My research interest is conservation biology and to improve our understanding of what affects species’ survival and dispersal in landscapes affected by human presence. My main focus is in entomology. Another field of research that I am working in is ecological questions around entomophagy - insects as a food source. My research in this emerging field focus on insect ecology and related biodiversity issues. Our research group has a blog: http://blogg.slu.se/crickets-as-sustainable-food/
Skills and Expertise
BiodiversityConservation BiologyEcology and EvolutionConservationEcologySpecies DiversityWildlife ConservationInvasive SpeciesWildlife EcologyBiodiversity MonitoringCommunity EcologyConservation EcologyLandscape EcologyWildlife ManagementSpatial StatisticsBiodiversity AssessmentDistributionEntomologyInsectMonitoringWildlifeMicrosatellitesFragmentationAgricultural ScienceHabitatSpeciesOrthoptera
Jul 2010 - Jun 2016
Department of Ecology,
- Swedish University of Agricultural Sciences
- Head of the Department of Ecology
May 2004 - May 2008
Swedish University of Agricultural Sciences
- Department of Ecology
- Uppsala, Sweden
- Assistant Professor
Awards & Achievements (2)
Award · Jan 2014
Pedagogic Prize awarded to the teacher collective
Award · Jan 1997
His Majesty the King Karl XIV 50-year fund
Insects show a promise as food source for humans, but most around insects used this way is unknown. We study different aspects of entomophagy including insect ecology, nutrition, behaviour and land-use.
In this project we focus on the spatial diversity pattern of springtail (Collembola) populations and communities. The aim it to understand at what scales communities are structured and how much of species turnover that can be explained by distance between sampling plots alone, compared with the effect of environmental variables.
Research Item (64)
This study evaluated diets including whole or peeled (legs removed) crickets (Teleogryllus testaceus) in terms of diet digestibility, growth and nitrogen retention, using pigs as an animal model. The experiment included three isonitrogenous diets (18.4% crude protein) including either whole cricket meal (WC), body cricket meal (legs removed, BC) or fish meal (control) as the main protein source. Castrated male piglets (n=21, 30-45 days) with initial body weight 13.0±0.3 kg were allocated to one of the dietary treatments (7 piglets/treatment) in a fixed block design. The piglets were kept in single bamboo/wooden stalls with slatted floors and were adapted to the feeds and the housing for 5 days before starting the 25-day experiment. The diets were offered ad libitum, but close to appetite (approximately 5% of body weight). Feed intake was recorded and piglets were weighed every 5 days. During days 20-25, total collection of faeces and urine was performed. Dry matter and nutrient intake were higher for piglets fed the WC and BC diets than for those fed the control diet. From day 10, piglets fed BC and WC were heavier than piglets fed the control diet, but there were no differences between WC and BC. Dry matter digestibility was highest for diet WC, and ash, crude fibre and crude fat digestibility was higher for BC and WC than for the control diet. Feed conversion ratio was lower for the WC and BC diets than for the control diet, and nitrogen retention (% of digested) was higher. We concluded that field cricket meal is a nutritious feedstuff for mono-gastric animals, and most likely also for humans. Removal of legs did not facilitate or improve the digestibility values and nitrogen retention. Thus, in order to minimise food waste, crickets should not be peeled in this way if they are going to be processed into meal.
Species range shifts associated with environmental change or biological invasions are increasingly important study areas. However, quantifying range expansion rates may be heavily influenced by methodology and/or sampling bias. We compared expansion rate estimates of Roesel's bush-cricket (Metrioptera roeselii, Hagenbach 1822), a nonnative species currently expanding its range in south-central Sweden, from range statistic models based on distance measures (mean, median, 95th gamma quantile, marginal mean, maximum, and conditional maximum) and an area-based method (grid occupancy). We used sampling simulations to determine the sensitivity of the different methods to incomplete sampling across the species' range. For periods when we had comprehensive survey data, range expansion estimates clustered into two groups: (1) those calculated from range margin statistics (gamma, marginal mean, maximum, and conditional maximum: ˜3 km/year), and (2) those calculated from the central tendency (mean and median) and the area-based method of grid occupancy (˜1.5 km/year). Range statistic measures differed greatly in their sensitivity to sampling effort; the proportion of sampling required to achieve an estimate within 10% of the true value ranged from 0.17 to 0.9. Grid occupancy and median were most sensitive to sampling effort, and the maximum and gamma quantile the least. If periods with incomplete sampling were included in the range expansion calculations, this generally lowered the estimates (range 16–72%), with exception of the gamma quantile that was slightly higher (6%). Care should be taken when interpreting rate expansion estimates from data sampled from only a fraction of the full distribution. Methods based on the central tendency will give rates approximately half that of methods based on the range margin. The gamma quantile method appears to be the most robust to incomplete sampling bias and should be considered as the method of choice when sampling the entire distribution is not possible.
The bush-cricket Metrioptera roeselii is an example of an insect which has expanded its indigenous range beyond expectations based on its natural dispersal potential. Understanding how species colonize new areas is vital for formulating effective species conservation programmes and managing invasive species. The aim of this research is to use mitochondrial sequence and microsatellite data to delineate the likely origin and dispersal pathways of M. roeselii in northern Europe. The well-known ecology of the species and the detailed colonization data make it a very suitable model species for addressing questions relating to invasiveness.
1. Individual movement behaviours of male Roesel's bush crickets were compared between individuals experimentally released with or without conspecifics.2. Differences in movement behaviour were recorded between the groups, with individuals released with conspecifics moving faster and further.3. The study shows that behavioural interactions between individuals need to be considered in population modelling. Empirical movement data derived from lone individuals would result in a significant underestimation of both population expansion (−38.1%) and inter-patch movement (−35.8%).
Insect production has been suggested as a food production system that could be more sustainable than many conventional livestock systems. Insects are a promising source of nutrients for humans containing high amounts of good quality protein, fatty acids, vitamins and minerals. A sustainable insect industry could have large impacts on land use, ecology and conservation. However, much around insects as a food source are unknown and only a small number of species have been used as livestock. Plenty of new information and understanding is needed if we are to develop food production systems and mass rearing of insects. The promise and also challenge of this food system is to develop it in a sustainable manner that permeates all parts of the production chain. This means that choice of species, rearing facilities, and resource use in terms of feed and energy are core components that needs to be evaluated within a sustainable framework. We suggest important key factors within these components that can guide the way for the future development of insect as minilivestock. These include that insect species chosen should be native so they do not contribute to the increasing invasion problem facing both natural and production systems. The species should have a potential to utilise plant products that cannot be used for humans as food. The animals thereby do not compete with humans for food resources, as is the case of many current food systems. Promising insect taxa are leaf chewers, which include species from the families’ orthoptera, coleoptera and phasmatodea. An evaluation of sustainable resource and energy use indicate that western countries relying heavily on fossil fuel will have harder to reach goals in these areas of the food system.
Question - GMO insects for food and feed?
Ok didn't know that :). Sounds good and interesting!
Question - GMO insects for food and feed?
Hi, Haven't seen or heard anything about it. Very interesting topic and will be on the agenda sooner than later is my guess. There are several people working on GMO and food at SLU (Project MistraBiotech) that I have talked with about insects as food, but as far as I know, they do not work on anything related to this yet. They do podcasts on GMO and food, but they might be in Swedish https://www.slu.se/shapingourfood_podcast Greetings, Åsa
Project - Orthopteran Ecology
We have just published a paper (se new papers) where we have looked at the Cambodian field cricket (Teleogryllus testaceus) as a food source for pigs and got some interesting results!
