Presència d'Ephydatia fluviatilis (Porifera: Spongillidae) en un torrent de Mallorca

Abstract not availabl

El perill d'introduir espècies exòtiques a les Illes: el cas del mufló i del francolí a Mallorca

S'assenyalen les causes i conseqüències de la fragilitat dels ecosistemes insulars envers espècies no nadives (exòtiques), i en particular, els efectes que introduccions de mamífers herbívors (com és el mufló) i d'ocells (com el francolí) poden tenir sobre la vegetació i sobre l'ecosistema en general. Els herbívors com cabres, ovelles i muflons han mostrat, en diferents llocs del món, tenir un efecte negatiu sobre les espècies vegetals (especialment les endèmiques) i la fauna associada a elles (inclosos els ocells) en destruir l'hàbitat. Per altra banda, la introducció d'espècies d'ocells exòtics comporta sovint una sèrie de riscs, especialment per a l'avifauna nadiva (per exemple, malalties, possibilitat de desplaçar a altres espècies). Se recomana una gestió que no inclogui aquest tipus de translocacions (ni d'espècies, ni de subespècies, ni de varietats noves), i que s'encamini més aviat cap a una erradicació dels tàxons exòtics ja existents a les Illes Balears que estiguin ajudant a destruir els hàbitats naturals i a evitar la seva regeneració, per més castigats per la mà de l'home que aquests ja hagin estat.The rises of introducing exotic species in islands: the case of the mouflon and the black francolin in Mallorca. The causes and consequences of the fragility of insular ecosystems towards the introduction of exotic species are pointed out, in particular the effects that the introduction of herbivorous mammals (such as the mouflon) and birds (such as the black francolin) can have on the vegetation and on the ecosystem in general. Herbivores, like goats, sheep and mouflons have shown, in different arcas of the world, to have a negative effect on the plant species (especially the endemic ones) and on the fauna associated to them (including birds) because they destroy the habitat. On the other hand, the introduction of exotic bird species often implies different risks, especially for the native avifauna (for instance, diseases, possibility of displacing other species). A management that does not include this kind of translocations (of species, subespecies, or varieties) is recommended. It is suggested that efforts should go towards an erradication of the exotic taxons that already exist on the Balearic Islands and that are being detrimental to the natural habitats by precluding their regeneration, even in those habitats already damaged due to human activities

Resultats preliminars sobre el consum de fruits per ocells a l'illa de Cabrera (Illes Balears)

S'examina, des d'un punt de vista purament qualitatiu, el consum de fruits carnosos (baies) per algunes espècies d'ocells a l'illa de Cabrera. L'alta disponibilitat de fruits a l'illa la fan una font important d'aliment per a bastants espècies d'ocells, sigui per una temporada curta com és el pas migratori de la tardor, sigui per tot l'hivern. Els busquerets, Sylvia spp., i els tords, Turdus spp. són els més frugívors. Sylvia atricapilla és el frugívor per excel.lència, consumint gairebé exclusivament fruits durant la tardor i incloent la major diversitat de fruits en la seva dieta. Durant la primavera/ estiu, els fruits d'algunes espècies com Rhamnus ludovici-salvatoris i Ephedra fragilis poden també ser importants, sobretot com a font d'aigua, per a espècies que crien a Cabrera com Monticola solitarius, Sylvia sarda i S. cantillans.Preliminary results on the fruit consumption by birds in Cabrera Island (Balearic Archipelago). The consumption of fleshy fruits by different species of birds is examined, qualitatively, in the island of Cabrera. The high availability of fruits in this island makes it an important source of food for some species of birds, either for a short period as the autumn migration or for the whole winter. Warblers, Sylvia spp., and thrushes, Turdus spp. are the most fru g ivorous birds. Sylvia atricapilla is the frugivore for excellence, with a diet consisting, during the fall period, almost exclusively of fruits, and including the greatest diversity of plant species. During spring and summerperiods, the fruits of several species, as Rhamnus ludovici-salvatoris and Ephedra fragilis, can also be very important, mainly as a source of water, for some birds that breed in Cabrera as Monticola solitarius, Sylvia sarda and S. cantillans

