| 1. |
- Becher, Paul, et al.
(author)
-
Yeast, not fruit volatiles mediate Drosophila melanogaster attraction, oviposition and development
- 2012
-
In: Functional Ecology. - : Wiley. - 1365-2435 .- 0269-8463. ; 26:4, s. 822-828
-
Journal article (peer-reviewed)abstract
- 1.In nature, the fruit fly Drosophila melanogaster is attracted to fermenting fruit. Micro-organisms like Saccharomyces yeasts growing on fruit occupy a commonly overlooked trophic level between fruit and insects. Although the dietary quality of yeast is well established for D.melanogaster, the individual contribution of fruit and yeast on host finding and reproductive success has not been established. 2.Here, we show that baker's yeast Saccharomyces cerevisiae on its own is sufficient for fruit fly attraction, oviposition and larval development. In contrast, attraction and oviposition were significantly lower if non-fermented grape juice or growth media were used, and yeast-free grapes did not support larval development either. 3.Despite a strong preference for fermented substrates, moderate attraction to and oviposition on unfermented fruit might be adaptive in view of the fly's capacity to vector yeast. 4.Signals emitted by fruit were only of secondary importance because fermenting yeast without fruit induced the same fly behaviour as yeast fermenting on fruit. We identified a synthetic mimic of yeast odour, comprising ethanol, acetic acid, acetoin, 2-phenyl ethanol and 3-methyl-1-butanol, which was as attractive for the fly as fermenting grape juice or fermenting yeast minimal medium. 5.Yeast odours represent the critical signal to establish the flyfruityeast relationship. The traditional plantherbivore niche concept needs to be updated, to accommodate for the role of micro-organisms in insectplant interactions.
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| 2. |
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| 3. |
- Elmberg, Johan, et al.
(author)
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Climate change-induced shifts in survival and size of the worlds' northernmost oviparous snake : A 68-year study
- 2024
-
In: PLoS ONE. - : Public Library of Science. - 1932-6203. ; 19:3
-
Journal article (peer-reviewed)abstract
- Because of their dependence on ambient temperature ectothermic animals can serve as sentinels of conservation problems related to global warming. Reptiles in temperate areas are especially well suited to study such effects, as their annual and daily activity patterns directly depend on ambient temperature. This study is based on annual data spanning 68 years from a fringe population of Grass Snakes (Natrix natrix), which is the world's northernmost oviparous (egg-laying) reptile, and known to be constrained by temperature for reproduction, morphology, and behavior. Mark-recapture analyses showed that survival probability was generally higher in males than in females, and that it increased with body length. Body condition (scaled mass index) and body length increased over time, indicative of a longer annual activity period. Monthly survival was generally higher during winter (i.e., hibernation) than over the summer season. Summer survival increased over time, whilst winter survival decreased, especially duringrecent decades. Winter survival was lower when annual maximum snow depth was less than 15 cm, implying a negative effect of milder winters with less insulating snow cover. Our study demonstrates long-term shifts in body length, body condition and seasonal survival associated with a warming climate. Although the seasonal changes in survival ran in opposite directions and though changes were small in absolute terms, the trends did not cancel out, but total annual survival decreased. We conclude that effects of a warming climate can be diverse and pose a threat for thermophilic species in temperate regions, and that future studies should consider survival change by season, preferably in a long-term approach.
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| 4. |
- Elmberg, Johan, et al.
(author)
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Movements and habitat choice of resident and translocated adult female Grass Snakes (Natrix natrix) during the egg-laying period
- 2019
-
In: Herpetological Journal. - : BRITISH HERPETOL SOC. - 0268-0130. ; 29:4, s. 244-250
-
Journal article (peer-reviewed)abstract
- We used externally applied transmitters to study movements of female grass snakes (Natrix natrix) during the egg-laying period in a near-urban landscape in Sweden. Half of the studied snakes were residents while the other half were translocated individuals with no previous experience of the area. As predicted, resident females moved more goal-oriented and shorter distances than did translocated individuals. Habitat use did not differ between resident and translocated snakes; they were typically found in bushes, reeds, and tall vegetation. Habitat preference (use in relation to availability) showed that bushy habitats, tall grassy vegetation and reedbeds were over-used in proportion to availability, whereas forest and open grass lawns were used less than expected based on availability. Our study highlights the importance of preserving and restoring linear habitat components providing shelter and connectivity in conservation of grass snakes. We suggest that externally applied transmitters are a better option than surgically implanted ones in movement studies of grass snakes, and that translocation as a conservation method for snakes has drawbacks.
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| 5. |
- Elmberg, Johan, 1960-, et al.
(author)
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Snokens barnkammare försvinner
- 2013
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In: Fauna och flora. - 0014-8903. ; 108:1, s. 10-16
-
Journal article (other academic/artistic)
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| 6. |
- Elmberg, Johan, et al.