Project - Entomophagy - the eating of insects - as a sustainable food source
We have just published a paper studying the effect of crickets as food source for pigs (se RG page & publications) and found that they grew really well (see paper). Pigs are not humans :) but are often used as human models in different studies
Project - Orthopteran Ecology
Understanding the effects of the environment on orthopteran (grasshoppers, crickets, bush-crickets) health, morphology, genetics, survival and distribution.
Background and motivation
Orthopteran species are numerous and widely distributed over the world. Some species are threatened and conservation efforts are in place, other species are regarded as invasive as they affect the systems they enter in a negative way. We study how the environment affect species: at an individual and a population level, in the wild and in the lab, and in short- and long-term time-frames.
Question - Do you, someone you know or other people within your country have insects as a part of their diet?
Thanks! Its blocket from viewing here, but I'll find its somehow.
Question - Do you, someone you know or other people within your country have insects as a part of their diet?
Great info from you all thanks and so interesting to hear from different traditions and experiences. Love to get some more knowledge about this from other areas as well!
We are interested in finding out more how widespread entomophagy (the eating of insects) is in countries around the world. In some countries it has a very long tradition and in some countries its a new behaviour. So would great to hear about what you know about your country in this respect.
This study evaluated survival and growth of Cambodian field crickets (Teleogryllus testaceus) during captivity when fed a set of local weed species, agricultural and food industry by-products. Wild individuals were caught at two locations in Cambodia, kept in pens and fed commercial chicken feed until the second generation off-spring hatched. First larval stage nymphs from this generation were collected and used in a 70-day feeding trial with one control treatment (chicken feed) and 12 experimental treatments (rice bran, cassava plant tops, water spinach, spent grain, residue from mungbean sprout production, and Alternanthera sessilis, Amaranthus spinosus, Commelina benghalensis, Cleome rutidosperma, Cleome viscosa, Boerhavia diffusa and Synedrela nodiflora). The crickets were kept in plastic cages and feed intake, weight and survival of crickets were recorded weekly. Overall survival did not differ between chicken feed and the experimental treatments with the exception of crickets fed B. diffusa, which had lower survival. From day 35 to day 49, survival on A. sessilis was also lower (P<0.05) than on chicken feed. There was no difference in weight between crickets fed chicken feed, cassava tops and C. rutidosperma. However, crickets fed A. sessilis, A. spinosus and B. diffusa weighed less than those fed chicken feed already at day 21. The feed conversion rate ranged from 1.6 to 3.9 and was ≤1.9 in crickets fed chicken feed, cassava plant tops and C. rutidosperma. Thus this study shows that it is possible, using simple means, to rear Cambodian field crickets. Cassava plant tops and C. rutidosperma both have great potential as cricket feed and the other weeds, with the exception of A. sessilis, A. spinosus and B. diffusa, agricultural and food industry by-products tested, also showed potential.
Question - Marking for capture and recapture Carabus species ?
We have marked bush-crickets with both pens (different colours and makes) and bought and done self-made stickers glued (fast acting glues) to their back. It has worked pretty well but all different marking will be lost with time. My guess is that it is substances from the cuticula that loosen up anything attached/painted. For tags we have used markers commonly used to mark domestic bee queens and they come in different colours and with numbers (can be ordered on bee keepers sites). We have also used tags that we have cut out ourselves from reflexive plastics/textiles where we have printed numbers on. In most of our studies we have been interested to separate individuals, but if you don't want hat no printing is needed of course. They good ting with reflexive markers is that you can look for your individuals in the dark using a head lamp (get additional data or find more if they are hard to find). To minimise any injuring during marking we have cooled individuals down so that they are relatively still in our hands.
Question - Sir i want to study biodiversity of grasshopper , how i should start the collection?
It depends on what your questions are. Maybe you want to study how diversity (eg. number of species) is related to different habitats or management of these habitats? When you have your questions clear, you design a survey method that will give you enough replicates of the different ingoing variables you are interested in (eg. 30 areas managed in way A and 30 areas managed in way B). You then survey these areas for grasshoppers in a fashion that make them all comparable (eg. time/area). Grasshoppers are often surveyed by listening for their species-specific call, but not all species (or sexes) call. Walking transects through the habitats are common and gathering and noting down that calls and sightings whilst doing this. You need to know what you heard see, so studying literature (including recordings) before heading out is a must.Hope that helped you a bit. Best of luck!
Question - Does anyone know about "The index of breadth of geographic range? and what is the formula?
Hi, There are several ways to measure the geographic range of s species. We have used different methods depending on the scale we have worked on and the species data (quality & amount) that we had. One way if you have a reasonable amount is to place a grid over that area and calculate the distribution area. Another way is if you know the approximate limit of the species distribution you can use this limit data to calculate distribution (and its changes) (we have done some papers on this if you want to have a look). You can also do what is done a lot when working on red listed species, to calculate the minimum convex polygon around known species localities (basically draw lines between localities). From this you get a distribution area measurement, often a bit cruder, but so is often the data we have on many species' distributions. I think finding which method best fit you taxa and the amount and quality of the data is what is most important for you study.
Question - Is the anonymous downvoting helpful?
As a relatively new user of Researcgate my thought is that it can also be a factor that user do not know the action fully and what it means? I agree that it would be useful with some feedback. Maybe just a comments line that shows up that one can write in? Best regards, Åsa
Question - Grasshoppers as food?
Hi, Let me know how it is going, do you have any results from your rearing yet? I am also interested in this subject and one taxa we will start working with now is also an orthopteran. I have raised orthopterans before, but for other ecological studies. It has not been much done yet as far as I have seen. Most experience is still from the pet food industry.
Question - How can I measure the wing length of living beetles?
I cool individuals in the fridge when measuring orthopterans.We have used micro enhancers (x 10) with built in rulers. Be careful of course and be prepared to re-chill as individuals tend to get warm quickly and start to wiggle. Then there is an increased risk of damage to legend wings.
Question - How identify grasshopper?
Hi, Do you have a photo or drawing? If you don't have that many species can also be identified from their call (stridulation).
Question - In which country are insects the most popular human food and what kinds of insects?
Hi, Even though most insect species are eaten in Asia, Africa and South America (FAO 2013. Edible insects: Future prospects for food and feed security. Forestry paper, 171: 1-154.), I think that there are indications that North America and Europe might follow. So far much of the work in these regions has been focused on producing minced insects for protein bars, but I think that will change. I and my colleagues are currently starting research focused on native species and focusing on a large spectrum och ecological, physiological and social science questions in relation to entomophagy. If you have any papers I'd love to read them.
Question - Is anybody working on the ethical aspects of the plans to use insects for food and feed in the future - especially from an animal ethics perspective?
Hi, Interesting field and something that we also are interested in. An unpublished survey that my colleague has done (A Jansson, unpublished) show a positive attitude in students (young people) to eat insects and from discussing with students and public at lectures and seminars about entomophagy I get the impression that a part of this can be that people feel that it doesn't feel as "bad" eating insects as other vertebrate animals. If you have published anything I'd love to read it. In Sweden where I work, you don't need ethics approval for working with insects (ecological research) which is an index of course that we do not regard insects the same way as other taxa.
