0000000000177409
AUTHOR
Jukka Suhonen
SELECTING HERB-RICH FOREST NETWORKS TO PROTECT DIFFERENT MEASURES OF BIODIVERSITY
Data on vascular plants of herb-rich forests in Finland were used to compare the efficiency of reserve selection methods in representing three measures of biodiversity: species richness, phylogenetic diversity, and restricted-range diversity. Comparisons of reserve selection methods were carried out both with and without consideration of the existing reserve system. Our results showed that the success of a reserve network of forests in representing different measures of biodiversity depends on the selection procedure, selection criteria, and data set used. Ad hoc selection was the worst option. A scoring procedure was generally more efficient than maximum random selection. Heuristic methods…
Regional variations in occupancy frequency distributions patterns between odonate assemblages in Fennoscandia
Odonate (damselfly and dragonfly) species richness and species occupancy frequency distributions (SOFD) were analysed in relation to geographical location in standing waters (lakes and ponds) in Fennoscandia, from southern Sweden to central Finland. In total, 46 dragonfly and damselfly species were recorded from 292 waterbodies. Species richness decreased to the north and increased with waterbody area in central Finland, but not in southern Finland or in Sweden. Species occupancy ranged from 1 up to 209 lakes and ponds. Over 50% of the species occurred in less than 10% of the waterbodies, although this proportion decreased to the north. In the southern lakes and ponds, none of the species o…
Food availability and the male's role in parental care in double-brooded TreecreepersCerthia familiaris
The aim of this work was to examine differences in paternal and maternal care in a double-brooded, monogamous species, the Treecreeper Certhia familiaris, in relation to food availability. As a measure of parental care, we recorded the hourly feeding activity of parents when the nestlings from their first and second breeding attempts were 7 and 12 days old. Feeding frequency of the first brood increased with the age of the nestlings and also with the brood size when 12 days old. While the feeding activities of the females were similar with respect to the first and second broods, the males were less active and failed to provide any food to their nestlings in 15 cases out of 28 second broods.…
Effects of male removal on female foraging behavior in the Eurasian treecreeper
In old, spruce-dominated forests of central Finland, Eurasian treecreepers Certhia familiaris divide their territories spatially during the breeding season. Females forage primarily on the upper parts of the tree trunks, while males use the lower parts of the tree trunks. In this study we removed males from eight territories in the early nestling period to see if the mate's absence would change the foraging patterns of the resident female. Widowed females foraged at lower heights, thus behaving more like paired males. These females also spent less time on each tree and on each foraging bout than did paired females. We conclude that male removal facilitated the change in a female's foraging …
Intraguild predation and interference competition on the endangered dragonfly Aeshna viridis
We examined the effects of intraguild predation (IGP) and interference competition on an endangered dragonfly, Aeshna viridis Eversm. (Odonata: Anisoptera). A. viridis is rare in Europe due to the decrease in suitable habitats harboring the macrophyte Stratiotes aloides L. Stratiotes plants are the principal oviposition substrate for A. viridis females and protect the larvae of A. viridis from fish predation. In our study lakes A. viridis larvae are sympatric with larvae of Aeshna grandis and Aeshna juncea. The susceptibility of A. viridis larvae to IGP by similar-sized larvae of A. grandis and A. juncea was tested in a laboratory predation experiment. Microhabitat use of A. viridis and A. …
Selecting networks of nature reserves: methods do affect the long-term outcome
Data on vascular plants of boreal lakes in Finland were used to compare the efficiency of reserve selection methods in representing four aspects of biodiversity over a 63 year period. These aspects included species richness, phylogenetic diversity, restricted range diversity and threatened species. Our results show that the efficiency of reserve selection methods depends on the selection criteria used and on the aspect of biodiversity under consideration. Heuristic methods and optimizing algorithms were nearly equally efficient in selecting lake networks over a small geographical range. In addition, a scoring procedure was observed to be efficient in maintaining different aspects of biodive…
Behavioural responses of Eurasian treecreepers, Certhia familiaris, to competition with ants
Competition for a specific resource that is essential for the survival of both the competitors may be intense even between very dissimilar taxa. However, the importance of the effects caused by such interspecific competition has seldom been emphasized. These effects can appear as differences in individual foraging behaviour during the breeding season, which can result in critical variation in fitness. In this study we examined the effects of wood ants (Formica rufa group) on the abundance of other invertebrates on tree trunks and on the foraging site selection of breeding Eurasian treecreepers, which use the same habitat as wood ants. Arthropods were scarcer on the trunks with ants present;…
Do pheromones reveal male immunocompetence?
