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Sex differences in lifespan have been labelled as one of the most robust features in biology. In human populations, women live consistently longer than men, a pattern that encompasses most mammalian species. However, when expanding both the taxonomic scope beyond mammals and the range of mortality metrics the female survival advantage over males is no longer the rule. Moreover, current evidence suggests that sex differences in actuarial ageing parameters (i.e. age at the onset of ageing and rate of ageing) are far from consistent across the tree of life. This chapter first reviews current knowledge of sex differences in mortality patterns across animals and appraises how these diverse patterns can be explained by the current evolutionary framework. It then emphasizes the relevance of going beyond the differences in mortality patterns by exploring how natural and sexual selection have shaped age- and sex-specific changes in reproductive performance and body mass across the tree of life, and by identifying some possible biological pathways modulating ageing in a sex-specific way. Finally, it highlights how evolutionary theories can be relevant to understand the widespread differences in causes of death between sexes, offering a complementary approach to gain a comprehensive understanding of the evolution of sex differences in health and ageing, with likely biomedical implications.
The West Atlantic trumpetfish Aulostomus maculatus is a species of little commercial importance, but it is frequently used as a study organism in behavioural ecology, and it has been traded in the aquarium industry to some extent. The adult life stage is well described, however its early life history is nearly unknown. This paper provides the first description of post-flexion larvae of A. maculatus, including detailed illustrations, photographs, morphological data, and collection site data of specimens collected during a multipurpose research survey conducted within the Sargasso Sea Subtropical Convergence Zone. The collection site also implies a geographic range expansion, off the continental shelf, of the pelagic larvae stage. This paper hence advances the scientific knowledge about the early life stages, distribution and ecology of this species.
A species’ behavioral, developmental, and reproductive life history will influence how quickly it can recover after a population crash. Some species can recover very quickly, while others, such as the North Atlantic right whale, cannot recover quickly, because even under ideal conditions they develop slowly and have very low reproductive rates. Ecologists have described various life history classification schemes that identify important tradeoffs in resource allocation, and focus attention on interesting life history questions. The quantitative relationship between metabolic rate and body size can help ecologists understand some life history tradeoffs, such as the relationship between number and size of offspring. There is a fundamental tradeoff between parental investment in any one reproductive event and the number of lifetime reproductive events, which in some cases can lead to a semelparous reproductive life history. Variable environments can select for phenotypic plasticity, which can lead to organisms with similar genotypes expressing alternative behavioral, developmental or reproductive life history traits. In some cases, phenotypic plasticity may help species adjust to rapidly changing environmental conditions, including climate change.
Dan Janzen and Winnie Hallwachs, his wife and colleague, have spent two lifetimes studying ecological interactions between organisms, mostly at Area de Conservacion Guanacaste (ACG) in northwestern Costa Rica. Early in his career, Janzen investigated many basic questions in evolutionary community ecology. One study of plant reproductive success and life history strategies showed that legume species use one of two alternative strategies to reproduce successfully – producing huge numbers of tiny defenseless seeds or small numbers of large, well-defended seeds. A second study explained high biological diversity in rainforests as arising because baby plants survive poorly near their parents (because seed predators consume them there), and only become established a considerable distance away from them. He also emphasizes that current selection pressures may differ from historical pressures, so it is critical to understand ecosystems in the context of their evolutionary history. Both Janzen and Hallwachs have now shifted their focus to inventorying the diversity of Lepidoptera, their parasitoids and host plants at ACG, so that their complex interactions can be understood by researchers and by students who use ACQ as a natural classroom.
This article proposes the concept of ‘memory script’ to analyse how, in the aftermath of political violence, memory activists narrate their lives in a way that is practised, repetitive and performative. Through a self-reflective life history of Aluízio Palmar, a Brazilian human rights activist and former political prisoner who suffered intense torture under military rule, this approach seeks to elucidates the personal and political contours of somebody's decision to transform their experiences into a public narrative. A close reading of Palmar's various platforms of memory-sharing reveals the complex moral reckoning of an activist's own trauma.
