their showy and colorful dense clumps or stands excluding the native and , are now being reported as invasive vegetation and spread in primary (or native) in Indo-Pacific tropical islands (Meyer and or in secondary (or disturbed) forests. Lavergne 2004). The palm family () The African oil palm (Elaeis guineensis) is has been regarded as under-represented in spreading on Pohnpei (Federate States of terms of the relative number of invasive Micronesia) particularly on drier sites (Space & species. Indeed, there are only a few species (ca. Falanruw 1999). 12) which are reported to be widely naturalized The Chinese fan palm or fountain palm or invasive in tropical islands or countries (Tab. ( chinensis) is considered invasive in 1). Bermuda (Kairo et al. 2003) and in Mauritius The objective of this paper is to inform private and La Réunion Islands (Moore & Guého 1984, and public botanical gardens, palm collectors Strahm 1993, 1999). It is naturalized in and hobbyists, horticulturists, gardeners and (www.fleppc.org/list/05List.htm), in landscapers of the risk of invasion posed by (Wagner et al. 1990, 1999) where it spreads in some introduced ornamental palms. Svenning ditches, stream beds, wet gulches and shady (2002), who focused only on naturalized palms understory of disturbed secondary forests (Starr in a secondary tropical forest in Panama, raised et al. 2003a) and on the east coast of New the issue that popular palms have the potential Caledonia in riparian forest (MacKey 1985). to become problematic invasive species and The California fan palm ( filifera) recommended that a world-wide list of is considered invasive in Hawaii (Starr et al. invasive, non-native species be compiled. 2003b) and in the Perth area (Hussey Herein, we listed the main naturalized and et al. 2007, Richardson et al. 2006), while the invasive species in tropical or subtropical Mexican fan palm (W. robusta) is cited as countries and islands based on our personal invasive in Hawaii (Starr et al. 2003b) and knowledge and field-observations, extensive Florida (www.fleppc.org/list/05List. htm).

1. Increase of the number of palm species introduced to Mauritius (Mascarenes, Indian Ocean) and Tahiti (French Polynesia, Pacific Ocean) during the last two centuries (after Baas Becking 1950, Jacquier 1960 and Nadeaud plant database, version 1992, for Tahiti, Rouillard & Guého 1981-1985, 1999 for Mauritius).

72 PALMS Meyer et al.: Invasive Palms Vol. 52(2) 2008 f f d d / s p p . . e i p p m c t m p p e t s s h 3 p . l _ _ h s . a a a , H / t i i a m m 7 b b e s r a t C t , n n s 0 I 3 3 e u 3 7 h h f o o a 0 L / . 0 0 . b 0 i t t 9 m s s b l 2 = a 0 0 i 0 o g g i 9 l a h a / s r f . p 2 2 2 t n n l 1 l o a i h _ _ i i n . . a r . a . b c l l n a a l t e m l i m h h i i d 7 / a a t t f S a t e m s s / a m 0 / n n p e t t t a a , h g h t n t y 0 . d o o i r / e e h 5 e s y e t t m . w w a 2 s a u o 9 ? t 8 / / r r e t e g g r . s . o n r g r r s s e s 9 t r r 9 l l g l e n n t t f a s _ a a o a 9 i o i i s a 1 i r r n t t c s d t f u s p 1 i p i h h o o S S t i S n o y e r w m . e s s e H e / p p r , , , r , e r a a a a a o 5 w w , e e g l / 2 2 p 3 z 3 K y 0 r r h r d u s / m e 5 w w 0 0 a 0 w 0 c / e r t / g / 0 / / o a h h 0 r s 0 0 L . a 0 s 0 s s s n n 2 w v n s o o t 0 b 2 2 e , 2 e e i 2 n 9 a a . a r , i i i u p p M 2 l l g j 7 . t t o . n 9 g / / c o c c 9 / l a i l , t t m p r f f 9 H n g e 9 e e t n i t p a 9 v F a i e e 4 o d d 9 , l l l a 1 p e p p n u . 9 h h o t 8 t t r r i s r 1 p p s s . 7 s v / c , l 1 g & e e a / / a a / / / / 9 s r r . 9 t _ r u 0 i r r r r r r r e 1 B B r a e a s 9 e x o e e o e e e e 9 W w a s l i i i i i i i r c r o d 1 t l n 3 9 o i , i u n W s a & & P s p P P P p n e h . r 0 u a 1 a 2 2 2 h / / / / / / / o l e , u p r r o F n 0 . n é . K 0 0 0 g g g g g g g c K a S o i 5 t e e l . s r r r r r r r , 2 a u 0 0 0 , , t n , s 8 t l a u h h o o o o o o o 9 . 2 2 2 7 t m m a 9 e e ...... a 5 c 9 n G l p t i i i r r r r r r r 7 i c 9 9 F _ a t 9 a 1 e s e e i g g g r o a a a a a a a l 9 s 9 a 9 r t t 9 e & t e e e e e e e s h h r n n n e f 1 p 1 & n 1 i i i n 1 n e d n e e / e h i a h h h h h h e n n i ...... , / o r c n n n o r h e u s r e e n : K t o r t e 3 c e w w w w w w w w w o a n n n h g r s o c i l p p p i i u 9 l a z e e e c t a c o a n p p w w w w w w w w w r a t v a 9 o u v v v p m o i S w l W K M J A h F w O w L w 1 S S S S w O S M w w w w d n a s d n a s l s o a a i w , d e d ) l m a . , a u a a N s b i ) I c a . l , , r n , n i i m ) ) ) s i a a a . . . a c r ) I i r n p i . i s s s B P e a t a f d I I I s o i c n o d s i I , , B l i a r w d ) ) ) ) c o f c c c n u a t . , . . . d i i i i i a c I e a r ) ) i s s s s f f f i l A ( c g t i i i I I I I f P H n a n A A a s i , e ( c c c i i ) n S S , c c P u r n n n a a a C . R i ) a ( s a o s . f a a a T i P P P U U A i i I s i ( ( ( ( ( P e e e d w , I n , c a a ( m n e i i i c b b b e e a l a a a a o i i i i u i p n b b b l l a m m f d r P d d d a a a N d é i i i i i i m n i i i a ( a a a e p r r r e z z , c r r r a R w w w e l h i i g a a a n n v a a a j o j o o c a a a u i a d r r o a a a l i i l l n C C C P e I C O F ( B H H G ( ( L P N P F F F H P F B ( z i l a r ) u a i t , l a a a n r n n o t a s o y i m l l z u , i , . a e & o r A n s a a l r , ( d i i I t a a A a o i s t s d d c s a e S s , w . u i A u e , w n c i n s a a r n , y i I i I i a f a a A n E r a a r E l k i , i i f k T u n A s S l l o u u o o r a e p n , n A n i l a a , n G r y c c y o p i h e a s r r i i n a e a t d f e i k t t t R i g i l L v t s a x x e A r b s s w d l i i u i s , d e e e i i p r u e o . u a s u u y h a E r s n a a O I A R A S Q E I W P J S N N C C M M M v n i d e a t n n a i e m m e a a u i h r c i g d r o n n u i d a h n a t x r t a r n e r s o l a u e j s a u c c a f i a r a i b s e a t l e s x x o i f a n i i i r f i m l m a e s m l s n n i e a n a y n a a e e e n g a r i t i i e e e o o n a c d h e h r n n m h c h h c a t n r i o o n T c p p i t t t a e d i a a . a o o i e g g f u u p p t t r i r 1 x n s g n n n s t i f t n n i i o o o o s e n t o o t r h h n a i h a l s e s s s e c h h e e c i p t o b y i e c c a a y a v y e r r r o a l i t h c S T A A A E H L N P P R W W

