Lack Of Local Adaptation Research Articles

Elevational range limits in naturalized Rumex conglomeratus likely formed by climate and lack of local adaptation

One of the fundamental questions in ecology is why species occur in some areas and not in others. Range limits, the boundaries between a species’ presence and absence, reflect the interplay of dispersal and population dynamics driven by biotic and abiotic conditions. As a result, range limits may shift as dispersal barriers are removed, climates change, and local species composition is altered, but the relative importance of these mechanisms is still not well understood. This is particularly true for introduced species, where current range limits may or may not reflect range limits at equilibrium, and is becoming more pressing under the effects of global climate change. To understand the drivers and stability of range limits in introduced Rumex conglomeratus, we used common garden experiments growing plants within, at the edge of and beyond their current range edge. Seeds were sourced from both lowland and upland populations and planted at all three sites. By measuring survival, growth, and the occurrence of reproduction, we tested whether upland populations are locally adapted to high elevation sites and whether plants were capable of surviving and reproducing above the current range edge. However, we found that upland populations were not better adapted to higher elevations, and often were small and performed more poorly than lowland populations across sites. Upland populations appear to be maintained by human-aided seed dispersal from lowland populations, which may constrain the opportunity for local adaptation. Although some plants survived above the current range edge, frost and growing season length restricted plant size and reproduction was infrequent. Therefore, the current range limit seems unlikely to expand as long as regular frost continues at the range edge and dispersal from the lowland continues to prevent local adaptation to upland environments.

Skull shape of a widely distributed, endangered marsupial reveals little evidence of local adaptation between fragmented populations.

The biogeographic distribution of diversity among populations of threatened mammalian species is generally investigated using population genetics. However, intraspecific phenotypic diversity is rarely assessed beyond taxonomy‐focused linear measurements or qualitative descriptions. Here, we use a technique widely used in the evolutionary sciences—geometric morphometrics—to characterize shape diversity in the skull of an endangered marsupial, the northern quoll, across its 5,000 km distribution range along Northern Australia. Skull shape is a proxy for feeding, behavior, and phenotypic differentiation, allowing us to ask whether populations can be distinguished and whether patterns of variation indicate adaptability to changing environmental conditions. We analyzed skull shape in 101 individuals across four mainland populations and several islands. We assessed the contribution of population, size, sex, rainfall, temperature, and geography to skull shape variation using principal component analysis, Procrustes ANOVA, and variation partitioning analyses. The populations harbor similar amounts of broadly overlapping skull shape variation, with relatively low geographic effects. Size predicted skull shape best, coinciding with braincase size variation and differences in zygomatic arches. Size‐adjusted differences in populations explained less variation with far smaller effect sizes, relating to changes in the insertion areas of masticatory muscles, as well as the upper muzzle and incisor region. Climatic and geographic variables contributed little. Strikingly, the vast majority of shape variation—76%—remained unexplained. Our results suggest a uniform intraspecific scope for shape variation, possibly due to allometric constraints or phenotypic plasticity beyond the relatively strong allometric effect. The lack of local adaptation indicates that cross‐breeding between populations will not reduce local morphological skull (and probably general musculoskeletal) adaptation because none exists. However, the potential for heritable morphological variation (e.g., specialization to local diets) seems exceedingly limited. We conclude that 3D geometric morphometrics can provide a comprehensive, statistically rigorous phenomic contribution to genetic‐based conservation studies.

Effects of selection and local adaptation on resilience and economic suitability in Apis mellifera carnica

Modern techniques of selective breeding show high potential to improve economically important traits of honey bees. However, breeding may neglect fundamental rules of natural selection. The objective of this study was to analyze the effects of selection and local adaptation on some relevant breeding traits of Apis mellifera carnica. We compared open mated queens from three different origins: local Croatian genotypes that are under controlled selection since five generations (MS), a local genotype that was never under selective breeding (NS) and, finally, a non-local genotype from a long-lasting German breeding program (HS). Generally, colonies with queens from breeding programs had better scores for defensive behavior, calmness, and swarming. In contrast, colonies from the NS group showed higher expression of Varroa destructor resistance traits. Although the HS group showed the highest score in most of the behavioral traits, the low overwintering index of colonies from this group after both wintering periods indicated a lack of local adaptation. This research underlines the relevance of breeding activities for the resilience of honey bee populations and the achievement of local adaptation.

