Male Mating Behavior Research Articles

Dominance rank and the presence of sexually receptive females predict feces-measured body temperature in male chimpanzees.

Quantifying the costs of mating is key for understanding life-history trade-offs. As a reflection of metabolic rate, body temperature is one metric for assaying these costs. However, conventional methods for measuring body temperature are invasive and unsuitable for the study of free-living populations of endangered species, including great apes. A promising proxy for body temperature is fecal temperature, the internal temperature of fecal deposits shortly following defecation. We validated this method with humans, finding that maximum fecal temperature is a reliable proxy for rectal temperature. We then applied this method to wild chimpanzees (Pan troglodytes schweinfurthii) at Ngogo, Kibale National Park, Uganda. We collected and analyzed 101 fecal temperature measurements from 43 adult chimpanzees (male: N = 28; female: N = 15). Chimpanzee fecal temperature ranged from 33.4 to 38.9 °C, with a mean of 35.8 °C. Although fecal temperature was not predicted by sex, age, or ambient temperature, male fecal temperature was 1.1 °C higher on days when sexually receptive females were present and was positively correlated with male dominance rank. Post hoc analyses showed that overall copulation rates, but not aggression rates, were positively correlated with fecal temperature, suggesting that sexual physiology and behavior best explain mating-related temperature variation. Together, these results indicate fecal temperature is a reliable proxy for core body temperature in large-bodied mammals, captures metabolic costs associated with male mating behavior, and represents a valuable noninvasive tool for biological field research.

Nerves innervating copulatory organs show common FMRFamide, FVRIamide, MIP and serotonin immunoreactivity patterns across Dinophilidae (Annelida) indicating their conserved role in copulatory behaviour

BackgroundMales of the microscopic annelid family Dinophilidae use their prominent glandomuscular copulatory organ (penis) to enzymatically dissolve the female’s epidermis and thereafter inject sperm. In order to test for putative conserved copulatory structures and neural orchestration across three dinophilid species, we reconstructed the reproductive myo- and neuroanatomy and mapped immunoreactivity patterns against two specific neurotransmitter markers with reported roles in invertebrate male mating behaviour (FVRIamide, MIP) and three general neural markers (acetylated α-tubulin, serotonin, FMRFamide).ResultsSeminal vesicles (one or two pairs), surrounded by a thin layer of longitudinal and circular muscles and innervated by neurites, are found between testes and copulatory organ in the larger males of Dinophilus vorticoides and Trilobodrilus axi, but are missing in the only 0.05 mm long D. gyrociliatus dwarf males. The midventral copulatory organ is in all species composed of an outer muscular penis sheath and an inner penis cone. Neurites encircle the organ equatorially, either as a ring-shaped circumpenial fibre mass or as dorsal and ventral commissures, which are connected to the ventrolateral nerve cords. All three examined dinophilids show similar immunoreactivity patterns against serotonin, FMRFamide, and FVRIamide in the neurons surrounding the penis, supporting the hypotheses about the general involvement of these neurotransmitters in copulatory behaviour in dinophilids. Immunoreactivity against MIP is restricted to the circumpenial fibre mass in D. gyrociliatus and commissures around the penis in T. axi (but not found in D. vorticoides), indicating its role in controlling the copulatory organ.ConclusionsThe overall myo- and neuroanatomy of the reproductive organs is rather similar in the three studied species, suggesting a common ancestry of the unpaired glandomuscular copulatory organ and its innervation in Dinophilidae. This is furthermore supported by the similar immunoreactivity patterns against the tested neurotransmitters around the penis. Smaller differences in the immunoreactivity patterns around the seminal vesicles and spermioducts might account for additional, individual traits. We thus show morphological support for the putatively conserved role of FMRFamide, FVRIamide, MIP and serotonin in dinophilid copulatory behaviour.

