The immediate effects of plant polyploidization are well characterized and it is generally accepted that these morphological, physiological, developmental, and phenological changes contribute to polyploid establishment. Studies on the environmental dependence of the immediate effects of whole-genome duplication (WGD) are, however, scarce but suggest that these immediate effects are altered by stressful conditions. As polyploid establishment seems to be associated with environmental disturbance, the relationship between ploidy-induced phenotypical changes and environmental conditions is highly relevant. Here, we use a common garden experiment on the greater duckweed Spirodela polyrhiza to test whether the immediate effects of WGD can facilitate the establishment of tetraploid duckweed along gradients of two environmental stressors. Because successful polyploid establishment often depends on recurrent polyploidization events, we include four genetically diverse strains and assess whether these immediate effects are strain-specific. We find evidence that WGD can indeed confer a fitness advantage under stressful conditions and that the environment affects ploidy-induced changes in fitness and trait reaction norms in a strain-specific way.

Aim Historical processes that shaped current diversity patterns of seaweeds remain poorly understood. Using Dictyotales, a globally distributed order of brown seaweeds as a model, we test if historical biogeographical and diversification patterns are comparable across clades. Dictyotales contain some 22 genera, three of which, Dictyota, Lobophora and Padina, are exceptionally diverse. Specifically, we test whether the evolutionary processes that shaped the latitudinal diversity patterns in these clades are in line with the tropical conservatism, out‐of‐the‐tropics or diversification rate hypotheses. Location Global coastal benthic marine environments. Taxon Dictyotales (Phaeophyceae). Methods Species diversity was inferred using DNA‐based species delineation, addressing cryptic diversity and circumventing taxonomic problems. A six‐gene time‐calibrated phylogeny, distribution data of 3,755 specimens and probabilistic modelling of geographical range evolution were used to infer historical biogeographical patterns. The phylogeny was tested against different trait‐dependent models to compare diversification rates for different geographical units as well as different thermal affinities. Results Our results indicate that Dictyotales originated in the Middle Jurassic and reach a current peak of species diversity in the Central Indo‐Pacific. Ancestral range estimation points to a southern hemisphere origin of Dictyotales corresponding to the tropical southern Tethys Sea. Our results demonstrate that diversification rates were generally higher in tropical regions, but increased diversification rates in different clades are driven by different processes. Our results suggest that three major clades underwent a major diversification burst in the early Cenozoic, with Dictyota and Padina expanding their distribution into temperate regions while Lobophora retained a predominantly tropical niche. Main conclusions Our results are consistent with both the tropical conservatism hypothesis, in which clades originate and remain in the tropics (Lobophora), and the out‐of‐the‐tropics scenario, where taxa originate and expand towards the temperate regions while preserving their presence in the tropics (Dictyota, Padina).

Abstract:The performance of populations is affected by environmental change and the resulting evolutionary dynamics. The spatial configuration and size of patches is known to directly influence metapopulation dynamics (spatial forcing). These metapopulation dynamics are also affecting and affected by life history evolution. Given the relevance of metapopulation persistence for biological conservation, and the potential rescuing role of evolution, a firm understanding of the relevance of these eco-evolutionary processes is essential.We here follow a system's modelling approach to disentangle the role of metapopulation structure relative to evolution for metapopulation performance. We developed an individual based systems model that is strongly based and parameterized by results from experimental metapopulations with spider mites. This model enables us to perform virtual translocation and invasion experiments that would have been impossible to conduct in our experimental systems.We show that (1) metapopulation demography is more affected by spatial forcing than by observed life history evolution, but that life history evolution contributes up to 20% of the variation in demographic measures related to spatiotemporal variance in population sizes, (2) metapopulation performance is not enhanced by evolution, and (3) evolution is optimising individual performance in metapopulations when considering the importance of so far overlooked stress resistance evolution.We thus provide evidence that metapopulation-level selection maximises individual performance and more importantly, that -at least in our system-evolutionary changes impact metapopulation dynamics, especially factors related to local and metapopulation sizes.

The spatial configuration and size of patches influence metapopulation dynamics by altering colonisation–extinction dynamics and local density dependency. This spatial forcing as determined by the metapopulation typology then imposes strong selection pressures on life‐history traits, which will in turn feed back on the ecological metapopulation dynamics. Given the relevance of metapopulation persistence for biological conservation, and the potential rescuing role of evolution, a firm understanding of the relevance of these eco‐evolutionary processes is essential. We here follow a systems’ modelling approach to quantify the importance of spatial forcing and experimentally observed life‐history evolution for metapopulation demography as quantified by (meta)population size and variability. We therefore developed an individual‐based model matching an earlier experimental evolution with spider mites to perform virtual translocation and invasion experiments that would have been otherwise impossible to conduct. We show that (a) metapopulation demography is more affected by spatial forcing than by life‐history evolution, but that life‐history evolution contributes substantially to changes in local‐ and especially metapopulation‐level population sizes, (b) extinction rates are minimised by evolution in classical metapopulations, and (c) evolution is optimising individual performance in metapopulations when considering the importance of more cryptic stress resistance evolution. Ecological systems’ modelling opens up a promising avenue to quantify the importance of eco‐evolutionary feedbacks in spatially structured populations. Metapopulation sizes are especially impacted by evolution, but its variability is mainly determined by the spatial forcing. Eco‐evolutionary dynamics can increase the persistence of classical metapopulations. Conservation of genetic variation and, hence, adaptive potential is thus not only essential in the face of environmental change; it also generates putative rescuing feedbacks that impact metapopulation persistence.

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