(author)
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Snokens barnkammare försvinner
- 2013
-
In: Fauna och flora populär tidskrift för biologi. - 0014-8903. ; 108:1, s. 10-16
-
Journal article (other academic/artistic)
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| 7. |
- Forsman, Anders, et al.
(author)
-
Association of coloration mode with population declines and endangerment in Australian frogs
- 2009
-
In: Conservation Biology. - : Wiley. - 0888-8892 .- 1523-1739. ; 23:6, s. 1535-1543
-
Journal article (peer-reviewed)abstract
- Successful protection of biodiversity requires increased understanding of the ecological characteristics that predispose some species to endangerment. Theory posits that species with polymorphic or variable coloration should have larger distributions, use more diverse resources, and be less vulnerable to population declines and extinctions, compared with taxa that do not vary in color. We used information from literature on 194 species of Australian frogs to search for associations of coloration mode with ecological variables. In general, species with variable or polymorphic color patterns had larger ranges, used more habitats, were less prone to have a negative population trend, and were estimated as less vulnerable to extinction compared with nonvariable species. An association of variable coloration with lower endangerment was also evident when we controlled statistically for the effects of range size. Nonvariable coloration was not a strong predictor of endangerment, and information on several characteristics is needed to reliably identify and protect species that are prone to decline and may become threatened by extinction in the near future. Analyses based on phylogenetic-independent contrasts did not support the hypothesis that evolutionary transitions between nonvariable and variable or polymorphic coloration have been accompanied by changes in the ecological variables we examined. Irrefutable demonstration of a role of color pattern variation in amphibian decline and in the dynamics and persistence of populations in general will require a manipulative experimental approach.
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| 8. |
- Forsman, Anders, et al.
(author)
-
Calling is an honest indicator of paternal genetic quality in male poison frogs
- 2006
-
In: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 60:10, s. 2148-2157
-
Journal article (peer-reviewed)abstract
- Several competing hypotheses have been put forward to explain why females of many species mate preferentially with males possessing the most conspicuous signals (e.g., ornaments, displays, or songs). We performed a laboratory experiment using two species of poison frogs, Dendrobates leucomelas and Epipedobates tricolor, to test the hypothesis that male calling performance is an honest indicator of parental quality. Our analyses are based on data from behavioral observations of mating activities of captive-reared individuals (and their offspring) that were housed in terraria for four consecutive breeding seasons. Male mating success increased with male calling rate and chirp duration in both species, suggesting that females preferred males with more elaborate calls. Because calling performance improved with age in D. leucomelas, female poison frogs that prefer males with more elaborate calls in the wild may end up mating with older males that have already proven their ability to survive. Females that mated with good callers obtained higher quality offspring. Eggs fertilized by males with high calling rates and long chirp durations had higher hatching success and produced tadpoles that were more likely to metamorphose into surviving frogs. As a consequence, females that mated with males with high calling performance obtained more surviving offspring per egg, compared to females that mated with poor callers. Collectively, our findings comply with the notion that female poison frogs prefer to mate with good callers because calling performance is a reliable predictor of offspring quality. The possible influence of maternal allocation and reasons for the strong effect size compared to previous studies are discussed.
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| 9. |
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| 10. |
- Hagman, Helga, et al.
(author)
-
Protein array profiling of circulating angiogenesis-related factors during bevacizumab containing treatment in metastatic colorectal cancer
- 2018
-
In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 13:12
-
Journal article (peer-reviewed)abstract
- Background Prolonged angiogenesis inhibition may improve treatment outcome in metastatic colorectal cancer (mCRC) patients. However, due to the complexity of the angiogenic pathways there is a lack of valid predictive biomarkers for anti-angiogenic agents. Here, we describe and optimize a procedure for simultaneous dynamic profiling of multiple angiogenesis related proteins in patient serum to explore associations with the response and acquired resistance to anti-angiogenic therapy. Materials and methods Patients (n=22) were selected from a clinical trial investigating maintenance treatment with bevacizumab alone after response to induction chemotherapy + bevacizumab in mCRC. Serum samples were analysed for 55 unique angiogenesis related proteins using a commercial proteome profiler array and a publicly available image analysis program for quantification. Samples were collected at baseline before induction treatment start, at start of maintenance treatment, and at end of treatment after tumour progression. Main results and conclusion For eight proteins, the antibody array signals were below detection range in all patient samples. None of the proteins showed levels at baseline or at start of maintenance with strong evidence for correlation to time to progression (lowest nominal p-value 0.03). The dynamic ranges of protein levels measured during the induction treatment period and during the maintenance period were analysed separately for time trends. Evidence for changing trends (up/down) in the levels of MMP-8, TIMP-4 and EGF was observed both during response to induction treatment and at progressive disease, respectively. For three of the proteins (IL-8, Activin A and IGFBP-2), weak evidence for correlation between increasing protein levels during induction with chemotherapy and bevacizumab and time to progression was observed. In conclusion, semi-quantitative profiling of angiogenesis related proteins in patient serum may be a versatile tool to screen for protein patterns aiming at identifying resistance mechanisms of anti-angiogenic treatment in patients with mCRC.