Sperm acquisition and storage dynamics facilitate sperm limitation in the selectively harvested blue crab Callinectes sapidus

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 629:87-101 (2019) - DOI: https://doi.org/10.3354/meps13104 Sperm acquisition and storage dynamics facilitate sperm limitation in the selectively harvested blue crab Callinectes sapidus Matthew B. Ogburn*, Kimberly D. Richie, Morgan A. Jones, Anson H. Hines Smithsonian Environmental Research Center, Edgewater, MD 21037, USA *Corresponding author: ogburnm@si.edu ABSTRACT: Selective harvest of male blue crabs Callinectes sapidus can reduce the operational sex ratio and alter male mating history and behaviors, reducing the quantity of sperm females acquire during mating. Females mate shortly after molting to maturity, storing sperm for at least 2 yr, and fertilize multiple broods of eggs. We combined field surveys, a mark-recapture experiment, and modeling in the most extensive study of sperm storage and use after mating in blue crabs evaluating (1) spatiotemporal patterns in sperm quantity acquired during mating, (2) the pattern and rate of decline of sperm during storage, (3) the quantity of sperm used for fertilization, and (4) the potential for sperm limitation. We also explored the spatial extent of spawning in Chesapeake Bay in comparison to the spawning sanctuary. Female crabs acquired up to 3 × 109 sperm, but sperm stores declined by 90-95% in the first 1-2 mo after mating. Sperm quantity differences between first- and second-year spawners indicated use of 4 sperm egg-1 during fertilization. Approximately 15% of spawning females were in their second spawning season, and remaining sperm stores were indicative of sperm limitation resulting in a 5-10% decrease in reproductive output of the spawning stock. The current spawning sanctuary encompassed 98% of ovigerous females and 100% of females with evidence of prior spawning. Although many females do not experience sperm limitation prior to harvest or natural mortality, reductions in the reproductive output of second-year spawners likely limits population resilience to inter-annual variation in spawning stock biomass. KEY WORDS: Sperm limitation · Population dynamics · Reproductive output · Selective harvest · Callinectes sapidus Full text in pdf format PreviousNextCite this article as: Ogburn MB, Richie KD, Jones MA, Hines AH (2019) Sperm acquisition and storage dynamics facilitate sperm limitation in the selectively harvested blue crab Callinectes sapidus. Mar Ecol Prog Ser 629:87-101. https://doi.org/10.3354/meps13104 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 629. Online publication date: October 24, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.

Sex Mysteries of the Fly Courtship Master Regulator Fruitless.

The fruitless (fru) gene of Drosophila melanogaster generates two groups of protein products, the male-specific FruM proteins and non-sex-specific FruCOM proteins. The FruM proteins have a 101 amino acids (a.a.)-long extension at the N-terminus which is absent from FruCOM. We suggest that this N-terminal extension might confer male-specific roles on FruM interaction partner proteins such as Lola, which otherwise operates as a transcription factor common to both sexes. FruM-expressing neurons are known to connect with other neurons to form a sexually dimorphic circuit for male mating behavior. We propose that FruM proteins expressed in two synaptic partners specify, at the transcriptional level, signaling pathways through which select pre- and post-synaptic partners communicate, and thereby pleiotropic ligand-receptor pairs for cell-cell interactions acquire the high specificity for mutual connections between two FruM-positive cells. We further discuss the possibility that synaptic connections made by FruM-positive neurons are regulated by neural activities, which in turn upregulate Fru expression in active cells, resulting in feedforward enhancement of courtship activities of the male fly.

Exploring the multilevel hazards of thiamethoxam using Drosophila melanogaster

Thiamethoxam (THIA) is a widely used pesticide. However, its effects on the growth and development of insects remain unclear. Herein, the lethal concentration 50 (LC50) of THIA (3.13 μg/mL for adults, 20.25 μg/mL for third-instar larvae) were identified. THIA (1/3 LC50) prolonged the time required for growth and development, and decreased the fecundity, the rates of pupation and eclosion, and lifespan of Drosophila. The uniform architecture of the compound eyes was disturbed. It also triggered DNA damage, and reduced the viability of fat body cells and hemocytes. Moreover, RNA-sequencing showed that differentially expressed genes in response to THIA were mainly related to stratum corneum development, immune function. Genes involved in stratum corneum proteins (Lcp65Ag3, Cpr65Ax1), hemocyte proliferation (RyR), and immune responses (IM4) were significantly induced. Genes associated with lipid metabolism (sxe2), lifespan (Atg7 and NalZ), pupa development (IIp8, Blimp-1), female fertility (Ddc), male mating behavior (ple), neural retina development (Nnad), was significantly downregulated. These findings provide a basis for further research to fully assess the hazards of exposure to neonicotinoid pesticides.

