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Mireia Esparza
Faculty of Biology of the Universitat de Barcelona
Department of Animal Biology (Anthropology)
Spain

A comparison between heritabilities of life history and morphological traits in human populations

poster 

Author(s): Esparza, M, Martínez-Abadías, N, Sjovold, T, González-José, R, Hernández, M

Summary:

According to Fisher's fundamental theorem of natural selection, the amount of additive genetic variance in a trait, and hence its heritability, should decrease as the strength of selection on this trait increases. Supporting this idea, many authors have reported lower heritability values in life history traits than in morphological and physiological traits for different species. But there are no studies comparing the evolvability of different types of traits in human populations. The pedigree collection of decorated skulls from the historical population of Hallstatt (Austria) offers an exceptional opportunity to compare the heritabilities of life history and morphological traits in humans. In this study we first used church records to reconstruct the pedigrees and to obtain the values of individual life history traits, such as fertility, age at first and at last child, mean interbirth interval, adult lifespan and lifetime reproductive success). Second, we measured a sample of 353 complete adult skulls falling into the pedigreesusing a 3D Microscribe digitizer. A set of 50 landmarks were measured on each skull and from the 3D landmarks coordinates we estimated several size and shape variables reflecting the complex and modular structure of the human skull. We estimated the heritabilities of the life-history and morphological traits using a Restricted Maximum Likelihood method and statistically compared the resulting heritability values. On average, our results show lower heritabilities for life history traits than for morphological ones, confirming the initial hypothesis.

Hannah Dugdale
University of Sheffield
Animal and Plant Sciences
United Kingdom

Age-specific breeding success in a wild mammalian population: selection, constraint, restraint and senescence

poster 

Author(s): Dugdale, HL, Lisa, PC, Newman, C, Macdonald, DW, Burke, T

Summary:

The Selection, Constraint, Restraint, and Senescence Hypotheses predict how breeding success should vary with age. The Selection Hypothesis predicts between-individual variation arising from quality differences; the other hypotheses predict within-individual variation due to differing skills or physiological condition (Constraint), residual reproductive lifespan (Restraint), or somatic and reproductive investment (Senescence). Studies tend to focus on either the initial increase in breeding success or later decrease; however, both require consideration when unravelling the underlying evolutionary processes. Additionally, few studies present genetic fitness measures, and rarely for both sexes. We therefore test these four hypotheses, which are not mutually exclusive, in a high-density population of European badgers Meles meles. Using an 18-year dataset (including 22 microsatellite loci) we show an initial improvement in breeding success with age, followed by a later and steeper rate of reproductive senescence in males than in females. Breeding success was skewed within age-classes indicating the influence of factors other than age-class. This was partly attributable to selective appearance and disappearance of badgers (Selection Hypothesis). Individuals with a late age of last breeding showed a concave down relationship between breeding success and experience (Constraint Hypothesis). There was no evidence of abrupt terminal effects; rather, individuals showed a concave down relationship between breeding success and residual reproductive lifespan (Restraint Hypothesis), with an interaction with age of first breeding only in females. Our results demonstrate the importance of investigating a comprehensive suite of factors in age-specific breeding success analyses, in both sexes, in order to fully understand evolutionary and population dynamics.

Ulrich Steiner
Max-Planck Odense Centre on the Biodemography of Aging
University of Southern Denmark, Insitute of Biology
Denmark

AgeGuess crowdsourcing human aging research

poster 

Author(s): Steiner, U, Misevic, D

Summary:

Human lifespan increases by 2.5 years every decade. This unprecedented change in life histories poses fundamental challenges for evolutionary theories. Some evidence indicates that this change is due to a delay in aging rather than a change in the rate of aging. AgeGuess is a citizen science project and online game that investigates the differences between perceived age (how old you look to other people) and chronological age (how old you actually are) and their potential power as an aging biomarker. Is the increased life expectancy reflected in how old one looks, i.e. are the new 60’s the old 50’s? Are people who look older than they are more likely to die early? Does the rate of looking older differ among individuals or some individuals just looking older all their lives, i.e. does the difference between estimated and real age change over time? Is the difference between perceived and real age heritable? Are there periods in life when one ages faster? The project aims at such questions by a simple on-line game in which you can post your photos, have other people guess your age, as well as guess the age of other users. Curious? Please visit AgeGuess.org

