Nesting Behavior Research Articles

Notas sobre a bionomia de Tetragonisca weyrauchi schwarz, 1943 (Apidae, MeliponinI)

No Brasil, a abelha sem ferrão, Tetragonisca weyrauchi tem sua distribuição restrita à região Amazônica. Constrói ninhos aéreos freqüentemente em forquilhas inclinadas de árvores. Os ninhos, cilindróides e verticais, medem cerca de 60cm de circunferência na parte mais larga e 35cm de altura. A cobertura é de uma película fina e maleável com diferentes consistências. A maioria dos ninhos apresenta, na parte superior, um prolongamento com várias protuberâncias e aberturas, ou só aberturas, com diâmetros milimétricos variáveis ao longo do dia, denominado aqui de respiráculo. A morfologia do ninho, com a porta na parte inferior e o respiráculo na parte superior, parece estar bem adaptado ao ambiente tropical em que se encontra. As médias das temperaturas internas de um ninho habitado e outro vazio acompanharam as flutuações ambientais com alto valor de correlação (r=0,98). Os resultados sugerem que a estrutura física do ninho seria responsável por uma pequena parcela na retenção da energia calorífera. Se existe termorregulação, ela deve ser mais evidente acima dos 33ºC ambientais, temperatura onde ocorreu tendência de estabilidade. A grande quantidade de lamelas de cerume ao redor dos favos de cria horizontais, o tamanho dos potes ovóides de alimento ao redor de 1-2 cm de altura, a porcentagem de água no mel ao redor de 27.6%, o aspecto do tubo de entrada com pequenos orifícios, os valores de temperatura em que ocorre a abertura desse tubo pela manhã, entre 21-23ºC, e as coletas de néctar, predominantemente em Myrtacea, fazem com que seja atribuída grande semelhança física e comportamental entre T.weyrauchi e T. angustula. Os ninhos se adaptam bem em colônias tipo Paulo Nogueira-Neto. São abelhas agressivas quando manuseadas. Estima-se que seus ninhos tenham uma população de 2000-3000 indivíduos.

Does the distance between nest clusters affect reproductive success in Ammophila sabulosa (Hymenoptera Sphecidae)?

A population of Ammophila sabulosa (Linnaeus 1758) in the Upper Valtellina (Northern Italy) was observed during in 1996. The 20 females object of this study dug a total of 120 nests. Each A. sabulosa nest was opened after the provisioning and at the end of the season, to check the status of prey, A. sabulosa larvae and pupae and the loss of brood due to biological factors. We found that 69.2% of the 120 nests were provisioned, but the larvae pupated in only 29.1% of provisioned nests. Brood loss was due to parasitism by Diptera Sarcophagidae and Hymenoptera Ichneumonidae (3.6% of provisioned nests), to cleptoparasitism by conspecific females (14.4% of provisioned nests) and to mites and nematodes (49.3% of provisioned nests). Using a new approach in entomology research, the nest clusters of different females were compared by means of distance weighted centroids, to evaluate the influence of nest cluster distances on reproductive success. Based on our observations, intraspecific parasitism is a common phenomenon among adjacent nests clusters: the distances among nest clusters of the females whose nests were parasitized by conspecifics are significant lower than the distances among nest clusters of females whose nest were not parasitized by conspecifics. Interestingly, intraspecific parasitism was not affected by nest densities, defined as the number of nests within the nest cluster. In conclusion, we believe that the novel technique of nests examination we introduced, provides a valid tool for studying nesting behaviour in wasps with shallow ground nests like A. sabulosa.

Colonização e biologia reprodutiva de mamangavas (Xylocopa frontalis) em um modelo de ninho racional

As mamangavas (Xylocopa spp.) são importantes polinizadores, mas o seu criatório para introdução em áreas agrícolas tem sido dificultado pelo hábito de nidificação dessas abelhas. Propostas de ninhos racionais, que possibilitem a observação do seu interior, manejo e transporte para os pomares, não têm sido bem aceitas pelas abelhas. O presente trabalho testou a colonização e biologia reprodutiva das mamangavas em um modelo sugerido por FREITAS & OLIVEIRA (2001). O resultado mostrou colonização por X. frontalis em taxas entre 18,75 e 52,22%, com 3,0 a 4,7 ninhos povoados por caixa. A arquitetura dos ninhos construídos foi semelhante ao observado em ninhos silvestres e o ciclo de ovo a adulto levou, em média, 45,58 dias. A relação macho/fêmea das crias foi de 0,60 : 1,00. Conclui-se que o modelo de caixa racional testado apresenta boa aceitação por X. frontalis e não afeta a biologia reprodutiva dessa abelha.

