Selective Forces Research Articles

Ontogenetic morphometry of the brown smoothhound shark Mustelus henlei with implications for ecology and evolution.

The central tenet of ecomorphology links ecological and morphological variation through the process of selection. Traditionally used to rationalise morphological differences between taxa, an ecomorphological approach is increasingly being utilised to study morphological differences expressed through ontogeny. Elasmobranchii (sharks, rays and skates) is one clade in which such ontogenetic shifts in body form have been reported. Such studies are limited to a relatively small proportion of total elasmobranch ecological and morphological diversity, and questions remain regarding the extent to which ecological selection are driving observed morphometric trends. In this study, we report ontogenetic growth trajectories obtained via traditional linear morphometrics from a large data set of the brown smoothhound shark (Mustelus henlei). We consider various morphological structures including the caudal, dorsal and pectoral fins, as well as several girth measurements. We use an ecomorphological approach to infer the broad ecological characteristics of this population and refine understanding of the selective forces underlying the evolution of specific morphological structures. We suggest that observed scaling trends in M. henlei are inconsistent with migratory behaviour, but do not contradict a putative trophic niche shift. We also highlight the role of predation pressure and sex-based ecological differences in driving observed trends in morphometry, a factor which has previously been neglected when considering the evolution of body form in sharks.

There is an obstetrical dilemma: Misconceptions about the evolution of human childbirth and pelvic form.

Compared to other primates, modern humans face high rates of maternal and neonatal morbidity and mortality during childbirth. Since the early 20th century, this "difficulty" of human parturition has prompted numerous evolutionary explanations, typically assuming antagonistic selective forces acting on maternal and fetal traits, which has been termed the "obstetrical dilemma." Recently, there has been a growing tendency among some anthropologists to question the difficulty of human childbirth and its evolutionary origin in an antagonistic selective regime. Partly, this stems from the motivation to combat increasing pathologization and overmedicalization of childbirth in industrialized countries. Some authors have argued that there is no obstetrical dilemma at all, and that the difficulty of childbirth mainly results from modern lifestyles and inappropriate and patriarchal obstetric practices. The failure of some studies to identify biomechanical and metabolic constraints on pelvic dimensions is sometimes interpreted as empirical support for discarding an obstetrical dilemma. Here we explain why these points are important but do not invalidate evolutionary explanations of human childbirth. We present robust empirical evidence and solid evolutionary theory supporting an obstetrical dilemma, yet one that is much more complex than originally conceived in the 20th century. We argue that evolutionary research does not hinder appropriate midwifery and obstetric care, nor does it promote negative views of female bodies. Understanding the evolutionary entanglement of biological and sociocultural factors underlying human childbirth can help us to understand individual variation in the risk factors of obstructed labor, and thus can contribute to more individualized maternal care.

Barriers with Valve Mechanisms Are Predicted to Protect Crops from Slug Carriers of Rat Lungworm Disease.

Angiostrongyliasis (Rat Lungworm disease) is an emerging parasitic disease caused by the ingestion of gastropods infected with the neurotropic nematode Angiostrongylus cantonensis. The reduction of crop infestation with infected slug carriers may vary widely by protection method. We explored the application of barriers with valve mechanisms, whereby selective directional forces caused a greater number of slugs to exit than enter the protected plot, leading to decreased slug population densities at a steady state. Using field data, we constructed predictive models to estimate slug population densities at a steady state in protected plots with (1) no valve effect, (2) a valve effect, (3) no valve effect with a single breach of the barrier, (4) a valve effect with a single breach of the barrier, (5) a valve effect with a constant breach of the barrier, and (6) a repelling effect. For all scenarios, plots protected using a barrier with a valve effect had consistently lower slug densities at a steady state. Our findings support the use of barriers with valve mechanisms under different conditions, and potentially in combination with other interventions to reduce the contamination of crops by slug carriers of A. cantonensis. Improving barriers extends beyond disease mitigation to economic and cultural impacts on the local farmer and consumer communities.

