| ontogeny of the bizarre: an osteological description of pipa pipa (anura: pipidae), with an account of skeletal development in the species. | the adult osteology of the direct-developing pipid frog, pipa pipa, is described based on cleared-and-stained and dry skeletal specimens. observations on skeletal development are based on cleared-and-stained embryos and young removed from the backs of preserved females. osteologically, p.pipa is distinguished from its congeners and other pipid anurans by its large size and peculiar skull, which is extremely depressed and hyperossified. skulls of the smallest individuals are not significantly dif ... | 2000 | 10629097 |
| effect of predator-prey phylogenetic similarity on the fitness consequences of predation: a trade-off between nutrition and disease? | a largely neglected aspect of foraging behavior is whether the costs and benefits of predation vary as a function of phylogenetic (i.e., genetic) similarity between predator and prey. prey of varying phylogenetic similarities to predators might differ in value because both the risk of pathogen transmission and the nutritional quality of prey typically decline with decreasing phylogenetic similarity between predator and prey. i experimentally evaluated this hypothesis by feeding omnivorous spadef ... | 2000 | 10718730 |
| character displacement in polyphenic tadpoles. | 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 competi ... | 2000 | 11108600 |
| how fluctuating competition and phenotypic plasticity mediate species divergence. | causal evidence linking resource competition to species divergence is scarce. in this study, we coupled field observations with experiments to ask if the degree of character displacement reflects the intensity of competition between two closely related spadefoot toads (spea bombifrons and s. multiplicata). tadpoles of both species develop into either a small-headed omnivorous morph, which feeds mostly on detritus, or a large-headed carnivorous morph, which specializes on and whose phenotype is i ... | 2002 | 12144021 |
| differential selection to avoid hybridization in two toad species. | the fitness consequences of hybridization critically affect the speciation process. when hybridization is costly, selection favors the evolution of prezygotic isolating mechanisms (e.g., mating behaviors) that reduce heterospecific matings and, consequently, enhance reproductive isolation between species (a process termed reinforcement). if, however, selection to avoid hybridization differs between species, reinforcement may be impeded. here, we examined both the frequency and fitness effects of ... | 2002 | 12389729 |
| ecological opportunity and phenotypic plasticity interact to promote character displacement and species coexistence. | we investigated the roles of resource availability and phenotypic plasticity in promoting ecological character displacement (i.e., trait evolution stemming from resource competition between species). because ecological character displacement generates new populations that differ in resource use, this process should only occur when exploitable resources are available. we tested this hypothesis in two species of spadefoot toads (spea bombifrons and s. multiplicata) whose tadpoles use phenotypic pl ... | 2006 | 16602305 |
| field and experimental evidence for competition's role in phenotypic divergence. | resource competition has long been viewed as a major cause of phenotypic divergence within and between species. theory predicts that divergence arises because natural selection favors individuals that are phenotypically dissimilar from their competitors. yet, there are few conclusive tests of this key prediction. drawing on data from both natural populations and a controlled experiment, this paper presents such a test in tadpoles of two species of spadefoot toads (spea bombifrons and s. multipli ... | 2007 | 17348937 |
| analysis of range expansion in two species undergoing character displacement: why might invaders generally 'win' during character displacement? | ecological character displacement occurs when interacting species diverge in resource use and associated traits in response to selection to minimize resource competition between them. yet, when resource quality is asymmetric, the species that monopolizes the more profitable resource following character displacement may have higher fitness and therefore be deemed the 'winner'. here, we ask: does the winner tend to be the resident species (i.e. the earlier inhabitant of the geographic region where ... | 2008 | 18341542 |
| influence of sprint speed and body size on predator avoidance in new mexican spadefoot toads (spea multiplicata). | predator-prey interactions play an important role in community dynamics and may be important for promoting genetic diversification. diversification may be especially important when prey species have multiple anti-predator strategies available, but these strategies conflict with each other. for example, rapid sprint speed and large size are both thought to decrease vulnerability to many predators. a physiological trade-off between swimming speed and growth rate has been documented in many aquatic ... | 2009 | 18987891 |
| evidence for urea-induced hypometabolism in isolated organs of dormant ectotherms. | many organisms endure extended periods of dormancy by depressing their metabolism, which effectively prolongs the use of their endogenous energy stores. though the mechanisms of hypometabolism are varied and incompletely understood, recent work suggests that urea accumulation in autumn and early winter contributes to reduced metabolism of hibernating wood frogs (rana sylvatica). urea accumulation during dormancy is a widespread phenomenon, and it has long been presumed that numerous species from ... | 2010 | 19739087 |
