Darwin and the plants of the Galapagos-Islands

During his five year sea voyage with the “Beagle”, Darwin, at the suggestion of the botanist J.S. Henslow, collected more than 1400 vascular plants, and more than 200 of them alone during his short stay on the Galápagos Islands. The unique collection of plants from the Galápagos archipelago was examined in 1845 by J.D. Hooker. Unlike the birds, Darwin had collected the plants separately for each island. Hooker described 78 of them as new species and analyzed the close biogeographical relations of the Galápagos flora with the South-American continent. The finding that more than 50% of the species are not found anywhere else on the globe – are hence endemics, many of them restricted to individual islands – was a sensation for Hooker and Darwin. Hooker correctly characterized the Asteraceae as the most remarkable family of the Galápagos Islands, due to the great number of their endemic genera and species. He also discussed the adaptations which might have allowed the plants of the different families to reach the isolated islands. Hooker’s results played an important role for Darwin in his developing the theory of evolution, and – besides the examples of birds, tortoises, and lizards – provided him with weighty arguments to defend it. There are seven endemic plant genera on the Galápagos Islands, and 19 genera that are adaptively diversified. With 19 endemic taxa, the genus Scalesia (Asteraceae) is the most spectacular example of an adaptive radiation, followed by the prickly pear cactuses (Opuntia) with 14 endemic taxa. While Darwin’s finches meanwhile represent one of the best-studied examples of evolution and adaptive radiation, only little research has been done so far into evolutionary processes in plants of the Galápagos archipelago. The prominent role that Darwin’s plants played for his scientific insights is even less known

Evolution der Gattung Echium auf den Kanarischen Inseln: vom Kraut zum Strauch zum Rosettenbaum

The genus Echium is represented on the seven volcanic Canary islands by 24 closely related endemic species. As in other genera on the archipelago, the diversityin Echium is a result of rapid adaptive radiation during the last few million years. Withmolecular markers, the evolution of Echium on the Canary Islands can be traced backto a single colonisation event. In contrast to Echium species on the continent, most ofthe insular endemics are woody perennials. Some of the more spectacular species aregiant rosette trees that flower only once and then die. The evolutionary diversificationin Echium results from the drastic climatic changes in the past, from the climatic andedaphic diversity of habitats, and from genetic bottleneckevents during the colonisationof newly formed volcanic islands. Today, the predominance of woodiness inendemic island species is explained by selection for longevity due to the scarcity ofpollinators. The red-flowered E. wildpretii occurring in the volcanic Caldera of the highestmountain on Tenerife, Pico el Teide, is the most spectacular giant rosette tree ofthe archipelago and is pollinated by an endemic bird. From molecular studies the phylogeneticrelationship among Echium species are well known. Their ecology, however,needs to be better explored in order to protect them from harmful consequences ofhabitat destruction and climatic change

Differences in life history traits of related Epilobium species: Clonality, seed size and seed number

Small changes in morphology can affect the performance and functions of organisms and hence their ecological success. In modular constructed plants, contrasting growth strategies may be realized by differences in the spatial arrangement and size of shoots. Such differences change the way in which meristems and resources are assigned to various functions during the lifespan of a plant. If such changes include the capacity to spread clonally, sexual reproduction may also be affected. I compare patterns in vegetative growth and sexual reproductive traits in four allopatric species ofEpilobium which are sometimes considered as subspecies of a single polymorphic taxon. The four species differ in the location of the buds which annually renew the aerial shoot system.E. dodonaei andE. steveni do not spread clonally and are characterized by a shrub-like habit.E. fleischeri, a species occurring only in the Alps, andE. colchicum, which occurs in the upper region of the Caucasus mountains, both produce buds on horizontal roots or plagiotropic shoots. Both alpine species exhibiting clonal growth have smaller shoots, fewer fruits and smaller seeds than the lowland species. An intraspecific trade-off between seed number per fruit and seed mass is realized. Both alpine species produce more seeds per fruit at the expense of seed mass. The morphological relationship between the four species and their geographical distribution suggest that clonal growth inE. fleischeri (restricted to the Alps) andE. colchicum (restricted to the Caucasus) is adaptively associated with the stressful conditions of alpine habitats. Our results suggest that clonal growth is not necessarily correlated with reduced reproduction by seeds. The success of plants which are already established may largely depend on clonal spread, but the colonization of new habitats depends on the production of a large number of small seeds with high dispersabilit