The male and female perspective in the link between male infant care and mating behaviour in Barbary macaques

AbstractInfant care from adult males is unexpected in species with high paternity uncertainty. Still, males of several polygynandrous primates engage in frequent affiliative interactions with infants. Two non‐exclusive hypotheses link male infant care to male mating strategies. The paternal investment hypothesis views infant care as a male strategy to maximize the survival of sired offspring, while the mating effort hypothesis predicts that females reward males who cared for their infant by preferably mating with them. Both hypotheses predict a positive relationship between infant care and matings with a particular female. However, the paternal investment hypothesis predicts that increased matings come before infant care whereas the mating effort hypothesis predicts that infant care precedes an increase in matings. Both hypotheses are usually tested from the perspective of the proportion of matings and care that individual females engage in and receive, rather than from the perspective of the care and mating behaviour of individual males. We tested the relationships between care and mating from both female and male perspectives in Barbary macaques. Mating predicted subsequent care and care predicted subsequent mating when viewed from the male but not the female perspective. Males mainly cared for infants of their main mating partners, but infants were not mainly cared for by their likely father. Males mated more with the mothers of their favourite infants, but females did not mate more with the main caretakers of their infants. We suggest that females do not choose their mating partners based on previous infant care, increasing paternity confusion. Males might try to increase paternal investment by distributing the care according to their own instead of female mating history. Further, males pursue females for mating opportunities based on previous care.

Female mice seek refuge from castrated males, but not intact or vasectomized males, mitigating a socially-induced glucocorticoid response

Sexual conflict may be manifested during social interactions, shaping the costs of reproduction in sexually reproducing species. This conflict, and the physical necessity of intromission, can intensify the already costly nature of reproduction for female mammals. To identify and partition the costs that males inflict on females during mating and reproduction, we paired female mice with either other females or castrated, vasectomised, or intact (sham-vasectomised) males, thus manipulating exposure to social mating behavior and costs arising from fertilization. We also provided females with refuges where males could not enter, to test whether females show avoidance or attraction to males of different gonadal status expected to exhibit different levels of social behavior. We found that females paired with vasectomised and castrated males spent the most time in their refuge. Females housed with castrated males also had increased glucocorticoid levels, an effect that was mitigated when females could retreat from these males to a refuge. This suggests that females actively refuge from castrated males, and that housing with such males is sufficient to generate an increased glucocorticoid response. Our results show that females choose to refuge from males depending on the partner’s gonadal status, choices that are linked to social induced stress responses but not exposure to male mating behaviour.

Exposure to Non-Native Tropical Milkweed Promotes Reproductive Development in Migratory Monarch Butterflies.

Background: North American monarchs (Danaus plexippus) are well-known for their long-distance migrations; however, some monarchs within the migratory range have adopted a resident lifestyle and breed year-round at sites where tropical milkweed (Asclepias curassavica) is planted in the southern coastal United States. An important question is whether exposure to exotic milkweed alters monarch migratory physiology, particularly the ability to enter and remain in the hormonally-induced state of reproductive diapause, whereby adults delay reproductive maturity. Cued by cooler temperatures and shorter photoperiods, diapause is a component of the monarch’s migratory syndrome that includes directional flight behavior, lipid accumulation, and the exceptional longevity of the migratory generation. Methods: Here, we experimentally test how exposure to tropical milkweed during the larval and adult stages influences monarch reproductive status during fall migration. Caterpillars reared under fall-like conditions were fed tropical versus native milkweed diets, and wild adult migrants were placed in outdoor flight cages with tropical milkweed, native milkweed, or no milkweed. Results: We found that monarchs exposed to tropical milkweed as larvae were more likely to be reproductively active (exhibit mating behavior in males and develop mature eggs in females) compared to monarchs exposed to native milkweed. Among wild-caught fall migrants, females exposed to tropical milkweed showed greater egg development than females exposed to native or no milkweed, although a similar response was not observed for males. Conclusions: Our study provides evidence that exposure to tropical milkweed can increase monarch reproductive activity, which could promote continued residency at year-round breeding sites and decrease monarch migratory propensity.

