Alytes Cisternasii Research Articles

Dissimilarities in auditory tuning in midwife toads of the genusAlytes(Amphibia: Anura)

The auditory sensitivity in three species of the anuran genus Alytes (Alytidae) was examined to determine patterns of intra- and interspecific variation, relating these measurements to behavioural preferences measured in previous studies and to the adaptive and evolutionary significance of this sensory function. The audiograms obtained with multi-unit recordings in the torus semicircularis of 13 Alytes cisternasii, 10 Alytes obstetricans, and eight Alytes dickhilleni show two regions of enhanced sensitivity, between approximately 100–500 and 1200–2400 Hz, with minimum thresholds at approximately 40 and 45 dB SPL, respectively. The mean and range of the high-frequency region differed among species, although the sensitivity, measured as minimum thresholds, was similar. The region of high-frequency sensitivity was centred at approximately the frequency of the advertisement call in A. cisternasii but, in A. obstetricans and A. dickhilleni, was centred at frequencies higher than the conspecific calls. These results contrast with preferences for lower frequencies exhibited by Alytes in female phonotactic and in male evoked vocal responses. Such loose relationships between signals and receivers suggest that the divergence of the sound communication system in Alytes has implied environmental and phylogenetic factors in addition to sexual selection processes.

Propagation of natural toad calls in a Mediterranean terrestrial environment

Propagation patterns of animal acoustic signals provide insights into the evolution of signal design to convey signaler's information to potential recipients. However, propagation properties of vertebrate calls have been rarely studied using natural calls from individuals; instead playback calls broadcast through loudspeakers have been used extensively, a procedure that may involve acoustical and physical features differing from natural sounds. Measurements of the transmission characteristics of natural advertisement calls, which are simple tonal sounds, of the Iberian midwife toad, Alytes cisternasii, were carried out, and the results were compared with previously published results broadcasting recorded calls of the same species. Measurements of sound pressure level (SPL) of calls from individual male A. cisternasii revealed that the call amplitude decreases at distances of 1-8 m from the source at rates averaging 1-5 dB above spherical transmission loss in an omni-directional pattern. A comparison between SPLs of natural calls in the current study and of playback calls from a previous study showed that patterns of propagation did not differ in average values, but variance was significantly higher for natural calls. Results suggest that using broadcast signals for transmission experiments may result in a simplification of the conditions in which actual animals communicate in nature.

Behavioural responses of Iberian midwife toad tadpoles (Alytes cisternasii) to chemical stimulus of native (Natrix maura and Squalius pyrenaicus) and exotic (Procambarus clarkii) predators

Predation can be an important force of selection, resulting in the evolution or learning of antipredator defences in amphibian larvae. In the laboratory, we compared the behavioural responses of the tadpoles of Alytes cisternasii subjected to the chemical stimulus of an exotic predator, Procambarus clarkii, with the responses to the chemical stimuli of two of its native predators, the snake Natrix maura and the fish Squalius pyrenaicus, which employ different predation strategies. Tadpoles reacted more intensely to N. maura and then to P. clarkii, with no significant responses to S. pyrenaicus. The alteration in the use of the vertical axis of the aquaria was the antipredator behaviour more frequently used towards both native and exotic predators, and the adopted behaviour was adequate to the activity period and predation strategy of each predator. Alytes cisternasii tadpoles reacted to P. clarkii, a predator introduced about 20 years ago in the study area. These reactions may result from a micro-evolutionary process, but may also be a fortuitous response to a non-familiar cue. We can also not discard the possibility of learning by tadpoles since, due to the reproductive characteristics of this species, it was not possible to collect egg masses before their release in the aquatic environment.

Survival of Alytes cisternasii tadpoles in stream pools: a capture-recapture study using photo-identification

AbstractFor amphibians with complex life cycles, the regulation of populations may occur in each life history stage and although available data stress the importance of studying amphibian population dynamics during the larval stage, most studies so far still focus only on the adult phase, due to the difficulty to estimate larval survival under field conditions. Through a two-months capture-recapture study of 646 photo-identified tadpoles of Alytes cisternasii we aimed to estimate tadpole survival in isolated temporary stream pools – their main habitat – as well as to evaluate how pool characteristics and intraspecific competition (tadpole density) affect this parameter. Photo-identification was performed with the help of the software I3S. We used the POPAN formulation of the Jolly-Seber model to estimate survival rates and population size in 9 stream pools. Tadpole density varied from ∼1 to 40 tadpoles · m–2. Tadpole weekly survival was relatively high, varying from 75 to 99% · week–1. Among-pool differences in survival were best explained by pool depth, and not by tadpole density or other pool characteristics. The lower survival estimates were obtained for the deep pools. The very high survival estimates for some pools are an indication that this type of discrete habitat may play an important role for this species. To our knowledge, this is the first time that photo-identification is used to obtain estimates for survival and density of tadpoles.

