TY - JOUR
T1 - Woody vegetation remnants within pastures influence locust distribution
T2 - Testing bottom-up and top-down control
AU - Lawton, Douglas
AU - Waters, Cathy
AU - Le Gall, Marion
AU - Cease, Arianne
N1 - Funding Information:
Thanks go to Ian Toole and Warren Smith for their lab and field assistance in Australia. Thanks to the Trangie Agricultural Research Centre and the New South Wales Department of Industries for the use of vehicles and lab space. For the lab work at ASU, thanks go Nidia Martinez, Michael Saban-Hutchinson, Jonah Broseman, and Natalia Thompson. This research is supported by National Science FoundationDEB-1313693 and CHE-1313958.
Funding Information:
Thanks go to Ian Toole and Warren Smith for their lab and field assistance in Australia. Thanks to the Trangie Agricultural Research Centre and the New South Wales Department of Industries for the use of vehicles and lab space. For the lab work at ASU, thanks go Nidia Martinez, Michael Saban-Hutchinson, Jonah Broseman, and Natalia Thompson. This research is supported by National Science Foundation DEB-1313693 and CHE-1313958 .
Publisher Copyright:
© 2020 Elsevier B.V.
PY - 2020/7/1
Y1 - 2020/7/1
N2 - Agriculture is a major factor in landscape fragmentation, altering nutrient cycling and animal and plant populations through increasing habitat edge density. Most research on insect herbivores in agroecosystems has focused on the top-down effects of predators moving throughout the habitat mosaic. Few studies have focused on the top-down and bottom-up factors modulating the distribution of insect herbivore populations between natural and agricultural patches. For example, despite an understanding that Australian plague locusts (Chortoicetes terminifera) avoid tree patches, the underlying mechanisms remain unknown. Here, we explored how wooded remnants within pastures affect locust density and the potential top-down and bottom-up mechanistic explanations. We tested three hypotheses: 1) grasses near wooded areas are nutritionally suboptimal, 2) predator density is higher near wooded areas, and 3) temperatures are cooler underneath trees. We measured locust density, grass nutrient content, predator abundance, temperature, and ground cover along 50 m transects from wooded areas to open grassy areas. We ran those transects in three fields and had four transects per field. We confirmed locust avoidance for trees at a 20 m periphery, however none of the variables tested independently explained this trend. Grass nutrient content was similar underneath wooded areas and in open patches. Predator abundance did not differ between the two habitats. The ground was warmer under wooded areas than in grassy areas potentially due to woody vegetation negating windchill. Further, we found that locust density was negatively correlated with plant protein content and was highest in areas with approximately 20 % bare ground cover. Both plant protein and ground cover are important for grasshopper performance and reproduction. It is likely a complex interaction between these variables and others that drive the distribution of this species and other insect herbivores in agroecosystems. The small-scale mechanisms driving the response of insect herbivores to landscape changes is critical to understanding and predicting population dynamics at large-scales.
AB - Agriculture is a major factor in landscape fragmentation, altering nutrient cycling and animal and plant populations through increasing habitat edge density. Most research on insect herbivores in agroecosystems has focused on the top-down effects of predators moving throughout the habitat mosaic. Few studies have focused on the top-down and bottom-up factors modulating the distribution of insect herbivore populations between natural and agricultural patches. For example, despite an understanding that Australian plague locusts (Chortoicetes terminifera) avoid tree patches, the underlying mechanisms remain unknown. Here, we explored how wooded remnants within pastures affect locust density and the potential top-down and bottom-up mechanistic explanations. We tested three hypotheses: 1) grasses near wooded areas are nutritionally suboptimal, 2) predator density is higher near wooded areas, and 3) temperatures are cooler underneath trees. We measured locust density, grass nutrient content, predator abundance, temperature, and ground cover along 50 m transects from wooded areas to open grassy areas. We ran those transects in three fields and had four transects per field. We confirmed locust avoidance for trees at a 20 m periphery, however none of the variables tested independently explained this trend. Grass nutrient content was similar underneath wooded areas and in open patches. Predator abundance did not differ between the two habitats. The ground was warmer under wooded areas than in grassy areas potentially due to woody vegetation negating windchill. Further, we found that locust density was negatively correlated with plant protein content and was highest in areas with approximately 20 % bare ground cover. Both plant protein and ground cover are important for grasshopper performance and reproduction. It is likely a complex interaction between these variables and others that drive the distribution of this species and other insect herbivores in agroecosystems. The small-scale mechanisms driving the response of insect herbivores to landscape changes is critical to understanding and predicting population dynamics at large-scales.
KW - Agricultural mosaic
KW - Australia
KW - Drylands
KW - Insect herbivore
KW - Population dynamics
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U2 - 10.1016/j.agee.2020.106931
DO - 10.1016/j.agee.2020.106931
M3 - Article
AN - SCOPUS:85082658742
SN - 0167-8809
VL - 296
JO - Agriculture, Ecosystems and Environment
JF - Agriculture, Ecosystems and Environment
M1 - 106931
ER -