Fabio A. Labra

Predicting insect pest status under climate change scenarios: combining experimental data and population dynamics modelling

Climate change could profoundly affect the status of agricultural insect pests. Several approaches have been used to predict how the temperature and precipitation changes could modify the abundances, distributions or status of insect pests. In this article it is demonstrated how the use of simple models, such as Ricker’s classic equation, including a mechanistic representation of the influence of exogenous forces may improve our predictive capacity of the dynamic behaviour of insect populations. Using data from classical experiments in population ecology, we evaluate how temperature and humidity influence the density of two stored grain insect pest, Tribolium confusum and Callosobruchus chinensis, and then, using the A2 and B2 scenarios proposed by the Intergovernmental Panel on Climate Change and the previous modelling, we develop predictions over the future pest status of T. confusum along South America austral region, and specifically for eight cities in the continental Chilean territory. Tribolium confusum and C. chinensis show qualitatively different responses to the exogenous forcing of temperature and humidity, respectively. Our simulations predict a change in the equilibrium density of T. confusum from 10 to 14% under the moderate B2 scenario and 12 to 22% under the extreme A2 scenario to the period, 2071–2100. Both results imply a severe change in the pest status of this species in the southern region. This study illustrates how the use of theoretically based models may improve our predictive capacity. This approach provides an opportunity to examine the link between invasive species and climate change and how new suitable habitat may become available for species whose niche space is limited in some degree by climatic conditions. The use of different scenarios allows us to examine the sensitivity of the predictions, and to improve the communication with the general public and decision‐makers; a key aspect in integrated pest management.

Biogeographic patterns of Chilean littoral fishes

En este estudio, analizamos los patrones biogeograficos de los peces litorales chilenos, incluyendo las tendencias latitudinales en riqueza de especies de peces teleosteos y condrictios, sus rangos de distribucion, y nivel de endemismo, tanto para la costa de Chile, como para el Pacifico Suroriental. Determinamos el numero y porcentaje de taxa de peces pertenecientes a cuatro grupos segun sus afinidades biogeograficas. Esta asignacion a grupos se hizo al nivel de especie, genero y familia, tanto para teleosteos como condrictios. Con el fin de determinar la existencia de regiones biogeograficas, utilizamos analisis de conglomerados y ordenacion en conjunto con tecnicas de aleatorizacion, para los tres niveles taxonomicos estudiados. Se determino que la diversidad de peces litorales se mantiene relativamente constante a lo largo de la costa, hasta alrededor de los 40o S, disminuyendo hacia el sur. Detectamos dos regiones biogeograficas a lo largo de la costa chilena, con un quiebre entre ellas a los 40o S. Estos resultados apoyan la existencia de las provincias biogeograficas o unidades faunisticas reconocidas previamente en la literatura. Estas dos regiones biogeograficas reflejan el origen mixto de la ictiofauna litoral chilena, la que consiste de especies de peces de origen subtropical y subantartico. Aunque el porcentaje de peces endemicos a la costa chilena es bajo (18%), un alto porcentaje de las especies de teleosteos presentes en aguas chilenas es endemico al Pacifico Suroriental (44%). Procesos relacionados con fenomenos de dispersion y la historia evolutiva de los componentes de esta fauna explicarian de mejor manera los patrones de distribucion observados mas que otros factores sugeridos en la literatura. Este estudio representa un primer paso hacia una mejor comprension de la biogeografia de los peces marinos del Pacifico Suroriental

METABOLIC ECOLOGY: LINKING INDIVIDUALS TO ECOSYSTEMS

Metabolism sustains life and controls the growth, reproduction, and longevity of living entities. As Brown et al. (2003, 2004) show, the ‘‘fire of life’’ is central to our understanding of patterns and dynamics at all levels of biological organization. However simple, it took 70 years to substantiate this statement; from Kleiber’s (1932) conclusion that the mass of the organism raised to the 3⁄4 power was the best predictor of metabolism to the model of West et al. (1997, 1999) that explains this relationship as a consequence of fundamental attributes of biological networks. This work paved the way to the Metabolic Theory of Ecology (MTE) outlined by Brown et al. (2004). We think that the theory outlined by Brown and co-workers represents a breakthrough that endows ecological sciences with a fresh perspective and a quantitative theory to tackle ecological complexity, from individuals to ecosystems. However, as with any new theory in science, it can be improved and refined.