Pheromones function not only as mate attractors, but they may also relay important information to prospective mates. It has been shown that vertebrates can distinguish, via olfactory mechanisms, major histocompatibility complex types in their prospective mates. However, whether pheromones can transmit information about immunocompetence is unknown. Here, we show that female mealworm beetles (Tenebrio molitor) prefer pheromones from males with better immunocompetence, indicated by a faster encapsulation rate against a novel antigen, and higher levels of phenoloxidase in haemolymph. Thus, the present study indicates that pheromones could transmit information about males' parasite resistance ab…
Coat darkness is associated with social dominance and mating behaviour in a mountain sheep hybrid lineage
Natural hybridization can produce novel traits when morphologically different populations hybridize, and can introduce variation in traits that become associated with sexual selection. Evidence from breeding experiments and genetic markers indicate that the great variation in coat darkness and the unique coat patterns found in Stone's sheep Ovis dalli stonei, populations, have resulted from an ancient hybridization event between thinhorn sheep, O. dalli, and bighorn sheep, O. canadensis. Behavioural evidence gathered in 2003 and 2004 in Yukon Territory, Canada, showed that higher dominance rank was correlated with increasing darkness in rams, and comparatively darker rams were seen more oft…
Immunocompetence and resource holding potential in the damselfly, Calopteryx virgo L
It is generally believed that resource holding potential reliably reflects male quality, but empirical evidence showing this is scarce. Here we show that the outcome of male-male competition may predict male immunocompetence in the territorial damselfly, Calopteryx virgo (Odonata: Calopterygidae). We staged contests between 27 pairs of males and found that winners of the contests showed higher immunocompetence, measured as encapsulation response, compared with that of losers. Furthermore, the winners had larger fat reserves. We also collected 29 males that had not been used in staged contests, and found that in these males encapsulation response correlated positively with an individual’s fa…
Food Caching By Willow and Crested Tits: A Test of Scatterhoarding Models
In coniferous forests of Central Finland, Willow (Parus montanus) and Crest- ed Tits (P. cristatus) store seeds in a scattered distribution within their territory during the autumn. Individuals cache and recover food items while moving together as members of mixed-species flocks. The purpose of this study was to test certain predictions of scatter- hoarding models (Stapanian and Smith 1978, Clarkson et al. 1986), which predict how the animal should hoard food items from a superabundant source to maximize the number of caches recovered. Our field experiments gave support to most of the predictions of the models. Individual tits stored seeds closer to the food source when food had been availa…
Distribution and habitat selection of wintering birds in urban environments
Habitat selection of wintering land-birds was studied in 31 human settlements in Finland. A total of 26 wintering bird species representing 5155 individuals were observed. Between-year variation (CVB%) and short-term fluctuation within one winter (CVW%) in species richness (CVB=10% CVW=15%) were low, as were total numbers of birds (CVB=22% CVW=24%) and populations of the most common bird species (CVB=20–40% CVW=15–47%). The most abundant bird species (e.g., Passer domesticus, Parus major and Pica pica) occurred in most of the study sites. The total densities of omnivorous birds, sedentary birds and bird species that commonly use feeding tables were higher in a heavily urbanized areas than i…
INTERSPECIFIC AGGRESSION CAUSES NEGATIVE SELECTION ON SEXUAL CHARACTERS
Interspecific aggression originating from mistaken species recognition may cause selection on secondary sexual characters, but this hypothesis has remained untested. Here we report a field experiment designed to test directly whether interspecific aggression causes selection on secondary sexual characters, wing spots, in wild damselfly populations. Males of Calopteryx virgo are more aggressive toward males of C. splendens with large than with small wing spots. This differential interspecific aggression may cause negative selection on wing spot size. Indeed, our results show that directional survival selection on wing spot size of C. splendens males was changed by experimental removal of C. …
Founder population size and number of source populations enhance colonization success in waterstriders.
