Terms Of Reproductive Success Research Articles

Amphipod Isotope Composition, Condition and Reproduction in Contrasting Sediments: A Reciprocal Transfer Experiment

Eutrophication is a process that results in excessive phytoplankton blooms, which sink to the sediment and enrich the organic matter (OM). This alters the available resources to benthic organisms and may have consequences for feeding ecology and reproduction strategies of marine populations. While effects of eutrophication on biodiversity are well documented, the more subtle effects of OM on population dynamics and diet plasticity are understudied. We performed a reciprocal transfer experiment with the benthic bioindicator amphipod Monoporeia affinis from two stations in the Baltic Sea with differing sediment OM (low and high) creating four treatments (low control, low transferred, high transferred, and high control). We investigated sediment OM effects on: i) the dietary niche and organism body condition of two different life stages of M. affinis utilizing bulk stable isotopes δ13C and δ15N, and C:N ratio; and ii) M. affinis fecundity and embryo viability. There was no initial significant differences between the females from different stations in terms of δ13C, δ15N, C:N, fecundity or viable embryos. However, we found that moving females from high OM to low OM (where the low OM sediment has higher δ15N and lower δ13C) significantly depleted their 13C values, while amphipods in low OM sediment had always significantly enriched 15N regardless of female origin indicating feeding on the new sediment. Although end-of-experiment females had lower C:N than initial females, individuals in low OM sediment presented significantly higher C:N (indicating higher body condition) than those in high OM sediment. Conversely to adult amphipods, no effects of OM were seen for juveniles δ13C or δ15N, but their individual biomass was larger in high OM sediment treatments and high OM transferred to low OM sediment. Our results indicate that the low range of sediment OM tested here altered female amphipod δ13C, δ15N and C:N ratios, with those in low OM treatments having a better body condition, but those in high OM treatments had a greater reproductive success in terms of offspring biomass. Our findings suggest a tradeoff between female condition and reproduction and indicates that even relatively small levels of sediment organic enrichment will impact female condition. Our study provides valuable information useful to interpret the effects of OM on amphipod populations used as bioindicators for anthropogenic impacts.

Darwin’s empirical claim and the janiform character of fitness proxies

Darwin’s claim about natural selection is reconstructed as an empirical claim about a causal connection leading from the match of the physiology of an individual and its environment to leaving surviving progeny. Variations in this match, Darwin claims, cause differences in the survival of the progeny. Modern concepts of fitness focus the survival side of this chain. Therefore, the assumption that evolutionary theory wants to explain reproductive success in terms of a modern concept of fitness has given rise to the so-called tautology problem. It is shown that the tautology problem reappears in the treatment of fitness proxies in today’s experimental evolutionary biology when these proxies are considered to indicate fitness only. Taking Darwin’s empirical claim seriously suggests, by contrast, that fitness proxies are first of all measures of the match between organism and environment, which I call the organism’s ‘fittedness’. At the same time, they are indeed related to reproductive success. Thus looking in both directions, at fitness and at fittedness, they are janiform. Acknowledging this situation not only allows for rejection of the tautology objection, but also for integration of Darwin’s argument into current evolutionary biology. It is suggested that this helps reframe and alleviate the dispute between the Modern Synthesis and the Extended Evolutionary Synthesis.

Intralocus conflicts associated with a supergene

Chromosomal inversions frequently underlie major phenotypic variation maintained by divergent selection within and between sexes. Here we examine whether and how intralocus conflicts contribute to balancing selection stabilizing an autosomal inversion polymorphism in the ruff Calidris pugnax. In this lekking shorebird, three male mating morphs (Independents, Satellites and Faeders) are controlled by an inversion-based supergene. We show that in a captive population, Faeder females, who are smaller and whose inversion haplotype has not undergone recombination, have lower average reproductive success in terms of laying rate, egg size, and offspring survival than Independent females, who lack the inversion. Satellite females, who carry a recombined inversion haplotype and have intermediate body size, more closely resemble Independent than Faeder females in reproductive performance. We inferred that the lower reproductive output of Faeder females is most likely balanced by higher than average reproductive success of individual Faeder males. These findings suggest that intralocus conflicts may play a major role in the evolution and maintenance of supergene variants.