Jenni Pettay
University of Turku
Section of Ecology
Finland

Cooperation and conflict in humans in traditional large joint families

poster 

Author(s): Pettay, JE, Lahdenperä, M, Lummaa, V

Summary:

Group living can be associated with cooperation and even cooperative breeding whereby non-reproductive individuals help to raise offspring that are not their own. However, it can also lead to evolutionary conflict, which is a less studied phenomenon. Humans are considered to be cooperative breeders, since mothers commonly gain help in raising offspring from other (usually related) group members, such as grandmothers and siblings. Nevertheless, simultaneous breeding in the same household among reproductive-aged females, such as mothers-in-law and daughters-in-law, has also been linked with reduced success. The importance of cooperation and conflict is likely to vary according to ecology and social structure of populations, leading to differential selection pressures on dispersal patterns. We used life-history data on humans collected from church book records from 19th century Eastern Finland where joint-families were traditionally common. In joint families several adult offspring, usually sons, stayed in their natal farm with their families. This creates a situation where reproductive-aged women are not related to other women in the family, leading to possible conflict over resources and lowered fitness, but cooperation between women is also possible. We analyse mother’s fecundity and survival of her offspring in relation to the presence and reproductive history of other reproductive-aged women in the family by event history analysis, whist controlling for potential confounders such as presence of other family members and temporal variation in mortality and fertility rates. Preliminary analysis suggest that living in larger joint families was beneficial for women’s fitness, both in terms of fecundity and offspring survival, compared to smaller nuclear families. These results suggest that in this population cooperation between family members was more important than conflict, potentially favouring reduced dispersal among adult siblings

François Mallard
Laboratoire Ecologie et Evolution
Ecole Normale Supérieure
France

Disposable springtails: highly plastic ageing patterns are explained by resource allocation trade-offs in Folsomia candida

poster 

Author(s): Mallard, F, Tully, T

Summary:

Although often neglected, the evidences of senescence occurring in the wild are accumulating (1) and there is a growing interest towards a clarification of how the mortality trajectories have been shaped by the ecological conditions (2). The challenge now lies in understanding the diversity of ageing patterns in the light of evolutionary theory (3). We developed an experimental system in the laboratory to assess these questions on the small and long-living Collembola Folsomia candida (4,5). We performed long term microcosms experiments to question how mortality trajectories have been shaped on the short- and long-term by trade-offs between traits. We found that within species genetic differences in ageing patterns can be explained with differences in growth and reproductive strategies: comparison of different lineages showed that initial mortality rate and age at onset of senescence are negatively correlated - a result coherent with recent predictions based on the 'disposable soma' theory of ageing (6). We also demonstrate that plastic adjustments of major life history traits triggered by changes in resource availability even late in life lead cohorts to shift from constant mortality trajectories (negligible senescence) to accelerated senescence. Our results emphasises the need for a more integrated ecological comprehension of the effects of environment and its fluctuations to understand how natural selection shapes ageing patterns. 1. D. H. Nussey et al., Ageing Research Reviews 12, 214-25 (2013). 2. A. Baudisch, J. W. Vaupel, Science 338, 618-9 (2012). 3. M. Bronikowski et al., Science 331, 1325-8 (2011). 4. T. Tully, R. Ferrière, PLoS One 3, e3207 (2008). 5. T. Tully, A. Lambert, Evolution 65, 3013-20 (2011). 6. M. J. Wensink et al. Biogerontology 13, 197-201 (2012).

