Correlated evolution of life-history with size at maturity in Daphnia pulicaria: patterns within and between populations

Explaining the repeated evolution of similar sets of traits under similar environmental conditions is an important issue in evolutionary biology. The extreme alternative classes of explanations for correlated suites of traits are optimal adaptation and genetic constraint resulting from pleiotropy. Adaptive explanations presume that individual traits are free to evolve to their local optima and that convergent evolution represents particularly adaptive combinations of traits. Alternatively, if pleiotropy is strong and difficult to break, strong selection on one or a few particularly important characters would be expected to result in consistent correlated evolution of associated traits. If pleiotropy is common, we predict that the pattern of divergence among populations will consistently reflect the within-population genetic architecture. To test the idea that the multivariate life-history phenotype is largely a byproduct of strong selection on body size, we imposed divergent artificial selection on size at maturity upon two populations of the cladoceran Daphnia pulicaria, chosen on the basis of their extreme divergence in body size. Overall, the trajectory of divergence between the two natural populations did not differ from that predicted by the genetic architecture within each population. However, the pattern of correlated responses suggested the presence of strong pleiotropic constraints only for adult body size and not for other life-history traits. One trait, offspring size, appears to have evolved in a way different from that expected from the within-population genetic architecture and may be under stabilizing selection.     

Geographic variation in the Laysan Finch (Telespyza cantans)

Summary Significant differences in bill shape exist between the endemic Laysan population and introduced populations of the Laysan Finch (Drepanidinae:Telespyza cantans) at Pearl and Hermes Reef. Furthermore, there are significant differences in bill shape between two of four finch populations on the islands of Pearl and Hermes Reef. The variation in finch bill shape is paralleled by geographic variation in the large, hard mericarps ofTribulus cistoides, an important food item at Pearl and Hermes Reef. There are three possible explanations for the observed variation. Environmental influence may be a non-evolutionary cause of the variation, or genetic drift and natural selection may have caused the differences in morphology. Preliminary results suggest that both genetic drift and natural selection have been acting on the populations. Continuing studies, including investigation of genetic variation and cross-fostering experiments to determine heritability of morphological traits and effects of environment on morphological traits, are planned to test the various hypotheses.     

The evolution of tolerance to damage in Gentianella campestris: natural selection and the quantitative genetics of tolerance

In the framework of phenotypic plasticity, tolerance to browsing can be operationally defined as a norm of reaction comparing plant performance in undamaged and damaged conditions. Genetic variation in tolerance is then indicated by heterogeneity in the slopes of norms of reaction from a population. We investigated field gentian (Gentianella campestris) tolerance to damage in the framework of phenotypic plasticity using a sample of maternal lines from natural populations grown under common garden conditions and randomly split into either a control or an artificial clipping treatment. We found a diversity of tolerance norms of reaction at both the population and family level: the impacts of clipping ranged from poor tolerance (negative slope) to overcompensation (positive slope). We detected heterogeneity in tolerance norms of reaction in four populations. Similarly, we found a variety of plastic architectural responses to clipping and genetic variation in these responses in several populations. Overall, we found that the most tolerant populations were late flowering and also exhibit the greatest plastic increases in node (meristem) production in response to damage. We studied damage-imposed natural selection on plasticity in plant architecture in 10 of the sampled populations. In general, there was strong positive direct selection on final number of nodes for both control and clipped plants. However, the total selection on nodes (direct + indirect selection) within each treatment category depended heavily on the frequency of damage and cross-treatment genetic correlations in node production. In some cases, strong correlated responses to selection across the damage treatment led to total selection against nodes in the more rare environment. This could ultimately lead to the evolution of maladaptive phenotypes in one or both of the treatment categories. These results suggest that tolerance and a variety of architectural responses to damage may evolve by both direct and indirect responses to natural selection. While the present study demonstrates the potential importance of cross-treatment genetic correlations in directing the evolution of tolerance traits, such as branch or node production, we did not find any strong evidence of genetic trade-offs in candidate tolerance traits between undamaged and damaged conditions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Rapid genome‐wide evolution in Brassica rapa populations following drought revealed by sequencing of ancestral and descendant gene pools

