BIOLIEF 2011: Linking invasive species and ecosystems

Acta Oecologica 54 (2014) 1e3 Contents lists available at ScienceDirect Acta Oecologica journal homepage: www.elsevier.com/locate/actoec Foreword BIOLIEF 2011: Linking invasive species and ecosystems Invasive species impacts on ecosystem functioning (i.e., the stocks and fluxes of energy and materials and their stability over time; sensu Pacala and Kinzig, 2002) have traditionally been much less investigated than their impacts on particular species or communities (Parker et al., 1999; Sousa et al., 2011). General hypotheses, frameworks, and theories about the ecosystem-level impacts of invaders are noticeably lacking and a number of fundamental questions in the field e such as how species affect ecosystem functioning, how frequently they do so, which invasions will change ecosystem functioning, and which ecosystem functions are affected more often or more severely by invaders e remain open or were just partially answered by ecologists (Strayer, 2012). To achieve reliable general answers to these questions it becomes necessary the study of a highly diverse and unbiased array of species and ecosystems, followed by conceptual integration and synthesis across taxonomic groups and geographical regions (Py
sek et al., 2008; Jeschke et al., 2012). The BIOLIEF meeting series (Launched with BIOLIEF e World Conference on Biological Invasions and Ecosystem Functioning, Porto, Portugal; October 27 to 30, 2009) was conceived as an opportunity to present and revisit knowledge on the impacts of invasive species on the functioning of distinct ecosystems across the globe, meanwhile exploring possible avenues for progress and conceptual integration in the field (see Sousa et al., 2011). BIOLIEF 2011 e 2nd World Conference on Biological Invasion and Ecosystem Functioning (Mar del Plata, Argentina; November 21 to 24, 2011) continued the effort and success of its predecessor, congregating ca. 250 participants from 31 countries across the five continents. This Special Issue gathers together research presented or discussed at this second meeting, which in one way or another is functional to the BIOLIEF foundational goals. Both review papers and empirical case studies are included in this volume. They jointly cover a variety of invasive organisms (algae, trees, grasses, shrubs, bamboos, insects, mollusks, vertebrates) and ecosystem types (e.g., tropical and subtropical forest, Andean and subantarctic forest, temperate montane woodland, temperate and riparian grasslands, coastal dunes, streams, lakes, freshwater wetlands). This volume is also particularly rich in field studies from South America e i.e., a world region that has traditionally made a minor proportional contribution to invasive species research e and places a major focus on understudied invasive species (i.e., species that were not listed amongst the fifty most intensively studied; see Py
sek et al., 2008). The term “invasive” is used here and throughout this volume to denote species that spread from a point of introduction or origin, either colonizing new habitats or becoming overly abundant in its original range (i.e., stages III to V in the framework suggested by Colautti and 1146-609X/$ e see front matter Ó 2013 Elsevier Masson SAS. All rights reserved. http://dx.doi.org/10.1016/j.actao.2013.09.009 Mac Isaac, 2004). This definition encompasses both native and non-native species as causative of invasion processes (see Válery et al., 2008, 2013; Carey et al., 2012; Simberloff et al., 2012) and irrespective of whether their impacts could be deemed as large or small, desirable or not. The contents of this Special Issue are organized into the following three main sections based on the kinds of impacts they emphasize: (A) Invasive Species Impacts on a Particular Ecosystem Function: Invasive species impacts on the stocks and transformations of particular materials are the most frequent focus of studies in this Special Issue. Seven out of the 16 papers in this volume can be grouped under this category. Four of them evaluate different aspects of the effect of invasive plants on litter decomposition rates. Spirito et al. compared litter decomposition and soil respiration between grassland assemblages dominated by native (Paspalum quadrifarium) and non-native (Festuca arundinacea) species in the Eastern Inland Flooding Pampas, Argentina. Furey et al. compared leaf attributes and decomposability in litter of native and invasive woody species (Ligustrum lucidum, Gleditsia triacanthos and Pinus elliotti) from the Chaco Montane woodlands, Argentina. Aragón et al. compared leaf attributes and decomposition rates of litter from exotic (L. lucidum and Morus sp.) and native tree species (Cinnamomun porphyria and Cupania vernalis) in invaded (Ligustrum-dominated) and native secondary forests of Northwestern Argentina. Mincheva et al. compared litter decomposition rates and fungal communities between a native grassland and an adjacent area invaded by Japanese knotweed (Fallopia japonica) both located at a plain in the Piedmont Region, Northern Italy. All four studies indicate changes in the overall rates of litter decomposition due to plant invasions, including both increases and decreases. On another note, Montti et al. illustrates that invasive bamboos (Chusquea ramosissima and C. tenella) have higher photosynthetic capacity per unit of dry mass than trees in the semideciduous Atlantic Forest of Argentina. Higher photosynthetic capacity in bamboos contributes to their superior colonization ability in forest gaps relative to co-occurring tree saplings and may lead to altered carbon cycling and storage in the ecosystem under a scenario of increasing forest disturbance. Two other studies evaluate the effects of animals on particular ecosystem functions. Relva et al. tested the effects of a 7-year, non-native deer (Cervus elaphus and Dama dama) exclusion on litter and soil properties in an Andean-Patagonian forest, Argentina. Their results show that nutrient content in litter and soil was not affected by deer exclusion despite deer effects on the structure, composition, and abundance of understory vegetation (see Relva 2 Foreword / Acta Oecologica 54 (2014) 1e3 et al., 2010). Cooper et al. estimated changes in the amount of water hold by epiphytic tank bromeliads (Tillandsia utriculata) after invasion of the bromeliad-eating weevil (Metamasius callizona) in the Enchanted Forest Sanctuary, Florida, USA. Their calculations indicate that water hold in T. utriculata phytotelmata decreased to 3% of its baseline amount (i.e., from 17,000 to 400 L across ca. 200 ha) after just 27 months from weevil arrival. (B) Invasive Species Impacts on Other Organisms with Putative Consequences for Ecosystem Functioning: Organisms drive or modulate a variety of processes that affect the transport and transformation of material and energy in ecosystems (see Jones and Lawton, 1995; Chapin et al., 1996). Therefore, changes in the relative abundance of species and organismal functional traits due to biological invasions are expected to have reverberating impacts on ecosystem functioning (see Simberloff, 2011). Three studies in this Special Issue illustrate significant impacts of invasive species on other organisms that may affect distinct aspects of ecosystem functioning. Abreu et al. compared seedling communities under invasive (Schizolobium parahyba) and native trees at the Seasonal Semideciduous Forest, Southeastern Brazil. Decreased seedling density, basal area, and richness under invasive trees suggest important consequences for forest regeneration and productivity as long as this invasion continues. Alberio and Comparatore compared plant communities and environmental variables in areas of coastal dune grassland invaded by trees (Populus alba and Acacia longifolia) and adjacent uninvaded areas. Decreased plant cover and richness, together with larger soil particle size in invaded areas indicate that invasive trees would be profoundly altering grassland functioning. Ayup et al. compared understory vegetation structure and avian communities between forest patches dominated by invasive trees (Ligustrum lucidum) and native secondary forest patches in the Northwestern Argentinean Yungas. Decreased understory cover, together with lower bird abundance and richness in Ligustrum-invaded patches suggest changes in understory production, forest regeneration, trophic transfer to birds, and seed dispersal by frugivores that might all interact with each other leading to complex dynamics of ecosystem transformation. (C) Invasive Species Effects on Multiple Ecosystem Functions. As information about the ecosystem impacts of a particular species accumulates, it becomes evident that a single species can affect multiple functions, and often in a simultaneous way (see, for example, Eviner and Chapin, 2003; Gutiérrez and Jones, 2006). Five papers here compile information about the distinct ecosystem impacts of particular invasive species. Muñoz-Vallés et al. summarize the known and potential impacts of the invasive leguminous shrub Retama monosperma on the biotic composition and functioning of coastal dune ecosystems in Southwestern Spain. Horgan et al. review the impacts of invasive apple snails (Ampullaridae) on the functioning and services of tropical and subtropical wetlands around the globe. Reid