73 PALMS Meyer et al.: Invasive Palms Vol. 52(2) 2008

2. Seedlings of grandis in the understory of lowland rainforest on the island of Tahaa, French Polynesia (photo: Jean-Yves Meyer).

The Sagisi palm (Heterospathe elata), which was including submontane rain forest in Rio introduced to Guam between 1900 and 1920, Grande (www.institutohorus.org.br/download/ is spreading in ravines and slopes (Jones 1995, fichas/Archontophoenix_cunninghamiana.ht Space & Falanruw 1999). m). The MacArthur palm ( The Cuban royal palm ( regia) occurs macarthurii) and the ( in high abundance in secondary forests of dactylifera) are widely naturalized in (Smith Panama, where it is well naturalized in swamp 1979, Watling 2005), the first species along or lakeside forests, and trianda sometimes drainages, fence lines and vacant lots in urban completely dominates the understory of areas and the second forming large secondary forests there (Svenning 2002). populations of about 1000 adult trees in the The nipa or palm (Nypa fruticans) in Nadi area and surrounding cane fields (Fuller Nigeria, which was introduced from 1997). The MacArthur palm is also naturalized in 1906, is currently displacing the native in Panama (Svenning 2002), Singapore (Hsuan mangrove vegetation and impacting coastal Keng et al. 1998) and the islands of plant communities (www.africanconservation. and in the Lesser org/ncftemp/nipa.html). This species is also Antilles (Delnatte 2003,) and is considered reported as naturalized in the island of invasive in (Kairo et al. 2003). The Trinidad (Kairo et al. 2003) and Panama. date palm, planted around settlements throughout the arid zone of , Naturalized and Invasive Alien Palms in forms dense thickets by suckering and French Polynesia (Pacific Ocean) spread by birds, affects water flow and displaces Beside the coconut (Cocos nucifera), which is the native Livistona alfredii (Hussey et al. 2007). considered native or a Polynesian intro- The Alexander palm (Archontophoenix duction, only three native palms have been alexandrae) is naturalized in Hawaii in low- recorded from the remote oceanic islands of elevation mesic valleys (Wagner et al. 1990, French Polynesia: vuylstekeana and 1999, Lorence, pers. comm. 2007), while the P. pericularum, both reportedly from the bangalow palm (A. cunninghamiana) is Tuamotu Archipelago, and Pelagodoxa henryana naturalized in several regions of in the Taipivai Valley on Nuku Hiva in the

