Abstract
Invasive species may have negative impacts on many narrow range endemics and species restricted to oceanic islands. Predicting recent impacts of invasive species on long-lived trees is difficult because the presence of adult plants may mask population changes. We examined the impact of introduced black rats (Rattus rattus) on two palm species restricted to cloud forests and endemic to Lord Howe Island, a small oceanic island in the southern Pacific. We combined estimates of the standing size distribution of these palms with the proximal impacts of rats on fruit survival in areas baited to control rats and in unbaited areas. The size distribution of palms with trunks was comparable across baited and unbaited sites. Small juvenile palms lacking a trunk (<50 cm tall) were abundant in baited areas, but rare in unbaited sites for Lepidorrhachis mooreana, and rare or absent in 3 out of 4 unbaited Hedyscepe canterburyana sites. All ripe fruits were lost to rats in the small fruited L. mooreana. Fruit removal was widespread but less (20–54%) in H. canterburyana. Both palms showed evidence of a reduced capacity to maintain a juvenile bank of palms through regular recruitment as a consequence of over 90 years of rat impact. This will limit the ability of these species to take advantage of episodic canopy gaps. Baiting for rat control reduced fruit losses and resulted in the re-establishment of a juvenile palm bank. Conservation of both endemic palms necessitates control (or eradication) of rat populations on the unique cloud forest summits of the island.
Similar content being viewed by others
References
Allen RB, Lee WG, Rance BD (1994) Regeneration in indigenous forest after eradication of Norway rats, Breaksea Island, New Zealand. NZ J Bot 32:429–439
Anderson A (2003) Investigating early settlement on Lord Howe Island. Aust Archaeol 57:98–102
Angel A, Wanless RM, Cooper J (2009) Review of impacts of the introduced house mouse on islands in the Southern Ocean: are mice equivalent to rats? Biol Invas 11:1743–1754
Athens JS (2009) Rattus exulans and the catastrophic disappearance of Hawai’i’s native lowland forest. Biol Invas 11:1489–1501
Auld TD, Hutton I (2004) Conservation issues for the vascular flora of Lord Howe Island. Cunninghamia 8:490–500
Baker WJ, Hutton I (2006) Lepidorrhachis. Palms 50:33–38
Billing J (2000) The control of introduced Rattus rattus L. on Lord Howe Island. II. The status of warfarin resistance in rats and mice. Wildl Res 27:659–661
Billing J, Harden B (2000) Control of introduced Rattus rattus L. on Lord Howe Island. I. The response of mouse populations to warfarin bait used to control rats. Wildl Res 27:655–658
Blackburn TM, Cassey P, Duncan RP, Evans KL, Gaston KJ (2004) Avian extinction and mammalian introductions on oceanic islands. Science 305:1955–1958
Campbell DJ, Atkinson IAE (2002) Depression of tree recruitment by the Pacific rat (Rattus exulans Peale) on New Zealand’s northern offshore islands. Biol Conserv 107:19–35
Cheke AS (2006) Establishing extinction dates—the curious case of the Dodo Raphus cucullatus and the Red Hen Aphanapteryx bonasia. Ibis 148:155–158
Coote T, Loeve E (2003) From 61 species to five: endemic tree snails of the Society Islands fall prey to an ill-judged biological control programme. Oryx 37:91–96
Crisp MD, Lange RT (1976) Age structure, distribution and survival under grazing of the arid-zone shrub Acacia burkittii. Oikos 27:86–92
Davey A (1986) Plan of management. Lord Howe Island permanent park preserve. NSW National Parks and Wildlife Service, Sydney
Delgado García JD (2002) Interaction between introduced rats and a frugivore bird–plant system in a relict island forest. J Nat Hist 36:1247–1258
Department of Environment and Climate Change NSW (2007) Lord Howe Island Biodiversity Management Plan. Department of Environment and Climate Change (NSW), Sydney
Dransfield J, Uhl NW, Asmussen CB, Baker WJ, Harley MM, Lewis CE (2008) Genera Palmarum. The evolution and classification of palms. Kew Publishing, UK
Duncan RP, Young JR (2000) Determinants of plant extinction and rarity 145 years after European settlement of Auckland, New Zealand. Ecology 81:3048–3061
Enright NJ (1985) Age, reproduction and biomass allocation in Rhopalostylis sapida (Nikau palm). Aust J Ecol 10:461–467
Enright NJ, Watson AD (1992) Population dynamics of the Nikau palm, Rhopalostylis sapida (Wendl et Drude), in a temperate forest remnant near Auckland, New Zealand. NZ J Bot 30:29–43
Fox GA (2001) Failure-time analysis: Studying times to events and rates at which events occur. In: Scheiner SM, Gurevitch J (eds) Design and analysis of ecological experiments. Oxford University Press, Oxford, pp 235–266
