Seasonal patterns of activity and community structure in an amphibian assemblage at a pond network with variable hydrology

We studied community structure and seasonal activity patterns in a system of four ponds with seasonally-variable hydrology at a Mediterranean area in central Italy. We used a set of field methods to assess species presence and relative frequency of observation. The network of ponds was inhabited by six species of amphibians, two salamanders and four frogs. The breeding phenology of the six species did not vary remarkably among ponds, but there were significant differences among species in use of ponds. Factorial analysis of pond similarity drawn from percentage composition of the amphibian fauna, revealed that each of the four ponds was treatable as independent units, with no influence of relative inter-pond distance. PCA analysis allowed us to spatially arrange the amphibian species into three main groups: two were monospecific groups (i.e., Triturus vulgaris and Bufo bufo) and the third consisted of those species that selected not only the largest-deepest ponds, but also the ephemeral ones (i.e., Triturus carnifex, Hyla intermedia, the green frogs and Rana dalmatina). Our results suggest that the inter-pond differences in riparian vegetation, water depth, aquatic vegetation structure/abundance, and soil composition may produce differences among pond ecological characteristics (i.e., water turbidity and temperature, shelter availability, abundance of oviposition micro-sites), which may in turn influence different patterns of use by amphibians. To our knowledge, this is the first study emphasizing the potential role of heterochrony in the maintenance of a high species richness in Mediterranean amphibian communities. Preservation of freshwater vertebrate biodiversity requires management and protection not only of the main ponds and water bodies but also the temporary and ephemeral shallow ponds.     

蛙类趋声行为的研究进展

蛙类是典型的依赖声音通讯的物种,具有季节性繁殖特点。繁殖季节雄性大多通过广告鸣叫竞争领地和吸引配偶,雌性通过雄性鸣声来评价个体特征及其所占有的资源,并以趋声行为完成配偶选择。趋声过程的行为学参数,通常用于检验动物对声音信号的偏爱和行为响应的特征。本文通过对蛙类趋声行为相关研究的回顾,总结其产生机制、评价方式及影响因素,并结合当前发展趋势对蛙类趋声行为未来的研究方向进行了展望。     

Mating behaviour and mating success in woodfrogs Rana sylvatica

Mating behaviour of woodfrogs was investigated in a woodland pond in southeastern Michigan. Males became sexually mature one year before females and outnumbered females by 5.6 to 1 at the breeding site. Males employed searching behaviour to obtain mates. Yearly male mating success varied from 0 to 2 matings, and larger males had a greater probability of mating than smaller males. The mating season lasted less than 10 days. Most egg masses were deposited in 1 m² of a 256-m² pond. Experimental introduction of egg masses to the breeding site indicated that presence of eggs was sufficient to stimulate egg deposition. The influence of selection for synchronous sexual receptivity in females, communal egg deposition, and delayed female sexual maturation on male mating behaviour and variation in male mating success is discussed.     

Flexible oviposition strategies in túngara frogs and their implications for tadpole spatial distributions

Because oviposition site selection is often studied in a single ecological context, little is known about flexibility in oviposition strategies. We studied the oviposition site selection strategies of túngara frogs ( Physalaemus pustulosus ) with respect to conspecific eggs and larvae in two different ecological contexts-arrays of artificial ponds and natural stream pools. We fit maximum likelihood models to sequential pond use data for both systems and found that strategies for oviposition differed greatly between the two systems. Within arrays of artificial ponds, túngara frogs avoided both conspecific egg masses and conspecific larvae. However, within a set of natural stream pools, túngara frogs consistently oviposited in the same pools from night to night, while many nearby ponds went unused. These variable strategies produced very different distributions of tadpoles among ponds, such that tadpoles tended to be evenly spread among artificial ponds, but highly clumped within stream pools. The difference between the two strategies appears to be an overriding effect of habitat quality. Surface area and the amount of leaf litter were all significant predictors of whether stream pools were used. Additionally, an experiment in which egg masses were either transplanted to, or removed from, selected stream pools provided no evidence that frogs in these pools used egg masses per se as a cue for oviposition. These results illustrate that oviposition strategies may be very flexible, allowing species to adjust strategies to different ecological contexts. Furthermore, they demonstrate that variation in oviposition strategies may have strong effects on egg and larval spatial distributions in patchy environments.     

