Does a trade‐off between current reproductive success and survival affect the honesty of male signalling in species with male parental care?

Recent theory predicted that male advertisement will reliably signal investment in paternal care in species where offspring survival requires paternal care and males allocate resources between advertisement and care. However, the predicted relationship between care and advertisement depended on the marginal gains from investment in current reproductive traits. Life history theory suggests that these fitness gains are also subject to a trade‐off between current and future reproduction. Here, we investigate whether male signalling remains a reliable indicator of parental care when males allocate resources between current advertisement, paternal care and survival to future reproduction. We find that advertisement is predicted to remain a reliable signal of male care but that advertisement may cease to reliably indicate male quality because low‐quality males are predicted to invest in current reproduction, whereas higher‐quality males are able to invest in both current reproduction and survival to future reproduction.     

Will male advertisement be a reliable indicator of paternal care,if offspring survival depends on male care?

Existing theory predicts that male signalling can be an unreliable indicator of paternal care, but assumes that males with high levels of mating success can have high current reproductive success, without providing any parental care. As a result, this theory does not hold for the many species where offspring survival depends on male parental care. We modelled male allocation of resources between advertisement and care for species with male care where males vary in quality, and the effect of care and advertisement on male fitness is multiplicative rather than additive. Our model predicts that males will allocate proportionally more of their resources to whichever trait (advertisement or paternal care) is more fitness limiting. In contrast to previous theory, we find that male advertisement is always a reliable indicator of paternal care and male phenotypic quality (e.g. males with higher levels of advertisement never allocate less to care than males with lower levels of advertisement). Our model shows that the predicted pattern of male allocation and the reliability of male signalling depend very strongly on whether paternal care is assumed to be necessary for offspring survival and how male care affects offspring survival and male fitness.     

Life history evolution in cichlids 1: revisiting the evolution of life histories in relation to parental care

Empirical links between egg size and duration of parental care in fishes have generated a considerable amount of theory concerning life history evolution. However, to date, this link has not been investigated in relation to other important life-history traits such as clutch size and body size, or while controlling for shared ancestry between species. We provide the first phylogenetically based tests using a database with information on egg size, clutch size, body size and care duration in cichlid fishes (Cichlidae). Multiple regression analyses, based on independent contrasts on both the species and the genus level, showed that clutch size is the variable most closely related to duration of care. This pattern appeared to be driven by post-hatch care relationships. Our results show that, contrary to expectation, there is no positive link between egg size and care duration in Cichlidae. Instead, greater reproductive output through increased clutch size investment appears to have coevolved with greater care of offspring. We suggest that re-evaluation of the generality of current models of the evolution of egg size under parental care in fishes is needed.     

进化生态学的产生与发展

进化论、遗传学与生态学是在不同时期发展起来的独立学科,然而,随着科学的发展,们越来越认识到它们之间存在着密切的关系。Petrusewicz(1959)(见Shvarts,1977)曾写过《达尔文进化论是一种生态理论》一书,强调进化在本质上是一生态过程。Hutchinson(1965)写了一部题名为《生态学舞台和进化节目》一书,认为生态的布景可以作为进化过程的舞台。但是,最早提出进化生态学这一概念的则是Orians(1962)。进化生态学从产生到现在虽然只有20多年的历史,但已成为生态学研究的重要领域。下面从几个方面谈谈进化生态学的产生与发展。     

Where are all the moms? External fertilization predicts the rise of male parental care in bony fishes

Parental care shows remarkable variation across the animal kingdom, but while maternal and biparental care are common in terrestrial organisms, male‐only care dominates in aquatic species that provide care. Using the most complete phylogenetic tree of bony fishes to date, we test whether the opportunity for external fertilization in aquatic environments can explain the more frequent evolution of male care in this group. We show that paternal care has evolved at least 30 times independently in fish and is found exclusively in externally fertilizing species. Male care is positively associated with pair spawning, suggesting that confidence in paternity is an important determinant of the evolution of care. Crucially, while female care is constrained by other forms of reproductive investment, male care occurs more frequently when females invest heavily in gamete production. Our results suggest that moving control of fertilization outside of the female reproductive tract raises male confidence in parentage and increases the potential for paternal care, highlighting that in an aquatic environment in which fertilization is external, paternal care is an effective reproductive strategy.     

A cost of maternal care in the dung beetle Onthophagus taurus?

Parental care theory assumes that investment in current offspring will trade against future investment. A number of field studies on birds have used clutch size manipulations to demonstrate a survival cost to chick rearing. However, such studies do not account for costs accrued during earlier stages of reproduction because not all aspects of reproductive effort are manipulated by varying the number of nestlings. In this study, we investigate the effect of reproductive effort on female survival in the dung beetle, Onthophagus taurus. By experimentally manipulating mating status and dung availability, we demonstrate that virgin females survive longer than mated females and that the survival of mated females was negatively associated with the number of brood masses produced. Using a novel manipulation of the mating system, we separated the effects of egg production and maternal care on female survival. Previously, we have shown that females provisioning with the assistance of a major male provide relatively less care than unassisted females. However, paternal assistance did not alter the number of brood masses produced and hence the amount of reproductive effort that was allocated to egg production. Therefore, our finding that female survival was increased when receiving paternal assistance provides, to our knowledge, the first definitive evidence that maternal care reduces female lifespan. These results are of major importance to theoretical models on the evolution of parental care.     