Local-scale diversity and adaptation along elevational gradients assessed by reciprocal transplant experiments: lack of local adaptation in silver fir populations

Silver fir transplantations along elevational gradients revealed a high diversity but no local adaptation. Populations displayed similar abilities to adapt to new environments including those due to climate change. The sustainability of forest stands depends on the ability of species and communities to adapt by combining plasticity and genetic evolution. Although well-documented at the scale of species distributions, the variability and adaptation of forest tree genetic resources are less understood at the short-distance scale. We analysed the effects of genetic and environmental factors on the local-scale phenotypic diversity of traits related to adaptation in Abies alba. We also sought to highlight local adaptation, revealing past selection. Six adaptive traits related to growth, phenology and survival were measured on seedlings from 57 half-sib families collected from 15 provenances and planted in a nine-site reciprocal transplant experiment distributed along three elevational gradients. Most part of the phenotypic variability was attributed to the environmental factors. Provenances and families had also significant effects on seedling performances, but the genetic variability was mostly attributed to the families. No pattern of local adaptation was observed, except in the presence of lateral branches in the driest garden. The absence of local adaptation suggests a similar ability of all silver fir populations to develop in the various environments. This result provides favourable conditions for coping with the ongoing climate change without exotic resources enrichment.

Are local plants the best for ecosystem restoration? It depends on how you analyze the data.

One of the key questions in ecosystem restoration is the choice of the seed material for restoring plant communities. The most common strategy is to use local seed sources, based on the argument that many plants are locally adapted and thus local seed sources should provide the best restoration success. However, the evidence for local adaptation is inconsistent, and some of these inconsistencies may be due to different experimental approaches that have been used to test for local adaptation. We illustrate how conclusions about local adaptation depend on the experimental design and in particular on the method of data analysis. We used data from a multispecies reciprocal transplant experiment and analyzed them in three different ways: (1) comparing local vs. foreign plants within species and sites, corresponding to tests of the “local is best” paradigm in ecological restoration, (2) comparing sympatric vs. allopatric populations across sites but within species, and (3) comparing sympatric and allopatric populations across multiple species. These approaches reflect different experimental designs: While a local vs. foreign comparison can be done even in small experiments with a single species and site, the other two approaches require a reciprocal transplant experiment with one or multiple species, respectively. The three different analyses led to contrasting results. While the local/foreign approach indicated lack of local adaptation or even maladaptation, the more general sympatric/allopatric approach rather suggested local adaptation, and the most general cross‐species sympatric/allopatric test provided significant evidence for local adaptation. The analyses demonstrate how the design of experiments and methods of data analysis impact conclusions on the presence or absence of local adaptation. While small‐scale, single‐species experiments may be useful for identifying the appropriate seed material for a specific restoration project, general patterns can only be detected in reciprocal transplant experiments with multiple species and sites.

Extensive genetic diversity among populations of the malaria mosquito Anopheles moucheti revealed by population genomics

Malaria vectors are exposed to intense selective pressures due to large-scale intervention programs that are underway in most African countries. One of the current priorities is therefore to clearly assess the adaptive potential of Anopheline populations, which is critical to understand and anticipate the response mosquitoes can elicit against such adaptive challenges. The development of genomic resources that will empower robust examinations of evolutionary changes in all vectors including currently understudied species is an inevitable step toward this goal. Here we constructed double-digest Restriction Associated DNA (ddRAD) libraries and generated 6461 Single Nucleotide Polymorphisms (SNPs) that we used to explore the population structure and demographic history of wild-caught Anopheles moucheti from Cameroon. The genome-wide distribution of allelic frequencies among samples best fitted that of an old population at equilibrium, characterized by a weak genetic structure and extensive genetic diversity, presumably due to a large long term effective population size. Estimates of FST and Linkage Disequilibrium (LD) across SNPs reveal a very low genetic differentiation throughout the genome and the absence of segregating LD blocks among populations, suggesting an overall lack of local adaptation. Our study provides the first investigation of the genetic structure and diversity in An. moucheti at the genomic scale. We conclude that, despite a weak genetic structure, this species has the potential to challenge current vector control measures and other rapid anthropogenic and environmental changes thanks to its great genetic diversity.

