Higher Reproductive Investment Research Articles

Testicular histomorphometric patterns and spermatogenesis dynamics of Oecomys bicolor tomes, 1860 (Rodentia: Cricetidae).

Although the order Rodentia does not present a high risk of extinction compared to mammals as a whole, several families demonstrate high levels of threat and/or data deficiency, therefore highlighting the need for targeted research and the application of ecological and reproductive data to the development of conservation actions. The order Rodentia, the largest among mammals, includes 9 families, and the family Cricetidae is the most diverse of the Brazilian rodents. In Brazil, 12 of the 16 genera of Oecomys are found. Oecomys bicolor is known in Brazil as the 'arboreal rat' and is, found in dry, deciduous and tropical forests. The mean body weight of Oecomys bicolor was 35.8 g and the gonadal, tubular and epithelial somatic indexes were, 0.53%, 0.47% and 0.37%, respectively. Seminiferous tubules volume density was 89.72% and the mitotic and meiotic indexes corresponded to 8.59 and 2.45 cells, respectively, and the yield of spermatogenesis was 23.83 cells. The intertubular compartment represented 10.28% of the testis parenchyma and around 5% of the interstitial space was occupied by Leydig cells, whose number per gram of testis was 11.10 × 107 cells. By evaluating the biometric and histomorphometric characteristics of the testis, there is evidence that this species has a high investment in reproduction. Due to the high contribution of the seminiferous epithelium and the intertubular compartment in this species, compared to the others of the same family, it is possible to infer that the species Oecomys bicolor has a promiscuous reproductive behaviour.

Sexual receptivity of females on Neotropical scorpion Tityus pusillus Pocock, 1893 in response to male reproductive advances

AbstractDue to the high reproductive investment, females are the decisive sex when making decisions about whether or not to reproduce. Generally, female scorpions display aggressive sexual behavior in response to male reproductive advances when they are not receptive. However, female receptivity can vary over time, depending on environmental factors favorable to reproduction Thus, the current study aimed to examine the correlation between the number of reproductive attempts by male Tityus pusillus scorpion and mating success over time, considering the female's behavioral response. Behavioral analyses were monthly conducted on 150 T. pusillus field-caught pairs over a five-month period. Our results indicate that despite females reacting aggressively to male advances, the persistence of the male has a positive effect in courtship probability. Furthermore, we observed variations in female behavior throughout the studied period, suggesting that female receptivity might be linked to the reproductive season. Therefore, environmental factors may play a significant role in regulating scorpion reproduction in Neotropical forests.

Urban landscape organization is associated with species-specific traits in European birds

Urbanization is one of the main current drivers of the global biodiversity loss. Cities are usually developed in a gradient between land-sharing (low density housing with small and fragmented green areas) and land-sparing areas (high density housing with large and non-fragmented green patches) depending on the spatial organization of urban attributes. Previous studies have indicated differences in biodiversity between these two urban development types, but mechanisms underlying these differences are inadequately understood. In this context, the landscape features of each urban development type may select for organisms with specific traits. To analyze it, we quantified birds in 9 European cities during the breeding and wintering season, collected species-specific traits and performed Bayesian comparative analyses. We found that birds living in land-sparing areas had a higher reproductive investment and a higher nesting specialization than birds living in land-sharing areas during the breeding season. Typical birds from land-sparing urban areas during winter are fast-lived species. Our results indicate that urban development type could have an important role selecting animal traits and provides useful information on how to build more biodiversity-friendly cities.

