Hierarchical trade-off model for eusocial species.

<p>Simplified hierarchical trade-off with a focus on workers for eusocial species, including two trade-offs at the colony and the individual levels. Arrows indicate resource flows. Resources are obtained by workers that do not reproduce and are allocated toward worker maintenance () and/or the colony (1−). At the colony level, resources that are not consumed by workers can be allocated to sexual reproduction () and/or maintenance (1−), such as the production of new workers or different levels of worker quality.</p

Model results under different levels of extrinsic mortality.

<p>The horizontal axis represents the values of extrinsic mortality used to run the model(;). A) and B) show the optimized parameters (, ,) from our model. In C)–F) the solid lines indicate the results when the optimal values of and , The dashed lines indicate results if the colony did not change the maintenance investments () or the switching time () with increasing extrinsic mortality ( = 0.38  = 84). A) Optimal investment into workers () decreases with increasing extrinsic risk. B) Denotes the switching time (), where the colony switches to the production of sexuals. C) The number of sexuals alive at the end of the season (maximized by finding optimal values for switching time () and maintenance investments into workers ()) decreases with increasing extrinsic mortality. D) Worker mortality combines intrinsic and extrinsic mortality (). The dashed line denotes the increase of extrinsic mortality. The difference between the dashed and solid lines shows the effect of the changing investment in worker maintenance. E) Worker life expectancy at the beginning of the season with different levels of extrinsic mortality. F) Worker life expectancy at switching time. At switching time, the worker population reaches its maximum. The difference in worker life span between e) and f) is due to the reduction of foraged resources caused by density dependency. Used parameters:  = 0.15,  = 0.005,  = 0.0024,  =  = 0–0.06.</p

Morphological adaptations of <i>Chara baltica</i> and <i>Chara liljebladii</i> (Characeae) under different light conditions

<p>Individuals within wild populations differ substantially in their fitness as a result of either genetic differences or acclimation. Within the Charophyte algae, the two taxa <i>Chara baltica</i> and <i>C</i>. <i>liljebladii</i> predominate at different water depths of the same habitat. The two taxa are mainly distinguished by quantitative characteristics, pointing to light acclimation. In particular, they differ by a length of the internode and the bract cells, as well as the cortication type. Genetic analyses revealed that individuals of both morphotypes are genetically identical, and hence may belong to the same species. In the present paper, we tested a hypothesis that <i>C</i>. <i>liljebladii</i> is a low-light phenotype of <i>C</i>. <i>baltica</i>. Can a <i>C</i>. <i>baltica</i> phenotype be transferred into a <i>C</i>. <i>liljebladii</i> (and vice versa) by manipulation of the environmental conditions such as irradiance? We observed significant changes in the morphology of <i>C</i>. <i>baltica</i>: decreasing the irradiance significantly increased the growth of the branchlets and internodal cells. Consequently, the plants grew larger, changing their morphology in the direction of the <i>C</i>. <i>liljebladii</i> morphotype. In the reverse experiment, subjecting <i>C</i>. <i>liljebladii</i> to increasing irradiances, the individuals had slightly better growth, but none of the analysed morphological characteristics changed significantly. Both taxa have thus shown different adaptations to light limitation. Their morphologies cannot be transferred into each other by environmental factors. Thus, the presence of the different morphologies reflects the ecological characteristics of their habitats, such as light availability or turbidity.</p

Diaspore bank analysis of Baltic coastal waters

<p>The coastal waters are important transition zones for terrestrial nutrient and pollutant runoff and the open Sea. During the last decades, eutrophication has negatively influenced macrophyte communities of the coastal ecosystems, making restoration activities inevitable. This study analysed recent macrophyte vegetation and the reproductive potential through the sediment diaspore reservoir along the German Baltic Sea coastline. Salinity was identified to be the responsible factor for shifts in the macrophyte community with most commonly found species like <i>Stuckenia pectinata</i> or <i>Myriophyllum spicatum</i>. In contrast, the oospores of small charophytes (e.g. <i>Tolypella nidifica</i>) clearly dominated the sediment diaspore bank. The germination rates differed in the recent vegetation composition and the diaspore bank composition with <i>Zannichellia palustris</i> as the dominant species. However, several species not visually detected at the respective sites were represented in the diaspore bank and germinated at a low rate (e.g. <i>Chara contraria</i> and <i>Lamprothamnium papulosum</i>). The maximal germination frequency corresponded to the sediment layer in which diaspore density was the highest (5–15 cm). In conclusion, the germinable diaspores were observed at all sites. Considering the differences between the diaspore composition, recent vegetation and germination success, we have illustrated the potential of the diaspore banks for the restoration of the macrophyte communities after at least mid-term periods of disturbance.</p