• Energy Research

AbstractChanging climates can influence species range shifts and biological invasions, but the mechanisms are not fully known. Using the model speciesPhragmites australis(Cav.) Trin. ex Steud. (Poaceae), we conducted a global analysis of climate and plant native and introduced cytotypes to determine whether this relationship influences population distributions, hypothesizing that smaller genomes are more common in regions of greater environmental stress. First, we identified 598Phragmites australisfield-collected native and introduced genome size variants using flow cytometry. We then evaluated whether temperature and precipitation were associated withP. australismonoploid genome size (Cx-value) distributions using Cx-value and Worldclim data. After accounting for potential spatial autocorrelation among source populations, we found climate significantly influenced Cx-value prevalence on continents. The relationships of Cx-value to temperature and precipitation varied according to whether plants were native or introduced in North America and Europe, and Cx-values were strongly influenced by precipitation during the dry season. Smaller plant monoploid genome size was associated with more stressful abiotic conditions; under extreme high temperatures and under drought, plants had smaller Cx-values. This may influence genome dominance, biological invasions, and range expansions and contractions as climate change selects for genome sizes that maximize fitness.

AbstractPlant genome size influences the functional relationships between cellular and whole‐plant physiology, but we know little about its importance to plant tolerance of environmental stressors and how it contributes to range limits and invasion success. We used native and invasive lineages of a wetland plant to provide the first experimental test of the Large Genome Constraint Hypothesis (LGCH)—that plants with large genomes are less tolerant of environmental stress and less plastic under stress gradients than plants with small genomes. We predicted that populations with larger genomes would have a lower tolerance and less plasticity to a stress gradient than populations with smaller genomes. In replicated experiments in northern and southern climates in the United States, we subjected plants from 35 populations varying in genome size and lineage to two salinity treatments. We measured traits associated with growth, physiology, nutrition, defense, and plasticity. Using AICc model selection, we found all plant traits, except stomatal conductance, were influenced by environmental stressors and genome size. Increasing salinity was stressful to plants and affected most plant traits. Notably, biomass in the high‐salinity treatment was 3.0 and 4.9 times lower for the invasive and native lineages, respectively. Plants in the warmer southern greenhouse had higher biomass, stomate density, stomatal conductance, leaf toughness, and lower aboveground percentage of N and total phenolics than in the northern greenhouse. Moreover, responses to the salinity gradient were generally much stronger in the southern than northern greenhouse. Aboveground biomass increased significantly with genome size for the invasive lineage (43% across genome sizes) but not for the native. For 8 of 20 lineage trait comparisons, greenhouse location × genome size interaction was also significant. Interestingly, the slope of the relationship between genome size and trait means was in the opposite direction for some traits between the gardens providing mixed support for LGCH. Finally, for 30% of the comparisons, plasticity was significantly related to genome size—for some plant traits, the relationship was positive, and in others, it was negative. Overall, we found mixed support for LGCH and for the first time found that genome size is associated with plasticity, a trait widely regarded as important to invasion success.