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| 11. |
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| 12. |
- Hagman, Mattias, et al.
(author)
-
Alarm cues experienced by cane toad tadpoles affect post-metamorphic morphology and chemical defences
- 2009
-
In: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 23, s. 126-132
-
Journal article (peer-reviewed)abstract
- Summary: In many anuran species, larvae modify their developmental trajectories and behaviour in response to chemical cues that predict predator risk. Recent reviews highlight a dearth of studies on delayed (post-metamorphic) consequences of larval experience. 2 We raised cane toad (Bufo marinus) tadpoles either under control conditions or in the presence of non-lethal predator cues (crushed conspecifics). 3 Exposure to these chemical cues massively reduced size at metamorphosis, as predicted by theory. Parotoid glands were larger relative to body size in post-metamorphic animals from the experimental treatment, suggesting higher investment in chemical defences. 4 Exposure to chemical cues from crushed conspecifics during larval life reduced total bufadienolide content of metamorphs, but increased amounts of one specific bufadienolide (bufalin). 5 Hence, cane toads respond to perceived predation risk in the aquatic environment by metamorphosing at a smaller size and modifying their investment in defensive toxins during post-metamorphic life. 6 Phenotypically flexible responses to larval conditions vary among amphibian taxa, and can involve significant carry-over effects into post-metamorphic life.
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| 13. |
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| 14. |
- Hagman, Mattias, et al.
(author)
-
Australian tadpoles do not avoid chemical cues from invasive cane toads (Bufo marinus)
- 2008
-
In: Wildlife research (East Melbourne). - 1035-3712 .- 1448-5494. ; 35:4, s. 59-64
-
Journal article (peer-reviewed)abstract
- In previous work, we have shown that tadpoles of invasive cane toads (Bufo marinus) strongly avoid scent cues from crushed conspecific tadpoles. Thus, identifying the identity of the chemical involved may provide novel approaches to toad control, by manipulating the behaviour of toad tadpoles. A first step in the search for that chemical is to see whether toad tadpoles are similarly repelled by chemical cues from crushed tadpoles of other species. Our experimental trials with four native Australian frogs (three hylids, one myobatrachid) show that toads do not respond to chemical cues from these taxa. Hence, the specific chemicals that induce avoidance cannot be generic ones (e.g. body fluids, tissue fragments) but instead, must reflect some underlying chemical divergence in body composition between the tadpoles of cane toads versus the other anurans that we have tested.
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| 15. |
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| 16. |
- Hagman, Mattias
(author)
-
Control methods for unwanted anurans
- 2011
-
Book (peer-reviewed)abstract
- Anurans (frogs and toads) worldwide are threatened by habitat loss, emerging infectious diseases, overexploitation, pollution, climatic change and introduction of exotic species. As a result of human activities, some anurans have actually increased their distribution and are now doing extremely well in places far outside of their natural range. But these anurans are often unwanted in the introduced range because they may disturb recipient ecosystems and pose a threat to indigenous fauna, including native amphibians. This book reviews anuran biology and discusses some life history traits that may be suitable for targeted control measures.
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| 17. |
- Hagman, Mattias, et al.
(author)
-
Correlated evolution of conspicuous colouration and body size in the poison frog family Dendrobatidae
- 2003
-
In: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 57:12, s. 2904-2910
-
Journal article (peer-reviewed)abstract
- Conspicuous coloration is often used in combination with chemical defenses to deter predators from attacking. Experimental studies have shown that the avoidance inducing effect of conspicuous prey coloration increases with increasing size of pattern elements and with increasing body size. Here we use a comparative approach to test the prediction from these findings, namely that conspicuous coloration will evolve in tandem with body size. In our analysis, we use a previously published mitochondrial DNA-based phylogeny and comparative analysis of independent contrasts to examine if evolutionary shifts in color pattern have been associated with evolutionary changes in body size in aposematic poison frogs (Anura: Dendrobatidae). Information on body size (snout to vent length) and coloration were obtained from the literature. Two different measures of conspicuousness were used, one based on rankings by human observers and the other based on computer analysis of digitized photographs. The results from comparative analyses using either measure of coloration indicated that avoidance inducing coloration and body size have evolved in concert in poison frogs. Results from reconstruction of character change further indicate that the correlated evolution of size and coloration has involved changes in both directions within each of the different clades of the phylogenetic tree. This finding is consistent with the hypothesis that selection imposed by visually guided predators has promoted the evolution of larger body size in species with conspicuous coloration, or enhanced evolution of conspicuous coloration in larger species.
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| 18. |
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| 19. |
- Hagman, Mattias, et al.