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Marquesas Islands. Recently, Hodel visited Twelve species of palms are sparingly or widely Makatea in the Tuamotus and was able to naturalized in French Polynesia (Table 2). verify that the indigenous palm there was P. Meyer (1998) reported that the ruffled fan mitiaroana, which heretofore was thought to be palm or Vanuatu fan palm (Licuala grandis, endemic to Mitiaro in the Cook Islands. The locally called “palmier-cuillère” in Tahiti, origin of Pelagodoxa henryana is still somewhat which means “spoon palm” because of its large controversial because all its known locations ), was established in wet, low-elevation in the Marquesas and in Melanesia (Vanuatu secondary forest in a valley on the island of and the ) are at sites currently Tahaa (Society Islands) (Fig. 2). In its native or known to have been inhabited in the past. range of Vanuatu (San Cristobal and Santa Cruz), L. grandis is known to be gregarious in About 108 species of non-native (or alien) shaded understory of rain forest and forms palms were introduced to French Polynesia extensive colonies (Jones 1995, Whitmore during the past century (Table 1). Nine species 1975). Introduced to Tahiti in 1930, it was were planted in Tahiti from 1840 to 1890, cultivated since 1936 in the JBHS, where it is including five by E. Raoul in the town of currently locally naturalized. Papeete in a botanical garden called Jardin Raoul, which is now the Mamao Hospital. Guérin observed the Lucuba palm (Dypsis Harrison W. Smith introduced about 30 species madagascariensis) naturalized in wet, low- in the 1920s to 1940s to his garden in Papeari, elevation secondary forests of the Opunohu now the Jardin Botanique Harrison Smith Valley, Moorea (Society Islands) in the 1980s (JBHS). Recently, more than 70 species have from a 1971 introduction. More recently Meyer been introduced from 1970 to 1990 by Michel observed this species naturalized in the Guérin, former director of the JBHS, and Vaianae and Maharepa valleys of Moorea up hobbyists, collectors and those in the to 400 m elevation in secondary and wet landscape industry. See Hodel (1982, 1993) for primary forests (Fig. 3). It is noteworthy that accounts of cultivated palms in Tahiti. this species (under the name Chrysalidocarpus lucubensis) is also noted to be locally naturalized in low-elevation rain forest in 3. Dypsis madagascariensis naturalized in mid- Mauritius (Lorence & Sussman 1986) and in elevation rainforest on the island of Moorea, French peripheral area of a secondary tropical forest Polynesia (photo: Jean-Yves Meyer). in Panama (Svenning 2002). Guérin also noted that the African Oil palm (Elaeis guineensis) was naturalized in the low elevation Fautaua Valley in Tahiti as early as the 1970s. In 2005 Meyer observed it locally naturalized in a wet secondary forest that was once a cultivated area in a deep valley on the island of Raiatea (Society Islands). The small fleshy (ca. 1 cm in diameter) of Dypsis madagascariensis and Licuala grandis might be dispersed over long distances by frugivorous birds, such as the common myna (Acridotheres tristis), introduced in the early 1900s in Tahiti and found at lower elevations, and the red-vented bulbul (Pycnonotus cafer), introduced in the 1970s and found at higher elevation (up to 2000 m), but also by the endemic dove Ptilinopus purpuratus, which is a generalist frugivorous wild pigeon found in mid-elevation rain forests in the Society Islands. Meyer observed red-vented bulbuls feeding on mature fruits of L. grandis in the main town of Papeete. The larger fruits of Elaeis guineensis might be dispersed by alien rats or wild pigs, which are common in deep and wet valleys of Tahiti and Raiatea.

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Table 2. Naturalized and invasive palms in French Polynesia (FP) and the (MS) (*known as naturalized or invasive in other tropical countries). Approximate date of introduction: T = in Tahiti; M = in Mauritius; R = in La Réunion. Scientific name Origin Date of introduction Status (island, archipelago) Areca catechu Southeast , 1754 (M) Locally naturalized (Tahiti, FP) 1825 (R) 1930? (T) Dypsis lutescens Madagascar 1837 (M) Locally naturalized (La 1856 (R) Réunion, MS) *Dypsis madagascariensis Madagascar 1768 (M) Widely naturalized/invasive 1856 (R) (Moorea, FP); naturalized 1937 (T) (Mauritius, MS) *Elaeis guineensis West 1780 (M) Locally naturalized (Raiatea, 1850 (T) Tahiti, FP) 1825 (R) *Heterospathe elata Philippines 1930? (T) Locally naturalized (Tahiti, FP) Licuala grandis Vanuatu 1936 (T) Locally naturalized (Tahiti, FP), widely naturalized (Tahaa, FP) *Livistona chinensis Japan, Taiwan, 1785 (M) Widely naturalized/invasive Ryukyu Is. (Mauritius, MS), locally naturalized (La Réunion, MS) Livistona australis Australia 1933 (T) Locally naturalized (Tahiti, FP) Livistona saribus . 1930 (T) Locally naturalized (Tahiti, FP) *Nypa fruticans Southeast Asia, , 1825 (R) Locally naturalized (Tahiti, FP) Sri Lanka, Australia, 1928 (T) Solomon Is. Ryukyu Is. tigillarium Sumatra, Borneo, 1930 (T) Locally naturalized (Tahiti, FP) Java, *Phoenix dactylifera North Africa & 1763 (M) Locally naturalized (Mauritius, Middle East 1825 (R) La Réunion, MS) Pakistan to Himalaya, before 1764 (M) Locally naturalized (Mauritius, E. India to Myanmar MS) Pinanga coronata 1980 (T) Locally naturalized (Tahiti, FP) 1836 (M) Locally naturalized (Tahiti, FP) 1896 (R) 1937 (T) * New Guinea, 1905 (M) Locally naturalized (Tahiti, FP) Australia 1931 (T) Raphia farinifera Trop. Africa before 1801 (M) Locally naturalized (Mauritius, before 1895 (R) La Réunion, MS) , 1825 (R) Locally naturalized (Mauritius, Trinidad, , 1837 (M) La Réunion, MS) Columbia Syagrus romanzoffiana Brazil to NE 1860 (M) Locally naturalized (Mauritius, Argentina MS) * 1904 (M) Locally naturalized (La Réunion, MS)

At least nine other palm species are locally solitaire palm (Ptychosperma elegans), native to naturalized in the JBHS. These include the Queensland, Australia, which is also known Indo-Malaysian nut (Areca catechu); the to be naturalized in the Islands

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4. Heterospathe elata naturalized in the shaded understory of a Tahitian chestnut Inocarpus fagifer secondary forest in the Jardin Botanique Harrison Smith in the island of Tahiti, French Polynesia (photo: Jean-Yves Meyer).