Flora der Furka

The Furka is an Alpine pass at 2431 m a.s.l. connecting the Urseren Valley and the Rhone Valley in the central Swiss Alps. Furthermore, the Furka is the watershed between the Mediterranean and the North Sea. The region is mostly characterized by siliceous rocks and acid soils, but calcareous sediments are also present. Here, the floristic composition and the plant communities of the Furka Region are described from a survey of 181 vegetation records covering all types of habitats, bedrocks, soils, slopes and expositions. In total 295 species, 153 genera and 49 plant families are represented in the Furka flora. The vegetation is composed of a diversity of mostly non-woody plant communities. Natural grasslands with Carex curvula and Nardus stricta on acid soils and with Festuca violacea on calcareous bedrock are most abundant. Grassland together with fens, dwarf shrubs, and plant communities from rock debris, screes, and glacier foreland create a diverse mosaic of alpine vegetation above timberline

Does pre-dispersal seed predation limit reproduction and population growth in the alpine clonal plant Geum reptans ?

We studied the impact of the seed damaging gall midge larva Geomyia alpina on its perennial alpine host plant Geum reptans. We analysed the effect of seed predation on reproduction by seeds, i.e. seed number, seed mass, and seed viability and on growth and clonal propagation of non-protected plants in comparison to plants protected from predation by an insecticide. Additionally, we assessed the consequences of seed predation for population growth using matrix projection modelling. Seed predation resulted in a decrease in total seed mass per flower head by 23.8% in non-protected plants (P<0.05). Individual seed mass decreased with increasing infestation intensity (P<0.05). Seed number remained unaffected because the sucking feeding behaviour by gall midge larvae does not evoke seed abortion. Percent germination of seeds from non-protected plants was reduced by 97.9% compared to seeds from protected plants. According to reduced seed viability, modelling revealed a decrease in population growth rate from λ=1.055 to λ=1.041. Predation did neither influence total plant biomass nor biomass fractions. But stolon dry-weight of non-protected plants increased by 24.1% (P<0.05), which may indicate a trade-off between sexual reproduction and clonal propagation. Our results demonstrate that despite substantial reduction of viable seeds, predation by gall midge larvae only slightly affected population growth of G. reptans suggesting that in this alpine species, persistence by longevity and clonal propagation can balance potential seed losses by predation, at least for local population growt

Genetic diversity, phenotypic variation and local adaptation in the alpine landscape: case studies with alpine plant species

Plant survival in alpine landscapes is constantly challenged by the harsh and often unpredictable environmental conditions. Steep environmental gradients and patchy distribution of habitats lead to small size and spatial isolation of populations and restrict gene flow. Agricultural land use has further increased the diversity of habitats below and above the treeline. We studied the consequences of the highly structured alpine landscape for evolutionary processes in four study plants: Epilobium fleischeri, Geum reptans, Campanula thyrsoides and Poa alpina. The main questions were: (1) How is genetic diversity distributed within and among populations and is it affected by altitude, population size or land use? (2) Do reproductive traits such as allocation to sexual or vegetative reproduction vary with altitude or land use? Furthermore, we studied if seed weight increases with altitude. Within-population genetic diversity of the four species was high and mostly not related to altitude and population size. Nevertheless, genetic differentiation among populations was pronounced and strongly increasing with distance. In Poa alpina genetic diversity was affected by land use. Results suggest considerable genetic drift among populations of alpine plants. Reproductive allocation was affected by altitude and land use in Poa alpina and by succession in Geum reptans. Seed weight was usually higher in alpine species than in related lowland species. We conclude that the evolutionary potential to respond to global change is mostly intact in alpine plants, even at high altitude. Phenotypic variability is shaped by adaptive as well as by random evolutionary processes; moreover plastic responses to growth conditions seem to be crucial for survival of plants in the alpine landscap

Differentiation in morphology and flowering phenology between two Campanula thyrsoides L. subspecies

