ORCID Profile
0000-0001-5945-6545
Current Organisations
Uppsala University
,
University of Queensland
,
Swedish University of Agricultural Sciences
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Publisher: Cold Spring Harbor Laboratory
Date: 18-06-2020
DOI: 10.1101/2020.06.17.156281
Abstract: Entering and exiting winter dormancy presents important trade-offs between growth and survival at northern latitudes and many forest trees display local adaptation across latitude. Transfers of a species outside its native range introduce the species to novel combinations of environmental conditions potentially requiring different combinations of alleles to optimize growth. We performed genome wide association analyses and a selection scan in a P. trichocarpa mapping population derived from crossings between clones collected across the native range and introduced into Sweden. GWAS analyses were performed using phenotypic data collected across two field seasons and in a controlled phytotron experiment. We uncovered 629 putative candidate genes associated with spring and autumn phenology traits as well as with growth. Many regions harboring variation significantly associated with the initiation of leaf shed and leaf autumn coloring appeared to have been evolving under positive selection in the native environments of P. trichocarpa . A comparison between the candidate genes identified with results from earlier GWAS analyses performed in the native environment found a smaller overlap for spring phenology traits than for autumn phenology traits, aligning well with earlier observations that spring phenology transitions have a more complex genetic basis that autumn phenology transitions.
Publisher: Cold Spring Harbor Laboratory
Date: 13-06-2020
DOI: 10.1101/2020.06.12.148445
Abstract: In a warming climate, the ability to accurately predict and track shifting environmental conditions will be fundamental for plant survival. Environmental cues define the transitions between growth and dormancy as plants synchronise development with favourable environmental conditions, however these cues are predicted to change under future climate projections which may have profound impacts on tree survival and growth. Here, we use a quantitative genetic approach to estimate the genetic basis of spring and autumn phenology in Populus trichocarpa to determine this species capacity for climate adaptation. We measured bud burst, leaf coloration, and leaf senescence traits across two years (2017-2018) and combine these observations with measures of lifetime growth to determine how genetic correlations between phenology and growth may facilitate or constrain adaptation. Timing of transitions differed between years, although we found strong cross year genetic correlations in all traits, suggesting that genotypes respond in consistent ways to seasonal cues. Spring and autumn phenology were correlated with lifetime growth, where genotypes that burst leaves early and shed them late had the highest lifetime growth. We also identified substantial heritable variation in the timing of all phenological transitions (h 2 = 0.5-0.8) and in lifetime growth (h 2 = 0.8). The combination of abundant additive variation and favourable genetic correlations in phenology traits suggests that cultivated varieties of P. trichocarpa have the capability to create populations which may adapt their phenology to climatic changes without negative impacts on growth.
Publisher: Wiley
Date: 02-01-2019
DOI: 10.1111/EVO.13665
Abstract: Species differences are maintained by the cumulative effect of factors that reduce gene flow between ergent lineages. In this issue, Karrenberg et al. quantify multiple genetic and environmental barriers to gene exchange between two closely related plant species and find that adaptation to ergent environments has the greatest effect on reproductive isolation.
Publisher: Cold Spring Harbor Laboratory
Date: 24-07-2022
DOI: 10.1101/2022.07.24.501324
Abstract: Herbivores can affect plant population dynamics both directly because of the damage they inflict, and indirectly by moderating conditions for plant recruitment, competition and other biotic interactions. Still, the relative importance of indirect effects of herbivores on plant population dynamics is poorly known. We quantified direct and indirect effects of ungulate grazers on population growth rate of the short-lived perennial herb Primula farinosa , using integral projection models based on demographic data collected over 7 years in exclosures and open control plots at nine grassland sites in southern Sweden. In addition, we explored the mechanisms behind indirect effects with simulations. Grazers had negative direct effects on P. farinosa population growth rate, but these were more than balanced by positive indirect effects. The positive indirect effects were mainly linked to improved conditions for plant recruitment. Simulations indicated that indirect effects of ungulate grazers on population growth rate via interactions with pollinators, seed predators, and small herbivores were weak in this system. Synthesis . The results demonstrate that a full understanding of the effects of grazing on plant population dynamics requires that both direct and indirect effects are identified and quantified. Plant species vary considerably in their response to shifts in grazing regime. Our study sets an ex le for how the causes of such variation can be assessed, and thus providing a better understanding of the variable effects of herbivores on plant fitness, abundance and distribution.