(Delnatte 2003, Kairo et al. 2003); the wet habitats in Fiji (Hodel, personal MacArthur palm (P. macarthurii), native to observation), especially in ColoiSuva where it Queensland and New Guinea and also locally was introduced in a garden in the 1970s and naturalized on the island of Kauai in the is now spreading aggressively through the Hawaiian Islands (D. Lorence, pers. comm. ColoiSuva Forest Park (Watling 2005). Dense 2007); Heterospathe elata, from the western stands of this palm species are observed in the Pacific, with many seedlings and young plants Lyon Arboretum in Hawaii (R. Baker, pers. growing in the shaded understory of a Tahitian comm. 2007). Seedlings of P. coronata were chestnut (Inocarpus fagifer) secondary wet forest recently observed in secondary wet forest at (Fig. 4); the Taraw palm (Livistona saribus), 450 m elevation in a gulch located under a native to Southeast-Asia, which is also well- residential area of the north coast of Tahiti. established in Panama (Svenning 2006); and The JBHS is also the source of some of the most the Australian palm (L. australis) and notorious and aggressive invasive plants in Oncosperma tigillarium (Hodel 1982). French Polynesia. Introduced in 1937, the Whether these palms will spread into the tropical American tree Miconia calvescens now surrounding vegetation or stay confined in the covers more than 80,000 ha of secondary and JBHS is not known, but there is often a time native wet forest, including endemic species- lag between the date of introduction and the rich cloud forest (Meyer & Florence 1996). The naturalization event, and between naturali- invasive trumpet tree (Cecropia peltata), the zation and invasion in secondary or native African tulip tree (Spathodea campanulata), and forests. Nypa fruticans, introduced in JBHS in the shoebutton ardisia (Ardisia elliptica) were 1928, is locally naturalized in the garden but all first introduced to the JBHS in the 1920s will not expand its distribution as suitable and 1930s. Other species have recently shown esturine habitat is scarce or lacking in French first signs of invasion, including the liana Polynesia. Anodendron paniculatum, which was introduced in 1934 (Meyer in press). Another species, Pinanga coronata, from Indonesia and introduced around 1980, may Alien Naturalized and Invasive Palms in the pose a threat because seedlings and saplings Mascarenes (Indian Ocean) have been observed in the JBHS and in nearby Thirteen native palm species are recognized in private gardens. It has naturalized in similar the Mascarene Islands (Moore & Guého 1984).

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A new endemic species, including an invasive species, the Chinese fan rousselii, was recently been described in La palm Livistona chinensis. On Mauritius it is Réunion, and A. crinita was recognized to be a widely naturalized in the secondary and the native species in the Mascarenes (Ludwig native forests (Rouillard & Guého 1981-1985, 2006). The origin of A. rubra is still 1999; Strahm 1993, 1999) and in the southeast controversial because all its known locations part of La Réunion it has spread in streambeds, in La Réunion are at or near places of past or shady understory of disturbed secondary current human habitation or other activity, forests, and in coastal areas (Fig. 5). Local land although in Mauritius wild populations are managers often mistake it for the endemic still found in the southern part of the island. palms Latania spp. This species may have been introduced from The Lucuba palm, Dypsis madagascariensis, Mauritius to La Réunion in the past for its which is a very old introduction in Mauritius much esteemed edible apical meristem, locally (1768), is naturalized in mid-elevation wet called “choux palmiste.” forests of Bel Ombre (J.-C. Sevathian, pers. Five Hyophorbe species have been described in comm. 2006). Seedlings and saplings of the the Mascarenes: one endemic to La Réunion golden cane palm D. lutescens, a very popular (H. indica), one to Rodrigues (H. verchaffeltii) palm used for hedges in the gardens of and three from Mauritius (H. lagenicaulis, H. Mauritius and La Réunion, have been observed vaughanii and H. amaricaulis). The in a streambed near Saint-Leu (J. Hivert and C. Latania is endemic to the Mascarenes, and each Fontaine, pers. comm. 2006). Frugivorous birds island has its own endemic species: L. or water have probably dispersed the fruits lontaroides in La Réunion, L. loddigesii in from a garden down to the valley bottom. Mauritius and L. verchaffeltii in Rodrigues. The cabbage palm or West Indian royal palm, Tectiphiala ferox is endemic on Mauritius and Roystonea oleracea, often planted in rows as is represented by fewer than 25 individuals in avenue trees, is naturalized in La Réunion the wild (Lavergne et al. 2007). Dictyosperma around the Saint-Paul pond and on a cliff near album is still common and currently cultivated a waterfall. This large palm is also reported to on the three islands. be naturalized in the Province Sud of New Among the 274 species of palms introduced to Caledonia (MacKey 1985) where it forms small the Mascarenes during the last three centuries, populations, especially in the valley of only 93 are still growing in the archipelago Moindou near a river (R. Amice, pers. comm. (Moore & Guého 1984, Rouillard & Guého 2007). It is naturalized in , Surinam 1981–1985, 1999). Palm introductions to the and (Zona 1996) where an Jardin des Pamplemousses in Mauritius important population is found near the village included 16 species by Fusée Aublet, of Kaw (C. Delnatte, pers. comm. 2007). Charpentier de Cossigny, Juge, Abbé Rochon Members of “Palmeraie-Union,” a local palm and Céré & Le Brasseur from 1754 to 1785; amateur group, reported that a population 50 160 species by, Falquhar, Thompson, Duncan, individuals of Raphia farinifera, native to Bojer and Cantley; 160 species from 1815 to tropical Africa and north and east Madagascar, 1892; 39 species by Koënig, Wiehé, Regnard, is established in La Réunion along the Rivière Rouillard, Val Ory and the forestry service from Saint-Louis (Martz & Martz 2001). The botanist 1904 to 1964; and 22 species from other E. Jacob de Cordemoy (1895) also observed sources in the 1970s–80s (Rouillard & Guého this species naturalized along the streams of 1999). Only 72 species are still growing in this Bras-Panon in La Réunion in the 19th century. botanical garden. However some Raphia populations have The gardeners N. Bréon and Jean-Marie regressed because of increasing urbanization. Richard planted about 45 species in the Jardin It is also naturalized along many streams and d’Acclimatation of La Réunion from 1825 to riverbanks in Mauritius, particularly around 1856. About 35 non-native palm species are Mare aux Vacoas and Moka plain (Rouillard & still growing in this botanical garden, now Guého 1981–1985, 1999), and is considered a called Jardin de l’État, located in the main potential invasive palm in the Seychelles town of Saint-Denis. (Dunlop et al. 2005). According to Moore and Guého (1984), about The date palm, Phoenix dactylifera, is widely 15 palm species are widely cultivated as planted along roadsides on the leeward coasts ornamentals in La Réunion and Mauritius. of Mauritius and La Réunion. It is naturalized Nine of them are naturalized (Table 2), in the driest region, particularly around Port