A Role for Calcineurin Dysfunction in Schizophrenia?

Schizophrenia, a form of mental illness that affects about 1% of the population, is believed to depend on a complex and incompletely understood interplay of genetic and environmental factors. Two related articles provide evidence suggesting that alterations in signaling from the serine-threonine phosphatase calcineurin may contribute to the pathogenesis of this severe and disabling disease. Miyakawa et al. subjected a strain of mutant mice that lacked forebrain calcineurin to a battery of tests and observed a spectrum of behavioral abnormalities reminiscent of those found in individuals with schizophrenia. The authors, who had previously noted deficits in working memory in these mice, observed decreased social interaction, impaired attention, and impaired nesting behavior. The mice also displayed increased hyperactivity, which is characteristic of other animal models of schizophrenia, and enhanced susceptibility to N -methyl-D-aspartate receptor blockade. In an accompanying article, Gerber et al. demonstrated that the PPP3CC gene, which encodes the calcineurin γ catalytic subunit, mapped to a chromosomal locus previously associated with susceptibility to schizophrenia and displayed a polymorphism that resulted in a nonconservative change in amino acid sequence. Genetic analysis of families affected with schizophrenia suggested that variations in PPP3CC could increase susceptibility to the disease. The authors discuss possible mechanisms whereby abnormalities in calcineurin signaling could predispose to the pathogenesis of schizophrenia. T. Miyakawa, L. M. Leiter, D. J. Gerber, R. R. Gainetdinov, T. D. Sotnikova, H. Zeng, M. G. Caron, S. Tonegawa, Conditional calcineurin knockout mice exhibit multiple abnormal behaviors related to schizophrenia. Proc. Natl. Acad. Sci. U.S.A. 100 , 8987-8992 (2003). [Abstract] [Full Text] D. J. Gerber, D. Hall, T. Miyakawa, S. Demars, J. A. Gogos, M. Karayiorgou, S. Tonegawa, Evidence for association of schizophrenia with genetic variation in the 8p21.3 gene, PPP3CC , encoding the calcineurin gamma subunit. Proc. Natl. Acad. Sci. U.S.A. 100 , 8993-8998 (2003). [Abstract] [Full Text]

A Role for Calcineurin Dysfunction in Schizophrenia?

Schizophrenia, a form of mental illness that affects about 1% of the population, is believed to depend on a complex and incompletely understood interplay of genetic and environmental factors. Two related articles provide evidence suggesting that alterations in signaling from the serine-threonine phosphatase calcineurin may contribute to the pathogenesis of this severe and disabling disease. Miyakawa et al. subjected a strain of mutant mice that lacked forebrain calcineurin to a battery of tests and observed a spectrum of behavioral abnormalities reminiscent of those found in individuals with schizophrenia. The authors, who had previously noted deficits in working memory in these mice, observed decreased social interaction, impaired attention, and impaired nesting behavior. The mice also displayed increased hyperactivity, which is characteristic of other animal models of schizophrenia, and enhanced susceptibility to N-methyl-D-aspartate receptor blockade. In an accompanying article, Gerber et al. demonstrated that the PPP3CC gene, which encodes the calcineurin γ catalytic subunit, mapped to a chromosomal locus previously associated with susceptibility to schizophrenia and displayed a polymorphism that resulted in a nonconservative change in amino acid sequence. Genetic analysis of families affected with schizophrenia suggested that variations in PPP3CC could increase susceptibility to the disease. The authors discuss possible mechanisms whereby abnormalities in calcineurin signaling could predispose to the pathogenesis of schizophrenia.T. Miyakawa, L. M. Leiter, D. J. Gerber, R. R. Gainetdinov, T. D. Sotnikova, H. Zeng, M. G. Caron, S. Tonegawa, Conditional calcineurin knockout mice exhibit multiple abnormal behaviors related to schizophrenia. Proc. Natl. Acad. Sci. U.S.A. 100, 8987-8992 (2003). [Abstract] [Full Text]D. J. Gerber, D. Hall, T. Miyakawa, S. Demars, J. A. Gogos, M. Karayiorgou, S. Tonegawa, Evidence for association of schizophrenia with genetic variation in the 8p21.3 gene, PPP3CC, encoding the calcineurin gamma subunit. Proc. Natl. Acad. Sci. U.S.A. 100, 8993-8998 (2003). [Abstract] [Full Text]

Colonial nesting behaviour in Indian Pond Heron (Ardeola grayii grayii) of Bangladesh

A study was conducted on the nesting behaviour of Indian Pond Heron in Sitakunda, southeastern region of Bangladesh between January, 1995 and December, 1996. Indian Pond Heron is a solitary bird on its feeding grounds. It forms colonies when nesting. Eight species of plants were used for nest building in three colonies. Colonial nesting is an anti-predator adaptation in the Indian Pond Heron.