Residuals of four genetic measures plotted against geographic distance (km) from the range centre and towards the range edge. There was a positive correlation between distance and variability around the mean for all estimates (AR: p = 0.012, UHe: p = 0.003 and FIS: p = 0.009) except for PAR, for which the correlation was negative
Metrioptera roeselii microsatellite markers. Primer names, GenBank accession numbers, fluorescent dyes, PCR multiplex and mean number of alleles corrected for sample size for the 13 microsatellite loci used. Forward (5’-3’) primers were directly labelled with FAM (blue), VIC (green), NED (black) or PET (red) fluorescent dye
Identifying sources of range expansions after an introduction event and understanding the species dispersal are essential for effective management of invasive species. In a unique study system we investigated the spread and distribution of genetic diversity subsequent to a known colonization event and in the light of the well-known biology of the rapidly expanding Roesel’s bush-cricket (Metrioptera roeselii), a species that is non-native in Sweden. Using eight microsatellite markers we analyzed genetic variation in 837 individuals collected at 29 sites across the species total range in central Sweden to verify the species local origin and to determine how the species known dispersal biology affect the population genetic structure throughout its range. We found that unique allelic richness was highest in a site approximately 16 km southwest of the previously suggested site of establishment, pointing towards a site of introduction close to a royal stud farm from where it is known that animals have been imported from Europe. Despite the species rapid expansion, genetic diversity in the core of the distribution was higher than in the populations at the range margin. Bayesian cluster analyses also revealed that genetic structuring was more pronounced in the range margin, indicating the occurrence of dichotomous dispersal behaviour of the species with occasions of rare long distance events. Our study shows that good sampling design and appropriate choice of genetic markers can help to identify species local origin and explain genetic patterns that arise during range expansions.
Context Habitat heterogeneity is often assumed to benefit farmland biodiversity. Increasing heterogeneity of non-crop habitats is often too costly in terms of agricultural production. It has been suggested that increased crop heterogeneity could mitigate the negative effects of intensification on biodiversity while still maintaining high production levels. Objectives We investigated if habitat-specific species pools of two groups of farmland birds, field-nesting and non-crop-nesting species, were related to landscape-level heterogeneity of crop and non-crop cover. We analysed total number of species (gamma diversity) and average local species richness (alpha diversity) in landscapes and related these two biodiversity measures to four components of landscape heterogeneity (compositional and configurational heterogeneity of crop and non-crop cover). Methods We selected 30 farmland landscapes (each 25 km2) in Sweden that largely broke up correlated relationships between crop and non-crop heterogeneity and between compositional and configurational heterogeneity. Estimates of species richness (alpha and gamma diversity) were calculated with bird survey data from specific habitats within landscapes (farmsteads and arable fields) and then related to measures of landscape heterogeneity. Results No measure of landscape species richness was associated with landscape-scale crop cover heterogeneities. However, gamma diversity of both bird groups was negatively related to the compositional and configurational heterogeneity of non-crop land-use in the landscapes, respectively. Conclusions Our results suggest that: (i) crop heterogeneities are not related to habitat-specific richness of farmland birds, (ii) heterogeneity effects of habitat complementarity in general are weak and (iii) relationships between diversity and heterogeneity in landscapes are dependent on the biodiversity measure used.
Both the environment and the spatial configuration of habitat patches are important factors that shape community composition and affect species diversity patterns. Species have traits that allow them to respond to their environment. Our current knowledge on environment to species traits relationships is limited in spite of its potential importance for understanding community assembly and ecosystem function. The aim of our study was to examine the relative roles of environmental and spatial variables for the small-scale variation in Collembola (springtail) communities in a Dutch salt marsh. We used a trait-based approach in combination with spatial statistics and variance partitioning, between environmental and spatial variables, to examine the important ecological factors that drive community composition. Turnover of trait diversity across space was lower than for species diversity. Most of the variation in community composition was explained by small-scale spatial variation in topography, on a scale of 4–6 m, most likely because it determines the effect of inundation, which restricts where habitat generalists can persist. There were only small pure spatial effects on species and trait diversity, indicating that biotic interactions or dispersal limitation probably were less important for structuring the community at this scale. Our results suggest that for springtails, life form (i.e. whether they live in the soil or litter or on the surface/in vegetation) is an important and useful trait to understand community assembly. Hence, using traits in addition to species identity when analysing environment–organism relationships results in a better understanding of the factors affecting community composition. Electronic supplementary material The online version of this article (doi:10.1007/s00442-015-3345-z) contains supplementary material, which is available to authorized users.
Information on exotic species' current and potential distribution is vital for decisions on management. Species distribution models can predict where colonizations are likely; however, the collection of species' distribution data over large areas in order to parameterize the models is costly. Therefore, modelling methods that are able to use low-cost information such as citizen-reported data are potentially very useful. In this study, we used the species habitat modelling program Maxent to predict the potential geographical distribution of two non-native insect species in Sweden, the butterfly Araschnia levana and the shield bug Graphosoma lineatum. For this we used citizen-reported presence-only open-access data in combination with climate and land cover data from national databases. Our models showed that presence of A. levana was best predicted by winter temperature and habitats related to open grasslands. For G. lineatum, summer temperature and open green areas, in both urban and rural areas were the best predictors for species presence. These models show that large areas of non-colonized potential habitats exist within Sweden. For A. levana these yet-to-be-colonized habitats are mainly in the south, while for G. lineatum these habitats occur in the south and along the Baltic Sea coast. Comparisons of temporal patterns in species reporting for A. levana and G. lineatum to similar insects with known stable populations revealed large 'willingness to report' effects that could potentially bias range expansion rates. Once corrected for, current distribution expansion rates were estimated as 1.9 km/yr and 1.07 km/yr respectively. The study shows the use of public reports in conservation science as a way of gathering species information over large areas. This increases the data sources available for researchers to predict the distribution of species and have the additional value of the involvement of the public in conservation efforts.
Newly founded isolated populations need to overcome detrimental effects of low genetic diversity. The establishment success of a population may therefore depend on various mechanisms such as assortative mating, purging of deleterious alleles, creation of new mutations and/or repeated inflow of new genotypes to reduce the effects of inbreeding and further loss of genetic variation. We compared the level of genetic variation in introduced populations of an insect species (Metrioptera roeselii) far beyond its natural distribution with levels found in their respective founder populations and coupled the data with timing since establishment. This allowed us to analyze if the introduced populations showed signs of temporal changes in genetic variation and have made it possible to evaluate underlying mechanisms. For this, we used neutral genetic markers, seven microsatellite loci and a 676-bp-long sequence of the mtDNA COI gene. All tested indices (allelic richness, unbiased expected heterozygosity, effective size, haplotype diversity, and nucleotide diversity) except inbreeding coefficient had significantly higher values in populations within the founding populations inside the continuous area of the species distribution compared with the introduced populations. A logarithmic model showed a significant correlation of both allelic richness and unbiased expected heterozygosity with age of the isolated populations. Considering the species' inferred colonization history and likely introduction pathways, we suggest that multiple introductions are the main mechanism behind the temporal pattern observed. However, we argue that influences of assortative mating, directional selection, and effects of an exceptional high intrapopulation mutation rate may have impacts. The ability to regain genetic diversity at this level may be one of the main reasons why M. roeselii successfully continue to colonize northern Europe.
Apalus bimaculatus (Linnaeus) (Coleoptera: Meloidae) is a beetle currently managed for conservation in Sweden. The species inhabits at-risk ephemeral and patchily distributed sandy habitats. However, little is known about its ecology and the factors important for its distribution. We censused 158 discrete sand patches within 31 potential sites for A. bimaculatus and examined which environmental variables predicted the probability of finding the beetle. Apalus bimaculatus was found at 17 sites, its presence at sand-patch scale was positively correlated with sand-patch area, sand temperature, and medium-sized sand grains. Although the beetle is assumed to be a parasite on the solitary bee, Colletes cunicularius (Linnaeus) (Hymenoptera: Colletidae), presence of the bee was a very weak predictor for A. bimaculatus, while other sand-living Hymenoptera were a strong predictor. At site-level scale, the beetle was positively correlated with total amount of sandy habitat and presence of sand-living Hymenoptera. Our study suggests that management strategies for this species should not consider sandy habitats equally. Rather, management efforts should focus on maintaining sites with larger total sandy areas, creating larger sand patches with medium-grained sand and a high degree of sun exposure. We also highlight that biotic interactions between the beetle and sand-living Hymenoptera are still poorly understood but potentially important for successful A. bimaculatus management.