Publisher: Wiley
Date: 08-08-2016
DOI: 10.1111/EVO.12994
Abstract: Ecological speciation occurs when reproductive isolation evolves between populations adapting to contrasting environments. A key prediction of this process is that the fitness of hybrids between ergent populations should be reduced in each parental environment as a function of the proportion of local genes they carry, a process resulting in ecologically dependent reproductive isolation (RI). To test this prediction, we use reciprocal transplant experiments between adjacent populations of an Australian wildflower, Senecio lautus, at two locations to distinguish between ecologically dependent and intrinsic genetic reproductive barriers. These barriers can be distinguished by observing the relative fitness of reciprocal backcross hybrids, as they differ in the contribution of genes from either parent while controlling for any intrinsic fitness effects of hybridization. We show ecologically dependent fitness effects in establishment and survival of backcrosses in one transplant experiment, and growth performance in the second transplant experiment. These results suggest natural selection can create strong reproductive barriers that maintain differentiation between populations with the potential to interbreed, and implies a significant role for ecology in the evolutionary ergence of S. lautus.
Publisher: Wiley
Date: 02-01-2019
DOI: 10.1111/EVO.13667
Abstract: Which genome contributes most to patterns of adaptive trait ergence in Drosophila melanogaster across environmental clines? In this issue, Lasne et al. find that genetic variation associated with adaptive traits is mostly distributed between autosomal and mitochondrial genomes with a negligible contribution from the X chromosome.
Publisher: Springer Science and Business Media LLC
Date: 02-07-2021
DOI: 10.1186/S12870-021-03103-5
Abstract: Entering and exiting winter dormancy present important trade-offs between growth and survival at northern latitudes. Many forest trees display local adaptation across latitude in traits associated with these phenology transitions. Transfers of a species outside its native range introduce the species to novel combinations of environmental conditions potentially requiring different combinations of alleles to optimize growth and survival. In this study, we performed genome wide association analyses and a selection scan in a P. trichocarpa mapping population derived from crossings between clones collected across the native range and introduced into Sweden. GWAS analyses were performed using phenotypic data collected across two field seasons and in a controlled phytotron experiment. We uncovered 584 putative candidate genes associated with spring and autumn phenology traits as well as with growth. Many regions harboring variation significantly associated with the initiation of leaf shed and leaf autumn coloring appeared to have been evolving under positive selection in the native environments of P. trichocarpa . A comparison between the candidate genes identified with results from earlier GWAS analyses performed in the native environment found a smaller overlap for spring phenology traits than for autumn phenology traits, aligning well with earlier observations that spring phenology transitions have a more complex genetic basis than autumn phenology transitions. In a small and structured introduced population of P. trichocarpa , we find complex genetic architectures underlying all phenology and growth traits, and identify multiple putative candidate genes despite the limitations of the study population.
Publisher: Wiley
Date: 06-2019
DOI: 10.1002/ECE3.5263
Abstract: Leaf morphology is highly variable both within and between plant species. This study employs a combination of common garden and reciprocal transplant experiments to determine whether differences in leaf shape between Senecio lautus ecotypes has evolved as an adaptive response to ergent ecological conditions. We created a synthetic population of hybrid genotypes to segregate morphological variation between three ecotypes and performed reciprocal transplants where this hybrid population was transplanted into the three adjacent native environments. We measured nine leaf morphology traits across the experimental and natural populations at these sites. We found significant ergence in multivariate leaf morphology toward the native character in each environment, suggesting environmental conditions at each site exert selective pressure that results in a phenotypic shift toward the local phenotype of the wild populations. These associations suggest that differences in leaf morphology between S. lautus ecotypes have arisen as a result of ergent selection on leaf shape or associated traits that confer an adaptive advantage in each environment, which has led to the formation of morphologically distinct ecotypes.
Publisher: Wiley
Date: 08-08-2016
DOI: 10.1111/EVO.13009
Abstract: Adaptation to contrasting environments across a heterogeneous landscape favors the formation of ecotypes by promoting ecological ergence. Patterns of fitness variation in the field can show whether natural selection drives local adaptation and ecotype formation. However, to demonstrate a link between ecological ergence and speciation, local adaptation must have consequences for reproductive isolation. Using contrasting ecotypes of an Australian wildflower, Senecio lautus in common garden experiments, hybridization experiments, and reciprocal transplants, we assessed how the environment shapes patterns of adaptation and the consequences of adaptive ergence for reproductive isolation. Local adaptation was strong between ecotypes, but weaker between populations of the same ecotype. F1 hybrids exhibited heterosis, but crosses involving one native parent performed better than those with two foreign parents. In a common garden experiment, F2 hybrids exhibited reduced fitness compared to parentals and F1 hybrids, suggesting that few genetic incompatibilities have accumulated between populations adapted to contrasting environments. Our results show how ecological differences across the landscape have created complex patterns of local adaptation and reproductive isolation, suggesting that ergent natural selection has played a fundamental role in the early stages of species ersification.
