Phenotypic Plasticity In Reproductive Traits Research Articles

Phenotypic Plasticity in Reproductive Traits of the Perennial Shrub Ulex europaeus in Response to Shading: A Multi-Year Monitoring of Cultivated Clones.

Phenotypic plasticity may be advantageous for plants to be able to rapidly cope with new and changing environments associated with climate change or during biological invasions. This is especially true for perennial plants, as they may need a longer period to respond genetically to selective pressures than annuals, and also because they are more likely to experience environmental changes during their lifespan. However, few studies have explored the plasticity of the reproductive life history traits of woody perennial species. This study focuses on a woody shrub, Ulex europaeus (common gorse), and on the response of its reproductive traits to one important environmental factor, shading. The study was performed on clones originating from western France (within the native range of this invasive species) and grown for seven years. We compared traits of plants grown in a shade treatment (with two successive shade levels) vs. full natural light. The traits monitored included flowering onset, pod production and seed predation. All traits studied responded to shading, exhibiting various levels of plasticity. In particular, dense shade induced a radical but reversible decrease in flower and pod production, while moderate shade had little effect on reproductive traits. The magnitude of the response to dense shade depended on the genotype, showing a genetically based polymorphism of plasticity. The level of plasticity also showed substantial variations between years, and the effect of environmental variations was cumulative over time. This suggests that plasticity can influence the lifetime fitness of U. Europaeus and is involved in the capacity of the species to grow under contrasting environmental conditions.

Phenotypic plasticity of reproductive traits in response to food availability in invasive and native species of nematode

Invasive species cause severe ecological and economic damage; however, the mechanisms underlying their successful invasion often remain elusive. In the case of Bursaphelenchus xylophilus, a global quarantine pest which invaded Asia and Europe, it has been suggested that this species possesses highly competitive abilities, which promotes its establishment and rapid spread. To explore biological traits that may explain its highly competitive abilities, we focused on expression of phenotypic plasticity in response to the food conditions experienced by the females during their development as juveniles in the invasive species B. xylophilus and native species Bursaphelenchus mucronatus. We report an unexpected significant difference of phenotypic trade-off between egg number and egg size in the invasive species B. xylophilus and native species B. mucronatus. This leads to superior propagation ability of invasive species, under high and low food conditions in culture. These effects reflect adaptive optimal resource allocation where more eggs are produced in favorable environments to enhance population viability. Furthermore, we show that B. xylophilus eggs hatched earlier than B. mucronatus when their parents experienced high food availability. Thus, this study revealed, for the first time, phenotypic plasticity of reproductive traits in B. xylophilus which empowers the species a competitive advantage relative to their native counterpart B. mucronatus when they are under different range of food availability. These results are a step towards answering the vital question of how an exotic invasive species exclude a native species from its original niche.

Phenotypic plasticity in the reproductive traits of a parasitoid

Organisms show phenotypic plasticity – the capacity for a given genotype to express different phenotypes – in response to changes in the environment. Among the several factors that can cause phenotypic plasticity, nutritional constraints during development can affect the size of organisms and, consequently, affect most life-history traits, including reproductive traits. As their larvae are restricted by the amount of food contained in their host, parasitoids are a good model to study phenotypic plasticity related to size. The phenotypic plasticity of reproductive traits was investigated in the egg parasitoid Trichogramma euproctidis (Hymenoptera: Trichogrammatidae) by using host species of different sizes. Adult size, sperm storage organs (seminal vesicles and spermatheca), number of sperm stored and gamete size (sperm and oocyte) are all influenced by the host species; larger individuals have larger organs which contain more sperm, and both sperm and oocytes are correlated with adult size. However, while females become larger than males and mature larger oocytes in larger hosts, increase in sperm length stops after a given threshold.

