Vegetation change on mountaintops in northern Sweden: Stable vascular-plant but reordering of lichen and bryophyte communities

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The evolvability of animal-pollinated flowers: towards predicting adaptation to novel pollinator communities

In the event of a community turnover, population decline, or complete disappearance ofpollinators, animal-pollinated plants may respond by adapting to novel pollinators or bychanging their mating system. The ability of populations to adapt is determined by their abilityto respond to novel selection pressures, i.e. their evolvability. In the short term, evolvability isdetermined by standing genetic variation in the trait under selection. To evaluate the evolutionary potential of plant reproductive systems, I compiled genetic-variance estimates for a large selection of floral traits mediating shifts in pollination and mat-ing systems. Then, I computed evolvabilities and compared these among trait groups andagainst the evolvabilities of vegetative traits. Evolvabilities of most floral traits were substantial yet tended to be lower than the medianfor vegetative traits. Among floral traits, herkogamy (anther–stigma distance), floral-displaytraits and perhaps floral-volatile concentrations had greater-than-average evolvabilities, whilethe evolvabilities of pollinator-fit traits were below average. These results suggest that most floral traits have the potential to evolve rapidly in responseto novel selection pressures, providing resilience of plant reproductive systems in the event ofchanging pollinator communities

Topographic complexity and biotic resilience to climate change

Topographically complex alpine terrains create a mosaic of diverse microclimates over short distances. This study investigated the extent of small-scale variation in temperature and soil moisture using dense arrays of temperature loggers and moisture measurements, and how this microclimatic variation influenced vascular-plant species richness and intra-specific trait variation across five pairs of 40x40 m landscape plots of contrasting complexity in alpine tundra at Finse, Norway. Spatial variation in mean temperature within landscape plots was in the range of 2-4 °C, similar to what is expected across large altitudinal or latitudinal distances, suggesting an important ?buffering capacity? of such landscapes in the event of climate warming. Rough landscapes contained more species than flatter ones, while patterns of within-species phenotypic variation were less clear and differed between species. These results suggest that local reshuffling and short-distance migration will be important biotic responses to climate change in this system, with assumed associated changes in biotic interactions and ecosystem function. The study also highlights the importance of mountains as target areas for biodiversity conservation

Topographic complexity and biotic resilience to climate change

Topographically complex alpine terrains create a mosaic of diverse microclimates over short distances. This study investigated the extent of small-scale variation in temperature and soil moisture using dense arrays of temperature loggers and moisture measurements, and how this microclimatic variation influenced vascular-plant species richness and intra-specific trait variation across five pairs of 40x40 m landscape plots of contrasting complexity in alpine tundra at Finse, Norway. Spatial variation in mean temperature within landscape plots was in the range of 2-4 °C, similar to what is expected across large altitudinal or latitudinal distances, suggesting an important buffering capacity of such landscapes in the event of climate warming. Rough landscapes contained more species than flatter ones, while patterns of within-species phenotypic variation were less clear and differed between species. These results suggest that local reshuffling and short-distance migration will be important biotic responses to climate change in this system, with assumed associated changes in biotic interactions and ecosystem function. The study also highlights the importance of mountains as target areas for biodiversity conservation

Topographic complexity and biotic resilience to climate change

Topographically complex alpine terrains create a mosaic of diverse microclimates over short distances. This study investigated the extent of small-scale variation in temperature and soil moisture using dense arrays of temperature loggers and moisture measurements, and how this microclimatic variation influenced vascular-plant species richness and intra-specific trait variation across five pairs of 40x40 m landscape plots of contrasting complexity in alpine tundra at Finse, Norway. Spatial variation in mean temperature within landscape plots was in the range of 2-4 °C, similar to what is expected across large altitudinal or latitudinal distances, suggesting an important buffering capacity of such landscapes in the event of climate warming. Rough landscapes contained more species than flatter ones, while patterns of within-species phenotypic variation were less clear and differed between species. These results suggest that local reshuffling and short-distance migration will be important biotic responses to climate change in this system, with assumed associated changes in biotic interactions and ecosystem function. The study also highlights the importance of mountains as target areas for biodiversity conservation

Quantitative and qualitative consequences of reduced pollen loads in a mixed-mating plant

Greater pollination intensity can enhance maternal plant fitness by increasing seed set and seed quality as a result of more intense pollen competition or enhanced genetic sampling. We tested experimentally these effects by varying the pollen load from a single pollen donor on stigmas of female flowers of Dalechampia scandens (Euphorbiaceae) and measuring the effects on seed number and seed mass. Seed set increased rapidly with pollen number at low to moderate pollen loads, and a maximum set of three seeds occurred with a mean pollen load of 19 pollen grains. We did not detect a trade‐off between the number of seeds and seed mass within a fruit. Seed mass increased with increasing pollen load, supporting the hypothesis of enhanced seed quality via increased pollen‐competition intensity or genetic sampling. These results suggest that maternal fitness increases with larger pollen loads, even when the fertilization success is already high. Our results further highlight the importance of high rates of pollen arrival onto stigmas, as mediated by reliable pollinators. Comparing the pollen‐to‐seed response curve obtained in this experiment with those observed in natural populations suggests that pollen limitation may be more severe in natural populations than predicted from greenhouse studies. These results also indicate that declines in pollinator abundance may decrease plant fitness through lowered seed quality before an effect on seed set is detected

