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Journal ArticleDOI

Drove roads: keystone structures that promote ant diversity in Mediterranean forest landscapes

01 May 2013-Acta Oecologica-international Journal of Ecology (Elsevier Masson)-Vol. 49, pp 107-115

Abstract: Drove roads are the traditional corridors used by pastoralists for seasonal movements of livestock (transhumance). They cover a considerable land area in Mediterranean countries and, although they are an obvious source of landscape diversity, their influence on the diversity and composition of animal assemblages has not been documented. Ant communities were studied on four active drove roads, two in forests (submediterranean and conifer) and two in open environments (croplands and rangelands). They were compared with the respective matrix communities and their contribution to local species richness was evaluated. The effects were heavily dependent on the open or closed nature of the matrix. In forest environments, drove roads increased ant species richness at the local scale, acting as clear keystone structures. Their species richness and functional diversity were highest on the fine scale, species composition was different, and a slight edge effect in the matrix was detected. In contrast, drove roads had little or even a negative effect in open environment locations. We conclude that drove roads have a high conservation value for ants in Mediterranean forest environments, in addition to their importance as reservoirs of plant biodiversity and generators of ecological goods and services.
Topics: Species richness (59%), Biodiversity (53%), Spatial heterogeneity (50%)

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!"
"
Drove roads: keystone structures that promote ant diversity in !"
Mediterranean forest landscapes #"
$"
%"
Francisco M. Azcárate
a,*
, Javier Seoane
a
, Sara Castro
b
, Begoña Peco
a
&"
'"
a
TEG, Departamento de Ecología, Universidad Autónoma de Madrid. 28049, ("
Spain
)"
b
Unidad de Zoología, Departamento de Biología, Universidad Autónoma de *"
Madrid. 28049, Spain !+"
!!"
*
Corresponding author: Tel.: +34 91 497 3513; fax: +34 91 497 8001. E-mail !#"
address: fm.azcarate@uam.es !$"
!%"

#"
"
Abstract !&"
!'"
Drove roads are the traditional corridors used by pastoralists for seasonal !("
movements of livestock (transhumance). They cover a considerable land area !)"
in Mediterranean countries and, although they are an obvious source of !*"
landscape diversity, their influence on the diversity and composition of animal #+"
assemblages has not been documented. Ant communities were studied on four #!"
active drove roads, two in forests (submediterranean and conifer) and two in ##"
open environments (croplands and rangelands). They were compared with the #$"
respective matrix communities and their contribution to local species richness #%"
was evaluated. The effects were heavily dependent on the open or closed #&"
nature of the matrix. In forest environments, drove roads increased ant species #'"
richness at the local scale, acting as clear keystone structures. Their species #("
richness and functional diversity were highest on the fine scale, species #)"
composition was different, and a slight edge effect in the matrix was detected. #*"
In contrast, drove roads had little or even a negative effect in open environment $+"
locations. We conclude that drove roads have a high conservation value for $!"
ants in Mediterranean forest environments, in addition to their importance as $#"
reservoirs of plant biodiversity and generators of ecological goods and services. $$"
$%"
$&"
Keywords: Transhumance; Functional diversity; Spatial heterogeneity; $'"
Grasslands; Ant assemblages $("

$"
"
1. Introduction $)"
$*"
Drove roads, also known as stock routes, are one of the most characteristic %+"
components of traditional landscapes in Mediterranean countries (Ruiz and %!"
Ruiz, 1986; Mangas Navas, 1992; Merino García and Alier Gándaras, 2004). %#"
Active drove roads stand out in the landscape as well-defined strips up to 100 m %$"
in width with a savannah-like grassland appearance, in some cases running for %%"
several hundred kilometres. They are reserved for and ecologically modeled by %&"
transhumance, a traditional type of pastoralism consisting on the seasonal %'"
movement of livestock between summer and winter pastures. In Spain, drove %("
roads cover nearly 1% of the country's land area, with a total length of about %)"
125,000km (Mangas Navas, 1992; Merino García and Alier Gándaras, 2004). %*"
Due to their grid-like distribution, most of the country's land area is in contact &+"
with or near a drove road (Azcárate et al. 2012). Drove roads are at least &!"
several centuries old, and may have originally been based on the migratory &#"
routes of wild ungulates (Manzano and Casas, 2010). Because of their &$"
enormous area, long-term persistence, impact on the landscape structure and &%"
capacity to host herbivore migrations, drove roads can have played a major &&"
ecological role in the Mediterranean Basin. The current crisis in extensive &'"
grazing has led to the abandonment of transhumance and grazing uses of &("
drove roads (Ruiz and Ruiz, 1986; Ruiz, 2001), causing a loss of their &)"
differentiation from the surrounding ecological matrix. Their influence on &*"
populations and communities may thus disappear before they are identified and '+"
studied. '!"
'#"