and Torres combine field surveys and literature review to explore the known and possible ecosystem-level impacts of the invasive, mat-forming diatom Didymosphenia geminata in Patagonian rivers. Valenzuela et al. review the impacts of non-native vertebrates in the Tierra del Fuego archipelago, characterize their underlying mechanisms, and suggest priorities for management. McLaughlan et al. revisit the 10 species listed as the “worst” invaders in Europe (see Vilá et al.. 2010) and check for evidence regarding their positive and negative impacts on distinct ecosystem services. In sum, the papers in this volume illustrate the variety of issues and approaches that are currently of interest for scientists studying the ecosystem impacts of invasive species and add research from many understudied systems to our knowledge of the field. The research presented here can certainly aid in resolving open general questions on the topic when combined with study cases from the general literature. As an example of the latter and an epilogue to this volume, Gutiérrez et al. approach the general question of how invasive species affect ecosystem functioning by depicting general mechanistic linkages between invasive species and the distinct biotic and abiotic components of ecosystems. Understanding how invasive species interact with other drivers of ecosystem functioning is particularly important for ecosystem management in a context where the ecological impacts of human development are multiple and diverse in nature (Crowl et al., 2008; Strayer, 2010, 2012). This final paper aims at providing conceptual tools to link invasive species impact and spread with the dynamics of other ecosystem process drivers and ultimately, to better integrate the study of invasive species impacts into an ecosystem perspective. There is still much work to be done in responding open general questions on the impacts of invasive species on ecosystem functioning. Clearly, the field is ripe for moving from the study of impacts on particular ecosystem functions to the analysis of impacts on multiple interacting processes and drivers of ecosystem change. Such a change of research focus from the invasion to the ecosystem (see Strayer, 2012) certainly holds promise for progress in the development of general hypotheses, frameworks, and theory. We very much hope that this Special Issue can serve to propel that progress and that ecosystem-focused research on biological invasions become more represented in the literature as well as future BIOLIEF meetings. Acknowledgments We thank the authors and reviewers for their insightful contributions and their efforts in meeting with the volume preparation schedule. Support and guidance from Drs. Carlos Bernstein (Special Issue Managing Editor) and Roger Arditi (Acta Oecologica Editor-inChief) were essential for the development of this Special Issue. BIOLIEF 2011 received financial support from CONICET, Argentina (RD0173-11, Meeting Organization Grant to J. Gutiérrez). We are also indebted to Keynote Speakers, Scientific Committee members, volunteers, and registered participants at BIOLIEF 2011, who have made the meeting a huge success. References Carey, M.P., Sanderson, B.L., Barnas, K.A., Olden, J.D., 2012. Native invaders e challenges for science, management, policy, and society. Front. Ecol. Environ. 10, 373e381. Chapin III, F.S., Reynolds, H.L., D’Antonio, C.M., Eckhart, V.M., 1996. The functional role of species in terrestrial ecosystems. In: Walker, B., Steffen, W. 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sek, P., Josefsson, M., Genovesi, P., Gollasch, S., Nentwig, W., Olenin, S., Roques, A., Roy, D., Hulme, P., DAISIE partners, 2010. How well do we understand the impacts of alien species on ecosystem services? A pan-European cross-taxa assessment. Front. Ecol. Environ. 8, 135e144. 3 Jorge L. Gutiérrez* Facultad de Ciencias Exactas y Naturales & CONICET, Universidad Nacional de Mar del Plata, Mar del Plata, Argentina Visiting Scientist, Cary Institute of Ecosystem Studies, Millbrook, NY 12545, USA M. Gabriela Palomo Grupo de Investigación y Educación en Temas Ambientales (GrIETA), Mar del Plata, Argentina Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” (MACN-CONICET), Buenos Aires, Argentina Pablo D. Ribeiro Grupo de Investigación y Educación en Temas Ambientales (GrIETA), Mar del Plata, Argentina Instituto de Investigaciones Marinas y Costeras (IIMyC-CONICET), Universidad Nacional de Mar del Plata, Mar del Plata, Argentina * Corresponding author. Cervantes Saavedra 1875, Mar del Plata (B7603CNI), Argentina. Tel.: +54 2234842886. E-mail address: [email protected] (J.L. Gutiérrez). Available online 8 November 2013