Abstract
Intact tropical rainforests on continents and continental islands are considered to be relatively resistant to invasions by introduced plant species, but fragmentation and degradation may render them susceptible, especially to species from predominantly shade-tolerant families with centres of diversity in the tropics, such as palms. We investigated the seedling establishment patterns of the most common exotic palm species in Singapore’s secondary forest patches, the Macarthur palm (Ptychosperma macarthurii), in relation to landscape-level planting intensity, abiotic conditions, and recipient community composition. We first used conditional inference forests to narrow down the set of possible explanatory variables, followed by fitting generalised linear models with the forest patch and individual plots as random intercepts, to account for the nesting of plots within patches and overdispersion, respectively. The number of cultivated adults in the vicinity was not an important variable. Instead, leaf litter was the most important predictor of seedling density. Thick leaf litter in the disturbed and younger secondary forest matrix that surrounds old growth forest patches may therefore serve as a buffer against invasions, especially by small-seeded exotics. However, if adults of exotic species are allowed to establish unchecked, for example along forest trails that lead into the interior of the forested landscape, the seed rain may eventually reach old growth forest where leaf litter is typically thin. Further studies are required to determine if second-generation adults within invaded habitats contribute disproportionately more to propagule pressure than first-generation cultivated plants outside the invaded habitat.
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References
Blackburn TM, Pyšek P, Bacher S, Carlton JT, Duncan RP, Jarošik V, Wilson JRU, Richardson DM (2011) A proposed unified framework for biological invasions. Trends Ecol Evol 26:333–339
Bolker BM, Brooks ME, Clark CJ, Geange SW, Poulsen JR, Stevens MHH, White J-SS (2008) Generalized linear mixed models: a practical guide for ecology and evolution. Trends Ecol Evol 24:127–135
Bray RH, Kurtz LT (1945) Determination of total, organic and available forms of phosphorus in soils. Soil Sci 59:39–45
Burnham KP, Anderson DR (2002) Model selection and multimodel inference: a practical information-theoretic approach. Springer, New York
Cadotte MW, Murray BR, Lovett-Doust J (2006) Ecological patterns and biological invasions: using regional species inventories in macroecology. Biol Invasions 8:809–821
Catford JA, Jansson R, Nilsson C (2009) Reducing redundancy in invasion ecology by integrating hypotheses into a single theoretical framework. Divers Distrib 15:22–40
Chong KY, Tan HTW, Corlett RT (2011) A summary of the total vascular plant flora of Singapore. Gard Bull Singap 63:197–204
Choong MF, Lucas PW, Ong JSY, Pereira B, Tan HTW, Turner IM (1992) Leaf fracture toughness and sclerophylly: their correlations and ecological implications. New Phytol 121:597–610
Colautti RI, Grigorovich IA, MacIsaac HJ (2006) Propagule pressure: a null model for biological invasions. Biol Invasions 8:1023–1037
Cummings JA, Parker IM, Gilbert GS (2012) Allelopathy: a tool for weed management in forest restoration. Plant Ecol 213:1975–1989
Dupuy JM, Chazdon RL (2008) Interacting effects of canopy gap, understory vegetation and leaf litter on tree seedling recruitment and composition in tropical secondary forests. Forest Ecol Manag 255:3716–3725
Elston DA, Moss R, Boulinier T, Arrowsmith C, Lambin X (2000) Analysis of aggregation, a worked example: numbers of ticks on red grouse chicks. Parasitology 122:563–569
Fensham RJ, Silcock JL, Dwyer JM (2011) Plant species richness responses to grazing protection and degradation history in a low productivity landscape. J Veg Sci 22:997–1008
Fine PVA (2002) The invisibility of tropical forests by exotic plants. J Trop Ecol 18:687–705
