Archive for the ‘agroecosystem analysis’ Category

Invasive species and climate change: the PBDM approach

September 12, 2014 Leave a comment

Assessing the geographic distribution and abundance of invasive species is critical for developing sound management and/or eradication policies. Ecological niche modelling approaches (ENMs) that make implicit assumptions about biology and mathematics are commonly used to predict the potential distribution of invasive species based on their recorded distribution. An alternative approach is physiologically based demographic modelling (PBDM), which explicitly incorporates the mathematics and the observed biology, including trophic interactions, to predict the temporal phenology and dynamics of a species across wide geographic areas. The invasive weed, yellow starthistle (YST) (Centaurea solstitialis), and its interactions with annual grasses and herbivorous biological control agents is used to demonstrate the utility of the PBDM approach for analysing complex invasive species problems. The PBDM predicts the distribution and relative abundance of YST accurately across the western USA, and the results are used to assess the effects of temperature, rainfall, competition from grasses and the efficacy of biocontrol efforts. Such an effort could also be used to include the direct effects of rising carbon dioxide on YST biology. A bioeconomic model could be developed to show how the YST PBDM analysis can also be used to assess the biological and economic effects of climate change on YST infestation levels regionally. Finally, this chapter discusses the need for a unified system for assessing invasive species problems at the field, regional and global levels, with the goal of enhancing the development of efficacious policy and management decisions.

Gutierrez A.P., Ponti L., 2014. Assessing and managing the impact of climate change on invasive species: the PBDM approach. In: Ziska L.H., Dukes J.S., (eds.), Invasive Species and Global Climate Change. CABI Publishing, Wallingford, UK. ISBN: 978-1780641645.

Trophic interactions in the yellow starthistle PBDM system.

Analysis of invasive insects: links to climate change

September 12, 2014 Leave a comment

Climate change is expected to alter the geographic distribution and abundance of many species, to increase the invasion of new areas by exotic species and, in some cases, to lead to extinction of species. This chapter reviews some of the links between invasive insects and climate change. The effects of climate change on insect pest populations can be direct, through impacts on their physiology and behaviour, or indirect, through biotic interactions (i.e. bottom-up and top-down eff ects). Anthropogenic climate and global change is expected to be a major driver in the introduction, establishment, distribution, impact and changes in the efficacy of mitigation strategies for invasive species. To address these problems, we must be able to predict climate change impacts on species distribution and abundance. Commonly used ecological niche modelling approaches have implicit assumptions about the biology of the target species and attempt to characterize the ecological niche using aggregate weather and other factors in the area of recorded distribution. More holistic physiologically based demographic modelling approaches explicitly describe the biological and physiological responses of species to weather and the species they interact with on fine temporal and spatial scales. The geographic distribution and relative abundance of four invasive insect pests are reviewed under observed and +2°C weather scenarios across the USA and Mexico: the tropical New World screwworm, the pink bollworm, the Mediterranean fruit fly (i.e. medfly) and the olive fly. The distribution of the olive fly is examined across the Mediterranean basin to illustrate the transferability of the model to analyses of new regions and climate change scenarios.

Gutierrez A.P., Ponti L., 2014. Analysis of invasive insects: links to climate change. In: Ziska L.H., Dukes J.S., (eds.), Invasive Species and Global Climate Change. CABI Publishing, Wallingford, UK. ISBN: 978-1780641645.

Dry matter partitioning in a ladybeetle PBDM.

Invasive species: why the biology matters

October 31, 2013 Leave a comment

Using published bi- and tri-trophic physiologically-based demographic system models having similar sub components, the geographic distributions and relative abundance (a measure of invasiveness) of six invasive herbivorous insect species is assessed prospectively across the United States and Mexico. The models used are mechanistic descriptions of the weather-driven biology of the species. The plant hosts and insect species included in the study are: (1) cotton/pink bollworm, (2) a fruit tree host/Mediterranean fruit fly, (3) olive/olive fly, (4) a perennial host/light brown apple moth; (5) grapevine/glassy-winged sharpshooter and its two egg parasitoids, (6) grapevine/European grapevine moth. All of these species are currently or have been targets for eradication. The goal of the analyses is to predict and explain prospectively the disparate distributions of the six species as a basis for examining eradication/containment efforts against them. The eradication of the new world screwworm is also reviewed in the discussion section because of its pivotal role in the development of the eradication paradigm.