Long-term monitoring data reveal effects of age, population density, and environmental aspects on hatching success of Common Cranes (Grus grus)

Facing climate and land use change, a species’ ability to successfully adapt to changing environments is crucial for its survival. Extensive drainage and intensification of agriculture and forestry set wetlands and associated species at risk of population declines. The population of Common Cranes (Grus grus) has experienced considerable fluctuations over the last century. Despite increasing population numbers, hatching success seemed to have decreased over the last years. The aim of this study was to identify factors influencing hatching success and nest survival of Common Cranes based on analyses of long-term individual-based monitoring data from northeastern Germany and evaluate the species ability to adapt to changing environments. Hatching success decreased over the course of the study period from 0.75 to 0.55. Surprisingly, nest survival and hatching success did not vary across different nesting habitats, whereas factors such as female age, timing of nest initiation and breeding pair density were found to have significant effects on hatching success. Older females showed higher hatching success, even though the proportion of unhatched eggs was highest in females aged 20 years or older. Early nest initiation had a positive effect on hatching success. Water levels are more favorable early in the nesting season, whereas increasing evaporation with time causes water levels to decrease, granting easier access for predators. Independently of female age, hatching success decreased with increasing numbers of breeding pairs within a 2-km radius around a nesting site. High population densities intensify competition for resources and promote intraspecific interactions, affecting reproductive outcome negatively. This study gives first insights into mechanisms behind population regulation in Common Cranes, highlighting the importance of population dynamics and individual features. We suggest to further investigate density dependent effects including landscape and habitat features as well as reproductive success in terms of chick survival, since successfully raising juveniles is crucial for a species survival.

Distribution and phenotypic effect of Wolbachia in natural population of Indian Drosophila

Background & objectives: Wolbachia (alpha-proteobacteria, Rickettsiaceae) undergoes maternal transmission and manipulates host reproductive fitness. Wolbachia strains in the Drosophila host (wMel, wRi) have significant implications in controlling arboviral diseases and are being transfected into the mosquito population. The efficient use of Wolbachia as a biocontrol agent calls for a need to understand its biology and host-symbiont interactions. The present work is a baseline study to explore the distribution of Wolbachia strains and their effect on the reproductive fitness of Drosophila (Drosophilidae, Diptera) hosts from India. Methods: The distribution and strain identification of Wolbachia was done by PCR and sanger sequencing method in Indian Drosophila host species. For further setting up of host-phenotype experiments, control (nature-caught Wolbachia- infected) and treated (antibiotics-treated Wolbachia-uninfected) host Drosophila laboratory-established lines were used. Results: The presence of Wolbachia was found to be limited to only three Drosophila host species i.e. D. melanogaster, D. simulans and D. ananassae and their distribution frequency was not influenced by host ecological background. Wolbachia infection was seen to provide a fitness advantage in terms of reproductive success in D. melanogaster; however, tetracycline treatment could not remove Wolbachia from D. ananassae, preventing us from conducting experiments in this species. Interpretation & conclusion: These results reaffirm the host specific nature of Wolbachia infection and highlight for the first time Wolbachia distribution and phenotypic effect in Indian Drosophila host. In the wake of world mosquito programme, it is crucial to identify Wolbachia strains in natural population and evaluate their effects on host species for making it an effective bio-control agent.

Is developmental rate polymorphism constant? Influence of temperature on the occurrence and constancy of slow and fast development in Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae).