(author)
-
Deceptive digits : the functional significance of toe waving by cannibalistic cane toads (Bufo marinus)
- 2008
-
In: Animal Behaviour. - : Elsevier BV. - 0003-3472 .- 1095-8282. ; 75, s. 123-131
-
Journal article (peer-reviewed)abstract
- Many ambush foraging predators possess specialized structures and behaviours that plausibly function to attract prey, but this hypothesis has rarely been subject to direct empirical tests. If luring evolved to attract specific prey types then we predict that it will be manifested only if that prey type is present, and only by predators of the size class that feed on that prey type. Also, luring should induce closer approach by prey; and aspects of the behaviour (e. g. frequency of movement of the lure) should have been. ne tuned by selection to induce maximal response from prey. We describe a novel luring system: small- and medium-sized ( but not metamorph and large) cane toads, Chaunus marinus, wave the long middle toe of the hind-foot up and down in an obvious display. In keeping with the functional hypothesis, toe waving is elicited by moving edible-sized objects such as crickets or metamorphic toads. Metamorphic toads are attracted to this stimulus, and trials with a mechanical model show that both the colour and the vibrational frequency of the toe correspond closely with those most effective at attracting smaller conspecifics towards the lure. The independent evolution of visual luring systems in many animal lineages provides a powerful opportunity for robust empirical tests of adaptive hypotheses about signal design.
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| 20. |
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| 21. |
- Hagman, Mattias, et al.
(author)
-
Determinants of anti-predator tactics in hatchling grass snakes (Natrix natrix)
- 2015
-
In: Behavioural Processes. - : Elsevier BV. - 0376-6357 .- 1872-8308. ; 113, s. 60-65
-
Journal article (peer-reviewed)abstract
- Many organisms exhibit diverse anti-predator tactics, influenced by genetics and prior experience. In ectothermic taxa, offspring phenotypes are often sensitive to developmental temperatures. If the effectiveness of alternative anti-predator responses depends on thermally sensitive traits, then the temperatures experienced during embryonic life should also affect how offspring respond to an approaching predator. We incubated 16 clutches of Swedish grass snakes (Natrix natrix) at a range of developmental temperatures, and scored body size, colour pattern, locomotor performance and anti-predator responses of 213 hatchlings from those clutches. A hatchling snake’s size and locomotor abilities were affected by its clutch of origin, its developmental temperature, and by an interaction between these two factors. Anti-predator tactics were strongly linked to locomotor ability, such that slower snakes tended to rely upon aggressive displays rather than flight. Incubation temperatures that generated slow (and thus aggressive) snakes also modified the colour of the snake’s nuchal spot. Temperatures in the low to medium range generated mostly cream, white and orange spots, whereas medium to high temperatures generated more yellow spots. Incubation effects, and gene X environment interactions, thus may generate complex correlations between morphology, locomotor ability, and anti-predator tactics.
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| 22. |
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| 23. |
- Hagman, Mattias, et al.
(author)
-
Effects of invasive cane toads on Australian mosquitoes : does the dark cloud have a silver lining?
- 2007
-
In: Biological Invasions. - : Springer Science and Business Media LLC. - 1387-3547 .- 1573-1464. ; 9:4, s. 445-452
-
Journal article (peer-reviewed)abstract
- Research on the ecological impacts of invasive organisms typically looks only for negative impacts, ignoring the possibility that the wider community might see benefits in some of these effects. To truly understand the impact of invasive species, we need to look as broadly as possible, and incorporate studies on a diversity of variables. The spread of the South American cane toad (Bufo marinus) through tropical Australia is widely viewed as an ecological catastrophe, but anecdotal reports suggest that the invasion of toads may reduce the numbers of mosquitoes (and thus, potentially, the risk they pose to human health). We conducted experiments to determine whether the presence of toad tadpoles affects survival rates, adult body sizes and/or rates of oviposition of four species of disease-carrying mosquitoes. In the laboratory, the presence of toad tadpoles significantly reduced the sizes of adult mosquitoes at emergence, and also reduced survival rates of the larvae of one mosquito species. In field trials, mosquitoes were less likely to oviposit in waterbodies containing toad tadpoles. Accordingly, these data suggest (but do not prove) that toad invasion may reduce mosquito abundance. More generally, any overall evaluation of the impact of an invasive species needs to consider possible benefits (e.g. to human health) as well as negative effects (e.g. to native species). Both types of information are essential to inform community decisions about the management of feral taxa such as the cane toad in Australia.
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| 24. |
- Hagman, Mattias, et al.
