Ilkka Hanski Research Articles

Editorial: Biographical Memoirs , Volume 68

Editorial: <i>Biographical Memoirs</i> , Volume 68

Ilkka Aulis Hanski. 14 February 1953—10 May 2016

Professor Ilkka Hanski made seminal contributions to both empirical and theoretical ecology and evolutionary biology, in particular metapopulation biology, throughout his scientific career. He started his career with dung beetle ecology, earning his doctorate at University of Oxford in 1979. He developed the rest of his career at University of Helsinki, where he was appointed professor in ecology in 1993 and academy professor in 2006. Hanski's most influential research was based on empirical work on the Glanville fritillary metapopulation in the Åland Islands, started in 1991, and continued until his death. His early research focused on ecological aspects of metapopulation biology, such as how the spatial structure of a landscape influences extinction thresholds, whereas his later work focused on genetic and evolutionary processes, such as maintenance of genetic variation by selection pressures varying with landscape structure. During the last years of his career, Hanski was a pioneer in the field of eco-evolutionary dynamics, showing how molecular-level underpinnings of trait variation can explain rapid evolutionary changes in natural populations. Hanski actively applied his research findings to conservation biology, involving himself in debates ranging from forest conservation in Finland to the links between human health and biodiversity. He was an exceptionally devoted group leader and mentor of younger researchers. His Metapopulation Research Centre grew gradually from a group consisting of Hanski and a few PhD students into a centre of 70 researchers.

Frontiers in Metapopulation Biology: The Legacy of Ilkka Hanski

This review of metapopulation biology has a special focus on Professor Ilkka Hanski's (1953–2016) research. Hanski made seminal contributions to both empirical and theoretical metapopulation biology throughout his scientific career. Hanski's early research focused on ecological aspects of metapopulation biology, in particular how the spatial structure of a landscape influences extinction thresholds and how habitat loss and fragmentation can result in extinction debt. Hanski then used the Glanville fritillary system as a natural laboratory within which he studied genetic and evolutionary processes, such as the influence of inbreeding on extinction risk and variation in selection for dispersal traits generated by landscape variation. During the last years of his career, Hanski's work was in the forefront of the rapidly developing field of eco-evolutionary dynamics. Hanski was a pioneer in showing how molecular-level underpinnings of trait variation can explain why evolutionary change can occur rapidly in natural populations and how these changes can subsequently influence ecological dynamics.

Ecology: From genes to metapopulations.

A tribute to Ilkka Hanski. Empirical data modelling shows that molecular variation at a candidate gene within populations has consequences for metapopulation size and persistence.

Ilkka Hanski, The “Compleat Ecologist”: An Homage to His Contributions to the Spatial Dimension of Food Web Interactions

Ilkka Hanski is most widely known for his seminal contributions to metapopulation ecology, both theoretical and empirical. But he also made many important and wide-ranging contributions to other arenas of ecological inquiry, including in particular predator—prey, host—parasitoid, and host—pathogen interactions. This paper provides an overview of his work in trophic ecology, ranging from individual behavior of foraging predators and fleeing prey, up to effects of spatial patchiness on the persistence of specialist natural enemies, and even the determinants of food chain length. In recent years, his work on food web interactions took on an increasingly genetic and evolutionary slant. In this paper, I also return to two theoretical models that I discussed over the years with Ilkka, where we contemplated carrying out collaborative work, but never managed to do so. The first of these models involves how habitat patchiness might moderate apparent competition between prey species. The second of these has to do w...

Ilkka Hanski and Small Mammals: from Shrew Metapopulations to Vole and Lemming Cycles

Ilkka Hanski may be best known for his work on insect and metapopulation dynamics, but he also contributed significantly to small mammal research. In the early 1980s he became interested in shrew dynamics, energetics, and of course, shrew metapopulations. He aimed at understanding the population biological consequences of body size in different shrew species. Feeding habits and environmental stochasticity affect shrew species in profoundly different ways: due to their short survival time small species have high extinction rates but their dispersal and colonization capacity is high which enables them to survive as metapopulations. After Hansson and Henttonen reported the Fennoscandian gradients in vole dynamics in the mid-1980s, Hanski became interested in vole and lemming cycles. The first models on this were published with Henttonen and Hansson in 1991 where the roles of specialist and generalist predators were assessed. Later, the models were further developed with Korpimaki and Turchin, with model para...