On the discovery of a male morph with a novelty alternative mating tactic in the neotropical cricket Macroanaxipha macilenta Orthoptera: Gryllidae)

Several animal taxa exhibit discrete male phenotypes, which are related to alternative mating tactics. In this study, we describe a new male phenotype and mating behavior of the cricket species Macroanaxipha macilenta. The most common male phenotype shows male-biased sexual size dimorphism, with wider forewings than those of the new male phenotype. Wide-forewing males produce longer and louder calling songs than narrow-forewing males, and after attracting a female, the wide-forewing male transfers a spermatophore during a 21-s copulation. On the other hand, narrow-forewing males occur at a low frequency in the population (< 20%), produce short whisper calls, and copulate twice with the female. In each copulation, the narrow-forewing male transfers one spermatophore. The first one is removed and eaten by the female shortly after copulation. Then, if the female stays near the male, they copulate again, and a second spermatophore is transferred to the females’ genitalia. Mating duration in narrow-forewing males can last up to 12 min. Both male morphs may represent alternative mating tactics.

Evaluating the Effect of Honey Bee (Apis mellifera) Queen Reproductive State on Pheromone-Mediated Interactions with Male Drone Bees.

Honey bee (Apis mellifera) queens produce pheromones responsible for mediating both male mating behavior and many critical facets of worker social organization within their colony. These pheromones are dynamic multi-component blends, allowing the communication of detailed information. Indeed, variation in the queen's mating and reproductive state is associated with significant changes in her pheromone profiles, and these different pheromone profiles elicit different behavioral and physiological responses in female workers. Here we evaluate behavioral responses of male drones to the chemical blends produced by two exocrine glands in queens, and determine if the blends and responses are altered by the queen's mating and reproductive state. We find that drone attraction to the chemical blends of mandibular glands produced by mated, laying queens versus virgin queens is reduced, suggesting that the queens produce a reliable signal of their mating receptivity. Interestingly, while the chemical blends of mating, laying queens and virgins queens largely overlap, mated, laying queens produce a greater number of chemicals and greater quantities of certain chemicals than virgin queens, suggesting that these chemicals may serve to inhibit behavioral responses of drones to mated, laying queens. Thus, our results highlight the importance of considering chemical cues and signals that serve to both stimulate and inhibit behavioral responses during social interactions in animals.

Size-selective harvesting fosters adaptations in mating behaviour and reproductive allocation, affecting sexual selection in fish.

The role of sexual selection in the context of harvest-induced evolution is poorly understood. However, elevated and trait-selective harvesting of wild populations may change sexually selected traits, which in turn can affect mate choice and reproduction. We experimentally evaluated the potential for fisheries-induced evolution of mating behaviour and reproductive allocation in fish. We used an experimental system of zebrafish (Danio rerio) lines exposed to large, small or random (i.e. control) size-selective mortality. The large-harvested line represented a treatment simulating the typical case in fisheries where the largest individuals are preferentially harvested. We used a full factorial design of spawning trials with size-matched individuals to control for the systematic impact of body size during reproduction, thereby singling out possible changes in mating behaviour and reproductive allocation. Both small size-selective mortality and large size-selective mortality left a legacy on male mating behaviour by elevating intersexual aggression. However, there was no evidence for line-assortative reproductive allocation. Females of all lines preferentially allocated eggs to the generally less aggressive males of the random-harvested control line. Females of the large-harvested line showed enhanced reproductive performance, and males of the large-harvested line had the highest egg fertilization rate among all males. These findings can be explained as an evolutionary adaptation by which individuals of the large-harvested line display an enhanced reproductive performance early in life to offset the increased probability of adult mortality due to harvest. Our results suggest that the large-harvested line evolved behaviourally mediated reproductive adaptations that could increase the rate of recovery when populations adapted to high fishing pressure come into secondary contact with other populations.

A synthetic male-specific sterilization system using the mammalian pro-apoptotic factor in a malaria vector mosquito

Conditional cell death systems are useful for various aspects of basic science with a wide range of applications, including genetic pest control. We recently demonstrated that expression of the mammalian pro-apoptotic factor, B-cell leukaemia/lymphoma 2-associated X protein (Bax), can induce apoptosis in specific tissues by using tissue specific promoters in silkworm and mosquito. Here, we newly identified a functional promoter in the Asian malaria vector, Anopheles stephensi, which enables gene expression specifically in the testis. We produced a transgenic mosquito line that expresses mouse Bax under the control of this testis-specific promoter. Transgenic mosquito males exhibited aberrant testes without functional sperm and complete sterility, whereas transgenic females maintained normal fecundity. Despite their abnormal testes, the transgenic males maintained normal function of male accessory glands and typical mating behaviour. As a result of mating with these males, females showed refractoriness to further mating. These results suggest that transgenic males induce female sterility via mating. The mosquito is one of the most important disease vectors, and the control of their population benefits global public health. Thus, this Bax-mediated synthetic male-specific sterilization system could be applied to population control of mosquitoes.