El paper dels mutualismes plantaanimal als ecosistemes insulars

En el present treball s'examina la importància ecològica a les illes de les interaccions mutualistes entre plantes i animals, en particular, el paper que la pol·linització i la dispersió de llavors per aquests juga en la estructura de les comunitats i en el manteniment de la diversitat biològica. S'enumeren una colla d'exemples d'interaccions peculiars que s'han originat en diferents illes arreu del món aixi com les conseqüències ocasionades al trencar-se aquests mutualismes degut a diferents causes com són la destrucció de l'hàbitat, la introducció d'espècies exòtiques o una caça excessiva. S'examinen també els factors que cal considerar a l'hora d'avaluar el risc d'extinció de plantes que han perdut els seus animals mutualistes i els mecanismes que tenen per a compensar aquestes pèrdues. Finalment, es tracten els sistemes de reproducció de les plantes a les illes i els mecanismes que han evolucionat per a evitar la dependència absoluta dels animals en aquests ecosistemes. Es conclou que en qualsevol programa de conservació cal incorporar l'estudi i la facilitació de les interaccions mutualistes. No n'hi ha prou en preservar la diversitat genètica i el potencial evolutiu, si no que s'han de conservar també els sistemes i processos que han evolucionat durant molt de temps i segueixen evolucionat. A les illes s'hi troben unes taxes relativament altes d'endemismes. Amb cada espècie endèmica que se'n va, se'n poden anar també altres espècies associades a ella, i per tant, la diversitat biològica total es pot veure molt negativament afectada.In the present study I examine the ecological importance of the mutualistic interactions between plants and animals in island ecosystems. In particular, I examine the role that pollination and seed dispersal by animals play on community structure and on the maintenance of biological diversity. A number of examples of peculiar interactions that have originated in different islands around the world is examined as well as the consequences of mutualism disruption due to different reasons such as habitat destruction, introduction of exotic species or an excesive hunting. I also examine the factors that need to be considered to evaluate the extinction risk of plants that have lost their animal mutualists and the mechanisms that they possess to compensate for such losses. Finally, plant breeding systems in islands and the mechanisms evolved to avoid the absolute dependence upon animals in these ecosystems are also considered. It is concluded that in any conservation program we need to incorporate the study and facilitation of mutual is tic interactions. It is not enough to preserve the genetic diversity and the evolutionary potential, but also the systems and processes that have evolved for a long time and continue to evolve. In islands we find relatively high rates of endemic taxa. Along each species that is gone, several other species associated with it may also disappear, and thus, the total biological diversity can be negatively affected

A methodology for the evaluation of the biodiversity interest present in three terrestrial ecosystems in the Palma beach system

An evaluation method for three terrestrial areas in the Palma beach system, Mallorca, Balearic Islands, Western Mediterranean is presented. Ses Fontanelles, Son Verí and Torrent dels Jueus are three fragments of semi-natural vegetation located within a very highly modified and exceedingly fragmented landscape. The Ratcliffe criteria (1977) were used as the basis for developing a multi-criteria decision making framework in order to score biodiversity value at sites. Ses Fontanelles is considered to be the area with the greatest biodiversity interest, followed by Son Verí and finally Torrent dels Jueus. As biodiversity value is an important factor in conservation planning, it is hoped that the information presented in this study will assist in guiding urban planning decisions in this and similar areas

Contrasting Partners' Traits of Generalized and Specialized Species in Flower-Visitation Networks

