Biology subjects

Angert, A. L.

Publications and source records attributed to Angert, A. L..

17 recordsLinked to original sources

bioRxiv2026

Eco-evolutionary dynamics are shaped by competition in experimental range expansions

Most theory and empirical research on range expansion assumes populations spread into empty landscapes with abundant resources, however expanding populations are likely to compete with residents. In mathematical models, interspecific competition can lead to pushed wave dynamics, where expansions are driven mainly by individuals dispersing from the core, leading to steeper wavefronts and increased genetic diversity at the edge. These predictions are yet to be tested empirically, and the role of interspecific competition in mediating evolution during range expansion is unclear. We used an experimental system with two duckweed species to ask if interspecific competition leads to pushed-like dynamics and to assess how competition alters evolution during range expansion. We found that competition with a resident reduced expansion speed and absolute variance among replicate expansions, suggesting competition makes expansion speed more predictable. Interspecific competition also changed the relative frequencies of genotypes at the leading edge. While competition was associated with some features of pushed waves, genotype diversity did not vary between treatments. Our results demonstrate that demographic and evolutionary patterns associated with pushed waves may not be universal, and that incorporating selective pressures into future research on eco-evolutionary dynamics of range expansion is key to understanding spreading populations in nature.

ecology↗

bioRxiv2025

Transgenerational plasticity affects fitness and mediates local adaptation

Transgenerational plasticity (TGP) could be as decisive of a factor in phenotypic outcomes as allelic variation and within-generation plasticity. While TGP is often associated with priming offspring to stress in stable environments (where offspring and grandparents are likely to experience similar stresses), our results suggest that TGP is locally adaptive for offspring when grandparents are exposed to environments that match historical conditions, regardless of the offsprings environment. Specifically, we find that Mimulus cardinalis populations from historically wet environments exhibit adaptive TGP in grand-offspring, via increased male and female fitness, only when grandparents experience wet treatments, while TGP is maladaptive when these grandparents experience dry treatments. In contrast, populations from historically dry environments show the opposite. Furthermore, we find that TGP can have a greater effect on both male and female fitness than allelic differences and within-generation plasticity. Our results indicate an additional way that phenotypes arise through local adaption and sheds light on the potential for how rapid evolution might occur.

evolutionary biology↗

bioRxiv2024

The historical biogeography of range expansion predicts spatial patterns in reproductive assurance

Plant reproductive assurance describes the ability of a plant to successfully reproduce in an environment that is potentially devoid of conspecifics and/or pollinators. Traditionally, studies have focused on the role of contemporary ecology---such as pollinator or mate availability---in driving spatial patterns in reproductive assurance within species, however, historical processes such as post-glacial range expansion may be an understudied alternative explanation for geographic variation in mating system. This is because during the process of geographic range expansion into novel habitat, selection should favour individuals that possess traits promoting reproductive assurance (i.e., autonomous selfing or clonal reproduction). Here, we used Northern pink monkeyflower--Erythranthe (Mimulus lewisii--a hermaphroditic, self-compatible, perennial, alpine plant, as a focal species to investigate the historical signatures of geographic range expansion by combining phylogeographic analyses with a greenhouse survey of range-wide reproductive assurance. First, we detected significant geographic variation among populations in two components of reproductive assurance: self-fertilization and clonal propagation. Next, using genome-wide single nucleotide polymorphism (SNP) data, we identified three distinct genetic clusters structured by longitude and estimated geographic coordinates of the most likely origins of range expansion within each cluster. We found that both measures of reproductive assurance significantly increased on average with distance from the inferred biogeographic origin, which is consistent with the hypothesis that reproductive assurance undergoes adaptive evolution during range expansion. This study supports hypotheses underlying Bakers Law and contributes to our understanding of spatial variation in reproductive assurance, which is linked to variation in evolutionary potential, adaptability, and the long-term persistence of populations across large spatial scales. Lay summaryWhat generates and maintains the amazing diversity in plant reproduction we see today? Traditionally, studies have focused on the role of contemporary ecology, such as pollinator or mate availability, in driving spatial patterns within species, however, historical drivers may be an understudied alternative explanation. Here, we test the hypothesis that expansion into new habitats after glacial retreat, where pollinators or mates were scarce, favors plants with the ability to reproduce in the absence of pollinators and mates by making self-pollinated seeds or vegetative clones of themselves. We find support for the hypothesis, where the probabilities of making both autonomously selfed seed and clonal vegetative propagules increase on average along inferred pathways of range expansion. Our study joins a handful of previous studies that tested and provided support for historical range expansion shaping range-wide spatial variation in reproductive assurance in plants, suggesting post-glacial range expansion may be a common mechanism creating diversity in plant mating systems.