Understanding the factors that underlie colonization success is crucial both for ecological theory and conservation practices. The most effective way to assess colonization ability is to introduce experimentally different sets of individuals in empty patches of suitable habitat and to monitor the outcome. We translocated mated female waterstriders, Aquarius najas, into 90 streams that were not currently inhabited by the species. We manipulated sizes of propagules (from 2 to 16 mated females) and numbers of origin populations (one or two). Three origin populations were genetically different from each other, but they were less than 150 km from the streams of translocation. The results demonst…
Hot spots, indicator taxa, complementarity and optimal networks of taiga
If hot spots for different taxa coincide, priority-setting surveys in a region could be carried out more cheaply by focusing on indicator taxa. Several previous studies show that hot spots of different taxa rarely coincide. However, in tropical areas indicator taxa may be used in selecting complementary networks to represent biodiversity as a whole. We studied beetles (Coleoptera), Heteroptera, polypores or bracket fungi (Polyporaceae) and vascular plants of old growth boreal taiga forests. Optimal networks for Heteroptera maximized the high overall species richness of beetles and vascular plants, but these networks were least favourable options for polypores. Polypores are an important gro…
REPRODUCTIVE SUCCESS OF EURASIAN TREECREEPERS,CERTHIA FAMILIARIS,LOWER IN TERRITORIES WITH WOOD ANTS
Few studies have considered the effects of interspecific competition between distantly related taxa on the reproductive success of individuals. We compared the food supply, laying date, clutch size, and breeding success of a small double-brooded passerine bird, the Eurasian Treecreeper (Certhia familiaris) between territories with or without col- onies of red wood ants (Formica rufa group) during four years. Both the wood ants and Eurasian Treecreepers forage on tree trunks and utilize the same food resources. It has been shown that the wood ants are able to depress the available food supply for the treecreepers and interfere with their foraging behavior. We found that food abundance was lo…
Evolution of foraging ecology in Fennoscandian tits ( Parus spp.)
Species belonging to the same genus exploit similar resources in a similar manner. Despite their general similarities in behaviour, they differ in morphology, and these differences are often interpreted as adaptations for use of different resources. Here we report on the relation between morphology, habitat selection and feeding ecology in seven tit species (Parus spp.) in Fennoscandia. A problem previously disregarded in most ecomorphological studies is that members of a guild with closely related species share their common ancestry. This historical legacy causes similarity in ecology and morphology. We have used phylogenetic information with proper comparative methods to reveal the evolut…
Age-dependent responses to alarm calls depend on foraging activity in Willow TitsPoecile montanus
Survivorship in animals depends on both foraging activities and avoidance of predation, and thus behavioural decisions often reflect a trade-off between predation risk and foraging efficiency. In this experimental study, we compared behavioural responses of free-living adult and juvenile Willow Tits Poecile montanus to a conspecific alarm call in two treatments. The alarm call was played back when a focal bird was either not feeding, or feeding on a sunflower seed on the middle part of a spruce branch. When feeding at the time of the alarm call, juveniles more often stayed motionless or moved shorter distances than adults. Our results suggest that in hierarchical groups, juveniles are force…
Risk of Local Extinction of Odonata Freshwater Habitat Generalists and Specialists
Understanding the risk of a local extinction in a single population relative to the habitat requirements of a species is important in both theoretical and applied ecology. Local extinction risk depends on several factors, such as habitat requirements, range size of species, and habitat quality. We studied the local extinctions among 31 dragonfly and damselfly species from 1930 to 1975 and from 1995 to 2003 in Central Finland. We tested whether habitat specialists had a higher local extinction rate than generalist species. Approximately 30% of the local dragonfly and damselfly populations were extirpated during the 2 study periods. The size of the geographical range of the species was negati…
Age Differences in the Response of Willow Tits (Parus montanus ) to Conspecific Alarm Calls
Predation is an important mortality factor in wintering birds. To counter this, birds produce alarm calls in the presence of predators which serve to warn conspecifics. In social hierarchical bird flocks, adults survive the winter better than juveniles and therefore survival strategies probably vary with social status. This study examined the differential responses to alarm calls by free-living willow tits, Parus montanus, in dominance-structured winter flocks in Finland. To explore the age-dependent differences in response to conspecific alarm calls, a series with three alarm calls was played to focal adults and juveniles while they sat in the middle section of a spruce branch. Immediately…
Local Extinction of Dragonfly and Damselfly Populations in Low- and High-Quality Habitat Patches
