Fabian M. Jaksic

Ecosystem Services for 2020

The Convention on Biological Diversitys 2020 targets are an improvement over the 2010 target, but they could be strengthened. The vast majority of nations have fallen far short of the Convention on Biological Diversitys (CBDs) 2010 target: to reduce the rate of loss of biodiversity (1, 2). This prompted the CBD to develop a new plan of action, supported by 20 “SMART” (specific, measurable, ambitious, realistic, and time-bound) targets for 2020 (3, 4). As the 10th Conference of the Parties (COP) of the CBD meets in Nagoya, Japan, to negotiate both plan and targets, it is critical that targets also be grounded in the real interests that people have in benefits provided by biodiversity. To evaluate targets on this basis, we use the ecosystem services framework developed by the Millennium Ecosystem Assessment (MA) (5). This framework balances resource conservation and use according to how societies value consumptive (e.g., food and fuel) and nonconsumptive (e.g., health and aesthetics) services provided by ecosystems.

Heterogeneous responses of small mammals to an El Niño southern oscillation event in northcentral semiarid Chile and the importance of ecological scale

A prolonged El Nino Southern Oscillation (ENSO) event during 1991–1992 with three times the normal annual 85-mm rainfall was accompanied by major changes in numbers of small mammals at a semiarid Mediterranean site in northcentral Chile. Several demographic patterns were evident. Akodon olivaceas , an omnivore, had a rapid increase in population size of more than an order of magnitude. Phyllotis darwini , a granivore-herbivore, showed somewhat delayed, smaller increases superimposed on annual oscillations. Octodon degus , an herbivore, showed a delayed response with larger increases and extended breeding in 1992–1993. Finally, Oligoryzomys longicaudatus , a granivore, experienced increases during both a dry (1990, ppt = 32 mm) and a wet year (1992). Other species such as Abrothrix longipilis, Abrocoma bennetti , and Thylamys elegans had smaller, delayed demographic responses. Reproductive rates for the first three species were higher due to the ENSO event only in O. degus males and P. darwini as a quadratic function of time. Survival rates of all four principal species were significantly greater during the 1991–1992 ENSO. Finally, average movement between captures was lower during ENSO years, suggesting behavioral changes. Explanations for these patterns include rainfall-related increases in food-resource levels ( A. olivaceus and P. darwini ), the importance of source-sink processes in vagile species from more mesic, adjacent habitats ( O. longicaudatus ), and delayed responses to extrinsic events in species with long gestation ( O. degus, A. bennetti ). The heterogeneity of species responses suggests different capabilities for small mammals to respond to an extrinsic, large-scale event, and it emphasizes the importance of long-term studies in semiarid systems.

Invaders without frontiers: cross-border invasions of exotic mammals

We address cross-border mammal invasions between Chilean and Argentine Patagonia, providing a detailed history of the introductions, subsequent spread (and spread rate when documented), and current limits of mammal invasions. The eight species involved are the following: European hare (Lepus europaeus), European rabbit (Oryctolagus cuniculus), wild boar (Sus scrofa), and red deer (Cervus elaphus) were all introduced from Europe (Austria, France, Germany, and Spain) to either or both Chilean and Argentine Patagonia. American beaver (Castor canadensis) and muskrat (Ondatra zibethicus) were introduced from Canada to Argentine Tierra del Fuego Island (shared with Chile). The American mink (Mustela vison) apparently was brought from the United States of America to both Chilean and Argentine Patagonia, independently. The native grey fox (Pseudalopex griseus) was introduced from Chilean to Argentine Tierra del Fuego. Few spread rates are available: the lowest are 10 km/yr and correspond to American beaver and American mink; intermediate rates are observed in muskrat and rather questionably, in grey fox; the highest rates (10–20 km/yr) are found among European hare and European rabbit. Because of their frequent migration, it is difficult to estimate the natural spread rate for wild boar and red deer. Not all mammal invasions in Chilean and Argentine Patagonia have been methodical advances of species; some involve an overlap of invasion fronts, with advances and retreats, and perhaps with re-invasions to different areas of either country. Because national policies with regard to introduced species may differ between countries sharing porous borders, it seems advisable to coordinate such policies in order to prevent the entry of unwelcome invaders.