To disperse or compete? Coevolution of traits leads to a limited number of reproductive strategies

Reproductive strategies are defined by a combination of behavioural, morphological, and life‐history traits. Reproductive investment and offspring propagule size are two key traits defining reproductive strategies. While a substantial amount of work has been devoted to understanding the independent fitness effects of each of these traits, it remains unclear how coevolution between them ultimately affects the evolution of reproductive strategies, and how this might influence the relationship between dispersal and environmental factors. In this study we explore how the evolution of reproductive strategies defined by these two coevolving traits is influenced by resource availability and spatial structuring of the environment using a simulation model. We find three possible equilibrium strategies across all scenarios: a competitor strategy with high reproductive investment (producing large propagules which disperse short distances), and two coloniser strategies differing in reproductive investment (both producing small propagules which disperse long distances). The possible equilibrium strategies for each scenario depended on starting conditions, spatial structure and resource availability. Evolutionary transitions between these equilibrium strategies were more likely in heterogeneous than homogeneous landscapes and at higher resource levels. Transition from coloniser strategy to competitor strategy was usually a two‐step process, with changes in propagule size following initial evolution in investment. This highlights how the interaction between the two trait axes affects the evolution of reproductive strategies, particularly where fitness valleys preclude the simultaneous evolution of traits. Our results highlight the need to incorporate trait coevolution into evolutionary models to help develop a more integrative understanding of the structure of natural populations and how the interaction between traits constrains or hinders evolutionary processes.

Seasonal shift in diet affects female reproductive anatomy but not mating behavior.

Females experience considerable environmental variability when breeding seasons are long. Adverse nutritional conditions can result in a reduction in mating and reproduction. However, a return to good nutrition may help animals resume high reproductive investment. I tested the silver spoon hypothesis in which females raised under poor conditions are reproductively limited compared to those raised under good conditions regardless of their adult environment. I used a specialist herbivore, Narnia femorata (Hemiptera: Coreidae), that lives on seasonally changing cacti. I provided juveniles and adults with a cactus pad with fruit (good diet), without fruit (restricted diet), or an improved adult diet (no fruit as juveniles, fruit at adulthood) to simulate a seasonal change in their diets near the end of the breeding season. I found that both ovary size and egg presence were reduced for females fed the restricted diet compared to those fed the good diet. Females fed the improved diet grew large ovaries like those fed the good diet, but few produced any eggs. Interestingly, female mating behavior did not change but females were less attractive to males when fed restricted diets. My results support the silver spoon hypothesis for compensatory growth and suggest that tradeoffs may occur between early survival and future reproduction when females experience a poor early life diet.

Increased male-induced harm in response to female-limited selection: interactive effects between intra- and interlocus sexual conflict?

Interlocus sexual conflict (IRSC) occurs because of shared interactions that have opposite effects on male and female fitness. Typically, it is assumed that loci involved in IRSC have sex-limited expression and are thus not directly affected by selective pressures acting on the other sex. However, if loci involved in IRSC have pleiotropic effects in the other sex, intersexual selection can shape the evolutionary dynamics of conflict escalation and resolution, as well as the evolution of reproductive traits linked to IRSC loci, and vice versa. Here we used an artificial selection approach in Japanese quail (Coturnix japonica) to test if female-limited selection on reproductive investment affects the amount of harm caused by males during mating. We found that males originating from lines selected for high female reproductive investment caused more oxidative damage in the female reproductive tract than males originating from lines selected for low female reproductive investment. This male-induced damage was specific to the oviduct and not found in other female tissues, suggesting that it was ejaculate-mediated. Our results suggest that intersexual selection shapes the evolution of IRSC and that male-induced harm may contribute to the maintenance of variation in female reproductive investment.

Assessment of glucocorticoids, sex steroids, and innate immunity in wild red-eared slider turtles (Trachemys scripta elegans)