High levels of population subdivision in a morphologically conserved Mediterranean toad (Alytes cisternasii) result from recent, multiple refugia: evidence from mtDNA, microsatellites and nuclear genealogies

Pleistocene glaciations often resulted in differentiation of taxa in southern European peninsulas, producing the high levels of endemism characteristic of these regions (e.g. the Iberian Peninsula). Despite their small ranges, endemic species often exhibit high levels of intraspecific differentiation as a result of a complex evolutionary history dominated by successive cycles of fragmentation, expansion and subsequent admixture of populations. Most evidence so far has come from the study of species with an Atlantic distribution in northwestern Iberia, and taxa restricted to Mediterranean-type habitats remain poorly studied. The Iberian Midwife toad (Alytes cisternasii) is a morphologically conserved species endemic to southwestern and central Iberia and a typical inhabitant of Mediterranean habitats. Applying highly variable genetic markers from both mitochondrial and nuclear genomes to samples collected across the species' range, we found evidence of high population subdivision within A. cisternasii. Mitochondrial haplotypes and microsatellites show geographically concordant patterns of genetic diversity, suggesting population fragmentation into several refugia during Pleistocene glaciations followed by subsequent events of geographical and demographic expansions with secondary contact. In addition, the absence of variation at the nuclear beta-fibint7 and Ppp3caint4 gene fragments suggests that populations of A. cisternasii have been recurrently affected by episodes of extinction and recolonization, and that documented patterns of population subdivision are the outcome of recent and multiple refugia. We discuss the evolutionary history of the species with particular interest in the increasing relevance of Mediterranean refugia for the survival of genetically differentiated populations during the Pleistocene glaciations as revealed by studies in co-distributed taxa.

Atlas de distribución y estado de conservación de los Anfibios de la Comunidad de Madrid

Successful management and conservation planning depend upon the availability, integration and updating of information provided by different disciplines. This paper compiles relevant information for the conservation of amphibians in Comunidad de Madrid (Spain). We obtained chorological information from 1384 sampling localities throughout the region of Madrid, and reviewed relevant scientific literature for the management of amphibian populations in this area. We found at least one amphibian species in 70,3% of sampled localities. Results are illustrated in distribution maps of all 18 species found: Salamandra salamandra, Pleurodeles waltl, Mesotriton alpestris, Lissotriton boscai, Triturus marmoratus, Triturus pygmaeus, Alytes obstetricans, Alytes cisternasii, Discoglossus galganoi, Discoglossus jeanneae, Pelobates cultripes, Pelodytes punctatus, Hyla arborea, Hyla meridionalis, Bufo bufo, Bufo calamita, Rana iberica and Rana perezi. Distribution maps are presented in five-kilometer side UTM grids cells. We compare and integrate our results with previous studies and outline groups of populations representing independent management units, for which we propose risk categories according to the criteria established by the International Union for the Conservation of Nature (IUCN) at the regional level. Finally, we point out the main threats for the survival of amphibian populations and discuss possible actions to improve their conservation status.

Female Iberian midwife toads (Alytes cisternasii) use call order to reach particular males in dense choruses

Call-timing mechanisms among anuran males calling within choruses are frequent, and previous studies have indicated that midwife toad females respond preferentially to these mechanisms. The results of multi-speaker tests performed here with midwife toads suggest that the temporal order of male calls within a dense chorus can determine the ability of females to locate the most attractive calls (in this instance the low-frequency calls emitted by larger males). When call emission was regular in the multi-speaker tests, most females chose the most attractive option (i.e., the speaker emitting the lower-frequency call). When call emission was not regular, however, most females failed to reach the most attractive option, selecting the speaker that emitted immediately after that emitting the most attractive call. These results support the idea that there may be benefits for smaller males that emit their less attractive calls close to those of larger, more attractive males in dense choruses. Less attractive males could exploit the attractiveness of nearby larger males calls by alternating their calls in an unordered sequence to reach receptive females.