Temperature plays an important role in different biological activities of organisms. The relationship between temperature and insect development has long been recognized as an important environmental parameter in modeling insect population dynamics. Although few studies have investigated the existence of developmental rate polymorphism within a cohort, the role of abiotic and biotic factors on such developmental variation has so far been meagerly investigated. The present study was designed to investigate the effect of thermal extremes on the developmental rate polymorphism and its influence on reproductive potential of Parthenium beetle, Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae). The study will also be helpful in solving hitherto whether the existence of slow and fast developers within a cohort has a purely genetic basis or this developmental polymorphism is presided by environmental factors. Our result reveals a clear bimodal pattern of distribution with two peaks at each temperature (20, 25, 27, 30 and 35°C) where the first peak represents the fast developers and second peak represents the slow developers. Both developmental variants took the longest duration for development at 20°C followed by 25, 27, 30°C and minimum at 35°C. More fast developers were found at higher temperatures. Slow developing individuals were heavier than the fast developing individuals regardless of rearing temperature. Slow developers have higher reproductive success in terms of fecundity and egg viability than the fast developers. The results of this study denote the constancy of the developmental rate polymorphism within a cohort and the possibility that this polymorphism was owing to the exogenous cues inclined differential rates of mortality.

Experimental admixture among geographically disjunct populations of an invasive plant yields a global mosaic of reproductive incompatibility and heterosis

Abstract Invasive species have the ability to rapidly adapt in the new regions where they are introduced. Classic evolutionary theory predicts that the accumulation of genetic differences over time in allopatric isolation may lead to reproductive incompatibilities resulting in decreases in reproductive success and, eventually, to speciation. However, experimental evidence for this theoretical prediction in the context of invasive species is lacking. We aimed to test for the potential of allopatry to determine reproductive success of invasive plants, by experimentally admixing genotypes from six different native and non‐native regions of Centaurea solstitialis, an invasive forb for which preliminary studies have detected some degree of reproductive isolation between one native and non‐native region. We grew plants under common garden conditions and outcrossed individuals originating from different source populations in the native and introduced range to evaluate reproductive success in terms of seed to ovule ratio produced. We also assessed geographical and genetic isolation among C. solstitialis regions as a potential driving factor of reproductive success. Experimental admixture generated mixed fitness effects, including significant increases, decreases and no differences in reproductive success as compared to crosses within population (control). Centaurea solstitialis invasive populations in the Americas generated preponderantly negative fitness interactions, regardless of the pollen source, suggesting selection against immigrants and reinforcement. Other non‐native populations (Australia) as well as individuals from the native range of Spain demonstrated an increase in fitness for between‐region crosses, indicating inbreeding. These differences show an asymmetrical response to inter‐regional gene flow, but no evidence of isolation by distance. Synthesis. The speed of adaptation and the accumulation of reproductive incompatibilities among allopatric populations of invasive species might be more rapid than previously assumed. Our data show a global mosaic of reproductive outputs, showcasing an array of evolutionary processes unfolding during colonization at large biogeographical scales.

Wildflower strips enhance wild bee reproductive success

Abstract Intensification of agriculture has resulted in a simplification and fragmentation of agroecosystems. Yet, its impact on the reproductive success and population dynamics of wild bees, and how adverse effects can be mitigated, remains poorly understood. We established populations of seven solitary bee species varying in body size in experimentally sown wildflower strips (WFS), existing semi‐natural habitats (SNH; forest edges) and isolated sites lacking WFS and SNH in the local surrounding (350 m radius) to test (a) whether the wild bee species use planted flowers of WFS to provision offspring with pollen, (b) whether vicinity to WFS reduces their foraging trip duration, (c) parasitism rate and (d) whether it increases bee reproductive success of nesting populations. Furthermore, we tested whether the effect size depends on the body size of the bee species considered. We show that wild bees nesting in WFS provisioned their offspring primarily with pollen from plants of WFS. This led to shorter foraging trips of all bee species nesting in WFS compared to bees nesting in isolated (unrestored) sites and overall increased reproductive success (i.e. more viable offspring). Reproductive success of bees nesting in WFS was also higher, and parasitism rates lower, compared to bees nesting at forest edges. Smaller—potentially less mobile—bee species benefitted more than larger ones from WFS plantings in terms of reproductive success. Synthesis and applications. Our findings demonstrate that diverse WFS can enhance the reproductive success of multiple solitary wild bee species, thereby mitigating negative impacts of agroecosystem simplification through the provision of suitable floral resources and reduced foraging times required for offspring provisioning. Our study further indicates that a relatively fine‐meshed network of wildflower plantings and nesting habitats is required to most effectively enhance reproduction and populations of solitary bees in agricultural landscapes.

