Editorial

Earthworms as Invasive Species in Latin America — the 2nd LatinAmerican Meeting on Oligochaeta (Earthworm) Ecology

and Taxonomy

GRIZELLE GONZÁLEZ

International Institute of Tropical Forestry USDA Forest Service Río Piedras, PR. 00926-1119 ggonzalez@fs.fed.us

“A fact is a simple statement that everyone believes. It is innocent, unless found guilty. A hypothesis is anovel suggestion that no one wants to believe. It is guilty, until found effective.”—Edward Teller(1908-2003)

This special issue is based on scientificcontributions presented at the 2nd LatinAmerican Symposium of Earthworm Ecol-ogy and Taxonomy (ELAETAO, for itsSpanish acronym) held in San Juan, PuertoRico November 14-18, 2005. The first ofthese symposia was organized by GeorgeG. Brown and Klaus D. Sautter and held atLondrina, Brazil from December 1-3, 2003.The objective of the first symposium was tosummarize the state of knowledge on theecology, biodiversity and distribution ofearthworms in Latin America and of theirusefulness as bio-indicators in variousnatural and agricultural ecosystems. Thepresent issue is focused on the ecology andtaxonomy of earthworms in Latin America,with the general theme of “Earthworms asinvasive species.” Symposium participantsevaluated the knowledge of earthwormecology and taxonomy in Latin Americawith particular emphasis on the relativeimportance of exotic vs. native earthwormsand their effects on ecosystem processesand services. The symposium included 39invited and contributed talks and posters,two workshops, and a demonstration onvermi-composting techniques. A one-daytaxonomy course taught by Samuel Jamesimmediately followed the 2nd ELAETAO(Fig. 1).

Workshops at the symposium dealt withthe following topics: possibilities of cross-site studies and/or experiments, potential

synthesis efforts, and proposal writing andprospective funding agencies in LatinAmerica. An unprecedented result fromthe various workshop deliberations was aMemorandum of Understanding (MOU)which was signed by fifteen of the partici-pants from eleven countries agreeing to“work actively towards setting importantresearch directions for earthworm ecologyand taxonomy in the Americas and to de-fine a research agenda that would includedissemination of results and new knowl-edge” (Fig. 2). Furthermore, the MOUstates that “this knowledge would bewidely distributed and accessible to fellowresearchers and land managers for betterunderstanding and use of soil ecologicalprinciples and for soil and biological con-servation”. These goals are not trivial aslanguage barriers and financial support of-ten limit the dissemination of scientificknowledge in many Latin American coun-tries.

The publication of this special issue ofthe Caribbean Journal of Science (CJS) fur-thers those goals stated in the MOU andadds to recent literature synthesizing earth-worm invasions in Canada, the UnitedStates, Europe and Australia. Recently,Paul F. Hendrix edited a Special Issue ofthe journal Biological Invasions on thistopic (September 2006). In Latin America(as in temperate North America), the inva-sions of exotic earthworms can be generally

Caribbean Journal of Science, Vol. 42, No. 3, 281-284, 2006Copyright 2006 College of Arts and SciencesUniversity of Puerto Rico, Mayaguez

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explained by the historical dispersal of hu-mans and commerce. Most recently, ad-vances in communication technology(e.g., internet access) have facilitated thesale and export of exotic earthworms inter-nationally via e-commerce. Thus, the trans-port of living goods over the long history ofmestizaje (mixture of foreign cultures), com-bined now with ready availability of earth-worm-associated commodities (e.g., horti-cultural or vermi-composting materials)add to the challenges that scientists andmanagers must face in pursuit of the studyof the ecology and taxonomy of earth-worms in Latin American countries. Al-though not all countries in Latin Americaare covered here, this collection of papersreflects the state of our knowledge of nativeand exotic earthworms in this part of theworld.

About sixty percent of these papersexplore a wide range of issues dealingwith the diversity, community structure,and distribution of earthworms in LatinAmerica. Richardson et al. explore the bio-geography of epigeic worms in bromeliadsof Dominica and Puerto Rico. They reportthat earthworms in Dominica occurred inmore than 90% of the plants and made up alarge portion of the total invertebrate bio-mass, whereas in Puerto Rico earthwormswere less abundant. Mischis and Herrerareview the distribution of exotic earth-