There is increasing evidence that evolution can occur rapidly in response to selection. Recent advances in sequencing suggest the possibility of documenting genetic changes as they occur in populations, thus uncovering the genetic basis of evolution, particularly if samples are available from both before and after selection. Here, we had a unique opportunity to directly assess genetic changes in natural populations following an evolutionary response to a fluctuation in climate. We analysed genome‐wide differences between ancestors and descendants of natural populations of Brassica rapa plants from two locations that rapidly evolved changes in multiple phenotypic traits, including flowering time, following a multiyear late‐season drought in California. These ancestor‐descendant comparisons revealed evolutionary shifts in allele frequencies in many genes. Some genes showing evolutionary shifts have functions related to drought stress and flowering time, consistent with an adaptive response to selection. Loci differentiated between ancestors and descendants (F_ST outliers) were generally different from those showing signatures of selection based on site frequency spectrum analysis (Tajima's D), indicating that the loci that evolved in response to the recent drought and those under historical selection were generally distinct. Very few genes showed similar evolutionary responses between two geographically distinct populations, suggesting independent genetic trajectories of evolution yielding parallel phenotypic changes. The results show that selection can result in rapid genome‐wide evolutionary shifts in allele frequencies in natural populations, and highlight the usefulness of combining resurrection experiments in natural populations with genomics for studying the genetic basis of adaptive evolution.     

Evolutionary potential of a widespread clonal grass under changing climate

Adaptive responses are probably the most effective long‐term responses of populations to climate change, but they require sufficient evolutionary potential upon which selection can act. This requires high genetic variance for the traits under selection and low antagonizing genetic covariances between the different traits. Evolutionary potential estimates are still scarce for long‐lived, clonal plants, although these species are predicted to dominate the landscape with climate change. We studied the evolutionary potential of a perennial grass, Festuca rubra, in western Norway, in two controlled environments corresponding to extreme environments in natural populations: cold–dry and warm–wet, the latter being consistent with the climatic predictions for the country. We estimated genetic variances, covariances, selection gradients and response to selection for a wide range of growth, resource acquisition and physiological traits, and compared their estimates between the environments. We showed that the evolutionary potential of F. rubra is high in both environments, and genetic covariances define one main direction along which selection can act with relatively few constraints to selection. The observed response to selection at present is not sufficient to produce genotypes adapted to the predicted climate change under a simple, space for time substitution model. However, the current populations contain genotypes which are pre‐adapted to the new climate, especially for growth and resource acquisition traits. Overall, these results suggest that the present populations of the long‐lived clonal plant may have sufficient evolutionary potential to withstand long‐term climate changes through adaptive responses.     

Quantitative genetics of yield breeding forPopulus short rotation culture. III. Efficiency of indirect selection on tree geometry

Quantitative analysis of genetic covariances was used to identify the critical morphological components of wood productivity and to evaluate the efficiency of indirect selection for these components at the four levels of biological organization, (1) leaf, (2) branch, (3) main stem, and (4) whole-tree, in 4-yearPopulus deltoides ×P. simonii andP. deltoides ×P. nigra F₁ progeny. A total of 44 morphometric traits measured at the four organizational levels showed varying genetic associations with productivity, variations being dependent on traits, developmental processes (current terminal, sylleptics, and proleptics), and hybridization combinations. Most of the leaf and branch traits on the current terminal and/or sylleptic branches had higher genetic correlations with stem-wood volume than those on proleptics, which resulted in larger indirect selection responses in volume, especially in DxS progeny. Indirect clonal selection on leaf size and area, branching capacity, and branch angle at age 4 years was expected to generate 10–35% more genetic gain per year in 6-year volume than direct selection on 6-year volume in the DxS progeny. The efficiency of indirect selection on the numbers of different order branches and bifurcation ratio was greater than 1.0 relative to that for direct selection for stemwood volume in the D × N progeny. Under the pressure of artificial selection for superior volume production, with the proportion selected=15%, the two F₁ progeny populations exhibited distinct evolutionary divergence in tree geometry. The high-yielding D × S clones displayed a decurrent-like crown with strong apical dominance, whereas the crown ideotype for the high-yielding D × N clones was found to be excurrent-like and surrounded by dense foliage and branches.     

