DOI: 10.5061/dryad.1s4f2
title: Data from: Roads increase population growth rates of a native leaf-cutter ant in Neotropical savannahs

description: A challenge in applied ecology is understanding the responses of native
 species to roads, which are ubiquitous drivers of environmental
 heterogeneity. While most studies highlight their negative effects, the
 potential for native species to increase in abundance near roads has been
 underappreciated, and the demographic mechanisms underlying abundance
 changes remain unclear. Elucidating these mechanisms requires first
 determining how demographic vital rates and life-history stages interact
 to influence population growth. One can then assess how roads alter the
 relative importance of the alternative demographic pathways – increased
 performance of early vs. late life stages – suggested as the principal
 drivers of increased population growth. We parameterized demographic
 models with 3 years of census data and conducted perturbation analyses to
 evaluate how proximity to roads altered abundance and demography. To do
 so, we used the leaf-cutter ant Atta laevigata as our model organism.
 Leaf-cutters are native ecosystem engineers and dominant herbivores in
 Neotropical ecosystems and also amongst the longest lived insects in
 nature. Our study was conducted in Cerrado savannahs, where road networks
 are rapidly expanding and Atta species are major agricultural pests. We
 found that 35–45% of adult colonies were located within 15 m of roads,
 which is significantly closer than expected at random. Population growth
 rates (λ) were &gt;1 both near and far from roads, but λ near roads
 were significantly (41%) higher. Elasticities of λ to early survival and
 growth rates were proportionally much higher than those of adult stages,
 irrespective of habitat. Life-table response experiment results indicate
 that the higher λ near roads was due primarily to the much higher
 colonization and early-life performance there. Synthesis and applications.
 Road networks are proliferating throughout biodiversity-rich regions.
 Developing conservation and management guidelines for species whose
 abundance is altered by roads requires understanding the demographic
 mechanisms that underpin these changes. We demonstrate that the higher
 growth rate of roadside Atta laevigata populations is due to increased
 early-life performance. Thus, the expansion of road networks could have
 major ecological and economic consequences by facilitating the increased
 abundance of ecosystem engineers and agricultural pests. Accounting for A.
 laevigata early life stages and careful planning of road placement should
 improve management strategies of protected areas and agricultural systems
 in Neotropical savannahs.
description: Ant demography
 dataField demographic data
 based on colony (nest mound) sizes of the ant Atta laevigata in a
 Brazilian Cerrado area. More details in the ReadMe
 file.data_MPM.csvAdult distances to the nearest roadField data collected during three years on the distance (in m) of adult Atta laevigata colonies (mound size &gt; 2 square metres) to the nearest road in a Brazilian Cerrado area. More details in the ReadMe file.distance_adults.final.csv