evolutionary biology↗

bioRxiv2024

An alpine plant shows no decrease in genetic diversity associated with rapid post-glacial range expansion

While range expansion is hypothesized to be a mechanism for species persistence under climate change, many eco-evolutionary models describe demographic and genetic processes during range expansion that may decrease genetic variation and increase genetic load at the leading edge (i.e., expansion load). These predictions are related to dispersal limitation at the leading edge driving colonization dynamics, a scenario common in post-glacial range expansion at the continental scale ([~]20,000 years ago). However, post-glacial range expansion can also occur on contemporary time scales, such as alpine glacier recession following the end of The Little Ice Age ([~]150 years ago) and our understanding of dispersal limitation structuring these instances of rapid range expansion are relatively understudied. Here, we test whether there is evidence supporting the role of dispersal limitation during range expansion following alpine glacier retreat using the native alpine plant Erythranthe (Mimulus) lewisii by examining patterns of neutral genetic diversity (single nucleotide polymorphisms) across the history of glacier recession (i.e., glacier chronosequence) across two glacier forelands in Garibaldi Provincial Park, BC. We find weak support for the prediction of increasing clines in genetic differentiation towards the range edge, and no support for decreasing clines in genetic diversity, suggesting dispersal limitation is not characterizing colonization during range expansion, with the implication that the accumulation of expansion load at the range edge is likely not applicable on these spatiotemporal scales. Together, our results suggest that loss of genetic diversity for range-shifting species in the alpine is likely not a key contributing factor to any decreased fitness over time.

evolutionary biology↗

bioRxiv2024

Evolutionary rescue during extreme drought

Populations declining due to climate change may need to evolve to persist. While evolutionary rescue has been demonstrated in theory and the lab, its relevance to natural populations facing climate change remains unknown. Here we link rapid evolution and population dynamics in scarlet monkeyflower, Mimulus cardinalis, during an exceptional drought. We leverage whole-genome sequencing across 55 populations to identify climate-associated loci. Simultaneously we track demography and allele frequency change throughout the drought. We establish range-wide population decline during the drought, geographically variable rapid evolution, and variable population recovery that is predictable by standing genetic variation in and rapid evolution at climate-associated loci. These findings demonstrate evolutionary rescue in the wild, showing that genetic variation at adaptive, but not neutral loci, predicts population recovery.

evolutionary biology↗

bioRxiv2023

Temperature-dependence and genetic variation in resource acquisition strategies in a model freshwater plant

O_LIUnderstanding how competition varies with environmental stress is critical to anticipating species and community responses to rapid environmental change. While the stress-gradient hypothesis predicts the strength of competition to decrease with increasing stress, our understanding of how competition varies with stress is limited by a lack of mechanistic understanding of how resource-use traits underlying competitive dynamics respond to stress. C_LIO_LIHere, we use duckweeds in the Lemna species complex to measure how phenotypic and genetic variation in R* (a resource acquisition trait representing the minimum resource requirement for positive population growth) varies with high-temperature stress to better understand how stress alters competitive ability for essential resources. C_LIO_LIWe found that heat stress increased the R* of Lemna plants for nitrogen acquisition. Because lower R* values predict dominance in competitive dynamics where resources are limiting, this indicates that under stressful, high temperatures, plants could experience increased sensitivity to competition due to the higher resources required to sustain positive population growth rates. C_LIO_LIWe found minimal genetic variation in R* across 11 local genotypes within the Lemna species complex, indicating that selection on resource acquisition strategies for essential resources such as nitrogen may be constrained in nature. The expression of genetic variation in R* for nitrogen was further reduced under heat stress, suggesting that the response to selection for R* could be particularly constrained under high-temperature stress. C_LIO_LIContrary to predictions drawn from the gleaner-opportunist trade-off, we did not find evidence for a trade-off in resource acquisition strategies under benign conditions or high-temperature stress. Plants with lower R* (i.e., higher growth rates under lower nitrogen levels) were not constrained to have lower growth rates under higher nitrogen levels, possibly because the chosen genotypes have not diverged across resource acquisition strategies or because Lemna spp. has escaped this constraint. C_LIO_LIImportantly, our work outlines that high-temperature stress could increase sensitivity to competition through increased requirement for resources while reducing the evolutionary potential for Lemna species to respond to selection for resource traits. This study acts as a key step to understanding the mechanistic traits behind competitive dynamics in resource-limited and stressful environments. C_LI

ecology↗

bioRxiv2023

Lagged climate-driven range shifts at species' leading, but not trailing, range edges revealed by multispecies seed addition experiment