Life-history trade-offs among four sympatric seabreams

Fish life history is shaped by environmental and ecological circumstances but constrained by phylogeny. Life-history trade-offs can be exposed in a comparison of closely related species with similar niches. We compare the life histories of four closely related and similar-sized, sympatric, omnivorous seabreams (Sparidae) that share the same physical habitat, namely the steentjie Spondyliosoma emarginatum, hottentot Pachymetopon blochii, white stumpnose Rhabdosargus globiceps and Fransmadam Boopsoidea inornata. Samples of each species were obtained in every season from the southwestern Cape, South Africa, to obtain measures of length, mass, gonadosomatic index (GSI) and condition. Large variations in sex ratio, GSI, and spawning season length (SSL) among species are described. Differences in patterns of sex-specific GSI and condition point to different mating systems. Spondyliosoma emarginatum is a nest-guarding, short-lived, protogynous hermaphrodite. Pachymetopon blochii is a resident group-spawner. Rhabdosargus globiceps is a moderately long-lived migrant group-spawner, with a sex ratio closest to 1:1. Boopsoidea inornata is a polygamous, long-lived resident with low annual fecundity. Trade-offs are apparent between annual fecundity and longevity, parental care and male GSI, parental care and SSL, migration and SSL, hermaphroditism and migration, and hermaphroditism and bet-hedging. The cost of sequential hermaphroditism in marine fish is considered in terms of reproductive success in highly variable environments.

Are offspring begging levels exaggerated beyond the parental optimum? Evidence from a bidirectional selection experiment.

Parental care involves elaborate behavioural interactions between parents and their offspring, with offspring stimulating their parents via begging to provision resources. Thus, begging has direct fitness benefits as it enhances offspring growth and survival. It is nevertheless subject to a complex evolutionary trajectory, because begging may serve as a means for the offspring to manipulate parents in the context of evolutionary conflicts of interest. Furthermore, it has been hypothesized that begging is coadapted and potentially genetically correlated with parental care traits as a result of social selection. Further experiments on the causal processes that shape the evolution of begging are therefore essential. We applied bidirectional artificial selection on begging behaviour, using canaries (Serinus canaria) as a model species. We measured the response to selection, the consequences for offspring development, changes in parental care traits, here the rate of parental provisioning, as well as the effects on reproductive success. After three generations of selection, offspring differed in begging behaviour according to our artificial selection regime: nestlings of the high begging line begged significantly more than nestlings of the low begging line. Intriguingly, begging less benefitted the nestlings, as reflected by on average significantly higher growth rates, and increased reproductive success in terms of a higher number of fledglings in the low selected line. Begging could thus represent an exaggerated trait, possibly because parent-offspring conflict enhanced the selection on begging. We did not find evidence that we co-selected on parental provisioning, which may be due to the lack of power, but may also suggest that the evolution of begging is probably not constrained by a genetic correlation between parental provisioning and offspring begging.

Sex, personality and conspecific density influence natal dispersal with lifetime fitness consequences in urban and rural burrowing owls.

