Invasive species and habitat degradation in Iberian streams: an analysis of their role in freshwater fish diversity loss

Abstract

Abstract. Mediterranean endemic freshwater fish are among the most threatened biota in the world. Distinguishing the role of different extinction drivers and their potential interactions is crucial for achieving conservation goals. While some authors argue that invasive species are a main driver of native species declines, others see their proliferation as a co-occurring process to biodiversity loss driven by habitat degradation. It is difficult to discern between the two potential causes given that few invaded ecosystems are free from habitat degradation, and that both factors may interact in different ways.Here we analyze the relative importance of habitat degradation and invasive species in the decline of native fish assemblages in the Guadiana River basin (southwestern Iberian Peninsula) using an information theoretic approach to evaluate interaction pathways between invasive species and habitat degradation (structural equation modeling, SEM). We also tested the possible changes in the functional relationships between invasive and native species, measured as the per capita effect of invasive species, using ANCOVA.We found that the abundance of invasive species was the best single predictor of natives' decline and had the highest Akaike weight among the set of predictor variables examined. Habitat degradation neither played an active role nor influenced the per capita effect of invasive species on natives. Our analyses indicated that downstream reaches and areas close to reservoirs had the most invaded fish assemblages, independently of their habitat degradation status. The proliferation of invasive species poses a strong threat to the persistence of native assemblages in highly fluctuating environments. Therefore, conservation efforts to reduce native freshwater fish diversity loss in Mediterranean rivers should focus on mitigating the effect of invasive species and preventing future invasions.

Differential population responses of native and alien rodents to an invasive predator, habitat alteration and plant masting

“…Our analysis revealed that habitat alteration can decrease the carrying capacity of endemic rats and halt the recovery of endemics from suppression by an invasive predator (figure 3), but the interaction effect with predatory impact was not significant (table 1). This finding is consistent with those of previous studies focusing on the interaction effects of invasive species and habitat alteration [62,63]. Importantly, as habitat alteration intensified, the relative rank of the carrying capacity of the black rat increased (figure 3), probably because the black rat can eat agricultural crops and rubbish, which are abundant in human-dominated landscapes, whereas endemic rats are purely forest-dwellers.…”

Range Expansion of Ambrosia artemisiifolia in Europe Is Promoted by Climate Change

“…Some invasive species may be promoted by climate change (e.g., [8]) due to characteristics that facilitate rapid range shifts (e.g., short time to maturity and low seed mass) and due to their broad climatic tolerances [9]. The introduction of invasive species is often supported by human activities, for example, by affecting natural habitats with global trade, transport, and new transport vectors involved [7,10]. For the successful establishment of invasive plant species evolutionary factors (e.g., the potential for rapid adaptation to novel environmental conditions) play an important role [7,11].…”

Factors influencing tropical Island freshwater fishes: species, status, threats and conservation in Hainan Island

“…A number of organisms (plants, amphibians, mammals and birds) have been threatened by habitat degradation on Hainan Island Xie et al, 2007;Zhang et al, 2010;Meng et al, 2011). Research has shown that habitat degradation leads to loss of fish biodiversity in other regions (Kruk, 2007;Hermoso et al, 2011), however little is known about the actual negative impacts on native freshwater fish caused by habitat degradation on Hainan Island.…”