Changes In Reproductive Investment Research Articles

Variation in reproductive investment increases body temperature amplitude in a temperate passerine

Many birds and mammals show substantial circadian variation in body temperature, which has been attributed to fluctuations in ambient temperature and energy reserves. However, to fully understand the variation in body temperature over the course of the day, we also need to consider effects of variation in work rate. We made use of a dataset on body temperature during the resting and active periods in female marsh tits (Poecile palustris) that bred in a temperate area and were subjected to experimental changes in reproductive investment through brood size manipulations. Furthermore, the amplitude increased with daytime, but were unaffected by nighttime, ambient temperature. Amplitudes in females with manipulated broods were 44% above predictions based on inter-specific allometric relationships. In extreme cases, amplitudes were > 100% above predicted values. However, no individual female realised the maximum potential amplitude (8.5 °C, i.e. the difference between the highest and lowest body temperature within the population) but seemed to prioritise either a reduction in body temperature at night or an increase in body temperature in the day. This suggests that body temperature amplitude might be constrained by costs that preclude extensive use of both low nighttime and high daytime body temperatures within the same individual. Amplitudes in the range found here (0.5–6.7 °C) have previously mostly been reported from sub-tropical and/or arid habitats. We show that comparable values can also be found amongst birds in relatively cool, temperate regions, partly due to a pronounced increase in body temperature during periods with high work rate.

Seasonal change in male reproductive investment of a fish

Many animals are sexually dimorphic, whereby males may display brighter body coloration and more distinctive ornamentation than females. Fishes in temperate regions markedly change their energy allocation toward reproduction in response to the seasonal environment. Seasonal change in reproductive investment affects the expression of sexually dimorphic traits in males through gonadal weight change. Here, we report seasonal changes in body size, testis weight and sexual dimorphism of the fins (anal fin length and dorsal fin length) in the northern medaka Oryzias sakaizumii. Fish were collected periodically from a wild population (Aomori). Gonad weight increased from May to July in both males and females, corresponding to the reproductive season. Moreover, during this period, the degree of sexual dimorphism in fin length increased. To investigate the relationship between testis weight and individual differences in male fin length, we analyzed relationships among morphological traits using structural equation modeling. In the reproductive season, increased testis weight was associated with longer fin length in males, but the relationship disappeared after the reproductive season. These observations suggest that the sexually dimorphic fin in this fish is a mating signal. Results from a mating experiment also support this view. Males with larger size and/or longer fin attracted more mates than those with smaller fins, suggesting that sexual selection operates through females choosing to mate with males having longer fins.

Birds from matched developmental environments breed faster

The developmental environment an animal experiences can have a pervasive and sustained effect on phenotype throughout its life. Animals exposed to suboptimal conditions during development can experience physiological trade-offs, leading to seemingly negative phenotypic changes in later life that have been hypothesised to have detrimental effects on fitness. However, few studies have investigated how exposure to suboptimal developmental conditions affects an animal’s reproductive behavior and fitness. Here, we determine if elevated levels of corticosterone (CORT; the dominant avian stress hormone) during development affect fitness via changes in reproductive investment in adult zebra finches (Taeniopygia guttata). To do this, we exposed nestling zebra finches to either CORT supplemented or control treatments and assessed their mate selection and reproductive investment as adults, using free choice breeding experiments. We found that breeding pairs of birds from matched developmental treatments (CORT or control) had a shorter latency to lay clutches compared to pairs with mismatched developmental treatments. We found no indication that clutch size or egg mass were affected by developmental treatment. Also, we found no evidence that birds choose mates to match their own developmental treatment. Our results demonstrate that developmental experience may affect reproductive investment through changes to reproductive timing and add to the literature suggesting that pairs with similar developmental backgrounds can coordinate their reproduction more effectively. Developmental stress may reduce the fitness of a breeding pair as a result of its detrimental effect on phenotype and performance. Alternatively, individuals could use indicators of developmental stress to influence mate choice in order to compensate for a poor start to life. Previous studies suggest that birds do assortatively mate by developmental environment, but this has not been tested in a free choice mating context. Using a free choice breeding experiment, we show that pairs of breeding birds lay eggs faster when they have matching developmental environments, regardless of the quality of their developmental environment. This evidence suggests that assortatively mated pairs can potentially offset a bad start to life and maintain fitness in spite of the deleterious effects of developmental stress.

