Friday, September 12, 2014

Invasive species and climate change: the PBDM approach

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. http://www.cabi.org/bookshop/book/9781780641645

Trophic interactions in the yellow starthistle PBDM system.

Analysis of invasive insects: links to climate change

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. http://www.cabi.org/bookshop/book/9781780641645

Dry matter partitioning in a ladybeetle PBDM.

Tuesday, March 25, 2014

Olive bioeconomics under climate warming

Inability to determine reliably the direction and magnitude of change in natural and agro-ecosystems due to climate change poses considerable challenge to their management. Olive is an ancient ubiquitous crop having considerable ecological and socioeconomic importance in the Mediterranean Basin. We assess the ecological and economic impact of projected 1.8 °C climate warming on olive and its obligate pest, the olive fly. This level of climate warming will have varying impact on olive yield and fly infestation levels across the Mediterranean Basin, and result in economic winners and losers. The analysis predicts areas of decreased profitability that will increase the risk of abandonment of small farms in marginal areas critical to soil and biodiversity conservation and to fire risk reduction.

Ponti L., Gutierrez A.P., Ruti P.M., Dell’Aquila A., 2014. Fine scale ecological and economic assessment of climate change on olive in the Mediterranean Basin reveals winners and losers. Proceedings of the National Academy of Sciences, USA, http://dx.doi.org/10.1073/pnas.1314437111




Wednesday, March 12, 2014

Ultra-low, cryptic tropical fruit fly populations

A comment appeared in Proceedings B reviews a study by Papadopoulos, Plant, and Carey (2013; "From trickle to flood: the large-scale, cryptic invasion of California by tropical fruit flies." Proc. R. Soc. B: Biol. Sci. 280: http://dx.doi.org/10.1098/rspb.2013.1466) and suggests an alternative approach that addresses the biology of invasive species. In summary, inference of establishment of fruit flies based on recurrence data as performed by Papadopoulos et al. (2013) is neither explanatory nor provides confirmation of establishment in California. By contrast, physiologically based demographic models for medfly and olive fly accurately predict the potential distribution of the two fruit flies in California and elsewhere, and provide explanation for species phenology and dynamics that is critical for risk assessment and policy development for these and other invasive species under current climate and climate change scenarios.

Gutierrez A.P., Ponti L., Gilioli G., 2014. Comments on the concept of ultra-low, cryptic tropical fruit fly populations. Proceedings of the Royal Society B: Biological Sciences, 281, http://dx.doi.org/10.1098/rspb.2013.2825

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