Danse

Specialization is a concept based on a broad theoretical framework developed by evolutionary biologists and ecologists. In the past 10 years, numerous studies have reported that – in many contexts – generalist species are “replacing” specialist species. We review recent research on the concept of the ecological niche and species specialization, and conclude that (1) the observed worldwide decline in specialist species is pre- dicted by niche theory, (2) specialist declines cause “functional homogenization” of biodiversity, and (3) such homogenization may be used to measure the impact of disturbance on communities. Homogenization at the community level could alter ecosystem functioning and productivity, as well as result in the deterio- ration of ecosystem goods and services. We propose community-level specialization as an indicator of the impact of global changes (habitat and climate disturbances) on biodiversity.

Each species generally has a close relationship with one or more habitats and can therefore be classified as either specialist or generalist. We studied whether specialist and generalist species are spatially distributed independently of each other. Repeating the analysis for 100 of the most frequent terrestrial bird species recorded over the 10 000 sampled sites of the French Breeding Bird survey, we found that specialists were more abundant if the rest of the community was specialized, and that the inverse was also true. This pattern was far subtler than just a simple dichotomy: most species actually presented a maximum abundance at a value of community specialization similar to their own level of specialization. Bird communities appear very well defined along a specialistgeneralist gradient. We believe this pattern becomes more apparent with habitat degradation. The consequences on both ecological services and community resilience may well be considerable.

Aim Worldwide, functional homogenization is now considered to be one of the most prominent forms of biotic impoverishment induced by current global changes. Yet this process has hardly been quantified on a large scale through simple indices, and the connection between landscape disturbance and functional homogenization has hardly been established. Here we test whether changes in land use and landscape fragmentation are associated with functional homogenization of bird communities at a national scale.

1. Ecological specialization is one of the main concepts in ecology and conservation. However, this concept has become highly context-dependent and is now obscured by the great variability of existing definitions and methods used to characterize ecological specialization. 2. In this study, we clarify this concept by reviewing the strengths and limitations of different approaches commonly used to define and measure ecological specialization. We first show that ecological specialization can either be considered as reflecting species' requirements or species' impacts. We then explain how specialization depends on species-specific characteristics and on local and contingent environmental constraints. We further show why and how ecological specialization should be scaled across spatial and temporal scales, and from individuals to communities. 3. We then illustrate how this review can be used as a practical toolbox to classify widely used metrics of ecological specialization in applied ecology, depending on the question being addressed, the method used, and the data available. 4. Synthesis and applications. Clarifying ecological specialization is useful to make explicit connections between several fields of ecology using the niche concept. Defining this concept and its practical metrics is also a crucial step to better formulate predictions of scientific interest in ecology and conservation. Finally, understanding the different facets of ecological specialization should facilitate to investigate the causes and consequences of biotic homogenization and to derive relevant indicators of biodiversity responses to land-use changes.

One of the most consensual ecological eff ects of the current climate warming is the alteration of the environmental timing of ecosystems. Phenological shifts, at diff erent levels of food webs, are predicted to have major eff ects on species assemblages. Indeed it is unlikely that all species should be able to respond to the phenological shifts of their environment evenly. Yet questions remain about the specifi c traits that predict the ability of a species to track the temporal fl uctuations of its environment. In this study, we use data from the French Constant Eff ort Site ringing program over a 20 years period (1989 -2008) to estimate the ability of 20 common passerine species to adjust their breeding phenology to spring temperature variations. We show that the sensitivity of species breeding phenology to climate relates to species mean migration distance, species ' thermal and habitat niche breadth and brain mass. Species with the broadest ecological and thermal niches, the shortest mean migration distances and the largest brains were most able to adjust their breeding phenology to temperature variations. Our results thus identify long distance migrants and ecological specialists as species that could most suff er from the future expected climate change and suggests phenological adjustment as one possible mechanism underlying the replacement of specialist species by more generalist ones, the so called functional biotic homogenization.