Impact of rising temperature on reproductive investment in a capital breeder: The lesser sandeel

Capital breeding, whereby adult's build-up energy reserves at times when food is abundant in order to invest in reproduction during a time of low prey availability, is common in seasonal environments. A dependence on stored energy for reproductive investment may make capital breeders sensitive to rising temperatures during winter when activity and energy demands are typically low. The lesser sandeel, Ammodytes marinus (Raitt, 1934), is an extreme capital breeder, as gonad development is entirely dependent on stored energy whilst the fish remains buried in sand overwinter. In this laboratory study, the energetic consequences of high and low overwintering temperatures on energy allocation to reproduction in A. marinus were examined. The laboratory conditions led to growth and mass changes that were consistent with previously published field observations. Loss in wet mass was greater in the high temperature treatment, consistent with the higher metabolic cost predicted. Despite this, somatic energy loss did not differ between the two temperatures, the difference in mass being related to the lower relative gonad size in the high temperature treatment. The negative effect of temperature on reproductive investment in A. marinus highlights that although temperature can have a permissive effect on reproductive development it is limited by available energy reserves. Based on these findings it seems likely that warming will lead to a change in reproductive investment in A. marinus that mature but will not impact their overwinter survival.

Are life-history strategies of Norway rats (Rattus norvegicus) and house mice (Mus musculus) dependent on environmental characteristics?

Context Life-history theory attempts to explain the way in which an organism is adapted to its environment as well as explaining the differences in life-history strategies among and within species. Aims The aim of this paper was to compare life-history traits of the Norway rat and the house mouse living in different habitats and geographic regions so as to find patterns related to environmental characteristics on the basis of published ecological studies conducted before 2011. Methods The environments where rodent populations lived were characterised according to climate type, occurrence of freezing temperatures and frost, degree of anthropisation and trapping location. Four demographic characteristics were analysed. A canonical correspondence analysis was performed to explain the effects of environmental variables on the demographic characteristics of rodents. Information was gathered from 35 articles published between 1945 and 2010. Key results Most populations of both species showed differences in abundance throughout the year, but no defined pattern was common among populations. The pregnancy rate of Norway rat was highest during spring and autumn in urban environments, during spring and winter in rural environments and during summer in sylvan habitats. House mouse populations were most frequently reported to experience high pregnancy rates during summer. Contrary to urban and rural populations, in sylvan environments the occurrence of a reproductive break was the most commonly reported pattern for both species. Litter size of Norway rat depended on the degree of anthropisation and the occurrence of freezing temperatures and frost. Litter size was greater in rural environments and in areas without freezing temperatures and frost. House mouse did not show differences in litter size resulting from any of the environmental characteristics analysed. Conclusions Both species are able to modify their reproductive strategies according to environmental characteristics, especially according to the degree of anthropisation of the environment. In sylvan areas, where animals are more exposed to seasonal changes in weather conditions, changes in reproductive investment are more evident. Implications Regarding the implications for rodent control, the best time to apply control measures could be winter in sylvan and urban environments. In rural environments, the best time for conducting control efforts is less clear, although cold seasons seem also to be the best.

Direct and size‐dependent effects of climate on flowering performance in alpine and lowland herbaceous species

AbstractQuestionsEffects of climate on flowering performance are often investigated independently of plant size. We ask how temperature and precipitation impact flowering probability and flower production: via direct effects, size‐dependent indirect effects, changes in minimum size for flowering and/or changes in reproductive investment.LocationTwelve calcareous grasslands in western Norway (4°50′–8°45′ E, 60°20′–61°50′ N).MethodsThe investigations were carried out at the rear temperature edge of alpine plants and at the leading temperature edge of lowland plants to capture the variety of climate responses occurring in different parts of species climate niches within our study landscape. The study was conducted within a natural ‘climatic grid’ consisting of temperature gradients replicated along a precipitation gradient. In each study site, we sampled populations of two alpine (Viola biflora, Veronica alpina) and two lowland (Viola palustris, Veronica officinalis) species. The relative importance of each effect was assessed under a 2 °C increase in mean summer temperature and a 10% increase in annual precipitation.ResultsFlowering was climate‐ and size‐dependent in all species except Viola palustris. Both direct climate effects and climate‐driven variation in reproductive investment were detected for the three other species. Indirect climate effects were detected for Veronica officinalis, and climate‐driven variation in minimum size for flowering in Viola biflora. Climatic responses were not consistent within or between distributional types (alpine vs lowland) or genera. A temperature increase of 2 °C was predicted to increase flower production by 22% for Veronica alpina and by 74% for Veronica officinalis. A precipitation increase of 10% had a limited impact on Viola biflora flowering probability (0.08% increase) and increased Veronica officinalis flower production by 1.7%.ConclusionsOur study shows that climate affects flowering performance both directly and through size dependence. Understanding such size‐dependent responses to climate is important for our understanding of how climate change will affect flowering performance and recruitment in plant populations.

