Novel communities from climate change

Abstract

Climate change is generating novel communities composed of new combinations of species. These result from different degrees of species adaptations to changing biotic and abiotic conditions, and from differential range shifts of species. To determine whether the responses of organisms are determined by particular species traits and how species interactions and community dynamics are likely to be disrupted is a challenge. Here, we focus on two key traits: body size and ecological specialization. We present theoretical expectations and empirical evidence on how climate change affects these traits within communities. We then explore how these traits predispose species to shift or expand their distribution ranges, and associated changes on community size structure, food web organization and dynamics. We identify three major broad changes: (i) Shift in the distribution of body sizes towards smaller sizes, (ii) dominance of generalized interactions and the loss of specialized interactions, and (iii) changes in the balance of strong and weak interaction strengths in the short term. We finally identify two major uncertainties: (i) whether largebodied species tend to preferentially shift their ranges more than small-bodied ones, and (ii) how interaction strengths will change in the long term and in the case of newly interacting species.

Network complexity and species traits mediate the effects of biological invasions on dynamic food webs

“…If the former case is the norm, we should expect species to be bigger if they are going to thrive in novel communities, as has been shown the case in, for example, mountain ecosystems (Lurgi et al, 2012b). Our results agree with previous findings that suggest that novel communities will be biased toward species with larger body sizes that are easily capable of invading native communities (Lurgi et al, 2012a).…”

“…Bigger species (or those increasing their metabolic demands) will be generally more successful invaders although they will find it harder to invade communities that are loosely connected. Under the current global change scenario, communities are probably getting simpler due to the loss of interactions, although in some cases the opposite might be true (Lurgi et al, 2012a). If the former case is the norm, we should expect species to be bigger if they are going to thrive in novel communities, as has been shown the case in, for example, mountain ecosystems (Lurgi et al, 2012b).…”

Climate change impacts on body size and food web structure on mountain ecosystems

“…Expanders did not have wider diet breadths than non-expanders, but they were larger and were attacked by fewer predators. The first pattern disagrees with studies stating that more generalist consumers are good candidates to firstly move upwards [24,46,50]. Actually, specialists are considered particularly vulnerable to extinction as a result of environmental change [50][51][52][53].…”

Climate change in size-structured ecosystems

“…The resulting shifts in the size structure of the community towards populations of smaller individuals can induce trophic cascades that modify biomass distribution across size classes and trophic levels [14]. These modifications can lead to the loss of existing interactions and the emergence of novel ones, leading to different food-web structures [7]. Hence, understanding the interplay of direct warming effects with indirect effects of modified community size structures may provide a generalized understanding of climate change impacts on natural communities.…”

“…This theme issue integrates novel approaches for addressing the consequences of climate change in complex, sizestructured ecosystems. This includes the development of novel concepts [7][8][9][10], model analyses [11][12][13] and empirical studies in marine [14,15], freshwater [16,17] and terrestrial ecosystems [18][19][20][21][22]. In the following, we will introduce the framework of this theme issue by describing the complexity and the size structure of natural communities and how they might interact with climate change in determining top-down or bottom-up control, community stability and spatial processes.…”