Nonoptimal propagation of advertisement calls of midwife toads in Iberian habitats

This study compares the efficiency of transmission of the advertisement calls of two species of midwife toads, Alytes cisternasii and A. obstetricans, in both native and non-native habitats in the Iberian Peninsula. Recorded calls of both species and pure tones were broadcast at ten sites native to either the relatively small A. cisternasii or the larger A. obstetricans. A large variation in the patterns of excess attenuation between localities was observed for calls measured at distances of 0.5 to 8 m from a loudspeaker. However, attenuation rates were higher for calls of both species in habitats of A. obstetricans relative to habitats of A. cisternasii. The calls of A. obstetricans experienced lower attenuation rates than those of A. cisternasii in both conspecific and heterospecific localities. Thus, although A. cisternasii occupies habitats more favorable for sound transmission, its advertisement call spectrum is not optimized for these habitats; the calls of A. obstetricans suffer less attenuation in A. cisternasii habitats. This result argues against the notion that spectral features of the calls are adapted to enhance transmission efficiency in natural habitats, and suggests that differences in call dominant frequency between the two species result from constraints imposed by selection on body size.

Isolation and characterization of two dinucleotide and four tetranucleotide polymorphic microsatellite loci in the Iberian midwife toad Alytes cisternasii

AbstractThe Iberian midwife toad Alytes cisternasii is an endemic species of the southwestern and central parts of the Iberian Peninsula. Allozyme analysis of Iberian midwife toads indicated no inter‐ or intrapopulation variation and a more sensitive method is required to quantify genetic differentiation and gene flow between populations of this species. We describe here the development of primers for the amplification by the polymerase chain reaction (PCR) of six polymorphic microsatellite loci in A. cisternasii.

Female Preference Intensities on Different Call Characteristics and Symmetry of Preference Above and Below the Mean in the Iberian Midwife Toad Alytes cisternasii

AbstractThe intensity of female preference for call characteristics is measured in two‐speaker playback tests with female Iberian midwife toads ‘Alytes cisternasii’ using an experimental design that allows quantitative comparisons across characters. Female preferences do not appear to be symmetrical above and below the population mean, female preference being more efficient at discriminating against low quality competing males that at selecting optimum males among good ones. Female preference is significantly more effective selecting males calling at higher call rates (a highly variable call characteristic probably related to the physical state of the male) rather than selecting calls of low dominant frequency (a characteristic of low intra‐individual variation, related to male size and age).

Reproductive stage and phonotactic preferences of female midwife toads ( Alytes cisternasii )

We studied the phonotactic response of Alytes cisternasii females at different reproductive stages (before and after oviposition) toward two male call characteristics (call rate and frequency) differing in variability, as well as in the strength of female preference. We measured female phonotactic response over several repetitions by means of the frequency of selection of the population-preferred alternative, consistency of choice, frequency of reciprocal calling activity, frequency of null trials, and average approach time. Our results showed that female mating preferences in A. cisternasii are highly influenced by the variability of male call characteristics, while only female motivation is related to reproductive stage.

Double stimulation of the inner ear organs of an anuran species (Alytes cisternasii) with simple tonal advertisement calls

Midwife toads present one of the simplest calls in anurans, with the whole energy concentrated in a single band without frequency modulation. The tuning curves of the Iberian midwife toads Alytes cisternasii show the typical bimodal pattern in anurans, with two best excitatory frequencies at 0.412 kHz (corresponding to the amphibian papilla) and at 1.358 kHz (corresponding to the basilar papilla and matching the male call frequency). In this study, the hypothesis that complex calls arose in anurans because they were inherently more attractive to females, since they provided greater acoustic stimulation, was tested. However, our results indicate that splitting the call energy to stimulate both inner ear organs simultaneously, the male call is not more attractive to female midwife toads, but sometimes renders it unattractive. The biological role of the amphibian papilla is discussed in ecological and evolutionary terms.