Stylops ater is an endoparasite of the mining bee Andrena vaga with extreme sexual dimorphism and hypermetamorphosis. Its population structure, parasitization mode, genetic diversity and impact on host morphology were examined in nesting sites in Germany to better understand this highly specialized host–parasite interaction. The shift in host emergence due to stylopization was proven to be especially strong in A. vaga. Around 10% of bees hosted more than 1 Stylops, with at maximum 4. A trend in Stylops' preference for hosts of their own sex and a sex-specific position of extrusion from the host abdomen was found. Invasion of Andrena eggs by Stylops primary larvae was depicted for the first time. Cephalothoraces of female Stylops were smaller in male and pluristylopized hosts, likely due to lower nutrient supply. The genes H3, 18S and cytochrome c oxidase subunit 1 were highly conserved, revealing near-absence of local variation within Stylops. Ovaries of hosts with male Stylops contained poorly developed eggs while those of hosts with female Stylops were devoid of visible eggs, which might be due to a higher protein demand of female Stylops. Male Stylops, which might have a more energy-consuming development, led to a reduction in head width of their hosts. Host masculinization was present in the leaner shape of the metabasitarsus of stylopized females and is interpreted as a by-product of manipulation of the host's endocrine system to shift its emergence. Stylopization intensified tergal hairiness, most strongly in hosts with female Stylops, near the point of parasite extrusion, hinting towards substance-induced host manipulation.
The scientific study of animal welfare has generated a welter of complex, equivocal and often contradictory results. Consequently, there is little agreement about how impairment of welfare should be measured. While some solutions to this have been suggested, these have usually relied on more sophisticated versions of, or more control over, existing measures. However, we argue that the difficulties arise because of questionable assumptions in the definition and measurement of welfare, in particular the measurement of suffering and the assumed importance of individual well-being. We contend that welfare can be interpreted only in terms of what natural selection has designed an organism to do and how circumstances impinge on its functional design. Organisms are designed for self-expenditure and the relative importance of self-preservation and survival, and the concomitant investment of time and resources in different activities, varies with life history strategy. The traditional notions of coping and stress are anthropomorphisms based on homeostatic mechanisms of self-preservation in a long-lived species. Suffering-like states are viewed as generalized subjective states that are geared to avoiding deleterious circumstances with which the organism does not have specific adaptive mechanisms to deal. Attempts to measure suffering-like states directly are likely to remain inconclusive, at least for the foreseeable future, because such states are private and subjective, may take many forms fundamentally different from our own and are likely to depend on the operation of phenotype-limited priorities and decision rules. However, measuring the impact of circumstances on functional design via the organism ‘s decision rules provides a practicable means of giving benefit of the doubt by indicating when suffering, or an analogous subjective state, is likely.
Drought is a substantial threat to cereal production under global climatic change scenarios, albeit its aftermath on arthropod pests is yet contentious. To address this issue, demographic characteristics of Metopolophium dirhodum (Walker, 1849) (Hemiptera: Aphididae) were studied on one drought-susceptible wheat cultivar and one drought-tolerant wheat cultivar under different water treatments. Some physiological and biochemical features of wheat cultivars including leaf soluble sugar and proline contents and antioxidant enzymes activities were also investigated. Significant differences occurred in the developmental period, survival, and fecundity of M. dirhodum between wheat cultivars under various water treatments. The impact of intermediate and severe water stress on M. dirhodum was neutral and negative for the tolerant cultivar and negative for the water-susceptible cultivar, respectively. Under severe water stress, on both wheat cultivars, the aphids had low net reproductive rates and finite and intrinsic rates of increase in comparison with those reared on unstressed plants. In total, drought resulted in lower growth of population and reduced survival of aphids. Hence, in the context of projected climatic changes, acute water deficiency could probably result in reducing the abundance and menace of outburst of M. dirhodum. However, it should be noted that the potential likelihood of M. dirhodum eruptions can be drastically affected by the degree of drought intensity and host plant cultivar.