Human Genetic Factors as Determinants of Resistance to Malaria: A systematic Review

Introduction: Malaria is one of the strongest known forces of evolutionary selection in the recent history of the human genome, having had important implications in human adaptation and in the response to its infections. The objective of this systematic review was to provide an update on human genetics that have been described as affecting the human susceptibility to malaria around the world and particularly in Africa. Methods: Through world wide web research vectors and using PubMed and Google Scholar, we reviewed relevant original articles, review papers, short reports, and peer-reviewed papers on human genetics factors described as related to human susceptibility to malaria. Here, we reviewed the literature on human genetic polymorphisms associated with protection from Plasmodium infections and/or disease. Results: After reviewing and summarizing 140 manuscripts, we found that several factors appeared to hamper an effective control of malaria, including the complex biology of Plasmodium parasites, parasite genetic diversity, environmental factors, resistance to antimalarial drugs, and the lack of a highly effective vaccine for public health use. Although the cellular and molecular regulatory mechanisms underlying the pathogenesis of disease are still not fully understood, it is well-established that genetic determinants of the host play an important role in the outcome of infection and the severity of the disease. Conclusions: The interaction between malaria parasites and humans has led to the selection of several inherited traits conferring protection against malaria, such as hemoglobinopathies, enzymopathies, and immunogenetic variation, whilst others’ polymorphism describes susceptibility to the infection.

VITAL RATES, THEIR VARIATION AND NATURAL SELECTION: A CASE FOR AN ATLANTIC FOREST MARSUPIAL

Evolutionary theory predicts that viable wild populations confront environmental variation by maintaining the variance of the most important vital rates low, a phenomenon also known as demographic buffering. However, patterns diverging from the demographic buffering hypothesis have also been reported. Here we used Population Matrix Models to test the hypothesis of buffering in the early survival of an Atlantic Forest marsupial. We used sensitivity analyses, which allow quantifying the effects that perturbations in specific vital rates could have on the population’s growth rate. We obtained the sensitivities, elasticities, and second-order derivatives of the discrete population growth rate with respect to different vital rates for a population of the black-eared opossum ( Didelphis aurita , Marsupialia, Didelphidae) in a preserved Atlantic Forest, the state of Rio de Janeiro, Brazil. The second-order derivatives offer an insight into the selection forces occurring during the life cycle, clarifying the processes behind the common pattern of early-survival importance. We found evidence of buffering in early survival, however, in one of the cohorts, early survival displayed evidence of opposed behavior to the expected under demographic buffering, thus revealing that established life-history patterns can be quickly modified by a small change in one vital rate.

A biological invasion reduces rates of cannibalism by Japanese toad tadpoles

Biological invasions can favour rapid changes in intraspecific competitive mechanisms such as cannibalism by imposing novel evolutionary pressures. For example, cane toad (Rhinella marina) tadpoles are highly cannibalistic on eggs and hatchlings in their invasive range in Australia, but not in their native range in South America. Whether such changes in cannibalism occur in invasive populations of other amphibian species is unknown. To explore this question, we collected wild-laid egg clutches of Japanese common toads (Bufo japonicus) from native and invasive populations in Japan, and conducted laboratory experiments to examine cannibalism responses. Contrary to the Australian system, we found that invasion has been accompanied by reduced cannibalistic tendency of B. japonicus tadpoles. This reduction has occurred despite invasive-range B. japonicus eggs/hatchlings being more vulnerable than native-range B. japonicus eggs/hatchlings to cannibalism by native-range conspecific tadpoles, and to predation by native-range frog tadpoles. Our findings thus support the idea that biological invasions can generate rapid changes in rates of cannibalism, but also show that decreases as well as increases can occur. Future work could investigate the proximate cues and selective forces responsible for this rapid decrease in rates of cannibalism by tadpoles in an invasive B. japonicus population.

The impact of environmental conditions and milk type on microbial communities of wooden vats and cheeses produced therein

Wooden vats are used in the production of some traditional cheeses as the biofilms on wooden vat surfaces are known to transfer large quantities of microbes to cheese. Variability in microbial communities on wooden vats could lead to inconsistent cheese production. In the present study, the influences of environmental conditions and milk type (raw or heat-treated) on the microbial composition of vat biofilms and cheeses made in the vats were studied using amplicon sequencing of bacterial 16S rRNA and fungal internal transcribed spacer genes. Results showed that the microbial composition of biofilms was influenced by environmental conditions but not the milk type used in cheese production. The microbial composition of cheeses can be further affected by bacterial contributions from milk and the selective forces of environmental conditions. Results of this study suggest that controlling environmental conditions could maintain a more consistent microbial composition of biofilms on wooden vats and resulting cheeses. The use of wooden vats coupled with heat-treated milk at one or more stages of cheese production might be a viable approach to produce cheese with high microbial diversities and reduce risks of undesirable microbes related to food safety and quality.