(author)
-
Factors influencing responses to alarm pheromones by tadpoles of invasive cane toads (Bufo marinus)
- 2009
-
In: Journal of Chemical Ecology. - : Springer Science and Business Media LLC. - 0098-0331 .- 1573-1561. ; 35, s. 265-271
-
Journal article (peer-reviewed)abstract
- If pheromonal communication systems of invasive species differ from those of native biota, it may be possible to control the invader by exploiting that difference. When injured, the larvae of cane toads, Bufo marinus, an invasive species of major concern in tropical Australia, produce species-specific chemical cues that alert conspecific tadpoles to danger. Repeated exposure to the alarm chemical reduces tadpole survival rates and body sizes at metamorphosis and, thus, could help control toad populations. To evaluate the feasibility of this approach, we need to know how the intensity of toad tadpole response to the alarm chemical is affected by factors such as water temperature, time of day, larval stage and feeding history, geographic origin of the tadpoles, and habituation. Information on these topics may enable us to optimize deployment, so that tadpoles encounter pheromone at the times and places that confer maximum effect. In our studies, tadpole density, nutritional state, larval stage, and geographic origin had little effect on the intensity of the alarm response, but tadpoles reacted most strongly in higher water temperatures and during daylight hours. Repeated, once-daily exposure to pheromone did not induce habituation, but repeated exposure at 15-min interva
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| 25. |
- Hagman, Mattias, et al.
(author)
-
Fatal attraction: adaptations to prey on native frogs imperil snakes after invasion of toxic toads.
- 2009
-
In: Proceedings of the Royal Society of London. Biological Sciences. - 0962-8452 .- 1471-2954. ; 276, s. 2813-2818
-
Journal article (peer-reviewed)abstract
- Adaptations that enhance fitness in one situation can become liabilities if circumstances change. In tropical Australia, native snake species are vulnerable to the invasion of toxic cane toads. Death adders (Acanthophis praelongus) are ambush foragers that (i) attract vertebrate prey by caudal luring and (ii) handle anuran prey by killing the frog then waiting until the frog's chemical defences degrade before ingesting it. These tactics render death adders vulnerable to toxic cane toads (Bufo marinus), because toads elicit caudal luring more effectively than do native frogs, and are more readily attracted to the lure. Moreover, the strategy of delaying ingestion of a toad after the strike does not prevent fatal poisoning, because toad toxins (unlike those of native frogs) do not degrade shortly after the prey dies. In our laboratory and field trials, half of the death adders died after ingesting a toad, showing that the specialized predatory behaviours death adders use to capture and process prey render them vulnerable to this novel prey type. The toads' strong response to caudal luring also renders them less fit than native anurans (which largely ignored the lure): all toads bitten by adders died. Together, these results illustrate the dissonance in behavioural adaptations that can arise following the arrival of invasive species, and reveal the strong selection that occurs when mutually naive species first interact.
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| 26. |
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| 27. |
- Hagman, Mattias, et al.
(author)
-
Grass snakes (Natrix natrix) in Sweden decline together with their anthropogenic nesting-environments
- 2012
-
In: Herpetological Journal. - : British Herpetological Society. - 0268-0130. ; 22:3, s. 199-202
-
Journal article (peer-reviewed)abstract
- In this paper we show that the number of grass snake (Natrix natrix L.) specimens deposited in Swedish museum collections has declined in the last eighty years, and that this is correlated with a dramatic national decrease in the number of livestock holdings. These results support the hypothesis that Swedish grass snakes are declining and that this may be linked to a loss of important nesting-environments provided by open manure heaps in small-scale farming. Our study suggests that information obtained from museum databases potentially may be used to explore population trends for snakes and other reptiles.
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| 28. |
- Hagman, Mattias, et al.
(author)
-
Larval alarm pheromones as a potential control for invasive cane toads (Bufo marinus) in tropical Australia
- 2009
-
In: Chemoecology. - : Springer Science and Business Media LLC. - 0937-7409 .- 1423-0445. ; 19, s. 211-217
-
Journal article (peer-reviewed)abstract
- Novel approaches to control invasive species are urgently needed. Cane toads (Bufo marinus) are large, highly toxic anurans that are spreading rapidly through tropical Australia. Injured toad larvae produce an alarm pheromone that elicits rapid avoidance by conspecifics but not by frog larvae. Experiments in outdoor ponds show that repeated exposure to the pheromone reduced toad tadpole survival rates (by > 50%) and body mass at metamorphosis (by 20%). The alarm pheromone did not induce tadpoles to seek shelter, but accelerated ontogenetic differentiation. Perhaps reflecting mortality of weaker individuals during larval life, growth rates post-metamorphosis were higher in animals emerging from the pheromone exposure treatment than from the control treatment. Nonetheless, body size differentials established at metamorphosis persisted through the first 8 days of post-metamorphic life. We will need substantial additional research before evaluating whether the alarm pheromone provides a way to reduce cane toad recruitment in nature, but our field trials are encouraging in this respect.
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| 29. |
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| 30. |
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| 31. |
- Hagman, Mattias, et al.
