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Home , Agonoxena, Agonoxena argaula, Alex (moth), Araecerus, Capricornia (moth), Crocothemis

Surveys on Palmyra , Line , and Insights into the Decline of the Native Tree Pisonia grandis (Nyctaginaceae)1

Alex T. Handler,2,3,7 Daniel S. Gruner,3,4 William P. Haines,5 Matthew W. Lange,6 and Kenneth Y. Kaneshiro3

Abstract: , in the of the equatorial Pacific, supports one of the largest remaining native stands of Pisonia grandis forest in the tropical Pacific Ocean. In 2003, we surveyed terrestrial to document extant native and introduced richness, compare these lists with historical rec- ords, and assess potential threats to native species and ecosystem integrity. In total, 115 arthropod taxa were collected, bringing the total number of taxa re- corded since 1913 to 162. Few native species were collected; most taxa were ac- cidental introductions also recorded from the , the presumed main source of introductions to Palmyra. The overlap with previous historical surveys in 1913 and 1948 was low (<40%), and new species continue to estab- lish, with one species of whitefly reaching pest status between 2003 and 2005. We observed numerous dead or dying large Pisonia grandis, and the green scale Pulvinaria urbicola (Coccidae) was particularly abundant on trees of poor health. Abundant introduced , particularly megacephala, tended this and other hemipterans feeding on both native and introduced plants. We hypothesize that the Pheidole-Pulvinaria facultative mutualism is causing the decline of Pisonia grandis. Because of the unique properties of Pisonia grandis forest on oceanic , its importance for nesting seabirds, and its alarming global decline, im- mediate conservation efforts should be directed at controlling introduced Hemip- tera and disrupting their mutualisms with nonnative ants on Palmyra Atoll.

As biogeographic barriers break down in travel, introduced species have become a the face of increasing global commerce and dominant component of global environmen- tal change (Vitousek et al. 1999, Mack et al. 2000). Oceanic islands are among the systems 1 Funding for this work was provided by NSF GK-12 most vulnerable to biological invasion and Grant no. DGE02-32016 and the U.S. Fish and Wildlife homogenization (D’Antonio and Dudley Service. This is contribution no. 2368, Bodega Marine Laboratory, University of at Davis, Davis, Cal- 1995, Cowie 2001). Their small size allows ifornia. Manuscript accepted 7 January 2007. coexistence of fewer total species in small 2 Corresponding author: [email protected]. populations relative to continents, and their 3 Center for Conservation Research and Training, native biota evolved in geographic isolation University of Hawai‘i at Ma¯noa, , Hawai‘i 96822. from many functional forms of 4 Bodega Marine Laboratory, University of California and competition (Carlquist 1974, Wilson at Davis, Bodega Bay, California 94923. 1996, Whittaker 1998). Although the replace- 5 Department of Plant and Environmental Protection ment of endemic species by introduced Sciences, University of Hawai‘i at Ma¯noa, Honolulu, Ha- species may actually increase local species wai‘i 96822. 6 , Palmyra Atoll National and functional diversity on islands (Sax and Wildlife Refuge. Gaines 2003), regional homogenization of 7 PowerPlants LLC, Honolulu, Hawai‘i biotic communities causes decline in total 96816. global diversity (Samways 1999, Olden et al. 2004). Pacific Science (2007), vol. 61, no. 4:485–502 Palmyra is a remote atoll in the northern : 2007 by University of Hawai‘i Press Line Islands (Figure 1), approximately 2,000 All rights reserved km south-southwest of the Hawaiian Ar-