Gutierrez A.P., Ponti L., 2013. Eradication of invasive species: why the biology matters. Environmental Entomology, 42: 395-411. | Free PDF reprint

Deconstructing the control of the spotted alfalfa aphid

May 14, 2013 Leave a comment

Control of insect pests and other taxa may be due to many factors that are difficult to separate and quantify as was the case for the control of the spotted alfalfa aphid (SAA, Therioaphis maculata Monell) in California and elsewhere. Introduced parasitoids, host plant resistance, pathogens and native predators led to its successful control, but the relative contribution of each factor remained largely unknown. The relative contribution of each control factor was estimated using a weather-driven physiologically-based demographic system model consisting of alfalfa, SAA (a), its three exotic parasitoids [Trioxys complanatus (Quilis) (b), Praon palitans Muesebeck (c), and Aphelinus semiflavus Howard (d)], a native coccinellid beetle [Hippodamia convergens (Guérin-Menéville)], a fungal pathogen [Erynia neoaphidis Remaudière & Hennebert (Zygomycetes: Entomophthorales) (g)], and host plant resistance (HPR) (h). Alone, each factor failed to control SAA, as did combinations of the parasitoids and coccinellid predation (f). Control was predicted across all ecological zones only when all mortality factors were included (i).

Gutierrez A.P., Ponti L., 2013. Deconstructing the control of the spotted alfalfa aphid Therioaphis maculata. Agricultural and Forest Entomology, 15: 272-284.

Sardinia olive systems in a warmer climate

February 23, 2010 Leave a comment

In the Mediterranean Basin, major islands including Sardinia are considered particularly vulnerable to global warming and desertification. We used a physiologically based demographic model (PBDM) of olive and olive fly to analyze in detail this plant-pest system in Sardinia under observed weather (ten years of daily data from 48 locations), three climate warming scenarios (increases of 1, 2 and 3 °C in average daily temperature), and a 105-year climate model scenario for the Alghero (e.g. 1951-2055). GRASS GIS was used to map model predictions, and model calibration with field bloom date data was performed to increase simulation accuracy of olive flowering predictions under climate change. As climate warms, the range of olive is predicted to expand to higher altitudes and consolidate elsewhere, especially in coastal areas. The range of olive fly will extend into previously unfavorable cold areas, but will contract in warm inland lowlands where temperatures approach its upper thermal limits. Consequently, many areas of current high risk are predicted to have decreased risk of fly damage with climate warming. Simulation using a 105 year climate model scenario for Alghero, Sardinia predicts changes in the olive-olive fly system expected to occur if climate continued to warm at the low rate observed during in the past half century.

Ponti L., Cossu Q.A., Gutierrez A.P., 2009. Climate warming effects on the Olea europaea–Bactrocera oleae system in Mediterranean islands: Sardinia as an example. Global Change Biology, 15: 2874–2884.

Mediterranean-wide analysis of the olive-olive fly system

August 6, 2009 Leave a comment

The Mediterranean Basin is expected to be particularly vulnerable to climate change including pronounced climate warming and desertification. Olive (Olea europaea) is of eco-social importance in the Mediterranean where it was domesticated, and it is also considered a sensitive climate indicator. This crop and its major pest, the olive fly Bactrocera oleae are a suitable model system to study Mediterranean climate. A weather-driven physiologically-based demographic model (PBDM) of olive and olive fly ( is being used to analyze this plant-pest system in the Mediterranean region based on ERA-40 weather data ( downscaled via the regional climate model RegCM3 coupled to the MIT ocean model. PBDM predictions are mapped with the open source GIS GRASS (

Ponti L., Gutierrez A.P., Ruti P.M., 2009. The olive–Bactrocera oleae system in the Mediterranean Basin: a physiologically based analysis driven by the ERA-40 climate data. 5th Study days “Models for Plant Protection”, Piacenza, Italy, 27-29 May 2009.