Understanding the risk of extinction of a single population is an important problem in both theoretical and applied ecology. Local extinction risk depends on several factors, including population size, demographic or environmental stochasticity, natural catastrophe, or the loss of genetic diversity. The probability of local extinction may also be higher in low-quality sink habitats than in high-quality source habitats. We tested this hypothesis by comparing local extinction rates of 15 species of Odonata (dragonflies and damselflies) between 1930-1975 and 1995-2003 in central Finland. Local extinction rates were higher in low-quality than in high-quality habitats. Nevertheless, for the thre…
Influence of alternative mating tactics on predation risk in the damselfly Calopteryx virgo
Alternative mating tactics are a widespread feature in insects. A typical form of alternative mating behaviour is being a sneaker in the vicinity of a territorial male. Such nonterritorial males have lower mating success, but they may benefit from lower energetic costs and decreased predation risk. In this study, we examined whether nonterritorial male damselflies Calopteryx virgo (L., 1758) are subject to lower predation risk than territorial males. To distinguish predation from other sources of mortality, we used models. The experiment consisted of dried male damselflies settled into the typical perching positions of territorial and nonterritorial males. Also the spatiotemporal patterns …
Interspecific territoriality in Calopteryx damselflies: the role of secondary sexual characters
Interspecific territoriality is usually interpreted to result from interspecific interference competition, although it may also originate from mistaken species recognition. In the latter case, it may be based on similarity of secondary sexual characters. In the damselfly Calopteryx splendens, males have pigmented wing spots as a sexual character, and males with the largest spots resemble males of another species, Calopteryx virgo. Probably because of this resemblance, C. virgo males are more aggressive towards large- than small-spotted C. splendens males. We examined whether wing spot size of C. splendens males affects territorial interactions between the species. In a removal experiment, t…
Horn growth rate and longevity: implications for natural and artificial selection in thinhorn sheep (Ovis dalli).
We used horn measurements from natural and hunted mortalities of male thinhorn sheep Ovis dalli from Yukon Territory, Canada, to examine the relationship between rapid growth early in life and longevity. We found that rapid growth was associated with reduced longevity for sheep aged 5 years and older for both the hunted and natural mortality data sets. The negative relationship between growth rate and longevity in hunted sheep can at least partially be explained by morphologically biased hunting regulations. The same trend was evident from natural mortalities from populations that were not hunted or underwent very limited hunting, suggesting a naturally imposed mortality cost directly or in…
Predator presence may benefit: kestrels protect curlew nests against nest predators.
We studied whether the presence of breeding kestrels (Falco tinnunculus) affected nest predation and breeding habitat selection of curlews (Numenius arquata) on an open flat farmland area in western Finland. We searched for nests of curlews from an area of 6 km2 during 1985–1993. For each nest found, we recorded the fate of the nest, and the distance to the nearest kestrel nest and to the nearest perch. We measured the impact of breeding kestrels on nest predation by constructing artificial curlew nests in the vicinity of ten kestrel nests in 1993. Curlew nests were closer to kestrel nests than expected from random distribution, eventhough kestrels fed on average 5.5% of curlew chick produc…
Condition dependence of pheromones and immune function in the grain beetleTenebrio molitor
Summary 1. Pheromones are chemical signals that function not only as mate attractors, but may also relay important information to prospective mates. In order for the information to be reliable, the signal must be costly to produce and this is likely to result in condition dependent expression of the signal. 2. We present results from two experiments on the grain beetle Tenebrio molitor examining phenotypic condition dependence of pheromones and patterns of female preference for pheromones. We also analysed condition dependence of two measures of immunocompetence: encapsulation response and phenoloxidase activity. 3. By manipulating the nutritional condition of the males we found that the at…
Younger bank voles are more vulnerable to avian predation
The importance of predation on prey populations is mainly determined by the number of eaten prey. However, the total impact of predation might also be determined by the selection of certain prey individuals, e.g., different sexes or age categories. Here we tested selective predation by an avian predator, the pygmy owl ( Glaucidium passerinum (L., 1758)), on bank voles ( Myodes ( Clethrionomys ) glareolus (Schreber, 1780)). We compared the sex, age, and mass of hoarded prey with the animals snap-trapped from the field. There were no differences in the sex ratio between hoarded bank voles and those available in the field. However, hoarded voles were significantly younger than ones in the fie…
Immunocompetence, developmental stability and wingspot size in the damselflyCalopteryx splendensL.