| asymmetric reproductive character displacement in male aggregation behaviour. | reproductive character displacement-the evolution of traits that minimize reproductive interactions between species-can promote striking divergence in male signals or female mate preferences between populations that do and do not occur with heterospecifics. however, reproductive character displacement can affect other aspects of mating behaviour. indeed, avoidance of heterospecific interactions might contribute to spatial (or temporal) aggregation of conspecifics. we examined this possibility in ... | 2010 | 21177683 |
| distribution and reproductive strategies of gyrinicola batrachiensis (oxyuroidea: pharyngodonidae) in larvae of eight species of amphibians from nebraska. | abstract a total of 462 tadpoles and salamander larvae of 8 species was examined for the presence of gyrinicola batrachiensis from 5 locations in nebraska. infection by g. batrachiensis occurred in tadpoles of rana blairi, r. catesbeiana, r. pipiens, and bufo woodhousii. tadpoles of hyla chrysoscelis, spea bombifrons, and pseudacris maculata and larvae of ambystoma mavortium were not infected with g. batrachiensis. population structure, defined as prevalence, mean abundance, and mean intensity o ... | 2011 | 21506837 |
| development and characterization of nine polymorphic microsatellite markers for mexican spadefoot toads (spea multiplicata) with cross-amplification in plains spadefoot toads (s. bombifrons). | we developed nine polymorphic microsatellite markers for the mexican spadefoot toad, spea multiplicata. allele numbers range from five to 12, with observed heterozygosities from 0.48 to 0.87. because two loci are in linkage disequilibrium, these nine loci provide eight independent markers. three loci exhibit departure from hardy-weinberg equilibrium, possibly resulting from null alleles or population admixture. these markers will be useful for assessing population structure and relatedness in s. ... | 2008 | 21586053 |
| chiggers recently infesting spea spp. in texas, usa, were eutrombicula alfreddugesi, not hannemania sp. | upon re-examination of preserved larval chiggers collected from spadefoot toads (spea bombifrons and spea multiplicata) in the southern high plains of texas, usa, and identified previously as hannemania sp., we found them to be eutrombicula alfreddugesi. a review of previous reports of eutrombicula spp. chiggers on amphibian hosts provides context for current findings. all members of the genus hannemania are specialized larval parasites of amphibians, whereas larval e. alfreddugesi are generalis ... | 2011 | 21719825 |
| neurobiology of female mate choice in frogs: auditory filtering and valuation. | mate choice is a decision making process with profound implication for the reproductive success of both the sender and the chooser. preferences for conspecific over heterospecific males and for some conspecifics over others are typically mediated by a female's response to signals produced by males. and although one can experimentally describe a female's preference function, there is relatively little understood about the neural mechanisms mediating these preferences. in anurans, mating preferenc ... | 2017 | 29048536 |
| monoaminergic integration of diet and social signals in the brains of juvenile spadefoot toads. | social behavior often includes the production of species-specific signals (e.g. mating calls or visual displays) that evoke context-dependent behavioral responses from conspecifics. monoamines are important neuromodulators that have been implicated in context-dependent social behavior, yet we know little about the development of monoaminergic systems and whether they mediate the effects of early life experiences on adult behavior. we examined the effects of diet and social signals on monoamines ... | 2017 | 28659306 |
| genetic accommodation in the wild: evolution of gene expression plasticity during character displacement. | ecological character displacement is considered crucial in promoting diversification, yet relatively little is known of its underlying mechanisms. we examined whether evolutionary shifts in gene expression plasticity ('genetic accommodation') mediate character displacement in spadefoot toads. where spea bombifrons and s. multiplicata occur separately in allopatry (the ancestral condition), each produces alternative, diet-induced, larval ecomorphs: omnivores, which eat detritus, and carnivores, w ... | 2017 | 28612385 |
| genetic variation during range expansion: effects of habitat novelty and hybridization. | how species' ranges evolve remains an enduring problem in ecology and evolutionary biology. species' range limits are potentially set by the inability of peripheral populations to adapt to range-edge habitat. indeed, peripheral populations are often assumed to have reduced genetic diversity and population sizes, which limit evolvability. however, support for this assumption is mixed, possibly because the genetic effects of range expansion depend on two factors: the extent that habitat into which ... | 2017 | 28381622 |
| hybrid female mate choice as a species isolating mechanism: environment matters. | a fundamental goal of biology is to understand how new species arise and are maintained. female mate choice is potentially critical to the speciation process: mate choice can prevent hybridization and thereby generate reproductive isolation between potentially interbreeding groups. yet, in systems where hybridization occurs, mate choice by hybrid females might also play a key role in reproductive isolation by affecting hybrid fitness and contributing to patterns of gene flow between species. we ... | 2016 | 26717048 |