Frustrated nesting behaviour: Relation to extra-cuticular shell calcium and bone strength in White Leghorn hens

1. The inability of hens to express normal nesting behaviour in battery cages results in frustration, manifesting itself as stereotyped pacing. Frustration can cause hens to retain their eggs beyond the expected time of lay, resulting in an extra-cuticular layer of calcium on eggshells. 2. This study investigated whether frustrated nesting behaviour caused extra-cuticular calcification of eggshells and whether this loss of non-structural calcium to eggshells may have subsequently contributed to weak bones in spent hens. 3. One hundred and twenty hens were assigned to one of three treatments: NB (hens given nest boxes in their cages), NN (no nest box) and R (access to nest box periodically restricted). 4. NB hens spent the least amount of time pacing in the hour before oviposition. NN and R hens spent similar amounts of time pacing. 5. Contrary to expectation, eggshells from hens under different treatments yielded the same amount of extra-cuticular calcium. Similarly tibia strength did not significantly differ among treatments.

Assured fitness returns favor sociality in a mass-provisioning sweat bee, Megalopta genalis (Hymenoptera: Halictidae)

Assured fitness returns models for the evolution of sociality emphasize the selective value of ensuring that offspring receive adequate parental care to reach maturity. If a member of a social group dies, it can accrue returns on investment in offspring through the efforts of surviving social partners. We provide evidence that in the mass-provisioning, facultatively social sweat bee Megalopta genalis, adult presence in the nest throughout brood development provides protection from ant predation. Nests with adults present were well protected, and brood in nests with adults removed suffered higher predation. Females in observation nests showed effective defensive behavior against experimentally introduced ants, and bees in natural nests repulsed naturally occurring ant raids. Megalopta nest architecture and behavior are such that the brood of several cooperating females can be defended with little additional cost relative to solitary nesting. The benefits of cooperative defense may favor group living in mass provisioning bees. Our observations and experiments suggest that parental care throughout brood development can be adaptive in mass provisioning species, supporting the predictions of assured fitness returns models.

Nesting in textile laminates: geometrical modelling of the laminate

The nesting of reinforcements in textile laminates is studied using a 3D geometrical model of a woven, braided and non-crimp stitched fabrics in the relaxed and sheared state. The following fabric parameters were varied in the numerical experiments: flatness of the yarns, tightness and balance of the fabric, fabric weaving/braiding/knitted pattern, number of layers and degree of shear. Monte-Carlo modelling of the random nesting generated data on the influence these parameters on the average laminate thickness and fibre volume fraction and distributions of these characteristics of the laminate. The results show that the nesting effect becomes more pronounced with the decrease of the fabric tightness and the decrease of the float length in the weave. For non-circular yarns, an average dimension of the cross-section proved to be a valid normalizing parameter to generalize the nesting behaviour of fabrics. Shear deformation of the fabric decreases the nesting. For non-crimp stitched fabrics the nesting is defined by the stitching pattern.

AVIAN POPULATION TRENDS WITHIN THE EVOLVING AGRICULTURAL LANDSCAPE OF EASTERN AND CENTRAL UNITED STATES

Abstract State-level Breeding Bird Survey (1980–1998) and U.S. Department of Agriculture statistics were used to test the hypothesis that changes in agricultural land use within the eastern and central U.S. have driven population trends of grassland and shrub habitat birds over the past two decades. The degree to which population trends differed between grassland and shrub habitats was evaluated with respect to migratory and nesting behavior. Grassland birds declined significantly between 1980 and 1999, but, on average, shrub habitat species did not. Grassland-breeding, long-distance migrants exhibited the strongest negative trends. Most species (78%; n = 63) exhibited at least one significant association between population trends and changes in agricultural land use, and in most, land use “explained” 25–30% of the variation in population trends among states. Changes in the farmland landscape accounted for more of the interstate variability of population trends of short-distance migrants than of both long...