Bisexual behavior is an order of magnitude more common than exclusive homosexuality in women. Many evolutionary hypotheses on sexual orientation have focused on homosexuality, particularly in men, yet there has recently been a growing recognition that male and female homosexuality may have different evolutionary origins, and that the various forms of nonheterosexuality in the female sexual orientation spectrum may arise via discrete evolutionary–developmental mechanisms. Evolutionarily informed sex research therefore has the fascinating task of understanding the whole spectrum of female sexual orientation – from heterosexual, mostly heterosexual, and bisexual women through to exclusively homosexual women, and from feminine femmes to masculine butches – including the proximate mechanisms and ultimate functions that underlie that variation. Here, we address that task by applying Tinbergen’s four questions to analyze female bisexuality, synthesizing existing research on proximate mechanisms, ontogeny, phylogeny, and ultimate functions. Research in psychology and behavioral sciences indicates that bisexual women comprise a group distinct from heterosexual women and, on some metrics, even from lesbian women: bisexual women have more male-typical personality traits, more unrestricted sociosexual attitudes and behaviors, higher sexual responsiveness, earlier reproduction, higher substance use, higher incarceration rates, and worse health outcomes than heterosexual women. There is broad evidence from across mammalian species that indicates that individual differences in prenatal exposure to sex hormones creates individual differences in brain morphology, cognition, behavioral predispositions, and even life outcomes. They are typically studied in a sex differences framework, but there is now enough evidence to suggest that sexual orientation differences along these parameters can also be robust and informative. We review ten ultimate-level hypotheses on the evolution of female bisexuality and conclude that four hypotheses – balanced polymorphism of masculinity, sexually antagonistic selection, hormonally mediated fast life history strategy, and by-product – are currently best supported by evidence. These hypotheses are also consilient with the wealth of neurodevelopmental evidence on the masculinization of the brain and behavior, which is thought to underlie variation in female sexual orientation. By synthesizing ultimate functions with proximate mechanisms – combined with powerful mid-level frameworks such as life history theory – evolutionary scientists are in a stronger position to provide a comprehensive account of the phenotypic variation observed in the female sexual orientation spectrum.
Improved clarity of Neanderthal ways of life brought about by advancements in analysing the fossil and archaeological records, accompanied by increased willingness to accept complex Neanderthal cognition, makes it appropriate to begin to understand their sexual behavior. In this chapter, we briefly review current understandings about Neanderthals based on anatomy, genetics, and behavior evidenced from the archaeological record. We then integrate this with broad behavioral ecology and evolutionary sexual selection concepts to consider potential selection pressures on Neanderthals’ sexual and reproductive behaviors. Large adult brain size, rapid infant brain growth, and protracted offspring development, similar to Homo sapiens, were supported by adaptations in social organization, mating and parental effort. It is likely that male provisioning and investment in offspring strengthened reproductive pair bonds, improved infant survival, and impacted mate choice in both sexes. Systematic collaborative subsistence strategies were probably matched by a heavy reliance on kin and other trusted adults within the cooperative breeding group, reducing the energy burden on reproducing females, and enabling shorter lactation and reduced interbirth intervals. Neanderthals’ wide ecological tolerances and behavioral flexibility suggest that they also adjusted their sexual and reproductive behavior according to environmental circumstances. Small group size, local-to-regional social networks and potentially seasonal breeding enabled populations to adapt to fluctuating energy availability. During harsher climatic phases, limited access to mating opportunities may have favored social monogamy, with genetic isolation and inbreeding more likely. When conditions were milder (during interglacials, in warmer regions or seasons) with more plentiful resources, group sizes and social networks may have permitted polygyny. Finally we explore the behavioral implications of genetic evidence that Neanderthals interbred with other hominins including H. sapiens. This suggests that differences in physical appearance and social structures did not prevent copulation or raising hybrid infants, although sterility and lower fitness of the latter may have limited the spread of genes between species.
