Genetics of host plant use and life history in the comma butterfly across Europe: varying modes of inheritance as a potential reproductive barrier

Comma butterflies (Nymphalidae: Polygonia c-album L.) from one Belgian site and three Spanish sites were crossed with butterflies from a Swedish population in order to investigate inheritance of female host plant choice, egg mass and larval growth rate. We found three different modes of inheritance for the three investigated traits. In line with earlier results from crosses between Swedish and English populations, the results regarding female oviposition preference (choice between Urtica dioica and Salix caprea) showed X-linked inheritance to be of importance for the variation between Sweden and the other sites. Egg mass and growth rate did not show any sex-linked inheritance. Egg mass differences between populations seem to be controlled mainly by additive autosomal genes, as hybrids showed intermediate values. The growth rates of both hybrid types following reciprocal crossings were similar to each other but consistently higher than for the two source populations, suggesting a nonadditive mode of inheritance which is not sex-linked. The different modes of inheritance for host plant preference vs. important life history traits are likely to result in hybrids with unfit combinations of traits. This type of potential reproductive barrier based on multiple ecologically important traits deserves more attention, as it should be a common situation for instance in the early stages of population divergence in host plant usage, facilitating ecological speciation.     

Climatic adaptation in an isolated and genetically impoverished amphibian population

The capacity of populations to respond adaptively to environmental change is essential for their persistence. Isolated populations often harbour reduced genetic variation, which is predicted to decrease adaptive potential, and can be detrimental under the current scenarios of global change. In this study, we examined climatic adaptation in larval life history traits in the pool frog Rana lessonae along a latitudinal gradient across the northern distribution area of the species, paying special attention to the isolated and genetically impoverished fringe populations in central Sweden. Larvae from eight populations within three geographic areas (Poland, Latvia and Sweden) were reared under three temperatures (19, 22 and 26°C) in a common garden laboratory experiment. We found clear evidence for latitudinal adaptation in R. lessonae populations, larvae from higher latitudes growing and developing faster than low‐latitude ones. Larvae from the Swedish populations were able to compensate for the effects of cooler temperatures and a shorter growth season with genetically higher growth and development rates (i.e. countergradient variation) in the two higher temperature treatments, but there was no difference among the populations at the lowest temperature treatment, which is likely to be close to the temperature limiting growth in R. lessonae. Our results demonstrate that isolated and genetically impoverished populations can be locally adapted, and identify the Swedish fringe populations as a significant conservation unit adapted to the northern environmental conditions.     

Differentiation in developmental rate across geographic regions: a photoperiod driven latitude compensating mechanism?

Genetic differentiation and phenotypic plasticity in growth rates along latitudinal gradients may benefit our understanding of latitudinal compensating mechanisms in life history patterns. Here we explore latitudinal compensatory growth mechanisms with respect to photoperiod in northern and southern populations of two damselfly species, Coenagrion puella and C. pulchellum. In addition we compared size of field‐collected adults from southern and northern populations. Eggs from females in copulating tandems were collected at two or three localities for each species in each geographic region. Eggs were transported to the laboratory and the experiment started when the eggs hatched. The role of photoperiod on the expression of larval growth rate was evaluated under controlled laboratory conditions. Both species had lower growth rate when reared in the northern photoperiod, which is counter to expectations if species use photoperiodic cues to trigger compensatory growth. Instead, both species displayed countergradient variation in growth rates, which probably enable northern populations to compensate for the shorter growth season in the north. The smaller size of field‐collected adults from northern populations also supports the view that these species compensate for the shorter growth season by investing in growth and development but accomplish this at the expense of decreased final size.     

Leaf-level phenotypic variability and plasticity of invasive Rhododendron ponticum and non-invasive Ilex aquifolium co-occurring at two contrasting European sites