Avian Population Trends Within the Evolving Agricultural Landscape of Eastern and Central United States

Abstract State-level Breeding Bird Survey (1980–1998) and U.S. Department of Agriculture statistics were used to test the hypothesis that changes in agricultural land use within the eastern and central U.S. have driven population trends of grassland and shrub habitat birds over the past two decades. The degree to which population trends differed between grassland and shrub habitats was evaluated with respect to migratory and nesting behavior. Grassland birds declined significantly between 1980 and 1999, but, on average, shrub habitat species did not. Grassland-breeding, long-distance migrants exhibited the strongest negative trends. Most species (78%; n = 63) exhibited at least one significant association between population trends and changes in agricultural land use, and in most, land use “explained” 25–30% of the variation in population trends among states. Changes in the farmland landscape accounted for more of the interstate variability of population trends of short-distance migrants than of both long-distance migrants and residents, and that variability was greater in grassland than shrub species. Declines in the area of rangeland and cover crops were followed by population declines and increases, respectively, by many species. Increases of land in the Conservation Reserve Program had negative associations with population trends of some shrub species. The results indicate that grassland birds have declined strongly over the past two decades, and that regardless of migratory behavior or nesting habits, avian population trends are linked strongly to changes in agricultural land use within North America.

Nesting Behavior of Palila, as Assessed from Video Recordings

We quantified nesting behavior of Palila (Loxioides bailleui), an endangered Hawaiian honeycreeper, by recording at nests during three breeding seasons using a black-and-white video camera connected to a videocassette recorder. A total of seven nests was observed. We measured the following factors for daylight hours: percentage of time the female was on the nest (attendance), length of attendance bouts by the female, length of nest recesses, and adult provisioning rates. Comparisons were made between three stages of the 40-day nesting cycle: incubation (day 1–day 16), early nestling stage (day 17–day 30 [i.e., nestlings ≤14 days old]), and late nestling stage (day 31–day 40 [i.e., nestlings > 14 days old]). Of seven nests observed, four fledged at least one nestling and three failed. One of these failed nests was filmed being depredated by a feral cat (Felis catus). Female nest attendance was near 82% during the incubation stage and decreased to 21% as nestlings aged. We did not detect a difference in attendance bout length between stages of the nesting cycle. Mean length of nest recesses increased from 4.5 min during the incubation stage to over 45 min during the late nestling stage. Mean number of nest recesses per hour ranged from 1.6 to 2.0. Food was delivered to nestlings by adults an average of 1.8 times per hour for the early nestling stage and 1.5 times per hour during the late nestling stage and did not change over time. Characterization of parental behavior by video had similarities to but also key differences from findings taken from blind observations. Results from this study will facilitate greater understanding of Palila reproductive strategies.

Behavioral responses of males to estradiol-treated females in the budgerigar (Melopsittacus undulatus)

We investigated the effects of estradiol-treated females on the behavior of male budgerigars. In comparison to control females, females given implants of estradiol showed elevated nest behavior and darker cere color, which are characteristics of breeding females. After we confirmed the efficacy of estradiol treatment on behavior and morphology, each female was paired with a male mate. Males paired with estradiol-treated females showed more courtship behavior (auditory and visual display, and courtship feeding) to their mates than males paired with control females. These data indicate that budgerigar females with a high estrogen level enhance males' courtship behavior. Since males did not show response to estradiol-treated females soon after females were introduced, effects of estradiol-treated female budgerigars may be mediated by the endocrine system, rather than wholly by the nervous system, of males.

Temporal and Spatial Quantitation of Nesting and Mating Behaviors among Mice Housed in a Semi-Natural Environment

Enhanced behavioral complexity may be observed when animals are tested in naturalistic environments and engaging in nonforced social interactions. For each of six experimental runs, different groups of five adult Swiss-Webster mice (four ovariectomized females and a single male) were maintained under 12h dark:12h light in a 122 × 122 × 30.5-cm open box containing six peripheral “nestboxes.” On Day 1, females were released into the box first and their nesting behavior was observed. Two days later, each female was injected with estradiol benzoate and the male was introduced into the environment. Females were injected with progesterone (P) 48 h later and the animals were observed for an additional 14 h. Behaviors were recorded with a video camera suspended over the apparatus. Mating occurred only post-P and males always mated preferentially with certain females. The amount of nesting behavior per female on Day 1 correlated significantly with the number of times each female was mated by the male ( r = 0.57, P < 0.005). In all but one run, the male ejaculated with the female who performed the most nesting behavior. While 63% of mating was in the open, 56% of nestbox matings resulted in female postmating darting to alternate nestboxes; in 19% of these cases, the female quickly returned to the mating nestbox and was mated there again. Direct approaches by females to the male and behaviors which affect pacing were observed. These behaviors have not been reported previously for mice and may provide additional endpoints for the exploration of hormonal and genetic influences on reproductive behaviors.