worms in Argentina and confirm that dur-ing the last five decades, growers who cul-tivate earthworms for vermiculture areresponsible for the introduction of Eiseniaandrei and E. fetida into this country, as theyimported cocoons and individuals from theUSA. On the other hand, Zerbino et al. ex-plore the potential use of earthworms asbiological indicators in the development ofsustainable ecosystems. Grosso et al., Feijooet al., Zou et al., Sánchez et al., and Huertaet al. provide evidence of a large incidenceof exotic earthworm species in agro-ecosystems of Uruguay, Colombia, PuertoRico, Costa Rica and Mexico, respectively.Yet interestingly, there are also reports ofnative earthworms thriving under inten-sive management, as observed in an inun-dated rice field in Uruguay (Grosso et al.),in degraded pastures and row crops in Bra-zil (Nunes et al.), dominating more than70% of the total density of earthworms insugarcane and banana fields in Mexico(Huerta et al.), or present in combinationwith exotic worms in a Colombian pastureabove 2000 m (Feijoo et al.). Nevertheless,results from Zou et al. support the findingsfrom other studies that converting tropicalforests to pasture lead to the reduction ofparticular functional groups of earthwormsin these soils. In this regard Huang et al.propose that biotic factors, such as competi-tive exclusion of native earthworms by

FIG. 1. Participants to the taxonomy course of the 2nd Latin-American Symposium of Earthworm Ecology andTaxonomy held in San Juan, Puerto Rico. 1) María de los Angeles Sánchez-Rosa, 2) Xiaoming Zou, 3) YaniriaSánchez-de León, 4) Maria Stella Zerbino, 4) Grizelle González, 6) Yolmar B. Ríos, 7) Sandra C. Tapia-Coral, 8)Malena Sarlo, 9) Sonia Borges, 10) Esperanza Huerta Lwanga, 11) Samuel W. James, 12) Catalina C. Mischis, 13)Beto Pashanasi, 14) Tawainga Katsvairo, 15) Ching-Yu Huang, 16) George G. Brown, 17) Gabriella Jorge, 18) PaulH. Hendrix, 19) Christina M. Murphy. Not in the picture: Alexander Feijoo-Martínez, and Bruce A. Snyder.

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Fig. 1 live 4/C

FIG. 2. The Memorandum of Understanding signed by fifteen of the participants of the 2nd Latin-AmericanSymposium of Earthworm Ecology and Taxonomy (ELAETAO) held in San Juan, Puerto Rico during November14-18, 2005.

EDITORIAL 283

exotic earthworms, may have substan-tially retard their re-colonization and/orcause the disappearance of native earth-worm populations in disturbed areas. Lugoet al. and Borges et al. report the coexist-ence of native and exotic earthworms indisturbed forests under secondary plantsuccession.

Some of the papers in this special issueinvestigate the ecology of native and exoticearthworms, particularly as they influenceecosystem processes and services. For ex-ample, using mesocosms in the PeruvianAmazon, Tapia et al. show that Pontoscolexcorethrurus can increase soil nitrogen min-eralization. But as Brown et al. well pointout, little is known of the effects of mostexotic earthworm species on plants, soilproperties and processes, or on other nativespecies and conversely, as Sarlo’s studyshows, native tree species can favor earth-worm biomass over other tree species. Newtools using fluorescent markers for carry-ing out mark-release-recapture studies(e.g., González et al.) could enhance com-parative studies that would help us under-stand the biology, demography, selectivefeeding strategies, and resource competi-tion dynamics of native and exotic earth-worms.

I believe the information contained inthis special issue will be valuable as weconsider management and policy optionsto earthworm invasions and introductionsin Latin American countries and elsewhere.I also hope this wealth of information canmotivate a new generation of studies fo-cused on the unraveling of the mecha-nisms, effects and implications of invasive

species in terrestrial belowground ecosys-tems. Indeed, these are exciting times tostudy the patterns, mechanisms, and con-sequences of earthworms as invasive spe-cies in the Americas!

Acknowledgement.—I thank the State andPrivate Forestry Program, International Co-operation, and the Research and Develop-ment Units of the International Institute ofTropical Forestry (IITF) of the U.S. Depart-ment of Agriculture.—Forest Service(USDA – FS) in Puerto Rico, and the PuertoRico Conservation Foundation for support-ing this project. I also thank the Interna-tional Cooperation Program Office ofUSDA – FS in Washington, D.C. The sym-posium and this publication would nothave been possible without the financialsupport of the USDA – FS Agreements 05-DG 11120101011 and 05-DG 11120101027 tothe Puerto Rico Conservation Foundation.Additional support was provided by grantDEB-0218039 from the U.S. National Sci-ence Foundation to the Institute of TropicalEcosystem Studies, University of PuertoRico (UPR), and USDA – FS, IITF as part ofthe Long-Term Ecological Research Pro-gram in the Luquillo Experimental Forest.The work was done in collaboration withUPR. Drs. Inés Sastre-De Jesús, Ariel E.Lugo, William A. Gould and Paul F. Hen-drix kindly commented on earlier versionsof this editorial. Finally, I owe thanks to thecontributors to this special issue and themany open and anonymous reviewerswhose comments greatly improved earlierversions of the manuscripts. Thanks to Dr.Inés Sastre-De Jesús, former Editor of theCJS for allowing us to publish here.

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