Hannah Mumby
University of Sheffield
Department of Animal and Plant Sciences
United Kingdom

Effects of climate on survival of Asian elephants

poster 

Author(s): Mumby, HS, Courtiol, A, Mar, KU, Lummaa, V

Summary:

Climate change has intensified interest in understanding how climatic variability affects animal life histories. Despite this, little is known of their effect on survival in those species. Asian elephants (Elephas maximus) are endangered across their natural distribution, and inhabit regions often characterised by high seasonality of both temperature and rainfall. We investigated the effects of monthly climatic variation on survival and causes of death in Asian elephants of all ages and both sexes, using a unique demographic dataset of 839 semi-captive longitudinally monitored elephants from four sites in Myanmar between 1965 and 2000. Temperature had a pronounced effect on survival, with the lowest predicted survival during the hottest and coldest months in both sexes across all ages. Because during a year the elephants spent twice as long in temperatures higher than their optimum (24C) rather than temperatures below it, most deaths occurred during the “too hot” rather than the “too cold” period. Decreased survival at higher temperatures resulted partially from increased deaths from heat stroke and infectious disease, whilst the lower survival in the coldest months is associated with an increase in non-infectious diseases or poor health in general. Variation in survival was also related to rainfall with the highest survival rates during the wettest months. Our results show that even the normal-range monsoon variation in climate can exert large impact on elephant survival in Myanmar leading to large absolute differences in mortality, particularly among the youngest age classes. The persistence of a long-term trend towards higher global temperatures combined with the possibility of higher variation in temperature between seasons may pose a growing challenge to the survival of species such as the endangered Asian elephants.

Domenico D'Alelio
Stazione Zoologica Anton Dohrn
Ecology and Evolution of Plankton
Italy

Evolutionary demography of microbes: growth, sex and death in a marine planktonic diatom

poster 

Author(s): D'Alelio, D, Scalco, E, Ribera d'Alcalà, M, Montresor, M

Summary:

Populations of unicellular microalgae are orders of magnitude larger than those of multicellular organisms. They reproduce clonally by binary fission producing massive and, at times, periodical blooms. They cope with dramatic loss factors, such as primary consumers, parasite or viral infections. A sexual phase has been also reported for many species. Sex has a high cost in short-term, since cells have to stop division and invest energy in meiosis. Nonetheless, sex has been conserved in many microalgae, since it allows clonal populations to escape extinction, thus reducing its evolutionary cost in the long-term. Among unicellular microalgae, diatoms are key-players in marine ecosystems. Their landmark is represented by the rigid box-shaped siliceous cell-wall that imposes a progressive decrease in the average cell size of the cell population undergoing mitotic divisions. Larger cell size is generally restituted by sexual reproduction that, in diatoms, combines genetic recombination with the production of ‘young’ large cells. We have chosen the diatom Pseudo-nitzschia multistriata as a model to explore the application of a demographic approach to a planktonic microalga at the LTER station in the Gulf of Naples. The approach included in-situ monitoring of cell abundance and cell size, in-vitro experimentation on the factors that induce the transition between clonal reproduction and the onset of the sexual phase, and modeling simulations. We could follow the birth, maturation, and disappearance of various ‘age classes’ in the natural environment where large-sized cells - indicative of sexual reproduction events - were detected every two years. Our data suggest a collective behavior, apparently fostered by quorum sensing mechanisms, that shapes the periodic alternation between asexual and short-term sexual phases. Finally, our study corroborates the possibility to apply an evolutionary demographic approach to the study of unicellular organisms.