Biological control is one of the methods available for control of Aedes aegypti populations. We used experimental microcosms to evaluate the effects of actual predation and predation risk by dragonfly larvae (Odonata) on larval development, adult longevity, and adult size of Ae. aegypti. We used six treatments: control, removal, variable density cues (Cues VD), fixed density cues (Cues FD), variable density predator (Predator VD), and fixed density predator (Predator FD) (n = 5 each). Predator treatments received one dragonfly larva. Cue treatments were composed of crushed Ae. aegypti larvae released into the microcosm. For the FD treatments, we maintained a larval density of 200 individuals. The average mortality of Ae. aegypti larvae in the Predator VD treatment was used as the standard mortality for the other treatments. Mosquitoes from the Predator VD and Cues VD treatments developed faster, and adults were larger and had greater longevity compared to all other treatments, likely due to the higher food availability from larval density reduction. High larval density negatively affected larval developmental time, adult size, and longevity. Males were less sensitive to density-dependent effects. Results from this study suggest that the presence of predators may lead to the emergence of adult mosquitoes with greater fitness, causing an overall positive effect on Ae. aegypti population growth rates.
In this chapter, we explore the variation within the increasingly-threatened species of the Trachypithecus genus living in the Indo-Burmese region. These species live in habitats varying from shrubby karst to closed-canopy habitat with most in fragmented/disturbed primary or secondary forests that experience wet and dry seasons in a tropical monsoon climate. Trachypithecus species have adaptations for their highly-leafy, yet selective, diets, including high rates of inactivity and feeding that may shift seasonally, with habitat quality or by age-sex class. Home ranges are used differently depending on season, habitat quality and behaviour and there is variable territoriality. Predation pressure appears to be minimal, with the exception of human poachers. Most groups are unimale reproductive groups, although larger multimale and smaller all-male groups also exist. It is unclear whether these species exhibit female philopatry and/or dual dispersal and many soeices lack a strict/overt dominance hierarchy. Maturing around 3-5 years of age, these species have relaxed seasonality to mating/birth patterns and intervals are roughly two years with weaning at 18-21 months. Within this group research has primarily been concentrated on the distribution and habitat, diet and population status of limestone langurs. Conservation efforts should focus on impacts of deforestation and fragmentation.
Dental tissues have the unique property of recording their development history as histological growth markers. Animal studies have shown that many stress events (birth, weaning, infections) can generate a chemical signature. Enamel and dentin offer a retrospective view of significant events occurring in growth but are limited in time to the end of the permanent dentition growth and development. Recent improvements in cementum histological analysis offer new perspectives for analyzing stressors and life history events throughout life. This chapter tests the hypothesis that pregnancy may disrupt acellular cementum (AC) deposits visible in the mineralized matrix, using light microscopy, Raman spectrometry, and scanning electron microscopy equipped with an EDS probe. Two human samples with known age at pregnancies demonstrated that accentuated AC increments can be identified and precisely matched to these events. In both samples, these AC variations were the most outstanding optically and chemically. This is notable since such a method’s ultimate purpose is to identify fertility events in archaeological samples blindly.
Recent neurodevelopmental and evolutionary theories offer strong theoretical rationales and some empirical evidence to support the importance of specific dimensions of early adversity. However, studies have often been limited by omission of other adversity dimensions, singular outcomes, and short follow up durations. 1,420 participants in the community, Great Smoky Mountains Study, were assessed up to eight times between age 9 and 16 for four dimensions of early adversity: Threat, Material Deprivation, Unpredictability, and Loss (as well as a Cumulative Adversity measure). Participants were followed up to four times in adulthood (ages 19, 21, 25, and 30) to measure psychiatric disorders, substance disorder, and “real-world” functioning. Every childhood adversity dimension was associated with multiple adult psychiatric, substance, or functional outcomes when tested simultaneously in a multivariable analysis that accounted for other childhood adversities. There was evidence of differential impact of dimensions of adversity exposure on proximal outcomes (e.g., material deprivation and IQ) and even on distal outcomes (e.g., threat and emotional functioning). There were similar levels of prediction between the best set of individual adversity scales and a single cumulative adversity measure when considering distal outcomes. All dimensions of childhood adversity have lasting, pleiotropic effects, on adult health and functioning, but these dimensions may act via distinct proximal pathways.