Genetic and adaptive trait variation in seedlings of European beech provenances from Northern Germany

AbstractEuropean beech (Fagus sylvaticaL.) will most likely be threatened by climate change. Therefore, more knowledge of its adaptation potential to changing environmental conditions is required. Several studies showed differences in adaptive traits for beech populations from across Europe, but there is also growing evidence for microevolutionary processes occurring within short geographic distances in this species, or even a lack of local adaptation. Hence, a more regional perspective for adaptation research in beech might be appropriate. Here, we investigated the performance (height, height increment and mortality) and genetic structure based on microsatellite markers of 2400 beech seedlings from provenances growing along a temperature and precipitation gradient in Northern Germany in a common garden experiment. Differences for all traits were found among provenances. Provenances from lower precipitation areas did not perform better than provenances from higher precipitation areas at the common garden site, which was located near the lower precipitation limit of beech. Further, neighboring provenances growing on either sandy or loamy soils showed more different adaptive trait variation than distant provenances. We detected minor genetic structure among provenances and a high genetic diversity within them. Thus, small-scale adaptive trait variation in beech can occur, despite low but significant genetic population structure among provenances.

Up the mountain, north to the pole: Do species’ elevational and latitudinal limits match?

It is a long-held assumption that species' upper elevational and latitudinal range limits are correlated-i.e., species that grow at higher latitudes also reach higher elevations-but the degree to which these limits match and the climatic factors controlling them have rarely been quantitatively assessed. We compared the upper range limits of tree species along latitudinal and elevational gradients to assess the influence of specific climatic factors-winter temperature, summer temperature, and growing season length-in determining species' range limits. We determined the climatic limits for each of 28 common tree species along a latitudinal gradient in Eastern North America and across an elevational gradient in the Great Smoky Mountains. We calculated the degree of climatic mismatch between species' limits along the two gradients.We found strong positive relationships between species' latitudinal and elevational climatic limits. Winter temperatures were much lower at species' poleward, compared to upper elevational, range limits, but there were close matches between limits for variables related to summer temperature and growing season length. Results suggest that low summer temperatures and short growing season length limit species' distributions along both latitudinal and elevational gradients, whereas winter temperature does not play a critical role. Narrower ranges along elevational gradients may be due to a lack of local adaptation caused by increased gene flow along "shorter" gradients, where upslope dispersal of individuals maladapted to cold restricts upward expansion. Narrower ranges along the latitudinal gradient may be due to limited migration northward from historical range centers in the southern Appalachians.

Vocal flexibility and regional variation in free-tailed bat songs

Male Brazilian free tailed bats (Tadarida brasiliensis), sing to attract females and defend territories during the mating season. These songs are unusual among mammalian vocalizations in that they are highly complex and hierarchically structured. Songs are composed of multiple syllables which are combined into three phrases that vary in number and order across renditions. While much work has been done on regional vocal variation in birds, relatively a few studies have found similar evidence in mammals. This study aimed to determine if T. brasiliensis songs vary across agographical regions. To accomplish this, we compared spectro-temporal characteristics, and phrase composition of songs recorded from wild colonies in various locations throughout Florida, Georgia, and Texas. Although we found considerable inter-individual and within-individual variation, there are salient regional differences in song structure. These findings combined with a high level of within-individual flexibility, and the lack of local adaptation in foraging echolocation pulses, support a possible role of vocal learning in song production in this species.

