Anu Valtonen

Flowering and seed production success along roads with different mowing regimes

ABSTRACT Question: Which one of the two mainly used mowing regimes along road verges, mowing once or twice a year is a better option regarding flowering and seed-producing success of grassland species and plant species in general? Location: Southeast Finland. Methods: Plant species composition, flowering and seed production success were studied in road verges (1) mown once in August and (2) mown at the end of June and August. Flowering shoots were counted and phenological phases were estimated four times during a growing season. Results: The numbers of flowering or seed-producing species and shoots indicated that mowing once a year corresponding to the timing of traditional management was markedly better than mowing twice a year. The difference between the management groups was greatest at the end of July when the number of flowering species was 43% and the number of flowering and seed-producing shoots 76% less after the first mowing than in the still unmown sites. The species avoided early cutting either through the timing of flowering or due to their growth form. Early season mowing had no effect on the occurrence and seed-producing success of grassland species and the first flowering species. Seed production of grasses succeeded poorly in the verges mown twice. Conclusion: Mowing once in August resulted in higher seed production in general, but mowing twice a season might be a better way to manage young verges on nutrient-rich soils. The useful qualities of the management options should be considered locally when planning road verge management. Nomenclature: Hämet-Ahti et al. (1998).

Environmental controls on the phenology of moths: predicting plasticity and constraint under climate change

Ecological systems have naturally high interannual variance in phenology. Component species have presumably evolved to maintain appropriate phenologies under historical climates, but cases of inappropriate phenology can be expected with climate change. Understanding controls on phenology permits predictions of ecological responses to climate change. We studied phenological control systems in Lepidoptera by analyzing flight times recorded at a network of sites in Finland. We evaluated the strength and form of controls from temperature and photoperiod, and tested for geographic variation within species. Temperature controls on phenology were evident in 51% of 112 study species and for a third of those thermal controls appear to be modified by photoperiodic cues. For 24% of the total, photoperiod by itself emerged as the most likely control system. Species with thermal control alone should be most immediately responsive in phenology to climate warming, but variably so depending upon the minimum temperature at which appreciable development occurs and the thermal responsiveness of development rate. Photoperiodic modification of thermal controls constrains phenotypic responses in phenologies to climate change, but can evolve to permit local adaptation. Our results suggest that climate change will alter the phenological structure of the Finnish Lepidoptera community in ways that are predictable with knowledge of the proximate physiological controls. Understanding how phenological controls in Lepidoptera compare to that of their host plants and enemies could permit general inferences regarding climatic effects on mid- to high-latitude ecosystems.

Tropical phenology: bi‐annual rhythms and interannual variation in an Afrotropical butterfly assemblage

Temporal variation and phenology of tropical insect communities and the role of environmental factors controlling this variation is poorly understood. A better understanding is needed, for example, to predict the effects of climate change on tropical insect communities and to assess the long-term persistence of tropical communities. We studied seasonal and inter-annual variation in tropical fruit-feeding butterflies by exploiting a unique 137-month abundance time series of >100 species, sampled at 22 locations in the medium altitude montane rain forest of Kibale National Park, western Uganda. Precipitation peaked twice per year, about 20 d after each equinox. Vegetation greenness peaked approximately 33 d later. Species richness and abundance of butterflies peaked about 2 and 3 months, respectively, after the greenness peak. Furthermore, temporal shifts in peaks of butterfly abundances of each 6-month cycle positively correlated with temporal shifts in peaks of vegetation greenness approximately three months before. The butterfly assemblages of ENSO warm phase years differed significantly from assemblages of the other years. To our knowledge this is the first elucidation of bi-annual rhythms in butterfly assemblages. Host plant availability could explain the seasonal cycles in butterfly abundance and species richness, because the 3-month lag observed matches with the egg-to-adult development time in the studied species.