When access to resources is limited, organisms must shift energy investment among physiological processes to survive, reproduce, and respond to unpredictable events. The shifting of these limited resources among processes may result in physiological tradeoffs, often mediated by glucocorticoids. We assessed relationships among the physiological processes of immunity, reproduction, and the stress response in wild adult red-eared slider turtles (Trachemys scripta elegans). Red-eared sliders exhibit a multi-clutching reproductive strategy that requires high energetic investment in reproduction at the beginning of the nesting season in females. Males mate in spring and undergo spermatogenesis and mating in late summer/early fall. We expected to observe tradeoffs when investment toward reproductive processes was particularly demanding. To test this, we subjected 123 individuals to a standardized acute stressor and collected blood to measure innate immunocompetence and circulating steroid hormone concentrations. Tradeoffs between female reproduction and immunocompetence occurred early in the nesting season. This high reproductive investment was evident by heightened circulating progesterone and reduced baseline innate immunity. Corticosterone (CORT) was also high during this period, indicating a role in facilitating allocation of energy. Tradeoffs were not as evident in males, though males upregulated innate immune function, baseline CORT, and testosterone prior to fall spermatogenesis and mating. Throughout the entire sampling period, both males and females increased CORT and immunocompetence following the acute standardized stressor. Taken together, we concluded that reproduction requires shifts in energy allocation in during the highest reproductive period for females but all individuals in this population remain able to respond to the standardized stressor even during increased reproductive investment. These findings reinforce the continuing evidence that physiological relationships are context-dependent and resource demands are dynamic across the reproductive season.

Male plumage colouration predicts female reproductive investment and nestling survival in a colour dimorphic tropical songbird

In sexually colour dimorphic bird species, males can exhibit phenotypic variation, with males breeding in either dull female-like plumage or brightly coloured plumage. Two contradictory hypotheses predict that the male phenotype variation can influence the female investment in a given breeding attempt. Whereas females usually prefer males in bright coloured plumage, the “differential allocation hypothesis” predicts that females should invest more in their reproductive output when mating with them; while the “compensatory investment hypothesis” predicts that females should invest more when mating with non-preferred males. To test those predictions, we analysed reproductive data for two consecutive breeding seasons (2018–2019 and 2019–2020) of Lined Seedeaters Sporophila lineola. S. lineola is a socially monogamous songbird species in which males exhibit two breeding phenotypes, a black-and-white plumage being the most common, and a less common female-like brownish plumage. Our findings show that females mated with brownish males have a higher reproductive investment (i.e., egg volume) than those mated with black-and-white males. Despite the lower investment of females in egg volume, our results showed that black-and-white males have a higher nestling survival, producing more hatchings and fledglings per season than brownish males, which could suggest a higher fitness. Our findings indicate that investment allocation on the eggs and offspring survival rates can be attributed to the plumage colour of males.

High Investment in Reproduction Is Associated with Reduced Life Span in Dogs.

AbstractProminent differences in aging among and within species present an evolutionary puzzle. The theories proposed to explain evolutionary differences in aging are based on the axiom that selection maximizes fitness, not necessarily life span. This implies trade-offs between investment in self-maintenance and investment in reproduction, where high investments in growth and current reproduction are associated with short life spans. Fast growth and large adult size are related to shorter life spans in the domestic dog, a bourgeoning model in aging research; however, whether reproduction influences life span in this system remains unknown. Here we test the relationship between reproduction and differences in life span among dog breeds, simultaneously controlling for shared ancestry and recent gene flow. We found that shared ancestry explains a higher proportion of the among-breed variation in life history traits, in comparison with recent gene flow. Our results also show that reproductive investment negatively impacts life span, and more strongly so in large breeds, an effect that is not merely a correlated response of adult size. These results suggest that basic life history trade-offs are apparent in a domestic animal whose diversity is the result of artificial selection and that among-breed differences in life span are due to a combination of size and reproduction.