To understand the role of leaf-level plasticity and variability in species invasiveness, foliar characteristics were studied in relation to seasonal average integrated quantum flux density (Qint) in the understorey evergreen species Rhododendron ponticum and Ilex aquifolium at two sites. A native relict population of R. ponticum was sampled in southern Spain (Mediterranean climate), while an invasive alien population was investigated in Belgium (temperate maritime climate). Ilex aquifolium was native at both sites. Both species exhibited a significant plastic response to Qint in leaf dry mass per unit area, thickness, photosynthetic potentials, and chlorophyll contents at the two sites. However, R. ponticum exhibited a higher photosynthetic nitrogen use efficiency and larger investment of nitrogen in chlorophyll than I. aquifolium. Since leaf nitrogen (N) contents per unit dry mass were lower in R. ponticum, this species formed a larger foliar area with equal photosynthetic potential and light-harvesting efficiency compared with I. aquifolium. The foliage of R. ponticum was mechanically more resistant with larger density in the Belgian site than in the Spanish site. Mean leaf-level phenotypic plasticity was larger in the Belgian population of R. ponticum than in the Spanish population of this species and the two populations of I. aquifolium. We suggest that large fractional investments of foliar N in photosynthetic function coupled with a relatively large mean, leaf-level phenotypic plasticity may provide the primary explanation for the invasive nature and superior performance of R. ponticum at the Belgian site. With alleviation of water limitations from Mediterranean to temperate maritime climates, the invasiveness of R. ponticum may also be enhanced by the increased foliage mechanical resistance observed in the alien populations.     

Larval aestivation and direct development as alternative strategies in the speckled wood butterfly, Pararge aegeria, in Sweden

ABSTRACT.

• 1 Sweden has two disjunct populations of the speckled wood butterfly, Pararge aegeria L. The southern population has two generations per year but the central Swedish population is univoltine. When rearing larvae from central Sweden under normal photoperiodic conditions but at temperatures slightly above the ambient, 42% of the larvae developed directly and produced a second generation of adults the same summer. The egg—larval development time of the directly developing individuals was about 40 days, whereas that of the individuals developing along the univoltine pathway was about 100 days.
• 2 Larvae of the central Swedish population normally aestivate during part of the summer even though abundant food is available. In the closely related Lasiommata petropolitana F., which is the only Swedish satyrid that overwinters in the pupal stage besides P.aegeria, larvae do not aestivate, indicating that there does not seem to be any obligatory association between pupal hibernation and larval aestivation.
• 3 Development rates of aestivating and directly developing P.aegeria are equal up to the third larval instar. During the third and fourth instars, however, the development rate of aestivating individuals is retarded and females also have an additional fifth instar.
• 4 Since the central Swedish P.aegeria have the capacity to develop directly, and the southern Swedish ones have the capacity to aestivate, the evidence indicates that the outcome of the cost/benefit balance of univoltine versus bivoltine development differs between the two areas.

     

Latitudinal variation in growth among Arctic charr in eastern North America: evidence for countergradient variation?

Biological data from 66 populations of Arctic charr, Salvelinus alpinus, from eastern North America were analysed to test the applicability of the countergradient hypothesis as an explanation of differences in seasonally adjusted growth rates. Samples were obtained along a 37° latitudinal gradient and partitioned among anadromous, normal lacustrine, and dwarf lacustrine Arctic charr morphotypes. Models relating length-at-age or age-specific growth rates to latitude were estimated for each morphotype. Length-at-age declined with latitude for anadromous and lacustrine charr. Age-specific growth rates also varied with latitude, particularly for normal lacustrine charr. Results of analyses provide support for the countergradient hypothesis in growth performance of normal lacustrine morphotypes, where northern populations compensate for the shorter growth season with a greater rate of growth than southern populations. Anadromous charr exhibited equivocal evidence of countergradient variation, while results for dwarf lacustrine Arctic charr populations were inconclusive owing to the limited range of ages, and latitudes for which data were available.     

Latitudinal variation in thermal reaction norms of post‐winter pupal development in two butterflies differing in phenological specialization

Latitudinal clines in thermal reaction norms of development are a common phenomenon in temperate insects. Populations from higher latitudes often develop faster throughout the range of relevant temperatures (i.e countergradient variation) because they must be able to complete their life cycle within a shorter seasonal time window compared to populations at lower latitudes. In the present study, we experimentally demonstrate that two species of butterflies Anthocharis cardamines (L.) and Pieris napi (L.) instead show a cogradient variation in thermal reaction norms of post‐winter pupal development so that lower latitude populations develop faster than higher latitude populations. The two species share host plants but differ in the degree of phenological specialization, as well as in the patterns of voltinism. We suggest that the pattern in A. cardamines, a univoltine phenological specialist feeding exclusively on flowers and seedpods, is the result of selection for matching to the phenological pattern of its local host plants. The other species, P. napi, is a phenological generalist feeding on the leaves of the hosts and it shows a latitudinal cline in voltinism. Because the latitudinal pattern in P. napi was an effect of slow development in a fraction of the pupae from the most northern population, we hypothesize that this population may include both bivoltine and univoltine genotypes. Consequently, although the two species both showed cogradient patterns in thermal reaction norms, it appears likely that this was for different reasons. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 981–991.     