%"
"
The few published ecological studies of drove roads have focused on their '$"
effects on plant communities. Drove roads have traditionally been regarded as a '%"
good example of ecological corridors for plant species (review in Bunce et al., '&"
2006), although no experimental evidence supported this view until Manzano ''"
and Malo (2006) detected epizoochorous seed dispersal over distances of up to '("
400 km. More recently, the effects of drove roads on landscape patterns, ')"
species composition and functional diversity of plant communities have been '*"
measured (Azcárate et al, 2012), showing that drove roads are a source of (+"
spatial heterogeneity and a reservoir for many plant species in non- or (!"
moderately-grazed habitats. (#"
($"
Drove roads could also have a noticeable effect on the diversity and (%"
composition of animal assemblages. Active drove roads maintain patches of (&"
open grassland in non-grazed environments such as forests, and hence ('"
increase spatial heterogeneity. Spatial heterogeneity and diversity of several (("
animal species groups are often (but not always) correlated (Duelli, 1997; Atauri ()"
and de Lucio, 2001; Szczepko et al., 2012). It has been argued that each (*"
animal species group depends on a specific structural aspect of the vegetation )+"
whose presence or quality can be detected at a certain spatial scale (Tews et )!"
al, 2004). At that scale, biodiversity is favoured by the occurrence of “keystone )#"
structures”, characterized by their ability to provide resources, shelter or nesting )$"
sites to that species group. Examples of keystone structures at different spatial )%"
scales are tree cavities in forests (for insects, birds and mammals), trees in )&"
African savannas (for arboreal rodents, ungulates, raptors and other species )'"
groups) and temporary wetlands in agricultural fields (for carabid beetles) (Tews )("

&"
"
et al., 2004; Remm and Lohmus, 2011). If a key structure affects several ))"
species groups, or groups with a strong influence on ecosystem functioning, )*"
then its conservation is of crucial importance. Drove roads might then function *+"
as keystone structures by favouring rich groups of terrestrial species with *!"
relevant roles on ecosystem functioning, such as ants. *#"
*$"
Ants are considered to be a focal group for the monitoring of terrestrial *%"
ecosystems (Underwood and Fisher, 2006; Crist, 2009). This is not surprising, *&"
given their ability to stockpile a considerable amount of primary and secondary *'"
production, interact with several organisms and act as ecosystem engineers *("
(Folgarait, 1998; MacMahon et al., 2000; Crist, 2009). Literature shows that *)"
ants respond strongly to land management (Bestelmeyer and Wiens, 1996; **"
Chen et al., 2011), and are sensitive to different levels of grazing (Read and !++"
Andersen, 2000; Boulton et al. 2005; Azcárate and Peco, 2011). Moreover, ants !+!"
are widespread, moderately diverse and easy to sample (Alonso and Agosti, !+#"
2000; Andersen et al., 2004). Their role as indicators has improved with the !+$"
development of the concept of functional groups to classify ants within species !+%"
assemblages, as first proposed in Australia (Andersen, 1995), and then !+&"
extended worldwide (Brown, 2000). More recently, the role of ants in ecosystem !+'"
functioning has been studied by measuring their functional diversity (Bihn et al., !+("
2010; Silva and Brandao, 2010) although this approach has still been little !+)"
addressed, in contrast to other taxa. !+*"
!!+"
The present study evaluates the role of drove roads as keystone structures. !!!"
Specifically, our work analyzes the effects of drove roads on ant assemblages !!#"