Testing the migration syndrome: Comparative fecundity of migratory and non‐migratory nymphaline butterflies

AbstractEmpirical studies have shown a positive relationship between migration and fecundity, suggesting a ‘migration syndrome’ that also includes delayed reproduction and an extended reproductive lifespan. At the same time, life history theory predicts that the cost of migration should result in lower fecundity because both traits draw from a common resource.We test whether migration is associated with higher fecundity and delayed reproduction in five closely related butterfly species in the Nymphalini tribe. Two of these are migratory,Vanessa carduiandVanessa atalanta, and three are non‐migratory,Aglais urticae,Aglais io, andPolygonia c‐album, which appears in a diapausing and a non‐diapausing generation.Laboratory experiment of this study demonstrated a higher lifetime fecundity in the non‐migratory speciesA. urticaeandA. io, compared with the migratory species. When reproductive output was measured in terms of egg mass over adult female mass, also the non‐migratory speciesP. c‐albumhad a higher reproductive investment than the two migratory species, and the non‐diapausing generation had a higher reproductive output than the diapausing generation. All species butP. c‐albumdelayed reproduction until 5–7 days after eclosion/emergence.These results indicate that a migratory lifestyle carries a reproductive cost and suggests that the migratory habit has not resulted in selection for higher fecundity. However, the migratory species are highly fecund in a wider phylogenetic perspective, which leads to the conclusion that rather than selection having selected for high fecundity and delayed reproduction, these traits may be prerequisites for evolving a migratory lifestyle.

Fluctuations in Density-Dependent Selection Drive the Evolution of a Pace-of-Life Syndrome Within and Between Populations

AbstractThe pace-of-life syndrome (POLS) hypothesis posits that suites of traits are correlated along a slow-fast continuum owing to life history trade-offs. Despite widespread adoption, environmental conditions driving the emergence of POLS remain unclear. A recently proposed conceptual framework of POLS suggests that a slow-fast continuum should align to fluctuations in density-dependent selection. We tested three key predictions made by this framework with an eco-evolutionary agent-based population model. Selection acted on responsiveness (behavioral trait) to interpatch resource differences and the reproductive investment threshold (life history trait). Across environments with density fluctuations of different magnitudes, we observed the emergence of a common axis of trait covariation between and within populations (i.e., the evolution of a POLS). Slow-type (fast-type) populations with high (low) responsiveness and low (high) reproductive investment threshold were selected at high (low) population densities and less (more) intense and frequent density fluctuations. In support of the predictions, fast-type populations contained a higher degree of variation in traits and were associated with higher intrinsic reproductive rate (r0) and higher sensitivity to intraspecific competition (γ), pointing to a universal trade-off. While our findings support that POLS aligns with density-dependent selection, we discuss possible mechanisms that may lead to alternative evolutionary pathways.

New Insights into the Life-history Traits of the Night Shrimp Processa hemphilli (Caridea: Processidae) in the Western Atlantic.

We analyzed sexual dimorphism, sex ratio, relative growth, morphological sexual maturity, fecundity, embryo volume, and reproductive output of a population of the night shrimp Processa hemphilli from the Southeast coast of Brazil. Sampling was seasonally conducted, from June 2016 to April 2019 in Ubatuba, São Paulo. Our results showed the presence of sexual dimorphism in the body size, with females being larger than males. In addition, there was no difference in the overall sex ratio. However, it was possible to observe a skewed sex ratio to males in the smaller size classes, whereas females were more abundant in the larger size classes. The estimated carapace length at the onset of morphological sexual maturity of females and males was 3.6 mm and 3.2 mm, respectively. The mean fecundity of females was 285 ± 142 embryos (mean ± SD) embryos and was positively correlated with the carapace length. The embryo volume differed between the developmental stages with a constant increase in volume throughout the development between stages I and III. The mean reproductive output of females was 52.4%. Our results suggest that P. hemphilli have a pure search mating system, show sex allocation in the growth of body structures, and that females have high reproductive investment. All of these results represent the first insights into the life-history traits of the species in the western Atlantic and contribute to the knowledge about processid species.