485 486 PACIFIC SCIENCE . October 2007

Figure 1. Palmyra Atoll, northern Line Islands, equatorial Pacific Ocean. chipelago (5 53 0 600 N, 162 60 11 00 W ). The rare stands of Pisonia grandis R. Br. (Nyctagi- atoll consists of roughly 50 small, low , naceae). Many of these native species are with a total land area of less than 5 km2 and listed as threatened or endangered because a maximum elevation of 2 m, all surrounded of historical human exploitation and habitat by a barrier . With an average annual disturbance throughout their ranges and con- rainfall of more than 4 m, Palmyra is a wet tinued impacts of introduced species (IUCN atoll within the Inter-tropical Convergence 2004). Zone (Mueller-Dombois and Fosberg 1998). Palmyra probably did not support persis- This high rainfall, coupled with huge nutrient tent populations of indigenous peoples, influx in the form of from thousands although there is evidence of sporadic Poly- of resident seabirds and migratory shorebirds, nesian occupation (Dawson 1959, Wester supports thickly vegetated rain forest that is 1985). However, in the brief 200-yr history unique even in comparison with nearby, since European seafarers stumbled upon it, more arid islands such as (Wester intense human disturbance has severely im- 1985). The atoll is home to a relatively intact pacted the atoll (Dawson 1959). Fanning first and diverse marine ecosystem; 29 species of sighted the atoll in 1798, but it was named birds; the crab (Birgus latro L.), the when an American ship, The Palmyra, drifted world’s largest terrestrial arthropod (Reyne onto its shores after a storm on 7 November 1939, Chauvet and Kadiri-Jan 1999); and 1802. In 1862, Kamehameha IV claimed Pal- Palmyra Arthropod Invasions . Handler et al. 487 myra as part of the . Pal- Rock and Montague Cooke on a 1913 expedi- myra Atoll was recognized in turn as a U.S. tion (Swezey 1914). Krauss (1953) reported territory with the annexation of Hawai‘i in an additional 70þ taxa from an expedition in 1898. The atoll passed variously through 1948, overlapping minimally with Swezey’s public and private ownership until 2001, in- list. A comprehensive assessment of the ter- cluding a period of intense military occupa- restrial arthropod fauna has never been per- tion from 1938 to 1961. During that period, formed, and it is not known whether any the U.S. Navy dredged and built native arthropods persist, aside from four spe- bunkers, recreation centers, an airstrip, a hos- cies of abundant land crabs—B. latro, Cardi- pital, and causeways connecting islets. During soma carnifex (Herbst.), Coenobita brevimanus peak occupancy, the 182 ha of land area sup- Dana, and Coenobita perlatus H. Milne Ed- ported over 6,000 naval personnel and sub- wards. stantial infrastructure (Dawson 1959, Anon. In 2003, we conducted terrestrial arthro- 1998). In 2001, Palmyra Atoll was designated pod surveys on Palmyra Atoll. The goals of a of the U.S. Fish the study were to: (1) compile a current list and Wildlife Service. Currently, Palmyra of terrestrial arthropod species from con- Atoll is jointly owned and managed by The temporary sampling; (2) determine probable Nature Conservancy and the U.S. Fish and biogeographic origins or residency status (in- Wildlife Service (Anon. 1998) and is unin- troduced, indigenous, or endemic) for all taxa; habited except for a small cadre of scientists, (3) compare these lists with the record from resource managers, and transient crew. historical expeditions; and (4) assess potential The hallmark indigenous plant species of threats to native species and ecosystem integ- the atoll is Pisonia grandis, which grows to rity. These surveys were necessary to develop heights often exceeding 30 m in dense mono- a management and conservation plan for dominant stands in some of the largest tracts the terrestrial resources and of remaining on tropical Pacific islands (Walker Palmyra Atoll. We report an important new 1991a, Mueller-Dombois and Fosberg 1998). threat to P. grandis (a facultative mutualism With sticky fruits dispersed by seabirds (Airy between introduced ants and scale ), Shaw 1952, Burger 2005), P. grandis forests review the literature on this association from are widespread throughout the Indo-Pacific other Pacific islands, and provide recommen- region but are often locally rare and declining dations for quarantine and conservation. within their native range (Walker 1991a, Mueller-Dombois and Fosberg 1998, Kay et al. 2003). On Palmyra Atoll, P. grandis for- materials and methods est supports indigenous bird’s-nest ferns (As- Arthropod Surveys plenium nidus L.) in the canopy and laua‘e fern, Phymatosorus scolopendria (Burm.), in the The terrestrial arthropod fauna was surveyed understory. The remainder of the native flora during two visits to Palmyra (28 March–1 consists primarily of indigenous strand spe- April and 8–18 June 2003), supplemented by cies found on many islands in the Pacific, subsequent opportunistic collections. Because such as beach heliotrope (Tournefortia argen- of the time constraints of the survey expedi- tea L. f.), sericea Vahl, and Pandanus tions and the remoteness of Palmyra Atoll, tectorius Parkinson. One plant variety is con- we were unable to complete detailed quanti- sidered endemic to Palmyra: a grass, Lepturus tative sampling. Therefore, no attempt was repens (G. Forst.) R. Br. var. palmyrensis, which made to quantify population sizes, commu- is found in scattered patches throughout the nity structure, or species richness, or define atoll. habitat associations and distributions of The historical record for terrestrial arthro- arthropod taxa. The absence of particular pod species on Palmyra Atoll is sparse. Otto taxa does not preclude their presence on the Swezey published a list of 18 taxa, identified atoll. However, we are confident that the at various resolution, collected by Joseph most common and widespread terrestrial ar- 488 PACIFIC SCIENCE . October 2007 thropods present on the atoll in 2003 were and at the University of Hawai‘i Mu- collected and identified. seum (Honolulu, Hawai‘i). Malaise traps, light traps, and blacklighted sheets were used to sample active cursorial results and flying arthropods (Southwood and Hen- derson 2000, Toda and Kitching 2002). Mal- We recognized 113 arthropod taxa from our aise traps were set on Cooper, Eastern, Sand, surveys (Figure 2, Appendix). The majority and South Islets and left in place between of taxa were identified to the species level, 2 and 5 days. A total of eight malaise trap but some were identifiable only to or samples was taken in March–April and June . (Diptera, 38 species) were the 2003. Bucket-type light traps (Bioquip, Inc.) most species-rich, followed by and were set overnight on Cooper (2 trap-nights), ants (, 20 species), (Co- Dudley, Lesley, Lost, Sand, and South Islets, leoptera, 19 species), (Araneae, nine for a total of 7 trap-nights in June 2003. species), hemipterans (including Heterop- Vegetation was sampled using sweep nets tera and Homoptera, nine species), crickets and beating sheets and by visual inspection and grasshoppers (, six species), and excavation of leaves, flowers, fruits, and (, six species); the branches, and bark. To sample the epigean remaining six species belonged to other or- fauna, several designs of pitfall traps were ders. All beetles and ants were unequivocal tested but all failed because of the rapid and historical introductions, but some flies and pervasive interference of coconut crabs. Soil other taxa could not be identified to species cores were not taken systematically because or their biogeographic status could not be de- of the rocky substrate and lack of soil in termined. many areas. Therefore, we sifted litter and Our current surveys added to taxa reported soils onto beating sheets and collected visible by historical surveys, bringing the total list to arthropods with forceps and aspirators. Ants 163 taxa recorded from Palmyra since 1913 were sampled by baiting with peanut butter (Appendix). Previously, 88 taxa had been re- and canned lunch meat, as well as opportunis- corded (Swezey 1914, Krauss 1953), 68 of tic collecting and litter sifting. which were identified to the species level; of Most arthropods were collected into 95% these, at least 32 were recollected (Figure 3), ethanol. Lepidopteran adults collected with although voucher specimens for some histor- lights were killed with ethyl acetate, field ically collected taxa could not be located to mounted when possible, and stored in desic- compare with contemporary specimens. Of cation chambers. With the aid of specialists taxa identified to the species level, 36 species (see Acknowledgments) and by reference to recorded during the two historical surveys historical museum specimens, all taxa were were not recollected, and 51 of 87 (59%) identified to the highest possible taxonomic were new records for the atoll. resolution. For taxa identified to genus or Of the 119 taxa identified to the species species, biogeographic origins and residency level from Palmyra, most (106 taxa, 89%) are status were inferred from professional com- also recorded from the Hawaiian Islands munication and the literature (e.g., Nishida (Nishida 2002). Most of these (99 species, 2002). 93%) are considered accidental introductions In addition to the specimens collected dur- to Hawai‘i, whereas only three species (all ing these surveys, we have included speci- coccinellid beetles) were purposefully intro- mens collected during focused surveys in duced for biological control (Nishida 2002). 2001 and 2004 (M. Richardson, unpubl. data; There is no evidence of intentional introduc- P. Krushelnycky and P. Lester, unpubl. data), tions to Palmyra; thus all introduced species mosquito surveys in 2002 (Depkin 2002), and on Palmyra are considered accidental intro- opportunistic collections between 2003 and ductions. The majority of species now re- 2005 (A.T.H. and M.W.L.). Voucher speci- corded from Palmyra Atoll fall into this class mens are deposited at the Bishop Museum (102/119, 86%). Palmyra Arthropod Invasions . Handler et al. 489