Size-, energy- and stage-dependent fecundity and the occurrence of atresia in the Northeast Arctic haddock Melanogrammus aeglefinus

The Northeast Arctic (NEA) haddock (Melanogrammus aeglefinus) population size has fluctuated greatly over the last few decades. Such fluctuations may be influenced by changes in reproductive investment, yet no fecundity study on this population has been undertaken since 1974 with which to address such a concept. We therefore estimated potential fecundity of >350 NEA haddock caught in February–March 2009–2011 and correlated this with potential fecundity proxies, i.e. female age, length, relative liver size and somatic condition and leading oocyte cohort development (diameter) (LC20). We also examined the incidence (prevalence) and intensity of atresia in histological ovary sections. Finally, we estimated population (total) egg production (TEP) for NEA haddock in 2010 and 2011. Fecundity was mainly determined by length, although it was also positively associated with our metric of liver size and somatic condition. Fecundity decreased with LC20, indicating atresia, confirmed by the direct observation of atresia in histological sections (n=185). Although 45% of the females possessed atretic oocytes, the intensity of atresia was low, typically only 1–5% of the oocytes with yolk granules were atretic, complete reabsorption of all vitellogenic oocytes was not observed. Our proxies give no indication of any change in reproductive investment for NEA haddock in the last few decades. The present study confirms the importance of liver and white muscle energy for oocyte recruitment and shows atretic down-regulation in NEA haddock. Further, NEA haddock females whose oocytes reach the yolk granule stage will likely spawn. NEA haddock TEP for females aged 4–8 years was estimated to be 4.5×1013 and 2.9×1013 in 2010 and 2011, respectively.

Fisheries-induced evolution in growth, maturation and reproductive investment of the sexually dimorphic North Sea plaice ( Pleuronectes platessa L.)

Changes in the onset of sexual maturation, reproductive investment and growth of North Sea plaice are studied between three periods: 1900s, 1980s and 2000s. Probabilistic maturation reaction norms of both males and females, describing the probability of becoming mature conditional on age and size, shifted towards smaller sizes and younger ages, indicating a fisheries-induced evolutionary change. A higher rate of change was observed during the past 20 years, which may be related to higher temperature conditions. Reproductive investment was estimated from the decrease in lipid, protein, dry weight content and condition factor of the whole body between pre- and post-spawning adults. Reproductive investment expressed as the energy loss over the spawning period increased with body size from 19% at 20 cm to 30% at 40 cm in males and from 35% at 30 cm to 48% at 50 cm in females. No change in reproductive investment could be detected between the 1980s and the 2000s. Von Bertalanffy (VB) growth parameters showed a decrease in L ∞ the asymptotic size and an increase in K, the velocity to reach L ∞, in both males and females. The changes in VB growth are consistent with an increase in energy acquisition and reproductive investment. The observed changes in maturation, reproductive investment and growth are consistent with fisheries-induced evolution, but the changes in reproductive investment and growth need further investigation to disentangle the role of phenotypic plasticity.

Changes in reproductive investment with altitude in an alpine plant

In perennial species, the allocation of resources to reproduction results in a reduction of allocation to vegetative growth and, therefore, impacts future reproductive success. As a consequence, variation in this trade-off is among the most important driving forces in the life-history evolution of perennial plants and can lead to locally adapted genotypes. In addition to genetic variation, phenotypic plasticity might also contribute to local adaptation of plants to local conditions by mediating changes in reproductive allocation. Knowledge on the importance of genetic and environmental effects on the trade-off between reproduction and vegetative growth is therefore essential to understand how plants may respond to environmental changes. We conducted a transplant experiment along an altitudinal gradient from 425 to 1 921 m in the front range of the Western Alps of Switzerland to assess the influence of both altitudinal origin of populations and altitude of growing site on growth, reproductive investment and local adaptation in Poa alpina. In our study, the investment in reproduction increased with plant size. Plant growth and the relative importance of reproductive investment decreased in populations originating from higher altitudes compared to populations originating from lower altitudes. The changes in reproductive investment were mainly explained by differences in plant size. In contrast to genetic effects, phenotypic plasticity of all traits measured was low and not related to altitude. As a result, the population from the lowest altitude of origin performed best at all sites. Our results indicate that in P. alpina genetic differences in growth and reproductive investment are related to local conditions affecting growth, i.e. interspecific competition and soil moisture content.

Evolution of growth in Gulf of St Lawrence cod?