Calopteryx splendens males exhibit a remarkable variation in wing pigmentation both within and between populations. In this study, we examined whether the wingspots of male C. splendens are related to male quality. We measured the nylon implant encapsulation rate for 85 males and found that males with larger wingspots had a faster encapsulation rate, indicating a better immunocompetence. We also found that the encapsulation rate was positively correlated with the density of haemocytes in the haemolymph. Another measurement of male quality, fluctuating asymmetry of wingspots, correlated negatively with the size of the wingspots. Males with asymmetrical wingspots also had lower encapsulation …
Risk of predation and foraging sites of individuals in mixed-species tit flocks
Abstract Abstract. Foraging sites of individual willow tits, Parus montanus, and crested tits, P. cristatus, on spruce were studied in a winter when the risk of predation from pygmy owls, Glaucidium passerinum, was high and in a winter when it was low. Mixed-species flocks consisted of two crested tits (a pair) and three to six willow tits. The risk of predation from owls is likely to be highest on the most exterior tree parts. Female crested tits foraged further out on the branches than other individuals when predation risk was low, but foraged in the safer sites close to the tree trunk when the risk was high. Male crested tits retained both their relative distance to the trunk and their r…
Effect of Willow TitPoecile montanusalarm calls on attack rates by Pygmy OwlsGlaucidium passerinum
One suggested anti-predator function of alarm calls is to deliver a message to a predator that it has been detected. Moreover, giving the alarm call could provide a signal to the predator that capturing the individual giving the alarm is more difficult than capturing its silent group members, as the caller is probably the most aware of the predator's location. In an aviary experiment using stuffed dummy Willow Tits Poecile montanus, we assessed whether an authentic alarm call given by Willow Tit affected Pygmy Owl Glaucidium passerinum prey preference. In the experiment, the Owls attacked only the ‘silent’ dummy individuals, suggesting that alarm calling could offer direct fitness benefits …
Biogeographical comparison of winter bird assemblages in urban environments in Finland
We studied biogeographical variation of urban bird assemblages in Finland. Winter birds were censused by single-visit study plot method from thirty-one centres of villages or towns along 950 km latitudinal extent. A total twenty-eight bird species was observed and the average density was 61.2 ind./10 ha. The number of dominant species in study areas varied between two and seven and their proportion of the whole assemblage was over 70%. Species richness, but not the density of birds, decreased northwards in pooled data. Higher species richness in south than in north was mainly due to the higher amount of delayed migratory birds (e.g. waterbirds, finches) and southerly distributed bird specie…
The macrophyte, Stratiotes aloides, protects larvae of dragonfly Aeshna viridis against fish predation
Predation could be one force determining which contemporary species occupy a certain habitat. Aeshna viridis is an endangered dragonfly species with a larval distribution strongly associated with lakes where the water plant, water soldier, Stratiotes aloides, occurs. In this study, the larvae were almost exclusively found in patches of S. aloides. To study larval association with S. aloides further, we conducted a series of laboratory experiments. Behavioural experiments indicated that larvae preferred S. aloides. Aeshna viridis larvae were nocturnal and rather inactive. Larvae on S. aloides were less susceptible to predation by the perch, Perca fluviatilis, than larvae on another water pla…
Fluctuating asymmetry and immune function in a field cricket
Recently, fluctuating asymmetry (FA) of morphological traits has attracted great attention as a short-cut measure of individual quality. Whereas there is some evidence that FA of sexual ornaments is negatively associated with immune function, studies concerning FA and immune function in non-ornamental traits are absent. Here, we tested whether FA of three non-ornamental traits in hind limbs is related to male immune function in a population of the Mediterranean field cricket, Gryllus bimaculatus. As different measures of male immune function, we used encapsulation rate and lytic activity. We found that a composite measure of FA (cFA) was negatively related to encapsulation rate. However, ly…
Hybridization in Calopteryx damselflies: the role of males
Females are often considered responsible for hybridization between two species because usually they are the choosier sex and their cooperation is needed for successful copulation. However, males can also be responsible for hybridization, for example in species in which males are able to force copulation. We studied the pattern of hybridization in two congeneric damselfly species, Calopteryx splendens and Calopteryx virgo, and provide evidence that F1 hybrids between the two damselfly species occur in the wild. According to mitochondrial DNA analysis, hybridization is reciprocal: five of seven hybrids were sired by C. splendens and two by C. virgo males. We conducted an experiment that revea…