There is a growing need to understand how species respond to habitat changes and the potential key role played by natal dispersal in population dynamics, structure and gene flow. However, few studies have explored differences in this process between conspecifics living in natural habitats and those inhabiting landscapes highly transformed by humans, such as cities. Here, we investigate how individual traits and social characteristics can influence the natal dispersal decisions of burrowing owls (Athene cunicularia) living in urban and rural areas, as well as the consequences in terms of reproductive success and apparent survival. We found short dispersal movements among individuals, with differences between urban and rural birds (i.e., the former covering shorter distances than the latter), maybe because of the higher conspecific density of urban compared to rural areas. Moreover, we found that urban and rural females as well as bold individuals (i.e., individuals with shorter flight initiation distance) exhibited longer dispersal distances than their counterparts. These dispersal decisions have effects on individual fitness. Individuals traveling longer distances increased their reproductive prospects (productivity during the first breeding attempt, and long term productivity). However, the apparent survival of females decreased when they dispersed farther from their natal territory. Although further research is needed to properly understand the ecological and evolutionary consequences of dispersal patterns in transformed habitats, our results provide information about the drivers and the consequences of the restricted natal movements of this species, which may explain its population structuring through restricted gene flow between and within urban and rural areas.

Untangling systematics of the Paramacrobiotus areolatus species complex by an integrative redescription of the nominal species for the group, with multilocus phylogeny and species delineation in the genus Paramacrobiotus

Abstract Incomplete descriptions of nominal taxa are one of the most significant obstacles in modern taxonomy, including the taxonomy of Tardigrada. Another major problem in tardigrade systematics is the lack of tests for the reliability of genetic markers in species delineation. Here, we employ an integrative taxonomy approach to redescribe the nominal taxon for the P. areolatus complex, Paramacrobiotus areolatus. Moreover, we obtained multilocus DNA sequences for another 16 populations representing 9–12 Paramacrobiotus species collected from Europe, North America, Africa and Australia, enabling us to reconstruct the most extensive phylogeny of the genus to date. The identification of a pair of potentially cryptic dioecious P. areolatus complex species with divergent genetic distances in ITS2 (1.4%) and COI (13.8%) provided an opportunity to test the biological species concept for the first time in the history of tardigrade taxonomy. Intra- and interpopulation crosses did not differ in reproductive success in terms of F1 offspring. However, because of the low F1 family sizes, we were unfortunately unable to test F1 hybrid fertility. Although our results are only partially conclusive, they offer a baseline not only for further taxonomic and phylogenetic research on the areolatus complex, but also for studies on species delineation in tardigrades in general.

Prolactin concentrations predict parental investment and nest survival in a free-living shorebird

The hormonal milieu that exists during reproduction is one of the key factors influencing the trade-off between reproductive investment and self-maintenance. Much previous work in birds has focused on prolactin as a physiological mediator since prolactin is involved in the onset and maintenance of parental care. However, how prolactin relates to reproductive success in terms of altering parental behavior in wild bird populations is not fully understood. Here, we report prolactin concentrations in breeding Kentish plovers (Charadrius alexandrinus), a small shorebird with variable mating systems and parental care, as an ecological model of mating system evolution. Throughout the breeding season, we estimated the circulating prolactin concentrations in male and female plovers during incubation. In addition, we monitored parental behavior and determined the fate of nests. We found that prolactin concentrations decreased during incubation but increased with clutch completion date. In addition, males and females with high prolactin concentrations spent more time on incubation than those with low prolactin concentrations. Importantly, higher prolactin concentrations in either males or females predict higher nest survival. Our results suggest that prolactin is an indicator of parental behavior in a wild shorebird population, although additional studies including experimental manipulation of prolactin concentrations are necessary to verify this relationship.

Paternal activation of CB2 cannabinoid receptor impairs placental and embryonic growth via an epigenetic mechanism

The cannabinoid receptor type 2 (CB2) is the peripheral receptor for cannabinoids, involved in the homeostatic control of several physiological functions. Male mitotic germ cells express a high level of CB2, whose activation promotes their differentiation in both in vitro and in vivo experiments, controlling the correct progression of spermatogenesis. However, it remains elusive if CB2 activation in spermatogonia could affect reproductive success in terms of fertility and healthy pregnancy outcomes. In this study, we explored the effects of male CB2 activation on sperm number and quality and its influence on next generation health. We show that exposure of male mice to JWH-133, a selective CB2 agonist, decreased sperm count, impaired placental development and reduced offspring growth. These defects were associated with altered DNA methylation/hydroxymethylation levels at imprinted genes in sperm and conserved in placenta. Our findings reveal that paternal selective activation of CB2 alters the sperm epigenome and compromises offspring growth. This study demonstrates, for the first time, a new role of CB2 signaling in male gametes in causing epigenetic alterations that can be transmitted to the next generation by sperm, highlighting potential risks induced by recreational cannabinoid exposure.