The Effects of Sex and Season on Home Range in European Hedgehogs at the Northern Edge of the Species Range

Limited data exist on ecology of European hedgehog (Erinaceus europaeus) at the northern edge of the species’ range. In our study, spatial analysis using radio-tracking data from Finland showed that sex and season had significant effects on the homerange size of hedgehogs. Although males were heavier than females, body weight had no effect on home-range size. Total home ranges (male 98, female 55 ha) were larger than those in southern areas. Thus, male home ranges were larger than those of females during the mating (male 72, female 21 ha) and post-mating seasons (male 48, female 20 ha), but the differences were small and reversed before hibernation (male 17, female 29 ha). Home ranges of individuals of both sexes overlapped, but females shared core areas with other females only during the mating season. Our results imply possible differences in hedgehog ecology probably due to a less productive and harsh northern habitat.

Insect herbivore damage on latitudinally translocated silver birch (Betula pendula) – predicting the effects of climate change

Boreal forests might be challenged by increased herbivory pressure in the future due to global warming, since warming is predicted to increase the abundance of herbivorous insects and to lead to shifts in their distribution towards higher latitudes where they might face more palatable food sources. We studied the effect of the latitudinal translocation of silver birch (Betula pendula Roth) on herbivore damage to 26 micropropagated genotypes originating from six populations ranging from 60 to 67°N in Finland in two growing seasons, 2011 and 2012. The genotypes were planted at three sites located in southern (60°N), central (62°N) and northern (67°N) Finland. The genotypes translocated to lower latitudes from their latitudes of origin were experiencing higher intensity of herbivore damage compared to the genotypes translocated to higher latitudes in 2011, but not in 2012. All genotypes were experiencing herbivore damage by local herbivores of each study site. These results suggest that, as many herbivore species are predicted to shift their ranges towards higher latitudes, they can feed on novel host plant genotypes and may face more palatable food sources than at their present range. This suggests that future climate change will increase herbivore damage to young silver birch. Increased herbivory, in turn, might affect the growth of birch and therefore should be considered when making predictions about the boreal forest composition in the future.

Mixed artificial diets enhance the developmental and reproductive performance of the edible grasshopper, Ruspolia differens (Orthoptera: Tettigoniidae)

Diet mixing is a common feeding habit among polyphagous insect herbivores and is believed to be advantageous for performance-related factors like growth, survival and oviposition. However, relatively little is known about the influence of artificial diet or their mixtures on the performance of edible insects. We examined the effects of artificial diet mixtures on the developmental and reproductive performance (survival, developmental time, fresh adult weight and female fecundity) of an edible grasshopper, Ruspolia differens (Orthoptera: Tettigoniidae). We raised individuals from eggs and reared newly hatched nymphs to adult stage on six different dietary treatments consisting of a single diet, and mixtures of two, three, five, six and eight artificial diets. More diversified diets resulted in shorter development time and greater adult fresh weight and female fecundity compared to the single diet or less diversified diets. Even with slight diet diversification, survival to adult stage was greatly improved. Overall, these results highlight the potential of diet mixtures in achieving maximum adult weights and female fecundity and shortening development time, information which could be used when designing mass-rearing programs for this edible grasshopper.

The fatty acid contents of the edible grasshopper Ruspolia differens can be manipulated using artificial diets

Edible insects have been suggested as an alternative and sustainable source of fats, proteins and vitamins for humans. However, their nutritional content may largely depend on the diets offered for insects. Diet-based manipulation of fatty acids in edible insects shows promise to possibly increase their essential and long-chained polyunsaturated fatty acid content and thus further enhance human diets. We reared the edible grasshopper, Ruspolia differens, under various diets with manipulated content of fatty acids, proteins and carbohydrates. The manipulated diets dramatically altered the insects’ content and composition of fatty acids, especially the content of polyunsaturated fatty acids. Dietary fatty acids were stored largely unaltered in insects. Artificial diets with high content of linoleic, α-linolenic, eicosapentaenoic or docosahexaenoic acids, increased the content of these fatty acids in the insect tenfold. The manipulated diets also affected the omega-6/omega-3 (n-6/n-3) fatty acid ratio and de...