Much ecological research has focused on trying to understand why species are generalized or specialized in their interactions and how networks develop in a certain environment. It is now well known that traits such as phenology and abundance of a species are important determinants of its generalization level (i.e., number of different interactions or links to other species). Less information is available, however, on whether generalized and specialized species differ in particular traits of their interacting partners. Such partners might differ, for instance, in abundance and/or in the diversity of functional groups they belong to. Moreover, species might exhibit shifts through time (e.g., flowering season) in their partners' traits, though we know close to nothing on whether these changes do indeed occur. Assessing how such network links in both types of species are established is important for a better understanding of how different types of disturbance can affect community dynamics. Using data from four quantitative flower-visitation networks and independent measures of flower availability obtained when recording interactions, we test for such differences between species which have been previously categorized according to two specialization indexes: (1) number of partners (links), also named linkage level; this is a qualitative index and (2) complementary specialization d', named here selectiveness level; this is a quantitative index. We found that: (1) species with low linkage levels mainly interact with common species in the community whereas generalized species interact with a greater heterogeneity of partner's abundances and functional richness, (2) both selective and opportunistic species (with high and low d', respectively) interact with a similarly high functional richness (number of functional groups or families) of partners, and (3) generalized species are the only ones showing shifts along the season in their partners' traits, driven by changes in community species composition. The risk of extinction in front of a disturbance is generally expected to be highest for specialized species (with few partners) and selective species (which visit non-abundant or scarce partners). However, our findings show that by linking to abundant and/or to functionally diverse partners, respectively, these species may be maintained in the community and be less vulnerable to disturbances.This work was financially supported by the project CGL2010-18759BOS from Spanish Ministry of Science and Innovation. RCU received FPI grant from the Spanish Ministry of Economy and Competitiveness.Peer Reviewe

Extinction-induced community reorganization in bipartite networks

We study how the community structure of bipartite mutualistic networks changes in a dynamic context. First, we consider a real mutualistic network and introduce extinction events according to several scenarios. We model extinctions as node or interaction removals. For node removal, we consider random, directed and sequential extinctions; for interaction removal, we consider random extinctions. The bipartite network reorganizes showing an increase of the effective modularity and a fast decrease of the persistence of the species in the original communities with increasing number of extinction events. Second, we compare extinctions in a real mutualistic network with the growth of a bipartite network model. The modularity reaches a stationary value and nodes remain in the same community after joining the network. Our results show that perturbations and disruptive events affect the connectivity pattern of mutualistic networks at the mesoscale level. The increase of the effective modularity observed in some scenarios could provide some protection to the remaining ecosystem

A methodology for the evaluation of the biodiversity interest present in three terrestrial ecosystems in the Palma beach system

An evaluation method for three terrestrial areas in the Palma beach system, Mallorca, Balearic Islands, Western Mediterranean is presented. Ses Fontanelles, Son Verí and Torrent dels Jueus are three fragments of semi-natural vegetation located within a very highly modified and exceedingly fragmented landscape. The Ratcliffe criteria (1977) were used as the basis for developing a multi-criteria decision making framework in order to score biodiversity value at sites. Ses Fontanelles is considered to be the area with the greatest biodiversity interest, followed by Son Verí and finally Torrent dels Jueus. As biodiversity value is an important factor in conservation planning, it is hoped that the information presented in this study will assist in guiding urban planning decisions in this and similar areasEs presenta un mètode d'avaluació de tres àrees terrestres en el sistema de la Platja de Palma, Mallorca, Illes Balears, Mediterrània Occidental. Ses Fontanelles, Son Verí i el Torrent dels Jueus són tres fragments de vegetació semi-natural ubicat dins d'un paisatge molt modificat i fragmentat. Els criteris de Ratcliffe (1977) es van utilitzar com a base per al desenvolupament d'un marc de decisió multicriteri per tal de valorar la diversitat biològica en aquests llocs. Ses Fontanelles és considerada com la zona amb el major interès per a la biodiversitat, seguit per Son Verí i finalment pel Torrent dels Jueus. Com que el valor de la biodiversitat és un factor important en la planificació de la conservació, s'espera que la informació presentada en aquest estudi ajudi a prendre decisions sobre planificació urbana en aquesta i altres àrees semblant