Linear landscape elements are generally considered beneficial for promoting the movements of species between isolated habitats. However, relatively little consideration has been given to the effect of interconnections (nodes) between these elements: e.g. a simple linear element offers limited options for movement, whereas a network of such structures provides an exponential increase in potential pathways. In this pilot study we compared two experimental landscapes (single versus a lattice of four intercon- nected linear elements) in terms of their effect on the movement of males of Roesel’s bush-cricket (Metrioptera roeseli) (Orthoptera: Tettigoniidae). Emigration of released bush-crickets from experimental landscapes was greater if there was a single rather than a lat- tice of linear elements (corridors). In the landscape with a lattice of corridors, 50% of the bush-crickets changed their direction of movement at nodes at least once. There was also evidence that nodes were attractive to bush-crickets; a higher proportion of indi- viduals were found in and around nodes than in adjoining corridors, with the strength of this effect (i.e. aggregation at nodes) increasing with time. Thus nodes may not only affect the direction of movement but may also act as a local attractant. These effects may have an important role in the movement of species and their success in colonizing fragmented landscapes. These results indicate that in future landscape planning more consideration should be given to the connectivity between linear landscape elements as it is likely to be important in determining the movement and distribution of species.
Citation: Preuss S, Cassel-Lundhagen A, Berggren Å (2011) Modelling the distribution of the invasive Roesel's bush-cricket (Metrioptera roeselii) in a fragmented landscape. NeoBiota 11: 33–49. Abstract The development of conservation strategies to mitigate the impact of invasive species requires knowledge of the species ecology and distribution. This is, however, often lacking as collecting biological data may be both time-consuming and resource intensive. Species distribution models can offer a solution to this dilemma by analysing the species-environment relationship with help of Geographic information systems (GIS). In this study, we model the distribution of the non-native bush-cricket Metrioptera roeselii in the agricultural landscape in mid-Sweden where the species has been rapidly expanding in its range since the 1990s. We extract ecologically relevant landscape variables from Swedish CORINE land-cover maps and use species presence-absence data from large-scale surveys to construct a species distribution model (SDM). The aim of the study is to increase the knowledge of the species range expansion pattern by ex-amining how its distribution is affected by landscape composition and structure, and to evaluate SDM performance at two different spatial scales. We found that models including data on a scale of 1 × 1 km were able to explain more of the variation in species distribution than those on the local scale (10 m buffer on each side of surveyed road). The amount of grassland in the landscape, estimated from the area of ar-able land, pasture and rural settlements, was a good predictor of the presence of the species on both scales. The measurements of landscape structure – linear elements and fragmentation -gave ambivalent results which differed from previous small scaled studies on species dispersal behaviour and occupancy patterns. The models had good predictive ability and showed that areas dominated by agricultural fields and their associated grassland edges have a high probability being colonised by the species. Our study identified important landscape variables that explain the distribution of M. roeselii in Mid-Sweden that may also be important to other range expanding orthopteran species. This work will serve as a foundation for future analyses of species spread and ecological processes during range expansion. Copyright Sonja Preuss et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
1.Adams and Zhang recently published one of the best studies so far of patterns of insect folivory along a latitudinal (climatic) gradient. They show clear negative trends in foliage loss in relation to temperature for certain groups of insect herbivores. 2.Although their suggestion that the plant–herbivore interaction may be more important in cooler climates could be valid, they did not bring up the complementary explanation that interactions between predators and herbivores could also vary with climate. There are indications that insect natural enemies may respond more positively than insect herbivores to an increase in temperature. We argue that higher predator pressure in warmer climates may partly explain the patterns observed by Adams and Zhang. 3.Synthesis.To further develop the important research concerning herbivory in a changing climate, both theoretically and empirically, plant ecologists and entomologists would mutually benefit from joining forces.
Variation in morphological traits along latitudinal gradients often manifests as size clines. In insects, both positive and negative correlations are seen, and the mechanism behind the response is unclear. We studied variation in seven morphological traits of Roesel’s bush cricket, Metrioptera roeselii, sampled from seven latitude-matched-pair populations that were either geographically isolated from or connected to the species continuous distribution range. The aim was to examine whether morphological traits differed between isolated and continuous populations, and whether latitudinal variation was apparent. The data were used to indicate whether variation in trait means originates from plastic responses to the environment or genetic adaptation to local conditions. To evaluate the influence of gene flow on trait means, we analysed the genetic variation in seven microsatellites. Data showed that individuals from isolated populations display a positive relationship between latitude and body size, whereas individuals from continuous populations show little or no such relationship. The combined morphological and genetic data suggest that the isolated populations have adapted to local optima, while gene flow between continuous populations appears to counteract this process.
Abstract Despite the growing interest in how an individual's immune response is correlated to morphological and ecological factors, little empirical data has been available from wild insect populations. Many insects have different color morphs and exhibit differences in immune responses. Links are expected to exist between body colors and immune function in insects, because the same biochemical precursors involved in the immune response are responsible for melanin-based color markings. In this study, I assay the immune response of two different color morphs of 377 wild-caught bush-crickets, Metrioptera roeseli, from 20 populations by measuring individual encapsulation responses to a surgically implanted nylon monofilament. There was no difference between green and brown bush-cricket morphs (low melanin vs high melanin investment in cuticula color respectively) and their ability to mount an immune response to the implant. Further study is needed on the relationship between color morphology and immune response in wild insects, and whether trade-offs occur between factors during an insect's development phase and long-term health.
This article documents the addition of 411 microsatellite marker loci and 15 pairs of Single Nucleotide Polymorphism (SNP) sequencing primers to the Molecular Ecology Resources Database. Loci were developed for the following species: Acanthopagrus schlegeli, Anopheles lesteri, Aspergillus clavatus, Aspergillus flavus, Aspergillus fumigatus, Aspergillus oryzae, Aspergillus terreus, Branchiostoma japonicum, Branchiostoma belcheri, Colias behrii, Coryphopterus personatus, Cynogolssus semilaevis, Cynoglossus semilaevis, Dendrobium officinale, Dendrobium officinale, Dysoxylum malabaricum, Metrioptera roeselii, Myrmeciza exsul, Ochotona thibetana, Neosartorya fischeri, Nothofagus pumilio, Onychodactylus fischeri, Phoenicopterus roseus, Salvia officinalis L., Scylla paramamosain, Silene latifo, Sula sula, and Vulpes vulpes. These loci were cross-tested on the following species: Aspergillus giganteus, Colias pelidne, Colias interior, Colias meadii, Colias eurytheme, Coryphopterus lipernes, Coryphopterus glaucofrenum, Coryphopterus eidolon, Gnatholepis thompsoni, Elacatinus evelynae, Dendrobium loddigesii Dendrobium devonianum, Dysoxylum binectariferum, Nothofagus antarctica, Nothofagus dombeyii, Nothofagus nervosa, Nothofagus obliqua, Sula nebouxii, and Sula variegata. This article also documents the addition of 39 sequencing primer pairs and 15 allele specific primers or probes for Paralithodes camtschaticus.