Climate change is causing many species ranges to shift upslope to higher elevations as species track their climatic requirements. However, many species have not shifted in pace with recent warming (i.e., range stasis), possibly due either to demographic lags or microclimatic buffering. The lagged-response hypothesis posits that range stasis disguises an underlying climatic sensitivity if range shifts lag the velocity of climate change due to slow colonization or mortality. Alternatively, the microclimatic buffering hypothesis proposes that small-scale variation within the landscape, such as canopy cover, creates patches of suitable habitat within otherwise unsuitable macroclimates that create climate refugia and buffer range contractions. To test these two hypotheses, we combined a large seed addition experiment of 25 plant species across macro- and micro-scale climate gradients with local herbaria records to compare patterns of seedling recruitment relative to adult ranges and microclimate in the North Cascades, USA. Despite high species-to-species variability in recruitment, community-level patterns supported the lagged response hypothesis, with a mismatch between where recruitment vs. adults occur. On average, the seedling recruitment optimum shifted from the adult climatic range centre to historically cooler, wetter regions and many species recruited beyond their cold (e.g., leading) range edge. Meanwhile, successful recruitment at warm and dry edges, despite recent climate change, suggests that macroclimatic effects on recruitment do not drive trailing range dynamics. By contrast, we were unable to detect evidence of microclimatic buffering due to canopy cover. Combined, our results suggest apparent range stasis in our system is a lagged response to climate change at the cool ends of species ranges, with range expansions likely to occur slowly or in a punctuated fashion.

ecology↗

bioRxiv2023

Range expansion is both slower and less predictable across a spatial gradient in temperature

Rapid evolution in colonizing populations can alter our ability to predict future range expansions. Recent theory suggests that the dynamics of replicate range expansions are less variable, and hence more predictable, with increased selection at the expanding range front. Here, we test whether selection from environmental gradients across space produces more consistent range expansion speeds, using the experimental evolution of replicate duckweed populations colonizing landscapes with and without a temperature gradient. We found that range expansion across a temperature gradient was slower on average, with range-front populations displaying higher population densities, and genetic signatures and trait changes consistent with directional selection. Despite this, we found that with a spatial gradient range expansion speed became more variable and less consistent among replicates over time. Our results therefore challenge current theory, highlighting that chance can still shape the genetic response to selection to influence our ability to predict range expansion speeds.

ecology↗

bioRxiv2023

Phenotypic lags influence rapid evolution throughout a drought cycle

Climate anomalies pose strong selection which can lead to rapid evolution. These global mean trends occur on a backdrop of interannual variability that might weaken or even reverse selection. However, the impact of climatic interannual variability on rapid evolution is rarely considered. We study evolution through a seven-year period encompassing a severe drought across 12 populations of Mimulus cardinalis (scarlet monkeyflower). Plants were grown in a common greenhouse environment under wet and dry treatments, where specific leaf area and date of flowering were measured. We compare the ability of different climate metrics to explain the rapid evolution of trait values, examining different time-periods, including the collection year, prior years, and cumulative metrics across sequential years. We find that anomalies in mean annual precipitation best describe rapid evolution over our study period. Past climates, of one-to two-years ago, are often related to trait values in a conflicting direction to collection-year climate. Uncovering these complex climatic impacts on evolution is critical to better predict and interpret the impacts of climate change.

evolutionary biology↗

bioRxiv2022

Density-dependent selection during range expansion affects expansion load in life-history traits