Figure 2. Summary of introduced, native, and cryptogenic species richness within arthropod orders from recent col- lections, 2003–2005.

Only seven contemporary taxa were classi- lestum Parent) and the gryllid in the fied as indigenous species. These include genus Ornebius. Several possibly indigenous three odonates, Anax junius (Drury), Pantala taxa were collected in historical surveys but flavescens (Fabricius), and Ischnura aurora Brau- not recollected during our trips. These in- er; a predaceous tettigoniid katydid, Phisis clude the tetragnathid Tetragnatha key- holdhausi Karny; a marine water strider, serlingi Simon, the mirid bug Trigonotylus Halobates micans Eschscholz; a cranefly, Styr- brevipes Jakovlev, the gryllid cricket Speonemo- ingomyia didyma Grimshaw; and an isopod, bius tigrinus (Saussure), the butterfly Hypolim- Australophiloscia societatis (Maccagno) (Appen- nas bolina Linnaeus (Nymphalidae), and the dix). All of these species are distributed in flies Dasyrhicnoessa insularis (Aldrich), Noctica- the equatorial Pacific and occur naturally nace marshallensis Wirth, Chrysotus javanensis in similar habitats on neighboring islands de Meijere, and Olfersia aenescens Thomson. (Walker and Deitz 1979, Jin et al. 1991, Nishida 2002, Evenhuis 2005, Harada 2005). The crambid Piletocera signiferalis (Wal- discussion lengren) is widespread in the Pacific (Clarke Introduced Invertebrates 1986) and may be native to Palmyra, but it is unclear to what extent its distribution is natu- Although the true extent of native biodiver- ral. Several other taxa are possibly native, but sity before human arrival on Palmyra will less is known concerning their natural distri- never be known, the contemporary terrestrial butions or species-level identifications: two invertebrate fauna is dominated by intro- species of dolichopodid flies (Chrysosoma com- duced species. The great majority of the plicatum Becker and Chrysosoma sp. near mo- recorded species are accidentally or purpose- 490 PACIFIC SCIENCE . October 2007

