The more the better - polyandry and genetic similarity are positively linked to reproductive success in a natural population of terrestrial salamanders (Salamandra salamandra)

Conservation Genetics of the Loggerhead Sea Turtle, Caretta caretta, from the Central Mediterranean: An Insight into the Species' Reproductive Behaviour in Maltese Waters

Loggerhead sea turtle, Caretta caretta (Linnaeus, 1758), nestlings were investigated through specimens found dead either after hatching or unhatched (n = 120) from eight nests around the Maltese islands (Central Mediterranean). Molecular genetics was used to conduct maternity and paternity tests of the collected specimens utilizing expanded mitochondrial DNA sequences from the control region (858 bp) and 25 microsatellite loci (12 dinucleotide loci and 13 tetranucleotide loci). Mitochondrial data produced two haplotypes, CC-A2.1 and CC-A3.1, with the most common haplotype being present in seven nests. Microsatellite data revealed the identity of six different females that were involved in the deposition of the eggs in the eight turtle nests analysed. This confirms that two females laid multiple nests. Additionally, microsatellite data allowed for the determination of multiple paternity, with one clutch being sired by two fathers. These results are useful for monitoring the genetic diversity of loggerhead sea turtle nestlings and of the turtle mothers and fathers contributing to future turtle offspring, which rely on Maltese sandy beaches for their successful start to life. Effective conservation management benefits from merging scientific knowledge with effective measures at potential nesting sites to avoid losses of nestlings caused by human negligence.

Personality traits differentially affect components of reproductive success in a Neotropical poison frog

Individual reproductive success has several components, including the acquisition of mating partners, offspring production, and offspring survival until adulthood. While the effects of certain personality traits-such as boldness or aggressiveness-on single components of reproductive success are well studied, we know little about the composite and multifaceted effects behavioural traits can have on all the aspects of reproductive success. Behavioural traits positively linked to one component of reproductive success might not be beneficial for other components, and these effects may differ between sexes. We investigated the influence of boldness, aggressiveness, and exploration on the number of mating partners, mating events, and offspring surviving until adulthood in males and females of the Neotropical poison frog Allobates femoralis. Behavioural traits had different-even opposite-effects on distinct components of reproductive success in both males and females. For example, males who displayed high levels of aggressiveness and exploration (or low levels of aggressiveness and exploration) managed to attract high number of mating partners, while males with low levels of boldness, low levels of aggressiveness, and high levels of exploration had the most offspring surviving until adulthood. Our results therefore suggest correlational selection favouring particular combinations of behavioural traits.

The carboxypeptidase B and carbonic anhydrase genes play a reproductive regulatory role during multiple matings in Ophraella communa

Seminal fluid proteins (SFPs) are key factors in sexual reproduction and are transferred to females during mating with sperm. SFPs have a nutritional value because they protect and activate sperm storage and release to optimize fecundity. Multiple matings promote ovipositioning in several insect species. Therefore, insects may obtain more SFP through multiple matings to maximize reproduction, but this process has not yet been clearly confirmed. Here, the relationship between multiple matings and the SFPs in Ophraella communa (Coleoptera: Chrysomelidae), a biological control agent of the common ragweed Ambrosia artemisiifolia (Asterales: Asteraceae), was studied. Multiple matings significantly increased female fecundity and ovary egg deposition. Carboxypeptidase B (OcCpb) and carbonic anhydrase (OcCa) genes were identified as putative SFP genes in O. communa and they showed strong male-biased expression. Additionally, OcCpb and OcCa expression was upregulated in the bursa copulatrix of mating females compared to that in virgin females, but their expression gradually declined after copulation. Furthermore, OcCpb and OcCa knockdown in males led to a decrease in insect fecundity compared to that in the control. The reproductive tract of females mated with dsRNA-treated males was dissected and observed and, notably, the ovaries produced significantly fewer eggs. These data suggest that OcCpb and OcCa play regulatory roles during multiple matings in O. communa.