L'obser va tion de l'effet néfaste des acti vi tés humaines sur la nature ne date pas d'hier. Au contraire, dès le XIX e siècle, des groupes civils de natu ra listes, d'artistes et d'ONG se fédèrent afi n d'acti ver des mesures de pré ser va tion de la nature 1 . C'est dans la seconde moi tié du XX e siècle que la commu nauté scien ti fi que quan ti fi e, mesure et éva lue le déclin de la diver sité bio lo gique et la dégra da tion des habi tats à cause des acti vi tés humaines. Les obser va tions pre mières sont alors avé rées en faits scien ti fi ques. Avec l'appa ri tion, au début des années 1980, d'une nou velle dis ci pline uni ver si taire issue de l'éco lo gie scien ti fi que, la bio lo gie de la conser va tion (cf. introduction, p. 9), de nouvelles approches sont déve lop pées pour comprendre et pré dire les méca nismes sous-jacents à l'éro sion de la diver sité bio lo gique, mais aussi pour trou ver des solu tions, pour en pré ve nir ou en atté nuer les impacts néga tifs. Les écologues se mobi lisent alors pour aler ter le grand public et les poli tiques, remet tant en ques tion la sépa ra tion clas sique entre les sphères savantes et poli tiques (Weber 1919). Le point culmi nant de cette cam pagne de sen si bi li sa tion fut atteint lors du Natio nal Forum on BioDiversity de Washington en sep tembre 1. Le photo graphe An sel Adams, acti viste au Sierra Club, la plus vieille orga ni sa tion envi ron nemen ta liste amé ri caine, cher cha tout au long de sa vie à infl u en cer les poli tiques en faveur de la conserva tion de la nature. Avant lui, un autre artiste amou reux de la Yosemite Valley, Carleton Watkins, pré senta au Congrès amé ri cain ses photo graphies, qui jouèrent un rôle pré pon dé rant dans la déci sion du pré sident Abraham Lincoln de signer le clas se ment en parc natu rel de plu sieurs sites excep tion nels dès 1864. Plus récem ment, l'impli ca tion dans la pré ser va tion de la baie géor gienne du groupe des sept, un groupe d'artistes peintres, a abouti en 2004 à son clas se ment par l'UNESCO au patri moine des bio sphères mon diales. Nous aurions éga le ment pu citer l'impli ca tion de l'école pic tu rale de Barbizon dans la pré ser va tion de la forêt de Fon tai ne bleau.

Le terme de « ser vice écosystémique » appa raît dans la commu nauté scienti fi que dans les années 1970 , pour défi nir les pro ces sus et condi tions des éco sys tèmes natu rels qui per mettent le dévelop pe ment des acti vi tés et de la vie humaine (cf. introduction, p. 9). L'éva luation des éco sys tèmes pour le millé naire (Millennium Ecosystem Assessment, MEA), impul sée en 2001 par l'Orga ni sa tion des Nations unies (ONU), a tenté d'iden ti fi er les besoins sociétaux en rela tion avec ces ser vices, ainsi que l'infor ma tion scien ti fi que qu'il fau drait acqué rir pour quan ti fi er les modi fi cations des éco sys tèmes et les consé quences de ces chan ge ments sur le bien-être humain (MEA 2005). Si cette ini tiative était prin ci pa le ment à des ti nation des déci deurs poli tiques, la commu nauté scien ti fi que s'est retrou vée impliquée en tant qu'opé ra teur prin ci pal de cette éva lua tion ; la notion de « ser vice écosystémique » devient le concept clé des poli tiques de pro tec tion de la biodiver sité (cf. A. Larigauderie et al., p. 49).

To garner support for biodiversity from the World's human population, conservation biologists need an open-minded, integrated conservation strategy. We suggest that this strategy should include efforts to (1) preserve existing high quality, diverse ecosystems, (2) remediate impaired systems, (3) balance the needs of people and ecological resources, and (4) engender appreciation of nature and its services. We refer to these four key tenets as reservation, restoration, reconciliation, and reconnection. We illustrate these concepts by presenting the debate surrounding the management of exotic species from an unusual perspective, the benefits of exotic species. By this example we hope to encourage an integrated approach to conservation in which management strategies can be flexible, adjusting to society's needs and the overall goals of conservation.