Holistic View on Health: Two Protective Layers of Biodiversity

The western world has witnessed a rising epidemic of chronic inflammatory disorders, such as allergies and asthma. This epidemic is expected to spread also to the rest of the world, where allergies have to date been practically absent, along with adoption of western lifestyle. In parallel, biological diversity is globally declining. This inspired Ilkka Hanski, together with medical doctors, to formulate the biodiversity hypothesis of allergic disease. This hypothesis proposes that reduced contact with natural environments, including natural microbial diversity, is associated with unhealthy human microbiota, less able to educate the immune system. Contact with beneficial bacteria, particularly early in life, seems to be instrumental to the normal development of immune responses. Changes in lifestyle and diet, destruction of natural environments, and urbanisation threaten our natural exposure to these beneficial bacteria and thus also reduce their impact on our physiology. To ensure a healthy life, we need to preserve biodiversity in the environment and make sure it finds a favourable home in us. In this review, we will focus on the role of commensal microbiota in human health and wellbeing, as well as the interaction between our microbiota and environmental microbiota, highlighting the contribution of Ilkka Hanski.

Butterfly Genomics: Insights from the Genome ofMelitaea cinxia

The first lepidopteran genome (Bombyx mori) was published in 2004. Ten years later the genome of Melitaea cinxia came out as the third butterfly genome published, and the first eukaryotic genome sequenced in Finland. Owing to Ilkka Hanski, the M. cinxia system in the Aland Islands has become a famous model for metapopulation biology. More than 20 years of research on this system provides a strong ecological basis upon which a genetic framework could be built. Genetic knowledge is an essential addition for understanding eco-evolutionary dynamics and the genetic basis of variability in life history traits. Here we review the process of the M. cinxia genome project, its implications for lepidopteran genome evolution, and describe how the genome has been used for gene expression studies to identify genetic consequences of habitat fragmentation. Finally, we introduce some future possibilities and challenges for genomic research in M. cinxia and other Lepidoptera.

What Should Conservation Biologists be Doing? An Homage to Ilkka Hanski

What Should Conservation Biologists be Doing? An Homage to Ilkka Hanski

Ecology: Winged insights

H. Charles J. Godfray is inspired by the scientific memoir of late island ecologist Ilkka Hanski.

Discovery of genetic polymorphism: Richard Lewontin and Tomoko Ohta awarded the Crafoord Prize in Biosciences 2015.

Richard Lewontin and Tomoko Ohta are awarded the 2015 Crafoord Prize for their pioneering analyses and fundamental contributions to the understanding of genetic polymorphism. Earlier Crafoord laureates in biosciences include Ilkka Hanski (2011), Robert L. Trivers (2007), Carl R. Woese (2003), John Maynard Smith, Ernst Mayr and George C. Williams (1999), Robert May (1996), Seymour Benzer and William T. Hamilton (1993), Paul R. Ehrlich and Edward O. Wilson (1990), Eugene P. Odum and Howard T. Odum (1987), and Daniel H. Janzen (1984). The scientific discoveries of Richard Lewontin and Tomoko Ohta are of great general significance in basic research but applied knowledge of genetic variation is highly relevant also in environmental and conservation sciences. In ecology and conservation, it has led to a better understanding of population structure and genetic vulnerability among threatened populations. Another result has been new methods for estimating the size of natural populations using the DNA analysis of animal spoor, such as scat. In systematic biology, knowledge of genetic variation has resulted in new opportunities for understanding relationships between and within species. Furthermore, it is now possible to determine close relationships between individuals using DNA analysis. In many species, the females mate with more than one male, so that the offspring in one litter are often half-siblings. Nowadays, it may seem obvious that our genetic makeup is as unique as our fingerprints, but this was a contradiction to the prevailing theories when it was discovered in the 1960s. The view of genetic variation up until then was entirely different: biologists believed that most individuals in a population were fairly similar, genetically speaking. This must, they assumed, be the result of natural selection, where every genetic variant that was less beneficial was eliminated. Richard Lewontin used a method that separated proteins based on their molecular characteristics, obtaining very surprising results. The genetic variation between individuals in a population was many times greater than expected. The pattern was repeated in every species examined. They all demonstrated a significant and unexpected genetic variation, appearing to contradict the principles of natural selection. A theory of neutral mutations was put forward, in which gene variants that neither improve nor worsen an individual’s fitness are created. Geneticist Tomoko Ohta developed theory suggesting that almost all mutations in genes that affect the encoded proteins are somewhat harmful, but the effect of this is so small that these gene variants can remain in the population. They can thus be considered nearly neutral. Ohta also showed that the size of a population is decisive for the effectiveness of natural selection: the smaller the population, the greater the effect of chance, and natural selection will function more poorly. Both Lewontin and Ohta have continued to study genetic variation and have, over a number of decades, made sizable contributions to the continuing development of knowledge in the field. Today, Lewontin and Ohta are Professors Emeriti at Harvard University, MA, USA and the National Institute of Genetics, Mishima, Japan, respectively. During the autumn 2015, AMBIO will publish a Perspective with a more detailed account of the important work of these two pioneers and its relevance for environmental sciences.