A multivariate test of evolutionary constraints for thermal tolerance in Drosophila melanogaster

Exposure to extreme temperatures is increasingly likely to impose strong selection on many organisms in their natural environments. The ability of organisms to adapt to such selective pressures will be determined by patterns of genetic variation and covariation. Despite increasing interest in thermal adaptation, few studies have examined the extent to which the genetic covariance between traits might constrain thermal responses. Furthermore, it remains unknown whether sex‐specific genetic architectures will constrain responses to climatic selection. We used a paternal half‐sibling breeding design to examine whether sex‐specific genetic architectures and genetic covariances between traits might constrain evolutionary responses to warming climates in a population of Drosophila melanogaster. Our results suggest that the sexes share a common genetic underpinning for heat tolerance as indicated by a strong positive inter‐sexual genetic correlation. Further, we found no evidence in either of the sexes that genetic trade‐offs between heat tolerance and fitness will constrain responses to thermal selection. Our results suggest that neither trade‐offs, nor sex‐specific genetics, will significantly constrain an evolutionary response to climatic warming, at least in this population of D. melanogaster.     

Invasive Mahonia plants outgrow their native relatives

Invasive populations often grow more vigorously than conspecific populations in the native range. This has frequently been attributed to evolutionary changes resulting either from founder effects, or from natural selection owing to enemy release. Another mechanism contributing to evolutionary change has largely been neglected in the past: Many invasive plant species do actually descend from cultivated plants and were therefore subject to breeding, including hybridization and artificial selection. In a common garden experiment, we compared invasive Central European populations of the ornamental shrub, Mahonia, with native populations of its putative parental species, Mahonia aquifolium and M. repens, from North America. We hypothesized that plants of invasive populations show increased growth and retained high levels of heritable variation in phenotypic traits. Indeed, invasive Mahonia plants grew larger in terms of stem length, number of leaves and above-ground biomass than either of the two native species, which did not differ significantly from each other. Since there are no hints on release of invasive Mahonia populations from natural enemies, it is likely that hybridization and subsequent selection by breeders have lead to an evolutionary increase of plant vigour in the introduced range. Further on, heritable variation was not consistently reduced in invasive populations compared with populations of the two native species. We suggest that interspecific hybridization among the Mahonia species has counteracted the harmful effects of genetic bottlenecks often associated with species introductions. Based on this case study, we conclude that, more attention has to be paid on the role of plant breeding when assessing the mechanisms behind successful plant invasions in future.     

Low levels of quantitative and molecular genetic differentiation among natural populations of Medicago ciliaris Kroch. (Fabaceae) of different Tunisian eco-geographical origin

In this paper, we analyze the genetic variability in four Tunisian natural populations of Medicago ciliaris using 19 quantitative traits and six polymorphic microsatellite loci. We investigated the amplification transferability of 30 microsatellites developed in the model legume M. truncatula to M. ciliaris. Results revealed that about 56.66% of analyzed markers are valuable genetic markers for M. ciliaris. The most genetic diversity at quantitative traits and microsatellite loci was found to occur within populations (>80%). Low differentiations among populations at quantitative traits Q _ST  = 0.146 and molecular markers F _ST  = 0.18 were found. The majority of measured traits exhibited no significant difference in the level of Q _ST and F _ST . Furthermore, significant correlations established between these traits and eco-geographical factors suggested that natural selection should be invoked to explain the level of phenotypic divergence among populations rather than drift. There was no significant correlation between population differentiation at quantitative traits and molecular markers. Significant spatial genetic structure consistent with models of isolation by distance was detected within all studied populations. The site-of-origin environmental factors explain about 9.07% of total phenotypic genetic variation among populations. The eco-geographical factors that influence more the variation of measured traits among populations are the soil texture and altitude. Nevertheless, there were no consistent pattern of associations between gene diversity (He) and environmental factors.     

Evolutionary potential of morphological traits across different life‐history stages

Despite accumulating examples of selection acting on heritable traits in the wild, predicted evolutionary responses are often different from observed phenotypic trends. Various explanations have been suggested for these mismatches. These include within‐individual changes across lifespan that can create important variation in genetic architecture of traits and selection acting on them, but also potential problems with the methodological approach used to predict evolutionary responses of traits. Here, we used an 8‐year data set on tree swallow (Tachycineta bicolor) to first assess the effects of differences among three nestling life‐history stages on the genetic (co)variances of two morphological traits (body mass and primary feather length) and the selection acting on them over three generations. We then estimated the evolutionary potential of these traits by predicting their evolutionary responses using the breeder's equation and the secondary theorem of selection approaches. Our results showed variation in strength and direction of selection and slight changes in trait variance across ages. Predicted evolutionary responses differed importantly between both approaches for half of the trait–age combinations we studied, suggesting the presence of environmentally induced correlations between focal traits and fitness possibly biasing breeder's equation predictions. Our results emphasize that predictions of evolutionary potential for morphological traits are likely to be highly variable, both in strength and direction, depending on the life stage and method used, thus mitigating our capacity to predict adaptation and persistence of wild populations.     

