Demografía y ecología evolutiva del subarbusto carnívoro Drosophyllum lusitanicum (L.) Link. (Drosophyllaceae)

Abstract

Natural disturbances occur in various ecosystems and have resulted in the evolution of life histories to buffer or even benefit from disturbance regimes. However, human activities increasingly interact with natural disturbances, posing potentially significant threats to the viability of disturbance-adapted species and therefore causing biodiviersity loss. With fires regularly affecting 50 % of the Eath’s surface, such compounded effects of disturbance interactions are particularly prominent in fire-prone ecosystems. Using the rare carnivorous subshrub Drosophyllum lusitanicum (Drosophyllaceae), endemic to Mediterranean heathlands under increasing human pressure in the southwestern Iberian Peninsula and northern Morocco, this doctoral work illustrates how interactions between fire and small-scale human disturbances affect population dynamics and the potential evolutionary trajectory of populations. Greenhouse and in-situ field experiments and stochastic demographic models quantified biological and ecological characteristics of the study species that could be linked to an important, positive role of recurrent fires in population dynamics. At the same time, population censuses across the species range revealed that small-scale human disturbances related to removal of competitively superior shrub neighbors significantly increased the probability of population occurrence and the abundance of several life-cycle stages. Subsequently, stochastic integral projection models confirmed that moderate interactions between human and fire disturbances may significantly improve species viability in the absence of fires. However, a crucial finding of this work was that frequent human disturbances as well as frequent interactions between fires and chronic vegetation removal may be detrimental to population viability because the two fundamentally different disturbance types exert opposing selection pressures on populations. These findings are of potentially great importance for the management of disturbance-adapted species because they highlight the importance of including compounding effects of environmental drivers into demographic models and the need to consider the local disturbance history when designing conservation strategies of species exposed to various disturbance types.