American Journal of Botany 91(11): 1814±1827. 2004. PLANT-POLLINATOR INTERACTIONS IN NEW CALEDONIA INFLUENCED BY INTRODUCED HONEY BEES1 MAKOTO KATO2 AND ATSUSHI KAWAKITA Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-Nihonmatsu-cho, Sakyo-ku, Kyoto, 606±8501 Japan The ¯ora of New Caledonia is characterized by remarkably high species diversity, high endemicity, and an unusual abundance of archaic plant taxa. To investigate community-level pollination mutualism in this endemic ecosystem, we observed ¯ower visitors on 99 plant species in 42 families of various types of vegetation. Among the 95 native plant species, the most dominant pollination system was melittophily (bee-pollinated, 46.3%), followed by phalaenophily (moth-pollinated, 20.0%), ornithophily (bird-pollinated, 11.6%), cantharophily (beetle-pollinated, 8.4%), myophily (¯y-pollinated, 3.2%), chiropterophily (bat-pollinated, 3.2%), and anemophily (wind- pollinated, 3.2%). The prevalence of ornithophily by honeyeaters shows an ecological link to pollination mutualism in Australia. The relative dominance of phalaenophily is unique to New Caledonia, and is proposed to be related to the low diversity of the original bee fauna and the absence of long-tongued bees. Although some archaic plants maintain archaic plant-pollinator interactions, e.g., Zygogynum pollinated by micropterigid moths, or Hedycarya pollinated by thrips and staphylinid beetles, the most dominant organism observed on ¯owers was the introduced honey bee, Apis mellifera. The plant species now visited by honey bees are thought to have originally been pollinated by native solitary short-tongued bees. Our data suggest that the unique systems of pollination mutualism in New Caledonia are now endangered by the establishment of highly invasive honey bees. Key words: bird pollination; honey bee invasion; New Caledonia; plant-pollinator interactions; pollination. The ¯ora of New Caledonia is characterized by remarkably that the archaic Zygogynum subsp. are pollinated by primitive high species diversity (about 3000 species of seed plants) and micropterigid moths (Thien et al., 1985; Pellmyr et al., 1990) high endemicity (84%; Morat et al., 1984; Jaffre et al., 2001). that do not have nectar-collecting proboscides. The high diversity and endemicity result from the long history However, community-level studies on plant-pollinator inter- of this land mass remaining above sea level after the breakup actions have not yet been made in New Caledonia. Such stud- of Gondwanaland in the Mesozoic; they are also the result, in ies are important and necessary, because plant-pollinator in- part, of the climatic and geological diversity of habitats within teractions on oceanic islands are easily and rapidly degraded Grand Terre Island. The ¯ora of New Caledonia is also char- by the invasion of honey bees (Kato, 1992; Kato et al., 1999; acterized by an unusual abundance of archaic plant taxa (i.e., Dupont et al., 2004). Social bees were originally absent on basal angiosperm lineages), such as the Amborellaceae, Win- most oceanic islands, as it was often dif®cult for them to cross teraceae, and Monimiaceae (Takhtajan, 1986). The Amborel- the sea (Michener, 1979). Although New Caledonia is not an laceae are thought to be the most basal family of angiosperms oceanic island but rather a fragment of Gondwanaland, the (Soltis et al., 1999). These attributes of New Caledonian ¯ora only bees originally recorded in New Caledonia are solitary have attracted botanical and ecological interest, inspiring many short-tongued bees in the families Colletidae, Halictidae, and studies of plants on the islands (e.g., De Laubenfels, 1959; Megachilidae (Michener, 1965). Because honey bees can com- Jaffre et al., 1976; Thien et al., 1985, 2003; Pellmyr et al., municate the exact site of ¯owers to nestmates by dancing, 1990; Carpenter et al., 2003; Kawakita and Kato, 2004). they have often outcompeted native solitary bees, not only on The ¯oristically distinct area termed the New Caledonia oceanic islands but also in Australia (Paton, 1993), North Subkingdom by Takhtajan (1986) also provides a fascinating America (Barthell, 2001), and the Neotropics (Roubik, 1978), ecosystem from the perspective of pollination mutualism. It is where social bees (stingless bees and/or bumblebees) but not of great ecological and evolutionary interest to investigate honey bees were native. original plant-pollinator interactions that have potentially Because the ¯ora of New Caledonia has links with Austra- shaped the uniqueness and richness of the ¯ora in New Ca- lia, New Guinea, and New Zealand (Morat et al., 1984), plant- ledonia. Community-level plant-pollinator interactions are pollinator interactions are predicted to be similar