Precopulatory behaviour and the evolutionary relationships of Discoglossidae

The phylogenetic relationships among primitive anurans remain controversial, even when several morphological and molecular approaches have been used in an attempt to resolve them. Nevertheless, very little effort has been made to study these relationships with behavioural data. We studied the relation between some precopulatory behaviour characters (male call characteristics and call recognition by females) and the different proposed phylogenies among the anuran genera Alytes, Discoglossus and Bombina. Different acoustic variables were analysed from male calls of different species of these genera; Alytes cisternasii females were used in recognition tests with calls from those species. A phenetic tree generated from male call characteristics grouped Bombina with Discoglossus and separated these two genera from Alytes, although the tree generated from female response data did not show such a clear result. A. cisternasii females are mostly using some features that are absent in Alytes calls in order to recognize male calls. The two characters, mapped onto the three alternative phylogenetic proposals, did not resolve the trichotomy among the three genera, but suggested that the studied behavioural characters have a clear phylogenetic load. Die phylogenetischen Verwandtschaftsbeziehungen bei den primitiven Anuren werden immer noch kontrovers diskutiert, auch wenn mehrere morphologische und molekulare Untersuchungen gemacht wurden, um zu einer Lösung zu gelangen. Wenige Bemühungen wurden allerdings bisher unternommen, diese Beziehungen mit Hilfe von Verhaltensmerkmalen zu studieren. Wir haben deshalb einige Merkmale des präkopulatorischen Paarungsverhaltens (Charakteristika der männlichen Paarungsrufe und deren Erkennung durch die Weibchen) herangezogen und sie mit den verschiedenen vorgeschlagenen Phylogenien der Anurengattungen Alytes, Discoglossus und Bombina verglichen. Verschiedene akustische Variable der Paarungsrufe der unterschiedlichen Arten dieser Gattungen wurden analysiert und Weibchen der Art Alytes cisternasii für einen Test zur Erkennung der Rufe jener Arten herangezogen. Ein phenetischer Baum, der aus den Charakteristika der Rufe der Männchen abgeleitet wurde, stellt Bombina und Discoglossus in eine Gruppe und separiert sie von Alytes, wenn auch der Baum, der sich aus den Antworten des Weibchens ergibt, kein solch klares Ergebnis zeigt. Die Weibchen von A. cisternasii verwenden vorwiegend solche Eigenschaften zur Erkennung, die bei den Alytes-Rufen fehlen. Die Merkmale der beiden untersuchten Charakter, eingeordnet in die drei vorgeschlagenen phylogenetischen Gruppierungen, konnte die Trichotomie unter den drei Genera nicht auflösen, läßt aber vermuten, daß die untersuchten Verhaltensmerkmale eindeutig phylogenetisch belastet sind.

The functionality of female reciprocal calls in the Iberian midwife toad (Alytes cisternasii): female-female acoustic competition?

Female midwife toads (genus Alytes) emit highly variable reciprocal calls of unclear function prior to and during courtship. In some species, female-female competition, expressed as physical fighting, has been reported. Males of Majorcan midwife toads (Alytes muletensis) show phonotactic response to female calls, and females of Iberian midwife toads (Alytes cisternasii) respond differently according to the male call characteristics. In this study, I test the hypothesis of female-female acoustic competition as an additional function of female reciprocal calls. Playback tests indicate that female calls are not clearly involved in female acoustic competition in the Iberian midwife toad, therefore female calls could be directed at males rather than towards competitive females.

Signal discrimination by female Iberian midwife toads (Alytes cisternasii)

Coevolution between signaller and receiver is critical in signal evolution. Midwife toads produce simple calls that are similar among species. I conducted phonotaxis experiments with female midwife toads to study their tolerance to alteration of conspecific advertisement calls. Large alterations in amplitude and frequency modulation rendered the typical call unattractive while smaller alterations in both amplitude and frequency modulation did not influence call attractiveness. Frequency modulations appear to be weighted more heavily in discrimination tests. The evolutionary significance of female tolerance is discussed.

Female preference function related to precedence effect in an amphibian anuran (Alytes cisternasii): tests with non-overlapping calls

We quantified precedence effect (measured as female preference for the leading calls in an acoustic interaction between two males) with non-overlapping, simulated male calls presented with various phase relationships to female Iberian midwife toads (Alytes cisternasii) in two-speaker phonotaxis playback tests. The resulting information determines the shape of the female preference function for intercall delays. Females preferentially approached leading callers for most tested phase angles. We found a gradation in the degree to which females selected the leader. They tended to exert a strong preference for the leader in 30 test, and at higher phase angles, the overall preference was weaker and graded (the higher the phase angle, the lower the preference). Other parameters of female preference (latency and repeatability) also had a graded relationship with phase angle value. The sharp difference in probability of approach between 30 and 60 is consistent with a mechanism of male calling inhibition immediately after hearing a competitor’s call previously described in other taxa. In natural interactions, male A. cisternasii adjust the timing of their calls to a phase angle that provides a slight but significant advantage to the leading caller. Key words: Alytes cisternasii, anurans, calling, female preference, midwife toads, precedence effect. [Behav Ecol 13:149–153 (2002)]

Female reciprocal calling in the Iberian midwife toad (Alytes cisternasii) varies with male call rate and dominant frequency: implications for sexual selection.