Scaling metabolic rate fluctuations

Complex ecological and economic systems show fluctuations in macroscopic quantities such as exchange rates, size of companies or populations that follow non-Gaussian tent-shaped probability distributions of growth rates with power-law decay, which suggests that fluctuations in complex systems may be governed by universal mechanisms, independent of particular details and idiosyncrasies. We propose here that metabolic rate within individual organisms may be considered as an example of an emergent property of a complex system and test the hypothesis that the probability distribution of fluctuations in the metabolic rate of individuals has a “universal” form regardless of body size or taxonomic affiliation. We examined data from 71 individuals belonging to 25 vertebrate species (birds, mammals, and lizards). We report three main results. First, for all these individuals and species, the distribution of metabolic rate fluctuations follows a tent-shaped distribution with power-law decay. Second, the standard deviation of metabolic rate fluctuations decays as a power-law function of both average metabolic rate and body mass, with exponents −0.352 and −1/4 respectively. Finally, we find that the distributions of metabolic rate fluctuations for different organisms can all be rescaled to a single parent distribution, supporting the existence of general principles underlying the structure and functioning of individual organisms.

Response of the epibenthic macrofaunal community to a strong upwelling-driven hypoxic event in a shallow bay of the southern Humboldt Current System.

In January 2008, most of the southern coastal zone of the Humboldt Current System was affected by an intense upwelling event. This caused an intrusion of equatorial sub-surface water into the coastal zone, generating severe hypoxic conditions (≤0.5 ml O(2) l(-1)) three days after the beginning of the event. A rapid, massive die-off of marine organisms occurred in Coliumo Bay on January 3rd, affecting zooplankton, mollusks, crustaceans and fishes. Normal oxygen concentrations were observed on January 10th, seven days after the hypoxic event. Here we analyze the response of the epibenthic macrofauna community using data spanning three years of sampling which encompass the short-term hypoxic disturbance in the bay. We found that (i) strong changes in total density, total biomass, and diversity occurred immediately after the hypoxic event, negatively affecting crustaceans and fishes, while gastropods were favored, (ii) initial changes were reverted over a period of three months, (iii) on an inter-annual time scale, species richness and diversity decreased following the hypoxic event. Total density increased strongly, but total biomass showed no clear inter-annual trend. These results show that, while initial recovery from hypoxia was fast, over longer time scales the community exhibited a shift to an alternative structure dominated principally by Nassariid scavenger species.

DNA barcoding of marine polychaetes species of southern Patagonian fjords

Accurate species identification remains a basic first step in any study of biodiversity, particularly for global changes and their consequences. Thus, there is a pressing need for taxonomic expertise in a broad range of taxa. DNA barcoding has proved to be a powerful alternative method to traditional morphological approaches, allowing to complement identification techniques for living organisms. In this study, we assess intraspecific and interspecific genetic divergence among marine polychaetes from Patagonian fjords of southern Chile, using mitochondrial Cytochrome c Oxidase Subunit I (COI) gene. Our results showed that a total of 13 polychaetes species identified in this study exhibited high levels of interspecific variation among 31 analyzed sequences. Mean pairwise sequence distances comparisons based on K2P within species ranged from 0.2 to 0.4%. In contrast, interspecific comparisons were much higher and ranged between 18 to 47%, with the exception of the congeneric species Asychis chilensis and Asychis amphiglypta that showed high levels of genetic similarities and absence of reciprocal monophyly. This study presents the first information on DNA barcoding for polychaetes species in the southern Chile, and it establishes the effectiveness of DNA barcoding for identification of marine polychaetes species from Patagonian Fjords, thus making it available to a much broader range of scientists.

Scaling Biodiversity: Biodiversity power laws

The last ten years have been marked by important discoveries and scientificadvances in our understanding of biodiversity. The emergence of new fields,such as bioinformatics, ecoinformatics, and computational ecology (Helly et al.,1995; Spengler, 2000; Green et al., 2005) has brought about an informationalrevolution by making available massive data sets on the composition, distribu-tion and abundance of biodiversity from local to global scales and from genesto ecosystems. This has in turn changed biodiversity sciences, expanding thescale of analysis of ecological systems wherein biodiversity resides. Whilethe 1970s and 1980s were marked by studies at local scales, the 1990s weremarked by gaining access to regional, continental and global scale analyses.In parallel, and in part as a consequence of the above trend, there has been ashift from approaches that emphasize the highly variable and idiosyncraticnature of ecological systems to a view that emphasizes the action of firstprinciples, natural laws and zeroth order approaches (the macroscopicapproach hereafter).The small-scale approach can be illustrated by a representative quotationfrom Diamond and Case (1986, p. x): ‘‘The answers to general ecological ques-tions are rarely universal laws, like those of physics. Instead, the answers areconditional statements such as: for a community of species with properties A

Evaluating habitat suitability for the establishment of Monochamus spp. through climate-based niche modeling.