Mating-Induced Common and Sex-Specific Behavioral, Transcriptional Changes in the Moth Fall Armyworm (Spodoptera frugiperda, Noctuidae, Lepidoptera) in Laboratory

The intermediate process between mating and postmating behavioral changes in insects is still poorly known. Here, we studied mating-induced common and sex-specific behavioral and transcriptional changes in both sexes of Spodoptera frugiperda and tested whether the transcriptional changes are linked to postmating behavioral changes in each sex. A behavioral study showed that mating caused a temporary suppression of female calling and male courting behavior, and females did not lay eggs until the next day after the first mating. The significant differences on daily fecundity under the presence of males or not, and the same or novel males, suggest that females may intentionally retain eggs to be fertilized by novel males or to be fertilized competitively by different males. RNA sequencing in females revealed that there are more reproduction related GO (gene ontology) terms and KEGG (Kyoto encyclopedia of genes and genomes) pathways (mainly related to egg and zygote development) enriched to upregulated DEGs (differentially expressed genes) than to downregulated DEGs at 0 and 24 h postmating. In males, however, mating induced DEGs did not enrich any reproduction related terms/pathways, which may be because male reproductive bioinformatics is relatively limited in moths. Mating also induced upregulation on soma maintenance (such as immune activity and stress reaction) related processes in females at 0, 6 and 24 h postmating. In males, mating also induced upregulation on soma maintenance related processes at 0 h postmating, but induced downregulation on these processes at 6 and 24 h postmating. In conclusion, this study demonstrated that mating induced sex-specific postmating behavioral and transcriptional changes in both sexes of S. frugiperda and suggested that the transcriptional changes are correlated with postmating physiological and behavioral changes in each sex.

Do female amphibians and reptiles have greater reproductive output if they have more mates?

Abstract

In general, males mate with multiple females to increase individual reproductive success. Whether or not, and under what circumstances, females benefit from multiple mating has been less clear. Our review of 154 studies covering 184 populations of amphibians and reptiles showed that polyandry was widespread and variable among and within taxonomic groups. We investigated whether amphibian and reptile females had greater reproductive output as the number of sires for offspring increased. Meta-analysis revealed significant heterogeneity in the dataset of all taxa. Expected heterozygosity was a significant moderator (covariate) of positive relationships between female reproductive output and the number of sires, but a sensitivity test showed the result was tenuous. Significant heterogeneity remained despite controlling for expected heterozygosity and other variables but was resolved for most taxonomic groups with subgroup meta-analyses. Subgroup meta-analyses showed that only female salamanders (Caudata) had significantly greater reproductive output with an increased number of sires. For many species of Caudata, males cannot coerce females into accepting spermatophores. We therefore suggest that if females control the number of matings, they can use polyandry to increase their fitness. Caudata offers ideal models with which to test this hypothesis and to explore factors enabling and maintaining the evolution of female choice. Outstanding problems may be addressed by expanding taxonomic coverage and data collection and improving data reporting.

Significance Statement

Many factors and combinations of factors drive polyandry. Whether or not females benefit from mating with more than one male remains equivocal. Focusing on amphibians and reptiles, our analyses demonstrate that female salamanders produced more offspring when mated with multiple males, whereas this was not the case for reptiles. Unlike many other species in our dataset, the polyandrous female salamanders fully control sperm intake and have chosen to mate multiple times. We further highlight problems and key directions for future research in the field.

Multiple paternity in the pueriparous North African fire salamander, Salamandra algira, supports polyandry as a successful mating strategy in low fecundity Salamandra lineages

Multiple paternity is widespread in nature and despite costs, it has many associated benefits like increased genetic diversity and fertilization success. It has been described in many viviparous systems, suggesting the existence of some fitness advantages counteracting the inherent costs of viviparity, such as fecundity reduction and high parental investment. Reproductively polymorphic species, like the urodele Salamandra algira, which shows two types of viviparity: larviparity (i.e., delivering aquatic larvae), and pueriparity (i.e., delivering terrestrial metamorphosed juveniles), are suitable systems to study the relationship between reproductive modes and polygamous mating. Here, multiple paternity is confirmed in a pueriparous lineage of S. algira, as previously verified for the pueriparous lineages of the reproductively polymorphic species S. salamandra, suggesting polyandry is a successful mating strategy in pueriparous systems with reduced brood sizes. We discuss the potential benefits of polyandry in the context of viviparity evolution in urodeles.

Demography and spatial activity of fire salamanders, Salamandra salamandra (Linnaeus, 1758), in two contrasting habitats in the Vienna Woods

Understanding population dynamics is vital in amphibian conservation. To compare demography and movements, we conducted a capture-recapture study over three spring seasons in two populations of Salamandra salamandra in the Vienna Woods. The study sites differ in topography, vegetation, and the type of breeding waters. Population density in a beech forest traversed by a stream was more than twice as high as in an oak-hornbeam forest with temporary pools. Movement distances were on average higher at the latter site whereas home range estimates were similar for both sites. The sexes did not differ significantly in the observed movement patterns at either site. Annual apparent survival was mostly high (~0.85), but the estimate for females from the low-density site was lower (~0.60), indicating a higher rate of emigration or mortality.