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Louis in Mauritius and on the leeward coast of La Réunion (Cordemoy 1895). It can be encountered near Saint-Leu along the Ravine des Poux in a remnant native dry forest (Lavergne, personal observation). The wild date palm, P. sylvestris from southern and eastern Asia is locally naturalized in Mauritius near Port Louis (Rouillard & Guého 1981–1985, 1999). The queen palm, Syagrus romanzoffiana, is reported to be sub-spontaneous at the base of Montagne Ory in Mauritius (Rouillard & Guého 1981-1985, 1999). The Mexican fan palm, Washingtonia robusta, is locally naturalized in Saint-Gilles, La Réunion on a roadside near a plant nursery. According to A. Hoarau (pers. comm. 2005), a palm collector in La Réunion, this species could become a serious plant invader as it produces small fruits easily dispersed by the Indian myna, Acridotheres tristis, or the red-whiskered bulbul, Pycnonotus jocosus, two widespread non-native birds in the Mascarenes. Discussion Only a few introduced palm species are naturalized in French Polynesia (12 out of 108 , ca. 12%) and in La Réunion Island (9 out of 93 species, ca. 10 %). It is also 5. Livistona chinensis naturalized in coastal secondary the case in Fiji (Pacific Ocean), which has more forest of Saint-Philippe, La Réunion, Mascarenes than 100 palm species in cultivation but only (photo: Christophe Lavergne). four documented naturalized species (Fuller 1997, Watling 2005), and Hawaii with more especially mynas (Acridotheres tristis in many than 650 species of palms cultivated in tropical islands, and A. fuscus in Fiji) the botanical gardens including four well- bulbuls (Pycnonotus cafer and P. jocosus), over documented invasive species (Staples & Herbst long distances. 2005). Indeed, several species have recently escaped However, we predict that more and more from cultivation to become naturalized in species will become naturalized and invasive Hawaii, including the cascade or cataract palm in French Polynesia and the Mascarenes in the (Chamaedora cataractarum) (Staples & Herbst near future, and more generally in tropical 2005), the West Indian royal palm (Roystonea islands worldwide as they are becoming very oleracea) and the wild date palm (Phoenix popular landscape and garden plants. The sylvestris), which has formed locally extensive number of introduced species in these islands stands in mesic habitats in Hawaii (Hodel, has dramatically increased in the last decades personal observation). (Fig. 1). Also, an increase in the number of individuals per species, in the number of The Auckland Regional Council of New localities where they are planted (which Zealand has recently planned to add three together constitute the “propagule pressure” palm species in its list of 119 banned invasive concept) and potential suitable habitat for plants: the bangalow palm (Archontophoenix their establishment and naturalization cunninghamiana), the Chinese windmill palm enhance the risk of invasion. Moreover, several (Trachycarpus fortunei) and the Canary Island palm species with small fruits (Ptychosperma date palm (), because they macarthurii in Fiji [Watling 2005], Licuala are spreading in the wild (www.arc.govt. grandis and Dypsis madagascariensis in Tahiti, nz/arc/). The two last species are also Washingtonia robusta in La Réunion) are naturalized in disturbed areas in the region of actively dispersed by alien frugivorous birds, Victoria, Australia (Groves & Hosking 1997,

