Hermaphroditic individuals can produce both selfed and outcrossed progeny, termed mixed mating. General theory predicts that mixed-mating populations should evolve quickly toward high rates of ...setting, driven by rapid purging of genetic load and loss of inbreeding depression (ID), but the substantial number of mixed-mating species observed in nature calls this prediction into question. Lower average ID reported for selfing than for outcrossing populations is consistent with purging and suggests that mixed-mating taxa in evolutionary transition will have intermediate ID. We compared the magnitude of ID from published estimates for highly selfing (r > 0.8), mixed-mating (0.2 ≤ r ≥ 0.8), and highly outcrossing (r < 0.2) plant populations across 58 species. We found that mixed-mating and outcrossing taxa have equally high average lifetime ID (δ = 0.58 and 0.54, respectively) and similar ID at each of four life-cycle stages. These results are not consistent with evolution toward selfing in most mixed-mating taxa. We suggest that prevention of purging by selective interference could explain stable mixed mating in many natural populations. We identify critical gaps in the empirical data on ID and outline key approaches to filling them.
Most flowering plants are hermaphroditic, yet the proportion of seeds fertilized by self and outcross pollen varies widely among species, ranging from predominant self-fertilization to exclusive ...outcrossing. A population's rate of outcrossing has important evolutionary outcomes as it influences genetic structure, effective population size, and offspring fitness. Because most mating system studies have quantified outcrossing rates for just one or two populations, past reviews of mating system diversity have not been able to characterize the extent of variation among populations. Here we present a new database of more than 30 years of mating system studies that report outcrossing rates for three or more populations per species. This survey, which includes 741 populations from 105 species, illustrates substantial and prevalent among-population variation in the mating system. Intermediate outcrossing rates (mixed mating) are common; 63% of species had at least one mixed mating population. The variance among populations and within species was not significantly correlated with pollination mode or phylogeny. Our review underscores the need for studies exploring variation in the relative influence of ecological and genetic factors on the mating system, and how this varies among populations. We conclude that estimates of outcrossing rates from single populations are often highly unreliable indicators of the mating system of an entire species.
The neurohormones oxytocin (OT) and arginine vasopressin (AVP) are involved in social behaviors and psychiatric conditions. However, more research on nonhuman primates with complex social behaviors ...is needed. We studied two closely-related primate species with divergent social and mating systems; hamadryas baboons (Papio hamadryas, n=38 individuals) and anubis baboons (Papio anubis, n=46). We measured OT in cerebrospinal fluid (CSF, n=75), plasma (n=81) and urine (n=77), and AVP in CSF (n=45), and we collected over 250 hours of focal behavioral observations. Using Bayesian multivariate models, we found no clear species difference in hormone levels; the strongest support was for hamadryas having higher CSF OT levels than anubis (posterior probability PP for females = 0.75, males = 0.84). Looking at nine specific behaviors, OT was associated with affiliative behaviors (approach, proximity, grooming, PP ∼ 0.85 – 1.00), albeit inconsistently across sources of measurement (CSF, plasma, and urine, which were uncorrelated with each other). Most behaviors had low repeatability (R ∼ 0 – 0.2), i.e. they did not exhibit stable between-individual differences (or “personality”), and different behaviors did not neatly coalesce into higher-order factors (or “behavioral syndromes”), which cautions against the use of aggregate behavioral measures and highlights the need to establish stable behavioral profiles when testing associations with baseline hormone levels. In sum, we found some associations between peptides and social behavior, but also many null results, OT levels from different sources were uncorrelated, and our behavioral measures did not indicate clear individual differences in sociability.
•No species differences in oxytocin (OT) and vasopressin (AVP) levels in baboons.•OT from cerebrospinal fluid (CSF), plasma and urine and CSF AVP uncorrelated.•CSF OT associated with some affiliative behaviors, plasma OT with others.•Weak individual differences in behavior and no clear personality structure.•Overall mixed associations rather than generalized sociability driven by OT and AVP.
Premise of Study
In a seminal body of theory, Lloyd showed that the fitness consequences of selfing will depend on its timing in anthesis. Selfing that occurs after opportunities for outcrossing or ...pollen dispersal can provide reproductive assurance when pollinators are limited and is expected to incur little cost, even when inbreeding depression is high. As a result, delayed selfing is often interpreted as a “best‐of‐both‐worlds” mating system that combines the advantages of selfing and outcrossing.
Methods
We surveyed 65 empirical studies of delayed selfing, recording floral mechanisms and examining information on inbreeding depression, autofertility, and other parameters to test the support for delayed selfing as a best‐of‐both‐worlds strategy.