Fishing is often size selective such that the likelihood of capture increases with body size. It has therefore been postulated that fishing could favour evolution of slower growth because smaller size would reduce exposure to fishing gear (e.g. [Ricker 1981][1]). A recent study by Swain et al . ([

Decreased reproductive investment of female threespine stickleback Gasterosteus aculeatus infected with the cestode Schistocephalus solidus: parasite adaptation, host adaptation, or side effect?

Parasitic infections may cause alterations in host life history, including changes in reproductive investment (absolute amount of energy allocated to reproduction) and reproductive effort (proportion of available energy allocated to reproduction). Such changes in host life history may reflect: 1) a parasite tactic: the parasite adaptively manipulates energy flow within the host so that the host is induced to make a reduction in reproductive effort and reproductive investment, making more energy available to the parasite; 2) no tactic: there is no change in host reproductive effort and reproductive investment simply decreases as a side effect of the parasite depleting host energy stores; 3) a host tactic: the host adaptively increases reproductive effort in the face of infection and loss of body condition, reproductive investment possibly being reduced despite the increased reproductive effort. Females in Alaskan lake populations of threespine sticklebacks (Gasterosteus aculeatus) are capable of clutch production when parasitized by the cestode Schistocephalus solidus despite large relative parasite masses. We analyzed the somatic energy reserves, maturation stage and ovarian mass of female sticklebacks collected from an Alaska lake during a single reproductive season. We found that parasitized females were less likely to carry fully‐matured gametes, had smaller ovarian masses, and had lower somatic energy stores than unparasitized females. The relationship between reproductive investment and energy storage did not differ between parasitized and unparasitized females. Thus, reproductive effort did not change in response to parasitic infection. We conclude there was no indication of either a parasite tactic or a host tactic. Simple nutrient theft is involved in the parasite's influence on host reproduction, consistent with an earlier hypothesis that reproductive curtailment in threespine sticklebacks is a side effect.

Fisheries-induced adaptive change in reproductive investment in North Sea plaice (Pleuronectes platessa)?

Life history theory predicts that fishing may select for increased reproductive investment. A model of the reaction norm for reproductive investment in a capital breeder was developed to disentangle changes in reproductive investment from changes in growth rate in North Sea plaice (Pleuronectes platessa). Trends in reproductive investment since 1960 were estimated as (i) the decrease in body weight of mature males and females between the start and end of the spawning period, (ii) the difference in weight of ripe and spent females, and (iii) the ovary weight of prespawning females. These estimates were related to somatic growth estimated by back-calculation of otoliths and temperature. The ovary weight and weight loss of females that had just started and just finished spawning did not reveal any trends. There was a significant increase in weight loss over the spawning season in both sexes, but much of this increase was likely due to changes in environmental conditions. Evidence for a fisheries-induced change in reproductive investment from our analyses thus remained inconclusive. However, fecundity and ovary-weight data from previous studies tentatively suggest that an increase in reproductive investment occurred between the late 1940s and the 1960s. Such an increase is consistent with a fisheries-induced evolutionary change.

Somatic senescence: evidence from female Richardson's ground squirrels

We studied reproductive and somatic investments in >700 female Richardson's ground squirrels (Spermophilusrichardsonii) of known age over a 14‐year period to evaluate three hypotheses, restraint, senescence, and residual reproductive value, proposed to explain age‐specific life history patterns in iteroparous vertebrates. We found that reproductive investment, measured as litter mass at first emergence from the natal nest, did not differ among age classes. Although yearling female Richardson's ground squirrels made a greater somatic investment during reproduction than older females, they produced similar numbers and mass of offspring as older females. Reproductive investment did not decline with age, though active season somatic investment was lowest in the oldest females. Somatic investment during reproduction was highest in yearlings. This combination of age‐related changes in somatic investment unaccompanied by changes in reproductive investment was not well explained by any of the hypotheses examined, though the senescence hypothesis best explained the combination of declining somatic investment and declining survival of the oldest females. Our results supported the ideas that reproductive and somatic senescence evolve independently, and that somatic senescence may be more common in relatively smaller species.

