Salta al contingut principal

Interference competition in a threatened seabird community: A paradox for a successful conservation


It is often assumed that conservation actions targeting a threatened community (e.g. habitat protection)
will result in similar benefits for all species. However, complex interactions between species, such as interference competition, may result in displacement of subordinate, vulnerable species. We analysed here the spatio-temporal population dynamics of a threatened seabird community since the protection in the 1980s of several breeding sites at the Ebro Delta, western Mediterranean, Spain during 1980–2007. Competition for the most suitable patches was governed by body size, with smaller species avoiding associations with larger, dominant species. We tested whether the density increase of the larger species (yellow-legged gull Larus michahellis and Audouin’s gullLarus audouinii) at La Banya (the highest quality patch within the Delta) affected species diversity at the local level. As expected, such diversity decreased, resulting also from the colonisation of other sites by smaller species, some abandoning the former area. The conservation paradox appeared because the interference competition was dominated not only by the largest species of the community, the yellow-legged gull, which is sometimes considered a pest species, but also by the vulnerable Audouin’s gull, a flagship species which has ca. 65% of the total world population at La Banya. Nevertheless, the availability of alternative patches within the Ebro Delta ensured a high biodiversity at regional scale.
Results highlight the role of turnover of competing species within a community in ecosystem function and stability, and the importance of alternative sites and dispersal abilities for the conservation of vulnerable
communities.

Oro, D et al. (2009) Biological Conservation 142 
Etiquetes de comentaris:

Comentaris

Publica un comentari a l'entrada

Entrades populars d'aquest blog

An analysis of habitat distribution and associations in theOdonata of theBalearic Islands, Spain

 Spatial structure of the odon. community is analysed. The different abundance of the spp. and their most characteristic habitats in the islands are indicated. The reproduction of 19 spp. on the Balearic Islands is confirmed. Coenagrion scitulum is recorded for the first time from the archipelago. The associations of spp. existing on each of the islands were established by meansof factoranalysis (correspondence analysis); a total of9 associations are defined. This study has been made on larvae exclusively. Sympetrum striolatum is the most abundant sp. in the Balearic Islands. Previous records are discussed. García-Aviles, J,   Puig, M.A,  Soler, A.G. & Ferreras-Romero, M. (1995)  Odonalologica 24(3)
Publica un comentari a l'entrada
Més informació

Not so naïve: Ibiza wall lizards acquired the ability to recognize alien snakes in a few years

Alien predators may impose a great threat to naïve preys. Podarcis pityusensis lizards live in Ibiza, a snake-free island until 2003. We studied lizards’ discrimination of scents of two invader snakes: one that predates on lizards, Hemorrhois hippocrepis, and another that does not, Rhinechis scalaris. We compared two populations of P. pityusensis: one from the main island of Ibiza, which coexists with both snakes, and another from the close snake-free islet of Sal Rossa. Lizards from Ibiza recognized the scent of H. hippocrepis and responded with clear antipredator behaviours. However, they reacted to the scent of R. scalaris similarly than to the odorless and the pungent controls. Lizards from Sal Rossa did not recognize any snake species. Thus, lizards can rapidly acquire the ability to react to a totally novel type of predator. There are two possible explanations: (1) rapid evolution of antipredator behavior, and (2) the ability of lizards to learn how to avoid new predators. There ...
Publica un comentari a l'entrada
Més informació

Sobre las ginetas de la isla de Ibiza (Genetta genetta isabelae n.ssp.)

Las Ginetas de Ibiza habían sido consideradas hasta ahora como G. g. balearica. El estudio de 50 cráneos y 38 pieles (Cuadro 1) permite, sin embargo, caracterizarlas como una nueva subespecie, Genetta genetta isabelae n. ssp., debido fundamentalmente a su pequeño tamaño. Se consideran caracteres con valor diagnóstico LCB (longitud cóndilo-basal) ≤85 mm. LM (longitud de la mandíbula) ≤60 mm. LPm⁴ (longitud de la carnicera superior) ≤8mm. M² (segundo molar superior) muy reducido. Las manchas del pelaje son negras o marrones oscuras con abundantes pelos de color rojizo leonado. El dimorfismo sexual es poco marcado (Fig. 3). Las medidas de G. g. isabelae (Cuadros 2 y 3) difieren significativamente de las restantes poblaciones del oeste de Europa y norte de África. Estas muestran por su parte una variación clinal de tamaño, desde Francia, donde son más pequeñas, al norte de África donde son más mayores, a través de la Península Ibérica y Mallorca (Cuadros 4 y 5; Fig. 4, 5, 6 y 7). Las Ginet...
Publica un comentari a l'entrada
Més informació