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Toad Tadpoles (toad + tadpole)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

CHARACTER DISPLACEMENT IN POLYPHENIC TADPOLES

EVOLUTION, Issue 5 2000
David W. Pfennig
Abstract Biologists have long known that closely related species are often phenotypically different where they occur together, but are indistinguishable where they occur alone. The causes of such character displacement are controversial, however. We used polyphenic spadefoot toad tadpoles (Spea bombifrons and S. multiplicata) to test the hypothesis that character displacement evolves to minimize competition for food. We also sought to evaluate the role of phenotypic plasticity in the mediation of competitive interactions between these species. Depending on their diet, individuals of both species develop into either a small-headed omnivore morph, which feeds mostly on detritus, or a large-headed carnivore morph, which specializes on shrimp. Laboratory experiments and surveys of natural ponds revealed that the two species were more dissimilar in their tendency to produce carnivores when they occurred together than when they occurred alone. This divergence in carnivore production was expressed as both character displacement (where S. multiplicata's propensity to produce carnivores was lower in sympatry than in allopatry) and as phenotypic plasticity (where S. multiplicata facultatively enhanced carnivore production in S. bombifrons, and S. bombifrons facultatively suppressed carnivore production in S. multiplicata). In separate experiments, we established that S. bombifrons (the species for which carnivore production was enhanced) was the superior competitor for shrimp. Conversely, S. multiplicata (the species for which carnivore production was suppressed and omnivore production enhanced) was the superior competitor for detritus. These results therefore demonstrate that selection to minimize competition for food can cause character displacement. They also suggest that both character displacement and phenotypic plasticity may mediate competitive interactions between species. [source]

Species-specific communication systems in an introduced toad compared with native frogs in Australia

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2009
Mattias Hagman
Abstract 1.Lineage-specific communication systems may offer innovative ways of targeting control measures at invasive species. 2.Recent work has identified such a scenario in invasive cane toads (Bufo marinus) in Australia: toad tadpoles flee from chemical cues derived from crushed conspecifics, and this ,alarm pheromone' reduces tadpole survival rates and reduces body size at metamorphosis. 3.Before this method can be applied in the field, however, the signal's specificity needs to be tested against a wide range of Australian frog taxa, especially tropical species sympatric with cane toads. A signal that affected native frogs as well as toads clearly would be of little use for toad control. 4.Laboratory studies on cane toads and nine native frog taxa from the wet,dry tropics of the Northern Territory (Cyclorana australis, C. longipes, Limnodynastes convexiusculus, Litoria caerulea, L. dahlii, L. nasuta, L. rothii, L. rubella, Opisthodon ornatus) show that toad tadpoles rarely react to chemical cues from crushed frog tadpoles, and that frog tadpoles rarely react to chemical cues from crushed toad tadpoles. Crushed toad tadpoles occasionally elicited low-level attraction (to a potential food source) by frog tadpoles. 5.Overall, frog tadpoles were less responsive to chemical cues (either from crushed conspecifics or crushed toads) than were toad tadpoles. The low level of cross-lineage reactivity is encouraging for the feasibility of using cane toad alarm pheromones to control this invasive species in Australia; the risk of collateral damage to sympatric native frogs appears to be minimal. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Field and experimental evidence that competition and ecological opportunity promote resource polymorphism

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2010
RYAN A. MARTIN
Resource polymorphism , the occurrence within a single population of discrete intraspecific morphs showing differential resource use , has long been viewed as an important setting for evolutionary innovation and diversification. Yet, relatively few studies have evaluated the ecological factors that favour resource polymorphism. Here, we combine observations of natural populations with a controlled experiment to assess the role of intraspecific competition (specifically, the density of conspecifics) and ecological opportunity (specifically, the range of resources available) on the expression of resource polymorphism in spadefoot toad tadpoles. We found that greater conspecific densities and a greater range of available resources together promoted the expression of resource polymorphism. We conclude that, ecological opportunity, in the form of diverse available resources, along with intraspecific competition, may be a prerequisite for resource polymorphism to evolve, because such polymorphisms require diverse resources onto which each morph can specialize as an adaptive response to minimize competition. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 73,88. [source]