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The USGS had some great data on pesticide usage in the United States that causes great envy among Australian pest researchers. In this post we have a look at some of this data and present some spatial and temporal trends in an important pesticide group that has been the subject of much controversy in recent history. Such data allows researchers to better estimate selection pressure for resistance evolution, as well as other off-target effects of pesticide usage.


Where are climatically similar locations? This is not a straightforward question because a range of conditions contribute to climate including rainfall, temperature, and the seasonal and daily variation in these properties. A key set of spatial data that contains useful information on these ecoclimatic properties are the BIOCLIM variables frequently used in species distributinon models. We can download the data which contain the following variables. library(tidyverse) "data/bioclim/bioclim_var_description.csv" %>% read_csv() %>% knitr::kable() var desc bio01 Annual Mean Temperature bio02 Mean Diurnal Range (Mean of monthly (max temp - min temp)) bio03 Isothermality (BIO2/BIO7) (×100) bio04 Temperature Seasonality (standard deviation ×100) bio05 Max Temperature of Warmest Month bio06 Min Temperature of Coldest Month bio07 Temperature Annual Range (BIO5-BIO6) bio08 Mean Temperature of Wettest Quarter bio09 Mean Temperature of Driest Quarter bio10 Mean Temperature of Warmest Quarter bio11 Mean Temperature of Coldest Quarter bio12 Annual Precipitation bio13 Precipitation of Wettest Month bio14 Precipitation of Driest Month bio15 Precipitation Seasonality (Coefficient of Variation) bio16 Precipitation of Wettest Quarter bio17 Precipitation of Driest Quarter bio18 Precipitation of Warmest Quarter bio19 Precipitation of Coldest Quarter We can load this data into R and plot them for Australia.


Where do we grow things? This is an important question that can be answered in a few ways, but a more direct way is to just ask growers. This is what they did at a national scale in the 2017 United States’ Agriculture Census and here I am going to use R to load it, filter it, and plot the result. To start we need to download the data and the shape file of the USA counties (or states).


I never liked public speaking. When I was in primary school, I remember getting my younger sister to buy things for me from shops so I could avoid talking to adults. Although less severe in my adult life, I still can’t say I particularly enjoy giving presentations for their own sake. But what I have realised is that communication is a hugely important skill in just about every professional role, which motivated me to push passed the discomfort.


I don’t know why, but it took me a little while to properly make sense of these diagnostics, so I wanted to develop a very simple illustration of the logic behind these concepts. ROC stands for Receiver Operating Characteristics, while AUC is the area under this curve, which is used as a metric for model performance in a classification problem. Perfomance is measured as the ability to maximise true positives, while minimising false positives.


Selected Publications

Fencelines and field margins in broad-acre cropping systems are commonly a refuge for weeds, diseases and invertebrates because they avoid many cropping and pest management regimes applied inside fields. Here, a simulation approach was used to explore the effect of different fenceline management strategies, cropping characteristics and pest genetics on resistance evolution.
In Journal of Pest Science, 2019.

The evolution of pesticide resistance through space and time is of great economic significance to modern agricultural production systems, and consequently, is often well documented. It can thus be used to dissect the evolutionary and ecological processes that underpin large-scale evolutionary responses.
In Global Ecology and Biogeography, 2017.

Mechanistic models of the impacts of climate change on insects can be seen as very specific hypotheses about the connections between microclimate, ecophysiology and vital rates. These models must adequately capture stage-specific responses, carry-over effects between successive stages, and the evolutionary potential of the functional traits involved in complex insect life-cycles. Here we highlight key considerations for current approaches to mechanistic modelling of insect responses to climate change.
In COIS, 2016.

Insects are typified by their small size, large numbers, impressive reproductive output and rapid growth. However, insect growth is not simply rapid; rather, insects follow a qualitatively distinct trajectory to many other animals. Here we present a mechanistic growth model for insects and show that increasing specific assimilation during the growth phase can explain the near-exponential growth trajectory of insects.
In Proceedings of the Royal Society B, 2015.

Body size scaling relationships allow biologists to study ecological phenomena in terms of individual level metabolic processes. Body size scaling relationships allow biologists to study ecological phenomena in terms of individual level metabolic processes.
In Functional Ecology, 2015.

The uptake of resources from the environment is a basic feature of all life. Consumption rate has been found to scale with body size with an exponent close to unity across diverse organisms. However, past analyses have ignored the important distinction between ontogenetic and interspecific size comparisons. Using principles of dynamic energy budget theory, we present a mechanistic model for the body mass scaling of consumption, which separates interspecific size effects from ontogenetic size effects.
In Oikos, 2015.

Design constraints imposed by increasing size cause metabolic rate in animals to increase more slowly than mass. This ubiquitous biological phenomenon is referred to as metabolic scaling. Mechanistic explanations for interspecific metabolic scaling do not apply for ontogenetic size changes within a species implying different mechanisms for scaling phenomena. Here we show that the Dynamic Energy Budget theory approach of compartmentalizing biomass into reserve and structural components provides a unified framework for understanding ontogenetic and inter-specific metabolic scaling.
In American Naturalist, 2013.

Metabolic theory specifies constraints on the metabolic organisation of individual organisms. These constraints have important implications for biological processes ranging from the scale of molecules all the way to the level of populations, communities and ecosystems, with their application to the latter emerging as the field of metabolic ecology. While ecologists continue to use individual metabolism to identify constraints in ecological processes, the topic of metabolic scaling remains controversial.
In JAnE, 2013.

Recent Publications

. Field margins provide a refuge for pest genes beneficial to resistance management. In Journal of Pest Science, 2019.

Preprint PDF Project

. Climate contributes to the evolution of pesticide resistance. In Global Ecology and Biogeography, 2017.

Preprint PDF Project

. Mechanistic models for predicting insect responses to climate change. In COIS, 2016.

Preprint PDF Project

. Testing mechanistic models of growth in insects. In Proceedings of the Royal Society B, 2015.

Preprint PDF Project

. Ontogenetic and interspecific metabolic scaling in insects. In American Naturalist, 2013.

Preprint PDF Project

. Reconciling theories for metabolic scaling. In JAnE, 2013.

Preprint PDF Project


RLEM Resistance

Pest mites are a significant threat to the establishment of grain crops. Some species have become more problematic over the last decade as farming practices have changed, while others are proving difficult to control due to tolerance and insecticide resistance issues. The recent emergence of resistance to synthetic pyrethroids and organophosphates in the redlegged earth mite (RLEM) is of particular concern to the Australian grains industry.

The importance of body size - scaling of physiological traits in insects

Biological phenomena occur across wide scales in space, time, and organisational complexity. Molecules, which are small, quickly transforming units, exhibit new emergent properties when they are arranged into ecosystems. These properties of ecosystems, such as species diversity, distribution, standing biomass, or rates of nutrient turnover involve large spatial and temporal scales, as well as many underlying processes that make their study inherently complex. Integration across disciplines and across levels of biological organisation is one of the grand challenges in biology. Towards this end, novel methods are required so that cross-disciplinary phenomena can be quantified using a common metric. Energy and mass are two universal currencies that are able to cut through the hierarchy of biology, which must be both conserved irrespective to the scale of inquiry.