Population Persistence and Offspring Fitness in the Rare Bellflower Campanula Cervicaria in Relation to Population Size and Habitat Quality
Data from several animal species and a few plant species indicate that small populations face an elevated risk of extinction. Plants are still underrepresented in these studies concerning the relation between population size and persistence. We studied the effect of population size on persistence among natural popu- lations of the rare bellflower Campanula cervicaria in Finland. We monitored 52 bellflower populations for 8 years and found that the mean population size decreased from 24 to 14 during this period. Small popula- tions with # 5 individuals were more prone to losing all fertile plants than were larger ones. Reduction in population size was nevertheless unrelated to the degree of …
Interspecific aggression and character displacement in the damselfly Calopteryx splendens
Problems in species recognition are thought to affect the evolution of secondary sexual characters mainly through avoidance of maladaptive hybridization. Another, but much less studied avenue for the evolution of sexual characters due to species recognition problems is through interspecific aggression. In the damselfly, Calopteryx splendens, males have pigmented wing spots as a sexual character. Large-spotted males resemble males of another species, Calopteryx virgo, causing potential problems in species recognition. In this study, we investigate whether there is character displacement in wing spot size and whether interspecific aggression could cause this pattern. We found first that wing …
Conservation of vascular plants in single large and several small mires: species richness, rarity and taxonomic diversity
1. This study on vascular plant species of boreal spruce and pine mires concentrated on two geometrical principles: whether single large or several small (SLOSS) reserves contain more species and whether patch shape should be as nearly circular as possible. 2. SLOSS and patch shape have usually been tested by using species richness. Only a few studies have taken the rarity of species into account, and taxonomic diversity has never been used. In our study, all three of these factors were used. 3. Our results showed that the number of species was not related to the spruce mire size, but it increased in relation to the pine mire size. In contrast, the rarity score increased in relation to the …
Urbanization and stability of a bird community in winter
Abstract: The main objective of this study was to analyze between-winter stability of bird communities along latitudinal (950 km) and urban gradients (from small village to towns) in Finland. Birds were surveyed at the same 30-ha study plots using the same methods in 31 villages and town centres in the winters of 1991–1992 and 1999–2000. Species richness did not differ between the 2 study winters, but variation in total abundance of birds increased with increasing urbanization. However, urbanization reduced variation in wintering bird community structure. Species richness, density of wintering birds, and dissimilarity of wintering bird communities did not vary with latitude. According to ou…
Selection on size and secondary sexual characters of the damselfly Calopteryx splendens when sympatric with the congener Calopteryx virgo
Male mating success is often determined by body size or secondary sexual characters because of female mate choice or competition for females. In addition to intraspecific interactions, interspecific interactions may interfere with intraspecific selection. In this study, we investigated sexual selection on size and sexual characters of male banded demoiselle ( Calopteryx splendens (Harris, 1780)) in wild populations sympatric with the beautiful demoiselle ( Calopteryx virgo (L., 1758)). As secondary sexual characters, male C. splendens have pigmented wing spots whose size appears to be under positive selection. Male C. virgo resemble male C. splendens that have the largest wing spots, leadi…
Geographical patterns of species turnover in aquatic plant communities
1. A classic theory in biogeography predicts that high latitude communities are unstable. This may be because of decreased species richness or decreased environmental predictability and productivity towards the poles. 2. We studied latitudinal patterns in long-term community persistence of aquatic vascular plants in 112 Finnish lakes, situated within a 1000-km range from the northernmost to the southernmost lake. 3. Contrary to theoretical predictions, we found that the turnover rate of plant species in 45 years was inversely related to latitude. That is, plant communities in northern lakes were more persistent than communities in southern lakes. When we used multiple regression to find the…
Appendix A. Phylogenetic classification of vascular plants in boreal herb-rich forests.
Phylogenetic classification of vascular plants in boreal herb-rich forests.