Phenotypic plasticity of reproductive traits in response to food availability and photoperiod in white-footed mice (Peromyscus leucopus)

Although most temperate-zone mammals are seasonal breeders, many populations display variation in winter reproductive phenotype. For most mammals, the primary environmental cues regulating reproductive status are food availability and photoperiod, and these two factors can interact in their effect. Low food availability is primarily thought to suppress reproduction by reducing body mass and thereby forcing energy allocations to survival alone. However, because most small mammals rely on an increase in food intake rather than stored nutrients for reproduction, we hypothesized that food availability could act as a signal for low resource availability and affect reproduction even when body condition was not affected. We tested the prediction that restricted food access, without reduced body mass, could alter reproductive responses to short photoperiod. We used genetically distinct lines of white-footed mice (Peromyscus leucopus) derived from a wild population with genetic variation in the neuroendocrine pathway that regulates reproduction in response to environmental cues. The lines were created by artificial selection on gonad size in short photoperiods. Individuals from one line strongly suppress gonadal development in response to short photoperiods, while individuals from the other line suppress gonadal development weakly or not at all. Unresponsive individuals from the selected and an unselected control line were exposed to an intermittent food access protocol that did not affect body mass and only slightly reduced total food intake. We found that restricting food access caused reproductive suppression in short photoperiods but not long photoperiods, with no decrease in body mass. These results provide evidence for an interaction between food and photoperiod that is not dependent upon body condition or energy balance. The results also demonstrate plasticity in the reproductive response to photoperiod of otherwise reproductively nonphotoperiodic white-footed mice.

Phenotypic plasticity in reproductive traits induced by food availability in a lacertid lizard, Takydromus septentrionalis

Understanding the proximate determinants of phenotypic variations in life‐history traits can provide powerful insights into a species’ life‐history strategies. I experimentally manipulated availability of food (high vs low) to examine plasticity in the reproductive traits of northern grass lizards, Takydromus septentrionalis (Lacertidae), from eastern China. Food availability significantly affected reproductive frequency and thereby seasonal reproductive output, but had little effect on reproductive output per clutch. Low‐food females postponed reproduction and produced less clutches in the reproductive season than did high‐food females. After producing their second clutches, low‐food females were in lower body condition than the high‐food counterparts. By the end of the experiment, however, all females exhibited similar body condition. Clutch size and clutch mass differed between the first and second clutches but not between the treatments. Egg size and phenotypic traits of hatchlings (body size, morphology and locomotor performance) in T. septentrionalis did not vary significantly from first to second clutches nor between the two treatments. These results support optimal egg size (offspring) theory. Female T. septentrionalis “decide” whether or not to reproduce largely based on current energy intake; lowered feeding rates thus delay oviposition and reduce reproductive frequency. In contrast, clutch size, egg size and relative clutch mass remain unchanged.

Ecotypic differentiation and phenotypic plasticity in reproductive traits of Armadillidium vulgare (Isopoda: Oniscidea)

Armadillidium vulgare differed in growth and survivorship on two field sites. Growth rates were higher at a site with consistently higher quality food than at the other site where less high-quality food was produced and which was less predictably accessible. Survivorship was higher at the second site where temperature fluctuations were consistently smaller. Individuals from the two populations were kept for 6 months under the same food and temperature conditions and patterns of resource allocation to reproductive traits analysed. Members of the population from the site with good growth conditions had significantly higher reproductive allocation, by 13.5%, and larger broods, by 9.1%, than those from the site with poor growth conditions. Contrary to theoretical predictions, they also had significantly larger offspring, by 7.5% dry mass. Larger offspring survived better than small ones. This differential survivorship, by 20% for a 3.4% difference in live mass, was much more pronounced under conditions of moisture stress and under fluctuating temperature regimes. Larger offspring would therefore be at a selective advantage on the site with more severe temperature fluctuations. Phenotypic plasticity in reproductive traits in response to experimental changes in food quality, temperature and crowding were monitored. Reproductive allocation was increased by 20.8% under conditions of higher food quality, by 14.7% at higher temperatures, and by 12.5% under less crowded conditions. Brood size, but not offspring dry mass, increased when food quality increased. When crowding increased by 25.0%, the size of broods remained the same but the dry mass of individual offspring decreased by 11.2%. Members of the population from the site with more variable access to high-quality food showed more plasticity in reproductive traits in response to changes in food supply than members of the population from the site with the more predictable food supply. Members of the population from the site with more stable temperatures showed less plasticity to temperature changes than members of the population from the site with greater temperature fluctuations. It is concluded that the observed microevolutionary processes and phenotypic plasticity have adaptative value as responses to spatial and temporal heterogeneity in environmental conditions.

