Abstract
Edge effects alter insect biodiversity in several ways. However, we still have a limited understanding on simultaneous responses of ecological populations and assemblages to ecotones, especially in human modified landscapes. We analyze edge effects on dung beetle populations and assemblages between livestock pastures and native temperate forests (Juniperus and pine-oak forests (POFs)) to describe how species abundances and assemblage parameters respond to edge effects through gradients in forest-pasture ecotones. In Juniperus forest 13 species avoided the ecotones: six species showed greater abundance in forest interior and seven in pasturelands, while the other two species had a neutral response to the edge. In a different way, in POF we found five species avoiding the edge (four with greater abundance in pastures and only one in forest), two species had a neutral response, and two showed a unimodal pattern of abundance near to the edge. At the assemblage level edge effects are masked, as species richness, diversity, functional richness, functional evenness, and compositional incidence dissimilarity did not vary along forest-pasture ecotones. However, total abundance and functional divergence showed higher values in pastures in one of the two sampling localities. Also, assemblage similarity based on species’ abundance showed a peak near to the edge in POF. We propose that conservation efforts in human-managed landscapes should focus on mitigating current and delayed edge effects. Ecotone management will be crucial in livestock dominated landscapes to conserve regional biodiversity and the environmental services carried out by dung beetles.
Highlights
We found 33,431 individuals from 20 species in Juniperus forest (JF), and 8,205 individuals from 16 species in pine-oak forests (POFs)
Dung beetles were more abundant in pasturelands (16,455 individuals in the JF locality, 6,285 individuals in the POF locality) than in forests (12,151 individuals in JF, 1,179 individuals in POF)
Ecological research on edge effects has been intensive in natural ecotones, but in the last decades research has focused on human-modified landscapes, where novel ecosystems are usually simple in structure and represent inhospitable habitats for many species
Summary
Despite an extensive body of research on edge effects as key processes influencing individuals, populations, ecological interactions, communities and ecosystem processes (Murcia, 1995; Ries et al, 2004; Porensky, 2011; Ewers, Bartlam & Didham, 2013; Ziter, Bennett & Gonzalez, 2014), relatively few studies have focused on simultaneousHow to cite this article Martínez-Falcón AP, Zurita GA, Ortega-Martínez IJ, Moreno CE. 2018. A series of recent studies using this continuous approach showed that species might have an unimodal response near to or at the edge, edge avoidance (sigmoid or linear response) or edge insensitivity (neutral response), and this framework can be applied to both complete (covering the entire range of distances) and incomplete biological responses to edge effects This approach has been recently used to assess edge effects in fragmented landscapes where native habitats such as forests have been converted into pastures and agricultural lands uses, to assess population responses in ecotones between forest fragments and novel agroecosystems (Campbell et al, 2011; Ewers, Bartlam & Didham, 2013; Peyras et al, 2013; Barnes et al, 2014; Villada-Bedoya et al, 2017)
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