A tale of two hatcheries: Assessing bias in the hatchery process for Atlantic salmon (Salmo salar L.)

Abstract Stock enhancement of Atlantic salmon ( Salmo salar L.), a fish of considerable economic and social importance, is commonplace. Supportive-breeding is a well-recognised method of enhancement which, when compared with traditional hatchery practices, is thought to reduce the severity of selection pressures on broodstock fish. Critically, in supportive-breeding programmes, the eggs and sperm used in the breeding process are taken from wild adult fish originating from the same catchment that resulting juvenile fish are subsequently stocked into, thereby avoiding problems associated with a lack of local adaptation in the stocked fish. Previous studies have indicated that sex bias during the hatchery process may result in reduced genetic diversity of the offspring. Utilising 16 microsatellite loci and two expressed sequence tag (EST) loci, we examined progeny from two hatcheries located on the rivers Exe and Tamar in southwest England, assessing the genetic diversity and parental contribution at each. Two strains were assessed within each hatchery. Genetic diversity was found to be reduced in offspring compared with that of the parent fish. This is likely the result of utilising a small number of broodstock in combination with parental bias. In the four hatchery strains studied (Bar, LEx, Lyd and TXL), parental contribution ranged between 2.1 and 29.2%, 12.2–51.0%, 2.0–70.0% and 4.0–40.0%, respectively. If this practice is to be continued, efforts should be made to improve adherence to national rearing guidelines by increasing the number of broodstock fish utilised and ensuring a more balanced contribution of all adults during the crossing process. Ultimately, we suggest a need to review the suitability of current national Atlantic salmon hatchery guidelines, particularly with regard to their use and relevance in small European rearing systems.

Preference and Performance in Plant–Herbivore Interactions across Latitude–A Study in U.S. Atlantic Salt Marshes

High-latitude plants are often more palatable to herbivores than low-latitude conspecifics. Does increased plant palatability lead to better herbivore performance? Our field and laboratory work investigated (A) whether high-latitude plants have traits indicating that they should be higher-quality foods for herbivores; (B) whether geographic differences in plant quality are more important than local adaptation of herbivores. We studied 3 plant species and 6 invertebrate herbivores in U.S. Atlantic Coast. Past studies had shown high-latitude individuals of these plants are more palatable than low-latitude conspecifics. We documented plant traits and herbivore performance (body size) in the field across latitude. We collected individuals from different latitudes for factorial (plant region x herbivore region) laboratory experiments, examining how herbivore performance was affected by plant region, herbivore region, and their interaction (i.e., local adaptation). Field surveys suggested high-latitude plants were likely of higher quality to herbivores. Leaf nitrogen content in all plant species increased toward high latitudes, consistent with lower leaf C/N and higher leaf chlorophyll content at high latitudes. Furthermore, leaf toughness decreased toward higher latitudes in 1 species. The body size of 4 herbivore species increased with latitude, consistent with high-latitude leaves being of higher quality, while 2 grasshopper species showed the opposite pattern, likely due to life-history constraints. In the laboratory, high-latitude plants supported better performance in 4 herbivore species (marginal in the 5th). The geographic region where herbivores were collected affected herbivore performance in all 6 species; however, the pattern was mixed, indicating a lack of local adaptation by herbivores to plants from their own geographic region. Our results suggest that more-palatable plants at high latitudes support better herbivore growth. Given that geographic origin of either plants or herbivores can affect herbivore performance, the nature of plant-herbivore interactions is likely to change if climate change “reshuffles” plant and herbivore populations across latitude.

Varying herbivore population structure correlates with lack of local adaptation in a geographic variable plant-herbivore interaction.