Citations
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01 Aug 2016-Oecologia
TL;DR: The relationship of land use with taxonomic diversity and functional diversity is highly complex and context-dependent and it is found that TD and FD did not vary consistently, but rather followed different trajectories that largely depended on the biotic group and the intensity of land-use transformation.
Abstract: Land-use change is the major driver of biodiversity loss. However, taxonomic diversity (TD) and functional diversity (FD) might respond differently to land-use change, and this response might also vary depending on the biotic group being analysed. In this study, we compare the TD and FD of four biotic groups (ants, birds, herbaceous, woody vegetation) among four land-use types that represent a gradient of land-use intensity in a Mediterranean landscape (Mediterranean shrublands, dehesas, mixed-pine forests, olive groves). Analyses were performed separately at two different spatial scales: the sampling unit scale and the site scale. Land-use intensity effects on TD and FD were quite different and highly varied among the four biotic groups, with no single clear pattern emerging that could be considered general for all organisms. Additive partitioning of species diversity revealed clear contrasting patterns between TD and FD in the percentage of variability observed at each spatial scale. While most variability in TD was found at the larger scales, irregardless of organism group and land-use type, most variability in FD was found at the smallest scale, indicating that species turnover among communities is much greater than functional trait turnover. Finally, we found that TD and FD did not vary consistently, but rather followed different trajectories that largely depended on the biotic group and the intensity of land-use transformation. Our results highlight that the relationship of land use with TD and FD is highly complex and context-dependent.

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Cites background from "Drove roads: keystone structures th..."

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TL;DR: It is shown that livestock DRs act as reservoirs of wild bee diversity within intensive agricultural matrices, enhancing wild bee visitation and seed set in adjacent sunflower crops.
Abstract: Natural and semi-natural habitats within agricultural landscapes provide food and nesting resources for wild bees, thus promoting crop pollination services. In central Spain, a large network of drove roads (DRs) crosses extensive areas of intensive agricultural fields. DRs are tracks (20⿿75 m wide) with semi-natural vegetation, protected for their priority function of transhumant livestock herding. In this study, we analyse the bee community of one of the main Spanish DRs, and evaluate its effects on flower visitation and seed set in adjacent sunflower fields. We used pan traps to assess bee abundance and richness at 13 sites along the DR and in adjacent sunflower fields at 10, 75 and 150 m from the DR. We also conducted visual counts to assess visitation rates to sunflower heads and measured seed set. Wild bee abundance and richness were significantly higher in the DR than in sunflower fields; but there were no significant differences among distances within sunflower fields. Honey bee abundance did not differ between the DR and sunflower fields. Wild bee visitation to sunflower heads was higher at 10 m compared to 75 and 150 m from the DR, but differences in honey bee visitation were non-significant. Sunflower seed set was significantly higher at 10 m compared to 75 and 150 m, and was associated with wild bee abundance, but not with honey bee abundance. Our results show that livestock DRs act as reservoirs of wild bee diversity within intensive agricultural matrices, enhancing wild bee visitation and seed set in adjacent sunflower crops.

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Abstract: Quantifying and reconstructing past vegetation changes is an important step to fully understand human-environment interactions in the past. In this study we present a reconstruction of arboreal cover of six study sites in the Gredos Range (central Spain) over the last 3000 yr based on multivariate statistical analysis (cluster analysis and non-metric multidimensional scaling, NMDS) of 186 modern pollen samples, modern vegetation data and six detailed fossil pollen records. The integrated approach allows distinguishing eight modern vegetation communities and linking the fossil pollen records with these vegetation communities as modern analogues. The information of the arboreal cover of the modern pollen sites was used to estimate the past arboreal cover of the fossil pollen sites in the Gredos Range. This estimated arboreal cover shows a higher level of landscape openness than suggested by the original pollen percentages data. Our results show that the evolution of the arboreal cover through time differs along an altitudinal gradient, with a decrease in arboreal cover during the Roman and Visigoth periods (2000–1240 cal BP) at low altitudes and only during the Christian/Feudal period (850–500 cal BP) at high altitudes. The applied methodology, integrating fossil pollen data with modern pollen and vegetation data in one NMDS, allows reconstructing past arboreal cover in a quantitative way.

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Abstract: A high-altitude peat sequence from the heart of the Spanish Central System (Gredos range) was analysed through a multi-proxy approach to determine the sensitivity of high-mountain habitats to climate, fire and land use changes during the last seven hundred years, providing valuable insight into our understanding of the vegetation history and environmental changes in a mountain pass close to a traditional route of transhumance. The pollen data indicate that the vegetation was dominated by shrublands and grasslands with scattered pines in high-mountain areas, while in the valleys cereals, chestnut and olive trees were cultivated. Strong declines of high-mountain pines percentages are recorded at 1540, 1675, 1765, 1835 and 1925 cal AD, which may be related to increasing grazing activities and/or the occurrence of anthropogenic fires. The practice of mountain summer farming and transhumance deeply changed and redesigned the landscape of the high altitudes in central Spain (Gredos range) since the Middle Ages, although its dynamics was influenced in some way by climate variability of the past seven centuries.

