1. Understanding the combined effects of global and local stressors is crucial for conservation and management, yet challenging due to the different scales at which these stressors operate. Here we examine the effects of one of the most pervasive threats to marine biodiversity, ocean warming, on the early life stages of the habitat-forming macroalga Cystoseira zosteroides, its long-term consequences for population resilience and its combined effect with physical stressors.
2. First, we performed a controlled laboratory experiment exploring the impacts of warming on early life stages. Settlement and survival of germlings were measured at 16ºC (control), 20ºC and 24ºC and both processes were affected by increased temperatures. Then, we integrated this information into stochastic, density-dependent integral projection models (IPM).
3. Recovery time after a minor disturbance significantly increased in warmer scenarios. The stochastic population growth rate (λs) was not strongly affected by warming alone, as high adult survival compensated for thermal-induced recruitment failure. Nevertheless, warming coupled with recurrent physical disturbances had a strong impact on λs and population viability.
4. Synthesis: The impact of warming effects on early stages may significantly decrease the natural ability of habitat-forming algae to rebound after major disturbances. These findings highlight that, in a global warming context, populations of deep-water macroalgae will become more vulnerable to further disturbances, and stress the need to incorporate abiotic interactions into demographic models.
CzIPM
R code to estimate the recovery time for Cystoseira zosteroides populations after a major disturbance at different temperature scenarios treatments. In addition, stochastic population growth rate (λs) and quasi-extinction probability at increasing frequency of two major disturbances at increasing temperature scenarios. These analyses correspond to the figures 4 and 5 of Capdevila et al. 2018 JEcol.
MixedEffectsparams
Parameter values needed for the Integral Projection Models used to model the life cycle and population dynamics of Cystoseira zosteroides. This includes seven demographic processes: 1.survival (σ), 2.growth (γ), 3.fertility (φ), 4.recruits per capita (δ(N)), 5.probability of settlement of recruits (ε), 6.early survival of recruits (σs) and 7.recruits size probability distribution.
IPMFunctions
Functions required to run the CzIPM.R script. This script contains the description of the growth, survival and fecundity functions used to build the IPMs.1. The best-fitted model for survival (σ) was a logistic mixed effect model including size as fixed factors and population nested in years as a random factor. 2. For growth (γ), the best-fitted model was a linear mixed effect model, with size as fixed factor and population nested in year as random factor. 3. Fertility (φ(z)), was estimated as the relation between reproductive status (reproductive vs. non-reproductive) and size with a binomial regression. 4. Recruitment per capita (δ(N)) is density-dependent in C. zosteroides (Capdevila et al., 2015), so a generalized linear model with Poisson error distribution and a log-link function was fitted, correlating the recruit:adult ratio as a function of the adult density. 5. To model the effect of temperature on the probability of settlement (ε) we used a generalized linear mixed models (GLMM), with a Poisson error distribution and a logit link function, the independent variable was the number of zygotes, temperature was treated as a fixed variable and we used the ID of each quadrat of the Petri dishes as a random variable. 6. To model the effect of temperature and time (fixed factors) on germling survival (σs), we used a GLMM with a binomial error distribution and a logit link function, with the ID of each quadrat of each Petri dish as a random variable to deal with the lack of independence between observations repeated at different times and a binomial error distribution was assumed to deal with the binary response variable (survive vs. die). 7. The size distribution of recruits was estimated as a normal probability function. In addition, the function required to project the density-dependent and stochastic IPMs is provided.
modsum
Density-dependent function, relating the number of Cystoseira zosteroides recruits with the number of adults. It is a generalized linear model (GLM) with Poisson error distribution and a log-link function, correlating the recruit:adult ratio with the adult density. This file is needed to run the code CzIPM.R.
sett
Data on the impacts of temperature (16ºC, 20ºC and 24ºC) on the settlement of Cystoseira zosteroides early stages. This file is needed to perform the projections in CzIPM.R code.
survrec
Data on the impacts of the temperature treatments (16ºC, 20ºC and 24ºC) to early survival of Cystoseira zosteroides. This file is required to run the code CzIPM.R.