Gee GW, Bauder JW (1986) Particle-size analysis. In: Klute A (ed) Methods of soil analysis. Part 1: physical and mineralogical methods. Soil Science Society of America, Madison, WI, pp 383–411
Giam X, Ng TH, Lok AFSL, Ng HH (2011) Local geographic range predicts freshwater fish extinctions in Singapore. J Appl Ecol 48:356–363
Goldsmith GR, Comita LS, Chua SC (2011) Evidence for arrested succession within a tropical forest fragment in Singapore. J Trop Ecol 27:323–326
Helmke PA, Sparks DL (1996) Lithium, sodium, potassium, rubidium and cesium. In: Sparks DL (ed) Methods of soil analysis. Part 3: chemical methods. Soil Science Society of America, Madison, WI, pp 551–574
Hothorn T, Hornik K, Zeileis A (2006) Unbiased recursive partitioning: a conditional inference framework. J Comput Graph Stat 15:651–674
Inderjit, Wardle DA, Karban R, Callaway RM (2011) The ecosystem and evolutionary contexts of allelopathy. Trends Ecol Evol 26:655–662
Kjeldahl J (1883) Neue methode zur bestimmung des stickstoffs in organischen kompern. Z Anal Chem 22:366–382
Laurance WF, Lovejoy TE, Vasconcelos HL, Bruna EM, Didham RK, Stouffer PC, Gascon C, Bierregaard RO, Laurance SG, Sampaio E (2002) Ecosystem decay of Amazonian forest fragments: a 22-year investigation. Conserv Biol 16:605–618
Lockwood JL, Cassey P, Blackburn TM (2009) The more you introduce the more you get: the role of colonization pressure and propagule pressue in invasion ecology. Divers Distrib 15:904–910
Lok AFSL, Chong KY, Tan K-X, Tan HTW (2010) A checklist of the spontaneous exotic vascular plant flora of Singapore. Cosmos 6:57–83
Mazerolle MJ (2010) AICcmodavg: model selection and multimodel inference based on (Q)AIC(c). R package version 1.11
McCune B, Grace JB (2002) Analysis of ecological communities. MjM Software Design, Gleneden Beach, Oregon
Menke S, Böhning-Gaese K, Schleuning M (2012) Plant-frugivore networks are less specialized and more robust at forest-farmland edges than in the interior of a tropical forest. Oikos 121:1553–1566
Metlen KL, Aschehoug ET, Callaway RM (2012) Competitive outcomes between two exotic invaders are modified by direct and indirect effects of a native conifer. Oikos doi:10.1111/j.1600-0706.2012.20792.x
Meyer J-Y, Lavergne C, Hodel DR (2008) Time bombs in gardens: invasive ornamental palms in tropical islands, with emphasis on French Polynesia (Pacific Ocean) and the Mascarenes (Indian Ocean). Palms 52:71–83
Molofsky J, Augspurger CK (1992) The effect of leaf litter on early seedling establishment in a tropical forest. Ecology 73:68–77
Murphy J, Riley HP (1962) A modified single solution method for the determination of phosphate in natural waters. Anal Chim Acta 27:31–36
Neo L, Yee ATK, Chong KY, Tan HTW (2012) The vascular plant flora of abandoned plantations in Singapore I: Clementi Forest. Nat Singap 5:275–283
Neo L, Yee ATK, Chong KY, Yeo HHT, Tan HTW (2013) The vascular plant flora of abandoned plantations in Singapore II: Punggol End Forest. Nat Singap 6:7–17
Nghiem TPL (2010) The ecology of invasive tree species in Singapore. MSc Thesis, National University of Singapore
Nuñez MA, Moretti A, Simberloff D (2011) Propagule pressure hypothesis not supported by an 80-year experiment on woody species invasion. Oikos 120:1311–1316
Oksanen J, Blanchet FG, Kindt R, Legendre P, Minchin PR, O’Hara RB, Simpson GL, Solymos P, Stevens MHH, Wagner H (2010) Vegan: community ecology package. R version 1.17-2. Available online: http://CRAN.R-project.org/package=vegan
Pacific Island Ecosystems at Risk (2006) Ptychosperma macarthurii Pacific Island Ecosystems at Risk (PIER) Plant Threats to Pacific Ecosystems. Available online: http://www.hear.org/pier/species/ptychosperma_macarthurii.htm
Paradis E, Claude J, Strimmer K (2004) APE: analyses of phylogenetics and evolution in R language. Bioinformatics 20:289–290
Pryer KM, Schuettpelz E, Wolf PG, Schneider H, Smith AR, Cranfill R (2004) Phylogeny and evolution of ferns (monilophytes) with a focus on the early leptosporangiate divergences. Am J Bot 91:1582–1598