Figure 3. Species richness of introduced, native, and cryptogenic arthropods collected only in historical (1913, 1948) and recent (2003–2005) collections, and in both sampling periods (shared species). Uncertain historical natives (n ¼ 8, Appendix) are classified as cryptogenic. fully introduced species also reported from flect the greater comprehensiveness of our the Hawaiian Islands (106/119, 89% [Nishida recent assessments, or it may suggest that the 2002]). Thus, we suggest that Hawai‘i was the introduction rate has tailed off since the peak predominant historical source of exotic ar- of human activity (i.e., military occupation) thropod propagules, most likely during the ceased in 1961. Still, there was a surprising period of heavy military occupation and tran- degree of nonoverlap between our collections sit (1938–1961). Military installations have and species lists from Swezey (1914) and been blamed for other introductions of pes- Krauss (1953). Of the 87 identified species tiferous tramp species to Hawai‘i during that we collected, 52 (63%) were not recorded in time period (e.g., Argentine ant, Linepithema historical surveys. humile [Zimmerman 1941]), and Hawai‘i has No species were clearly endemic to Pal- always been the dominant shipping connec- myra (Appendix), but because any endemic tion to Palmyra Atoll (Dawson 1959). species would be undescribed, it remains pos- Krauss (1953) reported almost no overlap sible that endemic species exist among the of the 70þ taxa encountered in 1948 with specimens not identified to the species level. those recorded during the surveys reported Nevertheless, invasive arthropod species dom- by Swezey (1914)—the earwig Euborellia an- inated the atoll in terms of overall richness nulipes (Lucas) was the only species confirmed and qualitative abundance. For most of these from both surveys. Our recent collections species, there is little information on their show a somewhat higher ratio of overlap with effects on native species or ecosystem func- previous collections (Figure 3). This may re- tion. However, two groups of invasive insects Palmyra Arthropod Invasions . Handler et al. 491 that were particularly abundant, with well- Kay et al. 2003). Repeated defoliation events documented impacts on native vegetation and eventual death of many large trees have (ants and hemipteran phloem-feeding insects) been observed since 2003 (Figure 4). Concur- are discussed here. rent with these defoliation events, the esti- mated spatial extent of healthy P. grandis stands decreased more than 30% from 2002 The Pisonia-Pulvinaria-Pheidole Problem to 2005, and the stands were increasingly The terrestrial habitats of Palmyra are valued fragmented (Figure 5) (A. Wegmann, unpubl. for conservation because the atoll features data). Currently, numerous invading inver- some of the largest remaining stands of tebrates may be acting synergistically to P. grandis forest (Wester 1985, Mueller- threaten the viability of the P. grandis popula- Dombois and Fosberg 1998). Pisonia grandis tion on Palmyra Atoll. Quantitative data are occurs primarily on small islands throughout needed to unambiguously ascribe causes and the tropical Indo-Pacific where seabirds nest effects; here, we document the resident ar- (St. John 1951, Airy-Shaw 1952, Stemmerik thropod species and review the literature per- 1964, Mueller-Dombois and Fosberg 1998, tinent to this phenomenon. Burger 2005). The distribution of P. grandis At least 10 species of ants were found in is usually attributed to both the spread of recent surveys, the most notorious of which seeds stuck to the feathers of seabirds and are the African big-headed ant, Pheidole mega- growth facilitated by bird guano (Airy-Shaw cephala (Fabricius); crazy ants Paratrechina 1952, Stemmerik 1964, Burger 2005). As the bourbonica (Forel) and P. vaga (Forel); and dominant native tree on Palmyra, P. grandis the Guinea ant, Tetramorium bicarinatum is a characterizing feature of the terrestrial (Nylander). Ants were present in high den- ecosystem and provides nesting and roosting sities throughout the atoll, but Ph. mega- sites for seabirds, especially white terns, Gygis cephala was the dominant species on most alba (Sparrman), and noddies, Anous islets. On islets where Ph. megacephala was minutus Boie. Walker (1991a) found that the not found, T. bicarinatum and Paratrechina size of breeding colonies of black noddies bourbonica were the local dominant species. was positively associated with the areal extent Introduced ants and other social insects (e.g., and maximum height of P. grandis stands on paper Polistes aurifer Saussure) can be Great Barrier Reef islands. The height of devastating generalist predators of native in- the canopies may provide protection from in- sects on oceanic islands where native social troduced black rats, which can prey on adult insects are depauperate or entirely lacking birds and nestlings (Stapp 2002). Moreover, (Cole et al. 1992, Wilson 1996, Gerlach these forests on coralline substrates, in com- 2004, Krushelnycky et al. 2005, Le Breton bination with the high densities of nesting et al. 2005). seabirds, create a phosphate-rich humic soil In 2003, we observed these ants farming an substrate not otherwise found on oceanic unrecorded , Pulvinaria urbicola cays and atolls (Walker 1991a, Mueller- (Cockerell & Parrott), on P. grandis leaves. Dombois and Fosberg 1998). A healthy stand Although unidentified at the time, an out- tends to contain limited understory growth— breaking insect was observed on P. grandis in and invasion by nonindigenous plants— close association with ants as early as August because the broad-leaved, tall canopy pre- 2001 (Depkin 2002). By March 2002, Depkin vents most light from reaching the forest reported that mature trees infested with these floor. insects on one of Palmyra’s larger islets Pisonia grandis stands throughout their (Eastern) had lost >50% of their leaves. range are disappearing quickly because of Nest loss of seabirds using P. grandis for anthropogenic habitat destruction and breeding purposes in the infested zones was human-induced infestations by nonnative in- described in the report as an indirect effect sects (Mueller-Dombois and Fosberg 1998, of the scale infestation due to weakened Figure 4. (A) Healthy Pisonia grandis, and (B) Pisonia grandis infested with Pulvinaria urbicola (photos by A.T.H. in June 2003). Palmyra Arthropod Invasions . Handler et al. 493