Peer Effects in Productivity and Differential Growth: A Global Value-Chain Perspective

Abstract Using multinational input–output data, we analyze how the productivity of countries adjusted for participation in global value chains affects their output growth in manufacturing sectors. Based on parametric and non-parametric methods, we find that value-chain linkages are critical to the productivity–growth nexus and help to explain cross-country differences in sectoral output growth rates compared to the situation where these linkages are ignored. Our results have implications for macroeconomics, where they point to peer effects in productivity as drivers of growth, and for economic development, where they illustrate how the participation in global value chains may outweigh disadvantages in productive performance at the level of individual countries. They may also encourage future empirical tests of replicator dynamics to verify whether global value chains can explain the weak evidence of selection forces at the firm level.

Temporal dynamics of mother-offspring relationships in Bigg's killer whales: opportunities for kin-directed help by post-reproductive females.

Age-related changes in the patterns of local relatedness (kinship dynamics) can be a significant selective force shaping the evolution of life history and social behaviour. In humans and some species of toothed whales, average female relatedness increases with age, which can select for a prolonged post-reproductive lifespan in older females due to both costs of reproductive conflict and benefits of late-life helping of kin. Killer whales (Orcinus orca) provide a valuable system for exploring social dynamics related to such costs and benefits in a mammal with an extended post-reproductive female lifespan. We use more than 40 years of demographic and association data on the mammal-eating Bigg's killer whale to quantify how mother-offspring social relationships change with offspring age and identify opportunities for late-life helping and the potential for an intergenerational reproductive conflict. Our results suggest a high degree of male philopatry and female-biased budding dispersal in Bigg's killer whales, with some variability in the dispersal rate for both sexes. These patterns of dispersal provide opportunities for late-life helping particularly between mothers and their adult sons, while partly mitigating the costs of mother-daughter reproductive conflict. Our results provide an important step towards understanding why and how menopause has evolved in Bigg's killer whales.

Speech and sexual dimorphism: the history of the issue in the light of modern theories of the origin of speech and experimental data

In this theoretical article, the authors turn to the analysis of studies explaining the origin and revealing the functions and meaning of human oral speech within the framework of an evolutionary approach. First of all, the authors are interested in the influence of sexual selection on the development of verbal skills in different age and gender groups. In this regard, the data of the history of the human life cycle are of particular interest, which indicate that the mastery of language as a tool for influencing and manipulating the opinions of others approaches an advanced level of proficiency only at the time of puberty, and speech, thus, begins to play an important role in intersex competition. Rapidly developing with the onset of puberty, the ability to performative vivid performances, to defend their position, as well as to conduct debates in public, apparently, can be guided by the forces of sexual selection, and therefore, they should manifest themselves more clearly in men than in women. It is assumed that verbal mastery can serve as a means of actively attracting attention for the purpose of self-promotion and improving the social status of the speaker. The methodological basis of our work was largely the analysis of ethnographic sources. In the article, the authors cite extensive ethnographic material confirming the connection of high social status with oratorical abilities. The authors also turn to the latest research that analyzes the differences in performative speech between men and women. Experimental work shows that in a conversation with an attractive woman, men tend to be more creative in choosing words and expressions. Some researches consider the connection of various aspects of speech with the attractiveness of the speaker, his masculinity and adaptability. Of great interest are studies studying the relationship between musical abilities and attractiveness, as well as works analyzing the articulatory features of oral speech and their connection with belonging to a certain social environment or social class. All the features of speech given in the review could most likely have been formed by the pressure of the forces of sexual selection. In this regard, the study of sexual dimorphism seems to be one of the most important directions in the research of performative speech.