Phenotypic plasticity in reproductive traits: geographical variation in plasticity in a viviparous snake

Summary Previous experiments showed that Checkered Garter Snakes (Thamnophis marcianus) from south Texas, USA (an environment subject to high seasonal and annual variation in environmental conditions), demonstrated marked phenotypic plasticity in clutch size and clutch mass in response to experimental changes in prey availability. In this study, the extent of phenotypic plasticity in life‐history traits in Checkered Garter Snakes from south Texas was experimentally compared with a population of the same species from south‐eastern Arizona, where the environment may be more constant. Unlike results from south Texas, Checkered Garter Snakes from Arizona showed no significant phenotypic plasticity in clutch size, clutch mass or any other life‐history trait in response to changes in food availability, at least within the boundaries of our experimental conditions. The data indicate that the degree of phenotypic plasticity in life‐history traits differs among populations within the same species. However, these differences are subject to both adaptive and non‐adaptive explanations.

Annual variations in the reproductive traits of Pomatoschistus microps in a Mediterranean lagoon undergoing environmental changes: evidence of phenotypic plasticity

The spawning period of the common goby Pomatoschistus microps from 1993 to 1997 in the Vaccarès lagoon did not vary, except in 1997 when it was longer due to the reproduction of the young‐of‐the‐year. Egg size and number, and reproductive allocation varied greatly with one year to another. Female common gobies increased both their fecundity per spawning act and their egg size from 1993 to 1995. The annual variation in the reproductive effort suggests a high phenotypic plasticity of reproductive traits in P. microps, in the face of environmental perturbations. In winter 1993–1994, a centennial flood of the Rhône River caused major hydrological changes in the lagoon in less than 1 week, affecting many invertebrates and fish for several years. The reproductive investment of the common goby increased, possibly as a consequence of those environmental changes.

Reproductive strategies ofGammarus lacustris(Crustacea: Amphipoda) along an elevation gradient

Abstract1. The number of eggs, their size, mass and development time, and the starvation time of newly hatched young, was examined in four populations ofGammarus lacustrisalong an elevation gradient from prairie to alpine lakes (730 m to > 2300 m above sea level). Water temperature and ice‐free season decreased with increasing altitude.2. Females in the alpine lake produced fewer but larger and heavier eggs than females in the prairie lake. Eggs produced by females in montane and subalpine lakes were intermediate in size, mass and number. Within populations, egg size was not related to the number of eggs or female size.3. The development time of eggs declined with an increase in incubation temperature. At all incubation temperatures, large eggs had a longer incubation time than small eggs. All eggs incubated at 4 °C failed to produce young. Young from large eggs were larger in size than young from small eggs.4. The starvation time of newly hatched young increased with decreasing temperature. However, slopes of regressions relating starvation time to temperature differed among populations. At 4 °C young from large eggs survived longer than young from small eggs.5. The high phenotypic plasticity in reproductive traits contributes to the success ofG. lacustrisin a wide range of aquatic habitats. It is predicted that in response to climate‐induced warming, populations in currently cold montane and alpine lakes would shift their reproduction to produce more eggs of smaller size. However, the accurate prediction of the fate of populations between ecoregions will require knowledge of the extent to which these traits are under genetic control.

