New paper! Understanding selective predation: are energy and nutrients important?

Authors: Tamara I. Potter, Hayley J. Stannard, Aaron C. Greenville and Chris R. Dickman.

Published in: Plos One.

Abstract:

Lesser-hairy footed dunnart (Sminthopsis youngsoni). Photo: T. Potter

For generalist predators, a mixed diet can be advantageous as it allows individuals to exploit a potentially broad range of profitable food types. Despite this, some generalist predators show preferences for certain types of food and may forage selectively in places or at times when these foods are available. One such species is the lesser hairy-footed dunnart (Sminthopsis youngsoni). Usually considered to be a generalist insectivore, in the Simpson Desert, Australia, this small marsupial predator has been found to selectively consume wolf spiders (Family Lycosidae), for reasons yet unknown. Here, we tested whether lycosids have relatively high energy or nutrient contents compared to other invertebrates, and hence whether these aspects of food quality can explain selective predation of lycosids by S. youngsoni. Energy, lipid and protein composition of representatives of 9 arthropod families that are eaten by S. youngsoni in the Simpson Desert were ascertained using microbomb calorimetry, chloroform-methanol extraction and Dumas combustion, respectively. Although lycosids contained a high proportion of energy and nutrients, they were not found to yield statistically greater amounts of these food components than many other available arthropod prey that are not selected by S. youngsoni. Our results therefore suggest that alternative factors may be more influential in shaping dietary selection in this marsupial predator, such as high rates of encounter between lycosids and S. youngsoni.

Reference: Potter, T., Stannard, H. J., Greenville, A.C. & Dickman, C.R. (2018). Understanding selective predation: are energy and nutrients important? Plos One, 13: e0201300 .

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New Paper! Making the most of incomplete long-term datasets: the MARSS solution

Authors: Aaron C. Greenville, Vuong Nguyen, Glenda M. Wardle and Chris R. Dickman

Published in: Australian Zoologist

Abstract:

Field work doesn’t always go to plan and can lead to gaps in your datasets.

Long-term field-based monitoring is essential to develop a deep understanding of how ecosystems function and to identify species at risk of decline. However, conducting field-based research poses some unique challenges due to the frequently harsh environmental conditions or extreme weather events that may be encountered. Fieldwork issues can arise from vehicle breakdowns, wildfires and heavy rainfall events, all of which can delay or even cancel data collection. In addition, long-term monitoring often requires multiple observers, which may add observation bias to estimates of measured parameters. Thus there is an increasing need to develop new statistical techniques that take advantage of the power of long time-series datasets that also are incomplete. Here we introduce researchers to multivariate autoregressive state-space (MARSS) modelling; a new statistical technique for modelling long-term time-series data. MARSS models allow users to investigate incomplete datasets caused by missing values. In contrast to traditional modelling techniques, such as generalised linear models that only estimate error from environmental stochasticity (process error), MARSS models estimate both process and observation errors. By estimating observation errors, researchers can incorporate bias from different observers and methods into population or other parameter estimates. To illustrate the MARSS technique we interrogate long-term animal and plant datasets from central Australia that contain missing values and were collected by multiple observers. We then discuss the findings from the MARSS models and their implications for management. Lastly, we provide future applications that this new technique could be used for, such as studies of animal movements and food webs.

Reference: Greenville, A. C, Nguyen, V.,  Wardle, G. M. & Dickman, C. R. (2018). Making the most of incomplete long-term datasets: the MARSS solution. Australian Zoologist, In-Press. 

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New paper: Assessing the potential for intraguild predation among taxonomically disparate micro-carnivores

Authors: Tamara I. Potter, Aaron C. Greenville & Chris R. Dickman.

Great work by Tamara and her first paper from her Honours work!

