Exotic Fish in Exotic Plantations: A Multi-Scale Approach to Understand Amphibian Occurrence in the Mediterranean Region

Abstract

Globally, amphibian populations are threatened by a diverse range of factors including habitat destruction and alteration. Forestry practices have been linked with low diversity and abundance of amphibians. The effect of exotic Eucalyptus spp. plantations on amphibian communities has been studied in a number of biodiversity hotspots, but little is known of its impact in the Mediterranean region. Here, we identify the environmental factors influencing the presence of six species of amphibians (the Caudata Pleurodeles waltl, Salamandra salamandra, Lissotriton boscai, Triturus marmoratus and the anurans Pelobates cultripes and Hyla arborea/meridionalis) occupying 88 ponds. The study was conducted in a Mediterranean landscape dominated by eucalypt plantations alternated with traditional use (agricultural, montados and native forest) at three different scales: local (pond), intermediate (400 metres radius buffer) and broad (1000 metres radius buffer). Using the Akaike Information Criterion for small samples (AICc), we selected the top-ranked models for estimating the probability of occurrence of each species at each spatial scale separately and across all three spatial scales, using a combination of covariates from the different magnitudes. Models with a combination of covariates at the different spatial scales had a stronger support than those at individual scales. The presence of predatory fish in a pond had a strong effect on Caudata presence. Permanent ponds were selected by Hyla arborea/meridionalis over temporary ponds. Species occurrence was not increased by a higher density of streams, but the density of ponds impacted negatively on Lissotriton boscai. The proximity of ponds occupied by their conspecifics had a positive effect on the occurrence of Lissotriton boscai and Pleurodeles waltl. Eucalypt plantations had a negative effect on the occurrence of the newt Lissotriton boscai and anurans Hyla arborea/meridionalis, but had a positive effect on the presence of Salamandra salamandra, while no effect on any of the other species was detected. In conclusion, eucalypts had limited effects on the amphibian community at the intermediate and broad scales, but predatory fish had a major impact when considering all the scales combined. The over-riding importance of introduced fish as a negative impact suggests that forest managers should prevent new fish introductions and eradicate fish from already-occupied ponds whenever possible.

Biodiversidade aquática e qualidade de rios em eucaliptais certificados no centro de Portugal

“…Relembre-se que a galeria ripícola se apresenta bem desenvolvida na ribeira da Foz, com elevado ensombramento e presença de folhada no solo. Adicionalmente, um estudo recente demonstra um efeito positivo da presença de plantações de eucalipto a larga escala sobre a probabilidade de ocorrência desta espécie na região do centro interior de Portugal (CRUZ et al, 2015). Esse facto sugere a presença de galerias ripícolas mais bem preservadas em plantações de eucaliptos do que noutros usos do solo.…”

“…As densidades obtidas para ambas as espécies são muito elevadas. A forte presença de L. boscai nesta ribeira não é assim consistente com um estudo recente conduzido no centro interior de Portugal que sugere uma relação negativa entre a presença de plantações de eucalipto e a probabilidade de ocorrência de L. boscai (CRUZ et al, 2015).…”