| leptin manipulation reduces appetite and causes a switch in mating preference in the plains spadefoot toad (spea bombifrons). | condition- or context-dependent mate choice occurs when females modify their mate preferences depending on their internal or external environment. while the ecological and evolutionary factors that favor the evolution of such plasticity are emerging, relatively little is known of the mechanisms underlying such choice. here we evaluated whether leptin, a protein hormone involved in the regulation of appetite, might affect the expression of condition-dependent mate choice decisions. to do so, we a ... | 2015 | 25919309 |
| failed sperm development as a reproductive isolating barrier between species. | hybrid male sterility is a common reproductive isolating barrier between species. yet, little is known about the actual developmental causes of this phenomenon, especially in naturally hybridizing species. we sought to evaluate the developmental causes of hybrid male sterility, using spadefoot toads as our study system. plains spadefoot toads (spea bombifrons) and mexican spadefoot toads (s. multiplicata) hybridize where they co-occur in the southwestern usa. hybrids are viable, but hybrid males ... | 2016 | 24261446 |
| diet alters species recognition in juvenile toads. | whether environmental effects during juvenile development can alter the ontogeny of adult mating behaviour remains largely unexplored. we evaluated the effect of diet on the early expression of conspecific recognition in spadefoot toads, spea bombifrons. we found that juvenile toads display phonotaxis behaviour six weeks post-metamorphosis. however, preference for conspecifics versus heterospecifics emerged later and was diet dependent. thus, the environment can affect the early development of s ... | 2013 | 24088562 |
| vortex formation and foraging in polyphenic spadefoot toad tadpoles. | animal aggregations are widespread in nature and can exhibit complex emergent properties not found at an individual level. we investigate one such example here, collective vortex formation by congeneric spadefoot toad tadpoles: spea bombifrons and s. multiplicata. tadpoles of these species develop into either an omnivorous or a carnivorous (cannibalistic) morph depending on diet. previous studies show s. multiplicata are more likely to develop into omnivores and feed on suspended organic matter ... | 2012 | 23185101 |
| a suite of molecular markers for identifying species, detecting introgression and describing population structure in spadefoot toads (spea spp.). | two congeneric species of spadefoot toad, spea multiplicata and spea bombifrons, have been the focus of hybridization studies since the 1970s. because complex hybrids are not readily distinguished phenotypically, genetic markers are needed to identify introgressed individuals. we therefore developed a set of molecular markers (amplified fragment length polymorphism, polymerase chain reaction-restriction fragment length polymorphism and single nucleotide polymorphism) for identifying pure-species ... | 2012 | 22564443 |
| kin-mediated morphogenesis in facultatively cannibalistic tadpoles. | inclusive fitness theory predicts that organisms can increase their fitness by helping or not harming relatives, and many animals modify their behavior toward kin in a manner consistent with this prediction. morphogenesis also may be sensitive to kinship environment, particularly in species where certain individuals facultatively develop structures that can be used against conspecifics as weaponry. we tested this hypothesis by examining whether and how consanguinity affected the probability that ... | 1997 | 28565095 |
| morphological novelty emerges from pre-existing phenotypic plasticity. | plasticity-first evolution (pfe) posits that novel features arise when selection refines pre-existing phenotypic plasticity into an adaptive phenotype. however, pfe is controversial because few tests have been conducted in natural populations. here we present evidence that pfe fostered the origin of an evolutionary novelty that allowed certain amphibians to invade a new niche-a distinctive carnivore morph. we compared morphology, gene expression and growth of three species of spadefoot toad tadp ... | 2018 | 29988161 |
| differential encoding of signals and preferences by noradrenaline in the anuran brain. | social preferences enable animals to selectively interact with some individuals over others. one influential idea for the evolution of social preferences is that preferred signals evolve because they elicit greater neural responses from sensory systems. however, in juvenile plains spadefoot toad (spea bombifrons), a species with condition-dependent mating preferences, responses of the preoptic area, but not of the auditory midbrain, mirror adult social preferences. to examine whether this separa ... | 2020 | 32647019 |
| female toads engaging in adaptive hybridization prefer high-quality heterospecifics as mates. | hybridization-interbreeding between species-is generally thought to occur randomly between members of two species. contrary to expectation, female plains spadefoot toads (spea bombifrons) can increase their evolutionary fitness by preferentially mating with high-quality males of another species, the mexican spadefoot toad (spea multiplicata). aspects of mexican spadefoot males' mating calls predict their hybrid offspring's fitness, and plains spadefoot females prefer mexican spadefoot males on t ... | 2020 | 32193328 |
| ontogeny of the skeleton of spea bombifrons (anura: pelobatidae). | the developing skeleton of a pelobatid frog, spea bombifrons, is described based on a series of 81 cleared-and-stained tadpoles and juveniles. most limb and limb-girdle elements commence ossification premetamorphically, along with the parasphenoid, frontoparietals, exoccipitals, and vertebral column, during gosner stage 36. the chondrocranium undergoes dramatic restructuring at the beginning of metamorphosis (ca. stage 40); and the nasal cartilages, prootics, premaxillae, nasals, maxillae, septo ... | 1989 | 29865698 |