We expand upon prior work (Gibbons et al., 2012) relating childhood stressor effects, particularly harsh childhood environments, to risky behavior and ultimately physical health by adding longer-term outcomes – deoxyribonucleic acid (DNA) methylation-based measures of accelerated aging (DNAm-aging). Further, following work on the effects of early exposure to danger (McLaughlin et al., 2014), we also identify an additional pathway from harsh childhood environments to DNAm-aging that we label the danger/FKBP5 pathway, which includes early exposure to dangerous community conditions that are thought to impact glucocorticoid regulation and pro-inflammatory mechanisms. Because different DNAm-aging indices provide different windows on accelerated aging, we contrast effects on early indices of DNAm-aging based on chronological age with later indices that focused on predicting biological outcomes. We utilize data from Family and Community Health Study participants (N = 449) from age 10 to 29. We find that harshness influences parenting, which, in turn, influences accelerated DNAm-aging through the risky cognitions and substance use (i.e., behavioral) pathway outlined by Gibbons et al. (2012). Harshness is also associated with increased exposure to threat/danger, which, in turn, leads to accelerated DNAm-aging through effects on FKBP5 activity and enhanced pro-inflammatory tendencies (i.e., the danger/FKBP5 pathway).
Host–parasite coevolution may result in life-history changes in hosts that can limit the detrimental effects of parasitism. Fecundity compensation is one such life-history response, occurring when hosts increase their current reproductive output to make up for expected losses in future reproduction due to parasitic infection. However, the potential trade-offs between this increase in quantity and the quality of offspring have been relatively unexplored. This study uses the trematode, Schistosoma mansoni, and its snail intermediate host, Biomphalaria glabrata, to better understand how this host life-history response, fecundity compensation, impacts host reproduction. Measures of host reproductive output as well as offspring hatching success and survival were collected to assess the reproductive consequences of infection. Infected snails exhibited fecundity compensation by increasing the number of eggs laid and the overall probability of laying eggs compared to uninfected snails. Parental infection status did not play a significant role in hatching or offspring survival to maturity. Offspring from a later reproductive bout demonstrated a higher hatching success rate. Overall, the lack of an apparent trade-off between quantity and quality of offspring suggests that infected parental snails invest more resources towards reproduction not only to increase reproductive output, but also to maintain the fitness of their offspring, possibly at the expense of their own longevity.
The influences of different plants on herbivores have recently attracted research interest; however, little is known regarding the effects of wild, local and cultivated varieties of the same plant from the same origin on herbivores. This study aimed to examine the effects of different tobacco varieties from the same origin on the oviposition preference and offspring performance of Spodoptera litura. We selected two wild (‘Bishan wild tobacco’ and ‘Badan wild tobacco’), two local (‘Liangqiao sun-cured tobacco’ and ‘Shuangguan sun-cured tobacco’) and two cultivated (‘Xiangyan No. 5’ and ‘Cunsanpi’) tobacco varieties from Hunan Province, China. We found that female S. litura varied in oviposition preferences across the tobacco varieties. They preferred to lay eggs on the cultivated varieties, followed by the local varieties, with the wild varieties being the least preferred. Furthermore, different tobacco varieties significantly influenced the life history parameters of S. litura. Survival rate, pupal weight, emergence rate and adult dry weight decreased in the following order: cultivated varieties > local varieties > wild varieties. Conversely, the pupal stage and development period decreased in the following order: wild varieties > local varieties > cultivated varieties. Therefore, we conclude that wild tobacco varieties have higher resistance to S. litura than cultivated and local varieties, reflecting the evolutionary advantages of wild tobacco varieties.