Egg mass destroying and guarding behaviour of the giant water bug,Lethocerus deyrollei Vuillefroy (Heteroptera: Belostomatidae)

Egg mass destroying behaviour of femaleLethocerus deyrollei and male defending behaviour were observed in a densely vegetated concrete pond. In 3 of 9 cases of male-female interactions, the males successfully guarded their egg masses. In 4 of the 6 remaining cases in which the egg masses were destroyed by the female, females successfully took over the mate and laid their own egg masses the same night. These results suggest that male brooding guards the egg mass from females, as well as supplying eggs with water.     

Oviposition Site Selection and Spatial Predictability of Female White-faced Dragonflies (Leucorrhinia intacta) (Odonata: Libellulidae)

Location of breeding or egg-laying sites may be an important factor underlying social behavior of many organisms. We studied oviposition sites used by a population of Leucorrhinia intacta dragonflies at a small pond near Syracuse, NY, USA. Females preferentially used shallow water as an oviposition habitat. Shallow water increases egg hatching rate through temperature effects on development time and reduces predation on the female. Use of shallow water areas was reduced by locally high densities of territorial males. The same oviposition sites probably maximized the fitness of the male, female, and offspring, meaning that site selection did not necessitate fitness tradeoffs among these classes of individuals. Pond sectors used by ovipositing females were significantly correlated within and between years, but not within days or between consecutive days. Use of pond sectors within and between days was not related to the relative availability of the shallow water habitat, while seasonal use of pond sectors was related positively to availability of shallow water. In spite of the preference by females for ovipositing in shallow water, short-term location of females was not predictable and males could not search predictably good areas during a day. However, across a season, areas with more shallow water available were used for oviposition more than areas with limited substrate.     

Defining core habitat of local populations of the gray treefrog (Hyla versicolor) based on choice of oviposition site

Concern over amphibian population declines and loss of terrestrial and aquatic habitat have emphasized the need to define habitat requirements for each stage in a species' life history. The realization that pond-breeding amphibians spend most of their lives in the terrestrial environment suggests the need to protect terrestrial as well as aquatic habitat. Many studies on amphibian populations have focused on emigration from breeding sites to define habitat use; however these studies do not typically elucidate terrestrial activities of adults within the breeding season. We measured colonization rates of artificial pools by gray treefrogs (Hyla versicolor) at multiple distances from natural breeding ponds. We found a non-random distribution of egg deposition among distances, with 95% of eggs deposited within 15 m of the breeding pond. Additionally, we found that the time to first colonization of artificial pools increased with respect to distance. Our results indicate that adult gray treefrogs may travel up to 200 m within a breeding season, and that multiple breeding ponds may be considered part of a single population. We suggest that a minimum core terrestrial habitat of 60 m surrounding breeding sites is appropriate for protection of local populations of gray treefrogs.     

Frog breeding pond selection in response to predators and conspecific cues

Predators are a major influence on the breeding site selection decisions of anurans. Many species actively avoid breeding in habitat with predators when given the choice between predator and predator‐free sites. However, certain factors such as site fidelity or conflicting cues may preclude avoidance behavior. We conducted two experiments examining how western chorus frogs, Pseudacris triseriata, respond to predators, western mosquitofish, Gambusia affinis, using an array of artificial ponds located at two field sites. In one experiment, we added G. affinis to half of our experimental ponds and monitored subsequent colonization by frogs. We found that frogs laid significantly fewer eggs in ponds with fish compared to fishless ponds. In another experiment, we introduced an additional cue to complicate the decision‐making process and monitored colonization of ponds in response to treatments of conspecific breeding cues only (eggs), predators (G. affinis) only, and conspecific cues and predators. We found no significant differences in number of eggs deposited among these three treatments. Based on these results, P. triseriata does not always exhibit complete avoidance of fish predators, and avoidance may vary based on factors such as site fidelity or dispersal costs. This study represents a step toward understanding how multiple biotic factors at a breeding pond may influence anuran site selection behavior in the field.     

Female polyandry and size‐assortative mating in isolated local populations of the Japanese common toad Bufo japonicus

In anurans, female polyandry under male harassment is distributed across taxa because of external aquatic fertilization. According to the sexual selection theory, male–male competition for access to females is affected by the operational sex ratio (OSR) and population density. The Japanese common toad, Bufo japonicus, is widespread in mainland Japan, and like the European common toad, B. bufo, it engages in explosive breeding. In this study, we observed the breeding behaviour of B. japonicus in isolated local populations for over four years in two breeding ponds with different population sizes and densities: large‐low (L‐pond) and small‐high (S‐pond). We analysed the relative polyandry ratio in egg clutches laid by females and estimated the size‐assortative mating pattern to be an indicator of male–male competition in the two ponds. Both ponds tended to exhibit a size‐assortative mating pattern; however, the frequency of polyandry was different in the two ponds (L‐pond = 20% and S‐pond = 90%). Our results showed that polyandry could occur without multiple amplexus with a high population density, i.e. eggs were often fertilized by free‐swimming sperm in the small shallow pond. We propose that high female polyandry ratios without continuous male harassment are generated because of a male‐biased OSR and a high population density in the small pond. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 236–242.     