A population genetic evaluation of ecological restoration with the case study on <Emphasis Type="Italic">Cyclobalanopsis myrsinaefolia</Emphasis> (Fagaceae)

The ultimate goal of ecological restoration is to create a self-sustaining ecosystem that is resilient to perturbation without further assistance. Genetic variation is a prerequisite for evolutionary response to environmental changes. However, few studies have evaluated the genetic structure of restored populations of dominant plants. In this study, we compared genetic variation of the restored populations with the natural ones in Cyclobalanopsis myrsinaefolia, a dominant species of evergreen broadleaved forest. Using eight polymorphic microsatellite loci, we analyzed samples collected from restored populations and the donor population as well as two other natural populations. We compared the genetic diversity of restored and natural populations. Differences in genetic composition were evaluated using measurements of genetic differentiation and assignment tests. The mean number of alleles per locus was 4.65. Three parameters (A, A _R, and expected heterozygosity) of genetic variation were found to be lower, but not significantly, in the restored populations than they were in the natural populations, indicating a founder effect during the restoration. Significant but low F _ST (0.061) was observed over all loci, indicating high gene flow among populations, as expected from its wind-pollination. Differentiation between the two restored populations was smallest. However, differences between the donor population and the restored populations were higher than those between other natural populations and the restored populations. Only 13.5% and 25.7% individuals in the two restored populations were assigned to the donor population, but 54.1 and 40% were assigned to another natural population. The genetic variation of the donor population was lowest, and geographic distances from the restoration sites to the donor site were much higher than the other natural populations, indicating that the present donor likely was not the best donor for these ecological restoration efforts. However, no deleterious consequences might be observed in restored populations due to high observed heterozygosity and high gene flow. This study demonstrates that during the restoration process, genetic structures of the restored populations may be biased from the donor population. The results also highlight population genetic knowledge, especially of gene flow-limited species, in ecological restoration.     

Strong signature of selection in seeder populations but not in resprouters of the fynbos heath Erica coccinea (Ericaceae)

A higher frequency of natural selection is expected in populations of organisms with shorter generation times. In fire‐prone ecosystems, populations of seeder plants behave as functionally semelparous populations, with short generation times compared to populations of resprouter plants, which are truly iteroparous. Therefore, a stronger signature of natural selection should be detected in seeder populations, favoured by their shorter generation times and higher rates of population turnover. Here we test this idea in Erica coccinea from the Cape Floristic Region, which is dimorphic for post‐fire regeneration mode. We measured three floral traits supposedly subject to natural selection in seeder and resprouter populations. We then compared phenotypic trait variation with neutral genetic variation in each group of populations using P_ST–F_ST comparisons to detect signatures of natural selection in seeders and resprouters. We found a strong signature of selection in seeder populations, but not in resprouters. Furthermore, anthers of seeders were more exserted (and larger) than those of resprouters. These differences were maintained at sites where seeders and resprouters co‐occurred, suggesting that phenotypic plasticity or adaptation to different growth environments are unlikely explanations for trait variation. These results provide empirical support for the hypothesis that the genetic signature of natural selection is certainly more intense in seeder than in resprouter populations, favoured by their comparatively faster generation turnovers. Increased frequency of natural selection would increase differentiation among populations, thus promoting speciation in pyrophytic seeder lineages of the Cape flora.     