The roles of pre‐ and post‐hatching growth rates in generating a latitudinal cline of body size in the eastern fence lizard (Sceloporus undulatus)

Countergradient variation in norms of reaction can dampen the direct effects of environmental influences on phenotypic traits, allowing phenotypic similarity among populations despite exposure to different environmental conditions. Such norms of reaction may occur at any phase of the life‐history (e.g. growth rates during both embryonic and postembryonic stages may influence geographical variation in adult body size). We collected gravid female lizards (Sceloporus undulatus) from northern (Indiana), central (Mississippi), and southern (Florida) populations, spanning almost the full latitudinal range of the species. Adult females from the southern population were smaller. Intrinsic growth rates of hatchlings were higher for the central population than for the other two populations. This pattern does not parallel the countergradient variation previously found in embryonic developmental rates among these populations. Earlier hatching enhanced survival rates of juveniles to a similar degree among populations, although juvenile survival rates in the field generally increase with latitude in this species. Our data reveal geographical variation in the ways in which intrinsic developmental/growth rates and survival shift during ontogeny, and suggest that latitudinal patterns in adult body size (such as Bergmann's rule) can result from both faster growth, and longer periods of growth. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 202–209.     

Physiological variation along a geographical gradient: is growth rate correlated with routine metabolic rate in Rana temporaria tadpoles?

Shorter season length and lower temperature towards higher latitudes and altitudes often select for intraspecific clines in development and growth rates. However, the physiological mechanisms enabling these clines are not well understood. We studied the relationship between routine metabolic rate (RMR) and larval life-history traits along a 1500-km latitudinal gradient across Sweden. In a laboratory common garden experiment, we exposed eight common frog Rana temporaria populations to two experimental temperatures (15 and 18 °C) and measured RMR using flow-through respirometry. We found significant differences among populations in RMR, but there was no evidence for a linear relationship between latitude and RMR in either temperature treatment. However, we found a concave relationship between latitude and RMR at the lower experimental temperature. RMR was not correlated with growth rate at population or at individual levels. The results obtained suggest that, unlike in growth and development rates, there is no latitudinal cline in RMR in R. temporaria tadpoles.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 217–224.     

The energetics of starvation and growth after refeeding in juveniles of three cyprinid species

Synopsis Experiments were conducted to monitor changes in body mass and metabolic energy expenditure before, during, and after periods of starvation in juveniles of three species of cyprinids: Leuciscus cephalus, Chalcalburnus chalcoides mento, and Scardinius erythrophthalmus. During the starvation period all fish lost weight at about the same rate and the total amount of oxygen consumed during an experimental period of 20 h was about 40% lower in the starved than in the fed groups. Upon refeeding, both mass specific maintenance; and routine rates of metabolism as well as relative growth rates increased rapidly, the peaks of these increases being directly proportional to the length of the starvation period. Maximum compensatory growth was observed after four weeks of starvation in C. chalcoides and S. erythrophthalmus, with relative growth rates reaching 30% d^-1 during the first measuring interval after refeeding. The pattern of time-dependent compensatory growth displayed by these fish is similar to the responses of a colonial hydroid in which the rate of catch-up growth increased with the amount of stress to which the animals had been exposed. The exact cost of compensatory growth cannot be calculated because oxygen consumption and growth were not measured simultaneously. However, on the basis of data and calculations reported by Wieser & Medgyesy (1990) it appears that compensatory growth, if fuelled by the metabolic power indicated by our measurements of oxygen consumption, would have to be about twice as efficient as normal growth in the related species Rutilus rutilus.     