Pine sawyer beetle species of the genus Monochamus are vectors of the nematode pest Bursaphelenchus xylophilus. The introduction of these species into new habitats is a constant threat for those regions where the forestry industry depends on conifers, and especially on species of Pinus. To obtain information about the potential risk of establishment of these insects in Chile, we performed climate-based niche modeling using data for five North American and four Eurasian Monochamus species using a Maxent approach. The most important variables that account for current distribution of these species are total annual precipitation and annual and seasonal average temperatures, with some differences between North American and Eurasian species. Projections of potential geographic distribution in Chile show that all species could occupy at least 37% of the area between 30° and 53°S, where industrial plantations of P. radiata are concentrated. Our results indicated that Chile seems more suitable for Eurasian than for North American species.

Combining environmental suitability and population abundances to evaluate the invasive potential of the tunicate Ciona intestinalis along the temperate South American coast

The tunicate Ciona intestinalis is an opportunistic invader with high potential for causing economic losses in aquaculture centers. Recent phylogenetic and population genetic analysis support the existence of a genetic complex described as C. intestinalis with two main dominant species (sp A and B) occurring worldwide. In Chile, the species has been observed around 30°S of latitude, but no official reports exist for the presence of C. intestinalis in southern regions (above 40°S), where most of the mollusk aquaculture centers are located. Here, we used occurrences from multiple invaded regions and extensive field sampling to model and validate the environmental conditions that allow the species to persist and to find the geographic areas with the most suitable environmental conditions for the spread of C. intestinalis in the Chilean coast. By studying the potential expansion of C. intestinalis southward in the Chilean Coast, we aimed to provide valuable information that might help the development of control plans before the species becomes a significant problem, especially above 40°S. Our results highlight that, by using portions of the habitat that are apparently distinguishable, the species seem to be not only genetically distinct, but ecologically distinct as well. The two regional models fitted for sp A and for sp B showed disagreement on which sections of Chilean coastline are considered more suitable for these species. While the model for sp A identifies moderately to highly suitable areas between 30° and 40°S, the model for sp B classifies the areas around 45°S as the most appropriate. Data from field sampling show a positive linear relationship between density of C. intestinalis and the index of suitability for sp A in aquaculture centers. Understanding the relation of the distinct species with the surrounding environment provided valuable insights about probable routes of dispersion in Chile, especially into those areas considered suitable for aquaculture activities but where the species has not yet been recorded. We discuss the implications of our findings as a useful tool to anticipate the invasion of such harmful invasive species with regard to the most relevant environmental variables.

Recovery of black-necked swans, macrophytes and water quality in a Ramsar wetland of southern Chile: Assessing resilience following sudden anthropogenic disturbances

In 2004 migration and mortality for unknown reasons of the herbivorous Black necked swan (Cygnus melancorhyphus (Molina, 1782)) occurred within the Río Cruces wetland (southern Chile), a Ramsar Site and nature sanctuary. Before 2004, this wetland hosted the largest breeding population of this water bird in the Neotropic Realm. The concurrent decrease in the spatial occurrence of the aquatic plant Egeria densa Planch. 1849 - the main food source of swans - was proposed as a cause for swan migration and mortality. Additionally, post-mortem analyses carried out on swans during 2004 showed diminished body weight, high iron loads and histopathological abnormalities in their livers, suggesting iron storage disease. Various hypotheses were postulated to describe those changes; the most plausible related to variations in water quality after a pulp mill located upstream the wetland started to operate in February 2004. Those changes cascaded throughout the stands of E. densa whose remnants had high iron contents in their tissues. Here we present results of a long-term monitoring program of the wetland components, which show that swan population abundance, body weights and histological liver conditions recovered to pre-disturbance levels in 2012. The recovery of E. densa and iron content in plants throughout the wetland, also returned to pre-disturbance levels in the same 8-year time period. These results show the temporal scale over which resilience and natural restoring processes occur in wetland ecosystems of temperate regions such as southern Chile.