Is egg carrying attractive? Mate choice in the golden egg bug (Coreidae,Heteroptera)

In several species of fish, females select males that are already guarding eggs in their nests. It is a matter of debate as to whether a female selects a good nest site for her offspring (natural selection) or a male for his attractiveness (sexual selection). The golden egg bug, Phyllomorpha laciniata Vill, resembles fish in the sense that mating males carry more eggs than single males, but in the bugs, female mate choice is decoupled from egg site choice. The sexual selection hypothesis predicts that if females select males using male egg load as a cue for male quality, they should not mate with a male when eggs are removed, regardless of his mating attempts. When individual females were enclosed with an egg-loaded male and an unloaded male, they mated equally often with both males, although the loaded males courted more. In addition, when only successful males were used, females mated equally often with the loaded male and the unloaded male irrespective of sex ratio. Male choice rather than female choice affected mating frequency when sex ratio was equal. Therefore, females do not select the male by the eggs he carries, but successful males may receive many eggs due to egg dumping by alien females while they mate or as a consequence of mate guarding.     

Environmental predictability and remating in European blackbirds

We studied mate and site fidelity between years in an Englishpopulation of blackbirds (Turdus merula) from 1985 to 1991.Divorce was observed in 32% of 183 cases where mates had survivedfrom the previous breeding season. After divorces, females tendedto nest farther from their original site than males did, butthere was no sex difference in distance moved after the deathof a mate. The mean annual fledgling production of 60 m x 60m breeding sites was statistically repeatable among years, evenafter accounting for possible differences in reproductive performanceamong site-tenacious individuals. Divorce rates were greatestin low-quality sites. We found no annual fitness cost associatedwith mating with an unfamiliar bird. However, breeding in anew site cost on average one fledgling per year.     

Male nest site fidelity and female serial polyandry in lingcod (Ophiodon elongatus, Hexagrammidae)

Nest site fidelity and serial polyandry were examined in lingcod, Ophiodon elongatus, a teleost fish in which the nest-guarding male parent invests more heavily in parental care than the elusive female parent. Lingcod parental and progeny genotypes were established for fish spawning on a 200 m(2) section of Snake Island reef, British Columbia in two successive years to evaluate male and female mate choice (monogamy or polygamy) and nest site reuse by the same parents (nest site fidelity) and/or different parents (nest site affinity). Thirteen nests (egg masses) guarded by nine males and 14 nests guarded by seven males were observed in 2002 and 2003, respectively. No female laid more than one nest per season or spawned in the study area in both years. In contrast, at least six (86%) and possibly all seven (100%) of the 2003 guardian males had been guardian or auxiliary males in 2002. Both nest site affinity and extreme male nest site fidelity were observed, with at least four males reusing the exact same nest site. Serial polyandry resulting from the high male and low female nest site fidelity is consistent with predictions based on a low female parental investment and high rate of progeny loss to predation and cannibalism. Male polygyny, achieved primarily by cuckoldry within seasons, was enhanced by the lack of female fidelity between seasons. Polygamy in both sexes of nest-tending marine fish may minimize reproductive skew and maximize genetic diversity within populations.     

Female choice of sites versus mates in a coral reef fish,Thalassoma bifasciatum

To understand the dynamics of sexual selection, one needs to identify the basis of female choice in mating. Daily censuses showed that most spawns of individual female bluehead wrasses, Thalassoma bifasciatum, occurred at one of several available mating sites, either in a group-spawning aggregation of small males or with a large territorial male. Most females were not located near their principal mating site during the non-spawning period of the day. Females were thus exposed to other males and sites and should have had the opportunity for choice. When a resident territorial male disappeared or was removed experimentally from a mating site, females did not alter their fidelity to that site. Furthermore, manipulations showed that when a territorial male changed the location of his mating activity to an adjacent site, females did not follow him but continued to mate at their customary site. Thus mating sites, rather than the males occupying them, appeared to be the objects of female choice. The bright coloration and courtship behaviour of larger males may demonstrate the safety of a particular site rather than indicating some aspect of male quality.     