Adaptive variation in growth rate: life history costs and consequences in the speckled wood butterfly,Pararge aegeria

An important assumption made in most lifehistory theory is that there is a trade-off between age and size at reproduction. This trade-off may, however, disappear if growth rate varies adaptively. The fact that individuals do not always grow at the maximum rate can only be understood if high growth rates carry a cost. This study investigates the presence and nature of such costs inPararge aegeria. Five females from two populations with known differences in life history (south Sweden and Maderia) were allowed to oviposit in the laboratory and their offspring were reared in environmental chambers under conditions leading to direct development. We measured several aspects of life history, including development times, pupal and adult weights, growth rate, female fecundity, longevity and larval starvation endurance. In both populations there seemed to be genetic variation in growth rate. There was no evidence for a trade-off between age and size at pupation. As predicted, larvae with high growth rates also lost weight at a relatively higher rate during starvation. High weight-loss rates were furthermore associated with a lower probability of surviving when food became available again. This is apparently the first physiological trade-off with growth rate that has been experimentally demonstrated. In both populations there were significant differences in growth rate between the sexes, but the populations differed in which sex was growing at the highest rate. In Sweden males had higher growth rates than females, whereas the reverse was true for Madeira. These patterns most likely reflect differences in selection for protandry, in turn caused by differences in seasonality between Sweden and Madeira. Together with the finding that males had shorter average longevity than females in the Swedish, but not in the Maderiran, population, this indicates that a lower adult quality also may be a cost of high growth rate. We argue that for the understanding of life history variation it is necessary to consider not only the two dimensions of age and size, but also to take into full account the triangular nature of the relationship between size, time and growth rate.     

Latitudinal clines in alternative life histories in a geometrid moth

The relative roles of genetic differentiation and developmental plasticity in generating latitudinal gradients in life histories remain insufficiently understood. In particular, this applies to determination of voltinism (annual number of generations) in short‐lived ectotherms, and the associated trait values. We studied different components of variation in development of Chiasmia clathrata (Lepidoptera: Geometridae) larvae that originated from populations expressing univoltine, partially bivoltine or bivoltine phenology along a latitudinal gradient of season length. Indicative of population‐level genetic differentiation, larval period became longer while growth rate decreased with increasing season length within a particular phenology, but saw‐tooth clines emerged across the phenologies. Indicative of phenotypic plasticity, individuals that developed directly into reproductive adults had shorter development times and higher growth rates than those entering diapause. The most marked differences between the alternative developmental pathways were found in the bivoltine region suggesting that the adaptive correlates of the direct development evolve if exposed to selection. Pupal mass followed a complex cline without clear reference to the shift in voltinism or developmental pathway probably due to varying interplay between the responses in development time and growth rate. The results highlight the multidimensionality of evolutionary trajectories of life‐history traits, which either facilitate or constrain the evolution of integrated traits in alternative phenotypes.     

Compensatory growth and oxidative stress in a damselfly

Physiological costs of compensatory growth are poorly understood, yet may be the key components in explaining why growth rates are typically submaximal. Here we tested the hypothesized direct costs of compensatory growth in terms of oxidative stress. We assessed oxidative stress in a study where we generated compensatory growth in body mass by exposing larvae of the damselfly Lestes viridis to a transient starvation period followed by ad libitum food. Compensatory growth in the larval stage was associated with higher oxidative stress (as measured by induction of superoxide dismutase and catalase) in the adult stage. Our results challenge two traditional views of life-history theory. First, they indicate that age and mass at metamorphosis not necessarily completely translate larval stress into adult fitness and that the observed physiological cost may explain hidden carry-over effects. Second, they support the notion that costs of compensatory growth may be associated with free-radical-mediated trade-offs and not necessarily with resource-mediated trade-offs.     