Despite interest in the relationship between fluctuating asymmetry (FA), immune response and ecological factors in insects, little data are available from wild populations. In this study we measured FA and immune response in 370 wild-caught male bush-crickets, Metrioptera roeseli, from 20 experimentally introduced populations in southern-central Sweden. Individuals with more-symmetric wings had a higher immune response as measured by the cellular encapsulation of a surgically-implanted nylon monofilament. However, we found no relationship between measures of FA in other organs (i.e. tibia and maxillary palp) and immune response, suggesting that this pattern may reflect differing selection pressures.
- Aug 2009
Current predictions regarding the ecological consequences of climate change on animal populations are generally autecological and species-specific, and/or non-mechanistic extrapolations of recent short-term patterns. To better understand and predict the effects of climate change on the distribution of species and the abundance of populations we offer a novel, broad theoretical framework. Climate-induced changes in trophic structure may actually be more predictable than effects on individual species. The logic is that there are general differences in climatic sensitivity among trophic levels – specifically, that as one moves up trophic levels, there is an increase in the temperature sensitivity of vital rates. More precisely, we provide: (1) a formal mathematical definition of distribution limits that is both operational and conceptual, introducing the concept DL50, defined as the geographic and climatic isoline representing an equilibrium occupancy of half of the suitable habitats; (2) a matrix of the possible changes in trophic structure from climate change and the general theoretical consequences; and (3) a new idea that predicts broad effects of climatic warming on trophic systems. Our intention is to help meet the challenge of developing and testing general theoretical models that can predict which species will be winners and losers in ecological time, which evolutionary traits will be favoured or selected against, and what will be consequences for ecosystem structure and function.
Despite the growing interest in relationships between ecological variables and individual immune function, few empirical data have been available from wild populations. In this study, I assayed the immune response from 370 wild-caught bush-crickets, Metrioptera roeseli, from 20 experimentally introduced populations, by measuring individual encapsulation responses to a surgically implanted nylon monofilament. Bush-crickets descended from populations introduced into larger habitat patches showed a greater immune response when compared to individuals from smaller habitat-area introductions. Also, there was a significant positive correlation between immune response and the amount of linear elements at the introduction site. However, there was a lack of effect of population variables (i.e., propagule size and rate of population growth) on immune response. These results suggest that large-scale environmental parameters, such as patch size and connectivity, can be important for an individual’s physiological health and its ability to defend against disease-causing agents. Such effects are likely to compound the negative impacts associated with isolation of sub-populations and habitat fragmentation.
Artificial nests are frequently used to assess factors affecting survival of natural bird nests. We tested the potential for artificial nests to be used in a novel application, the prediction of nest predation rates at potential reintroduction sites where exotic predators are being controlled. We collected artificial nest data from nine sites with different predator control regimes around the North Island of New Zealand, and compared the nest survival rates with those of North Island robin (Petroica longipes) nests at the same sites. Most of the robin populations had been reintroduced in the last 10 years, and were known to vary in nest survival and status (increasing/stable or declining). We derived estimates of robin nest survival for each site based on Stanley estimates of daily survival probabilities and the known incubation and brooding periods of robins. Estimates of artificial nest survival for each site were derived using the known fate model in MARK. We identified the imprints on the clay eggs in the artificial nests, and obtained different estimates of artificial nest survival based on imprints made by different potential predators. We then compared the value of these estimates for predicting natural nest survival, assuming a relationship of the form s = αp β , where s is natural nest survival and p is artificial nest survival. Artificial nest survival estimates based on imprints made by rats (Rattus spp.) and brushtail possums (Trichosurus vulpecula) were clearly the best predictors (based on AIC c), and explained 64% of the variation in robin nest survival among sites. Inclusion of bird imprints in the artificial nest survival estimates substantially reduced their predictive value. We suggest that artificial nests may provide a useful tool for predicting the suitability of potential reintroduction sites for New Zealand forest birds as long as imprints on clay eggs are correctly identified.
The extent of darkening of melanin‐based plumages in birds has previously been linked with increasing aggressive encounters between individuals. The North Island robin (Petroica longipes) is a territorial New Zealand endemic passerine that displays delayed plumage maturation (darkening of the plumage with age). Aggressive boundary interactions in the robin are relatively common during the breeding season, when territories are protected and juveniles are dispersing. This study tests the hypothesis of aggression‐mediated plumage darkening in a population of North Island robins by examining if males and older (darker) birds are either (1) involved in a higher number of aggressive interactions, or (2) are more often the aggressor than females and younger birds. When sex and age are accounted for, darker individuals will be either (3) involved in a higher number of interactions or (4) more often the aggressor in encounters with other individuals. Data were collected by scoring the plumage darkness of 32 individuals in the field, and observing (1) interaction behaviours, and (2) age and sex of the birds involved in each interaction. The results show no support for any aggression‐mediated plumage darkness in the robin; males and older birds were not involved in more aggressive interactions, and were not more often the aggressor; and neither the frequency of interactions or the number of aggressive interactions were correlated with a darker plumage. Other more complex mechanisms may explain delayed plumage darkness in the North Island robin.
Complex interactions between an individual's genotype and its environment determine characteristics such as body size. However, gene-environment interactions should not be seen as being restricted to individual ontogeny: the diversity of the local gene pool can be greatly influenced by habitat variables and population history (e.g., landscape connectivity and propagule size). In this paper I use a model species, the bushcricket Metrioptera roeseli, and data from long-term experimental population introductions to examine individual body size as an indicator of the constraints placed on the gene pool by ecological variables following colonization of new environments. These broad-scale population-environment interactions are useful in understanding species ecology, species invasions and in managing successful reintroductions in conservation biology.
We thank Armstrong et al. (2008) for raising specific concerns about habitat fragmentation research in their paper “Avoiding hasty conclusions about effects of habitat fragmentation,” as these concerns are important and deserve to be highlighted. As a forum for exploring these issues, Armstrong et al. chose to single out our paper (Wittern and Berggren 2007) and structure their criticisms around three points with general relevance to fragmentation research; we discuss these criticisms below as they relate to our study: (1.) The scale of the study system needs to be appropriate for the study species. (2.) Interpretation needs to account for possible confounds. (3.) Increasing connectivity may not always benefit poor dispersers.
Natal dispersal is an important component in bird population dynamics and can influence the persistence of local and metapopulations. We examined natal dispersal in the North Island robin (Petroica longipes), a sedentary bird species distributed in a fragmented forest habitat on Tiritiri Matangi Island, New Zealand. Earlier studies have shown that the only dispersal phase in this species takes place when juveniles leave their natal patch, and that juveniles who fail to find suitable habitat do not survive their first winter. These findings suggest that natal dispersal behavior in this species is important for population viability. We found that juveniles were highly affected by the fragmentation of the forest habitat, with patch occupancy being positively correlated with degree of connectivity of the landscape. Most juvenile movements (52.1%) were observed between patches that were separated by less than 20 m. Juvenile North Island robins were found in all forest habitat types, including young and open stands. This suggests that the juveniles are not dependent on old forest stands during their dispersal phase. Based on these findings, we suggest that management of this regionally-threatened species should focus not only on maintaining populations in occupied patches and increasing the habitat quality of these patches, but also on protecting existing forest patches acting as corridors and creating new forest habitat among patches. This would greatly increase the viability of the species' metapopulations by increasing dispersal success between both unoccupied patches and subpopulations. Additionally, increased connectivity between forest patches could also be expected to increase the probability of successful dispersal of other threatened native species, many of which are also sensitive to the high degree of fragmentation of their habitats.