The evolution of pueriparity maintains multiple paternity in a polymorphic viviparous salamander

The reduction in fecundity associated with the evolution of viviparity may have far-reaching implications for the ecology, demography, and evolution of populations. The evolution of a polygamous behaviour (e.g. polyandry) may counteract some of the effects underlying a lower fecundity, such as the reduction in genetic diversity. Comparing patterns of multiple paternity between reproductive modes allows us to understand how viviparity accounts for the trade-off between offspring quality and quantity. We analysed genetic patterns of paternity and offspring genetic diversity across 42 families from two modes of viviparity in a reproductive polymorphic species, Salamandra salamandra. This species shows an ancestral (larviparity: large clutches of free aquatic larvae), and a derived reproductive mode (pueriparity: smaller clutches of larger terrestrial juveniles). Our results confirm the existence of multiple paternity in pueriparous salamanders. Furthermore, we show the evolution of pueriparity maintains, and even increases, the occurrence of multiple paternity and the number of sires compared to larviparity, though we did not find a clear effect on genetic diversity. High incidence of multiple paternity in pueriparous populations might arise as a mechanism to avoid fertilization failures and to ensure reproductive success, and thus has important implications in highly isolated populations with small broods.

'Mainland-island' population structure of a terrestrial salamander in a forest-bocage landscape with little evidence for in situ ecological speciation

Adaptation to different ecological environments can, through divergent selection, generate phenotypic and genetic differences between populations, and eventually give rise to new species. The fire salamander (Salamandra salamandra) has been proposed to represent an early stage of ecological speciation, driven by differential habitat adaptation through the deposition and development of larvae in streams versus ponds in the Kottenforst near Bonn (Germany). We set out to test this hypothesis of ecological speciation in an area different from the one where it was raised and we took the opportunity to explore for drivers of genetic differentiation at a landscape scale. A survey over 640 localities demonstrated the species' presence in ponds and streams across forests, hilly terrain and areas with hedgerows ('bocage'). Genetic variation at 14 microsatellite loci across 41 localities in and around two small deciduous forests showed that salamander effective population sizes were higher in forests than in the bocage, with panmixia in the forests (Fst < 0.010) versus genetic drift or founder effects in several of the small and more or less isolated bocage populations (Fst > 0.025). The system fits the 'mainland-island' metapopulation model rather than indicating adaptive genetic divergence in pond versus stream larval habitats. A reanalysis of the Kottenforst data indicated that microsatellite genetic variation fitted a geographical rather than an environmental axis, with a sharp transition from a western pond-breeding to an eastern, more frequently stream-breeding group of populations. A parallel changeover in mitochondrial DNA exists but remains to be well documented. The data support the existence of a hybrid zone following secondary contact of differentiated lineages, more so than speciation in situ.

Post-epizootic salamander persistence in a disease-free refugium suggests poor dispersal ability of Batrachochytrium salamandrivorans

Lack of disease spill-over between adjacent populations has been associated with habitat fragmentation and the absence of population connectivity. We here present a case which describes the absence of the spill-over of the chytrid fungus Batrachochytrium salamandrivorans (Bsal) between two connected subpopulations of fire salamanders (Salamandra salamandra). Based on neutrally evolving microsatellite loci, both subpopulations were shown to form a single genetic cluster, suggesting a shared origin and/or recent gene flow. Alpine newts (Ichthyosaura alpestris) and fire salamanders were found in the landscape matrix between the two sites, which are also connected by a stream and separated by no obvious physical barriers. Performing a laboratory trial using alpine newts, we confirmed that Bsal is unable to disperse autonomously. Vector-mediated dispersal may have been impeded by a combination of sub-optimal connectivity, limited dispersal ability of infected hosts and a lack of suitable dispersers following the rapid, Bsal-driven collapse of susceptible hosts at the source site. Although the exact cause remains unclear, the aggregate evidence suggests that Bsal may be a poorer disperser than previously hypothesized. The lack of Bsal dispersal between neighbouring salamander populations opens perspectives for disease management and stresses the necessity of implementing biosecurity measures preventing human-mediated spread.

