| 1. |
|
|
| 2. |
- Forsman, Anders, et al.
(författare)
-
Association of coloration mode with population declines and endangerment in Australian frogs
- 2009
-
Ingår i: Conservation Biology. - : Wiley. - 0888-8892 .- 1523-1739. ; 23:6, s. 1535-1543
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 3. |
- Forsman, Anders, et al.
(författare)
-
Calling is an honest indicator of paternal genetic quality in male poison frogs
- 2006
-
Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 60:10, s. 2148-2157
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 4. |
- Hagman, Mattias, et al.
(författare)
-
Alarm cues experienced by cane toad tadpoles affect post-metamorphic morphology and chemical defences
- 2009
-
Ingår i: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 23, s. 126-132
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 5. |
- Hagman, Mattias, et al.
(författare)
-
Australian tadpoles do not avoid chemical cues from invasive cane toads (Bufo marinus)
- 2008
-
Ingår i: Wildlife research (East Melbourne). - 1035-3712 .- 1448-5494. ; 35:4, s. 59-64
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 6. |
|
|
| 7. |
- Hagman, Mattias, et al.
(författare)
-
Deceptive digits : the functional significance of toe waving by cannibalistic cane toads (Bufo marinus)
- 2008
-
Ingår i: Animal Behaviour. - : Elsevier BV. - 0003-3472 .- 1095-8282. ; 75, s. 123-131
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
- Hagman, Mattias, et al.
(författare)
-
Effects of invasive cane toads on Australian mosquitoes : does the dark cloud have a silver lining?
- 2007
-
Ingår i: Biological Invasions. - : Springer Science and Business Media LLC. - 1387-3547 .- 1573-1464. ; 9:4, s. 445-452
-
Tidskriftsartikel (refereegranskat)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.
|
|