to those in founded on mutualisms between plants and their pollinators, Gondwanaland. Pollination systems of various plants in New as well as on competition between plants for pollinators, and Zealand were observed from 1920 to 1935, when introduced competition between pollinators for ¯oral resources (Waser honey bees were not as abundant as they are now (Thomson, and Real, 1979; Kevan and Baker, 1983). Pioneering works 1927; Heine, 1938). The data of these pioneering studies sug- on pollination systems in New Caledonia have demonstrated gest that the most dominant pollination system in New Zealand was myophily, followed by general entomophily, melittophily, 1 Manuscript received 14 December 2003; revision accepted 30 July 2004. and ornithophily. However, the increase in populations of in- The authors thank C. Lambert, T. Joseph, J.-J. Cassan, R. PouytieÂla, and troduced honey bees and bumblebees caused a decrease in all other staff at the Direction des Ressources Naturelles de la Province Sud native pollinators (Craig et al., 2000). The drastic changes in et Nord for their assistance and permission to study in New Caledonia, and pollination mutualism in New Zealand suggest that it is urgent, A. Takimura, L. Daniel, and T. Atkins for their help in the ®eld. This study was supported by a Japan Ministry of Education, Culture, Science, Sports, if it is not already too late, that study of the original systems and Technology Grant-in-Aid for Scienti®c Research (#12440217). of pollination mutualism in New Caledonia be undertaken. 2 E-mail: [email protected]. To investigate community-level pollination mutualism in the 1814 November 2004] KATO AND KAWAKITAÐPOLLINATION SYSTEMS IN NEW CALEDONIA 1815 TABLE 1. A list of study sites where we made surveys on ¯ower visitors in New Caledonia, with latitude, longitude, altitude, vegetation and rocks at each site. Code Site Latitude Longitude Altitude Vegetationa Rockb S1 Tiebaghi 208 27.39S 164813.19E 350±580 M/F U S2 Chagrin 208 26.19S 164815.09E 30±150 S S S3 La Koumac 208 32.29S 164820.89E 100±200 F C S4 La Bouverie 208 27.99S 164820.49E 100±200 S S S5 Koumac 208 34.69S 164817.99E 0±5 G A S6 Col de Amoss 208 18.69S 164825.19E 300±350 F A S7 Tinip 208 47.59S 164827.49E 10±80 L A S8 Voh 208 56.29S 164843.89E 0±20 S A S9 Oundjo 218 8.79S 164845.39E 0±5 G A S10 Pouembout 218 11.29S 164853.19E 10±50 S C S11 Pindai 218 17.19S 164858.59E 10±60 L C S12 Nepoui 218 18.19S 16580.39E 10±50 L C S13 Hiengene 208 40.19S 165855.49E 10±40 F A S14 Col de Tango 218 0.29S 16481.49E 200±250 F A S15 Bopope 208 54.59S 16587.19E 300±400 F A S16 Poindimie 208 56.69S 165821.69E 0±20 F A S17 Cap Bocage 218 10.29S 165832.49E 0±20 M/G U S18 Chute de Ba 218 11.99S 165833.69E 20±50 F U S19 Col des Roussettes 218 25.99S 165827.19E 250±300 F U S20 Poro 218 20.09S 165844.19E 100±250 M U S21 Kouaoua 218 23.59S 165846.49E 200±250 M U S22 Col de Amieu 218 35.59S 165848.59E 300±360 F A S23 Plateau de Dogny 218 36.99S 165852.39E 400±1010 F A S24 Saramea 218 38.59S 165851.39E 140±190 F A S25 Mt. Mou 228 4.019S 165820.29E 500±1219 F/M U S26 Mt. Koghi 228 10.79S 166830.99E 400±1075 F/M U S27 Noumea 228 16.49S 166824.09E 0±5 S C S28 Riviere Bleue 228 6.09S 166839.59E 100±300 M/F U S29 Col de Mouirange 228 13.39S 166840.39E 300±400 M U S30 Prony 228 19.49S 166848.29E 50±150 M U S31 Col de Yate 228 9.89S 166854.09E 300±400 M U a F: forest; M: mangrove; L: sclerophyllus forest; M: maquis; S: shrubby savanna. b A: acidic; C: calcarious; S: silicaceous; U: ultrabasi®c. endemic ecosystem in New Caledonia, we surveyed pollinator looked at whether or not birds visited the ¯owers by studying the ¯owers visits to the ¯owers of diverse species of various vegetation from at least 10 m away for an additional 15 min. For ¯owers that were not types. We observed 99 plant species, encompassing 42 fami- visited by insects or birds during the daytime or that did not receive visits lies of most major lineages of ¯owering plants. Our data high- that would have led, in all likelihood, to effective pollination, we made ad- light the uniqueness of pollination mutualism in New Cale- ditional observations in the evening and/or at night. Visitations by nocturnal donia, its links to other vegetation in the world, and the en- insects and bats were studied as described for diurnal insects and birds, re- dangered status of the observed interactions. This is the ®rst spectively. Thus, a data set of all bird/insect visits to ¯owers was created. study that describes community-level plant-pollinator interac- Principal components analysis and cluster analysis were performed on the tions in this ¯oristic region, i.e., in the New Caledonian Sub- data set to detect patterns of anthophilous insect communities on different kingdom.