Stronger compensatory growth in a permanent-pond Lestes damselfly relative to temporary-pond Lestes

Compensatory growth where animals compensate for time stress or transient nutritional or thermal stress by accelerating their growth rate is widespread. We know, however, relatively little about the evolution and ecological correlates of compensatory growth. For this we need studies on congeneric species with known phylogenetic relationships that also focus on the associated largely understudied costs. Here we tested for compensatory growth and associated costs in response to time stress (manipulated by photoperiod) and a transient period of starvation or cooling in larvae of the permanent-pond damselfly Lestes eurinus , and compare the results with former studies on temporary-pond Lestes . Larvae showed full compensation in body mass at emergence for all combinations of time stress and starvation or cooling. Unexpectedly, compensatory growth to starvation or cooling was not stronger under time stress. Instead, males under time stress delayed emergence after these transient stressors. In line with a stronger compensatory growth response to time stress than to the other stressors, physiological costs in terms of a reduced investment in immune response (measured as phenoloxidase activity) and energy storage (measured as fat content) were detected only under time stress. Compared to temporary-pond Lestes , L. eurinus showed stronger compensatory growth to time stress. We hypothesize that the stronger compensatory (growth) response in permanent-pond Lestes co-evolved with their derived slower lifestyle when they invaded permanent ponds.     

山地麻蜥继饥饿后的补偿生长

动物继饥饿后一段时间后恢复喂食,在恢复生长阶段中常出现高于正常生长速度的补偿生长现象.有关脊椎动物补偿增长的研究主要集中在畜禽类、哺乳类和鱼类(Wilson et al.,1960;Plavnik et al.,1985;Drew et al.,1975;Pitts,1986;Kim et al.,1995),并且已在一些经济动物的饲养中利用补偿增长效应而提高经济效益.爬行动物是否存在补偿生长的现象迄今不明.本研究以山地麻蜥(Eremias breuchleyi)作为实验对象,研究其继饥饿后的补偿生长,预期为揭示爬行动物饥饿胁迫条件下的生长对策提供基础资料.     

Genetics of diapause in the comma butterfly Polygonia c‐album

The processes of local adaptation and ecological speciation can be better understood by studying the genetic background of life‐history decisions. The sex chromosomes host genes for many population differences in the Lepidoptera and therefore the inheritance of diapause determination in the butterfly Polygonia c‐album may be hypothesized to be sex‐linked. In the present study, Polygonia c‐album (L.) from Spain and Sweden and hybrid offspring are raised under an LD 17 : 7 h photocycle that induces most pure Swedish individuals to develop into the diapausing dark morph and most pure Spanish individuals into the light and directly‐developing morph. If inheritance of the daylength threshold for diapause is X‐linked, as is known to be the case for host‐plant preferences, females should follow the developmental path of their male parents' populations. However, female hybrids instead have a diapause propensity intermediate to that of their parental stocks and, consequentially, diapause determination is not X‐linked. However, male hybrids eclose as the diapausing morph to a higher extent than females and, moreover, this pattern is more pronounced in the Spanish female × Swedish male cross than in the reciprocal cross. Hence, it is concluded that the genetic determination of the critical daylength for diapause is mainly autosomal but with some influence of sex‐linked genes and/or parental effects, possibly as an effect of the importance of protandry for males. Such sex effects could provide a starting point for the evolution of population differences inherited on the sex chromosomes.     

Inter- and intrapopulation variation in thermal reaction norms for growth rate: evolution of latitudinal compensation in ectotherms with a genetic constraint

In ectotherms, lower temperatures in high-latitude environments would theoretically reduce the annual growth rates of individuals. If slower growth and resultant smaller body size reduce fitness, individuals in higher latitudes may evolve compensatory responses. Two alternative models of such latitudinal compensation are possible: Model I: thermal reaction norms for growth rates of high-latitude individuals may be horizontally shifted to a lower range of temperatures, or Model II: reaction norms may be vertically shifted so that high-latitude individuals can grow faster across all temperatures. Model I is expected when annual growth rates in the wild are only a function of environmental temperatures, whereas Model II is expected when individuals in higher latitudes can only grow during a shorter period of a year. A variety of mixed strategies of these two models are also possible, and the magnitude of horizontal versus vertical variation in reaction norms among latitudinal populations will be indicative of the importance of "temperature" versus "seasonality" in the evolution of latitudinal compensation. However, the form of latitudinal compensation may be affected by possible genetic constraints due to the genetic architecture of reaction norms. In this study, we examine the inter- and intrapopulation variations in thermal reaction norms for growth rate of the medaka fish Oryzias latipes. Common-environment experiments revealed that average reaction norms differed primarily in elevation among latitudinal populations in a manner consistent with Model II (adaptation to "seasonality"), suggesting that natural selection in high latitudes prefers individuals that grow faster even within a shorter growing season to individuals that have longer growing seasons by growing at lower temperatures. However, intrapopulation variation in reaction norms was also vertical: some full-sibling families grew faster than others across all temperatures examined. This tendency in intrapopulation genetic variation for thermal reaction norms may have restricted the evolution of latitudinal compensation, irrespective of the underlying selection pressure.     