Shift in flowering time allows diploid and autotetraploid Anacamptis pyramidalis (Orchidaceae) to coexist by reducing competition for pollinators

AbstractHow autopolyploids establish when competing with diploid progenitors is still poorly understood. Here, we investigate the effects of morphological and phenological divergence on the reproductive success of co-occurring diploid and autotetraploid individuals of Anacamptis pyramidalis to disentangle the mechanisms allowing their c-oexistence. We estimated reproductive success in terms of absolute and relative fruit production and recorded morphological and phenological traits of the two cytotypes. We also estimated correlations between traits within cytotypes and the related phenotypic selection patterns. The two cytotypes experience similar levels of reproductive success, but they differ significantly in their morphological and phenological traits. Correlations among floral traits were weaker in autotetraploids than in diploids, but among-individuals variation was higher in diploids. For most flower traits, the strength of phenotypic selection was different in the two cytotypes. We found selection on flower number in both cytotypes, whereas selection for earlier flowering time was only found in late-flowering diploids. Our results suggest that a shift in flowering time may have allowed diploid and autotetraploid A. pyramidalis individuals to reduce competition for naïve pollinators. Consequently, the two cytotypes can coexist by attaining similar levels of reproductive success and, at same time, reducing the likelihood of inter-cytotype mating.

Status And Effects Of Food Provisioning on Ecology of Assamese Monkey (Macaca Assamensis) In Ramdi Area of Palpa, Nepal

The population status of Assamese monkey (Macaca assamensis) (McClelland 1840) and its interaction with the local people is poorly documented in Nepal. In 2014, we studied the population status, diurnal time budget and human-monkey conflict in Ramdi, Nepal by direct count, scan sampling and questionnaire survey methods, respectively. Two troops of Assamese monkey having total population of 48 with the mean troop size of 24 individuals were recorded in the study area. The group density was 0.33 groups / km² with a population density of 6 individuals/ km². The male to female adult sex ratio was 1:1.75 and the infant to female ratio was 0.85. The provisioned troop of Assamese monkey in Ramdi spent less time in feeding and movement while higher time was invested in resting and grooming than the nonspecific populations in the wild habitats. The human-monkey conflict is high in Ramdi, primarily due to the crop-raiding from fields and even the storage; the major crops raided are maize, vegetables, pulses and fruits. The higher reproductive success in terms of infant to adult female ratio, increased human-monkey conflicts and lesser investment of the diurnal time in foraging and feeding by Assamese monkey troop of Ramdi might be associated with the food provisioning. Journal of Institute of Science and TechnologyVolume 22, Issue 2, January 2018, Page: 183-190

Reproductive performance parameters in a large population of game-ranched white rhinoceroses (Ceratotherium simum simum).

The population of free-roaming white rhinoceroses (Ceratotherium simum) is under serious threat. Captive breeding of this species is therefore becoming more important, but this is challenging and often not successful. Obtaining reproductive reference values is a crucial aspect of improving these breeding results. In this study performed between 2008 and 2016, reproductive performance was analysed in 1,354 animals kept in a 8000 hectares game-ranched environment. Descriptive statistics of this captive population showed an average annual herd growth (%) of 7 .0±0.1 (min -9 –max 15). Average calving rates were calculated as an annual calving rate of 20% and biennial calving rate of 37% adult females calving per year. Females had a median age of 83.2 months at first calving (IQR 72.9–110.7) and inter-calving intervals of 29.2 (IQR 24.6–34.8) months. Furthermore, translocations of animals did not interfere with reproductive success in terms of inter-calving periods or age at first calving. Multivariate models showed a clear seasonal calving pattern with a significant increase of the number of calvings during December–April when compared to April–December. Our results did not show any significant skewed progeny sex ratios. Weather observations showed no significant influence of rain or season on sex ratios of the calves.