Biodiversity, microbes and human well-being

ESEP Ethics in Science and Environmental Politics Contact the journal RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections ESEP 14:19-25 (2014) - DOI: https://doi.org/10.3354/esep00150 AS I SEE IT Biodiversity, microbes and human well-being Ilkka Hanski Department of Biosciences, University of Helsinki, Helsinki 00014, Finland *Corresponding author: ilkka.hanski@helsinki.fi ABSTRACT: The biodiversity hypothesis postulates that the rapid increase in the prevalence of allergies, asthma and other chronic inflammatory disorders in developed countries in the past few decades is caused by loss of biodiversity, which reduces human exposure to beneficial environmental microbes with essential immunoregulatory functions. The biodiversity hypothesis builds upon Graham Rook’s ‘old friends’ concept, which highlights the long-term evolution of the human immune system with a diverse assembly of microbes. I describe a case study showing that the incidence of atopy (allergy sensitization) in adolescents decreases significantly with an increasing amount of forest and agricultural land in the surroundings of their homes. Environmental microbiota as part of broader biodiversity provides a tangible but little appreciated ‘ecosystem service’, which is vital for every individual. KEY WORDS: Biodiversity · Environmental microbiota · Immune tolerance · Proteobacteria · Acinetobacter Full text in pdf format PreviousNextCite this article as: Hanski I (2014) Biodiversity, microbes and human well-being. Ethics Sci Environ Polit 14:19-25. https://doi.org/10.3354/esep00150 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESEP Vol. 14, No. 1. Online publication date: October 27, 2014 Print ISSN: 1863-5415; Online ISSN: 1611-8014 Copyright © 2014 Inter-Research.

Profile of Ilkka A. Hanski

Watching birds and collecting butterflies in the field behind his boyhood home, young Ilkka Hanski marveled at the isolated habitats in which many insects live. Decades later, the Director of the Metapopulation Research Group at the University of Helsinki in Finland admits that many of his most successful research projects on the study of metapopulations, or isolated yet interconnected populations of the same species, were inspired by childhood adventures in his own back yard. Hanski, elected to the National Academy of Sciences (NAS) in 2010, has helped predict how plant and animal populations respond when their habitats are broken into fragments, whether by urbanization, deforestation, climate change, or entirely natural processes. His studies have earned him the 2011 Crafoord Prize in Biosciences from the Royal Swedish Academy of Sciences, as well as election to the Royal Society, the Finnish Academy of Science and Letters, and most recently, the NAS. Ilkka A. Hanski in the field. Before the 1970s, ecologists paid little attention to the spatial structure of populations, whether they were continuously distributed in space, assemblages of local populations, or a mix of both. In 1969, American population biologist Richard Levins first introduced the concept of a metapopulation. However, it was Hanski—who has since led the field of metapopulation biology through the development of basic concepts, models, and informative empirical examples—who helped gauge the prospects of long-term survival for species living in fragmented landscapes. Hanski's mathematical models have revealed how a collection of many small local populations survive in a network of habitat fragments. For the past 2 decades, Hanski has used the Glanville fritillary butterfly as a study system to fuel his models and to probe the ecological, genetic, and evolutionary consequences of habitat fragmentation. To date, Hanski's models have been used to predict the dynamics of animal and …