Evolution of male and female choice in polyandrous systems

We study the evolution of male and female mating strategies and mate choice for female fecundity and male fertilization ability in a system where both sexes can mate with multiple partners, and where there is variation in individual quality (i.e. in the availability of resources individuals can allocate to matings, mate choice and production of gametes). We find that when the cost of mating differs between sexes, the sex with higher cost of mating is reluctant to accept matings and is often also choosy, while the other sex accepts all matings. With equal mating costs, the evolution of mating strategies depends on the strength of female sperm limitation, so that when sperm limitation is strong, males are often reluctant and choosy, whereas females tend to accept available matings. Male reluctance evolves because a male's benefit per mating diminishes rapidly as he mates too often, hence losing out in the process of sperm competition as he spends much of his resources on mating costs rather than ejaculate production. When sperm limitation is weaker, females become more reluctant and males are more eager to mate. The model thus suggests that reversed sex roles are plausible outcomes of polyandry and limited sperm production. Implications for empirical studies of mate choice are discussed.

A Review of Patterns of Multiple Paternity Across Sea Turtle Rookeries

Why females would mate with multiple partners and have multiple fathers for clutches or litters is a long-standing enigma. There is a broad dichotomy in hypotheses ranging from polyandry having benefits to simply being an unavoidable consequence of a high incidence of male-female encounters. If females simply give in to mating when it is too costly to avoid being harassed by males (convenience polyandry), then there should be a higher rate of mating as density increases. However, if females actively seek males because they benefit from multiple mating, then mating frequency, and consequently the incidence of multiple paternity of clutches, should be high throughout. To explore these competing explanations, here we review the incidence of multiple paternity for sea turtles nesting around the World. Across 30 rookeries, including all 7 species of sea turtle, the incidence of multiple paternity was only weakly linked to rookery size (r²=0.14). However, using high resolution at-sea GPS tracking we show that the specifics of movement patterns play a key role in driving packing density and hence the likely rate of male-female encounters. When individuals use the same focal areas, packing density could be 100× greater than when assuming individuals move independently. Once the extent of adult movements in the breeding season was considered so that movements and abundance could be combined to produce a measure of density, then across rookeries we found a very tight relationship (r²=0.96) between packing density and the incidence of multiple paternity. These findings suggest that multiple paternity in sea turtles may have no benefit, but is simply a consequence of the incidence of male-female encounters.

Differentiation of movement behaviour in an adaptively diverging salamander population

Dispersal is considered to be a species-specific trait, but intraspecific variation can be high. However, when and how this complex trait starts to differentiate during the divergence of species/lineages is unknown. Here, we studied the differentiation of movement behaviour in a large salamander population (Salamandra salamandra), in which individual adaptations to different habitat conditions drive the genetic divergence of this population into two subpopulations. In this system, salamanders have adapted to the deposition and development of their larvae in ephemeral ponds vs. small first-order streams. In general, the pond habitat is characterized as a spatially and temporally highly unpredictable habitat, while streams provide more stable and predictable conditions for the development of larvae. We analysed the fine-scale genetic distribution of larvae, and explored whether the adaptation to different larval habitat conditions has in turn also affected dispersal strategies and home range size of adult salamanders. Based on the genetic assignment of adult individuals to their respective larval habitat type, we show that pond-adapted salamanders occupied larger home ranges, displayed long-distance dispersal and had a higher variability of movement types than the stream-adapted individuals. We argue that the differentiation of phenotypically plastic traits such as dispersal and movement characteristics can be a crucial component in the course of adaptation to new habitat conditions, thereby promoting the genetic divergence of populations.

Parallel habitat acclimatization is realized by the expression of different genes in two closely related salamander species (genus Salamandra)