If you encyst: evidence of parasite escape and host-switching among three co-occurring crabs

Biological invasions influence species interactions around the globe, including host and parasite communities. We evaluated trematode parasite diversity and the potential for host-switching of parasites in 3 co-occurring crabs in the Northeast USA, including 1 native species (Cancer irroratus) and 2 non-natives (Carcinus maenas, Hemigrapsus sanguineus), of which the former represents a historical and the latter a contemporary invader. At 7 sites from Maine to Rhode Island, we surveyed crabs for trematode infection prevalence and abundance, and the influence of parasitism on host body condition. We also conducted DNA sequencing using the 18S rRNA barcoding marker to determine species composition, diversity, and gene flow of trematode lineages among the co-occurring hosts. While the native host, C. irroratus, and the historical invader, C. maenas, exhibited no statistical difference in trematode prevalence, we found that C. maenas had a greater abundance of metacercarial cysts than the other 2 hosts, and the contemporary invader, H. sanguineus, was rarely infected. Crab condition did not vary with infection abundance, although infected females of all species had higher reproductive investment than other groups. Genetic analyses revealed that the microphallid trematodes consisted of 3 main clades, representing over 50 haplotypes, with evidence of host-switching by native parasites utilizing the non-native hosts. Given the importance of crustaceans to parasite life cycles, the introduction of novel hosts to these systems alters both free-living and host-parasite community interactions and could ultimately affect community structure and function. Future studies should continue to investigate host-parasite diversity and demographics following invasions to better understand impacts on native marine communities.

Assembleia de helmintos em uma pequena rã no semiárido brasileiro: relação parasito-hospedeiro-ambiente

ABSTRACT. Parasite infections may contingency different aspects of the hosts’ lives, and are usually expected to directly or indirectly compromise host reproduction. However, although amphibians have historically been study models in parasite ecology, the effects of parasitism on amphibians’ reproduction remain unknown. Thus, we investigated how the parasite load varies as a function of climatic seasonality (rainy and dry season) and intrinsic host characteristics (size and sex), as well as the relationship between parasite load and reproductive investment in males and females of a small frog (Pseudopaludicola pocoto Magalhães, Loebmann, Kokubum, Haddad & Garda, 2014) in the Brazilian semiarid region. The parasitological parameters of the studied population were not influenced by the season of the year or by the hosts’ body size, but females of P. pocoto had a higher prevalence and intensity of infection than males. The number of oocytes and the volume of the testes were not related to the parasite load, revealing that the parasitism did not negatively impact the gonadal investment in P. pocoto. Our findings suggest that short-lived species, such as the tiny Pseudopaludicola species, have a high reproductive investment independent of their parasitic interactions. In addition, this should be true mainly in those species that live in seasonally dry environments, such as P. pocoto, in which reproduction is even more constrained by the shortened and unpredictable rainy period.

Females restrict the position of domatia and suffer more herbivory than hermaphrodites inMyriocarpa longipes,a neotropical facultative myrmecophyte

AbstractDomatia are hollow structures in plants occupied by ant colonies, in turn ants provide protection against herbivores. In plants, competition for resources has driven sex-related changes in the patterns of resource allocation to life-history traits and defence traits. The resource-competition hypothesis (RCH) proposes that female plants due to their higher investment in reproduction will allocate fewer resources to defence production, showing greater herbivore damage than other sexual forms. We hypothesise the existence of sex-related differences in defensive traits of domatia-bearing plants, being female plants less defended due to differences in domatia traits, such as size, number of domatia and their position, exhibiting more herbivore damage than hermaphrodite plants ofMyriocarpa longipes, a facultative neotropical myrmecophyte. We found eight species of ants inhabiting domatia; some species co-inhabited the same plant, even the same branch. Our results are consistent with the predictions of RCH, as female plants had ant-inhabited domatia restricted to the middle position of their branches and exhibited greater herbivore damage in leaves than hermaphrodites. However, we did not find differences in domatia size and leaf area between sexual forms. Our study provides evidence for intersexual differences in domatia position and herbivory in a facultative ant–plant mutualism inM. longipes.We highlight the importance of considering the plant sex in ant–plant interactions. Differences in resource allocation related to sexual reproduction could influence the outcome of ant–plant interactions.