This paper is an answer to the Caplat and Coutts forum about our previous paper ''The need for flexibility in conservation practices: exotic species as an example''. We precise here why we proposed to consider exotic species as well as indigenous species in the reconnection framework in human-modified environments. One argument is that consistent and understandable arguments must be used in the communication from scientists to the public, in order not to decrease the gap between science and society.

The apple is the most common and culturally important fruit crop of temperate areas. The elucidation of its origin and domestication history is therefore of great interest. The wild Central Asian species Malus sieversii has previously been identified as the main contributor to the genome of the cultivated apple (Malus domestica), on the basis of morphological, molecular, and historical evidence. The possible contribution of other wild species present along the Silk Route running from Asia to Western Europe remains a matter of debate, particularly with respect to the contribution of the European wild apple. We used microsatellite markers and an unprecedented large sampling of five Malus species throughout Eurasia (839 accessions from China to Spain) to show that multiple species have contributed to the genetic makeup of domesticated apples. The wild European crabapple M. sylvestris, in particular, was a major secondary contributor. Bidirectional gene flow between the domesticated apple and the European crabapple resulted in the current M. domestica being genetically more closely related to this species than to its Central Asian progenitor, M. sieversii. We found no evidence of a domestication bottleneck or clonal population structure in apples, despite the use of vegetative propagation by grafting. We show that the evolution of domesticated apples occurred over a long time period and involved more than one wild species. Our results support the view that self-incompatibility, a long lifespan, and cultural practices such as selection from open-pollinated seeds have facilitated introgression from wild relatives and the maintenance of genetic variation during domestication. This combination of processes may account for the diversification of several long-lived perennial crops, yielding domestication patterns different from those observed for annual species.

Face à la « crise écologique» de nouveaux discours politiques se sont développés remplaçant le terme vernaculaire de Nature par celui de Biodiversité. Cependant, que reste-il de ce concept scientifique lorsqu'il est transmis à la société ? Quelle idée de nature perdure ? Dans cette étude nous interrogeons la perception du terme de biodiversité par des collégiens de Seine-Saint-Denis à partir d'ateliers pédagogiques Art-science réalisés en 2010-2011. Abstract : In response to the "ecological crisis" new political views have arisen, replacing the vernacular term of Nature by a new one: Biodiversity. What remains about this scientific concept when it is transmitted to the society? What kind of idea of nature endures ? In this study we question the perception of the term 'biodiversity' in children from Seine-Saint-Denis schools by an original way: Art-science educational workshops conducted in 2010-2011.

RÉSUMÉ: Les chercheurs en écologie sont confrontés à l'urgence d'enjeux sociétaux tels que la réduction rapide des pressions anthropiques sur les milieux naturels. Dans le prolongement naturel de ces travaux, on trouve une forme de médiation particulièrement sensitive, visant à impliquer le public dans une prise de conscience des problématiques en jeu. Nous étudierons l'œuvre Biome, issue de la collaboration entre une écologue, le DrNadkarni, et la compagnie de danse «Capacitor» dirigée par Jodi Lomask.

Biodiversity has reached a critical state. In this context, stakeholders need indicators that both provide a synthetic view of the state of biodiversity and can be used as communication tools. Using river fishes as model, we developed community indicators that aim at integrating various components of biodiversity including interactions between species and ultimately the processes influencing ecosystem functions. We developed indices at the species level based on (i) the concept of specialization directly linked to the niche theory and (ii) the concept of originality measuring the overall degree of differences between a species and all other species in the same clade. Five major types of originality indices, based on phylogeny, habitat-linked and diet-linked morphology, life history traits, and ecological niche were analyzed. In a second step, we tested the relationship between all biodiversity indices and land use as a proxy of human pressures. Fish communities showed no significant temporal trend for most of these indices, but both originality indices based on diet-and habitat-linked morphology showed a significant increase through time. From a spatial point of view, all indices clearly singled out Corsica Island as having higher average originality and specialization. Finally, we observed that the originality index based on niche traits might be used as an informative biodiversity indicator because we showed it is sensitive to different land use classes along a landscape artificialization gradient. Moreover, its response remained unchanged over two other land use classifications at the global scale and also at the regional scale.