Subspecies are usually characterised by sets of morphological discontinuities. By means of common garden experiments, we investigated genetic differentiation in morphological and phenological traits in two geographically disjunct subspecies of Campanula thyrsoides L., i.e. subsp. thyrsoides (=C.* thyrsoides) occurring in the European Alps and Jura Mountains, and subsp. carniolica (=C.* carniolica) occurring in the Southeastern Alps and the Dinaric Arc. Nine out of 16 investigated traits were significantly different between C.* thyrsoides and C.* carniolica. For C.* carniolica inflorescence length was 1.4×, and above-ground biomass 2.7× higher, while flower density was significantly lower. Campanula* carniolica also showed delayed flowering and flower development from bottom to top as compared to C.* thyrsoides which flowered from top to bottom. The inflorescence growth was indeterminate and flowering took several weeks in C.* carniolica, whereas C.* thyrsoides showed determinate flowering, rapidly opening all flowers within a few days. This differentiation in flowering phenology is likely to be adaptive. The submediterranean climate favours indeterminate flowering in C.* carniolica, allowing ongoing growth of the inflorescence throughout the long summer until environmental conditions worsen, whereas determinate and early flowering in C.* thyrsoides is favourable in the short growing season in the high Alps where seed production must be secured before temperature drops. Glacial survival in refugia with different climates (alpine vs. submediterranean) may have caused this regional differentiatio

High genetic differentiation in populations of the rare alpine plant species Campanula thyrsoides on a small mountain

Changes in climate and traditional land use have contributed to a loss and fragmentation of suitable habitats for many alpine plant species. Despite the importance of these changes, our knowledge of the consequences for gene flow and genetic diversity is still poor, especially in rare taxa and at fine spatial scales. Here, we investigated the genetic diversity in a rare alpine plant on a small and highly structured mountain in the Swiss Alps. Using microsatellite markers and Bayesian cluster analyses, we investigated genetic diversity within and among 24 populations of Campanula thyrsoides L. We also tested whether landscape structure has affected genetic structure by correlating genetic diversity with landscape and population features, which were assessed in a four-year monitoring period. The recorded genetic diversity (H e=0.714) and genetic differentiation ( $$G^{\prime}_{\rm ST}$$ =0.32) at distances of 1-10km were remarkably high. Clustering analyses revealed a split of populations into two genetically different spatial groups, but between-population genetic distances were neither correlated to geographic distance, elevation nor slope. The high differentiation and genetic bottlenecks may indicate strong founder effects, although the number of alleles was not decreased in bottlenecked populations. We conclude that stochastic colonisation by seeds is most important for shaping the genetic structure of C. thyrsoides on this small mountain. The high genetic diversity even in small populations may indicate that occasional gene flow is strong enough to overcome negative effects of bottlenecks. Nevertheless, further fragmentation and isolation of habitats may threaten this rare plant in the futur

Seed weight increases with altitude in the Swiss Alps between related species but not among populations of individual species

Seed weight is a crucial plant life history trait, determining establishment success and dispersal ability. Especially in stressful environments, larger seeds may be selected at the expense of seed number, because larger seeds have a better chance of giving rise to an established offspring. We tested the hypotheses that between related species-pairs and among populations of single species a similar trend for increasing seed weight with increasing altitude should be present. Firstly, we measured seed weights from 29 species-pairs, with one species occurring in lowland areas and a congeneric species from high altitudes. Seeds of the alpine species were 28±8% larger than seeds from lowland species (P<0.01). Compared to the related lowland species, 55% of the alpine species had heavier seeds, 3% (one species) had lighter, and 41% had seeds of approximately equal weight. Secondly, we compared seed weights among populations of four species from different habitats and with different life histories. Seeds from between 11 and 34 populations per species were sampled along altitudinal gradients of 800-1,500m (ca. 800m in Scabiosa lucida, ca. 1,000m in Saxifraga oppositifolia, ca. 1,000m in Epilobium fleischeri, and ca. 1,500m in Carex flacca). In all the four species, we found no indication for heavier seeds at higher altitudes. Our results indicate a selection pressure for species with heavier seeds at higher altitude, but the trend does not seem to operate across all cases. Phylogenetic constraints may limit the correlation among altitude and seed weight, operating particularly against selection for larger seed size, the closer populations and species are related to each othe