A Spatial Dimension of Ecology: Ilkka Hanski Crafoord Laureate in 2011

The Finnish ecologist Ilkka Hanski is awarded the Crafoord Prize in Biosciences for 2011 for his pioneering studies of how spatial variation affects the dynamics of animal and plant populations. Earlier Crafoord laureates in Biosciences include Robert L. Trivers (2007), Carl R. Woese (2003), John Maynard Smith, Ernst Mayr and George C. Williams (1999), Robert May (1996), Seymour Benzer and William T. Hamilton (1993), Paul R. Ehrlich and Edward O. Wilson (1990), Eugene P. Odum and Howard T. Odum (1987) and Daniel H. Janzen (1984). A common textbook defines ecology as the study of the mechanisms behind species abundance and distribution where each species can be characterized by the size and location of its populations. Ecological populations are rarely constant over time and space but vary due to factors both intrinsic to the system and extrinsic environmental variation. Even in a spatially homogeneous environment, populations of predator and prey may show patchy distributions due to, for example, differences in movement rates. In most cases, variation in population sizes over space (and time) is, however, a result of spatial variation in the distribution of suitable habitats, and it is in this context that Ilkka Hanski has made his major contributions. Inspired by a short paper by Richard Levins published in the late 1960s, Hanski initiated a development of both theory and empirical research that has now grown to become a major research area in ecology. Baptized as Metapopulation Ecology (Hanski 1999), this research now engages ecologists all over the world in studies in many different kinds of environments. Although animals and plants are most common, the metapopulation theories are used for all major groups of organisms. As in most scientific breakthroughs, the basic idea is quite simple. Each population is seen as an “individual”, which is born (the population is founded by colonization of a site) and ultimately dies (the population goes extinct). The likelihood of colonization is dependent on the presence of other populations in the surroundings (the isolation of the site) and the risk of extinction is dependent in the population size (the area of the site). From this simple basis of habitat area and isolation, Hanski has developed more complex theory to deal with the realism that makes ecological studies such a challenge. These extensions consider aspects such as population dynamics in local populations and stochastic variation. Along with the theoretical development, Hanski has also performed outstanding field studies, the most important being done on a butterfly (Melitaea cinxia) and its host plants in the Aland archipelago. For conservation biologists, Hanski’s studies have provided a tool box for analyzing how species are affected by habitat change and fragmentation. As habitat loss is considered as the major factor behind biodiversity decline and species extinction, the metapopulation theory has become a cornerstone of conservation biology. One major insight for conservation biology is the concept of “extinction debt” relating to the time delay between habitat loss and the extinction of a species which is particularly long when it is close to its extinction threshold. Metapopulation theory has also led to further developments of ecological theory concerned with spatial aspects of whole communities and ecosystems—metacommunityecology and meta-ecosystemecology—no doubt providing us with important new insights on the spatial dimension of the dynamics of ecological systems. In particular, metacommunity theory has developed into a rich theory studying the effects of trade-offs related to colonization and competitive ability, species-specific responses to environmental heterogeneity, stochastic demographic processes and dispersal limitation on species diversity in heterogeneous landscapes.

Genes Affect Population Growth, but the Environment Determines How

Why does a population in the wild grow or shrink, or remain the same over generations? Genes would seem an obvious factor, but in fact there is remarkably little evidence that genetic effects influence year-to-year population dynamics, beyond the well-recognized negative effect from inbreeding on very small populations. This lack of evidence for a genetic effect partly reflects the difficulty of choosing which gene to study, as only a few genes may be under strong selection at any given time, and fewer still will affect population dynamics. It also partly reflects an important truth about natural selection—it may determine who survives to reproduce, but not necessarily the total number of survivors. In many cases, ecological factors such as resource abundance and natural enemies may overwhelm any slight genetic effect on population dynamics. Finding a genetic effect, then, would require both knowing which pin in the genetic haystack to look for and having detailed knowledge of the complex and powerful environmental factors against which this effect plays out. In a new study, Ilkka Hanski and Ilik Saccheri show that variants of a sugar-metabolizing gene do indeed influence population growth in a species of butterfly, but in a complex and habitat-dependent way. The authors studied the Glanville fritillary butterfly on the Aland Islands in Finland, where its population dynamics are well studied, and its habitat—patches of dry meadows spread across the landscape—is well mapped. They focused on the gene phosphoglucose isomerase (Pgi), a key enzyme in the breakdown of sugar. The Pgi gene occurs in several forms, or alleles, whose proteins differ in their kinetic properties and thermal stability. These alleles have been previously linked to differences in flight metabolic rate and fecundity in this butterfly, making the gene a good candidate for observing a population effect, if there is one. The f and d alleles of Pgi are the most common, and previous work has shown that butterflies with either an ff or an fd genotype have a higher flight metabolic rate and are more fecund than those with a dd genotype. By analyzing genotypes, population growth, and habitat area simultaneously among more than 130 small butterfly populations, the authors showed that, in small meadows, growth was highest when the ff or fd genotypes predominated, but in larger meadows, the opposite was true—these genotypes predicted a decline in numbers instead of a rise, while dd was favored. The effect appeared to be specific to Pgi, as there was no correlation with genotype for any of the six other genes. The likely explanation for this effect, according to the authors, is related to the differences in maturation and egg laying between females bearing f and d alleles. Those with f alleles mature quickly and lay more eggs early on, just the strategy for exploiting a small patch, from which many butterflies risk drifting away rather quickly in their life. Those with d alleles mature later but also die later, allowing them to exploit a larger habitat more thoroughly. However, the authors note that this may not be the only, or even the main, reason for the genotype-habitat area effect, since Pgi is likely to influence many different aspects of life history. The results of this study confirm that, under the right circumstances, intraspecific genetic variation can influence population growth. But they also make an important point about fitness. A major goal of evolutionary physiology is to understand the selective advantage of the traits found in a population, and it is often tempting in this pursuit to assume there is a single “best” genotype. This study provides a strong counterargument against such one-size-fits-all models of evolution, pointing out that in the ecological theater, which script plays best is a function of exactly which stage you are on.