Esthétique environnementale, art écologique, les expressions ne manquent pas pour circonscrire un champ de recherche relativement nouveau en France, mais en formation depuis longtemps outre-Atlantique. Il y est question d’esthétisation de l’espace public, ou bien de nouvelles formes de relations entre les arts, la recherche et l’éthique, ou bien encore de la place de l’esthétique dans les mobilisations associatives. Cet article s’inscrit plutôt dans le second courant en tentant un rapprochement entre la biologie de la conservation et les manifestations plurielles d’un art se réclamant de l’engagement écologique. NSS a traité cette question émergente à plusieurs reprises, notamment dans un éditorial intitulé « Artistes et scientifiques : soupçons et espoirs d’interdisciplinarité » (NSS, 16, 3 [2008]), puis à travers d’autres publications, qu’il s’agisse d’études de cas, d’articles de synthèse ou de comptes rendus (NSS, 16, 2 [2008], 122-130 ; NSS, 16, 3 [2008], 279-281 ; NSS, 17, 3 [2009], 285-292). La tentative des auteurs de proposer une catégorisation des créations qui se revendiquent de l’« art écologique » trouvera-t-elle un écho dans le milieu artistique ?

Fungal invasions are increasingly recognized as a significant component of global changes, threatening ecosystem health and damaging food production. Invasive fungi also provide excellent models to evaluate the generality of results based on other eukaryotes. We first consider here the reasons why fungal invasions have long been overlooked: they tend to be inconspicuous, and inappropriate methods have been used for species recognition. We then review the information available on the patterns and mechanisms of fungal invasions. We examine the biological features underlying inva- sion success of certain fungal species. We review population structure analyses, reveal- ing native source populations and strengths of bottlenecks. We highlight the documented ecological and evolutionary changes in invaded regions, including adapta- tion to temperature, increased virulence, hybridization, shifts to clonality and associa- tion with novel hosts. We discuss how the huge census size of most fungi allows adaptation even in bottlenecked, clonal invaders. We also present new analyses of the invasion of the anther-smut pathogen on white campion in North America, as a case study illustrating how an accurate knowledge of species limits and phylogeography of fungal populations can be used to decipher the origin of invasions. This case study shows that successful invasions can occur even when life history traits are particularly unfavourable to long-distance dispersal and even with a strong bottleneck. We con- clude that fungal invasions are valuable models to contribute to our view of biological invasions, in particular by providing insights into the traits as well as ecological and evolutionary processes allowing successful introductions.

Summary
1. Generalist species are more successful than specialists in anthropogenically modified envi- ronments or in environments in which they have been introduced, but the nature of the link between generalism and establishment success is unclear.
2. A higher feeding innovation rate has previously been reported in habitat generalist birds from North America. By allowing them to exploit new resources, this higher feeding innovation rate might explain the generalists’ advantage. This result might be due to generalists being more likely to find new resources because they are exposed to more diverse environmental conditions. Alternatively, they might differ from specialists in other traits, in particular cognitive skills that might allow them to innovate more complex food searching and handling techniques.
3. To test these hypotheses, we separated avian feeding innovations into a ‘technical’ (novel searching and handling behaviour) and a ‘food type’ (incorporation of a new food in a spe- cies’ diet) category. Technical innovations, but not food type innovations, have previously been shown to correlate with avian brain size, suggesting they reflect cognitive ability. We used a world-wide data base of 2339 feeding innovations recorded in the literature, covering a total of 765 avian species and assessed the correlations between brain size and feeding innova- tion rates on one side and habitat and diet generalism on the other.
4. Habitat generalism was positively related with food type innovation rate, but not technical innovation rate or brain size. This suggests that habitat generalist species are more likely to incorporate new food types in their diet because of higher chances to find new food resources in their environment, or of a higher opportunism, but not enhanced cognitive skills. In con- trast, diet generalist species had higher food type and technical innovation rates, as well as larger brains, suggesting that cognitive skills might help species expand their diet breadth or that an increase in diet breadth might favour the evolution of enhanced cognitive abilities.
5. Our results provide new insights into the nature of the generalists’ advantage in the face of environmental changes, and suggest that dietary and habitat generalism are different, but con- vergent, routes to feeding flexibility and adaptation to changed environments.