The reproductive characteristics of co-occurring freespine flathead, Ratabulus diversidens, and mud flathead, Ambiserrula jugosa, that interact with fisheries across continental shelf waters of eastern Australia were examined. Samples were collected across three depth strata and two locations on a monthly basis over two years. Males of both species matured younger and at smaller total lengths (TL) than females. Estimated TL and age (years) at maturity (L50 and A50, respectively) of R. diversidens also varied between locations, but differences were not related to differential growth. Although some mature individuals of both species occurred year-round, they were most prevalent and gonadosomatic indices greatest, between the austral spring and autumn. Mature R. diversidens almost exclusively occurred in deeper offshore waters, whereas the opposite was evident for A. jugosa. Both species displayed asynchronous oocyte development, and were thus considered capable of spawning more than once throughout each spawning season. Potential batch fecundity was positively related to TL for R. diversidens, but not A. jugosa, possibly due to the small size of the latter species. The sex ratios for R. diversidens varied between locations and length categories, and like A. jugosa the larger categories were skewed towards females, a result of divergent growth between sexes. Macroscopic and microscopic evidence indicated both species were gonochoristic. The data provide new information for fisheries management consideration and contribute to the data-poor international knowledge base of platycephalid biology.
Aphids parasitized in later instars can give birth to several nymphs before their reproduction is curtailed by the developing parasitoid. We examined the life histories of Aphis fabae Scopoli born to mothers parasitized by Lysiphlebus fabarum Marshall, and their suitability as subsequent hosts, to test the ‘fecundity compensation’ hypothesis. Maternal parasitism negatively impacted life history parameters, resulting in reduced estimates of population increase (rm, R0, and λ), and increased generation time (GT) and doubling time (DT). These impacts were greater when the larva developing in the mother turned out to be female rather than male, and greater still when mothers were superparasitized. Maternal parasitism produced aphids with shorter hind tibia (HTL), at birth and at maturity, but their developmental time was unaffected. Although female L. fabarum readily accepted such aphids for oviposition, rates of mummification and wasp emergence were lower, and more so when the maternal parasitoid was female. The resulting parasitoids took longer to develop than progeny from control wasps, had shorter HTLs, lower egg loads, smaller eggs, and produced fewer mummies with lower rates of adult emergence, all differences that were more pronounced when the maternal parasitoid was female. The progeny of these wasps exhibited similar impairments to these biological parameters as their parents, demonstrating that the negative impacts of development in maternally parasitized hosts extended for at least two generations. Thus, our results do not support fecundity compensation, but suggest that any benefits of post-parasitism reproduction will be offset by reduced fitness in both aphid progeny and the parasitoids that develop in them.
Abundant species are typically also viewed as ecologically dominant, and are frequently used to characterize the communities in which they live. Such characteristic assemblages may also be used as indicators of environmental conditions, such as relative stability. Fossil and modern turritelline gastropods are often the most abundant species in the marine assemblages and communities in which they occur, forming ‘turritelline-dominated assemblages’ (TDAs). We use data on modern Turritella bacillum from waters around Hong Kong as a case study to analyse fluctuations in abundance over 25 years. While turritellines were not always dominant in the area surveyed (~1650 km2), populations were notably persistent, and rebound after decline of abundances occurred within ~5 years at some sites. δ18O sclerochronology suggests that individuals were ~1–2 years old. It is also notable that T. bacillum was found to be abundant at salinities as low as 10–15 psu, despite the general characterization of turritellines as fully marine. Comparison with data on modern T. communis in the western English Channel corroborates this pattern, as localized sites of high abundance also appear transient. These results have implications for the interpretation of TDAs in the fossil record: they may signify the cumulative result of short-lived, spatially restricted populations, possibly resulting from essentially stochastic larval settlement. This suggests that the palaeoenvironmental setting of fossil TDAs does not always control their occurrence on short temporal scales.