Verhalten von Kranichfamilien (Grus grus) in Brutrevieren Nordostdeutschlands: Investition der Altv?gel in ihre Nachkommen

Zusammenfassung Junge Graukraniche haben einen weniger guten Jagderfolg bzw. eine geringere Rate bei der Nahrungsaufnahme als Altvögel. Dieses Defizit sollte durch die elterliche Investition bei der Jungenaufzucht kompensiert werden. Untersuchungen zum Zeitbudget und zum Aufwand aus dem Brutgebiet fehlen bisher. Mit Hilfe markierter Jungkraniche (Farbringe, Sender) wurde das Verhalten der Eltern und ihrer Nachkommen erfasst, um die Investitionen in Beziehung zum Reproduktionserfolg zu analysieren. Die Eltern sicherten mit 39,6% fast viermal so häufig wie Altvögel ohne Junge (Übersommerer). Bei Paaren mit zwei Nachkommen waren diese Aufwendungen höher als bei Paaren mit nur einem Jungvogel. Das Weibchen profitierte vom verstärkten Sichern des Männchens (Männchen: durchschnittlich 43,9%, Weibchen 35,3%) und konnte so vermutlich schneller seine Investition in die Gelegeproduktion ausgleichen. Die Revierverteidigung bzw. Feindabwehr übernahmen meist die Männchen. Die Beteiligung des Männchens förderte den Aufzuchterfolg, der auf zwei Junge begrenzt ist. Die Jungen profitierten von den Leistungen ihrer Eltern. Sie konnten mit geringem Sicherungsaufwand (11,9%) Nahrung suchen (67,7%, Eltern 42,8%) und so ihre geringere Aufnahmerate kompensieren. 77,9% der Jungkraniche überlebten vom Zeitpunkt des Markierens im Juni bis zum Abzug ins Überwinterungsgebiet im Oktober/November (84% der Einzeljungen und 75% bei Familien mit zwei Nachkommen).Junge Kraniche müssen einen wesentlichen Teil des Tages Nahrung aufnehmen, um den Energiebedarf für ein schnelles Wachstum sicherzustellen. Bei einer negativen Energiebilanz aufgrund zu vieler Störreize können die Erfolge bei der Jungenaufzucht sinken. Im Rahmen der Landschaftsplanung ist vor allem in Räumen mit einer hohen Siedlungsdichte des Kranichs auf eine stärkere Bebauung (z. B. mit Windkraftanlagen) oder Zerschneidung durch weitere Verkehrswege und Energieleitungen zu verzichten.

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Behaviour of Crane (Grus grus) families in their breeding territories in Northeast Germany: parental care and investment

Summary Juveniles and immature birds normally have less foraging ability and a lower food intake rate than adults. This — it has been presumed — is compensated for by parental care and investment during juvenile development. Studies of time budgets and parental investment of Common Cranes were carried out in the years 1995 to 1999 in Northeast Germany. Having first marked young Cranes (colour rings, radio transmitters), we analysed the behaviour of parents and offspring to correlate this with reproductive success. Parents with young (39.6%) were four times more vigilant than non-breeders. The investment of pairs with two young was significantly (p<0.001) higher than in pairs with only one young. Females profited from the high vigilance rate of their males (males mean 43.9%, females 35.3%) and were thus able probably to compensate for their investment in the clutch faster because of higher food intake. Defence of the territory against other cranes and defence against predators were tasks mostly undertaken by males. If the males participated in the rearing of the young, the pair were able to rear two juveniles to fleding.The young profited from parental care. They were able to feed most of the time (67.7%) with lower vigilance costs (11.9%; 27.7% less than parents), and thus possibly compensated for their lower feeding success. Rearing of two young, however, must be the upper limit of possible investment of adults. So far there has been no evidence of families with three grown-up young in a stopover region or on the wintering grounds. The survival of juveniles from the date of ringing in June up to the migration to the wintering sites in mid-November amounts to 77.9%, with 84% for families with one young and 75% for those with two young. Accordingly the reproductive success was higher for pairs with two young (1.32 juv./pair) than with one young (0.84 juv/pair).The long-term survival of the population in a man-made landscape is only possible with an appropriate reproductive success. The offspring of crane families have to feed throughout the major part of the day in order to gain their energy for the high metabolic rate during growth. With a negative energy balance because of too much disturbance, the reproductive success will decrease. Future landscape planning should avoid new traffic structures, buildings (e.g. wind turbines) or power lines at least in areas of high crane density.

     

Flexibility in reproductive timing in human females: integrating ultimate and proximate explanations

From an ultimate perspective, the age of onset of female reproduction should be sensitive to variation in mortality rates, and variation in the productivity of non-reproductive activities. In accordance with this prediction, most of the cross-national variation in women's age at first birth can be explained by differences in female life expectancies and incomes. The within-country variation in England shows a similar pattern: women have children younger in neighbourhoods where the expectation of healthy life is shorter and incomes are lower. I consider the proximate mechanisms likely to be involved in producing locally appropriate reproductive decisions. There is evidence suggesting that developmental induction, social learning and contextual evocation may all play a role.     

A bibliography and categorization of bony fishes exhibiting parental care

Parental care occurs in a diversity of fishes, but predominantly among freshwater groups. Among the approximately 422 families of bony fishes (Osteichthyes), 89 are presently known to exhibit parental care. Grouping these families into eight categories, based on the sex of the care-giver(s), reveals male parental care is as common or more common than female parental care. Although unusual among vertebrates, parental care by males alone is very common among bony fishes. Lists of families, the forms of parental care exhibited, the modes of fertilization, the environments in which reproduction occurs, and the sources of documentation are presented. An extensive bibliography and index are provided.