Spatial distribution of ammonia oxidizers in marine sediments of the Bohai, Yellow and East China Seas

Ammonia oxidation, an essential process within the global nitrogen cycle, is mainly performed by ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). To date, the current knowledge on the biogeography of AOA and AOB in the ocean across a large geographic distance remains poorly known. In this study, the abundance, microbial composition, and diversity of AOA and AOB in marine sediments collected from the Bohai Sea, Yellow Sea, and East China Sea were characterized by employing quantitative PCR and Illumina Miseq sequencing of both archaeal and bacterial amoA genes. qPCR analysis demonstrated significantly higher abundances of archaeal amoA genes than those of bacterial amoA genes with AOA/AOB ratios varying from 1.59 to 292.88, suggesting a greater contribution of AOA to nitrification in the seas. Nitrosopumilus and Nitrosospira were the predominant clusters of AOA and AOB respectively in all sediment samples. The distribution pattern of both AOA and AOB communities revealed by PCoA (principal coordinate analysis) showed distinct geographic separation of sediment samples from the three seas. Correlation analysis indicated that ammonia (NH4+-N) and nitrate (NO3−-N) content were the main selective forces leading to the distinct biogeography of the two ammonia oxidizers in the ocean. The results are of great significance in improving our understanding of the contribution of AOA and AOB in the nitrogen transformation in the marine ecosystem and providing insights into the environmental factors that shape the assembly of aerobic ammonium oxidizers.

Tolerant macaque species are less impulsive and reactive.

Inhibitory control, the inhibition of impulsive behaviours, is believed to be key in navigating a complex social environment. Species characterised by higher social tolerance, living in more complex groups, with more diverse relationships, face higher uncertainty regarding the outcome of social interactions and, therefore, would benefit from employing more inhibitory strategies. To date, little is known about the selective forces that favour the evolution of inhibitory control. In this study, we compared inhibitory control skills in three closely related macaque species which differ in their social tolerance style. We tested 66 macaques from two institutions (Macaca mulatta, low tolerance; M. fascicularis, medium tolerance; and M. tonkeana, high tolerance) using a battery of validated inhibitory control touchscreen tasks. Higher social tolerance was associated with enhanced inhibitory control performances. More tolerant species were less impulsive and less distracted by pictures of unknown conspecifics. Interestingly, we did not find evidence that social tolerance degree was associated with performance in reversal learning. Overall, our results support the hypothesis that evolution has promoted the development of socio-cognitive skills to cope with the demands related to the complexity of the social environment.

Compositional constraints and selection forces dictate codon usage in human bocavirus

ObjectivesHuman bocavirus (HBoV), of the genus Bocaparvovirus, is a small, non-enveloped linear single-stranded DNA virus of the Parvoviridae family. The virus is known to cause severe life-threatening respiratory tract infections in pediatric patients. Considering its deleterious impacts on respiratory, gastrointestinal, and hematological health, we prompted to investigate codon usage patterns, parity, neutrality, Nc-GC3 analysis, gene expression, Intrinsic codon bias index (ICDI), Codon bias index (CBI), Relative codon deoptimization index (RCDI), Translational selection (P2), and measure independent of length and composition (MILC) to investigate the role of evolutionary constraints such as selection and mutation and molecular patterns present in HBoV. Methods805 HBoV sequences were investigated using various software and statistical tools. ResultsThe present study demonstrated the predominant governance of selection forces over mutational forces in determining codon usage. The compositional parameters were pivotal in deciding the dinucleotide occurrence and frequently used codons. Since the HBoV genomes were A-and T-nucleotide-rich, A/T ending codons and ApAdinucleotides were overrepresented. Despite the A/T richness, at the non-neutral positions of the codon, the G/C nucleotide content was found to be the highest, again underscoring the selective forces that drive a high percentage of G/C nucleotide. At the non-neutral codon positions, with an increase in GC nucleotide, codon bias also increased, while at the third position of the codon, with an increase in GC content, it was decreased. Overall, there is a low codon bias in HBoV. A total of nine A/T ending codons were overrepresented, while nineteen G/C ending codons were underrepresented. Interestingly, instead of CTG, a commonly overrepresented codon, AGA was the most overrepresented codon. AGA and CGG encoding for arginine showed average maximum and minimum RSCU values in the HBoV genome. ConclusionsThe collective inference from the neutrality plot, Nc-GC3 curve, and P2 analysis indicated the prevalence of selection force over mutation force. With that, our study offers a novel perspective on the different molecular patterns present in HBoV, and the results might be implicated in designing efficacious therapeutic modalities against HBoV.

Mutation rate, selection, andepistasis inferred from RNA virus haplotypes via neural posterior estimation.