Spatial distribution of soil nutrients and ephemeral plants underneath and outside the canopy of Porlieria chilensis shrubs (Zygophyllaceae) in arid coastal Chile

Soil nutrients and density and biomass of annual plants underneath and outside the canopy of Porlieria chilensis shrubs were measured at the end of the growing season in a protected arid coastal site in Chile. Levels of soil nitrogen, phosphorus and organic matter were significantly higher underneath than outside the canopies of shrubs. Almost 4 times as many plants occurred outside than underneath shrubs, but no significant differences in total aboveground biomass were found. Several species had higher densities and/or biomass outside rather than underneath shrubs, whereas others showed the oppsite trend. Species richness was lower underneath P. chilensis canopy. The spatial microdistribution of ephemeral species may be explained by differential water and nutrient requirements. Comparison of the patterns observed in our protected site versus surrounding unprotected areas supports the generalization that man, by removing shrubs and trees, has changed a previous heterogeneous spatial distribution of nutrients to a more homogenous one.

Objective recognition of guilds : testing for statistically significant species clusters

SummaryPresently, no standard protocol for objective guild recognition is consistently used by ecologists. Apart from intuitive designations of guild membership, four statistically-based protocols are currently available: those of Colwell (1977); Holmes (1979); Lawlor (1980); and Adams (1985). The first is based on nearest-neighbor variance in overlap, the second on multivariate statistics, the third on clustering techniques, and the fourth on psychometric analysis. We propose a fifth approach, first developed by Strauss (1982) for purposes other than guild recognition. We advocate the use of bootstrap procedures to resample any given empirical matrix of consumers by resources, within constraints set by either of four different randomization algorithms. Subsequently, pseudovalues of similarity in resource use between the consumers are computed and their frequency distribution is displayed in a histogram. The overlap pseudovalue that exceeds percentile 95 may be considered statistically significant and chosen as the cutoff point that identifies significant species clusters (guilds) in the original (empirical) similarity matrix. We exemplify use of this approach with the food-niche matrix obtained for a predatory assemblage in California, and discuss its implications for the general analysis of guild structure.

Vertebrate invaders and their ecological impacts in Chile

The South American country of Chile has been subjected to relatively few invasions in historic times. In comparison to the ca 610 vertebrate species found in continental Chile, only 24 species (3.9%) have invaded the country. Except for two bird and two or three mammal species that expanded their range and crossed the Andean Ranges from Argentina, the remaining 20 species were all introduced, or aided, by humans. Of the 24 invader species that currently occur in Chile, 11 (46%) were first introduced in central Chile, two (8%) in the northern part of the country, nine (38%) in the southern part, and two (8%) in Juan Fernández Archipelago. For ten (42%) of those species there is no information about their effects on the native flora, vegetation, or fauna. For eight species (33%), the information regarding the effects of the invaders is anecdotal. For six species (25%), there is adequate quantitative documentation available on their effects. Of a total of seven convincingly repo rted cases, two involve positive effects (increase in the prey base for native predators) and five have negative effects, of which three are on native vegetation and the remaining two on native fauna.

Effects of small mammals and vertebrate predators on vegetation in the Chilean semiarid zone

Abstract We monitored the cover and seed bank response of shrubs, perennial herbs, and ephemeral plants to experimental exclusion of both the principal rodent herbivore, Octodon degus, and its vertebrate predators from 1989 to 1994 in a semiarid Chilean mediterranean site. Although both richness and species composition of the plant community at the study site were largely determined by abiotic factors (mainly rainfall and soil nutrients), predator and herbivore exclusion had significant effects on the relative abundance of several plant species. Experimental exclusion of herbivores was associated with increased cover of some shrubs and a perennial grass, and decreased cover and seed densities of several ephemerals, especially those exotic or restricted to areas underneath shrubs. Herbivores apparently reduced shrubs through browsing and indirectly affected herb cover and seed densities by opening up areas under shrubs and/or modifying physical and chemical conditions of the soil. Plant responses to predator exclusion were less clear. Nevertheless, higher cover of some shrubs and ephemerals in the presence of predators suggests tritrophic effects through changes in small mammal densities and/or foraging behavior.