Figure 5. Extent of vegetated ground area covered by Pisonia grandis on Palmyra Atoll in 2002 and 2005. In 2002, P. grandis covered approximately 12% of vegetated land area (27.3 ha). The percentage was approximately 8% in 2005 (18.2 ha). Data and figure are courtesy of Alex Wegmann. branches (Depkin 2002). Higher rates of P. Reef of , green scales tended by Ph. grandis deadfall were also noted in infested megacephala have locally extirpated mature P. stands, and areas that had been fully shaded grandis stands, leading to dramatic shifts by these trees in 2001 were exposed to direct from closed canopy to open scrub (Olds et al. sunlight 1 yr later (Depkin 2002). 1996, Smith and Papacek 2001, Kay et al. Pulvinaria urbicola is a widespread pest of 2003). Pulvinaria urbicola also has been linked solanaceous crops that has been implicated in to poor health and dieback of P. grandis trees the poor health and dieback of P. grandis on in American ( J. Burgett, stands throughout the Indo-Pacific region. pers. comm.). In the , stress caused by Pu. urbicola Because there have been very few inverte- scales tended by the long-legged ant, Anoplo- brate assessments for Palmyra, the local his- lepis gracilipes (F. Smith), caused defoliation tory of this ant-scale association is not well and death of mature trees (Hill et al. 2003). known. However, ants have been in Palmyra On multiple islands on the Great Barrier for at least a century. Tetramorium bicarina- 494 PACIFIC SCIENCE . October 2007 tum was reported as ‘‘very abundant’’ on the emies of used in biological control atoll in the early 1900s (Swezey 1914), and (Reimer et al. 1993, Jahn and Beardsley 1994, Pheidole megacephala (recorded as Pheidole sp. 2000, Helms and Vinson 2002, Lach 2003). but presumed to be Ph. megacephala) invaded Ants form facultative mutualisms with mealy- before 1948 (Krauss 1953). It is probable bugs, scales, , , and other that other introduced ant species were pres- hemipterans by protecting them from preda- ent but uncollected during those surveys. tors and parasitoids and moving them among However, because of its ecological domi- individual host plants while harvesting honey- nance in numerous habitats globally and as dew, the sugary exudate upon which the ants observed on Palmyra Atoll (e.g., Illingworth feed (Buckley 1987). Thus, both ant and scale 1927, Hoffman et al. 1999), it is unlikely that densities can reach higher population levels Ph. megacephala was overlooked if present than either species could attain in isolation, during Swezey’s survey. The scale insect Pu. with devastating effects on host plants and urbicola was not recorded in either of the pre- vegetation structure (O’Dowd et al. 2003). vious surveys on the atoll, and its negative ef- Pheidole megacephala also attended thick ag- fects on the P. grandis forest have been noted gregations of Dysmicoccus neobrevipes Beards- only recently. In light of this information, we ley (Pseudococcidae) around the fruits of propose that Pu. urbicola is a recent introduc- the rare indigenous tree Ochrosia oppositifolia tion to Palmyra Atoll. (Lam.) K. Schum. The cottony-cushion scale Introduced natural enemies can be a viable (Icerya purchasi Maskell) and an unidentified means of control for pestiferous arthropods sooty mold (Capnodiaceae) were observed on (Hajek 2004), and several parasitoid species Sceavola sericea, and sooty mold commonly used for Pulvinaria spp. control in other grew on laua‘e fern (Phymatosorus scolopendri) locations (Smith and Papacek 2001) were col- under P. grandis canopies infested with Pu. lected in our surveys. We collected the aphe- urbicola. The opaque coating of sooty molds linid wasps Coccophagus ceroplastae (Howard) on plant surfaces, encouraged by the rich and Euryischomyia flavithorax Girault & sugar content of hemipteran honeydew Dodd and the encytrid wasp Metaphycus flavus ‘‘rain’’ (Wood et al. 1988), can reduce light (Howard), which are all known to include interception and photosynthesis, thus increas- Pulvinaria spp. in their host ranges. Several ing stress on recipient plants (Fokkema et al. coccinellid species also occur on Pal- 1983). myra, including Coelophora inaqualis (Fabri- cius), notescens (Blackburn), and conclusions (Blaisdell). However, these insects were relatively uncommon, Despite the fact that the flora and fauna of wasp parasitism rates were quite low (mean Palmyra have already been overwhelmed by exit holes per insect on Eastern Islet ¼ nonnative species, globally important stands 2.1% G 0:7 S.E. [Krushelnycky and Lester, of P. grandis and dependent seabird popula- unpubl. data]), and Pu. urbicola does not tions remain. Yet the atoll remains highly appear to be under control. Smith and susceptible to new introductions of invasive Papacek (2001) advocated the release of Cryp- species. This is clearly demonstrated by the tolaemus montrouzieri Mulsant to augment the recent decline of P. grandis, which we pro- presence of the parasitic wasp C. ceroplastae in pose is caused by recent introductions of scale the Coringa-Herald National Nature Reserve insects and accelerated by ants. Hawai‘i accu- in the Coral Sea. They argued that parasitoid mulates 20–30 new foreign insect species per wasps can regulate scales at low densities, but year (Beardsley 1962), and the small of outbreaks must be controlled with augmenta- receives 12–15 new species (Schreiner tive releases of generalist predators. and Nafus 1986), many of which become im- Ants in general, and Ph. megacephala spe- portant pests to agriculture and native spe- cifically, often interfere with other natural en- cies. Even with the extremely limited human Palmyra Arthropod Invasions . Handler et al. 495 transit to Palmyra, more recent introductions sects collected from the hemipteran suborder continue. were unequivocal introduced Indeed, a new unidentified whitefly in the species. Of course, all mitigation and control family Aleyrodidae (Hemiptera) was discov- measures should be accompanied with moni- ered on the atoll in 2005, and it quickly toring measures to assess the efficacy of treat- reached nuisance levels on Scaevola species ments and to test the causal mechanisms and other native plants on Cooper Islet. The proposed in this paper. In the near term, a vi- research field station, housing, and airplane able option would be to propagate P. grandis are located on Cooper; therefore a saplings in greenhouses protected from ants majority of the current human traffic and im- and scales. Even after the destructive impacts pact on Palmyra Atoll is concentrated on that of mining and goat grazing, P. grandis is capa- particular islet. The family Aleyrodidae has ble of repopulating an area after substantial not previously been recorded from Palmyra, disturbances (Elsol 1985, Walker 1991b)if either by ourselves or in previous surveys pestiferous impacts can be minimized. How- (note that the insect referred to as a ‘‘white- ever, this task will be more difficult if a com- fly’’ by Depkin [2002] proved to be the scale plete phase shift to coconut palms or open insect Pu. urbicola, not a true whitefly). In less scrubland has already occurred (Kay et al. than 2 yr, this presumably recent introduc- 2003). tion has gone from being absent or undetect- Moreover, effective management protocols able to a major nuisance, with predicted for Palmyra Atoll should include an enforce- negative impacts on the native flora (Byrne able quarantine policy. Primary pathways of and Bellows 1991). transmission of include hitch- In response to Ph. megacephala and Pu. hiking on cargo in transit such as fresh pro- urbicola infestations in the P. grandis forests duce, plants, and packing material (Reichard of the Capricorn Cays National Park of and White 2001). These items should be in- , Australia, Kay et al. (2003) rec- spected in detail, and high-risk categories ommended strategies to fight these infesta- (i.e., live plants) should be completely prohib- tions, including (1) annual censuses of ited from transport to Palmyra. In addition, habitats to monitor infestation levels, (2) im- docking recreational craft should be scruti- plementation of a biocontrol program using nized for the possibility of infestation by ants the ladybird beetle Cryptolaemus montrouzieri or plant pathogens and pests. Because traffic and parasitoid wasps in combination with ant to and from the atoll is relatively limited, im- control measures, and (3) development and plementation of a robust quarantine policy, in implementation of an integrated revegetation which all cargo is thoroughly inspected or and weed control program. In light of this treated, should be feasible. ant-scale infestation on Palmyra and the de- clining P. grandis, we recommend the con- acknowledgments tinued implementation of control measures for both ants and scales, which are currently We thank the Bishop Museum for access to ongoing. More experimental data are urgently collections and working space. Thanks also needed to determine the individual and com- to Keith Arakaki, Joe Beatty, Ron Englund, bined effects of ants and scales on P. grandis Neal Evenhuis, Michael Gates, Tino Gon- at this location. Generally, introduction of salves, Bertram Lindsey, Gary Miller, John new biological control measures (e.g., Crypto- Noyes, Dan Polhemus, Neil Reimer, and G. laemus montrouzieri) should proceed with the Allan Samuelson for identification and verifi- utmost caution, to avoid nontarget impacts cation of insect specimens. Nathan Sanders, and other documented pitfalls (e.g., Pearson Robert Cowie, Phil Lester, and two anony- and Callaway 2003, Simberloff 2005). In the mous reviewers provided critical comments current case, nontarget impacts of specialized on the manuscript, and Stephanie Dunbar, natural enemies are less likely because all in- Paul Krushelnycky, Alex Wegmann, Zenneth 496 PACIFIC SCIENCE . October 2007