Nest provisioning and a possible cost of reproduction in the megachilid bee Osmia rufa studied by a new observation method

Parental care is thought to increase offspring success but entails a cost in terms of a decrease in the parent's ability for subsequent reproduction. Females of most bees and wasps show extensive parental care. Thus, they are ideal organisms to study the expenditure for offspring production and the resulting costs of reproduction. We examined parental behaviour in the solitary bee Osmia rufa (Linné 1758) (Hymenoptera Megachilidae) by use of a new method that allows observation of within nest behaviour and quantification of most aspects of nest construction and provisioning. The method does not cause disturbance of provisioning females and does not increase immature mortality. To characterise maternal expenditure we recorded the number of foraging trips and the time spent for one brood cell, the duration of single foraging trips to gather provisions and loam (for brood cell partitions), and the amount of provisions and loam gathered per trip. We predicted that, due to the large expenditure for provisioning, females would loose weight in the course of the flight season. Alternatively, a weight loss could be caused by decreasing ambient temperatures and a shortage of food resources. Our results show that female O. rufa lost mass towards the end of the flight season. Though ambient temperatures had some effect, the high expenditure for reproduction were probably the major cause of the weight loss. The weight loss was independent of the rate of brood cell construction but was significantly more pronounced in smaller females. Thus, if the weight loss represents a cost of reproduction our results suggest that the magnitude or type of cost might vary among individuals.

Father nose best

Olfaction is the main sensory modality for many animals, but the importance of smell to humans is not so clear. However, a number of researchers have demonstrated that the human sense of smell, similar to that of many animals, might form part of the individual recognition and mate choice processes, albeit at a subconscious level. The mechanism by which the distinct odour of an individual arises is due in part to the highly polymorphic human leukocyte antigen (HLA) loci. The HLA are the human equivalent of the major histocompatibility complex (MHC), which influence a number of olfactory-related behaviours in rodents, including nesting, pregnancy block, individual recognition and mate choice.It is generally thought that most animals, including humans, base much of their odour preference on their own odour and those odours to which they were exposed as infants. However, there is some evidence for a heritable component to odour preference, although a genetic effect is difficult to prove owing to the many environmental variables that not only influence the preference, but also the odour production. In addition, the high level of variation at the HLA loci in the general population also adds complications to a genetic analysis in humans. However, a recent study [1xPaternally inherited HLA alleles are associated with women's choice of male odor. Jacob, S et al. Nat. Genet. 2002; 30: 175–179Crossref | PubMed | Scopus (273)See all References][1] demonstrates that there is indeed a genetic influence on odour preference in humans and, by using members of an isolated community of German–Austrian descent, the researchers were able to investigate how this choice varied with a limited number of HLA alleles.Females were asked to report on the ‘familiarity’, ‘intensity’, ‘pleasantness’ and ‘spiciness’ of the odours from males from a wide-range of ethnic backgrounds. What was evident was that the women preferred the odours of those males whose HLA most closely matched their own (although they did not perceive these as familiar). However, in a subtle twist, the preference was not just for similar HLA to their own, but for odours that came from individuals with similar HLA alleles to those that the women had inherited from their fathers; that is, a paternal effect. Additionally, the authors show that this effect has a genetic basis, as the preference co-varies only with those HLA alleles the women inherited from their father, rather than all the HLA alleles their fathers possess.This indicates a genetic parent-of-origin effect (POE) on odour preference, a phenomenon that can most readily be explained by genomic imprinting. Interestingly a study using mice [2xUrinary odour preferences in mice. Isles, A.R et al. Nature. 2001; 409: 783–784Crossref | PubMedSee all References][2] produced results that are strikingly similar to those of Jacob et al. In this investigation both male and female mice were shown to prefer paternal odour cues and this preference was also subject to a genetic POE. Although it is difficult to determine a mode of action for these POEs, what is germane is that this phenomenon could be an underlying mechanism behind kin-biased behaviour, such as mate choice, communal nesting and social behaviour in species as diverse as mouse and man.