Publisher: Springer Science and Business Media LLC
Date: 04-02-2021
DOI: 10.1007/S12155-021-10249-5
Abstract: In Northern Europe, poplars ( Populus ) can provide biomass for energy and material use, but most available clones were developed for lower latitudes and are unlikely to be well adapted to higher latitudes, even under warmer climates. We thus need to understand how clones respond to climatic conditions and photoperiod, and how these responses can be predicted. We answer these questions exploiting leaf phenological data of Populus clones, grown in six sites across the Baltic region, in Northern Europe, for 2 years with contrasting climatic conditions. Regarding the effects of climatic conditions and photoperiod, within each site, higher temperatures advanced the timing and enhanced the speed of spring and autumn phenology, but reduced the effective growing season length. Across sites, latitude affected the timing of spring and autumn phenology, the speed of spring phenology, and the effective growing season length clone affected only the timing of phenology. Regarding the predictability of clone response to growing conditions, the growing degree day (GDD) model could not predict spring phenology, because the growing degree day threshold for a specific phenological stage was not only clone-, but also latitude- and year-specific. Yet, this GDD threshold allowed a robust ranking of clones across sites and years, thus providing a tool to determine the relative differences across clones, independently of latitude and temperature. A similar, but not as strong, pattern was observed in the timing of spring and autumn phenological stages. Hence, while prediction of spring phenology remains elusive, the ranking of clones based on observations of their phenology in a single location can provide useful indications on the clones’ relative performance under different latitudes and climates.
Publisher: Wiley
Date: 30-05-2016
DOI: 10.1111/EVO.12936
Abstract: Speciation proceeds when gene exchange is prevented between populations. Determining the different barriers preventing gene flow can therefore give insights into the factors driving and maintaining species boundaries. These reproductive barriers may result from intrinsic genetic incompatibilities between populations, from extrinsic environmental differences between populations, or a combination of both mechanisms. We investigated the potential barriers to gene exchange between three adjacent ecotypes of an Australian wildflower to determine the strength of in idual barriers and the degree of overall isolation between populations. We found almost complete isolation between the three populations mainly due to premating extrinsic barriers. Intrinsic genetic barriers were weak and variable among populations. There were asymmetries in some intrinsic barriers due to the origin of cytoplasm in hybrids. Overall, these results suggest that reproductive isolation between these three populations is almost complete despite the absence of geographic barriers, and that the main drivers of this isolation are ecologically based, consistent with the mechanisms underlying ecological speciation.
Publisher: University of Queensland Library
Publisher: Oxford University Press (OUP)
Date: 08-2020
DOI: 10.1002/EVL3.187
Abstract: Adaptation to contrasting environments occurs when advantageous alleles accumulate in each population, but it remains largely unknown whether these same advantageous alleles create genetic incompatibilities that can cause intrinsic reproductive isolation leading to speciation. Identifying alleles that underlie both adaptation and reproductive isolation is further complicated by factors such as dominance and genetic interactions among loci, which can affect both processes differently and obscure potential links between adaptation and speciation. Here, we use a combination of field and glasshouse experiments to explore the connection between adaptation and speciation while accounting for dominance and genetic interactions. We created a hybrid population with equal contributions from four contrasting ecotypes of Senecio lautus (Asteraceae), which produced hybrid genomes both before (F1 hybrid generation) and after (F4 hybrid generation) recombination among the parental ecotypes. In the glasshouse, plants in the second generation (F2 hybrid generation) showed reduced fitness as a loss of fertility. However, fertility was recovered in subsequent generations, suggesting that genetic variation underlying the fitness reduction was lost in subsequent generations. To quantify the effects of losing genetic variation at the F2 generation on the fitness of later generation hybrids, we used a reciprocal transplant to test for fitness differences between parental ecotypes, and F1 and F4 hybrids in all four parental habitats. Compared to the parental ecotypes and F1 hybrids, variance in F4 hybrid fitness was lower, and lowest in habitats that showed stronger native-ecotype advantage, suggesting that stronger natural selection for the native ecotype reduced fitness variation in the F4 hybrids. Fitness trade-offs that were present in the parental ecotypes and F1 hybrids were absent in the F4 hybrid. Together, these results suggest that the genetic variation lost after the F2 generation was likely associated with both adaptation and intrinsic reproductive isolation among ecotypes from contrasting habitats.