(author)
-
Many Paths to a Common Destination : Morphological Differentiation of a Functionally Convergent Visual Signal
- 2016
-
In: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 188:3, s. 306-318
-
Journal article (peer-reviewed)abstract
- Understanding the interacting outcomes of selection and historical contingency in shaping adaptive evolution remains a challenge in evolutionary biology. While selection can produce convergent outcomes when species occupy similar environments, the unique history of each species can also influence evolutionary trajectories and result in different phenotypic end points. The question is to what extent historical contingency places species on different adaptive pathways and, in turn, the extent to which we can predict evolutionary outcomes. Among lizards there are several distantly related genera that have independently evolved an elaborate extendible dewlap for territorial communication. We conducted a detailed morphological study and employed new phylogenetic comparative methods to investigate the evolution of the underlying hyoid that powers the extension of the dewlap. This analysis showed that there appear to have been multiple phenotypic pathways for evolving a functionally convergent dewlap. The biomechanical complexity that underlies this morphological structure implies that adaptation should have been constrained to a narrow phenotypic pathway. However, multiple adaptive solutions have been possible in apparent response to a common selection pressure. Thus, the phenotypic outcome that subsequently evolved in different genera seems to have been contingent on the history of the group in question. This blurs the distinction between convergent and historically contingent adaptation and suggests that adaptive phenotypic diversity can evolve without the need for divergent natural selection.
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| 32. |
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| 33. |
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| 34. |
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| 35. |
- Hagman, Mattias
(author)
-
Pheromone-induced life-history shifts : a novel approach to controlling invasive toads
- 2010
-
In: Communicative & Integrative Biology. - 1942-0889. ; 3:3, s. 238-239
-
Journal article (peer-reviewed)abstract
- In a recent paper,1 we showed that recurrent exposure to alarm pheromones reduced development time and size at metamorphosis in larval cane toads (Bufo marinus). Subsequent measurements of post-metamorphic toads revealed larger parotoid glands relative to body size and increased amounts of bufalin (a toxic bufodienalide) in animals from the experimental treatment, suggesting increased investment in chemical defenses. These findings are of interest for evolutionary theory. But the study was also part of a larger conservation-based research program of which this pheromone work was an important component in the development of a management strategy for reducing the ecological impact of invasive cane toads in Australia. For example, our study1 aimed to quantify biochemical and life-history effects as well as assess the likely longterm impact of pheromone exposure on toads. In this addendum, I discuss the conservation potential of our research, with emphasis on exploiting alarm pheromones to induce viability reducing life-history shifts.
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| 36. |
- Hagman, Mattias
(author)
-
Pilgiftsgrodor
- 1999
-
In: Terrariet. - 1404-7519. ; 6:12, s. 4-18
-
Journal article (pop. science, debate, etc.)
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| 37. |
- Hagman, Mattias
(author)
-
Pond usage by anuran amphibians
- 2011
-
In: Ponds: Formation, Characteristics and Uses. - New York : Nova Science Publishers, Inc.. - 9781617613777 ; , s. 1-36
-
Book chapter (peer-reviewed)
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| 38. |
- Hagman, Mattias, et al.
(author)
-
Spawning-site selection by feral cane toads (Bufo marinus) at an invasion front in tropical Australia
- 2006
-
In: Austral ecology (Print). - : Wiley. - 1442-9985 .- 1442-9993. ; 31:5, s. 551-558
-
Journal article (peer-reviewed)abstract
- Spawning sites are a critical and often scarce resource for aquatic-breeding amphibians, including invasive species such as the cane toad (Bufo marinus). If toads select spawning sites based on habitat characteristics, we can potentially manipulate those characteristics to either enhance or reduce their suitability as breeding sites. We surveyed 25 spawning sites used by cane toads, and 25 adjacent unused sites, in an area of tropical Australia recently invaded by these feral anurans. Water chemistry (pH, conductivity, salinity, turbidity) was virtually identical between the two sets of waterbodies, but habitat characteristics were very different. Toads selectively oviposited in shallow pools with gradual rather than steep slopes, and with open (unvegetated) gradually sloping muddy banks. They avoided flowing water, and pools with steep surrounds. In these respects, cane toads broadly resemble previously studied toad species in other parts of the world, as well as conspecifics within their natural range in South America.
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| 39. |
- Hagman, Mattias, et al.
(author)
-
Species-specific communication systems in an introduced toad compared with native frogs in Australia
- 2009
-
In: Chemoecology. - : Springer Science and Business Media LLC. - 0937-7409 .- 1423-0445. ; 19:4, s. 211-217
-
Journal article (peer-reviewed)abstract
- Novel approaches to control invasive species are urgently needed. Cane toads (Bufo marinus) are large, highly toxic anurans that are spreading rapidly through tropical Australia. Injured toad larvae produce an alarm pheromone that elicits rapid avoidance by conspecifics but not by frog larvae. Experiments in outdoor ponds show that repeated exposure to the pheromone reduced toad tadpole survival rates (by >50%) and body mass at metamorphosis (by 20%). The alarm pheromone did not induce tadpoles to seek shelter, but accelerated ontogenetic differentiation. Perhaps reflecting mortality of weaker individuals during larval life, growth rates post-metamorphosis were higher in animals emerging from the pheromone exposure treatment than from the control treatment. Nonetheless, body size differentials established at metamorphosis persisted through the first 8 days of post-metamorphic life. We will need substantial additional research before evaluating whether the alarm pheromone provides a way to reduce cane toad recruitment in nature, but our field trials are encouraging in this respect.