Oviposition site selectivity of some stream-dwelling caddisflies

Population dynamics depends upon the spatial distribution of individuals in heterogeneous environments. The various processes surrounding insect oviposition are central to understanding their population dynamics because the choice of oviposition site ultimately influences the survivorship and spatial distribution of their progeny. Aquatic insects are often assumed to have non-selective oviposition habits, but empirical data are scarce and selective oviposition may be quite common. We quantitatively sampled egg masses of stream-dwelling caddisflies (Trichoptera) that specialise in egg-laying on hard substrata underwater, in order to characterise oviposition site selectivity and test for communal oviposition. In a field survey of two Scottish streams, we sampled egg masses of three species, Polycentropus flavomaculatus, Hydropsyche siltalai, Rhyacophila dorsalis, with the aim of testing whether egg mass abundance varied with current (riffles vs. pools), location within the channel (margins vs. centre) and rock exposure (emergent vs. fully submerged). In one stream, we captured adults landing on emergent rocks and assessed whether females were modified morphologically for swimming. The egg masses of two species (P. flavomaculatus, H. siltalai) occurred primarily on submerged rocks in pool margins, and adult females had legs modified for swimming. In contrast, egg masses of R. dorsalis were most abundant on the underside of emergent rocks in riffles, and females were not modified for swimming. Communal oviposition was evident for all three species, with most egg masses aggregated on the minority of potential rocks. How females locate oviposition sites and the consequences of these highly specialised oviposition behaviours to the survival and spatial distribution of larvae now require investigation. The effects of these behaviours on population dynamics are likely to differ from terrestrial herbivores because oviposition sites are not food resources for these aquatic species.     

黄河下游平原农业景观异质性对两栖类生物栖息地可用性的影响

以黄河下游典型平原农业景观封丘县为研究区,基于图论的分析方法,采用概率连通性指数(PC)和斑块重要值(dPC_k)表征池塘栖息地可用性程度,在地理信息系统和R软件的支持下,分析了两栖类物种在250、500、1000和2000 m不同扩散能力下,反映池塘栖息地组成和构型的池塘平均面积(MS)以及池塘数量(NP)、至道路的最近距离(DR)组合作用对池塘栖息地可用性的影响.结果表明: 两栖类栖息地的可利用性与池塘数量、池塘平均面积和至道路的最近距离关系密切.在250 m扩散能力下,池塘平均面积和池塘数量是决定池塘可利用程度高低的重要影响因素;在500 m扩散能力下,池塘平均面积和至道路的最近距离对栖息地可用性的影响最为显著;在物种相对较高扩散能力下(1000和2000 m),池塘平均面积和池塘数量是最主要的影响因素.在平原农业景观中,两栖类生物及其栖息地的保护要充分考虑池塘斑块的数量、平均面积以及至道路的最近距离.     

Selective oviposition of the mayfly Baetis bicaudatus

Selective oviposition can have important consequences for recruitment limitation and population dynamics of organisms with complex life cycles. Temporal and spatial variation in oviposition may be driven by environmental or behavioral constraints. The goals of this study were to: (1) develop an empirical model of the substrate characteristics that best explain observed patterns of oviposition by Baetis bicaudatus (Ephemeroptera), whose females lay eggs under rocks protruding from high-elevation streams in western Colorado; and (2) test experimentally selective oviposition of mayfly females. We surveyed the number and physical characteristics of potential oviposition sites, and counted the number and density of egg masses in different streams of one watershed throughout two consecutive flight seasons. Results of surveys showed that variability in the proportion of protruding rocks with egg masses and the density of egg masses per rock were explained primarily by seasonal and annual variation in hydrology, and variation in geomorphology among streams. Moreover, surveys and experiments showed that females preferred to oviposit under relatively large rocks located in places with high splash associated with fast current, which may provide visual, mechanical or both cues to females. Experiments also showed that high densities of egg masses under certain rocks were caused by rock characteristics rather than behavioral aggregation of ovipositing females. While aggregations of egg masses provided no survival advantage, rocks selected by females had lower probabilities of desiccating during egg incubation. Our data suggest that even when protruding rocks are abundant, not all rocks are used as oviposition sites by females, due to female selectivity and to differences in rock availability within seasons, years, or streams depending on variation in climate and hydrogeomorphology. Therefore, specialized oviposition behavior combined with variation in availability of quality oviposition substrata has the potential to limit recruitment of this species.Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Kin Recognition and Incest Avoidance in Toads