Harris R, Cassis G, Auld TD, Hutton I (2005) Patterns in floristic composition and structure in the mossy cloud forest of Mt Gower summit, Lord Howe Island. Pac Conserv Biol 11:246–256
Hindwood KA (1940) The birds of Lord Howe Island. Emu 40:1–86
Holdaway RN (1989) New Zealand’s pre-human avifauna and its vulnerability. NZ J Ecol 12:11–25
Hunt TL (2007) Rethinking Easter Island’s ecological catastrophe. J Archaeol Sci 34:485–502
Hutton I (1986) Lord Howe Island. Conservation Press, Canberra, ACT
Hutton I, Parkes JP, Sinclair ARE (2007) Reassembling island ecosystems: the case of Lord Howe Island. Anim Cons 10:22–29
Janzen DH (1986) Blurry catastrophes. Oikos 47:1–2
Lonsdale WM (1999) Global patterns of plant invasions and the concept of invasibility. Ecology 80:1522–1536
Mack MC, D’Antonio CM (1998) Impacts of biological invasions on disturbance regimes. Trends Ecol Evol 13:195–198
McAllan IAW, Curtis BR, Hutton I, Cooper RM (2004) The birds of Lord Howe Island Group: a review of records. Aust Field Ornithologist 21(Suppl):1–82
McDougall I, Embleton BJ, Stone DB (1981) Origin and evolution of Lord Howe Island, southwest Pacific Ocean. J Geol Soc Aust 28:155–176
Meyer JY, Butaud JF (2009) The impacts of rats on the endangered native flora of French Polynesia (Pacific Islands): drivers of plant extinction or coup de grâce species? Biol Invas 11:1569–1585
Moore HE (1966) Palm hunting around the world. IV Lord Howe Island. Principes 10:13–21
Mueller-Dumbois D, Fosberg FR (1998) Vegetation of the tropical Pacific islands. Springer, New York
Mulder CPH, Grant-Hoffman MN, Towns DR, Bellingham PJ, Wardle DA, Durrett MS, Fukami T, Bonner KI (2009) Direct and indirect effects of rats: does rat eradication restore ecosystem functioning of New Zealand seabird islands? Biol Invas 11:1671–1688
Ogden J (1985) An introduction to plant demography with special reference to New Zealand trees. NZ J Bot 23:751–772
Pickard J (1980) The palm seed industry of Lord Howe Island. Principes 24:3–13
Pickard J (1983a) Vegetation of Lord Howe Island. Cunninghamia 1:133–266
Pickard J (1983b) Rare or threatened vascular plants of Lord Howe Island. Biol Conserv 27:125–139
Prebble M, Dowe JL (2008) The late Quaternary decline and extinction of palms on oceanic Pacific islands. Quatern Sci Rev 27:2546–2567
Priddel D, Carlile N, Humphrey M, Fellenberg S, Hiscox D (2003) Rediscovery of the ‘extinct’ Lord Howe Island stick-insect (Dryococelus australis (Montrouzier)) (Phasmatodea) and recommendations for its conservation. Biodiversity Conserv 12:1391–1403
Sakai AK, Wagner WL, Mehrhoff LA (2002) Patterns of endangerment in the Hawaiian flora. Syst Biol 51:276–302
Sarukhán J (1980) Demographic problems in tropical systems. In: Solbrig O (ed) Demography and evolution in plant populations. Blackwell Scientific Publications, Oxford, pp 161–188
Silvertown JW (1982) Introduction to plant population ecology. Longman Press, London
Soule ME (1990) The onslaught of alien species, and other challenges in the coming decades. Conserv Biol 4:233–239
Tomlinson PB (1979) Systematics and ecology of the Palmae. Annu Rev Ecol Syst 10:85–107
Towns DR (2009) Eradications as reverse invasions: lessons from Pacific rat (Rattus exulans) removals on New Zealand islands. Biol Invas 11:1719–1733
Towns DR, Atkinson IAE, Daugherty CH (2006) Have the harmful effects of introduced rats on islands been exaggerated? Biol Invas 8:863–891
Traveset A, Nogales M, Alcover JA, Delgado JD, López-Darias M, Godoy D, Igual JM, Bover P (2009) A review on the effects of alien rodents in the Balearic (Western Mediterranean Sea) and Canary Islands (Eastern Atlantic Ocean). Biol Invas 11:1653–1670
Trevino HS, Skibiel AL, Karels TJ, Dobson FS (2007) Threats to avifauna on oceanic islands. Conserv Biol 21:125–132
Underwood AJ (1997) Experiments in ecology. Their logical design and interpretation using analysis of variance. Cambridge University Press, Cambridge
Walker BH, Stone L, Hendersen L, Verede M (1986) Size structure analysis of the dominant trees in a South African savannah. S Afr J Bot 52:397–402
Wiles GJ, Bart J, Beck RE, Aguon CF (2003) Impacts of the brown tree snake: patterns of decline and species persistence in Guam’s avifauna. Conserv Biol 17:1350–1360
Zar JH (1974) Biostatistical analysis. Prentice-Hall Inc, NJ
Acknowledgments
We thank the Lord Howe Island Board for permission to carry out this study and for support in the use of a research facility for TA, MO and AD. William Baker made helpful comments on the manuscript.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Auld, T.D., Hutton, I., Ooi, M.K.J. et al. Disruption of recruitment in two endemic palms on Lord Howe Island by invasive rats. Biol Invasions 12, 3351–3361 (2010). https://doi.org/10.1007/s10530-010-9728-5
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10530-010-9728-5