Models of range expansion have independently explored fitness consequences of life-history trait evolution and increased rates of genetic drift--or "allele surfing"--during spatial spread, but no previous model has examined the interactions between these two processes. Here, we explore an ecologically complex range expansion scenario that combines density-dependent selection with allele surfing, using spatially explicit simulations to asses the genetic and fitness consequences of density-dependent selection on the evolution of life-history traits. We demonstrate that density-dependent selection on the range edge acts differently depending on the life-history trait and can either diminish or enhance allele surfing. Specifically, we show that selection on the range edge is always weaker at sites affecting competitive ability (K-selected traits) than intrinsic growth rate ((r-selected traits). We then link differences in the frequency of deleterious mutations to differences in the efficacy of selection and rate of mutation accumulation across distinct life-history traits. Finally, we demonstrate the fitness consequences of accumulated deleterious mutations for different life-history traits are related to the population density in which they are expressed. Our work highlights the complex relationship between ecology and expressed genetic load, which will be important to consider when interpreting both experimental and field studies of range expansion.

evolutionary biology↗

bioRxiv2021

Selection on early survival does not explain germination rate clines in Mimulus cardinalis (Phrymaceae)

PremiseMany traits covary with environmental gradients to form phenotypic clines. While local adaptation to the environment can generate phenotypic clines, other nonadaptive processes may also. If local adaptation causes phenotypic clines, then the direction of genotypic selection on traits should shift from one end of the cline to the other. Traditionally genotypic selection on non-Gaussian traits like germination rate have been hampered because it is challenging to measure their genetic variance. MethodsHere we used quantitative genetics and reciprocal transplants to test whether a previously discovered cline in germination rate showed additional signatures of adaptation in the scarlet monkeyflower (Mimulus cardinalis). We measured genotypic and population level covariation between germination rate and early survival, a component of fitness. We developed a novel discrete log-normal model to estimate genetic variance in germination rate. ResultsContrary to our adaptive hypothesis, we found no evidence that genetic variation in germination rate contributed to variation in early survival. Across populations, southern populations in both gardens germinated earlier and survived more. ConclusionsSouthern populations have higher early survival but this is not caused by faster germination. This pattern is consistent with nonadaptive forces driving the phenotypic cline in germination rate, but future work will need to assess whether there is selection at other life stages. This statistical framework should help expand quantitative genetic analyses for other waiting-time traits.

evolutionary biology↗

bioRxiv2020

Climate warming weakens local adaptation

Anthropogenic climate change is generating mismatches between the environmental conditions that populations historically experienced and those in which they reside. Understanding how climate change affects population performance is a critical scientific challenge. We combine a quantitative synthesis of field transplant experiments with a novel statistical approach based in evolutionary theory to quantify the effects of temperature and precipitation variability on population performance. We find that species average performance is affected by both temperature and precipitation, but populations show signs of local adaptation to temperature only. Contemporary responses to temperature are strongly shaped by the local climates under which populations evolved, resulting in performance declines when temperatures deviate from historic conditions. Adaptation to other local environmental factors is strong, but temperature deviations as small as 2{degrees}C erode the advantage that these non-climatic adaptations historically gave populations in their home sites. One sentence summaryClimate change is pulling the thermal rug out from under populations, reducing average performance and eroding their historical home-site advantage.

evolutionary biology↗

bioRxiv2020

Expansion dynamics and marginal climates drive adaptation across geographic ranges

Every species experiences limits to its geographic distribution. Some evolutionary models predict that populations at range edges are less well-adapted to their local environments due to drift, expansion load, or swamping gene flow from the range interior. Alternatively, populations near range edges might be uniquely adapted to marginal environments. In this study, we use a database of transplant studies that quantify performance at broad geographic scales to test how local adaptation, site quality, and population quality change from spatial and climatic range centers towards edges. We find that populations from poleward edges perform relatively poorly, both on average across all sites (15% lower population quality) and when compared to other populations at home (31% relative fitness disadvantage), consistent with these populations harboring high genetic load. Populations from equatorial edges also perform poorly on average (18% lower population quality) but, in contrast, outperform foreign populations (16% relative fitness advantage), suggesting that populations from equatorial edges have strongly adapted to unique environments. Finally, we find that populations from sites that are thermally extreme relative to the species niche demonstrate strong local adaptation, regardless of their geographic position. Our findings indicate that both nonadaptive processes and adaptive evolution contribute to variation in adaptation across species ranges.

evolutionary biology↗

bioRxiv2020

Quantitative trait locus mapping reveals an independent genetic basis for joint divergence in leaf function, life-history, and floral traits between scarlet monkeyflower (Mimulus cardinalis) populations

