Biogeography of species richness gradients: Linking adaptive traits, demography and diversification

Carnicer J., Brotons L., Stefanescu C., Peñuelas J. (2012) Biogeography of species richness gradients: Linking adaptive traits, demography and diversification. Biological Reviews. 87: 457-479.
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Doi: 10.1111/j.1469-185X.2011.00210.x

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Here we review how adaptive traits contribute to the emergence and maintenance of species richness gradients through their influence on demographic and diversification processes. We start by reviewing how demographic dynamics change along species richness gradients. Empirical studies show that geographical clines in population parameters and measures of demographic variability are frequent along latitudinal and altitudinal gradients. Demographic variability often increases at the extremes of regional species richness gradients and contributes to shape these gradients. Available studies suggest that adaptive traits significantly influence demographic dynamics, and set the limits of species distributions. Traits related to thermal tolerance, resource use, phenology and dispersal seem to play a significant role. For many traits affecting demography and/or diversification processes, complex mechanistic approaches linking genotype, phenotype and fitness are becoming progressively available. In several taxa, species can be distributed along adaptive trait continuums, i.e. a main axis accounting for the bulk of inter-specific variation in some correlated adaptive traits. It is shown that adaptive trait continuums can provide useful mechanistic frameworks to explain demographic dynamics and diversification in species richness gradients. Finally, we review the existence of sequences of adaptive traits in phylogenies, the interactions of adaptive traits and community context, the clinal variation of traits across geographical gradients, and the role of adaptive traits in determining the history of dispersal and diversification of clades. Overall, we show that the study of demographic and evolutionary mechanisms that shape species richness gradients clearly requires the explicit consideration of adaptive traits. To conclude, future research lines and trends in the field are briefly outlined. © 2011 The Authors. Biological Reviews © 2011 Cambridge Philosophical Society.

Llegeix més

Calibration of hybrid species distribution models: The value of general-purpose vs. targeted monitoring data

De Cáceres M., Brotons L. (2012) Calibration of hybrid species distribution models: The value of general-purpose vs. targeted monitoring data. Diversity and Distributions. 18: 977-989.
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Doi: 10.1111/j.1472-4642.2012.00899.x

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Aim Temporally replicated observations are essential for the calibration and validation of species distribution models (SDMs) aiming at making temporal extrapolations. We study here the usefulness of a general-purpose monitoring programme for the calibration of hybrid SDMs. As a benchmark case, we take the calibration with data from a monitoring programme that specifically surveys those areas where environmental changes expected to be relevant occur. Location Catalonia, north-east of Spain. Methods We modelled the distribution changes of twelve open-habitat bird species in landscapes whose dynamics are driven by fire and forest regeneration. We developed hybrid SDMs combining correlative habitat suitability with mechanistic occupancy models. We used observations from two monitoring programmes to provide maximum-likelihood estimates for spread parameters: a common breeding bird survey (CBS) and a programme specifically designed to monitor bird communities within areas affected by wildfires (DINDIS). Results Both calibration with CBS and DINDIS data yielded sound spread parameter estimates and range dynamics that suggested dispersal limitations. However, compared to calibration with DINDIS data, calibration with CBS data leads to biased estimates of spread distance for seven species and to a higher degree of uncertainty in predicted range dynamics for six species. Main conclusions We have shown that available monitoring data can be used in the calibration of the mechanistic component of hybrid SDMs. However, if the dynamics of the target species occur within areas not well covered, general-purpose monitoring data can lead to biased and inaccurate parameter estimates. To determine the potential usefulness of a given monitoring data set for the calibration of the mechanistic component of a hybrid SDM, we recommend quantifying the number of surveyed sites that are predicted to undergo habitat suitability changes. © 2012 Blackwell Publishing Ltd.

Llegeix més

Using species combinations in indicator value analyses

De Cáceres M., Legendre P., Wiser S.K., Brotons L. (2012) Using species combinations in indicator value analyses. Methods in Ecology and Evolution. 3: 973-982.
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Doi: 10.1111/j.2041-210X.2012.00246.x