The utilization of similar habitats by different species provides an ideal opportunity to identify genes underlying adaptation and acclimatization. Here, we analysed the gene expression of two closely related salamander species: Salamandra salamandra in Central Europe and Salamandra infraimmaculata in the Near East. These species inhabit similar habitat types: 'temporary ponds' and 'permanent streams' during larval development. We developed two species-specific gene expression microarrays, each targeting over 12 000 transcripts, including an overlapping subset of 8331 orthologues. Gene expression was examined for systematic differences between temporary ponds and permanent streams in larvae from both salamander species to establish gene sets and functions associated with these two habitat types. Only 20 orthologues were associated with a habitat in both species, but these orthologues did not show parallel expression patterns across species more than expected by chance. Functional annotation of a set of 106 genes with the highest effect size for a habitat suggested four putative gene function categories associated with a habitat in both species: cell proliferation, neural development, oxygen responses and muscle capacity. Among these high effect size genes was a single orthologue (14-3-3 protein zeta/YWHAZ) that was downregulated in temporary ponds in both species. The emergence of four gene function categories combined with a lack of parallel expression of orthologues (except 14-3-3 protein zeta) suggests that parallel habitat adaptation or acclimatization by larvae from S. salamandra and S. infraimmaculata to temporary ponds and permanent streams is mainly realized by different genes with a converging functionality.

Cutaneous Bacterial Communities of a Poisonous Salamander: a Perspective from Life Stages, Body Parts and Environmental Conditions

Amphibian skin provides a habitat for bacterial communities in its mucus. Understanding the structure and function of this "mucosome" in the European fire salamander (Salamandra salamandra) is critical in the context of novel emerging pathogenic diseases. We compare the cutaneous bacterial communities of this species using amplicon-based sequencing of the 16S rRNA V4 region. Across 290 samples, over 4000 OTUs were identified, four of them consistently present in all samples. Larvae and post-metamorphs exhibited distinct cutaneous microbial communities. In adults, the parotoid gland surface had a community structure different from the head, dorsum, flanks and ventral side. Larvae from streams had higher phylogenetic diversity than those found in ponds. Their bacterial community structure also differed; species of Burkholderiaceae, Comamonadaceae, Methylophilaceae and Sphingomonadaceae were more abundant in pond larvae, possibly related to differences in factors like desiccation and decomposition rate in this environment. The observed differences in the cutaneous bacterial community among stages, body parts and habitats of fire salamanders suggest that both host and external factors shape these microbiota. We hypothesize that the variation in cutaneous bacterial communities might contribute to variation in pathogen susceptibility among individual salamanders.

No signs of inbreeding despite long-term isolation and habitat fragmentation in the critically endangered Montseny brook newt (Calotriton arnoldi)

Endemic species with restricted geographic ranges potentially suffer the highest risk of extinction. If these species are further fragmented into genetically isolated subpopulations, the risk of extinction is elevated. Habitat fragmentation is generally considered to have negative effects on species survival, despite some evidence for neutral or even positive effects. Typically, non-negative effects are ignored by conservation biology. The Montseny brook newt (Calotriton arnoldi) has one of the smallest distribution ranges of any European amphibian (8 km²) and is considered critically endangered by the International Union for Conservation of Nature. Here we apply molecular markers to analyze its population structure and find that habitat fragmentation owing to a natural barrier has resulted in strong genetic division of populations into two sectors, with no detectable migration between sites. Although effective population size estimates suggest low values for all populations, we found low levels of inbreeding and relatedness between individuals within populations. Moreover, C. arnoldi displays similar levels of genetic diversity to its sister species Calotriton asper, from which it separated around 1.5 million years ago and which has a much larger distribution range. Our extensive study shows that natural habitat fragmentation does not result in negative genetic effects, such as the loss of genetic diversity and inbreeding on an evolutionary timescale. We hypothesize that species in such conditions may evolve strategies (for example, special mating preferences) to mitigate the effects of small population sizes. However, it should be stressed that the influence of natural habitat fragmentation on an evolutionary timescale should not be conflated with anthropogenic habitat loss or degradation when considering conservation strategies.

Amphibian gut microbiota shifts differentially in community structure but converges on habitat-specific predicted functions

Complex microbial communities inhabit vertebrate digestive systems but thorough understanding of the ecological dynamics and functions of host-associated microbiota within natural habitats is limited. We investigate the role of environmental conditions in shaping gut and skin microbiota under natural conditions by performing a field survey and reciprocal transfer experiments with salamander larvae inhabiting two distinct habitats (ponds and streams). We show that gut and skin microbiota are habitat-specific, demonstrating environmental factors mediate community structure. Reciprocal transfer reveals that gut microbiota, but not skin microbiota, responds differentially to environmental change. Stream-to-pond larvae shift their gut microbiota to that of pond-to-pond larvae, whereas pond-to-stream larvae change to a community structure distinct from both habitat controls. Predicted functions, however, match that of larvae from the destination habitats in both cases. Thus, microbial function can be matched without taxonomic coherence and gut microbiota appears to exhibit metagenomic plasticity.