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increases. Trends Ecol. Evol. 18:561– search methods: IBOY in western 566. Pacific and . Kyoto University Press, Schreiner, I., and D. Nafus. 1986. Accidental Kyoto. introductions of insect pests to Guam, Vitousek, P. M., C. M. D’Antonio, L. L. 1945–1985. Proc. Hawaii. Entomol. Soc. Loope, and R. Westbrooks. 1999. Biolog- 27:45–72. ical invasions as global environmental Simberloff, D. 2005. The politics of assessing change. Am. Sci. 84:468–478. risk for biological invasions: The USA as a Walker, A. K., and L. L. Deitz. 1979. A re- case study. Trends Ecol. Evol. 20:216– view of entomophagous insects in the 222. . N. Z. Entomol. 7:70–82. Smith, D., and D. Papacek. 2001. Report Walker, T. A. 1991a. Pisonia islands of the on the levels of the scale insect Pulvina- Great Barrier Reef. I. The distribution, ria urbicola and its natural enemies on abundance and dispersal by seabirds of Pi- Pisonia grandis in the Coringa-Herald sonia grandis. Atoll Res. Bull. 350:1–23. National Nature Reserve 16–23 March ———. 1991b. Pisonia islands of the Great 2001. http://www.deh.gov.au/coasts/mpa/ Barrier Reef. III. Changes in the vascular coringa/insect-1/ (date accessed: 1 August flora of Lady Musgrave Island. Atoll Res. 2005). Bull. 350:31–41. Southwood, T. R. E., and P. A. Henderson. Wester, L. 1985. Checklist of the vascular 2000. Ecological methods. 3rd ed. Black- plants of the northern Line Islands. Atoll well Science Ltd., London. Res. Bull. 287:1–38. Stapp, P. 2002. Stable isotopes reveal evi- Whittaker, R. J. 1998. Island biogeography: dence of predation by ship rats on seabirds Ecology, evolution and conservation. Ox- on the Shiant Islands, Scotland. J. Appl. ford University Press, Oxford, United Ecol. 39:831–840. Kingdom. Stemmerik, J. F. 1964. Nyctaginaceae. Flora Wilson, E. O. 1996. Hawaii: A world without Melasiana Ser. 6:450–468. social insects. Bishop Mus. Occas. Pap. St. John, H. 1951. The distribution of Pisonia 45:3–7. grandis (Nyctaginaceae). Pacific Plant Wood, B. W., W. L. Tedders, and C. C. Reil- Studies No. 10. Webbia 8:225–228. ly. 1988. Sooty mold on pecan Swezey, O. H. 1914. Insects from Palmyra Is- foliage suppresses light penetration and lands. Proc. Hawaii. Entomol. Soc. 3:15– net photosynthesis. HortScience 23:851– 16. 853. Toda, M., and R. L. Kitching. 2002. Forest Zimmerman, E. C. 1941. Argentine ant ecosystems. Pages 27–109 in T. Nakashi- in Hawaii. Proc. Hawaii. Entomol. Soc. zuka and N. E. Stork, eds. Biodiversity re- 11:108. Palmyra Arthropod Invasions . Handler et al. 499

Appendix Taxonomic List of Terrestrial Arthropod Species Collected from Palmyra Atoll in Historical (Swezey 1914, Krauss 1953) and Recent (2001–2005) Collections