RNA viruses are particularly notorious for their high levels of genetic diversity, which is generated through the forces of mutation and natural selection. However, disentangling these two forces is a considerable challenge, and this may lead to widely divergent estimates of viral mutation rates, as well as difficulties in inferring the fitness effects of mutations. Here, we develop, test, and apply an approach aimed at inferring the mutation rate and key parameters that govern natural selection, from haplotype sequences covering full-length genomes of an evolving virus population. Our approach employs neural posterior estimation, a computational technique that applies simulation-based inference with neural networks to jointly infer multiple model parameters. We first tested our approach on synthetic data simulated using different mutation rates and selection parameters while accounting for sequencing errors. Reassuringly, the inferred parameter estimates were accurate and unbiased. We then applied our approach to haplotype sequencing data from a serial passaging experiment with the MS2 bacteriophage, a virus that parasites Escherichia coli. We estimated that the mutation rate of this phage is around 0.2 mutations per genome per replication cycle (95% highest density interval: 0.051-0.56). We validated this finding with two different approaches based on single-locus models that gave similar estimates but with much broader posterior distributions. Furthermore, we found evidence for reciprocal sign epistasis between four strongly beneficial mutations that all reside in an RNA stem loop that controls the expression of the viral lysis protein, responsible for lysing host cells and viral egress. We surmise that there is a fine balance between over- and underexpression of lysis that leads to this pattern of epistasis. To recap, we have developed an approach for joint inference of the mutation rate and selection parameters from full haplotype data with sequencing errors and used it to reveal features governing MS2 evolution.

Convergent genomic signatures of local adaptation across a continental-scale environmental gradient.

Convergent local adaptation offers a glimpse into the role of constraint and stochasticity in adaptive evolution, in particular the extent to which similar genetic mechanisms drive adaptation to common selective forces. Here, we investigated the genomics of local adaptation in two nonsister woodpeckers that are codistributed across an entire continent and exhibit remarkably convergent patterns of geographic variation. We sequenced the genomes of 140 individuals of Downy (Dryobates pubescens) and Hairy (Dryobates villosus) woodpeckers and used a suite of genomic approaches to identify loci under selection. We showed evidence that convergent genes have been targeted by selection in response to shared environmental pressures, such as temperature and precipitation. Among candidates, we found multiple genes putatively linked to key phenotypic adaptations to climate, including differences in body size (e.g., IGFPB) and plumage (e.g., MREG). These results are consistent with genetic constraints limiting the pathways of adaptation to broad climatic gradients, even after genetic backgrounds diverge.

Cumulative early-life adversity does not predict reduced adult longevity in wild gorillas

Extensive research across fields has repeatedly confirmed that early-life adversity (ELA) is a major selective force for many taxa, in part via its ties to adult health and longevity.1,2,3 Negative effects of ELA on adult outcomes have been documented in a wide range of species, from fish to birds to humans.4 We used 55 years of long-term data collected on 253 wild mountain gorillas to examine the effects of six putative sources of ELA on survival, both individually and cumulatively. Although cumulative ELA was associated with high mortality in early life, we found no evidence that it had detrimental consequences for survival later in life. Experiencing three or more forms of ELA was associated with greater longevity, with a 70% reduction in the risk of death across adulthood, driven specifically by greater longevity in males. Although this higher survival in later life is likely a consequence of sex-specific viability selection5 during early life due to the immediate mortality consequences of adverse experiences, patterns in our data also suggest that gorillas have significant resilience to ELA. Our findings demonstrate that the detrimental consequences of ELA on later life survival are not universal, and indeed largely absent in one of humans' closest living relatives. This raises important questions about the biological roots of sensitivity to early experiences and the protective mechanisms that contribute to resiliency in gorillas, which could be critical for understanding how best to encourage similar resiliency to early-life shocks in humans.

Evolutionary consequences of loss of sexual reproduction on male-related traits in parthenogenetic lineages of the pea aphid.