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Journal ArticleDOI
Abstract: Drove roads are a major feature of Mediterranean countries, where this live- stock management system has been practiced for centuries. In Spain, many drove roads have become completely or partially abandoned by herders, and transformed for other land uses. Yet, some major drove roads continue to be used for the passage of livestock, and might exert important effects on the conservation of biodiversity and ecosystem functions, particularly in highly transformed agricultural landscapes. In this study, we compare ant taxonomic and functional diversity on a drove road that is still used by transhumant livestock (the Conquense Drove Road) versus an abandoned road (the Murciana Drove Road). Ant species richness per trap and ant richness per sample unit were significantly higher on the used drove road compared to the abandoned drove road. The used drove road also had a positive edge effect on ant species diversity in adjacent croplands (both her- baceous crops and vineyards). Ant functional diversity was also higher on the used drove road. These results draw attention to the role of drove roads as ecologically unique systems and reservoirs of biodiversity, particularly within intensive agricultural landscapes. These effects, however, are largely dependent on maintaining livestock use.

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References
More filters

Journal ArticleDOI
29 Aug 1997-Science
TL;DR: Functional composition and functional diversity were the principal factors explaining plant productivity, plant percent nitrogen, plant total nitrogen, and light penetration in grassland plots.
Abstract: Humans are modifying both the identities and numbers of species in ecosystems, but the impacts of such changes on ecosystem processes are controversial. Plant species diversity, functional diversity, and functional composition were experimentally varied in grassland plots. Each factor by itself had significant effects on many ecosystem processes, but functional composition and functional diversity were the principal factors explaining plant productivity, plant percent nitrogen, plant total nitrogen, and light penetration. Thus, habitat modifications and management practices that change functional diversity and functional composition are likely to have large impacts on ecosystem processes.

2,568 citations


"Drove roads: keystone structures th..." refers result in this paper

  • ...This result is compatible with the sampling effect hypothesis (SEH) (Tilman et al., 1997), which predicts that successive additive random draws from a regional species pool lead to an increase in trait states....

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Journal ArticleDOI
Jörg Tews1, Ulrich Brose2, Volker Grimm, Katja Tielbörger1  +3 moreInstitutions (2)
TL;DR: It is shown that ecological effects of habitat heterogeneity may vary considerably between species groups depending on whether structural attributes are perceived as heterogeneity or fragmentation, and possible effects may also vary relative to the structural variable measured.
Abstract: Aim In a selected literature survey we reviewed studies on the habitat heterogeneity–animal species diversity relationship and evaluated whether there are uncertainties and biases in its empirical support. Location World-wide. Methods We reviewed 85 publications for the period 1960–2003. We screened each publication for terms that were used to define habitat heterogeneity, the animal species group and ecosystem studied, the definition of the structural variable, the measurement of vegetation structure and the temporal and spatial scale of the study. Main conclusions The majority of studies found a positive correlation between habitat heterogeneity/diversity and animal species diversity. However, empirical support for this relationship is drastically biased towards studies of vertebrates and habitats under anthropogenic influence. In this paper, we show that ecological effects of habitat heterogeneity may vary considerably between species groups depending on whether structural attributes are perceived as heterogeneity or fragmentation. Possible effects may also vary relative to the structural variable measured. Based upon this, we introduce a classification framework that may be used for across-studies comparisons. Moreover, the effect of habitat heterogeneity for one species group may differ in relation to the spatial scale. In several studies, however, different species groups are closely linked to ‘keystone structures’ that determine animal species diversity by their presence. Detecting crucial keystone structures of the vegetation has profound implications for nature conservation and biodiversity management.

2,383 citations


"Drove roads: keystone structures th..." refers background or result in this paper

  • ...…at different spatial scales are tree cavities in forests (for insects, birds and mammals), trees in African savannas (for arboreal rodents, ungulates, raptors and other species groups) and temporary wetlands in agricultural fields (for carabid beetles) (Tews et al., 2004; Remm and Lohmus, 2011)....

    [...]

  • ...Following Tews et al. (2004), the keystone structure characteristic was recognized if an abrupt increase in the pattern of species accumulation occurred when the curve entered a new habitat type....

    [...]

  • ...Firstly, drove roads are distinct spatial structures within larger and more homogeneous matrices (Azcárate et al., 2012), what coincides with the physical appearance described by Tews et al. (2004) for keystone structures....

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  • ...It has been argued that each animal species group depends on a specific structural aspect of the vegetation whose presence or quality can be detected at a certain spatial scale (Tews et al., 2004)....

    [...]