Toads, like many amphibians, display breeding site fidelity.Individuals that return to natal ponds to breed are likely toencounter siblings as potential mates. We examined the geneticstructure of Bufo americanus breeding populations at five localitieswithin a 1 km radius. Mitochondrial DNA (mtDNA) haplotypes significantlydiffered among the breeding populations, but haplotype distributionsdid not differ from year to year within breeding sites. Natalphilopatry may account for these results. Although incest isthus possible, siblings rarely mate. Comparing haplotypes oftoads captured while mating, we found only 2 of 86 pairs thatcould possibly be siblings. We suggest that toads might recognizeand actively avoid close kin as mates. Advertisement vocalizationsgiven by males serve as potential cues by which females mightrecognize their kin. We recorded calls of males, in the field,and later obtained rank estimates of their relationships toone another by DNA fingerprinting of the nuclear genome. Theresemblance of males' calls was positively correlated with thesimilarity of their fingerprints. Significant differences incall characteristics were also found among breeding populations.Temporal parameters, rather than frequency components, encodekinship information. Recently developed techniques in moleculargenetics facilitate studies of the heritability of behavioraltraits in natural populations.     

Life stage specific variation in the occupancy of ponds by Litoria aurea,a threatened amphibian

Breeding aggregations are a reproductive strategy to increase mate finding opportunity. However, because aggregations skew the distribution of mature animals through conspecific attraction, rather than resource availability, the distribution of breeding sites may be reduced, so that not all suitable breeding sites are used. To examine the relationship between landscape and reproductive strategies of a threatened frog, Litoria aurea, we studied its distribution at Sydney Olympic Park over two breeding seasons. We aimed to: (i) determine the distribution and predictors of breeding ponds; and (ii) assess the significance of dispersal in the juvenile age‐class. We found that the distribution of the calling males was highly skewed and occurred in large, well‐connected ponds. Despite this, breeding ponds were not aggregated; pond size was the single factor explaining the distribution of breeding ponds. Juvenile frogs dispersed from breeding ponds and were not associated with a specific pond characteristic. Less breeding occurred in the second season during which fewer ponds were used for breeding including many different ponds from the previous year. These changes suggest that breeding effort and breeding pond choice are dynamic and therefore knowledge of the factors that drive breeding events will be a powerful tool in managing species, particularly in light of changing climatic regimes.     

Site-specific mate-finding strategies and oviposition behavior inCrocothemis erythraea (Brullé) (Odonata: Libellulidae)

Mate-finding strategies and adaptations in pre- and postcopulatory behaviors to avoid male disturbance were studied in Crocothemis erythraea at two different sites. At ponds without perch sites males patrolled with temporal partitioning of the limited oviposition sites and male-male disputes were rare. The arrival rate of females was high. At temporary marshes with dense emergent vegetation the oviposition sites were widely distributed. Males mainly perched and interacted with longer disputes. At both types of habitats with high male densities females showed a similar number of copulations per visit and oviposition durations. Postcopulatory behavior to avoid male disturbance and to decrease remating of the female differed in both sexes. At the ponds with patrolling males the probability of remating in guarded and unguarded ovipositions was similar and higher than at the marshes. At the marshes 78% of rematings occurred when the guarding male was still involved in disputes with the previously disturbing male. At the ponds females hovered before escaping successfully from approaching males and they changed to another oviposition site where they continued oviposition. Females at the marshes remated after surprise attacks by neighboring males.     

Sex roles and mutual mate choice matter during mate sampling

The roles of females and males in mating competition and mate choice have lately proven more variable, between and within species, than previously thought. In nature, mating competition occurs during mate search and is expected to be regulated by the numbers of potential mates and same-sex competitors. Here, we present the first study to test how a temporal change in sex roles affects mating competition and mate choice during mate sampling. Our model system (the marine fish Gobiusculus flavescens) is uniquely suitable because of its change in sex roles, from conventional to reversed, over the breeding season. As predicted from sex role theory, courtship was typically initiated by males and terminated by females early in the breeding season. The opposite pattern was observed late in the season, at which time several females often simultaneously courted the same male. Mate-searching females visited more males early than late in the breeding season. Our study shows that mutual mate choice and mating competition can have profound effects on female and male behavior. Future work needs to consider the dynamic nature of mating competition and mate choice if we aim to fully understand sexual selection in the wild.