Local adaptation of parasites to their hosts due to coevolution is a central prediction of many theories in evolutionary biology. However, empirical studies looking for parasite local adaptation show great variation in outcomes, and the reasons for such variation are largely unknown. In a previous study, we showed adaptive differentiation in the arctiid moth Utetheisa ornatrix to its host plant, the pyrrolizidine alkaloid-bearing legume Crotalaria pallida, at the continental scale, but found no differentiation at the regional scale. In the present study, we sampled the same sites to investigate factors that may contribute to the lack of differentiation at the regional scale. We performed field observations that show that specialist and non-specialist polyphagous herbivore incidence varies among populations at both scales. With a series of common-garden experiments we show that some plant traits that may affect herbivory (pyrrolizidine alkaloids and extrafloral nectaries) vary at the regional scale, while other traits (trichomes and nitrogen content) just vary at the continental scale. These results, combined with our previous evidence for plant population differentiation based on larval performance on fresh fruits, suggest that U. ornatrix is subjected to divergent selection even at the regional scale. Finally, with a microsatellite study we investigated population structure of U. ornatrix. We found that population structure is not stable over time: we found population differentiation at the regional scale in the first year of sampling, but not in the second year. Unstable population structure of the herbivore is the most likely cause of the lack of regional adaptation.

Local expansion and selection of soil bacteria in a glacier forefield

SummaryIn the environment of Alpine glacier forefields, bacteria represent the functional link between initial soil development and secondary colonization. An important question is whether soil bacteria are adapted to the poor nutrient availability in this environment and whether selection processes significantly limit their local expansion along the gradients of chemical and biological factors. To address these questions, we used a two‐dimensional sampling strategy at our study site, the Damma glacier forefield, Switzerland, to characterize the soil environment by selected biogeochemical parameters. Our results revealed two contrasting sites that differed in time since deglaciation (‘young’ and ‘old’ soil, ≤ 13 years and > 53 years of ice‐free conditions) and vegetation cover (threefold increase), but also showed significant differences in soil properties thought to be relevant for the successional development of glacier forefield soils, such as pH (0.5‐fold decrease), ammonium (0.5‐fold decrease) concentration, and the content of total organic carbon (10‐fold increase). Isolated strains, affiliated to the genus Pseudomonas, according to their 16S rDNA profile, were tested experimentally for local adaptation by a reciprocal transfer experiment. The bacteria from both young and old soils showed a significant interaction with their local environment; the direction of the interaction, however, did not follow the expected pattern of local adaptation. The significant genoype‐with‐environment interaction indicates a limited local expansion of soil bacteria in the Damma glacier forefield over the range of only 110 m. The lack of local adaptation could be explained by environmental constraints such as exclusion of competition, different migration behaviour of bacteria from young and old soil, or the ability of early colonizing bacteria to survive under the glacier ice.

Genotype × Region Interaction for Two‐Row Barley Yield in Canada

Barley (Hordeum vulgare L.) breeding programs recognize eastern and western Canada as separate target regions, but the extent of local adaptation to regions and subregions within them has not been studied. Genotype × region and subregion interactions were estimated in 145 lines from the two‐row barley cross Harrington/TR306 in 22 trials in 1992‐1993. The trials were grouped into five subregions (Maritimes–Quebec, Ontario, Manitoba–North Dakota, Saskatchewan, and Alberta) and two regions (eastern Canada and western Canada plus North Dakota). Variance components were estimated by a model in which the genotype × location (σ2GL) variance was subdivided into a genotype × region (or subregion) variance (σ2GS), and a within‐region or ‐subregion σ2GL No σ2GS was observed within the eastern or western regions, and genotypic correlations across subregions within regions approached 1.0. Significant σ2GS was observed for eastern versus western Canada, but the correlation between genotypic effects across these regions was 0.83. In a selection experiment, subdivision of the eastern or western regions did not increase response. Selection in the east produced greater yields in both the east and west. The same genotype ranked first for yield in both regions. There was little specific adaptation to subregions, and two‐row barley genotypes were broadly adapted across northern North America. Further subdivision of the regions is unwarranted, and selection in either region is likely to result in response in the other. The lack of local adaptation indicates that breeding programs that test broadly are likely to outperform ones that are narrowly targeted.