Research Highlights (2010, 2009)



Topic: linking density, productivity and population trends in an endangered species

* Whether regional population density is a good indicator of environmental quality according to demographic variables such as breeding success or short-term population trends is controversial. In this paper we analyze the interrelationships among regional population density, breeding success and recent population trends of an endangered species, Bonelli’s eagle in the Iberian Peninsula.

* Breeding success was higher and population decrease was lower in those areas where the population density of Bonelli’s eagle was greater. Overall, these results suggest that population density in this endangered species of large home-range is a good indicator of environmental quality and reproductive output, and that peripheral populations occupy low-suitability areas with lower breeding success, where negative short-term population trends are more likely. Read more [… y más]


Topic: partial least squares regression as an alternative to current regression methods used in ecology

            * When analyzing ecological patterns, the variation in the response variables is established as a function of several predictors (i.e., multiple regression analysis, MR). An alternative to the classical regression approach is partial least squares regression analysis (PLSR), with a high potential utility in ecological studies. This statistical technique is particularly well suited to analyzing a large array of related predictor variables (i.e. not truly independent), with a sample size not large enough compared to the number of independent variables, and in cases in which an attempt is made to approach complex phenomena or syndromes that must be defined as a combination of several variables obtained independently.

            * A simulation experiment was carried out to compare PLSR with MR, and with a combination of principal component analysis and multiple regression (PCA+MR), varying the number of predictor variables and sample sizes. PLSR models explained a similar amount of variance to those results obtained by MR and PCA+MR. However, PLSR was more reliable than other techniques when identifying relevant variables and their magnitudes of influence, especially in cases of small sample size and low tolerance. Read more.


Topic: effects of vegetation restoration on bird assemblages of Mediterranean abandoned croplands

            * Habitat changes induced by land abandonment or active pine plantations determine bird distribution patterns in large areas of the Mediterranean Basin.

            * Pine plantations increased local bird species richness (mainly generalist woodland birds) as they favored several Paleartic, Holarctic and European species. Secondary succession (holm oak) provided more favorable habitats for species of conservation concern in the European context.

            * The number of forest species increased with vegetation maturity in both restoration trajectories, but especially in pine plantations. Bird species inhabiting pine plantations had broader habitat breadth at the regional level than those inhabiting secondary shrublands and woodlands. Read more.