Corticosterone mediated mate choice affects female mating reluctance and reproductive success

The study of stress-related hormones as mediators of sexual selection has traditionally focused on the effect of glucocorticoids on male quality and competing ability. However, environmental stressors are expected to affect both males and females, and the strength of sexual selection might be affected by changes in female mating decisions, a hypothesis that has rarely been tested. Here, we investigated whether female common lizard (Zootoca vivipara) mating behaviour and mating preferences are affected by different levels of administered corticosterone and conditioned by the familiarity of their partners, which is known to influence Z. vivipara social behaviour. To this end, two females, one corticosterone-treated and one control female, were simultaneously presented with an unfamiliar male and the following day with either a familiar or an unfamiliar male. Females treated with corticosterone (Cort) were more aggressive towards males and mated less. Furthermore, copulation probability in Cort females, but not in control females, increased with body size. On the second day, Cort females only mated with familiar partners. In contrast, male behaviour towards females was not affected by treatment and only bigger males successfully copulated with Cort females. This shows that corticosterone directly affected female mating behaviour and mating preferences, while male mating behaviour was unaffected by the female's level of corticosterone. Environmental and social stressors may affect reproductive strategies of females, the strength of sexual selection, and sexual conflict through their effects on female glucocorticoid levels, potentially in a wide range of species.

Sperm-limited males continue to mate, but females cannot detect the male state in a parasitoid wasp

Female mating frequency and male ejaculate allocation are likely to interact. Females may adjust their propensity for remating based on the amount of provided sperm to ensure a sufficient sperm supply, and males may determine sperm allocation based on female availability and female mating frequency. In this study, I investigated male and female mating behaviors in the parasitoid wasp Anisopteromalus calandrae. The wasp exhibits the haplo-diploid sex determination, in which sperm-depleted females are constrained to produce only sons by laying unfertilized eggs. The first experiment showed that a rapid succession of male mating decreased the production of daughters (fertilized eggs) by the inseminated females, suggesting that sperm-limited males provided an insufficient amount of sperm to the females. Although the males appeared to replenish their sperm store after 6 h, they mated upon encountering females despite their sperm shortage. The second experiment showed that copulation reduced the subsequent mating receptivity of the inseminated females irrespective of whether the females received a sufficient amount of sperm. Moreover, although approximately 26% of females accepted a second mating and recovered a certain degree of daughter production, remating was independent of the mating status of their first mating partner or the social environment. These results suggest that sperm-limited males may benefit from continuing to mate because their copulation prevents competing males from reproducing with their mates. Females incur a cost from not remating depending on the amount of sperm provided, which may result from weak environmental selection pressure or manipulation by the initial mate.Significance statementMale and female mating strategies are likely to evolve interdependently. Specifically, in species that produce limited numbers of sperm, the mating behavior of males and females is likely to be influenced by sperm transfer. The results of the present study suggest that males of the parasitoid wasp Anisopteromalus calandrae can replenish their sperm stores over time. However, sperm-limited males that encounter a potential mating partner mate rather than wait for sperm recovery. Females do not discriminate the male state before copulation, and those that mate with sperm-limited males suffer from sperm shortage. Although females can augment their sperm supply by remating, only a portion of females do so, regardless of sperm supply. The lack of a female facultative response suggests weak environmental selection on the species or the existence of sexual conflict over sperm transfer.