A Checkered History

On the Wings of Checkerspots A Model System for Population Biology. Paul R. Ehrlich and Ilkka Hanski, Eds. Oxford University Press, New York, 2004. 391 pp. $64.50, £40. ISBN 0-19-515827-X. The contributors synthesize results from the editors' long-term research projects in the Bay Area and Finland, which have made important contributions to our understanding of the ecological and evolutionary dynamics of populations and to conservation biology.

AN AUSTRALIAN PERSPECTIVE ON POPULATION VIABILITY IN FRAGMENTED LANDSCAPES

Journal Article AN AUSTRALIAN PERSPECTIVE ON POPULATION VIABILITY IN FRAGMENTED LANDSCAPES Get access Ilkka Hanski Ilkka Hanski Metapopulation Research Group, Department of Ecology and Systematics, P.O. Box 17, FIN‐00014, University of Helsinki, Finland E‐mail: ilkka.hanski@helsinki.fi Search for other works by this author on: Oxford Academic Google Scholar Evolution, Volume 55, Issue 12, 1 December 2001, Pages 2623–2626, https://doi.org/10.1111/j.0014-3820.2001.tb00776.x Published: 01 December 2001 Article history Received: 31 October 2001 Published: 01 December 2001

On the use of connectivity measures in spatial ecology

OikosVolume 95, Issue 1 p. 147-151 On the use of connectivity measures in spatial ecology Atte Moilanen, Atte Moilanen Dept of Ecology and Systematics, Div. of Population Biology, PO Box 17, FIN-00014 University of Helsinki, Finland (atte.moilanen@helsinki.fi).Search for more papers by this authorIlkka Hanski, Ilkka Hanski Dept of Ecology and Systematics, Div. of Population Biology, PO Box 17, FIN-00014 University of Helsinki, Finland (atte.moilanen@helsinki.fi).Search for more papers by this author Atte Moilanen, Atte Moilanen Dept of Ecology and Systematics, Div. of Population Biology, PO Box 17, FIN-00014 University of Helsinki, Finland (atte.moilanen@helsinki.fi).Search for more papers by this authorIlkka Hanski, Ilkka Hanski Dept of Ecology and Systematics, Div. of Population Biology, PO Box 17, FIN-00014 University of Helsinki, Finland (atte.moilanen@helsinki.fi).Search for more papers by this author First published: 10 April 2003 https://doi.org/10.1034/j.1600-0706.2001.950116.xCitations: 209AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume95, Issue1October 2001Pages 147-151 RelatedInformation

RAMAS/Metapop: Viability Analysis for Stage-Structured Metapopulations.H. Resit Akcakaya

Previous articleNext article No AccessNew Biological SoftwareRAMAS/Metapop: Viability Analysis for Stage-Structured Metapopulations. H. Resit Akcakaya Greg J. Witteman and Michael GilpinGreg J. Witteman Search for more articles by this author and Michael Gilpin Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Quarterly Review of Biology Volume 70, Number 3Sep., 1995 Published in association with Stony Brook University Article DOIhttps://doi.org/10.1086/419165 Views: 10Total views on this site Citations: 2Citations are reported from Crossref Copyright 1995 The University of ChicagoPDF download Crossref reports the following articles citing this article:Philip J. Harrison, Ilkka Hanski, Otso Ovaskainen Bayesian state-space modeling of metapopulation dynamics in the Glanville fritillary butterfly, Ecological Monographs 81, no.44 (Nov 2011): 581–598.https://doi.org/10.1890/11-0192.1 References, (Dec 2009).https://doi.org/10.1201/9781420032321.bmatt