Key Results
Phylogenetic distribution of the diverse floral mechanisms suggests that some basic floral structures may predispose plant taxa to evolve delayed selfing. Delayed selfing appears to serve as a best‐of‐both‐worlds strategy in some but not all species. While the capacity for autonomous selfing is often high, it is lower, in some cases, than in related species with earlier modes of selfing. In other delayed‐selfers, low inbreeding depression and reduced investment in corollas and pollen suggest limited benefits from outcrossing.
Conclusions
Despite a growing literature on the subject, experimental evidence for delayed selfing is limited and major gaps in knowledge remain, particularly with respect to the stability of delayed selfing and the conditions that may favor transitions between delayed and earlier selfing. Finally, we suggest a potential role of delayed selfing in facilitating transitions from self‐incompatibility to selfing.
Male–female coevolution has taken different paths among closely related species, but our understanding of the factors that govern its direction is limited. While it is clear that ecological factors, ...life history, and the economics of reproduction are connected, the divergent links are often obscure. We propose that a complete understanding requires the conceptual integration of metabolic phenotypes. Metabolic rate, a nexus of life history evolution, is constrained by ecological factors and may exert important direct and indirect effects on the evolution of sexual dimorphism. We performed standardized experiments in 12 seed beetle species to gain a rich set of sex-specific measures of metabolic phenotypes, life history traits, and the economics of mating and analyzed our multivariate data using phylogenetic comparative methods. Resting metabolic rate (RMR) showed extensive evolution and evolved more rapidly in males than in females. The evolution of RMR was tightly coupled with a suite of life history traits, describing a pace-of-life syndrome (POLS), with indirect effects on the economics of mating. As predicted, high resource competition was associated with a low RMR and a slow POLS. The cost of mating showed sexually antagonistic coevolution, a hallmark of sexual conflict. The sex-specific costs and benefits of mating were predictably related to ecology, primarily through the evolution of male ejaculate size. Overall, our results support the tenet that resource competition affects metabolic processes that, in turn, have predictable effects on both life history evolution and reproduction, such that ecology shows both direct and indirect effects on male–female coevolution.
Reduced allocation to structures for pollinator attraction is predicted in selfing species. We explored the association between outcrossing and floral display in a broad sample of angiosperms. We ...used the demonstrated relationship to test for bias against selfing species in the outcrossing rate distribution, the shape of which has relevance for the stability of mixed mating. Relationships between outcrossing rate, flower size, flower number and floral display, measured as the product of flower size and number, were examined using phylogenetically independent contrasts. The distribution of floral displays among species in the outcrossing rate database was compared with that of a random sample of the same flora. The outcrossing rate was positively associated with the product of flower size and number; individually, components of display were less strongly related to outcrossing. Compared with a random sample, species in the outcrossing rate database showed a deficit of small floral display sizes. We found broad support for reduced allocation to attraction in selfing species. We suggest that covariation between mating systems and total allocation to attraction can explain the deviation from expected trade-offs between flower size and number. Our results suggest a bias against estimating outcrossing rates in the lower half of the distribution, but not specifically against highly selfing species.
Extra‐pair paternity in birds Brouwer, Lyanne; Griffith, Simon C.
Molecular ecology,
November 2019, Letnik:
28, Številka:
22
Journal Article
Recenzirano
Odprti dostop
Since the first molecular study providing evidence for mating outside the pair bond in birds over 30 years ago, >500 studies have reported rates of extra‐pair paternity (EPP) in >300 bird species. ...Here, we give a detailed overview of the current literature reporting EPP in birds and highlight the sampling biases and patterns in the data set with respect to taxonomy, avian phylogeny and global regions, knowledge of which will be crucial for correct interpretation of results in future comparative studies. Subsequently, we use this comprehensive dataset to simultaneously test the role of several ecological and life history variables. We do not find clear evidence that variation in EPP across socially monogamous species can be explained by latitude, density (coloniality), migration, generation length, genetic structuring (dispersal distance), or climatic variability, after accounting for phylogeny. These results contrast previous studies, most likely due to the large heterogeneity within species in both EPP and the predictor of interest, indicating that using species averages might be unreliable. Despite the absence of broadscale ecological drivers in explaining interspecific variation in EPP, we suggest that certain behaviours and ecological variables might facilitate or constrain EPP, as indicated by our finding that EPP was negatively associated with latitude within noncolonial species, suggesting a role of breeding synchrony. Thus, rather than focussing on general explanations for variation in EPP across all species, a future focus should be on how various aspects of ecology or life history might have driven variation in EPP among groups of species or populations of the same species. Hence, we argue that variation in EPP can be partly explained when taking the right perspective. This comprehensive overview, and particularly the dataset provided herein will create a foundation for further studies.