Me against who? Male guppies adjust mating behaviour according to their rival’s presence and attractiveness

AbstractSexual selection theory suggests that males need to constantly reappraise their mating decisions to take account of the presence and the phenotypes of their rivals. Here we examine this expectation by asking: (i) If the presence of a rival influences male mating behaviour; (ii) How important is the attractiveness of the rival (absolute attractiveness) in shaping male behaviour; and (iii) How does a male's attractiveness in comparison to his rival (relative attractiveness) influence a male's mating decisions. Using the Trinidadian guppy, a species in which female mate choice (based on males’ attractive traits) plays an important role in male mating outcomes, we recorded the frequency of courtship displays and unsolicited attempts by focal males. First, we quantified focal male mating behaviour with and without a rival. Since the probability of a successful mating is, on average, halved by the presence of a rival, we predicted that under competition the focal male would invest more in less costly mating tactic—unsolicited attempts. Second, we examined how the rival's standard length and area of orange coloration mediated focal male mating behaviour. We found that rival presence influenced how focal males responded to females in terms of both mating tactics. However, the rival attractiveness elicited changes only in male courtship display. Focal males increased courtship display rate if his rival was small or if possessed large amounts of orange, regardless of considering rival absolute or relative attractiveness. Our results show that males invest in the costlier mating tactic when there is no rival or in the presence of a smaller rival. Interestingly, they make a similar investment in the presence of an attractive orange rival. Overall, this study highlights the importance of fine‐grained male decisions in mating encounters and shows that mating tactics are differentially shaped by multiple competition risk cues.

Plasticity of Mating Duration in Response to Slightly Biased Operational Sex Ratios in the Water Strider (Aquarius remigis): The Effect of Cohabitation Under Standard Laboratory Conditions

In polygynandrous species, males face the trade-off between the pursuit of increased mating opportunities and securing paternity. Within such systems, males need to accurately assess the social composition of the local environment to maximize fitness. Here, we investigated this capability in the water strider (Aquarius remigis), a semi-aquatic insect known to exhibit a broad spectrum of mating behaviors and inhabit a socially diverse and changing environment. Using a combination of methodological designs to track both within- and between-subject effects, individuals remained in same-sex housing prior to being exposed to slightly biased operational sex ratios (2:1 vs. 1:2) with or without prior cohabitation to determine the effects on mating duration. Results show that males were sensitive to these subtle differences in social conditions, mating for longer periods within male-biased environments, but this was true only under conditions with prior cohabitation. In particular, when individuals could acclimate to the testing environment, mating duration dropped precipitously in female-biased conditions. These findings do not support the view that male water striders have consistent behavioral syndromes, and instead show that individuals are able to differentiate between, and adaptively respond to, small changes in the local sex ratio. In addition to improving our understanding of the plasticity of male mating behavior in this species, this study offers new insights for future laboratory research studying reproductive competition across a diverse range of polygynandrous animals.

No evidence that male sexual experience increases mating success in a coercive mating system

Several studies have shown that sexual experience can alter a male's mating behaviour to increase his future mating success. One explanation is that experienced males are better at courting females and inducing them to mate. Experienced males might also be better at identifying higher quality mates, although fewer studies have tested for this benefit. In both cases, however, these potential benefits of sexual experience might be partially offset by the energetic costs of courting and mating, which tend to reduce a male's subsequent ability to invest in sexually selected traits, and thereby reduce his future attractiveness and mating success (i.e. hasten the onset of reproductive senescence). Here we used the eastern mosquitofish, Gambusia holbrooki, to test whether sexual experience elevates male mating success. We housed recently matured males either with full mating access to females (experienced males) or in the visual and olfactory presence of females with which they could not mate (naive males). We then measured the strength of male mate choice for larger, more fecund, females, male mating behaviour (time spent chasing females and the number of copulation attempts) and insemination success. Experienced and naive males did not differ significantly in their mating behaviour and there was no effect of sexual experience on the likelihood of mating or on the number of sperm inseminated (although experienced males had a tendency to be less successful when performing gonopodial thrusts). Experienced males in two-choice trials were, however, significantly more likely to ‘inspect’ both females and had a significantly stronger preference for larger females. Finally, we measured male immune response and growth to test for any costs of the increased mating effort that is concomitant with greater experience. Experienced males had significantly slower postmaturation growth and a significantly weaker immune response than naive males.