Publisher: Cold Spring Harbor Laboratory
Date: 16-01-2019
DOI: 10.1101/520809
Abstract: Testing whether local adaptation and intrinsic reproductive isolation share a genetic basis can reveal important connections between adaptation and speciation. Local adaptation arises as advantageous alleles spread through a population, but whether these same advantageous alleles fail on the genetic backgrounds of other populations remains largely unknown. We used a quantitative genetic breeding design to produce a late generation (F4) recombinant hybrid population by equally mating amongst four contrasting ecotypes of a native Australian daisy for four generations. We tracked fitness across generations and measured morphological traits in the glasshouse, and used a reciprocal transplant to quantify fitness in all four parental habitats. In the glasshouse, plants in the second generation showed a reduction in fitness as a loss of fertility, but this was fully recovered in the following generation. The F4 hybrid lacked extreme phenotypes present in the parental ecotypes, suggesting that genes reducing hybrid fitness were linked to traits specific to each ecotype. In the natural habitats, additive genetic variance for fitness was greatest for habitats that showed stronger native-ecotype advantage, suggesting that a loss of genetic variation present in the parental ecotypes were adaptive in the natural habitats. Reductions in genetic variance for fitness were associated with a loss of ecological trade-offs previously described in the parental ecotypes. Furthermore, natural selection on morphological traits differed amongst the parental habitats, but was not predicted to occur towards the morphology of the parental ecotypes. Together, these results suggest that intrinsic reproductive isolation removed adaptive genetic variation present in the parental ecotypes. The evolution of these distinct ecotypes was likely governed by genetic variation that resulted in both ecological trade-offs and intrinsic reproductive isolation among populations adapted to contrasting environments.
Publisher: Springer Science and Business Media LLC
Date: 08-09-2020
DOI: 10.1038/S41437-020-00363-Z
Abstract: In a warming climate, the ability to accurately predict and track shifting environmental conditions will be fundamental for plant survival. Environmental cues define the transitions between growth and dormancy as plants synchronise development with favourable environmental conditions, however these cues are predicted to change under future climate projections which may have profound impacts on tree survival and growth. Here, we use a quantitative genetic approach to estimate the genetic basis of spring and autumn phenology in Populus trichocarpa to determine this species capacity for climate adaptation. We measured bud burst, leaf coloration, and leaf senescence traits across two years (2017–2018) and combine these observations with measures of lifetime growth to determine how genetic correlations between phenology and growth may facilitate or constrain adaptation. Timing of transitions differed between years, although we found strong cross year genetic correlations in all traits, suggesting that genotypes respond in consistent ways to seasonal cues. Spring and autumn phenology were correlated with lifetime growth, where genotypes that burst leaves early and shed them late had the highest lifetime growth. We also identified substantial heritable variation in the timing of all phenological transitions ( h 2 = 0.5–0.8) and in lifetime growth ( h 2 = 0.8). The combination of additive variation and favourable genetic correlations in phenology traits suggests that populations of cultivated varieties of P. Trichocarpa may have the capability to adapt their phenology to climatic changes without negative impacts on growth.
Publisher: Wiley
Date: 29-04-2023
DOI: 10.1111/GCB.16719
Abstract: Global environmental change is happening at unprecedented rates. Coral reefs are among the ecosystems most threatened by global change. For wild populations to persist, they must adapt. Knowledge shortfalls about corals' complex ecological and evolutionary dynamics, however, stymie predictions about potential adaptation to future conditions. Here, we review adaptation through the lens of quantitative genetics. We argue that coral adaptation studies can benefit greatly from “wild” quantitative genetic methods, where traits are studied in wild populations undergoing natural selection, genomic relationship matrices can replace breeding experiments, and analyses can be extended to examine genetic constraints among traits. In addition, in iduals with advantageous genotypes for anticipated future conditions can be identified. Finally, genomic genotyping supports simultaneous consideration of how genetic ersity is arrayed across geographic and environmental distances, providing greater context for predictions of phenotypic evolution at a metapopulation scale.
Publisher: Informa UK Limited
Date: 02-01-2022
No related grants have been discovered for Thomas Richards.