Evolutionary experiments on mate recognition in the Drosophila serrata species complex

It is becoming increasingly apparent that at least some aspects of the evolution of mate recognition may be amenable to manipulation in evolutionary experiments. Quantitative genetic analyses that focus on the genetic consequences of evolutionary processes that result in mate recognition evolution may eventually provide an understanding of the genetic basis of the process of speciation. We review a series of experiments that have attempted to determine the genetic basis of the response to natural and sexual selection on mate recognition in the Drosophila serrata species complex. The genetic basis of mate recognition has been investigated at three levels: (1) between the species of D. serrata and D. birchii using interspecific hybrids, (2) between populations of D. serrata that are sympatric and allopatric with respect to D. birchii, and (3) within populations of D. serrata. These experiments suggest that it may be possible to use evolutionary experiments to observe important events such as the reinforcement of mate recognition, or the generation of the genetic associations that are central to many sexual selection models.     

Contrasting Levels of Variation in Neutral and Quantitative Genetic Loci on Island Populations of Moor Frogs (<Emphasis Type="Italic">Rana arvalis</Emphasis>)

Reduced levels of genetic variability and a prominent differentiation in both neutral marker genes and phenotypic traits are typical for many island populations as compared to their mainland conspecifics. However, whether genetic diversity in neutral marker genes reflects genetic variability in quantitative traits, and thus, their evolutionary potential, remains typically unclear. Moreover, the phenotypic differentiation on islands could be attributable to phenotypic plasticity, selection or drift; something which seldom has been tested. Using eight polymorphic microsatellite loci and quantitative genetic breeding experiments we conducted a detailed comparison on genetic variability and differentiation between Nordic islands (viz. Gotland, Öland and Læsø) and neighbouring mainland populations of moor frogs (Rana arvalis). As expected, the neutral variation was generally lower in island than in mainland populations. But as opposed to this, higher levels of additive genetic variation (V _A) in body size and tibia length were found on the island of Gotland as compared to the mainland population. When comparing the differentiation seen in neutral marker genes (F _ST) with the differentiation in genes coding quantitative traits (Q _ST) two different evolutionary scenarios were found: while selection might explain a smaller size of moor frogs on Gotland, the differentiation seen in tibia length could be explained by genetic drift. These results highlight the limited utility of microsatellite loci alone in inferring the causes behind an observed phenotypic differentiation, or in predicting the amount of genetic variation in ecologically important quantitative traits.     

Evolutionary history of an MHC gene in two leporid species: characterisation of <Emphasis Type="Italic">Mhc-DQA</Emphasis> in the European brown hare and comparison with the European rabbit

We surveyed the genetic diversity of the expressed major histocompatibility complex class II DQA locus in natural populations of European brown hares, Lepus europaeus, from Austria and Belgium (267 individuals in total). Based on cDNA sequences, we designed hare-specific primers to amplify the highly variable second exon of the DQA gene. Using cloning–sequencing methodology and capillary electrophoresis single-strand conformation polymorphism, we found ten alleles of the DQA exon 2 locus across these two European regions, of which eight are described for the first time. To search for signals of selection and recombination in the evolution of the DQA gene within the leporids, we augmented our sample with orthologous DQA alleles from the European rabbit, Oryctolagus cuniculus, in order to carry out a species level, species pairwise comparison. We found evidence of recombination in the history of the DQA sequences in leporids with some recombinant alleles bridging the species divide. In both species, selection on peptide binding site codons can be detected, though stronger for the rabbit. This result suggests that there may be a differential selection pressure in the deeper evolutionary history of these two species due to differences in several demographic and ecological traits likely subjecting them to differential selection by parasites. Finally, evolutionary relationships show a widespread and statistically significant intermingling of alleles from the two species. The many macroparasites shared between hares and rabbits may explain this pattern of trans-species polymorphism. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. The nucleotide sequence data reported in this paper have been submitted to Genbank and have been assigned the accession numbers FJ225335–FJ225346.     

Evolutionary consequences of simulated global change: genetic adaptation or adaptive phenotypic plasticity

During the next century, natural and agricultural systems might need to adjust to a rapid increase in atmospheric CO₂ concentration and global temperature. Evolution of genotypes adapted to this global change could play a central role in plants' response. The main purpose of this study was to determine the relative importance of phenotypic and genotypic responses of plants to global change. To do so, we selected two populations of the short-lived Brassica juncea, one under ambient conditions and another one under conditions simulating global change. After seven generations of selection, differences between the two populations were examined using a reciprocal transplant garden. We monitored 14 different traits and found evidence for genetic adaptation only once, for vegetative biomass early in the growth cycle. Of the 14 traits, 11 responded plastically to the environment, but only one of these plastic changes had a possible adaptive value. Overall, the long-term evolutionary consequences of global change will depend on the response of fitness-related traits. None of the five reproductive traits measured showed any evolutionary responses. The main conclusion of our study is that Brassica juncea was apparently unable to respond evolutionarily to simulated global change either by genetic adaptation or by adaptive phenotypic plasticity. The limit to selection was apparently due to inbreeding depression induced by the harsh conditions of the predicted environment.     