Extreme climatic events change the dynamics and invasibility of semi‐arid annual plant communities

Extreme climatic events represent disturbances that change the availability of resources. We studied their effects on annual plant assemblages in a semi-arid ecosystem in north-central Chile. We analysed 130 years of precipitation data using generalised extreme-value distribution to determine extreme events, and multivariate techniques to analyse 20 years of plant cover data of 34 native and 11 exotic species. Extreme drought resets the dynamics of the system and renders it susceptible to invasion. On the other hand, by favouring native annuals, moderately wet events change species composition and allow the community to be resilient to extreme drought. The probability of extreme drought has doubled over the last 50 years. Therefore, investigations on the interaction of climate change and biological invasions are relevant to determine the potential for future effects on the dynamics of semi-arid annual plant communities.

Ecosystem services, targets, and indicators for the conservation and sustainable use of biodiversity

After the collective failure to achieve the Convention on Biological Diversitys (CBDs) 2010 target to substantially reduce biodiversity losses, the CBD adopted a plan composed of five strategic goals and 20 “SMART” (Specific, Measurable, Ambitious, Realistic, and Time-bound) targets, to be achieved by 2020. Here, an interdisciplinary group of scientists from DIVERSITAS – an international program that focuses on biodiversity science – evaluates these targets and considers the implications of an ecosystem-services-based approach for their implementation. We describe the functional differences between the targets corresponding to distinct strategic goals and identify the interdependency between targets. We then discuss the implications for supporting research and target indicators, and make several specific suggestions for target implementation.

Exotic plant invasions to the mediterranean region of Chile: causes, history and impacts

Revisamos la literatura sobre patrones, causas, procesos e impactos de las plantas exoticas, principalmente en la region mediterranea de Chile, considerando tres factores determinantes del proceso de invasion: (a) Disponibilidad de propagulos de las especies exoticas, (b) atributos de las comunidades locales en las cuales las especies exoticas se establecen y a partir de las cuales eventualmente se expanden, y (c) atributos de las especies exoticas que facilitan o restringen su expansion a nuevos sitios. Con relacion a la disponibilidad de propagulos, el matorral de Chile central presenta las comunidades con la mayor incidencia de hierbas naturalizadas, seguido por el bosque esclerofilo y el espinal de la Cordillera de la Costa. En contraste, las comunidades al norte de Chile central tienen menores numeros y proporciones de hierbas naturalizadas en sus bancos de semilla. La disponibilidad y persistencia de hierbas naturalizadas no difiere entre la vegetacion emergida y el banco de semillas. En cuanto a los atributos de las comunidades locales, asociadas al establecimiento y expansion de las especies exoticas, tanto el regimen de pastoreo como el uso de la tierra emergen como los factores mas prominentes en hacerlas susceptibles a la invasion por exoticas. La evidencia sobre el efecto del regimen de incendios es contradictoria y la riqueza de especies nativas tampoco aparece como un factor importante. Con relacion a la atributos de las especies exoticas, los resultados sugieren que las anuales naturalizadas germinan dentro de un amplio rango de temperaturas, que son altamente resistentes a las condiciones frias y secas, y que muestran un cierto grado de dormancia fisiologica. Ademas, las anuales naturalizadas son altamente tolerantes a los suelos pobres, y generalmente intolerantes a la sombra. Estos atributos generales han sido determinantes en el proceso de invasion de la region mediterranea de Chile. Los datos historicos indican que un numero importante de especies exoticas fueron introducidas intencionalmente, y que su expansion es incontrolada. Se ha demostrado que la fecha de arribo de las especies exoticas es de gran relevancia para entender su actual dispersion en Chile, independientemente de su origen biogeografico. Las especies exoticas pueden causar grandes perturbaciones de procesos y funciones ecosistemicas en Chile, tal como lo ejemplifican las plantaciones de arboles exoticos, que han alterado la quimica del suelo, el ciclaje de nutrientes, el ciclo del agua, la hidrologia, el microclima, y la frecuencia e intensidad de incendios