Host-associated microbial communities can shift in structure or function when hosts change locations. Bletz et al. reciprocally transfer salamander larvae between pond and stream habitats to show that gut microbiomes shift in function, but not necessarily taxonomic identities, when hosts encounter a new environment.

Multiple paternity in a viviparous toad with internal fertilisation

Anurans are renowned for a high diversity of reproductive modes, but less than 1 % of species exhibit internal fertilisation followed by viviparity. In the live-bearing West African Nimba toad (Nimbaphrynoides occidentalis), females produce yolk-poor eggs and internally nourish their young after fertilisation. Birth of fully developed juveniles takes place after 9 months. In the present study, we used genetic markers (eight microsatellite loci) to assign the paternity of litters of 12 females comprising on average 9.7 juveniles. In 9 out of 12 families (75 %), a single sire was sufficient; in three families (25 %), more than one sire was necessary to explain the observed genotypes in each family. These findings are backed up with field observations of male resource defence (underground cavities in which mating takes place) as well as coercive mating attempts, suggesting that the observed moderate level of multiple paternity in a species without distinct sperm storage organs is governed by a balance of female mate choice and male reproductive strategies.

Influences of population density on polyandry and patterns of sperm usage in the marine gastropod Rapana venosa

Polyandry is a common mating strategy in animals, with potential for sexual selection to continue post-copulation through sperm competition and/or cryptic female choice. Few studies have investigated the influences of population density on polyandry and sperm usage, and paternity distribution in successive broods of marine invertebrates. The marine gastropod Rapana venosa is ideal for investigating how population density influences the frequency of polyandry and elucidating patterns of sperm usage. Two different population density (12 ind/m³ and 36 ind/m³) treatments with two replications were set to observe reproductive behaviors. Five microsatellite markers were used to identify the frequency of multiple paternity and determine paternal contributions to progeny arrays in 120 egg masses. All of the mean mating frequency, mean number of sires and mean egg-laying frequency were higher at high population density treatment relative to low population density treatment, indicating population density is an important factor affecting polyandry. The last sperm donors achieved high proportions of paternity in 74.77% of egg masses, which supported the “last male sperm precedence” hypothesis. In addition, high variance in reproductive success among R. venosa males were detected, which might have an important influence on effective population size.

Genetic structure of the fire salamander Salamandra salamandra in the Polish Sudetes

We analysed genetic variation within and differentiation between nineteen populations of the fire salamander Salamandra salamandra inhabiting the north-eastern margin of the species range in the Sudetes Mountains (south-western Poland). The results were compared with those obtained recently for the Polish part of the Carpathians. Variation of 10 nuclear microsatellite loci was analysed in 744 individuals to estimate genetic structure, gene flow, isolation and to test for a geographic gradient of genetic variation. Mitochondrial DNA control region (D-loop) of 252 specimens from all localities was used to identify the origin of populations currently inhabiting its north-eastern range. We found little genetic differentiation among populations in the Sudetes indicating substantial recent or ongoing gene flow. The exceptions were one isolated peripheral population located outside the continuous distribution range which displayed extremely reduced genetic variation probably due to a combination of long term isolation and low population size, and one population located at the eastern margin of the Polish Sudetes. Populations inhabiting the Sudetes and the Carpathians formed two separate clusters based on microsatellite loci. In accordance with available phylogeographic information, single mitochondrial haplotype (type IIb) fixed in all populations indicates their origin from a single refugium and may suggest colonization from the Balkan Peninsula. The analysis of geographic gradient in variation showed its decline in the westerly direction suggesting colonization of Poland from the east, however, alternative scenarios of postglacial colonization could not be rejected with the available data.