GENETIC INFLUENCES ON EXPERIMENTAL POPULATION DYNAMICS OF THE LEAST KILLIFISH

When natural populations differ in density or in the dynamic fluctuations of population size, some of those differences may result from their different ecological conditions, and some may originate from genetically based differences in life history expression. Natural populations of the live-bearing poeciliid fish, Heterandria formosa, vary considerably in their population dynamics, with densities that differ between populations by as much as sevenfold. This system offers an excellent opportunity to explore the potential role of genetically based differences in life history expression in creating different dynamic patterns in a common environment. We created five different genetic stocks of H. formosa by carrying out a series of crosses using fish from two North Florida populations (the Wacissa River and Trout Pond) and used them to initiate replicate experimental populations in artificial ponds. The five stocks consisted of two “controls,” which were pure Wacissa River and Trout Pond stocks, and three types of hybrid stocks. The hybrid stocks differed in a regular way in the proportion of genes from one population or the other. The crossing scheme was designed so that each hybrid stock would have the same proportion of heterozygous (or “heterodemic”) loci but would differ in the proportion and/or identity of homozygous (or “homodemic”) loci from the Wacissa River and Trout Pond populations. These populations were chosen because a previous study had found that population densities in the Wacissa River greatly exceeded those of Trout Pond and exhibited a higher range of population fluctuation during the breeding season. We addressed four questions in this experiment: (1) Are there genetically based differences in life history traits of fish from the two populations? (2) If so, do differences in life history expression produce differences in population dynamics in a common environment? (3) Which traits have the greatest influence on population dynamics? (4) How do changes in density affect the phenotypes of individual traits that govern the rates of birth and death in a population? We followed experimental populations of the five genetic stocks from their initiation at low density through 4–6 generations of population growth and decline. The mean offspring size differed among stocks by as much as 50%. At low densities, offspring size exhibited a trade-off with brood size: Trout Pond alleles were associated with more, smaller offspring. At higher densities, offspring sizes were similar among stocks, and the trade-off with offspring number was not evident. Stocks differed in realized population growth rate by as much as 70%; the rank order differences among stocks with respect to population growth rate appeared to match the genetic relatedness among stocks based on the expected percentage of Trout Pond alleles. Differences in population growth rate appeared to be due to differences in brood size among stocks at low density. Stocks did not differ in the equilibrium population size, which indicated the absence of a trade-off between population growth rate and carrying capacity in this environment. Adult survival and recruitment of juveniles into the adult population both declined linearly with increasing density; and stocks did not generally differ in those rates after the effects of density had been taken into account. The stocks differed in their response to the depressant effects of density on life history trait expression. The offspring size of the pure Wacissa River stock was much more sensitive to density than was the offspring size of the pure Trout Pond stock. However, the brood sizes of the Wacissa River stock were reduced much less than those of the Trout Pond stock when exposed to the same high density. These results suggest that life history distinctions among populations, both in the mean values and plasticity of traits, play a role in creating different dynamics. We discuss the ways in which phenotypic plasticity in reproductive traits potentially acts as a mechanism to stabilize population dynamics in this species.

Phenotypic plasticity in reproductive traits: importance in the life history of Helix aspersa (Mollusca: Helicidae) in a recently colonized habitat

Abstract Reproductive traits of the land snail Helix aspersa Muller were investigated under artificial conditions from two samples, one collected from a population exposed to unpredictable human pressures in its natural environment, i.e. a recently created polders area with intensive agriculture, and the other from a snail farm in which animals were reared under constant conditions defined as «optimal» for growth and reproduction. Results were compared with data collected from natural populations of the same region (Brittany) and from habitats spanning the environmental heterogeneity of the range of the species. A large part of the variation among populations could be explained by different phenotypic covariances between shell size, clutch size and egg size, but not by the number of clutches per snail. Thus, the higher egg production of snails from the polders was related to (i) a strong correlation between clutch size and shell size, shell size being in the upper limit of the overall range for the region concerned; (ii) an uncommonly low egg weight in comparison with the «norm» of Helix aspersa , this trait seeming to be involved in a trade-off with clutch size. Second clutches were smaller than the first ones, but their eggs were significantly heavier. This difference may be linked to a size-dependent mortality of juveniles during winter which arises in all populations in which hibernation occurs as an adaptation to low temperatures. In addition to the selective regime usually involved for populations of helicid snails from Western Europe, several unpredictable mortality factors occurred in the polders area: herbicide and pesticide treatments (lethal for young snails), human predation (lethal for adults) and burning (lethal for all snails). Life-history patterns of Helix aspersa are discussed in relation to its ability to successfully colonize a large range of habitats modified by humans, to such an extent that it can become a pest.