Temporal and spatial variation in reproductive investment of Atlantic cod Gadus morhua in the northern North Sea and Scottish west coast

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 276:237-248 (2004) - doi:10.3354/meps276237 Temporal and spatial variation in reproductive investment of Atlantic cod Gadus morhua in the northern North Sea and Scottish west coast Michio Yoneda1,2,*, Peter J. Wright1 1Fisheries Research Services Marine Laboratory, PO Box 101 Victoria Road, Aberdeen AB11 9DB, UK 2Present address: Tohoku National Fisheries Research Institute, Shinhama, Shiogama, Miyagi 985-0001, Japan *Email: myoneda@fra.affrc.go.jp ABSTRACT: The recent decline in many fish stocks has been accompanied by marked changes in age at maturity. However, there is little information on whether other components of reproductive investment have changed and the relative roles of phenotypic plasticity or genetic selection in such change. This study explored how reproductive investment in cod Gadus morhua from different regions around Scotland has changed between a period of high (1969, 1970) and low (2002, 2003) spawning-stock size. Maturity ogives indicated that inshore North Sea cod now mature at a smaller size and younger age than they did around 1970. The relationship between potential fecundity and size indicated that cod in the inshore region are now more fecund than 30 yr ago. Cod from the inshore region of the North Sea now have a higher fecundity at a given size and age than cod from the offshore region and the west of Scotland. There was no such spatial trend around 1970. Similarly, whilst the relative fecundity of cod in recent times is positively correlated with age, no such relationship was evident in 1969 and 1970. Nutritional influences on maturity and fecundity, particularly liver condition, were also evident from the recent study. However, the temporal and spatial differences in fecundity-size relationships were not consistent with a change in growth conditions, as there has been a significant decrease in body condition in recent times. Our findings regarding the temporal change in reproductive investment in the inshore North Sea region appear consistent with genotypic changes in life-history traits predicted to arise from intense periods of size-selective mortality. KEY WORDS: Cod · North Sea · Maturity · Fecundity · Nutritional status · Population dynamics · Life-history traits Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 276. Online publication date: August 02, 2004 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2004 Inter-Research.

Changes in Reproductive Investment following Caudal Autotomy in Viviparous Skinks (Niveoscincus metallicus): Lipid Depletion or Energetic Diversion?

The effect of caudal autotomy on reproductive investment in females of a viviparous skink, Niveoscincus metallicus, was investigated to examine the relative importance of lipid depletion and energetic diversion to this activity. Although abdominal fat bodies are present, this species stores most of its energetic reserves in the tail. Since caudal fat is preferentially aggregated toward the base of the tail, autotomy and lipid depletion may be mutually exclusive events. Reproductive consequences following tail loss associated with significant loss of caudal fat were compared with those following autotomy involving no fat loss in two groups of females: females that had lost their tail during their most recent vitellogenic period; and females in which tail loss had occurred in a previous reproductive season. Caudal autotomy during vitellogenesis resulted in a significant reduction in litter size, irrespective of the position of tail loss, suggesting that smaller litters were a consequence of the diversion of energetic resources from reproduction to tail regeneration, rather than the loss of fat reserves per se. However, offspring from mothers that experienced tail loss during vitellogenesis without associated loss of fat reserves were significantly larger in size (snout–vent length and mass) and had longer tails than those from any other group. We suggest that this was probably achieved through facultative placental transfer during gestation, although the possibility that more yolk was allocated to each egg cannot be discounted. Sprint speed and the size of abdominal fat reserves at birth and postnatal growth were not correlated with either recency of autotomy or the location of the tail break.

Changes in Reproductive Investment Following Caudal Autotomy in Viviparous Skinks (Niveoscincus metallicus): Lipid Depletion or Energetic Diversion?

The effect of caudal autotomy on reproductive investment in females of a viviparous skink, Niveoscincus metallicus, was investigated to examine the relative importance of lipid depletion and energetic diversion to this activity. Although abdominal fat bodies are present, this species stores most of its energetic reserves in the tail. Since caudal fat is preferentially aggregated toward the base of the tail, autotomy and lipid depletion may be mutually exclusive events. Reproductive consequences following tail loss associated with significant loss of caudal fat were compared with those following autotomy involving no fat loss in two groups of females: females that had lost their tail during their most recent vitellogenic period; and females in which tail loss had occurred in a previous reproductive season. Caudal autotomy during vitellogenesis resulted in a significant reduction in litter size, irrespective of the position of tail loss, suggesting that smaller litters were a consequence of the diversion of energetic resources from reproduction to tail regeneration, rather than the loss of fat reserves per se. However, offspring from mothers that experienced tail loss during vitellogenesis without associated loss of fat reserves were significantly larger in size (snout–vent length and mass) and had longer tails than those from any other group. We suggest that this was probably achieved through facultative placental transfer during gestation, although the possibility that more yolk was allocated to each egg cannot be discounted. Sprint speed and the size of abdominal fat reserves at birth and postnatal growth were not correlated with either recency of autotomy or the location of the tail break.