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Lazarides et al. 1997). The Canary Island date potentially invasive species. WRAs are mainly palm, which is widely planted as an based on climate matches and life history traits ornamental and a street tree, has started to of species, and their “behavior” or invasive spread along waterways across south-east history elsewhere in the world (i.e. “black listed Australia (Richardson et al. 2006). species”), but published information on many plants species in specific regions or countries The Senegal date palm (), the are often lacking or not easily available, often queen palm (Syagrus romanzoffiana), the being only found in “gray literature.” solitaire palm (Ptychosperma elegans) and the bamboo palm (Chamaedorea seifrizii) are For example, the WRA for Hawaii and Pacific reported to be naturalized in Florida Islands (www.botany.hawaii.edu/faculty/ (www.fleppc.org/list/05List.htm). The Senegal daehler/WRA/, version January 2007) evaluates date palm, native to tropical Africa, is reported only a relatively few number of palm species to be naturalized in Bermuda (Kairo et al. (64, but some of these are synonyms) 2003). Doubts persist on the origin of Phoenix including 10 cited in our study. Three of them reclinata in the Comoros archipelago. It could (Ptychosperma macarthurii, Washingtonia filifera be native, but it is more frequent around and W. robusta) are considered invasive, villages and cultivated areas (Pascal 2000) and “causing significant ecological or economic in coastal forests. However, the fruits are harm in Hawaii.” dispersed by the native lemurs, and the palm Three other species (Archontophoenix alexandrae populations are increasing in the inland forest [syn. Ptychosperma alexandrae], Ptychosperma in the last ten years (N. Ludwig, pers. comm. elegans [syn. Seaforthia elegans] and Livistona 2006). The queen palm, native to Brazil and chinensis), which are considered invasive in Argentina, is also naturalized in the New South our study, need further evaluation according Wales and southern Queensland region of to the WRA “because of important missing Australia, the latter in urban shrubland in the data or because the species possesses a suburbs of Brisbane (Csurhes & Edwards 1998). combination of traits that makes its behavior Hyphaene thebaica, native from west tropical difficult to assess.” Africa to Egypt and the Arabian peninsula, is Four other species (Archontophoenix reported as a potential invasive palm in cunninghamiana, Dypsis lutescens, Roystonea Curaçao in the (Delnatte 2003). regia and Syagrus romanzoffiana) are considered The rattan, Calamus caesius, a climbing, vine- “not currently recognized as invasive in Hawaii like, spiny species native to Southeast Asia, is and not likely to have major ecological or reported to have started to naturalize on the economical impact on other Pacific Islands” by island of Upolu, Western Samoa in the South this WRA system. However, two of these are Pacific where it was intentionally introduced reported and known as invasive (D. lutescens in the early 1990s (Mark J. Bonin, pers. comm. and R. regia), and the other two are already 2007). The clustered fishtail palm Caryota mitis naturalized in tropical regions or islands (A. and the African oil palm Elaeis guineensis are cunninghamiana and S. romanzoffiana). naturalized and considered moderately invasive on the island of Mayotte in the We strongly recommend avoiding the Comoros archipelago, Indian Ocean (F. introduction and planting of the 12 well- Barthelat, pers. comm. 2006). documented invasive species (Table 1) and the two widely naturalized species in French Other naturalizing palms in botanical gardens Polynesia and the Mascarene Islands (Table 2) include the palm Arenga pinnata and that are able to form dense stands excluding Aiphanes horrida in the Amani Botanic Garden the native vegetation, as well as the other located in the East Usambara Mountains of locally naturalized species in tropical islands or Tanzania, first established in 1902 (W. Dawson, regions, which constitute real “time bombs” pers. comm. 2007). that can escaped from cultivation and gardens Management of invasive species begins with and invade native habitats (dry and mesic prevention, early detection and rapid response forests, rain forests, riparian forests) in the near (e.g. eradication) because control of large future. By forming very dense stands or infestations is often very expensive and clumps, palm species have the potential to difficult. “Black lists” of noxious (or harmful) displace native plant communities and change species and Weed Risk Assessment (WRA) the functioning of natural ecosystems (light systems are now commonly used in Australia or water regime, soil nutrients). Remote and New Zealand to prevent introduction of oceanic islands with a disharmonic flora might