Enforced monoandry over generations induces a reduction of female investment into reproduction in a promiscuous bird.

While uncovering the costs and benefits of polyandry has attracted considerable attention, assessing the net effect of sexual selection on population fitness requires the experimental manipulation of female mating over generations, which is usually only achievable in laboratory populations of arthropods. However, knowing if sexual selection improves or impairs the expression of life‐history traits is key for the management of captive populations of endangered species, which are mostly long‐lived birds and mammals. It might therefore be questionable to extrapolate the results gathered on laboratory populations of insects to infer the net effect of sexual selection on populations of endangered species. Here, we used a longitudinal dataset that has been collected on a long‐lived bird, the houbara bustard, kept in a conservation breeding program, to investigate the effect of enforced monoandry on female investment into reproduction. In captivity, female houbara bustards are artificially inseminated with sperm collected from a single male (enforced monoandry), or sequentially inseminated with semen of different males (polyandry), allowing postcopulatory sexual selection to operate. We identified female lines that were produced either by monoandrous or polyandrous inseminations over three generations, and we compared reproductive investment of females from the two mating system groups. We found that females in the polyandrous lines had higher investment into reproduction as they laid more eggs per season and produced heavier hatchlings. Higher reproductive investment into reproduction in the polyandrous lines did not result from inherited differences from females initially included in the two mating system groups. These results show that removal of sexual selection can alter reproductive investment after only few generations, potentially hindering population fitness and the success of conservation breeding programs.

Invasion of pumpkinseed Lepomis gibbosus is facilitated by phenotypic plasticity across its invasion gradient

As a non-native species invades a new region, individuals at the range front are often characterised by differences in their traits and behaviours versus individuals in the established ‘core’ area. Here, differences in life history traits of invading pumpkinseed Lepomis gibbosus were assessed across a fine spatial scale in the Saricay Stream, Turkey, with seven locations sampled between their core area and the invasion front. Following genetic analyses that suggested the pumpkinseed all originated from the same founding population, life history trait analyses revealed pronounced differences between the sites at the core and front that were independent of environmental factors. Pumpkinseed in sites towards the invasion front were of relatively low abundance and displayed relatively high reproductive investment, with heavier gonads, higher fecundity and smaller eggs. They also had faster growth rates than pumpkinseed in sites towards the core of the invasion. The traits displayed by pumpkinseed at sites in the mid-range were intermediate between the extremes displayed by fish at core and frontal sites. These results suggested high plasticity in life history traits of these pumpkinseed across this fine-scale invasion gradient and was considered to be most likely due to responses to low intra-specific competition at the invasion front that had shifted selective pressures towards higher investment in somatic growth and reproduction.

Relationships between Haemosporidian Infection and Parental Care in a Cooperative Breeder, the Iberian Magpie Cyanopica cooki

El periodo reproductivo, una etapa clave en la historia de la vida animal, supone un alto gasto de energia y a menudo existe la posibilidad de que las infecciones parasitarias puedan comprometer su exito. Puesto que las defensas antiparasitarias son tambien costosas de producir, los individuos deben optimizar el destino de los recursos limitados disponibles entre las actividades reproductivas o al automantenimiento, p. ej. apoyando la funcion inmunologica y manteniendo la masa corporal. Aqui exploramos las relaciones entre el estado de infeccion por hemosporidios, la condicion corporal y la tasa de alimentacion de pollos en ayudantes, hembras reproductoras y machos reproductores de un corvido con cria cooperativa, el rabilargo iberico Cyanopica cooki. Para el estado de infeccion, diferenciamos entre aves no infectadas y, por separado, aquellas infectadas con uno o mas de un linaje parasitario del genero Leucocytozoon. Nuestras predicciones fueron que tanto los rabilargos reproductores como los ayudantes con una infeccion mixta por hemosporidios deberian mostrar una condicion corporal y tasas de alimentacion de pollos mas bajas que las aves no infectadas o con infeccion simple. Encontramos que la mayoria de los rabilargos estudiados (78,7%) estaban infectados con especies del genero Leucocytozoon, la mayoria de ellas (67,1% de los individuos infectados con Leucocytozoon) presentando infecciones mixtas. El indice de masa corporal escalado no difirio con respecto al estado de infeccion en reproductores machos o hembras; sin embargo, los ayudantes infectados mixtos mostraron una condicion corporal mas baja que los infectados simples. Ademas, encontramos que los machos con una infeccion mixta, asi como las hembras reproductoras con infeccion simple y mixta, pero no los ayudantes infectados, mostraron tasas de alimentacion de pollos mas bajas que los individuos no infectados. Estos hallazgos podrian indicar un compromiso entre las funciones reproductiva e inmunologica en el rabilargo iberico, efecto que se hace mas evidente en aquellos individuos con mayor inversion reproductiva durante el periodo de cria.