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1. Indicator species are often determined using an analysis of the relationship between the species occurrence or abundance values from a set of sites and the classification of the same sites into site groups (habitat types, community types, disturbance states, etc.). It may happen, however, that a particular site group has no indicator species even if its sites have a community composition that is clearly distinct from the sites of other site groups. This motivates an exploration of the indicator value of not only individual species but also species combinations. 2. Here, we present a novel statistical approach to determine indicators of site groups using species data. Unlike traditional indicator value analysis, we allow indicators to be species combinations in addition to single species. We require that all the species forming the combination must occur in the site to use the combination as an indicator. We present a simple algorithm that identifies the set of indicators (each one being either a single species or a species combination) that show high positive predictive value for the target site group. Moreover, we demonstrate the use of the percentage of sites of the site group where at least one of its valid indicators occurs to determine whether the group can be reliably predicted throughout its range. 3. Using a simulation study, we show that if two species are not strongly correlated and their frequency in the data set is larger than the frequency of sites belonging to the site group, the joint occurrence of the two species has higher positive predictive value for the site group than the two species taken independently. 4. We illustrate the proposed method by determining which combinations of vascular plants can be used as indicators for 29 shrubland and forest vegetation types of New Zealand. 5. The proposed methodology extends traditional indicator value analyses and will be useful to develop multispecies ecological or environmental indicators. Further, it will allow newly surveyed sites to be reliably assigned to previously defined vegetation types. © 2012 The Authors. Methods in Ecology and Evolution © 2012 British Ecological Society.

Llegeix més

Identifying location and causality of fire ignition hotspots in a Mediterranean region

Gonzalez-Olabarria J.R., Brotons L., Gritten D., Tudela A., Teres J.A. (2012) Identifying location and causality of fire ignition hotspots in a Mediterranean region. International Journal of Wildland Fire. 21: 905-914.
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Doi: 10.1071/WF11039

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Fire ignitions tend to be spatially aggregated depending on their causality. In highly populated regions, such as the northern Mediterranean basin, human activities are the main cause of ignitions. The ability to locate zones with an intense and recurrent history of fire occurrence and identify their specific cause can be helpful in the implementation of measures to reduce the problem. In the present study, kernel methods, non-parametric statistical methods for estimating the spatial distribution of probabilities of point-based data, are used to define ignition hotspots based on historical records of fire ignitions in Catalonia for the period 19952006. Comparison of the cause of the ignitions within the area of the hotspots enabled analysis of the relation between the cause of the ignitions and the occurrence of hotspots. The results obtained highlighted that the activity of arsonists showed strong spatial clustering, with the share of intentionally caused ignitions within the hotspot areas accounting for 60.1% of the fires, whereas for the whole of Catalonia they only represented 24.3%. The findings of the study provide an opportunity to optimally allocate law-enforcement and educational resources within hotspot areas. © IAWF 2012.

Llegeix més

TEASIng apart alien species risk assessments: A framework for best practices

Leung B., Roura-Pascual N., Bacher S., Heikkilä J., Brotons L., Burgman M.A., Dehnen-Schmutz K., Essl F., Hulme P.E., Richardson D.M., Sol D., Vilà M. (2012) TEASIng apart alien species risk assessments: A framework for best practices. Ecology Letters. 15: 1475-1493.
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Doi: 10.1111/ele.12003

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Some alien species cause substantial impacts, yet most are innocuous. Given limited resources, forecasting risks from alien species will help prioritise management. Given that risk assessment (RA) approaches vary widely, a synthesis is timely to highlight best practices. We reviewed quantitative and scoring RAs, integrating > 300 publications into arguably the most rigorous quantitative RA framework currently existing, and mapping each study onto our framework, which combines Transport, Establishment, Abundance, Spread and Impact (TEASI). Quantitative models generally measured single risk components (78% of studies), often focusing on Establishment alone (79%). Although dominant in academia, quantitative RAs are underused in policy, and should be made more accessible. Accommodating heterogeneous limited data, combining across risk components, and developing generalised RAs across species, space and time without requiring new models for each species may increase attractiveness for policy applications. Comparatively, scoring approaches covered more risk components (50% examined > 3 components), with Impact being the most common component (87%), and have been widely applied in policy (> 57%), but primarily employed expert opinion. Our framework provides guidance for questions asked, combining scores and other improvements. Our risk framework need not be completely parameterised to be informative, but instead identifies opportunities for improvement in alien species RA. © 2012 Blackwell Publishing Ltd/CNRS.

Llegeix més

Fine-scale bird monitoring from light unmanned aircraft systems

Sarda-Palomera F, Bota G, Viñolo C, Pallarés O, Sazatornil V, Brotons L, Gomáriz S, Sarda F (2012) Fine-scale bird monitoring from light unmanned aircraft systems. Ibis 154: 177:183.