Collectionsc

2001– Family Taxaa Originb 1913 1948 2005 Determinerd

Order Araneae p Agelenidae Agelenidae G. sp. ? — pp— Araneidae Neoscona theisi (Walckenaer, 1841) Intr — pp DG & JB Heteropodidae Heteropoda venatoria (Linnaeus, 1767) Intr — pp JB pallidus (Blackwall, 1856) Intr — pp DG & JB Salticidae Hasarius adansoni (Audouin, 1826) Intr — pp JB Menemerus bivittatus (Dufour, 1831) Intr — pp JB Messua cf. felix (Peckham & Peckham, 1901) Intr — p JB Phintella versicolor (C. L. Koch, 1846) ? — —p *JB Plexippus paykulli (Audouin, 1826) Intr — p— Salticidae G. sp. 1 ? — ? p Salticidae G. sp. 2 ? — ?p Sandalodes sp. ? — p — Scytodidae Scytodes longipes Lucas, 1845 Intr — p — Scytodes striatipes (L. Koch, 1872) Intr — p — Tetragnathidae Tetragnatha keyserlingi Simon, 1890 Nat? — p — Coleosoma floridanum Banks, 1900 Intr — p — C. L. Koch, 1841 Intr — p — Nesticodes rufipes (Lucas, 1846) Intr — — Order p Pycnoscelus indicus (Fabricius, 1775) Intr — — p*DG Blatellidae Supella longipalpa (Fabricius, 1798) Intr — —p *DG Periplaneta americana (Linnaeus, 1758) Intr — pp— Periplaneta australasiae (Fabricius, 1775) Intr — p DG Platyzosteria soror (Brunner, 1865) Intr — — Order Coleoptera p Araecerus vieillardi (Montrouzier, 1860) Intr — — p* GAS Mauia subnotatus (Boheman, 1859) Intr — —pp* GAS Carabidae Carabidae G. sp. ? — p GAS Cerambycidae Cerambycidae G. sp. 1 ? — — p* GAS Cerambycidae G. sp. 2 ? — — p* GAS Coccinellidae G. sp. ? — — p* GAS Coelophora inaequalis (Fabricius, 1775) Intr — —p * GAS Diomus notescens (Blackburn, 1889) Intr ? p — Rhyzobius lophanthae (Blaisdell, 1892) Intr ? p — Cryptophagidae Toramus(?) sp. ? — p— Cucujidae Psammoecus insularis (Sharp, 1885) Intr — —pp* GAS Elateridae Conoderus pallipes (Eschscholtz, 1829) Intr ?p GAS Melanoxanthus melanocephalus (Fabricius, 1781) Intr ——p Dactylosternum abdominale (Fabricius, 1792) Intr — — p* GAS Nitidulidae Carpophilus humeralis (Fabricius, 1798) Intr — —pp* GAS Oedemeridae Eobia bicolor (Fairmaine, 1849) Intr — pp GAS Eobia decolor (Fairmaine, 1849) Intr —p p GAS Eobia kanack (Fairmaine, 1849) Intr — p GAS Eobia sinensis Gemminger, 1870 Intr — — p* GAS Sessinia livida (Fabricius, 1775) Intr — —p * GAS Pselaphidae Pselaphidae G. sp. ? — pp— Ptilidae Ptilidae G. sp. ? — p GAS Scarabaeidae Saprosites pygmaeus Harold, 1877 Intr — p— Scolytidae Xyleborus perforans (Wollaston, 1857) Intr — — p* GAS Staphylinidae Philonthus discoideus (Gravenhorst, 1802) Intr — — * GAS 500 PACIFIC SCIENCE . October 2007

Appendix (continued)

Collectionsc

2001– Family Taxaa Originb 1913 1948 2005 Determinerd

Order Dermaptera ppp Carcinophoridae Euborellia annulipes (Lucas, 1847) Intr WH Order Diptera p Agromyzidae Liriomyza sativae Blanchard, 1938 Intr — — p*KA Liriomyza sp. ? — —p *KA Calliphoridae Chrysomya megacephala (Fabricius, 1794) Intr — pp— Lucilia sericata (Meigen, 1826) Intr — p KA Canaceidae Canaceoides sp. ? — —p *KA Nocticanace marshallensis Wirth Nat? — p— Ceratopogonidae Ceratopogonidae G. sp. ? — —pp*KA Dasyhelea sp. ? — p KA Chironomidae Chironomidae G. sp. ? — p— Clunio sp. ? — ?pp KA Chloropidae Cadrema pallida (Loew, 1865) Intr — p KA Gaurax bicoloripes (Malloch, 1933) Intr —p — *KA Hippelates sp. ? ——p e Culicidae (Skuse, 1894) Intr — — p* GAS e Culex quinquefasciatus Say, 1823 Intr — — p* GAS Dolichopodidae Chrysosoma complicatum Becker, 1922 Intr —p — *KA Chrysosoma globiferum (Wiedemann, 1830) Intr ——pp Chrysosoma sp. ? — p KA Chrysosoma sp. nr. molestum Parent ? — —p *KA Chrysotus javanensis de Meijere, 1916 Nat? — p— Dolichopodidae G. sp. ? ? ? p KA Drosophilidae Cacoxenus perspicax (Knab, 1914) Intr — — p*KA Drosophila ananassae Doleschall, 1858 Intr — —pp*KK Discocerina mera Cresson, 1939 Intr — p KA Hecamede granifera (Thomson, 1869) Intr — p — Hostis guamensis Cresson, 1945 Intr — p — Placopsidella marquesana (Malloch, 1933) Intr — p— Placopsidella sp. ? — ? p KA Scatella stagnalis (Fallen, 1813) Intr — —p *KA Hippoboscidae Olfersia aenescens Thomson, 1869 Nat? — p— Limoniidae Limonia sp. nr. perkinsi (Grimshaw) Intr — —pp*KA Styringomyia didyma Grimshaw, 1901 Nat — pp KA Lonchaeidae Lamprolonchaea metatarsata (Kertesz, 1901) Intr — p KA Milichilidae Milichiella lacteipennis (Loew, 1865) Intr — —pp*KA Muscidae Atherigona orientalis Schiner, 1868 Intr — p KA Atherigona sp. ? — —p *KA&NE Musca domestica Linnaeus, 1758 Intr — p— Muscidae G. sp. ? — — p*KA Phoridae Chonocephalus sp. ? — —pp*KA Platystomatidae Scholastes lonchifera Hendel, 1914 Intr — p KA Sarcophagidae Parasarcophaga misera Walker Intr — — p*KA Parasarcophaga sp. ? — —p *KA Sarcophaga peregrina (Robineau-Desvoidy, 1830) Intr — p— Sarcophagidae G. sp. ? — — p*KA Sciaridae Sciaridae G. sp. ? — — p*KA Stratiomyidae Cephalochrysa maxima (Bezzi, 1928) Intr — — p*KA Syrphidae Eristalinus arvorum (Fabricius, 1787) Intr — —p *WH Simosyrphus grandicornis (Macquart, 1842) Intr — p— Syritta sp. ? — —p *KA Tethinidae Dasyrhicnoessa insularis (Aldrich, 1931) Nat? — p— Tethina sp. ? — — p*KA Ulididae Ulididae G. sp. ? — — *KA Palmyra Arthropod Invasions . Handler et al. 501