Prolific pioneers and reserved settlers. Changes in the life-history of the western tubenose goby (Proterorhinus semilunaris) at different invasion stages

The western tubenose goby is one of the most wide-spread invasive fish species in European freshwaters, though information of its life-history in relation to its invasion success is limited. We compared the reproductive traits, growth rate and condition of three populations that differed in their stage of invasion in its expanding range in the River Vistula: core - the oldest population established at the centre of the invasive range; intermediate - long established by downstream dispersal from the core area but continuously supplemented by drifting specimens; front - new population at the edge of the invasive range, upstream from the core area. Pronounced differences in life-history traits were found between the ‘core’ and the ‘front’ populations. The ‘front’ population displayed high investment in reproduction and had heavier gonads, higher fecundity, higher batch fecundity though smaller eggs than the ‘core’ population. The ‘core’ population was characterized by the lowest fecundity, the largest eggs, the highest condition after spawning, and the highest maximum age of males. The ‘intermediate’ population was intermediate between the ‘front’ and the ‘core’ populations regarding reproductive traits, but showed the highest growth rates. The life-history traits that varied most among populations were gonad weight, fecundity, gonado-somatic index, condition and growth in the first years of life. Inter-individual variability of life-history traits was lower in the front of the invasive range than in the core and intermediate area. The observed plasticity in life-history appears to favour production of large numbers of offspring in newly-colonised areas in the initial stages of invasion and at the edge of the expanding range. In longer-established populations, at the core of invasive range, a strategy for greater competitiveness under intra-specific competition appears to be favoured.

Selection for Divergent Reproductive Investment Affects Neuron Size and Foliation in the Cerebellum

The cerebellum has a highly conserved internal circuitry, but varies greatly in size and morphology within and across species. Despite this variation, the underlying volumetric changes among the layers of the cerebellar cortex or their association with Purkinje cell numbers and sizes is poorly understood. Here, we examine intraspecific scaling relationships and variation in the quantitative neuroanatomy of the cerebellum in Japanese quail (Coturnix japonica) selected for high or low reproductive investment. As predicted by the circuitry of the cerebellum, the volumes of the constituent layers of the cerebellar cortex were strongly and positively correlated with one another and with total cerebellar volume. The number of Purkinje cells also significantly and positively co-varied with total cerebellar volume and the molecular layer, but not the granule cell layer or white matter volumes. Purkinje cell size and cerebellar foliation did not significantly covary with any cerebellar measures, but differed significantly between the selection lines. Males and females from the high-investment lines had smaller Purkinje cells than males and females from the low-investment lines and males from the high-investment lines had less folded cerebella than quail from the low-investment lines. These results suggest that within species, the layers of the cerebellum increase in a coordinated fashion, but Purkinje cell size and cerebellar foliation do not increase proportionally with overall cerebellum size. In contrast, selection for differential reproductive investment affects Purkinje cell size and cerebellar foliation, but not other quantitative measures of cerebellar anatomy.