Differences in the climatic debts of birds and butterflies at a continental scale

DeVictor V, van Swaay C, Brereton T, Brotons L, Chamberlain D, Heliölä J, Herrando S, Julliard R, Kuusaari M, Lindstrom A, Reif J, Roy DB, Schweiger O, Settele J, Stefanescu C, Van Strein A, Van Turnhout C, Vermouzek Z, De Vries MW, Wynhoff I, Jiguet F (2012) Differences in the climatic debts of birds and butterflies at a continental scale. Nature Climate Change 2: 121-124.

Uncertainty in thermal tolerances and climatic debt

DeVictor V, van Swaay C, Brereton T, Brotons L, Chamberlain D, Heliölä J, Herrando S, Julliard R, Kuusaari M, Lindstrom A, Reif J, Roy DB, Schweiger O, Settele J, Stefanescu C, Van Strein A, Van Turnhout C, Vermouzek Z, De Vries MW, Wynhoff I, Jiguet F (2012) Uncertainty in thermal tolerances and climatic debt. Nature Climate Change 2: 638-639.

Modelling invasive alien species distributions from digital biodiversity atlases. Model upscaling as a means of reconciling data at different scales

Marcer A., Pino J., Pons X., Brotons L. (2012) Modelling invasive alien species distributions from digital biodiversity atlases. Model upscaling as a means of reconciling data at different scales. Diversity and Distributions. 18: 1177-1189.
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Doi: 10.1111/j.1472-4642.2012.00911.x

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Aim: There is a wealth of information on species occurrences in biodiversity data banks, albeit presence-only, biased and scarce at fine resolutions. Moreover, fine-resolution species maps are required in biodiversity conservation. New techniques for dealing with this kind of data have been reported to perform well. These fine-resolution maps would be more robust if they could explain data at coarser resolutions at which species distributions are well represented. We present a new methodology for testing this hypothesis and apply it to invasive alien species (IAS). Location: Catalonia, Spain. Methods: We used species presence records from the Biodiversity data bank of Catalonia to model the distribution of ten IAS which, according to some recent studies, achieve their maximum distribution in the study area. To overcome problems inherent with the data, we prepared different correction treatments: three for dealing with bias and five for autocorrelation. We used the MaxEnt algorithm to generate models at 1-km resolution for each species and treatment. Acceptable models were upscaled to 10 km and validated against independent 10 km occurrence data. Results: Of a total of 150 models, 20 gave acceptable results at 1-km resolution and 12 passed the cross-scale validation test. No apparent pattern emerged, which could serve as a guide on modelling. Only four species gave models that also explained the distribution at the coarser scale. Main conclusions: Although some techniques may apparently deliver good distribution maps for species with scarce and biased data, they need to be taken with caution. When good independent data at a coarser scale are available, cross-scale validation can help to produce more reliable and robust maps. When no independent data are available for validation, however, new data gathering field surveys may be the only option if reliable fine-scale resolution maps are needed. © 2012 Blackwell Publishing Ltd.

Llegeix més

History matters: Previous land use changes determine post-fire vegetation recovery in forested Mediterranean landscapes

Puerta-Piñero C., Espelta J.M., Sánchez-Humanes B., Rodrigo A., Coll L., Brotons L. (2012) History matters: Previous land use changes determine post-fire vegetation recovery in forested Mediterranean landscapes. Forest Ecology and Management. 279: 121-127.
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Doi: 10.1016/j.foreco.2012.05.020

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Land use changes and shifts in disturbance regimes (e.g. wildfires) are recognized worldwide as two of the major drivers of the current global change in terrestrial ecosystems. We expect that, in areas with large-scale land use changes, legacies from previous land uses persist and affect current ecosystem responses to climate-associated disturbances like fire. This study analyses whether post-fire vegetation dynamics may differ according to specific historical land use histories in a Mediterranean forest landscape of about 60,000. ha that was burnt by extensive fires. For that, we assessed land use history of the whole area through the second half of the XXth century, and evaluated the post-fire regeneration success in terms of: (i) forest cover and (ii) tree species composition (biotic-dispersed, resprouter species, Quercus spp. vs. wind-dispersed species with or without fire-resistant seed bank, Pinus spp.). Results showed that stable forest areas exhibited a higher post-fire recovery than younger forests. Furthermore, the longer since crop abandonment translates into a faster post-fire recovery. Results highlight that to anticipate the impacts of disturbances on ecosystems, historical land trajectories should be taken into account. © 2012 Elsevier Ltd.

Llegeix més

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