80 PALMS Meyer et al.: Invasive Palms Vol. 52(2) 2008 be more vulnerable to invasion by palms as Dawson (University of Aberdeen, UK), Michel this functional group is scarce (only one genus Guérin (former director of the Jardin in Hawaii, Pitchardia, and two in French Botanique Harrison Smith in Papeari, Tahiti, Polynesia Pritchardia and Pelagodoxa) whereas French Polynesia), Jean Hivert & Christian dwarf, understory, climbing and clonal palms Fontaine (Conservatoire Botanique National are common in continental rainforests de Mascarin, Saint-Leu, La Réunion), Alain (Denslow 2003). Hoarau (Palmito Palm Nursery, La Réunion), David H. Lorence (National Tropical Botanical In 1990, Hodel, alarmed by John Dransfield’s Garden, Lawai, Hawaii, USA), Ray Baker (Lyon observation that the Wanga palm, Pigafetta Arboretum, Honolulu, Hawaii, USA), Nicole elata (as P. filaris) was a colonizer of disturbed Ludwig (Palmeraie-Union Association, Etang- areas in its native range of Sulawesi, cut down Salé, La Réunion) and Jean-Claude Sevathian the staminate tree he had planted to eliminate (Mauritius Wildlife Foundation, Vacoa, production and any possibilities of its Mauritius) for their personal communications escaping from cultivation and becoming and often unpublished data on naturalized naturalized in Tahiti (Hodel 1993). The palms in tropical islands worldwide. eradication of Dypsis madagascariensis in the island of Moorea (French Polynesia) still seems LITERATURE CITED possible before dense stands are formed or BAAS BECKING, L.G.M. 1950. Liste préliminaire before individuals are found at higher de plantes introduites à Tahiti. Commission elevation and on steep slopes. du Pacifique Sud, Document Technique N°7, In 1999, Meyer officially advised the Nouméa, 20 pp. Department of the Environment of French CORDEMOY, E.J. DE 1895. Flore de l’île de la Polynesia to ban introduction of Licuala Réunion. Paul Klincksieck, Paris, 574 pp. grandis, Washingtonia spp. and Elaeis guineensis. CSURHES, S. AND R. EDWARDS. 1998. Potential All new importation of palms of the genera Environmental Weeds in Australia. , Areca, Arenga, Borassus, Dypsis, Environment Australia, Biodiversity Group, Corypha, Howea, Livistona, Ptychosperma and Canberra, 208 pp. Roystonea, as well as Elaeis guinensis, Washingtonia robusta and Phoenix dactylifera, DELNATTE, C. 2003. La Guadeloupe face aux are officially illegal in French Polynesia (Decree espèces allochtones. Etude préalable N°276 CM 23 May 2005), primarily because d’évaluation de la menace des espèces of the risk of disease to the coconut, the most végétales invasives dans le Parc National de economically important plant of the islands. Guadeloupe. DESS Ressources Naturelles et Environnement, Université de Metz. More recently, 421 additional palm species Unpublished thesis,189 pp. belonging to 130 genera and representing more than 51,000 individuals have been DENSLOW, J.S. 1998. Weeds in paradise: officially introduced from 2000 to 2006 to La thoughts on the invisibility of tropical islands. Ann. Missouri Bot. Gard. 90: Réunion for a “Palm Botanical Garden” project 119–127. carried out by the Commune du Tampon (A. Hoarau, pers. comm. 2007). A careful screening DUNLOP, E., J. HARDCASTLE AND N.J. JIVAN SHAH. of all these species, currently cultivated in a 2005. Cousin and Cousine Islands. Status plant nursery, should be conducted before and management of alien invasive species. planting them out. Gardeners, horticulturists Nature Seychelles, Victoria. Unpublished and landscapers could become key allies in the report, 65 pp. prevention and control of invasive alien plants FULLER, D. 1997. Conservation Status, Diversity in tropical islands, thus preserving their unique and Systematics of the Indigenous Palms of biodiversity. Fiji. University of the South Pacific, Suva, Acknowledgments Fiji, Unpublished MSc. thesis, 152 pp. We deeply thank Rémy Amice (Direction des GROVES, R.H. AND J.R. HOSKING. 1997. Recent Affaires Alimentaires, Vétérinaires et Rurales, incursions of weeds in Australia 1971–1995. Nouméa, New Caledonia), Fabien Barthelat Technical Series N°3, CRC for Weed (Direction de l’Agriculture et de la Forêt, Management Systems, Australia, Adelaïde, Mamoudzou, Mayotte), Mark J. Bonin 74 pp. (Samoan National Invasive’s Task Team, Apia, HODEL, D.R. 1982. Cultivated palms in Tahiti Western Samoa), César Delnatte (Herbier de and The Jardin Botanique de Papeari. Guyane, Cayenne, French Guiana), Wayne Principes 26: 77–85.

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HODEL, D.R. 1993. The growth of some palms Miconia calvescens DC. (Melastomataceae). J. in Tahiti. Principes 37: 127–138. Biogeography 23: 775–781.

HSUAN KENG CHIN, S.C. AND H.T.W. TAN. 1998. MEYER, J.-Y. 1998. Mécanismes et gestion des The Concise Flora of Singapore. Volume II: invasions biologiques par des plantes . Singapore University Press, introduites dans des forêts naturelles à National Park Board, Singapore, 215 pp. Hawai’i et en Polynésie française : une étude HUSSEY, B.M.J., G.J. KEIGHERY, J. DODD, S.G. de cas. Rapport d’étude post-doctorale, LLOYD AND R.D. COUSENS. 2007. Western Délégation à la Recherche, Papeete. Weeds. Second Edition. The Weeds Society Unpublished post-doctoral report, 72 pp. of Western Australia (Inc.), Perth, 294 pp. MEYER, J.-Y. In press. The snake-like climber JACQUIER, H. 1960. Enumération des plantes Anodendron paniculatum (Apocynaceae), a introduites à Tahiti depuis la découverte “new” invasive liana in the rainforests of jusqu’en 1885. Bull. Soc. Etud. Océan. 130: Tahiti (Pacific Ocean). Aliens (IUCN/ISSG). 117–146. MEYER, J.-Y. AND C. LAVERGNE. 2004. Beautés JONES, D.L. 1995. Palms Throughout the World. fatales: Acanthaceae species as invasive alien Smithsonian Institution Press, Washington, plants on tropical Indo-Pacific Islands. DC., 410 pp. Diversity & Distrib. 10: 333–347.