Long-term consequences of early nutritional conditions on the behaviour and growth of fire salamanders

Early developmental conditions can have a strong influence on the life history. Fire salamanders represent an interesting system due to their biphasic life cycle consisting of an aquatic larval stage and a subsequent terrestrial stage. The environment experienced as larvae affects growth, age at metamorphosis and behaviour. In particular, diet restrictions can cause developmental stress. However, the impact of such developmental stress on the growth and behaviour in a long-lived amphibian are not yet well studied. We manipulated the early diet of sibling pairs of fire salamander larvae. One sibling was raised under food-restriction and the other was raised under conditions of abundant food. We report long-term effects on growth and exploratory behaviour; exploratory behaviour was tested in two sessions, first as young juveniles and later as sub-adults. We found that food-restricted conditions during early development affected exploratory behaviour. Early deficits in body mass and body size were compensated later in life, by approximately 18 months of age. When morphological differences were compensated, the initial differences in exploratory behaviour also disappeared. Thus, compensation not only led to an alignment of body parameters but was also accompanied by an adjustment in exploratory behaviour. No cost of compensation was detected, but future research will need to verify whether the potential costs of compensation are negligible in slow-growing salamanders or whether they are shifted to later life stages. Our study provides novel insights into the life history of fire salamanders and reveals that early larval conditions have effects on individuals long after metamorphosis.

Inter-annual weather variability can drive the outcome of predator prey match in ponds

The matching of life-history-events to the availability of prey is essential for the growth and development of predators. Mismatches can constrain individuals to complete life-cycle steps in time and in ephemeral habitats it can lead to mortality unless compensation mechanisms exist. Here we measured the performance of a population of European fire-salamanders (Salamandra salamandra) and their prey in ephemeral ponds. We analysed how short time inter-annual variability of yearly rainfall and temperature (two consecutive years, 2011 and 2012) affects matching of predator and prey and how two different weather scenarios influenced the predator’s population structure. A single species (larvae of the mosquito Aedes vexans) dominates the prey community here, which occurs in high quantities only in the beginning of the season. When the occurrence of prey and predator matched during a period of sufficiently high temperatures (as in 2011), initial growth of the salamander larvae was high and population size development homogeneous. At low temperatures during matching of predatory and prey (as in 2012), the initial growth was low but the salamander larvae developed into two distinctly different sizes. Further, some individuals in the large cohort became cannibalistic and initial size differences increased. As a result, the latest (smallest) cohort disappeared completely. Temperature measurements and estimation of maximal growth rates revealed that temperature differences alone could explain the different early development between years. Our data show that weather conditions (rainfall; temperature during early growth phase) strongly determined the performance of salamander larvae in ponds. Our data also add to the match-mismatch concept that abiotic growth conditions (here: low temperature) could prevent efficient conversion of prey- into predator-biomass despite high prey availability.

Female and male moths display different reproductive behavior when facing new versus previous mates

Multiple mating allows females to obtain material (more sperm and nutrient) and/or genetic benefits. The genetic benefit models require sperm from different males to fertilize eggs competitively or the offspring be fathered by multiple males. To maximize genetic benefits from multiple mating, females have evolved strategies to prefer novel versus previous mates in their subsequent matings. However, the reproductive behavior during mate encounter, mate choice and egg laying in relation to discrimination and preference between sexes has been largely neglected. In the present study, we used novel and previous mate treatments and studied male and female behavior and reproductive output in Spodoptera litura. The results of this study do not support the sperm and nutrient replenishment hypotheses because neither the number of mates nor the number of copulations achieved by females significantly increased female fecundity, fertility and longevity. However, females showed different oviposition patterns when facing new versus previous mates by slowing down oviposition, which allows the last male has opportunities to fertilize her eggs and the female to promote offspring diversity. Moreover, females that have novel males present called earlier and more than females that have their previous mates present, whereas no significant differences were found on male courtship between treatments. These results suggest that S. litura females can distinguish novel from previous mates and prefer the former, whereas males generally remate regardless of whether the female is a previous mate or not. In S. litura, eggs are laid in large clusters and offspring competition, inbreeding and disease transfer risks are thus increased. Therefore, offspring diversity should be valuable for S. litura, and genetic benefits should be the main force behind the evolution of female behavioral strategies found in the present study.

Condition-dependent mate choice: A stochastic dynamic programming approach

We study how changing female condition during the mating season and condition-dependent search costs impact female mate choice, and what strategies a female could employ in choosing mates to maximize her own fitness. We address this problem via a stochastic dynamic programming model of mate choice. In the model, a female encounters males sequentially and must choose whether to mate or continue searching. As the female searches, her own condition changes stochastically, and she incurs condition-dependent search costs. The female attempts to maximize the quality of the offspring, which is a function of the female's condition at mating and the quality of the male with whom she mates. The mating strategy that maximizes the female's net expected reward is a quality threshold. We compare the optimal policy with other well-known mate choice strategies, and we use simulations to examine how well the optimal policy fares under imperfect information.