Male midwife toads (Alytes cisternasii) responded differently depending on the call frequency and call rate of other males. I tested female Iberian midwife toads with the same set of stimuli used earlier with males. Females responded faster to high call rates, and female vocal activity was greater in response to low-frequency male calls. Thus, in both sexes, the vocal response differs in the same direction according to signal frequency variation, but the magnitude of the response is greater in males than in females. In the light of these results, I discuss the implications for sexual selection of this reciprocal calling.

Female preference in complex acoustical environments in the midwife toads Alytes obstetricans and Alytes cisternasii

Gravid females of Alytes obstricans and Alytes cisternasii were tested with synthetic calls in seven-speaker playback tests. A first, “mean-centered” test presented calls with frequencies representing an array of different calls spanning over the range of the population (±2.25 SD). In this test, females of both species approached a synthetic call that was lower than the average call frequency of the male population although the difference was significant only for A. obstetricans. The regression between female weight and size and preferred frequency was not significant in either species. These results confirm the reported trends of females preferring lower frequency calls (corresponding to larger males) based on two-speaker playback tests for A. obstetricans. For A. cisternasii, the lack of significance of the seven-speaker test suggests that the preference trend previously found in two-speaker tests may be obscured in more complex acoustical environments. A second “supernormal stimulus” test presented females with calls ranging from the lowest frequency values of the male population (−2.25 SD) and lower, up to −6.75 SD beyond the range. In both species females preferentially approached calls higher than the mean frequency of the stimulus presented. This result suggests that in both cases selection for low frequencies is not open ended, and that the preferred frequency is within the range of the male population.

Egg Mass and Size of Tadpoles at Hatching in the Midwife Toads Alytes obstetricans and Alytes cisternasii: Implications for Female Choice

In Alytes obstetricans, the eggs of males carrying larger egg complements were smaller in mass and produced smaller tadpoles at hatching. In A. cisternasii, the total number of eggs in the male complement was not related to average egg mass or tadpole size. Alytes obstetricans males with large egg complements from several females could obtain their matings over a prolonged period. I tested the hypothesis that the negative correlation between progeny size and total number of eggs in the male complement could be a result of greater asynchrony in the development of the egg complement of male A. obstetricans. A simulation determined that the differences between species were not explained by differences in asynchrony in development between clutches of different females in a single male egg complement. Alytes obstetricans males with larger egg complements released their eggs later in the season and, hence, exposed their progeny to desiccation, whereas this did not occur in A. cisternasii in which the reproductive phenology was much more explosive. Therefore, in A. obstetricans, female preference for males that were already carrying eggs would be nonadaptive at the level of tadpole size at hatching.

The courtship and mating of the Iberian midwife toad Alytes cisternasii (Amphibia: Anura: Discoglossidae)

Sexual encounters were staged in the laboratory among hormonally‐primed Iberian midwife toads, Alytes cisternasii. In this species, pairing and fertilization are terrestrial. The male cares for the developing embryos on land, carrying them twined around his hind limbs until they hatch into tadpoles which he releases into water; his investment in the offspring then ends. The courtship of A. cisternasii can be divided into a pre‐ and post‐ovulatory phase. An encounter is initiated when the female approaches the male and is clasped by him in inguinal amplexus. Both the male and the female produce vocalizations during the period prior to the initiation of amplexus. During amplexus, only the female vocalizes, changing her call to one that is of lower intensity, longer duration and more regularly emitted than before. During inguinal amplexus, the male engages in bouts of intense pedalling and gentle rocking behaviour, each bout being initiated when the female repositions herself beneath him. Rocking and pedalling cease when the female ovulates, at which time she exhibits a posture that we call Unkenkrampf. Ovulation occurs at this time, and is followed by sperm release by the male (seen as a series of lateral compressions of his body). After sperm release, the male moves forwards to engage the female in cervical amplexus and then manoeuvres his hind limbs such that the egg string becomes tangled around his ankles. The female may exhibit additional episodes of Unkenkrampf during this period, but these are not accompanied by further egg release. Episodes of Unkenkrampf (without ovulation) also may occur after the male dismounts from the female. Similar behaviour patterns to those observed in the laboratory are seen in natural populations of A. cisternasii. We compare and contrast our observations of A. cisternasii with those of other authors for this species and also for the common midwife toad, A. obstericans.