Katharina Wyschetzki
Faculty of Biology of University of Regensburg
Institute of Zoology
Germany

Exploring variation in longevity: transcriptomic studies in long-lived ant queens

poster 

Author(s): Wyschetzki, K

Summary:

Senescence occurs in all multicellular and unicellular organisms. It is generally assumed that lifespan is genetically determined. Several candidate genes are suspected to be responsible for a gradual deterioration of physical function. These findings mainly arise from experiments with rather short-lived organisms (flies, worms, mice). However, the enormous intraspecific variation in longevity is often disregarded. Social insects with their different castes (queens, workers, males) have plastic life history traits which also include different aging rates. Ant queens are famous due to their exceptional long life spans compared to workers and males, making them a good model for the study of aging. The myrmecine tramp ant Cardiocondyla obscurior lacks the "reproductive senescence" which is normally present in other organisms (Heinze & Schrempf 2012). In addition, female-male co-evolution determines the lifespan of the queen (Schrempf et al. 2005, Schrempf & Heinze 2008, Schrempf et al. 2011). However, even queens mated with a sterilized male live considerably longer and start to lay eggs earlier than virgin females. In order to gain insights into lifespan-mediating mechanisms of mating, we conducted RNAseq of gene expression of old queens that were subjected to different mating. By comparing old queens mated to a fertile or a sterile male with virgin queens, we aim to find genes involved in the regulation of queen longevity.

Stefano Giaimo
Max Planck Institute for Demographic Research
Germany

Group formation and individual mortality

poster 

Author(s): Giaimo, S, Baudisch, A

Summary:

In some species, organisms perform key activities in groups. This is the case, for example, when nesting or foraging is communal. The evolutionary advantage of this sort of social behaviour is that group members gain access to vital resources in an amount greater than that accessible through individual effort. In this paper, we explore the relationship between group formation and individual mortality in social species. We make two realistic assumptions: (i) there is a time lag between group formation and the moment in which group members enjoy the result of group activities (i.e. laborious construction of the communal nest, human agriculture); (ii) one or more group members may die during this time interval, and remaining members benefit from this event (i.e. the result of group activities is divided among fewer individuals). Two different situations are considered. First, mortality is independent of age, initially. We examine whether changes in individual mortality may have an impact on fitness when grouping is random. Second, mortality increases with age; i.e. ageing. In this situation, the strategy of choosing older individuals as group mates is selectively superior to random grouping. However, selection on “go-for-the-old” appears to be frequency dependent. Finally, we discuss the potential advantages of “segregate-by-age”, a behaviour that has been observed in some species.

Roser Pratdesaba
Faculty of Biology of the University of Barcelona
Department of Genetics
Spain

Inference of the demographic history of Drosophila subobscura using Approximate Bayesian Computation: a multilocus analysis along chromosome J

poster 

Author(s): Pratdesaba, R, Segarra, C, Aguadé, M

Summary:

Understanding the forces that control genetic variation in natural populations has been a major challenge for evolutionary biologists. Drosophila subobscura is a member of the obscura group that is widely distributed in the Paleartic region and presents a rich chromosomal polymorphism. Although this species has been extensively studied in relation to chromosomal inversion polymorphism, little is known about its demographic history. Multilocus studies provide an excellent opportunity to determine whether demographic factors have shaped the genetic variation observable in natural populations. In order to infer the demographic history of D. subobscura from the Paleartic area through Approximate Bayesian Computation (ABC), we sequenced and analyzed 16 non-coding regions distributed along the J chromosome in regions not affected by chromosomal inversions. In the 16 regions, the frequency spectrum was shifted towards an excess of low frequency variants, which led us to explore different simple scenarios including a final population expansion. Even if scarce, existing information on climatic changes as well as on recombination rates in the species under study was used to establish prior distributions for those parameters defining each model. Contrasting the different models through ABC analysis will provide new insides into the evolutionary history of D. subobscura based on an ample dataset of independently evolving loci not affected by chromosomal polymorphism.

Contacts

Chairman: Octávio S. Paulo
Tel: 00 351 217500614 direct
Tel: 00 351 217500000 ext22359
Fax: 00 351 217500028
email: mail@eseb2013.com

Address

XIV Congress of the European Society for Evolutionary Biology

Organization Team
Department of Animal Biology (DBA)
Faculty of Sciences of the University of Lisbon
P-1749-016 Lisbon
Portugal

Website

Computational Biology & Population Genomics Group 
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