Published in: Royal Society Open Science

Abstract:

Wolf spider (Lycosa spp.). Photo: T. Potter

Interspecific competition may occur when resources are limited, and is often most intense between animals in the same ecological guild. Intraguild predation (IGP) is a distinctive
form of interference competition, where a dominant predator selectively kills subordinate rivals to gain increased access to resources. However, before IGP can be identified, organisms must be confirmed as members of the same guild and occur together in space and time.

The lesser hairy-footed dunnart

Lesser-hairy footed dunnart (Sminthopsis youngsoni). Photo: T. Potter

(Sminthopsis youngsoni, Dasyuridae) is a generalist marsupial insectivore in arid Australia, but consumes wolf spiders (Lycosa spp., Lycosidae) disproportionately often relative to their availability. Here, we test the hypothesis that this disproportionate predation is a product of frequent encounter rates between the interactants due to high overlap in their diets and use of space and time. Diet and prey availability were determined using direct observations and invertebrate pitfall trapping, microhabitat use by tracking individuals of both species-groups, and temporal activity using spotlighting and camera traps. Major overlap (greater than 75% similarity) was found in diet and temporal activity, and weaker overlap in microhabitat use. Taken together, these findings suggest reasonable potential, for the first time, for competition and intraguild predation to occur between taxa as disparate as marsupials and spiders.

Reference:

Potter, T., Greenville, A.C. & Dickman, C.R. (2018). Assessing the potential for intraguild predation among taxonomically disparate micro-carnivores: marsupials and arthropods. Royal Society Open Science, 5: 171872.

Media:

Marsupial species eats spiders to stop spiders eating insects, Australia’s Science Channel, May 2018.

The marsupial mouse eats its competitors (Dutch), Scientias, May 2018.

This dunnart has competition for food… so it just eats the competition, Australian Geographic, May 2018.

 

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New paper: Biodiversity responds to increasing climatic extremes in a biome-specific manner

Authors: Aaron C. Greenville, Emma Burns, Christopher R. Dickman, David A. Keith, David B. Lindenmayer, John W. Morgan, Dean Heinze, Ian Mansergh, Graeme R. Gillespie, Luke Einoder, Alaric Fisher, Jeremy Russell-Smith , Daniel J. Metcalfe, Peter T. Green, Ary A. Hoffmann, and Glenda M. Wardle.

Published in: Science of the Total Environment (Special edition & invited paper (23 accepted from 50 submissions) by the International Long Term Ecological Research Network).

Abstract:

An unprecedented rate of global environmental change is predicted for the next century. The response to this change by ecosystems around the world is highly uncertain. To address this uncertainty, it is critical to understand the potential drivers and mechanisms of change in order to develop more reliable predictions. Australia’s Long Term Ecological Research Network (LTERN) has brought together some of the longest running (10–60 years) continuous environmental monitoring programs in the southern hemisphere. Here, we compare climatic variables recorded at five LTERN plot network sites during their period of operation and place them into the context of long-term climatic trends. Then, using our unique Australian long-term datasets (total 117 survey years across four biomes), we synthesize results from a series of case studies to test two hypotheses: 1) extreme weather events for each plot network have increased over the last decade, and; 2) trends in biodiversity will be associated with recent climate change, either directly or indirectly through climate-mediated disturbance (wildfire) responses. We examined the biodiversity responses to environmental change for evidence of non-linear behavior. In line with hypothesis 1), an increase in extreme climate events occurred within the last decade for each plot network. For hypothesis 2), climate, wildfire, or both were correlated with biodiversity responses at each plot network, but there was no evidence of non-linear change. However, the influence of climate or fire was context-specific. Biodiversity responded to recent climate change either directly or indirectly as a consequence of changes in fire regimes or climate-mediated fire responses. A national long-term monitoring framework allowed us to find contrasting species abundance or community responses to climate and disturbance across four of the major biomes of Australia, highlighting the need to establish and resource long-term monitoring programs across representative ecosystem types, which are likely to show context-specific responses.