KAIRO, M.A.B., O. CHEESMAN, K. HAYSOM AND S. MOORE, H.E., JR. AND L.J. GUÉHO. 1984. Famille MURPHY. 2003. Invasive Species Threats in 189. Palmiers. In: T.L. BOSSER, J. CADET, J. the Caribbean Region. CAB International, GUÉHO AND W. M ARAIS (eds.), Flore des Trinidad & Tobago. Unpublished report to Mascareignes. The Sugar Industry Research the Nature Conservancy, 132 pp. Institute, Mauritius, ORSTOM, Paris, and the LAVERGNE, C., C. DURET, L. GIGORD, L. GROSSET Royal Botanic Gardens, Kew. AND L. REICHSTEINER 2007. Les palmiers OPPENHEIMER, H.L. AND R.T. BARLETT. 2002. New menacés de l’Ile Maurice et de ses îlots (22 plant records from the main Hawaiian mars–2 avril 2006). Association Palmeraie- Islands. In: N.L. EVENHUIS AND L.G. ELDREDGE Union, La Réunion. Unpublished report, 36 (eds.), Records of the Hawaii Biological pp. Survey for 2000. Part 2: Notes. Bishop Mus. LAVERGNE, R. 2001. Plantes du Jardin Occas. Papers 69:1–14. d’Acclimatation: mise à jour de la RICHARDSON, F.J., R.G. RICHARDSON AND R.C.H. nomenclature utilisée au siècle dernier par SHEPHERD. 2006. Weeds of the South-East. An les deux jardiniers-botanistes dans leurs Identification Guide for Australia. R. G. and catalogues: Nicolas Bréon en 1825 et Jean- F. J. Richardson, Meredith, 438 pp. Marie Richard en 1856. Unpublished report, 109 pp. ROUILLARD, G. AND J. GUÉHO. 1981–1985. Histoire des Plantes d’Intérêt Horticole, LAZARIDES, M., K. COWLEY AND P. H OHNEN. 1997. Médicale et Economique à l‘Ile Maurice 1. CSIRO Handbook of Australian Weeds. Henry & Cie, Ltée, Les Pailles, 289 pp. CSIRO, Canberra, 264 pp. ROUILLARD, G. AND J. GUÉHO. Eds 1999. Les LORENCE, D.H. AND R.W. SUSSMAN. 1986. Exotic Plantes et leur Histoire à l’Ile Maurice. MSM species invasion into Mauritius wet forest Ltd., Port-Louis, 752 pp. remnants. J. Trop. Ecol. 2: 147-162. SMITH, A.C. 1979. Flora Vitiensis Nova. A New LUDWIG, N. 2006. Acanthophoenix in Réunion, Flora of Fiji, Vol. 1. Pacific Tropical Botanical Mascarene Islands. Palms 50: 82–98. Garden, Lawai, 495 pp. MACKEE, H.S. 1985. Les plantes introduites et SPACE, J.C. AND M. FALANRUW. 1999. cultivées en Nouvelle-Calédonie. Muséum Observations on invasive plant species in National d’Histoire Naturelle, Laboratoire de Micronesia. USDA Forest Service, Honolulu. Phanérogamie, Paris, 159 pp. Report to the Pacific Islands Committee, MARTZ, C. AND B. MARTZ. 2003. Les Raphia Council of Western State Foresters. USDA farinifera de la Rivière Saint-Louis. Magazine Forest Service, Honolulu. 32 pp. de Palmeraie-Union Latania 5: 10–11. STAPLES, G.W. AND D.R. HERBST. 2005. A Tropical MEYER, J.-Y. AND J. FLORENCE. 1996. Tahiti’s Garden Flora. Plants cultivated in the native flora endangered by the invasion of Hawaiian Islands and in other tropical

82 PALMS Meyer et al.: Invasive Palms Vol. 52(2) 2008

islands. Bishop Museum Press, Honolulu, diversity Management. Kluwer Academic 908 pp. Publishers, Dordrecht, 448 pp.

STARR, F., K. STARR AND L. LOOPE. 2003a. Livistona SVENNING, J.-C. 2002. Non-native ornamental chinensis. Chinese fan palm, Arecaceae. palms invade a secondary tropical forest in USGS-BRD, Haleakala Field Station, Maui, Panama. Palms 46: 81–86. Hawai’i. Unpublished report, 4 pp. WAGNER, W.L., D.R. HERBST AND S.H. SOHMER. STARR, F., K. STARR AND L. LOOPE. 2003b. 1990. Manual of the Flowering Plants of Washingtonia spp. Mexican fan palm and Hawaii. Volume 2. University of Hawaii California fan palm, Arecaceae. USGS-BRD, Press, Bishop Museum Press, Honolulu: Haleakala Field Station, Maui, Hawai’i. 989–1853. Unpublished report, 5 pp. WATLING, D. 2005. Palms of the Fiji Islands. STRAHM, W. 1993. The conservation and Environmental Consultants, Fiji. Ltd. 192 restoration of the flora of Mauritius and pp. Rodrigues. University of Reading. Unpublished PhD thesis, 240 pp. WHITMORE, T.C. 1973. Palms of Malaya. Oxford University Press, London, 148 pp. STRAHM, W. 1999. Invasive species in Mauritius: examining the past and charting the future, ZONA, S. 1996. Roystonea (Arecaceae: Arecoid- pp. 325–347 In: O.T. SANDLUNG, P. SCHEI AND eae). Fl. Neotrop. Monogr. 71: 1–36. A. VIKEN. (eds), Invasive Species and Bio-

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