Natal dispersal is an important component in bird population dynamics and can influence the persistence of local and metapopulations. We examined natal dispersal in the North Island robin ( Petroica longipes), a sedentary bird species distributed in a fragmented forest habitat on Tiritiri Matangi Island, New Zealand. Earlier studies have shown that the only dispersal phase in this species takes place when juveniles leave their natal patch, and that juveniles who fail to find suitable habitat do not survive their first winter. These findings suggest that natal dispersal behavior in this species is important for population viability. We found that juveniles were highly affected by the fragmentation of the forest habitat, with patch occupancy being positively correlated with degree of connectivity of the landscape. Most juvenile movements (52.1%) were observed between patches that were separated by less than 20 m. Juvenile North Island robins were found in all forest habitat types, including young and open stands. This suggests that the juveniles are not dependent on old forest stands during their dispersal phase. Based on these findings, we suggest that management of this regionally-threatened species should focus not only on maintaining populations in occupied patches and increasing the habitat quality of these patches, but also on protecting existing forest patches acting as corridors and creating new forest habitat among patches. This would greatly increase the viability of the species' metapopulations by increasing dispersal success between both unoccupied patches and subpopulations. Additionally, increased connectivity between forest patches could also be expected to increase the probability of successful dispersal of other threatened native species, many of which are also sensitive to the high degree of fragmentation of their habitats.
Behavioural laterality, where an individual shows a preference for using its left or right side when engaging in a task, has been documented in a wide range of species. Typically, such preferences have been correlated with neurological biases associated with brain structure, genetics, sex, and age. In birds, behavioural laterality (and footedness) is most commonly expressed in the searching and handling of food. I examined foot preferences during foraging in the North Island robin (Petroica longipes), a species which rapidly vibrates one of its legs when searching for food on the forest floor. Topography of the study site had a significant effect on the laterality of the individual, with the uppermost leg almost exclusively used for the trembling behaviour. With this exception, there was no bias in which leg was used across the population or within the individual for different sexes or age classes. As study sites and their features are seldom described in laterality studies, the results of my study show that topographical features may be important factors in determining side preferences and need to be accounted for.
Intraspecific foster feeding and adoption has rarely been observed in birds, with the exception of waterfowl. In this study, I document for the first time the existence of intraspecific foster feeding and adoption of fledglings by adult passerines with their own young. During a three-year study of the North Island robin (Petroica longipes), a species with very low levels of extra-pair paternity, eight fledglings (4% of the fledglings in the population the study years) were fed by adults other than their parents, with four of these being adopted. In cases of foster feeding and adoption in this species: 1) adopted fledglings came from parents with lower feeding rates than the population average; 2) the territories of adopting/foster parents were of higher quality than the fledglings original parents' territories; 3) in all cases the adopting/foster-feeding parent was a male; 4) adoption of a fledgling was associated with a very low survival of the foster parent's own fledglings; 5) the original parents of the adopted fledglings had a higher reproductive output than the general population. Although the frequency of adoption/foster-feeding was very low, the findings suggest that both the original parents and the fledglings may have a fitness payoff from this behaviour with the fledgling most likely being the active participant. Foster parents appear to be victims of this phenomenon, with it reducing their life-time reproductive output. This begs the question of why selection does not act to improve recognition of one's own young. One possibility is that males are trapped in a situation where better discrimination of offspring is more costly than any benefits it may bring. To better understand the complex phenomenon and possible adaptive explanations for adoption, the perspective of all participants, juveniles, original parents and the foster parents, need to be considered.
The North Island Robin (Petroica longipes) is an endemic New Zealand passerine with melanin-based plumage of grey-brown and black, with males typically described as having darker plumage than females. In this study we quantified the relationship of sex and age on plumage colour in 32 North Island Robins on Tiritiri Matangi Island, New Zealand. We objectively scored plumage colour in each individual relative to a colour identity chart created with reference to HTML code. Our results support the general assertion that males are darker than females in this species. However, we found that this is significantly confounded by the age of the bird in both sexes and that this relationship is not a simple dichotomy between first-year breeders and adults. This is the first study to document the existence of delayed plumage maturation in the female of this species, and that plumage changes occur over many years in both sexes. The plumage of most Robins lies within the colour-range overlap between the sexes, indicating that plumage colour is not a reliable criterion for sexing this species. We used a classification and regression tree (CART) analysis to determine which morphometric measures were the best classifiers of gender in birds within the colour-range overlap; a tarsus measure cut-off of similar to 36 mm accurately predicted gender in > 80% of cases. We propose that delayed plumage maturation in this species results from social and physiological factors during moult, which affect melanin production and the colouring of the feathers.
A 3-year-old female North Island robin (Petroica longipes) was found dead on Tiritiri Matangi Island during the breeding season. The bird was in poor condition, and there was a 13 x 8 mm granulomatous mass in the thoracic cavity causing displacement of the heart and left lung. Histologically, the mass was a large granuloma infiltrated with fungal hyphae, and the liver contained multifocal aggregates of inflammatory cells. Thoracic aspergillosis and multifocal hepatitis. Determining the causes of death in populations of wild birds is often hampered by a lack of recovery of carcasses, autolysis and poor clinical history. In this case, the life history of the bird was known and recovery of the body was relatively swift. This is the first published description of aspergillosis in a free-living North Island robin.
Conservation efforts involving introductions, reintroductions, and translocations of populations have an inherent and inescapable problem of small initial populations. Small founding populations are likely to have a small proportion of the genetic variability carried by the original population. This may manifest phenotypically through changes in individual morphology, such as decreased body size, increased degree of fluctuating asymmetry, or changing susceptibility to environmental stressors. I investigated the effects of population and landscape variables on the morphology and fluctuating asymmetry in individual bush-crickets by examining 584 individual Roesel's bush-crickets (Metrioptera roeseli) from 29 established populations from different propagule sizes that were introduced in areas previously unoccupied by the species. The introduction sites were in landscapes similar to where the species occurs naturally, but sites differed in connectivity and amount of surrounding suitable habitat. Individuals were caught up to 9 years after the initial introduction, and five different morphological traits were measured. All introduced individuals originated from the same population and individuals from this source population were also collected for comparison in the analyses. Male body weight and female body length were positively affected by initial population size and degree of connectivity of the introduction patch. Isolation also affected fluctuating asymmetry in male tibias, with a higher degree of asymmetry in males that came from more isolated populations. In a relatively short time period, I was able to detect the effect of isolation and small population sizes on morphology and asymmetry. Small propagule sizes and habitat isolation are both likely to have resulted in decreased genetic diversity, the latter by reducing population sizes through decreased survival. These results show the importance of both large propagule sizes and good connectivity of habitats when introducing populations. The differences between the sexes in response to the variables examined also indicate that studies on morphology and fluctuating asymmetry need to consider males and females separately to avoid inaccurate generalizations of the state of the population.Resumen: Los esfuerzos de introducción que implican introducciones, reintroducciones y translocaciones de poblaciones tienen un problema inherente e inevitable de poblaciones iniciales pequeñas. Es probable que las poblaciones iniciales pequeñas tengan una pequeña proporción de la variabilidad genética de la población original. Esto puede manifestarse fenotípicamente por medio de cambios en la morfología individual, como una menor talla corporal, un aumento en la asimetría fluctuante o cambio en la susceptibilidad a factores ambientales estresantes. Examiné los efectos de variables poblacionales y del paisaje sobre la morfología y asimetría fluctuante en 584 individuos de Metrioptera roeseli de 29 poblaciones establecidas a partir de propágulos de tamaños diferentes que fueron introducidos en áreas no ocupadas por la especie previamente. Los sitios de introducción estaban en paisajes similares a donde la especie ocurre naturalmente, pero los sitios diferían en la conectividad y cantidad de hábitat adecuado circundante. Los individuos fueron capturados hasta 9 años después de las introducciones iniciales, y se midieron cinco características morfológicas diferentes. Todos los individuos introducidos provenían de la misma población y también fueron recolectados individuos de esta población fuente para comparación en los análisis. El peso de machos y la longitud corporal de hembras fueron afectados positivamente por el tamaño poblacional inicial y el grado de conectividad del parche donde fueron introducidos. El asilamiento también afectó a la asimetría fluctuante en las tibias de machos, con un mayor grado de asimetría en machos provenientes de poblaciones más aisladas. En un período de tiempo relativamente corto, pude detectar el efecto del aislamiento y de tamaños poblacionales pequeños sobre la morfología y la asimetría. Es probable que tanto el tamaño pequeño de propágulos como el asilamiento del hábitat resultaran en una menor diversidad genética, por la disminución de los tamaños poblacionales por reducción de la supervivencia en el caso del aislamiento. Estos resultados muestran la importancia tanto del tamaño grande de propágulos como de la adecuada conectividad de hábitats cuando se introducen poblaciones. Las diferencias entre sexos como respuesta a las variables examinadas también indican que los estudios de morfología y simetría fluctuante necesitan considerar a machos y hembras por separado para evitar generalizaciones imprecisas sobre el estado de las poblaciones.