Reference:

Greenville A.C., Burns, B., Dickman, C.R., Keith, D.A., Lindenmayer, D.B., Morgan, J.W.,  Heinze, D., Mansergh, I., Gillespie, G.R., Einoder, L., Fisher, A., Russell-Smith, J., Metcalfe, D.J., Green, P.T., Hoffmann, A.A., and Wardle, G.M. (2018). Biodiversity responds to increasing climatic extremes in a biome-specific manner. Science of the Total Environment 634: 382–393.

 

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New paper: Interactions between wildfire and drought drive population responses of mammals in coastal woodlands

Authors: Mathew S. Crowther, Ayesha I. Tulloch, Mike Letnic, Aaron C. Greenville, & Chris R. Dickman

Published in: Journal of Mammalogy (Feature article)

Abstract:

Fire is an ecologically important process in many habitats. Increases in the frequency and intensity of wildfires due to anthropogenic activity or future changes in the global climate are suspected to impact heavily on components of the biota in fire-dependent landscapes, but there is almost no knowledge of how changes to fire regimes interact with other stressors such as drying environments. We used live-trapping techniques to investigate the effects of wildfire and drought on the abundance of 3 species of small mammals in coastal woodland in southeastern Australia. We used a generalized linear mixed effects model design to compare 4 years of post-fire trapping results with pre-fire data on both burned and unburned sites. Numbers of all small mammal species were declining due to drought prior to an extensive wildfire. Wildfire significantly exacerbated the decline in abundance of small mammals in the year after fire. A return to wetter climatic conditions was accompanied by a recovery in small mammal numbers, which was faster in unburnt sites than burnt sites. Our results demonstrate a strong linkage between climatic conditions, fire, and mammal assemblages, and emphasize the need for long-term research to disentangle the interactive effects of these factors on wildlife.

Reference:

Crowther, M.S, Tulloch, A.I., Letnic, M., Greenville, A.C., & Dickman, C.R. (2018). Interactions between wildfire and drought drive population responses of mammals in coastal woodlands. Journal of Mammalogy, doi.org/10.1093/jmammal/gyy003

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Book review: The Biology of Deserts

David Ward, 2nd edition. Oxford University Press, Oxford, 2016. xv + 370 pp.

First published in Austral Ecology.

Contrary to the popular perception that deserts are wastelands, they house some of the most diverse communities of flora and fauna of any environment on the planet. Thus, deserts provide biologists and ecologists an ideal setting to explore and test many ecological, behavioural, ecophysiological and evolutionary theories. Or as Professor
David Ward writes, we can view ‘deserts as laboratories of nature, where natural selection is exposed at its most extreme’. The Biology of Deserts provides a significant summary of the abiotic and biotic processes, which operate in arid environments, and represents one of the few general texts on desert biology (also see Whitford 2002).

Read the full review here.

 

References:

Whitford W. (2002). Ecology of Desert Systems. Academic Press, San Diego.

Greenville A.C. (2017). The Biology of Deserts – David Ward , 2nd edition. Austral Ecology, DOI: 10.1111/aec.12523

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New book: Lake Eyre basin rivers: environmental, social and economic importance.

Lake Eyre Basin Rivers outlines the environmental, social and economic values of the rivers from a diverse range of perspectives, including science, tourism, economy, engineering, policy, Traditional Owners and pastoralists. It describes the current state of the environment and the past and ongoing threats to the river systems, drawing on stories from the Murray-Darling Basin. It also provides direction for ensuring that the rivers remain free-flowing to service the environment and future generations.

I had the opportunity to contribute to one of the chapters.

Chapter 6: Developing the desert: potential effects on wildlife.

In this chapter we discuss the potential consequences of irrigation and mining developments on wildlife in arid Australia.

Reference:

Dickman C. R., Greenville A. C. & Wardle G. M. (2017) Developing the desert: potential effects on wildlife. In: Lake Eyre Basin rivers: environmental, social and economic importance. (ed R. T. Kingsford) pp. 63-74. CSIRO Publishing, Melbourne.

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