QUANTIFYING EVOLUTIONARY POTENTIAL OF MARINE FISH LARVAE: HERITABILITY,SELECTION, AND EVOLUTIONARY CONSTRAINTS

For many marine fish, intense larval mortality may provide considerable opportunity for selection, yet much less is known about the evolutionary potential of larval traits. We combined field demographic studies and manipulative experiments to estimate quantitative genetic parameters for both larval size and swimming performance for a natural population of a common coral‐reef fish, the bicolor damselfish (Stegastes partitus). We also examined selection on larval size by synthesizing information from published estimates of selective mortality. We introduce a method that uses the Lande–Arnold framework for examining selection on quantitative traits to empirically reconstruct adaptive landscapes. This method allows the relationship between phenotypic value and fitness components to be described across a broad range of trait values. Our results suggested that despite strong viability selection for large larvae and moderate heritability (h²= 0.29), evolutionary responses of larvae would likely be balanced by reproductive selection favoring mothers that produce more, smaller offspring. Although long‐term evolutionary responses of larval traits may be constrained by size‐number trade‐offs, our results suggest that phenotypic variation in larval size may be an ecologically important source of variability in population dynamics through effects on larval survival and recruitment to benthic populations.     

Natural selection on ecophysiological traits of a fern species in a temperate rainforest

Unlike other species of the genus Blechnum, the fern Blechnum chilense occurs in a wide range of habitats in Chilean temperate rainforest, from shaded forest understories to abandoned clearings and large gaps. We asked if contrasting light environments can exert differential selection on ecophysiological traits of B. chilense. We measured phenotypic selection on functional traits related to carbon gain: photosynthetic capacity (A _max), dark respiration rate (R _d), water use efficiency (WUE), leaf size and leaf thickness in populations growing in gaps and understorey environments. We assessed survival until reproductive stage and fecundity (sporangia production) as fitness components. In order to determine the potential evolutionary response of traits under selection, we estimated the genetic variation of these traits from clonally propagated individuals in common garden experiments. In gaps, survival of B. chilense was positively correlated with WUE and negatively correlated with leaf size. In contrast, survival in shaded understories was positively correlated with leaf size. We found positive directional fecundity selection on WUE in gaps population. In understories, ferns of lower R _d and greater leaf size showed greater fecundity. Thus, whereas control of water loss was optimized in gaps, light capture and net carbon balance were optimized in shaded understories. We found a significant genetic component of variation in WUE, R _d and leaf size. This study shows the potential for evolutionary responses to heterogeneous light environments in functional traits of B. chilense, a unique fern species able to occupy a broad successional niche in Chilean temperate rainforest.     

Temporal genetic stability in natural populations of the waterflea Daphnia magna in response to strong selection pressure

Studies monitoring changes in genetic diversity and composition through time allow a unique understanding of evolutionary dynamics and persistence of natural populations. However, such studies are often limited to species with short generation times that can be propagated in the laboratory or few exceptional cases in the wild. Species that produce dormant stages provide powerful models for the reconstruction of evolutionary dynamics in the natural environment. A remaining open question is to what extent dormant egg banks are an unbiased representation of populations and hence of the species’ evolutionary potential, especially in the presence of strong environmental selection. We address this key question using the water flea Daphnia magna, which produces dormant stages that accumulate in biological archives over time. We assess temporal genetic stability in three biological archives, previously used in resurrection ecology studies showing adaptive evolutionary responses to rapid environmental change. We show that neutral genetic diversity does not decline with the age of the population and it is maintained in the presence of strong selection. In addition, by comparing temporal genetic stability in hatched and unhatched populations from the same biological archive, we show that dormant egg banks can be consulted to obtain a reliable measure of genetic diversity over time, at least in the multidecadal time frame studied here. The stability of neutral genetic diversity through time is likely mediated by the buffering effect of the resting egg bank.