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| 40. |
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| 41. |
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| 42. |
- Hagman, Mattias
(author)
-
Terrarieteknik och växter
- 2001
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In: Terrariet. ; 8:10, s. 3-12
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Journal article (pop. science, debate, etc.)
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| 43. |
- Hagman, Mattias, et al.
(author)
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Understanding the toad code : behavioural responses of cane toad (Chaunus marinus) larvae and metamorphs to chemical cues
- 2008
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In: Austral Ecology. - : Wiley. - 1442-9985. ; 33:1, s. 37-44
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Journal article (peer-reviewed)abstract
- Larvae of many anuran taxa display strong behavioural responses to chemical cues, including alarm signals from injured conspecific tadpoles. We exposed tadpoles and metamorphs from an Australian population of the invasive cane toad (Chaunus [Bufo] marinus) to a range of chemical stimuli and quantified their responses both in the laboratory and in the field. Filtered fluids containing scent cues from crushed conspecifics elicited strong avoidance from tadpoles, whereas other cues (e.g. scent of food, of native-range fish or urodele predators, and thermal stimuli) did not. Apparent aggregation of tadpoles in response to scent cues proved to be an artifact of tank design, and was an indirect consequence of avoidance of those cues. Field trials confirmed that free-ranging toad tadpoles and metamorphs avoided chemical cues from crushed conspecifics, suggesting that the chemicals inducing this response might provide an opportunity to develop targeted control methods for this invasive species.
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| 44. |
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| 45. |
- Hayes, Andrew, et al.
(author)
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Ontogenetic variation in the chemical defenses of cane toads (Bufo marinus): toxin profiles and effects on predators.
- 2009
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In: Journal of Chemical Ecology. - : Springer Science and Business Media LLC. - 0098-0331 .- 1573-1561. ; 35, s. 391-399
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Journal article (peer-reviewed)abstract
- We conducted a quantitative and qualitative chemical analysis of cane toad bufadienolides-the cardioactive steroids that are believed to be the principal cane toad toxins. We found complex shifts in toxin composition through toad ontogeny: (1) eggs contain at least 28 dominant bufadienolides, 17 of which are not detected in any other ontogenetic stage; (2) tadpoles present a simpler chemical profile with two to eight dominant bufadienolides; and (3) toxin diversity decreases during tadpole life but increases again after metamorphosis (larger metamorph/juvenile toads display five major bufadienolides). Total bufadienolide concentrations are highest in eggs (2.64 +/- 0.56 mu mol/mg), decreasing during tadpole life stages (0.084 +/- 0.060 mu mol/mg) before rising again after metamorphosis (2.35 +/- 0.45 mu mol/mg). These variations in total bufadienolide levels correlate with toxicity to Australian frog species. For example, consumption of cane toad eggs killed tadpoles of two Australian frog species (Limnodynastes convexiusculus and Litoria rothii), whereas no tadpoles died after consuming late-stage cane toad tadpoles or small metamorphs. The high toxicity of toad eggs reflects components in the egg itself, not the surrounding jelly coat. Our results suggest a dramatic ontogenetic shift in the danger that toads pose to native predators, reflecting rapid changes in the types and amounts of toxins during toad development.
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| 46. |
- Kelehear, Crystal, et al.
(author)
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Interactions between infective helminth larvae and their anuran host
- 2011
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In: Herpetologica. - 0018-0831 .- 1938-5099. ; 67:4, s. 378-385
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Journal article (peer-reviewed)abstract
- Detailed observations on interactions between parasites and prospective hosts during the infection process can clarify (1) the routes by which parasites enter the host and (2) the ability of prospective hosts to detect, avoid, or resist potential parasites. Such information can clarify determinants of host vulnerability. Infective larvae of the nematode Rhabdias pseudosphaerocephala entered the bodies of their anuran host the Cane Toad (Rhinella marina, formerly Bufo marinus) primarily through the orbit (i.e., by crawling over the surface of the toad's eye) rather than by burrowing through the skin (believed to be the usual route of infection for rhabditid parasites). In our experimental infections, metamorph Cane Toads detected infective R. pseudosphaerocephala larvae but did not avoid them, nor did they manage to restrict rates of infective larvae penetration by using behavioral means (the toads kicked at infective larvae but failed to dislodge them). Rhabdias pseudosphaerocephala cause damage to their toad host during the process of host entry and throughout the ensuing infection. Despite the high cost of infection and the low cost of avoidance, metamorph Cane Toads seem to lack effective parasite avoidance strategies.