European butterfly populations vary in sensitivity to weather across their geographical ranges

Aim

The aim was to assess the sensitivity of butterfly population dynamics to variation in weather conditions across their geographical ranges, relative to sensitivity to density dependence, and determine whether sensitivity is greater towards latitudinal range margins.

Location

Europe.

Time period

1980–2014.

Major taxa studied

Butterflies.

Methods

We use long‐term (35 years) butterfly monitoring data from > 900 sites, ranging from Finland to Spain, grouping sites into 2° latitudinal bands. For 12 univoltine butterfly species with sufficient data from at least four bands, we construct population growth rate models that include density dependence, temperature and precipitation during distinct life‐cycle periods, defined to accommodate regional variation in phenology. We use partial R² values as indicators of butterfly population dynamics' sensitivity to weather and density dependence, and assess how these vary with latitudinal position within a species' distribution.

Results

Population growth rates appear uniformly sensitive to density dependence across species' geographical distributions, and sensitivity to density dependence is typically greater than sensitivity to weather. Sensitivity to weather is greatest towards range edges, with symmetry in northern and southern parts of the range. This pattern is not driven by variation in the magnitude of weather variability across the range, topographic heterogeneity, latitudinal range extent or phylogeny. Significant weather variables in population growth rate models appear evenly distributed across the life cycle and across temperature and precipitation, with substantial intraspecific variation across the geographical ranges in the associations between population dynamics and specific weather variables.

Main conclusions

Range‐edge populations appear more sensitive to changes in weather than those nearer the centre of species' distributions, but density dependence does not exhibit this pattern. Precipitation is as important as temperature in driving butterfly population dynamics. Intraspecific variation in the form and strength of sensitivity to weather suggests that there may be important geographical variation in populations' responses to climate change.     

Adaptive variation in energy acquisition and allocation among latitudinal populations of the Atlantic silverside

Understanding the evolution of growth rate requires knowledge of the physiology of growth. This study explored the physiological basis of countergradient variation (CnGV) in somatic growth across latitudinal populations of the Atlantic silverside, Menidia menidia. Energetics of northern (Nova Scotia, Canada) and southern (South Carolina, USA) genotypes were compared across resource levels, temperatures, and fish sizes to identify trade-offs to rapid growth. Offered unlimited resources, genotypes differed in both energy acquisition and allocation. Food consumption, growth, and efficiency of northern genotypes were consistently higher than in southern genotypes, across temperatures and body sizes. Feeding metabolism (specific dynamic action; SDA) was proportional to meal size, differing between genotypes to the extent that food consumption differed. Given limited resources, northern and southern genotypes displayed similar growth, efficiency, routine activity, and SDA across temperatures and fish sizes. Routine metabolism was equal at 17°C and 22°C, yet was significantly higher in northern fish at 28°C. Growth rates in M. menidia do not appear to trade off across environments or body sizes, i.e., at no temperature, ration, or size do southern fish outgrow northern conspecifics. Nor does submaximal growth result from increased costs of maintenance, tissue synthesis, or routine activity. Based on our findings, we propose that CnGV consumption and growth in M. menidia likely result from trade-offs with other energetic components, namely sustained and burst swimming. Received: 26 January 1999 / Accepted: 14 September 1999     

Overwintering strategy of two closely related forms of Cloeon (dipterum?) (Ephemeroptera) from Sweden and England

SUMMARY. Comparison is made of resistance to anoxia at 0°C of an English and a Swedish winter larval population of two closely related forms of Cloeon (dipterum?). The English population was not very resistant but contained a few slightly resistant larvae; the Swedish population was very resistant. Swedish larvae initiated hibernation more rapidly than English larvae and were also more resistant to starvation. The different properties of the populations are seen as an adaptation to different winter conditions in ponds in England and Sweden. Evidence is presented that low temperatures but not decreasing photoperiod are decisive for the final induction of hibernation in the larvae. In Swedish larvae this induction starts at between 4 and 5°C.