Cloacal protuberances (CP) in male birds result from spermatic engorgement of storage tubules around the cloaca during the breeding season. We examined seasonal changes in the volume and orientation of the CP in the New Zealand stitchbird Notiomystis cincta. The male stitchbird has one of the largest recorded CPs for any species (max = 1,570mm3), with CP volume increasing by almost 400% between the non-breeding and breeding seasons. While sperm competition has been positively correlated with the magnitude of CP storage in other species, no evidence previously existed for the CP improving copulation efficiency. By measuring the relative orientation of the CP throughout the year, we show that not only does the CP increase in size as males become sexually active, it also changes its orientation by approximately 60. This results in it shifting from facing posteriorly to becoming almost perpendicular to the abdomen. This cloacal erection improves the apposition of the male and female cloacal openings during face-to-face forced copulation in this species. This provides the first reported evidence supporting the copulation efficiency hypothesis of the avian CP. While the magnitude of seasonal changes in female cloacal volume was similar to males, female cloacal orientation remained virtually unchanged across seasons. This difference between the sexes is likely to reflect differing selection pressures for optimizing sperm transfer. In females, a posterior-facing cloaca is ideal for both waste evacuation and sperm reception, whereas, for the male, a posterior-facing cloaca is well suited for waste evacuation, but possibly hinders sperm delivery. Changes in male cloacal orientation from the non-breeding to the breeding season are a likely reflection of conflict in this dual function. Evidence of changes in CP orientation in another passerine species suggests this phenomenon is widespread and also important for understanding related fields such as sperm competition, forced copulation and constraints on the evolution of the avian intromittent organ.
Birds are hosts to many blood-sucking ectoparasites, with these parasites having diverse and wide-ranging effects on the health, reproductive success and behaviour of their hosts. Louse flies Ornithoica sp. (Rondani) (Diptera: Hippoboscidae) are common parasites on bird species around the world and have been found to be vectors for both blood parasites and skin parasites. The North Island robin (Petroica australis longipes) is an endemic New Zealand passerine focus of numeric management projects. 32 adults of and fifty-six robin fledglings were caught and examined for louse flies. There was a significant effect of micro-climate on the presence of louse flies, with parasites more likely to be present on juveniles in wetter territories. The effect of micro-climate was not seen in adults. The effects of parasites are important to quantify for management decisions regarding treatment, or lack thereof, of parasites in native species.
Pathological consequences of the blood-sucking mite Ornithonyssus bursa vary between species, with its impact ranging from no measurable effect, to significant blood loss and chick mortality. In New Zealand, where several bird species are known to be parasitised by O.bursa, the effect of this mite on host fitness is unclear, as few studies have been carried out. During a three-year study of the North Island robin Petroica longipes on Tiritiri Matangi Island, the prevalence of O. bursa in robin nests and on chicks and its impact on robin chick growth and survival was measured. The presence of mites was correlated with both time of the season and humidity of the habitat, with infestation being positively correlated with later nesting attempts and more humid microclimates. Robin chicks in infested nests were significantly smaller and fledged at an earlier age than chicks in nests where no mites were detected. Despite this effect, no significant difference in body size or survival was detected between the two groups at one month post-fledging. This was most likely because chicks from mite-infested nests compensated for their retarded growth once they left the nest environment. On mainland New Zealand, where ground-dwelling mammalian predators are present, chicks forced to leave the nest at an earlier age with less developed flying skills may be at an increased risk of predation.
Background The colour of animals' skin, fur, feathers or cuticula has been estimated in a large number of studies. The methods used to do so are diverse, with some being costly and not available to all researchers. In a study to measure plumage colour in a bird species, a new method of creating a colour chart was developed. While colour-charts have their own limitations, these can be minimised when they have the following properties: 1) being readily available to the majority of biologists, 2) containing a large array of colours to allow accurate recording and differentiation of subtle colour differences, 3) low cost, 4) adhering to a world-wide standard, and 5) being available in both hard-copy and digital formats to allow for various analytical methods. The method described below satisfies all of these requirements. Results Colour charts estimated to fit the range of the species' plumage colours were created on the computer screen using web software that allowed for HTML-coding (in this case Dreamweaver™). The charts were adjusted using feathers from dead specimens until a satisfying range of darker and lighter colours were found. The resulting chart was printed out and was successfully used in the field to determine the plumage colour of hand-held birds. Conclusion Access to a computer and printer, and the software to enable the creation of a chart, is within the reach of the vast majority of biologists. The numbers of colours that can be generated should suit most studies, with the advantage of the method being that the chart can be individually tailored to the species under study. HTML colour coding is a worldwide standard, thus the colours used in studies can be described in the methods section of journal articles using the six-digit alphanumeric code. We believe this method is very useful as a low-tech method for future estimation of individual colour.
Many bird species show delayed plumage maturation (DPM), retaining sub-adult plumage until after their first breeding season. Most explanations assume that DPM increases fitness over the breeding season. However, unless birds undergo a full moult before breeding, DPM could also be an adaptation to increase survival over the previous winter. The winter adaptation hypothesis has never been tested owing to the difficulty of measuring overwinter survival. We experimentally tested this hypothesis in North Island robins (Petroica longipes) using a closed island population where we could accurately estimate survival. The experiment involved dyeing 41 juveniles to mimic adult males, and comparing their survival with 41 control juveniles treated with the same peroxide base minus the pigment. The population was monitored with a series of resighting surveys, and mark-recapture analysis used to estimate overwinter survival. Survival probability was estimated to be 10% for dyed birds versus 61% for control birds in 2001, and 29% for dyed birds versus 40% for control birds in the winter of 2002, supporting the winter adaptation hypothesis for DPM. Access to suitable habitat is the key factor limiting juvenile survival in this population, and the locations where dyed juveniles were sighted suggest that they were often excluded from suitable areas.
One aid to understanding species distribution patterns is to gather detailed information on individual movement behavior. To gather information on dispersal capabilities in Roesel''s bush-cricket Metrioptera roeseli an individual-based study was carried out. In four areas with two different cattle grazing regimes 35 individuals were released and their movements recorded for a mean of 80 h. Bush-crickets in grazed areas moved significantly further between the censuses and more individuals in grazed areas moved >5 m from the release point. The further away an individual was from the release point, the more likely he was to continue moving away. There was also a positive correlation between distance from the release point and the step length of the individual. The movement pattern found may make it easier for the species to find and reach new favorable habitats and withstand the negative effects of fragmentation.