Phenotypic plasticity in reproductive traits: importance in the life history of Helix aspersa (Mollusca: Helicidae) in a recently colonized habitat

Reproductive traits of the land snail Helix aspersa Müller were investigated under artificial conditions from two samples, one collected from a population exposed to unpredictable human pressures in its natural environment, i.e. a recently created polders area with intensive agriculture, and the other from a snail farm in which animals were reared under constant conditions defined as «optimal» for growth and reproduction. Results were compared with data collected from natural populations of the same region (Brittany) and from habitats spanning the environmental heterogeneity of the range of the species. A large part of the variation among populations could be explained by different phenotypic covariances between shell size, clutch size and egg size, but not by the number of clutches per snail. Thus, the higher egg production of snails from the polders was related to (i) a strong correlation between clutch size and shell size, shell size being in the upper limit of the overall range for the region concerned; (ii) an uncommonly low egg weight in comparison with the «norm» ofHelix aspersa , this trait seeming to be involved in a trade-off with clutch size. Second clutches were smaller than the first ones, but their eggs were significantly heavier. This difference may be linked to a size-dependent mortality of juveniles during winter which arises in all populations in which hibernation occurs as an adaptation to low temperatures. In addition to the selective regime usually involved for populations of helicid snails from Western Europe, several unpredictable mortality factors occurred in the polders area: herbicide and pesticide treatments (lethal for young snails), human predation (lethal for adults) and burning (lethal for all snails). Life-history patterns of Helix aspersa are discussed in relation to its ability to successfully colonize a large range of habitats modified by humans, to such an extent that it can become a pest.

Trade-offs between Reproductive Traits and the Influence of Food Intake during Pregnancy in the Garter Snake, Thamnophis elegans

Trade-offs between Reproductive Traits and the Influence of Food Intake during Pregnancy in the Garter Snake, Thamnophis elegans

Control of Phenotypic Plasticity Via Regulatory Genes

Control of Phenotypic Plasticity Via Regulatory Genes

Environmental effects on variation and covariation in reproductive traits of Western Bluebirds

Environmental conditions can influence the expression and correlations of phenotypic traits. I studied phenotypic plasticity in reproductive traits of Western Bluebirds breeding in northern Arizona. Data collected over 4 years on two contrasting habitats identified significant spatial and temporal variation in bluebird reproduction. Clutch size was similar over different environmental conditions whereas timing of clutch initiation, percent fledging success, and frequency of second nest attempts were flexible. Correlations between traits varied widely-often changing sign-among samples from different years or habitats. Correlations of traits with reproductive success were also dependent on environmental conditions. Variation in traits reflected behavioral responses by nesting adults to differences in time for breeding and feeding conditions. Density of trees differed between habitats and had opposing effects on these environmental variables; breeding seasons were generally longer, but feeding rates to nestlings were lower on the more open habitat. Late Spring snows delayed reproduction and increased the importance of limited time for breeding; feeding conditions were more influential following a dry Spring. This and other studies illustrate that data on phenotypic plasticity are important when evaluating the ecological and evolutionary forces underlying life histories.

Phenotypic Plasticity in Reproductive Traits: Evidence from a Viviparous Snake

A number of recent studies have indicated that life history characteristics (e.g., number of offspring, offspring size, age at sexual maturity) are strongly affected by proximate environmental factors such as prey availability. Evaluating this phenotypic plasticity will be crucial to a complete understanding of the evolution of life history traits, because the occurrence of such variability casts doubt on the common assumption that the values of life history characteristics expressed in nature are the outcome of long-term natural selection. In this study, we manipulated the diets of a captive-bred colony of the viviparous snake Thamnophis marcianus to determine to what degree the reproductive characteristics of this species were determined by food intake. We found that both number of offspring and clutch mass were significantly affected by prey availability, but that relative clutch mass and offspring size were fixed relative to diet. Our data suggest that like other organisms, T. marcianus shows a gradient in phenotypic plasticity, with some traits more canalized than others. Therefore, intraspecific comparisons of life history characteristics should not be made without information on which traits are subject to phenotypic plasticity.