Appendix (continued)

Collectionsc

2001– Family Taxaa Originb 1913 1948 2005 Determinerd

Order Hemiptera (Heteroptera) p Cynidae Geotomus pygmaeus (Dallas, 1851) Intr —p — p*WH Gerridae Halobates micans Eschscholz, 1822 Nat — p DP Lygaeidae Lygaeidae G. sp. ? — —p * Miridae Trigonotylus brevipes Jakovlev, 1880 Nat? — p— Reduviidae Reduviidae G. sp. ? — — * Order Hemiptera (Sternorrhyncha) p Aleyrodidae Aleyrodidae G. sp. Intr —p — p* Aphididae Aphididae G. sp. ? — p Coccidae Pulvinaria urbicola (Cockerell & Parrott, 1899) Intr — —pp*BL Margarodidae Icerya purchasi Maskell, 1879 Intr — p WH Pseudococcidae Dysmicoccus brevipes (Cockerell, 1893) Intr — p— Dysmicoccus neobrevipes Beardsley, 1959 Intr — —p *GM Ferrisia virgata (Cockerell, 1893) Intr — p — Planococcus citri (Risso, 1813) Intr — — Order Hymenoptera p Aphelinidae Coccophagus ceroplastae (Howard, 1895) Intr — — p*DG&MG Euryischomyia flavithorax Girault & Dodd, 1915 Intr — —p *DG Cynipidae Kleidotoma sp. ? — p — Diapriidae Trichopria sp. ? — p— Encyrtidae Metaphycus flavus (Howard, 1881) Intr — —p *DG&JN hagenowii (Ratzeburg, 1852) Intr — p— Hemiptarsenus semialbiclavus (Girault, 1916) Intr — — p*MG appendigaster (Linnaeus, 1758) Intr — — p*WH Formicidae Cardiocondyla emeryi Forel, 1881 Intr — — p*PK Cardiocondyla minutior Forel, 1899 Intr — — p*PK f Hypoponera punctatissima (Roger), 1859 Intr — — p* PK Monomorium floricola ( Jerdon, 1851) Intr — — p*DG Paratrechina bourbonica (Forel, 1886) Intr — — p*NR g Paratrechina longicornis (Latreille, 1802) Intr — — p* Paratrechina vaga (Forel, 1901) Intr — —pp*NR Pheidole megacephala (Fabricius, 1793) Intr — p NR Tapinoma melanocephalum (Fabricius, 1793) Intr —p — p*WH Tetramorium bicarinatum (Nylander, 1847) Intr —p DG fullawayi Cockerell, 1914 Intr — p— Megachile sp. ? — — p*WH&TG Scelionidae Scelionidae G. sp. ? — — p*MG Sphecidae Sceliphron caementarium (Drury, 1770) Intr — — p*TG Sphecidae G. sp. ? — —pp*WH (Latreille, 1802) Intr — pp WH Polistes aurifer Saussure, 1853 Intr — TG Order Isopoda p Philosciidae Australophiloscia societatis (Maccagno, 1932) Nat — — *DG Order Lepidoptera p Agonoxenidae argaula Meyrick, 1921 Intr —p — Anatrachyntis incertulella (Walker, 1864) Intr ——pp Piletocera signiferalis (Wallengren, 1860) ? — pp WH Gelechiidae Stoeberhinus testaceus Butler, 1881 Intr — p WH Gracillariidae Gracillariidae G. sp. ? — —p *WH Noctuidae Chrysodeixis eriosoma (Doubleday, 1843) Intr — p— Spodoptera litura (Fabricius, 1775) Intr — —p *WH Nymphalidae Hypolimnas bolina Linnaeus, 1758 Nat? — p— Sphingidae Agrius cingulata (Fabricius, 1775) Intr — — p*WH Erechthias simulans (Butler, 1882) Intr — —p *WH Opogona sp. ? — — 502 PACIFIC SCIENCE . October 2007

Appendix (continued)

Collectionsc

2001– Family Taxaa Originb 1913 1948 2005 Determinerd

Order p Aeshnidae Anax junius (Drury, 1770) Nat — — p*DG Coenagrionidae Ischnura aurora Brauer, 1865 Nat — — p*RE Crocothemis servilia (Drury, 1770) Intr — —pp*RE Pantala flavescens (Fabricius, 1770) Nat — DG Order Orthoptera pp Acrididae Oxya japonica (Thunberg, 1824) Intr — p DG Gryllidae Cycloptilum sp. ? — p— Ornebius sp. ? — —p *WH Speonemobius tigrinus (Saussure) Nat? — p— Teleogryllus oceanicus (Le Guillou, 1841) Intr — —pp*WH Pyrgomorphidae Atractomorpha sinensis Bolivar, 1905 Intr — pp WH Tettigoniidae Conocephalus saltator (Saussure, 1859) Intr —ppp WH Phisis holdhausi Karny, 1926 Nat WH

a G. sp. indicates undetermined genus and species. b Refers to biogeographicp status on Palmyra (Intr, introduced; Nat, native; ?, cryptogenic). c A check mark ( ) indicates that a taxon was collected during a particular time period, as opposed to no collection (-) or an un- confirmed record (?). An asterisk (*) for recent collections indicates a new record for Palmyra Atoll. d Abbreviations refer to: BL, Bertram Lindsey; DG, Daniel Gruner; DP, Dan Polhemus; GAS, G. Allan Samuelson; GM, Gary Miller; JB, Joe Beatty; JN, John Noyes; KA, Keith Arakaki; KK, Ken Kaneshiro; MG, Michael Gates; NR, Neil Reimer; RE, Ron Englund; TG, Tino Gonsalves; WH, William Haines. e Collected July 2002 by C. Depkin. f Collected November 2003 by P. Krushelnycky and P. Lester. g Collected November 2003 by M. Richardson.