Quantitative and qualitative consequences of reduced pollen loads in a mixed-mating plant

Greater pollination intensity can enhance maternal plant fitness by increasing seed set and seed quality as a result of more intense pollen competition or enhanced genetic sampling. We tested experimentally these effects by varying the pollen load from a single pollen donor on stigmas of female flowers of Dalechampia scandens (Euphorbiaceae) and measuring the effects on seed number and seed mass. Seed set increased rapidly with pollen number at low to moderate pollen loads, and a maximum set of three seeds occurred with a mean pollen load of 19 pollen grains. We did not detect a trade‐off between the number of seeds and seed mass within a fruit. Seed mass increased with increasing pollen load, supporting the hypothesis of enhanced seed quality via increased pollen‐competition intensity or genetic sampling. These results suggest that maternal fitness increases with larger pollen loads, even when the fertilization success is already high. Our results further highlight the importance of high rates of pollen arrival onto stigmas, as mediated by reliable pollinators. Comparing the pollen‐to‐seed response curve obtained in this experiment with those observed in natural populations suggests that pollen limitation may be more severe in natural populations than predicted from greenhouse studies. These results also indicate that declines in pollinator abundance may decrease plant fitness through lowered seed quality before an effect on seed set is detected

Fitness costs of delayed pollination in a mixed-mating plant

Background and Aims To predict the evolutionary consequences of pollinator declines, we need to understand the evolution of delayed autonomous self-pollination, which is expected to evolve as a mechanism of reproductive assurance when cross-pollination becomes unreliable. This involves estimating the costs of increased levels of selfing as well as those associated with floral senescence. Methods We studied the mechanisms and costs of delayed self-pollination in the mixed-mating vine Dalechampia scandens (Euphorbiaceae) by first assessing among-population variation in herkogamy and dichogamy, which together determine the rate and timing of autonomous self-pollination. We then tested whether floral longevity responds plastically to delayed pollination. Finally, we assessed the costs of delayed self-pollination in terms of seed number and size, explicitly separating inbreeding depression from effects of floral senescence. Key Results Herkogamy varied extensively, while variation in dichogamy was more limited. Unpollinated blossoms increased their longevity, but seed quantity and quality decreased with increasing delays in pollination, independently of inbreeding depression. Conclusions In D. scandens, earlier autonomous selfing is facilitated by reduced herkogamy rather than reduced protogyny, providing reproductive assurance while maintaining the possibility for outcrossing events. Effective early autonomous self-pollination may evolve under reduced cross-pollination reliability in response to costs associated with floral senescence

Quantitative and qualitative consequences of reduced pollen loads in a mixed-mating plant

Greater pollination intensity can enhance maternal plant fitness by increasing seed set and seed quality as a result of more intense pollen competition or enhanced genetic sampling. We tested experimentally these effects by varying the pollen load from a single pollen donor on stigmas of female flowers of Dalechampia scandens (Euphorbiaceae) and measuring the effects on seed number and seed mass. Seed set increased rapidly with pollen number at low to moderate pollen loads, and a maximum set of three seeds occurred with a mean pollen load of 19 pollen grains. We did not detect a trade‐off between the number of seeds and seed mass within a fruit. Seed mass increased with increasing pollen load, supporting the hypothesis of enhanced seed quality via increased pollen‐competition intensity or genetic sampling. These results suggest that maternal fitness increases with larger pollen loads, even when the fertilization success is already high. Our results further highlight the importance of high rates of pollen arrival onto stigmas, as mediated by reliable pollinators. Comparing the pollen‐to‐seed response curve obtained in this experiment with those observed in natural populations suggests that pollen limitation may be more severe in natural populations than predicted from greenhouse studies. These results also indicate that declines in pollinator abundance may decrease plant fitness through lowered seed quality before an effect on seed set is detected

Rainfall seasonality predicts the germination behaviour of a tropical dry-forest vine

Seed dormancy is considered to be an adaptive strategy in seasonal and/or unpredictable environments because it prevents germination during climatically favorable periods that are too short for seedling establishment. Tropical dry forests are seasonal environments where seed dormancy may play an important role in plant resilience and resistance to changing precipitation patterns. We studied the germination behavior of seeds from six populations of the Neotropical vine Dalechampia scandens (Euphorbiaceae) originating from environments of contrasting rainfall seasonality. Seeds produced by second greenhouse‐generation plants were measured and exposed to a favorable wet environment at different time intervals after capsule dehiscence and seed dispersal. We recorded the success and the timing of germination. All populations produced at least some dormant seeds, but seeds of populations originating from more seasonal environments required longer periods of after‐ripening before germinating. Within populations, larger seeds tended to require longer after‐ripening periods than did smaller seeds. These results indicate among‐population genetic differences in germination behavior and suggest that these populations are adapted to local environmental conditions. They also suggest that seed size may influence germination timing within populations. Ongoing changes in seasonality patterns in tropical dry forests may impose strong selection on these traits