Tree community composition and vegetation structure predict butterfly community recovery in a restored Afrotropical rain forest

Abstract Anthropogenic disturbances have led to a dramatic loss of biodiversity in the tropics. Habitat restoration can mitigate biodiversity loss but studies describing insect community recovery during tropical forest restoration are limited in Africa. Our aim was to compare the predictive power of tree community composition versus vegetation structure for butterfly community composition during tropical rain forest restoration. A fruit-feeding butterfly dataset from two primary and six restored forest areas of Kibale National Park (Uganda) was used. At the same sites, the tree community composition and six variables describing the vegetation structure, namely; (1) total stem density per hectare; (2) tree canopy cover; (3) elephant grass cover; (4) “other grass” cover; (5) shrub cover; and (6) herb cover, were sampled. Co-correspondence analysis and canonical correspondence analysis were used to predict butterfly community composition from tree community composition or vegetation structure, respectively. Both tree community composition and vegetation structure predicted butterfly community equally well. We also found a corresponding successional gradient of butterfly and tree communities, associated with the age of the forest since restoration started. Most butterfly species had their peak abundance (optima) in the late successional or primary forests, while most tree species had their optima in primary forests. Elephant grass cover and tree canopy cover were the most important predictors of the butterfly community composition. Our results demonstrate how tropical forest restoration can ignite successional changes in tree communities and vegetation structure, which in turn restructure the animal communities, according to resource availability and species-specific habitat requirements.

Bottom‐up manipulations alter the community structures of galling insects and gall morphs on Neoboutonia macrocalyx trees in a moist tropical rainforest

The effects of bottom‐up forces on the community structure of tropical insect gallers and within species variation in gall morphotype assemblages are not well understood. We tested the roles of increased nutritional quality and density of host plants with respect to structuring the galling insect communities and gall morphotype assemblages on Neoboutonia macrocalyx trees in Uganda. Plant nutritional quality and resource concentration were manipulated with four levels of fertilization and the group size of trees, respectively. After applying these treatments in May 2011, gallers established naturally on experimental replicates. Five months later, we sampled gallers and recorded their numbers and the different morphotypes. We analyzed the effects of treatments on the structures of galler communities and gall morphotype assemblages. We recorded 5237 individuals, representing four galler species. One species, Cecidomyiid leaf galler, was represented by three morphologically distinct galls. Fertilization, host tree density and their interactions significantly changed the structures of galler species communities and gall morphotype assemblages. The results of the present study demonstrate the important role of bottom‐up factors in structuring galler communities and the gall morphotype assemblages. These changes are likely caused by differential responses of different galler species and gall morphs to plant quality or quantity changes.

Susceptibility of silver birch (Betula pendula) to herbivorous insects is associated with the size and phenology of birch – implications for climate warming

ABSTRACT Susceptibility of trees to herbivorous insects is often associated with the tree growth and phenology, both of which are sensitive to a warming climate. Therefore, changes in these traits may affect the intensity of herbivory on trees in the future. We grew silver birch (Betula pendula) populations differing in their growth and phenology in a common garden experiment, and studied the effect of these plant traits on the leaf herbivory, insect herbivore density and community composition of herbivores in two consecutive years, 2011 and 2012. Differences in size and the timing of growth cessation among the birch genotypes were related to differences in herbivore community compositions and herbivory. In 2011, the most intensive herbivore damage was observed on birch genotypes of small size, late bud burst and early growth cessation, and these genotypes originated from high-latitude populations. The differences among birch genotypes in their susceptibility to herbivore damage may lead to differences in their competitive abilities. While climate warming will affect phenology and growth of plants, our study shows, that it may indirectly affect herbivory and herbivore communities as well.