The strength of species interactions modifies population responses to environmental variation in competitive communities

Spatio-Temporal Environmental Correlation and Population Variability in Simple Metacommunities

“…When two species that are differently adapted to a common environmental variable come to interact, the arising between-species environmental correlation ( ρ S ) – ρ S  = 1 means that responses are identical, ρ S  = 0 means responses are independent, and ρ S  = –1 indicates completely opposite responses – can affect population variability in closed communities [2], [14], [15], [20]. In simple competitive communities increasing ρ S dampens undercompensating population fluctuations, whereas overcompensating populations tend increase in variability [14], [15], [21]. In multi-trophic food webs increased ρ S can be associated with lower population variability [22], as well as increased food web persistence [23].…”

Environmental weakening of trophic interactions drives stability in stochastic food webs

“…Environmental characteristics that are known to affect food web dynamics include the temporal mean (Vasseur and McCann, 2005), fluctuation amplitude (Gouhier et al, 2010;Vasseur and Fox, 2007), spectral colour (Gonzalez and De Feo, 2007;Greenman and Benton, 2005a), and the similarity of species environmental responses (Ripa and Ives, 2003;Ruokolainen and Ripa, 2012;Thébault and Loreau, 2005). Here we concentrate on analysing the effects of varying environmental amplitude (s 2 ) and colour (γ).…”

“…The period length of the consumer-resource cycle is influenced by the strength of interactions between the consumer and the resources, which in turn determines the location of the variance maximum along varying environmental colour (Ripa and Ives, 2003). Ruokolainen and Ripa (2012) suggested that the interaction strength could shift the consumer and resource variance maxima with respect to each other, which could explain why Vasseur and McCann (2005) observed maximum variability at an intermediate noise colour only for the resource population.…”

“…Further, how environmental reddening affects population dynamics depends on whether noise affects resource productivity (r i ) or consumer resource intake (I i ). Uncorrelated (between-species), reddened environmental variation amplifies fluctuations in the densities of competitors (Ruokolainen and Fowler, 2008;Ruokolainen and Ripa, 2012). In addition to the fact that the consumer couples more strongly to the resource that is favoured by the environment (having a relatively high growth rate and carrying capacity, which excites the consumer-resource cycle; Rip and McCann, 2011), this explains why environmental reddening destabilises food web dynamics under stochastic r i ′s.…”

“…From these simplified model systems it is known that the system-level consequences of environmental forcing depend on which nodes in the food web are being affected by external perturbations (Greenman and Benton, 2005a). The impact of environmental variation can also depend on the strength of species interactions within the food web (Ripa and Ives, 2003;Ruokolainen and Ripa, 2012;Ruokolainen et al, 2009b) and temporal characteristics of environmental fluctuations, such as variance and colour (Ruokolainen et al, 2009a). Variation in the colour (referring to the dominant mode of fluctuations; blue for fast and red for slow) of environmental fluctuations can have a different effect on species embedded in food webs, depending on their trophic position (affecting their demographic characteristics) Benton, 2005a, 2005b).…”