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| 47. |
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| 48. |
- Lundgren, Nils, et al.
(author)
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Predicting the strength of Norway spruce by microwave scanning: A comparison with other scanning techniques
- 2007
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In: Wood and Fiber Science. - 0735-6161. ; 39, s. 167-172
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Journal article (peer-reviewed)abstract
- In this study, 90 boards of Norway spruce (Picea abies (L.) Karst.) sized 48 x 148 mm in cross-section, have been examined using different scanning and measurement techniques. All of the boards originated from a sawmill located in southern Finland. Planar X-ray scanning, microwave scanning, and grain-angle measurement have been performed. In addition, strength and elastic properties were assessed for eachpiece by four point bending. The purpose of the study was to relate the potential of microwave scanning compared to other, industrially available techniques and to explain the physiological background of the microwave responses. The results show that the microwave signal, after transmission through wood, contains information about the bending strength and the modulus of elasticity. The correlation to densityis a key factor. Annual ring width was also found to be correlated both to microwave measurements and strength properties.
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| 49. |
- Löwenborg Di Marino, Kristin, 1985-
(author)
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Nesting ecology of the grass snake (Natrix natrix) and its implications for conservation
- 2016
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Doctoral thesis (other academic/artistic)abstract
- The onset of agriculture about 12,000 years ago has had a major influence on the biodiversity of plants and animals. Unfortunately, the rapid changes in agricultural practices that has occurred in recent times has negatively affected many farmland species. One such species is the grass snake (Natrix natrix), which has been reported to decline in many parts of Europe, including Sweden. The grass snake is unique, not only in that it is the most northerly distributed oviparous reptile in the world, but also because of its habit of using anthropogenic heat sources such as manure heaps and composts as nesting-sites. Unfortunately changes in manure management and abandonment of farmlands have resulted in a decline and fragmentation of these environments. This may pose a threat for the northernmost populations of the grass snake, because natural nests in these areas may not provide sufficient heat for the eggs to hatch. The eggs and embryos of reptiles are highly sensitive to incubation temperatures, which can influence not only hatching success but also many phenotypic traits in the hatchlings. In this thesis I used a series of laboratory and field experiments to investigate the importance of anthropogenic heat sources for the reproductive ecology of cold-climate populations of grass snakes. More specifically, I aimed to investigate thermal regimes of nests and how they influence embryonic development and offspring traits associated with survival and fitness. The results showed that manure heaps and composts are significantly warmer than potential natural nests and that natural nests do not provide sufficient heat to sustain embryonic development. Further, manure heaps were warmer and more constant in temperature than composts, resulting in higher hatching success and earlier hatching in manure heaps. The higher thermal variability in composts increased the frequency of abnormalities that are likely to negatively affect survival and fitness. In conclusion, this thesis shows that the use of anthropogenic heat sources has enabled grass snakes to expand their range farther north than any other oviparous reptile and that the thermal dichotomy in the primary nesting environments used by grass snakes contribute to important life-history variation in this species. These findings have important implications for conservation of reptile populations in general and grass snakes in particular.
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| 50. |
- Löwenborg, Kristin, et al.
(author)
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Agricultural by-products provide critical habitat components for cold-climate populations of an oviparous snake (Natrix natrix)
- 2012
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In: Biodiversity and Conservation. - : Springer Science and Business Media LLC. - 0960-3115 .- 1572-9710. ; 21:10, s. 2477-2488
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Journal article (peer-reviewed)abstract
- Populations of snakes and other reptiles are declining worldwide. Habitat loss and degradation is thought to be a significant factor in these declines, so to improve management strategies it is important to increase our understanding of reptilian habitat requirements. Modern agriculture is abandoning the tradition of gathering compost and manure in large heaps. Consequently these unusually warm environments are disappearing from the landscape. This may imperil populations of grass snakes (Natrix natrix) that rely on these anthropogenic heat sources to incubate their eggs. We conducted a relocation experiment to examine if eggs can develop successfully in other more natural environments that grass snakes potentially could utilize in the absence of manure heaps and compost piles. We found that hatching success was high (71 %) when we placed eggs in manure heaps and non-existent (0 %) when we placed them in potential ‘natural’ nests. Placement in compost piles resulted in intermediate (43 %) hatching success. Eggs in manure heaps hatched earlier than eggs in compost piles and thermal data from the nests showed that temperatures were higher and more stable in manure heaps than in compost piles and potential ‘natural’ nests. Jointly these results suggest that manure heaps generally provide a better nesting habitat than compost piles, attributable to thermal differences between the environments. Our findings facilitate improvement of current management strategies and have implications for conservation of oviparous reptiles in general.
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