Friend-or-foe? Behavioural evidence suggests interspecific discrimination leading to low probability of hybridization in two coexisting rock lizard species (Lacertidae, Darevskia)

The parthenogenetic rock lizard Darevskia rostombekowi is considered to be the product of hybridization between female Darevskia raddei and male Darevskia portschinskii. These two species coexist within several secondary contact areas; however, no trace of their hybridization has been previously reported. We conducted focal observations of individually marked lizards in 2017 and 2018 to establish if there is behavioural isolation between these species. We demonstrate that individuals distinguish between lizards of the same and different species. Individuals of both studied species interacted regularly, but we found no evidence of males of either species using interspecific interference competition for resources or for females. Neutral reactions prevailed in the reactions of males to the individuals of the different species; aggressive or submissive behaviour was more common towards males of the same species. The differences in reactions of males to females of the same and different species were less clear and interspecific social interactions were almost as common as intraspecific interactions. Interspecific male mating behaviour was rare and unsuccessful; only a single female with heterospecific copulation marks on the body was found. The mating period in both species overlapped broadly in late May and early June; body size (SVL) in females of both species was equal. Hence, we suggest that the selection of the sexual partner and preference of the conspecific partner for the social and sexual contacts is the most plausible explanation of the revealed behavioural asymmetry in intra- and interspecific relationship. Here, we present the first description of the social and sexual behaviour of two bisexual species of rock lizard belonging to the Darevskia genus. Most works devoted to the study of reticulate evolution in lizards have used genetic and morphological approaches rather than behavioural observations. The study of the proximal mechanisms of evolution is important in understanding how evolution occurs. The results indicate that even in ecologically similar species, social and sexual selection tend towards separation of the species rather than mixing, although they are able to coexist peacefully.

Defects in mating behavior and tail morphology are the primary cause of sterility in Caenorhabditiselegans males at high temperature.

Reproduction is a fundamental imperative of all forms of life. For all the advantages sexual reproduction confers, it has a deeply conserved flaw: it is temperature sensitive. As temperatures rise, fertility decreases. Across species, male fertility is particularly sensitive to elevated temperature. Previously, we have shown in the model nematode Caenorhabditiselegans that all males are fertile at 20°C, but almost all males have lost fertility at 27°C. Male fertility is dependent on the production of functional sperm, successful mating and transfer of sperm, and successful fertilization post-mating. To determine how male fertility is impacted by elevated temperature, we analyzed these aspects of male reproduction at 27°C in three wild-type strains of C. elegans: JU1171, LKC34 and N2. We found no effect of elevated temperature on the number of immature non-motile spermatids formed. There was only a weak effect of elevated temperature on sperm activation. In stark contrast, there was a strong effect of elevated temperature on male mating behavior, male tail morphology and sperm transfer such that males very rarely completed mating successfully when exposed to 27°C. Therefore, we propose a model where elevated temperature reduces male fertility as a result of the negative impacts of temperature on the somatic tissues necessary for mating. Loss of successful mating at elevated temperature overrides any effects that temperature may have on the germline or sperm cells.

Rarity of Size-Assortative Mating in Animals: Assessing the Evidence with Anuran Amphibians.

Assortative mating in animals can have substantial evolutionary impact. Numerous reports also make it appear to be pervasive in occurrence. In assortative mating, defined here in behavioral terms, animals select their mates according to a particular shared trait such that mated individuals phenotypically resemble each other more than expected by chance. Body size is a widely studied assortment trait. This is especially relevant for anuran amphibians (frogs and toads), among whom reproductive advantages may accrue to large individuals of both sexes. Anurans also exhibit discrete forms of male mating behavior. Sedentary calling behavior of "sitters" allows for female choice, whereas fighting for possession of mates by "scramblers" precludes female choice. Size-assortative mating in anurans should therefore be a property of sitters, not scramblers. I used meta-analysis to assess the occurrence of true size-assortative mating in relation to mating behavior and other variables in 282 studies of 68 species of anurans. I found publication bias against reporting nonsignificant results and analytical bias resulting from pooling of samples collected at different times or places (Simpson's paradox). Pooled samples significantly inflated the apparent occurrence and strength of size-assortative mating. Controlling for such biases left little credible evidence for size-assortative mating behavior in any anurans. Instead, large-male advantage among scramblers was associated with a secondary pattern of concomitant nonrandom mating. In this disproportionate mating, neither sex behaves according to mate choice rules that could lead to consistently strong assortment. It should thus have relatively little evolutionary impact compared to true assortative mating.