Fitness correlates of age at primiparity in a hunted moose population.

Trade-offs between fitness-related traits are predicted from the principle of resource allocation, where increased fecundity or parental investment leads to reduced future reproduction or survival. However, fitness traits can also be positively correlated due to individual differences (e.g. body mass). Age at primiparity could potentially explain variation in individual fitness either because early primiparity is costly, or it may lead to higher lifetime reproductive success. Based on long-term monitoring and genetic parentage assignment of an island population of moose, we quantified reproductive performance and survival, and examined whether early maturing females have higher total calf production than late maturing females. We explored if harvesting of calves affected the subsequent reproductive success of their mothers, i.e. also due to a post-weaning cost of reproduction, and whether there are any intergenerational effects of female reproductive success. There was a positive relationship between current and future reproduction. The probability to reproduce was lower for females that were unsuccessful the year before, indicating a strong quality effect on productivity. Females that started to reproduce as 2-year olds had a slightly higher total calf production compared to those starting at age three or four. High-performing mothers were also correlated with daughters that performed well in terms of reproductive success. Our results suggest that the observed individual heterogeneity in fitness could be associated with differences in age at primiparity. This heterogeneity was not affected by reproductive costs associated with tending for a calf post-weaning.

Mate choice could be random in female rats (Rattus norvegicus)

Female mate choice is often investigated in terms of reproductive success in order to understand how male characteristics contribute to sexual attractiveness. Previous studies have found that females rats prefer mating with their first encounter rather than males visited subsequently, suggesting that the rewarding value of this first encounter is enough to reinforce mating with the first partner. Using a multiple chambers paradigm, we allowed female rats to copulate freely with three males placed each in a different chamber. Then, we switched the males' position, and let the female interact with them freely again within the same session. We tested whether female mate choice was relying rather on a preferred male rat or on a preferred mating location. The results showed that females spent most time with the male in the chamber of 1st entry in the beginning, but as soon as male rats switched chambers, the female rat continued to copulate with the new male in the same chamber of 1st entry, instead of mating with her previously preferred male rat. This suggests that the male preference is an artefact of location preference. Therefore, female mate choice seems to be rather random than the consequence of an individual choice based on male characteristics. This finding, although contradictory with the intuitive feeling that mate choice is a crucial feature in sexual and reproductive behavior, is supported by several recent observations. In the coming years, behavioral neuroscience should bring light to the brain processes at work in random mate choice.

Problem-solving performance and reproductive success of great tits in urban and forest habitats.

Success in problem solving, a form of innovativeness, can help animals exploit their environments, and recent research suggests that it may correlate with reproductive success. Innovativeness has been proposed to be especially beneficial in urbanized habitats, as suggested by superior problem-solving performance of urban individuals in some species. If there is stronger selection for innovativeness in cities than in natural habitats, we expect problem-solving performance to have a greater positive effect on fitness in more urbanized habitats. We tested this idea in great tits (Parus major) breeding at two urban sites and two forests by measuring their problem-solving performance in an obstacle-removal task and a food-acquisition task. Urban pairs were significantly faster problem-solvers in both tasks. Solving speed in the obstacle-removal task was positively correlated with hatching success and the number of fledglings, whereas performance in the food-acquisition task did not correlate with reproductive success. These relationships did not differ between urban and forest habitats. Neophobia, sensitivity to human disturbance, and risk taking in the presence of a predator did not explain the relationships of problem-solving performance either with habitat type or with reproductive success. Our results suggest that the benefit of innovativeness in terms of reproductive success is similar in urban and natural habitats, implying that problem-solving skills may be enhanced in urban populations by some other benefits (e.g. increased survival) or reduced costs (e.g. more opportunities to gain practice with challenging tasks).