Prominent role of invasive species in avian biodiversity loss

Clavero M., Brotons L., Pons P., Sol D. (2009) Prominent role of invasive species in avian biodiversity loss. Biological Conservation. 142: 2043-2049.
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Doi: 10.1016/j.biocon.2009.03.034

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The rise of extinction rates associated with human activities has led to a growing interest in identifying extinction-prone taxa and extinction-promoting drivers. Previous work has identified habitat alterations and invasive species as the major drivers of recent bird extinctions. Here, we extend this work to ask how these human-driven impacts differentially affect extinction-prone taxa, and if any specific driver promotes taxonomic homogenization of avifauna. Like most previous studies, our analysis is based on global information of extinction drivers affecting threatened and extinct bird species from the IUCN Red List. Unlike previous studies, we employ a multivariate statistical framework that allows us to identify the main gradients of variation in extinction drivers. By using these gradients, we show that bird families with the highest extinction risk are primarily associated with threats posed by invasive species, once species richness and phylogeny are taken into account. As expected, the negative impact of invasive species was higher on island species, but our results also showed that it was particularly high in those species with small distribution ranges. On the other hand, mainland species and island species with large ranges tended to be affected by habitat destruction. Thus the impacts of invasive species promote the process of taxonomic homogenization among islands and between islands and continents. Consequently, introduced species may increase biotic homogenization not only directly, as generally believed, but also indirectly through their disproportional impact on endemic species imperilment. © 2009 Elsevier Ltd. All rights reserved.

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Exploring species attributes and site characteristics to assess plant invasions in Spain

Gassó N., Sol D., Pino J., Dana E.D., Lloret F., Sanz-Elorza M., Sobrino E., Vilà M. (2009) Exploring species attributes and site characteristics to assess plant invasions in Spain. Diversity and Distributions. 15: 50-58.
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Doi: 10.1111/j.1472-4642.2008.00501.x

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Aim: Biological invasions are a major component of global change with increasing effects on natural ecosystems and human societies. Here, we aim to assess the relationship between plant invader species attributes and the extent of their distribution range size, at the same time that we assess the association between environmental factors and plant invader species richness. Location: Spain, Mediterranean region. Methods: From the species perspective, we calculated the distribution range size of the 106 vascular plant invaders listed in a recently published atlas of alien plant species in Spain. Range size was used as an estimation of the degree of invasion success of the species. To model variation in range size between species as a function of a set of species attributes, we adopted the framework of the generalized linear mixed models because they allow the incorporation of taxonomic categories as nested random factors to control for phylogenetic relationships. From the invaded site perspective, we determined invader plant species richness as the number of species for each 10 × 10 km Universal Transverse Mercator (UTM) grid. For each grid cell, we estimated variables concerning landscape, topography, climate and human settlement. Then, we performed a generalized linear mixed model incorporating a defined spatial correlation structure to assess the relationship between plant invader richness and the environmental predictors. Results: From the species perspective, wind dispersal and minimum residence time appeared to favour invasion success. From the invaded site perspective, we identified high anthropogenic disturbance, low altitude, short distance to the coastline and dry, hot weather as the main correlates to UTM grid cell invader richness. Main conclusions: According to these results, an increasing importance of man-modified ecosystems and global warming in the Mediterranean region should facilitate the expansion of plant invaders, especially wind-dispersed species, leading to the accumulation of invasive species in some sites (i.e. invasion hot spots). © 2008 The Authors.

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Opinion piece. Revisiting the cognitive buffer hypothesis for the evolution of large brains

Sol D. (2009) Opinion piece. Revisiting the cognitive buffer hypothesis for the evolution of large brains. Biology Letters. 5: 130-133.
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Doi: 10.1098/rsbl.2008.0621

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Why have some animals evolved large brains despite substantial energetic and developmental costs? A classic answer is that a large brain facilitates the construction of behavioural responses to unusual, novel or complex socioecological challenges. This buffer effect should increase survival rates and favour a longer reproductive life, thereby compensating for the costs of delayed reproduction. Although still limited, evidence in birds and mammals is accumulating that a large brain facilitates the construction of novel and altered behavioural patterns and that this ability helps dealing with new ecological challenges more successfully, supporting the cognitive-buffer interpretation of the evolution of large brains. © 2008 The Royal Society.

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A global risk assessment for the success of bird introductions

Vall-Llosera M., Sol D. (2009) A global risk assessment for the success of bird introductions. Journal of Applied Ecology. 46: 787-795.
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Doi: 10.1111/j.1365-2664.2009.01674.x

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Concern over the impact of invasive species has led to the development of risk assessment methodologies to identify potential invaders and prevent future ecological and economic problems. However, developing a risk assessment tool is challenging because of the difficulties of accurately predicting the outcome of species introductions. In this study, we develop a global risk assessment for birds. We integrate two approaches, generalized linear mixed models (GLMM) and hierarchical tree models, to help identify those introductions with the highest risk of establishment success. Past work has shown that the number of individuals released is the main factor influencing establishment success in animals, a conclusion that was supported in our analyses. Establishment success was also higher for species with broader ecological niches and larger brains relative to body size. These features should increase the likelihood of finding an appropriate niche in the region of introduction. The GLMM and tree model predicted the probability of establishment success of birds in Europe and Australia with high accuracy (over 80% of introductions correctly classified). This highlights that establishment risk can be reasonably assessed with information on general habitat use, brain size and the size of the founder population. When compared with an alternative risk assessment tool based on a qualitative ranking, our quantitative approaches achieved higher accuracy with less information. Synthesis and applications. Quantitative risk assessments based on traits related to establishment success are difficult but feasible, providing a useful tool for guiding preventive polices aimed at mitigating the impact of invasive species. © 2009 British Ecological Society.

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