An Optimal Life-History Strategy in which Reproductive Effort Decreases with Age

Previous articleNext article No AccessLetters to the EditorsAn Optimal Life-History Strategy in which Reproductive Effort Decreases with AgeRobert M. FagenRobert M. Fagen Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 106, Number 948Mar. - Apr., 1972 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/282766 Views: 4Total views on this site Citations: 17Citations are reported from Crossref Copyright 1972 The University of Chicago.PDF download Crossref reports the following articles citing this article:Reuven Dukas Animal expertise: mechanisms, ecology and evolution, Animal Behaviour 147 (Jan 2019): 199–210.https://doi.org/10.1016/j.anbehav.2018.05.010Reuven Dukas Life history of learning: performance curves of honeybees in settings that minimize the role of learning, Animal Behaviour 75, no.33 (Mar 2008): 1125–1130.https://doi.org/10.1016/j.anbehav.2007.08.029SÉBASTIEN DESCAMPS, STAN BOUTIN, DOMINIQUE BERTEAUX, JEAN-MICHEL GAILLARD Female red squirrels fit Williams’ hypothesis of increasing reproductive effort with increasing age, Journal of Animal Ecology 76, no.66 (Nov 2007): 1192–1201.https://doi.org/10.1111/j.1365-2656.2007.01301.x Lock Rogers and Robert Craig Sargent A Dynamic Model of Size‐Dependent Reproductive Effort in a Sequential Hermaphrodite: A Counterexample to Williams's Conjecture. L. Rogers and R. C. Sargent, The American Naturalist 158, no.55 (Jul 2015): 543–552.https://doi.org/10.1086/323119JOSEPH APALOO FREQUENCY INDEPENDENT EVOLUTIONARY MODELS, Journal of Biological Systems 07, no.0101 (Mar 1999): 1–9.https://doi.org/10.1142/S0218339099000024P. A. Langley, T. H. Clutton-Brock Does reproductive investment change with age in tsetse flies, Glossina morsitans morsitans (Diptera: Glossinidae)?, Functional Ecology 12, no.66 (Mar 2002): 866–870.https://doi.org/10.1046/j.1365-2435.1998.00262.xJohn P. Phelan, Peter C. Frumhoff Differences in the effects of parental age on offspring life history between tropical and temperate populations of milkweed bugs (Oncopeltus spp.), Evolutionary Ecology 5, no.22 (Apr 1991): 160–172.https://doi.org/10.1007/BF02270832James T. Giesel Life-history strategies, (Jan 1988): 153–161.https://doi.org/10.1007/978-1-4899-2683-8_12Ismo J. Holopainen, Ilkka Hanski Life history variation in Pisidium (Bivalvia: Pisidiidae), Ecography 9, no.22 (May 1986): 85–98.https://doi.org/10.1111/j.1600-0587.1986.tb01195.xTakashi Kohyama Studies on theAbies population of Mt. Shimagare II. Reproductive and life history traits, The Botanical Magazine Tokyo 95, no.22 (Jun 1982): 167–181.https://doi.org/10.1007/BF02488583Richard Shine ?Costs? of reproduction in reptiles, Oecologia 46, no.11 (Jul 1980): 92–100.https://doi.org/10.1007/BF00346972 Nancy Burley Clutch Overlap and Clutch Size: Alternative and Complementary Reproductive Tactics, The American Naturalist 115, no.22 (Oct 2015): 223–246.https://doi.org/10.1086/283556Nils Chr. Stenseth Demographic strategies in fluctuating populations of small rodents, Oecologia 33, no.22 (Jan 1978): 149–172.https://doi.org/10.1007/BF00344845John Michael Dearn Variable life history characteristics along an altitudinal gradient in three species of Australian grasshopper, Oecologia 28, no.11 (Mar 1977): 67–85.https://doi.org/10.1007/BF00346837Jesús Alberto León Life histories as adaptive strategies, Journal of Theoretical Biology 60, no.22 (Aug 1976): 301–335.https://doi.org/10.1016/0022-5193(76)90062-X Brian Charlesworth , and Jesus Alberto Leon The Relation of Reproductive Effort to Age, The American Naturalist 110, no.973973 (Oct 2015): 449–459.https://doi.org/10.1086/283079 Eric R. Pianka , and William S. Parker Age-Specific Reproductive Tactics, The American Naturalist 109, no.968968 (Oct 2015): 453–464.https://doi.org/10.1086/283013