Although plastic and metallic leg bands are widely used for identifying individual birds to assist population monitoring, the health risks associated with banding are quantified relatively rarely. We recorded the general occurrence of foot and leg injuries during a four-year study of the North Island robin (Petroica longipes) and assessed the probability of banding-injury relationships. While most leg problems were not obviously related to banding (transient lameness, congenital deformity, infection, fracture), on 10 occasions individuals experienced lameness or injury directly because of the presence of bands (∼2.5% of individuals per year). In eight of these instances, individual robins caught their back toe (hallux) in between a band and their tarsus. This resulted in an inability to place the affected foot on the ground, and in some cases a pedal injury. We believe that this previously undescribed toe entrapment is made possible because of the robin's sideways perching behaviour on upright vegetation. This highlights that relationships between leg banding and injury may be species-specific and that the impacts of banding should be identified and quantified in all species in which it is used. This will allow more accurate assessments of the risks and benefits associated with this common marking technique.
One method proposed for moderating the negative effects of habitat isolation is the preservation or restoration of linear landscape elements that structurally link isolated habitat remnants. An understanding of how animals react to landscape elements and move through the landscape is vital for species management and theory development. To achieve this understanding, detailed information on movement rates and specific movement behavior of individual animals in different ecosystems is essential. In an experimental study, we investigated whether individuals of Roesel's bush-cricket ( Metrioptera roeseli) prefer to use corridors or move over the matrix when they leave a habitat patch. We examined whether movement rates and movement angles in corridors and matrix differed and whether individuals showed edge-avoidance behavior. Differences in these behaviors were analyzed in relation to the softness of habitat edges. We found that approximately 30% more individuals used the corridor than would be expected if dispersal behavior was random. All individuals using the corridor as a dispersal route moved to the end of the corridor and into the surrounding habitat, which is 1000% more than would be expected if dispersal was random. The edge type ( hard or soft) did not influence whether individuals moved through corridors or the matrix. Individuals that moved through the corridor moved straighter but slower than individuals that moved over the matrix. A higher movement rate over the matrix than through corridors may be explained by an increased risk of predation, starvation, or dehydration in the open habitat causing individuals to move more quickly toward the higher vegetation. Our results suggest that individuals avoid the edge and the matrix and that the corridor is a preferred alternative for dispersal. We conclude that for this species, and probably other similar species of Orthoptera, linear elements in the form of corridors have a positive influence on the individual's dispersal through the landscape. This demonstrates the value of corridors in reducing the negative effect of habitat fragmentation on the persistence of local species. Resumen: Un método propuesto para moderar los efectos negativos del aislamiento del hábitat es la preservación o restauración de los elementos del paisaje lineal que estructuralmente unen remanentes de hábitats aislados. El conocimiento de la forma en que los animales reaccionan a los elementos de paisaje y se mueven a través del paisaje es vital para el manejo de especies y la teoría del desarrollo. Para alcanzar este conocimiento, es esencial conocer información detallada sobre las tasas de movimientos y las conductas específicas de movimiento de animales individuales en diferentes ecosistemas. En un estudio experimental, investigamos si los individuos del grillo de arbusto de Roesel ( Metrioptera roeseli), prefieren usar corredores o moverse sobre la matriz cuando dejan un parche del hábitat. Examinamos si las tasas y los ángulos de movimiento en corredores y matrices difieren y si los individuos mostraban una conducta para evitar los bordes. Las diferencias en estas conductas fueron analizadas en relación a la suavidad de los bordes del hábitat. Encontramos que un 30% más de los individuos esperados usaron el corredor si la conducta de dispersión era aleatoria. Todos los individuos que usaron el corredor como una ruta de dispersión se movieron hacia el final del corredor y hacia adentro del hábitat circundante, lo cual es 1000% más de lo que se había esperado si la dispersión hubiera sido aleatoria. El tipo de borde (suave o duro), no influenció en que los individuos se movieran a través de los corredores o la matriz. Los individuos que se movieron a través del corredor se movieron de manera más recta pero más lenta que los individuos que se movieron sobre la matriz. Una tasa de movimiento mayor sobre la matriz comparada con corredores puede ser el resultado de un incremento en el riesgo de depredación, inanición o deshidratación en el hábitat abierto resultando en un movimiento más rápido de los individuos hacia vegetación más alta. Nuestros resultados sugieren que los individuos evitaron el borde y la matriz y el corredor es una alternativa preferida para la dispersión. Concluimos que para ésta especie y probablemente para otras especies similares de ortópteros, los elementos lineales en forma de corredores tienen una influencia positiva en la dispersión de individuos a lo largo del paisaje. Esto demuestra el valor de los corredores en la persistencia de especies locales al reducir los efectos negativos de la fragmentación del hábitat.
Summary1.Fragmentation and habitat loss affects both existing and introduced populations. Small habitat areas may have harsher biotic and abiotic conditions, as well as restricting population sizes. Loss of connectivity reduces the opportunities for individuals to move between patches to rescue populations or to re-colonize patches. Knowledge of how landscape composition affects the introduced populations is therefore essential for successful management and future re-introductions.2.To study the effect of landscape composition and structure on the success of colonization, population growth and dispersal distances, we introduced Roesel’s bush-crickets Metrioptera roeseli to 70 habitat islands in areas previously unoccupied by the species. The introduction sites differed in habitat area and connectivity. The population survival and dispersal were then studied for 5 years after initial introductions.3.In addition to results showing the importance of suitable habitat for population persistence, connectivity in form of linear landscape elements and nodes was also crucial. Linear landscape elements and/or nodes were important for colonization success, growth and dispersal. Linear landscape elements and nodes also reduced the negative effects of unsuitable habitat (matrix) and isolation from suitable habitat and on the populations.4.These results stress the importance of connectivity in the landscape for population survival and establishment. Consideration of this should be taken into account in both management and re-introductions of bush-crickets and other invertebrates with similar population characteristics and behaviour.
Assessing the colonizing ability of a species is important for predicting its future distribution or for planning the introduction or reintroduction of that species for conservation purposes. The best way to assess colonizing ability is by making experimental introductions of the species and monitoring the outcome. In this study, different-sized propagules of Roesel's bush-cricket, Metrioptera roeseli, were experimentally introduced into 70 habitat islands, previously uninhabited by the species, in farmland fields in southeastern Sweden. The areas of introduction were carefully monitored for 2-3 yr to determine whether the propagules had successfully colonized the patches. The study showed that large propagules resulted in larger local populations during the years following introduction. Probability of colonization for each propagule size was measured and showed that propagule size had a significant effect on colonization success, i.e., large propagules were more successful in colonizing new patches. If future introductions were to be made with this or a similar species, a propagule size of at least 32 individuals would be required to establish a viable population with a high degree of certainty.
Thesis (doctoral)--Swedish University of Agricultural Sciences, 2001. Consists chiefly of 4 papers submitted to or published in journals, 2 of which are co-authored with other writers. Includes bibliographical references.
The bush cricket, Metrioptera roeseli (Orthoptera, Tettigoniidae), occurs in patchy and heterogeneous agricultural landscapes. Such a mosaic of different types of grassland habitats causes spatial variation in local population density. Low population densities may result in fewer mating opportunities that can give rise to an Allee effect, possibly leading to a population decline or extinction. This experimental study shows that individuals can avoid an Allee effect by adjusting their movement behaviour in sparse populations. Even at a population density of Eve individuals per hectare, i.e. approximately one percent of normal population densities, no reduction of mating frequencies was detected. Observed net displacements made by different individuals in high and low population densities could successfully be predicted by a simple model of animal movement.