Transition from sexual reproduction to parthenogenesis constitutes a major life-history change with deep evolutionary consequences for sex-related traits, which are expected to decay. The pea aphid Acyrthosiphon pisum shows intraspecific reproductive polymorphism, with cold-resistant cyclically parthenogenetic (CP) lineages that alternate sexual and asexual generations and cold-sensitive obligately parthenogenetic (OP) lineages that produce only asexual females but still males. Here, the genotyping of 219 pea aphid lineages collected in cold-winter and mild-winter regions revealed contrasting population structures. Samples from cold-winter regions consisted mostly of distinct multilocus genotypes (MLGs) usually represented by a single sample (101 different MLGs for 111 samples) and were all phenotyped as CP. In contrast, fewer MLGs were found in mild-winter regions (28 MLGs for 108 samples), all but one being OP. Since the males produced by OP lineages are unlikely to pass on their genes (sexual females being rare in mild-winter regions), we tested the hypothesis that their traits could degenerate due to lack of selection by comparing male production and male reproductive success between OP and CP lineages. Male production was indeed reduced in OP lineages, but a less clear pattern was observed for male reproductive success: females mated with OP males laid fewer eggs (fertilized or not) but OP and CP males fertilized the same proportion of eggs. These differences may stem from the type of selective forces: male production may be counter-selected whereas male performances may evolve under the slower process of relaxed selection. The overall effective reproductive capacity of OP males could result from recent sex loss in OP lineages or underestimated reproductive opportunities.

Island and Rensch’s rules do not apply to cave vs. surface populations of Asellus aquaticus

Body size is a trait of fundamental ecological and evolutionary importance that is often different between males and females (sexual size dimorphism; SSD). The island rule predicts that small-bodied species tend to evolve larger following a release from interspecific competition and predation in insular environments. According to Rensch’s rule, male body size relative to female body size increases with increasing mean body size. This allometric body size – SSD scaling is explained by male-driven body size evolution. These ecogeographical rules are rarely tested within species, and has not been addressed in a cave–surface context, even though caves represent insular environments (small and isolated with simple communities). By analyzing six cave and nine surface populations of the widespread, primarily surface-dwelling freshwater isopod Asellus aquaticus with male-biased SSD, we tested whether cave populations evolved larger and showed higher SSD than the surface populations. We found extensive between-population variation in body size (maximum divergence being 74%) and SSD (males being 15%–50% larger than females). However, habitat type did not explain the body size and SSD variation and we could not reject isometry in the male–female body size relationship. Hence, we found no support for the island or Rensch’s rules. We conclude that local selective forces stemming from environmental factors other than island vs. mainland or the general surface vs. cave characteristics are responsible for the reported population variation.

Multimodal duetting in katydids under bat predation risk: a winning strategy for both sexes.

Duetting is a behaviour observed in some animal species, in which both males and females participate in signalling to find mates. It may have evolved as an adaptation to reduce the costs associated with mate-finding behaviours, such as predation risk. Duetting systems allow estimation of sex-specific predation risks of signalling and searching in the same species, giving insights into the selective forces acting on these behaviours. Using an acoustic-vibratory duetting katydid, Onomarchus uninotatus, and its bat predator, Megaderma spasma, we estimated the sex-specific predation costs of different mate-finding behaviours, such as walking, flying and signalling, by conducting experiments with untethered live katydids and bats. We found that acoustic-vibratory duetting benefits both the sexes as a low-risk mate-finding strategy.

Evolution of acoustic signals associated with cooperative parental behavior in a poison frog

The emergence of complex social interactions is predicted to be an important selective force in the diversification of communication systems. Parental care presents a key social context in which to study the evolution of novel signals, as care often requires communication and behavioral coordination between parents and is an evolutionary stepping-stone toward increasingly complex social systems. Anuran amphibians (frogs and toads) are a classic model of acoustic communication and the vocal repertoires of many species have been characterized in the contexts of advertisement, courtship, and aggression, yet quantitative descriptions of calls elicited in the context of parental care are lacking. The biparental poison frog, Ranitomeya imitator, exhibits a remarkable parenting behavior in which females, cued by the calls of their male partners, feed tadpoles unfertilized eggs. Here, we characterized and compared calls across three social contexts, for the first time including a parental care context. We found that egg-feeding calls share some properties with both advertisement and courtship calls but also had unique properties. Multivariate analysis revealed high classification success for advertisement and courtship calls but misclassified nearly half of egg feeding calls as either advertisement or courtship calls. Egg feeding and courtship calls both contained less identity information than advertisement calls, as expected for signals used in close-range communication where uncertainty about identity is low and additional signal modalities may be used. Taken together, egg-feeding calls likely borrowed and recombined elements of both ancestral call types to solicit a novel, context-dependent parenting response.