Mixing gene pools in translocations can create populations with higher genetic diversity and evolutionary potential compared to single sources. However, the benefits of outcrossing on genetic rescue ...may depend on species' life history, notably mating systems. We assessed outcomes on growth and survival of different kinds of cross in a translocated population of the highly endangered mixed‐mating species Banksia brownii, established from multiple sources. We genetically assigned plants grown from field‐pollinated seed as of selfed, within‐source or between‐source (referring to the original source populations) cross types, and estimated proportion of heterozygous loci for each plant. We modeled the associations among genetic predictors (cross type, level of genetic diversity, and ancestry) and fitness proxies measured in glasshouse and field. At the translocation site, selfing rates were approximately 53–70% and crossing among sources was rare, both likely owing to different patterns of flowering among plants. Offspring of selfed plants were consistently smaller in volume in the glasshouse than were offspring from within‐source crosses. There was no evidence from the first 3 years that survival in the field was influenced by any predictor tested, but the smaller volume of selfed plants in the glasshouse and correlation of glasshouse size at 5 months with the size of the same plants at 3 years in the field suggest that more time may be needed to observe any effects of outcrossing on survival and fitness. Our results highlight the importance of monitoring mating systems, genetic diversity, and fitness data for evaluating translocation success and informing adaptive management.
Territory defence is widely assumed to be adaptive because it enhances reproductive success. However, empirical evidence for such a benefit is scarce or nonexistent for many types of territorial ...organisms. The roles of intraspecific aggression versus interactions with females in successful breeding by territorial males are also still poorly understood in lower tetrapods, including lizards. We address both of these important issues using 10 years of data on genetic parentage combined with field behavioural studies in collared lizards, Crotaphytus collaris. As predicted, territorial males (T-males) had more mates, sired markedly more total offspring and sired more surviving offspring with more females than did nonterritorial (NT) males. Territorial males in structurally simpler habitats sired a higher proportion of each female's offspring than their counterparts in complex habitats, indicating that the ability of T-males to accrue mating benefits is highest where topography maximizes contact with multiple females. All measures of T-male reproductive success increased with travel rate but decreased with the time spent courting individual females, suggesting a fitness trade-off between these behaviours. We found no evidence that aggressive behaviour was linked to any component of male fitness. Hence, activities of territory owners appear to be shaped by sexual selection to enhance mating opportunities rather than to aggressively dominate same-sex rivals. Our study illustrates the value of long-term research documenting behaviour and fitness of free-ranging individuals over multiple reproductive cycles in evaluating fundamental questions about the adaptive significance of social tactics.
•Territorial male collared lizards had higher fitness than nonterritorial males.•Territorial tactics increased mating more effectively in simpler habitats.•Fitness of territory owners increased with travel but not with aggressive behaviour.•Limiting courtship per female promoted travel to interact with additional mates.•Male behaviour is selected to enhance interactions with multiple female mates.
Intraspecific variability in mating systems has been documented previously, but there are few studies where investigators have used intraspecific comparisons to investigate the influence of ...ecological or demographic factors on social and genetic mating systems. We studied two populations of prairie voles,
Microtus ochrogaster, one near Lawrence, Kansas, U.S.A., and the other in Bloomington, Indiana, U.S.A. We examined differences in spatial structuring of vegetation between sites, which might contribute to intraspecific variation in social and genetic mating patterns. Since space use is often related to the mating system, we calculated home range size of a subset of adult males and females in both populations and used live trapping to examine the number of same- or opposite-sex conspecifics sharing capture locations. We applied social network analysis to live-trapping data to quantify the number and strength of social ties with opposite-sex conspecifics. Genetic parentage analysis provided an estimate of the number of mates per individual. We found that space use and overlap with members of the same and opposite sex were best explained by effects of site and sex. The relative strength of social associations with opposite-sex conspecifics was best predicted by site, density and sex. The genetic mating system was best explained by population density. Although we cannot disentangle population density from ecological variables related to site (e.g. distribution of vegetation) that may have affected social monogamy in our study populations, our study shows that extrinsic variables do affect differences in social and genetic mating systems between populations.
► We studied two populations of prairie voles to see what factors influence mating systems. ► Site and sex best explained social monogamy. ► Site, density and sex best predicted the strength of social associations. ► Density best explained the genetic mating system. ► Extrinsic variables affect intraspecific mating systems.
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