  • ...If drove roads crossing forest environments provide resources or nesting sites to ants as a species group, then they are good candidates to be considered as keystone structures (Tews et al., 2004)....

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Journal ArticleDOI
Etienne Laliberté1, Pierre Legendre2Institutions (2)
01 Jan 2010-Ecology
TL;DR: A highly flexible distance-based framework to measure different facets of FD in multidimensional trait space from any distance or dissimilarity measure, any number of traits, and from different trait types (i.e., quantitative, semi-quantitative, and qualitative).
Abstract: A new framework for measuring functional diversity (FD) from multiple traits has recently been proposed. This framework was mostly limited to quantitative traits without missing values and to situations in which there are more species than traits, although the authors had suggested a way to extend their framework to other trait types. The main purpose of this note is to further develop this suggestion. We describe a highly flexible distance-based framework to measure different facets of FD in multidimensional trait space from any distance or dissimilarity measure, any number of traits, and from different trait types (i.e., quantitative, semi-quantitative, and qualitative). This new approach allows for missing trait values and the weighting of individual traits. We also present a new multidimensional FD index, called functional dispersion (FDis), which is closely related to Rao's quadratic entropy. FDis is the multivariate analogue of the weighted mean absolute deviation (MAD), in which the weights are species relative abundances. For unweighted presence-absence data, FDis can be used for a formal statistical test of differences in FD. We provide the "FD" R language package to easily implement our distance-based FD framework.

2,098 citations


"Drove roads: keystone structures th..." refers methods in this paper

  • ...Functional diversity was thenmeasured with the FDis index, the mean distance in a multidimensional trait space of individual species from the centroid of all species in an assemblage (LaLiberté and Legendre, 2010)....

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Journal ArticleDOI
TL;DR: FD measures can explain variation in ecosystem function even when richness does not, and should be incorporated into conservation and restoration decision-making, especially for those efforts attempting to reconstruct or preserve healthy, functioning ecosystems.
Abstract: Summary 1. The goal of conservation and restoration activities is to maintain biological diversity and the ecosystem services that this diversity provides. These activities traditionally focus on the measures of species diversity that include only information on the presence and abundance of species. Yet how diversity influences ecosystem function depends on the traits and niches filled by species. 2. Biological diversity can be quantified in ways that account for functional and phenotypic differences. A number of such measures of functional diversity (FD) have been created, quantifying the distribution of traits in a community or the relative magnitude of species similarities and differences. We review FD measures and why they are intuitively useful for understanding ecological patterns and are important for management. 3. In order for FD to be meaningful and worth measuring, it must be correlated with ecosystem function, and it should provide information above and beyond what species richness or diversity can explain. We review these two propositions, examining whether the strength of the correlation between FD and species richness varies across differing environmental gradients and whether FD offers greater explanatory power of ecosystem function than species richness. 4. Previous research shows that the relationship between FD and richness is complex and context dependent. Different functional traits can show individual responses to different gradients, meaning that important changes in diversity can occur with minimal change in richness. Further, FD can explain variation in ecosystem function even when richness does not. 5. Synthesis and applications. FD measures those aspects of diversity that potentially affect community assembly and function. Given this explanatory power, FD should be incorporated into conservation and restoration decision-making, especially for those efforts attempting to reconstruct or preserve healthy, functioning ecosystems.

1,258 citations


"Drove roads: keystone structures th..." refers background in this paper

  • ...The ideal index of functional diversity should be based on functional traits that correlate well with ecosystem function (Cadotte et al., 2011)....

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Journal ArticleDOI
Abstract: ▪ Abstract Edge effects have been studied for decades because they are a key component to understanding how landscape structure influences habitat quality. However, making sense of the diverse patterns and extensive variability reported in the literature has been difficult because there has been no unifying conceptual framework to guide research. In this review, we identify four fundamental mechanisms that cause edge responses: ecological flows, access to spatially separated resources, resource mapping, and species interactions. We present a conceptual framework that identifies the pathways through which these four mechanisms can influence distributions, ultimately leading to new ecological communities near habitat edges. Next, we examine a predictive model of edge responses and show how it can explain much of the variation reported in the literature. Using this model, we show that, when observed, edge responses are largely predictable and consistent. When edge responses are variable for the same species ...

1,149 citations


"Drove roads: keystone structures th..." refers background in this paper

  • ...We surmise that ant assemblages in adjacent matrices are affected by edge effects, although on the basis of our datawe cannot rule which specific mechanisms are involved (Ries et al., 2004)....

    [...]


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