Pyšek P, Křivánek M, Jarošik V (2009) Planting intensity, residence time, and species traits determine invasion success of alien woody species. Ecology 90:2734–2744
R Development Core Team (2009) R: a language and environment for statistical computing. R Foundation for Statistical Computing. Vienna, Australia. Available online: http://www.R-project.org
Richardson DM, Pyšek P, Carlton JT (2011) A compendium of essential concepts and terminology in invasion ecology. In: Richardson DM (ed) Fifty years of invasion ecology: the legacy of Charles Elton. Oxford. UK, Wiley-Blackwell, pp 409–420
Sayer EJ (2006) Using experimental manipulation to assess the roles of leaf litter in the functioning of forest ecosystems. Biol Rev 81:1–31
Sayer EJ, Wright SJ, Tanner EVJ, Yavitt JB, Harms KE, Powers JS, Kaspari M, Garcia MN, Turner BL (2012) Variable responses of lowland tropical forest nutrient status to fertilization and litter manipulation. Ecosystems 15:387–400
Scariot A (1999) Forest fragmentation effects on palm diversity in central Amazonia. J Ecol 87:66–76
Scarpa FM, Valio IFM (2008) Relationship between seed size and litter effects on early seedling establishment of 15 tropical tree species. J Trop Ecol 24:569–573
Schramm JW, Ehrenfeld JG (2010) Leaf litter and understory canopy shade limit the establishment, growth and reproduction of Microstegium vimineum. Biol Invas 12:3195–3204
Sim JWS, Tan HTW, Turner IM (1992) Adinandra belukar: an anthropogenic heath forest in Singapore. Vegetatio 102:125–137
Strobl C, Boulesteix A-L, Zeileis A, Hothorn T (2007) Bias in random forest variable importance measures: illustrations, sources and a solution. BMC Bioinformatics 8:25
Strobl C, Boulesteix A-L, Kneib T, Augustin T, Zeileis A (2008) Conditional variable importance for random forests. BMC Bioinformatics 9:307
Teo DHL, Tan HTW, Corlett RT, Wong CM, Lum SKY (2003) Continental rain forest fragments in Singapore resist invasion by exotic plants. J Biogeogr 30:305–310
Thuiller W, Gallien L, Boulangeat I, de Bello F, Mükenmüller T, Roquet C, Lavergne S (2010) Resolving Darwin’s naturalization conundrum: a quest for evidence. Divers Distrib 16:461–475
Warren RJ II, Bahn V, Bradford MA (2012) The interaction between propagule pressure, habitat suitability and density-dependent reproduction in species invasion. Oikos 121:874–881
Webb CO, Donoghue MJ (2004) Phylomatic: tree assembly for applied phylogenetics. Mol Ecol Notes 5:181–183
Webb CO, Ackerly DD, Kembel SW (2008) Phylocom: software for the analysis of phylogenetic community structure and trait evolution. Bioinformatics 24:2098–2100
Weir JES, Corlett RT (2007) How far do birds disperse seeds in the degraded tropical landscape of Hong Kong, China? Landscape Ecol 22:131–140
Wikström N, Savolainen V, Chase MW (2001) Evolution of the angiosperms: calibrating the family tree. P Roy Soc Lond B Biol 268:2211–2219
Yee ATK, Corlett R, Liew SC, Tan HTW (2011) The vegetation of Singapore-an updated map. Gard Bull Singap 63:205–212
Acknowledgments
We are grateful to Woo Wee Meng, Teo Siyang, and Yeo Chow Khoon for field work support, Gwee Aik Teck for plant identification, Andy Angkasa and Tan Chee Wei for preparing the voucher specimens, Serena Lee and Chua Keng Soon for access to the herbarium collections, and Tommy Tan and Ang Swee Eng for technical assistance. Permission for surveys in some sites was provided by National Parks Board, Singapore (Permit No. NP/RP10-072) and Jeremy Woon facilitated the processing of the permit. We thank Martin Nuñez and two anonymous reviewers for very helpful feedback on the manuscript.
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Yeo, H.H.T., Chong, K.Y., Yee, A.T.K. et al. Leaf litter depth as an important factor inhibiting seedling establishment of an exotic palm in tropical secondary forest patches. Biol Invasions 16, 381–392 (2014). https://doi.org/10.1007/s10530-013-0527-7
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DOI: https://doi.org/10.1007/s10530-013-0527-7