Synergy between habitat fragmentation and climate change: implications for biodiversity in Alpine ecosystems

Abstract

An increase in global temperature accompanied by rapid fragmentation of habitats will lead to greater pressure on biodiversity, with more dramatic impacts expected on high mountain ranges. A new wave of extinction is likely to occur as the ability of species to migrate toward new cooler suitable areas will be hampered by altered landscapes, also the magnitude of species loss will in part depend on species traits, or phenotypic plasticity of individuals which will have to adapt to the changed environmental conditions. In this PhD thesis, I included different models employing altitudinal gradient as a surrogate, to understand how effects determined by climatic variation might or might not exacerbate the negative impact of landscape changes on carabid communities (eastern Italian Alps). Chapter I contains a brief overview of the current body of scientific literature on the main ecological impacts of habitat fragmentation and climate change, and the emerging research related to the response of organisms to the synergistic impacts of these two threats. The aim of Chapter II is to determine whether the effects of rising temperature might enhance the impact of habitat fragmentation on beetle diversity and community structure. Chapter III describes an attempt to assess the existence of simultaneous effects generated by habitat fragmentation and climate change on variation of morphological traits (fluctuating asymmetry and body length) in natural populations of forest-dwelling species Haptoderus unctulatus. Finally, Chapter IV explores if species’ sensitivity to landscape modification and altitude might be maximized or not by a combination of life history traits of ground beetles. In summary, data of carabid assemblages suggest that the impact of rising temperature acting in synergy with land use pressure will move up along the mountainside, inflicting more serious negative impact on species composition, and causing changes in morphological traits of beetle populations particularly accentuated at lowlands. Also, interaction between these two drivers of change will exert a selective pressure on species with certain functional traits, which will result in a greater impact on the beetle assemblages of Alpine ecosystems than either driver acting individually.