IMPACT OF NEST-SITE SELECTION ON NEST SUCCESS AND NEST TEMPERATURE IN NATURAL AND DISTURBED HABITATS

Nest-site selection behavior is a maternal effect that contributes to offspring survival and variation in offspring phenotypes that are subject to natural selection. We investigated nest-site selection and its consequences in the snapping turtle, Chelydra serpentina, in northwestern Illinois. We evaluated nest-site selection at both the microhabitat and habitat patch levels. Turtles selected nest sites with shorter vegetation, more open sand, and fewer cacti than random locations. These microhabitat characteristics described sandy patches where both nest density and success were higher compared to grassy patches in 1999. We subsequently investigated nest-site selection within two discrete subdivisions of the study area that varied in the degree of human disturbance to determine if nesting behavior, nest success, or nest temperatures were affected. The tendency to nest in sandy patches was much stronger at the natural site due to habitat modifications at the residential site that have blurred the distinction between sandy and grassy patches. Additionally, the residential site had a high density of nests within 5 m of houses and a fence (both areas with disturbed habitat similar to sandy patches), compared to the overall density. Thus, nest success associated with sandy patches may be compromised at the residential site; an ecological trap may result in lower nest success in areas with preferred microhabitat characteristics. Despite a similar basis for nest-site selection in terms of microhabitat characteristics at both sites, nest temperatures were correlated with microhabitat characteristics used to select nest sites only at the natural site. Nest temperatures at the residential site were instead correlated only with the percentage overstory vegetation cover and therefore averaged 2°C lower than at the natural site, a temperature difference that influenced offspring sex. The higher percentage overstory vegetation cover at the residential site was due to human alterations of the habitat, and may serve to extend the ecological trap biasing the sex ratio of this population. This study illustrates the importance of (1) nest-site selection as a substantive maternal effect, (2) understanding habitat use during crucial life-history events, and (3) the potential for human disturbance to modify offspring phenotypes and negatively impact nest success despite adaptive nesting behavior.

CLASSIFICATION OF ARTIFICIAL CHANGE PATTERN OF SPAWNING SITE OF LOGGERHEAD TURTLE CARETTA CARETTA AND SOME CONSIDERATIONS

Human-induced alterations were investigated at sixty sea turtle nesting sites based on field surveys. Alterations were classified into 6 types due to the effects to the nesting behavior of loggerhead turtle Caretta caretta. The 63% of the nesting sites are suffering from decrease of nesting areas caused by construction of seawall, beach erosion and excess usage of back-shore. In order to monitor and restore sandy beaches, cooperation between amateur turtle surveyors and coastal engineers is required.

Repeatability of microenvironment-specific nesting behaviour in a turtle with environmental sex determination

Evolutionary thermal adaptation is increasingly being elucidated in a variety of systems. However, one of the most striking examples, temperature-dependent sex determination (TSD) in reptiles, has proven stubbornly difficult to decipher. Theoretical models suggest that selection on and heritable variation in thermal sensitivity of embryonic sex determination and maternal behavioural choice of thermal qualities of nest sites control the microevolutionary potential of TSD. To begin addressing this important issue, we conducted a multiyear field study of nesting behaviour in painted turtles (Chrysemys picta), which display TSD. We detected a significant field repeatability for overstory vegetation cover around nests at oviposition, a trait that is correlated inversely with nest temperature during embryonic sex determination and positively with offspring sex ratio (percentage of male). Neither clustered nesting nor individual spatial repeatability in nest site choice caused this striking pattern. Instead, females consistently preferred nest environments with particular quantities of overstory vegetation cover. These findings confirm a crucial assumption of models concerning the microevolution and adaptive significance of TSD in reptiles. The results also indicate that this system may be able to evolve via long-term maternal nesting behaviour in response to skewed sex ratios caused by environmental perturbations, such as gradual long-term climate change.

Exact analysis of the cache behavior of nested loops

We develop from first principles an exact model of the behavior of loop nests executing in a memory hicrarchy, by using a nontraditional classification of misses that has the key property of composability. We use Presburger formulas to express various kinds of misses as well as the state of the cache at the end of the loop nest. We use existing tools to simplify these formulas and to count cache misses. The model is powerful enough to handle imperfect loop nests and various flavors of non-linear array layouts based on bit interleaving of array indices. We also indicate how to handle modest levels of associativity, and how to perform limited symbolic analysis of cache behavior. The complexity of the formulas relates to the static structure of the loop nest rather than to its dynamic trip count, allowing our model to gain efficiency in counting cache misses by exploiting repetitive patterns of cache behavior. Validation against cache simulation confirms the exactness of our formulation. Our method can serve as the basis for a static performance predictor to guide program and data transformations to improve performance.