PREMISEAcross taxa, vegetative and floral traits that vary along a fast-slow life-history axis are often correlated with leaf functional traits arrayed along the leaf economics spectrum, suggesting a constrained set of adaptive trait combinations. Such broad-scale convergence may arise from genetic constraints imposed by pleiotropy (or tight linkage) within species, or from natural selection alone. Understanding the genetic basis of trait syndromes and their components is key to distinguishing these alternatives and predicting evolution in novel environments. METHODSWe used a line-cross approach and quantitative trait locus (QTL) mapping to characterize the genetic basis of twenty leaf functional/physiological, life history, and floral traits in hybrids between annualized and perennial populations of scarlet monkeyflower (Mimulus cardinalis). RESULTSWe mapped both single and multi-trait QTLs for life history, leaf function and reproductive traits, but found no evidence of genetic co-ordination across categories. A major QTL for three leaf functional traits (thickness, photosynthetic rate, and stomatal resistance) suggests that a simple shift in leaf anatomy may be key to adaptation to seasonally dry habitats. CONCLUSIONSOur results suggest that the co-ordination of resource-acquisitive leaf physiological traits with a fast life history and more selfing mating system results from environmental selection rather than functional or genetic constraint. Independent assortment of distinct trait modules, as well as a simple genetic basis to leaf physiological traits associated with drought escape, may facilitate adaptation to changing climates.

plant biology↗

bioRxiv2018

Genetic differentiation is determined by geographic distance in Clarkia pulchella

Both environmental differences and geographic distances may contribute to the genetic differentiation of populations on the landscape. Understanding the relative importance of these drivers is of particular interest in the context of geographic range limits, as both swamping gene flow and lack of genetic diversity are hypothesized causes of range limits. We investigated the landscape genetic structure of 32 populations of the annual wildflower Clarkia pulchella from across the species geographic range in the interior Pacific North-west. We tested whether climatic differences between populations influenced the magnitude of their genetic differentiation. We also investigated patterns of population structure and geographic gradients in genetic diversity. Contrary to our expectations, we found an increase in genetic diversity near the species northern range edge. We found no notable contribution of climatic differences to genetic differentiation, indicating that any processes that might operate to differentiate populations based on temperature or precipitation are not affecting the putatively neutral loci in these analyses. Rather, these results support seed and pollen movement at limited distances relative to the species range and that this movement and the subsequent incorporation of immigrants into the local gene pool are not influenced by temperature or precipitation similarities among populations. We found that populations in the northern and southern parts of the range tended to belong to distinct genetic groups and that central and eastern populations were admixed between these two groups. This pattern could be the result of a past or current geographic barrier associated with the Columbia Plateau, or it could be the result of spread from separate sets of refugia after the last glacial maximum.

evolutionary biology↗

bioRxiv2017

Demographic compensation does not rescue populations at a trailing range edge

As climate change shifts species' climatic envelopes across the landscape, equilibrium between geographic ranges and niches is likely diminishing due to time lags in demography and dispersal. If a species' range and niche are out of equilibrium, then population performance should decrease from cool, \"leading\" range edges, where populations are expanding into recently ameliorated habitats, to warm, \"trailing\" range edges, where populations are contracting from newly unsuitable areas. Population contraction signals that compensatory changes in vital rates are insufficient to buffer population growth from deteriorating environments. Life history theory predicts tradeoffs between fast development, high reproduction, and short longevity at low latitudes and slow development, less frequent but multiple bouts of reproduction, and long lifespan at high latitudes. If demographic compensation is driven by life history evolution, compensatory negative correlations in vital rates may be associated with this fast-slow continuum. An outstanding question is whether range limits and range contractions reflect inadequate compensatory life history shifts along environmental gradients, causing population growth rates to fall below replacement levels at range edges. We surveyed demography of 32 populations of the scarlet monkeyflower (Erythranthe cardinalis) spanning 11{degrees} latitude in western North America and used integral projection models to infer population dynamics and assess demographic compensation. Population growth rates decreased from north to south, consistent with leading-trailing dynamics. Southern populations are declining due to reduced survival, growth, and recruitment, despite compensatory increases in reproduction and faster life history characteristics, suggesting that demographic compensation will not rescue populations at the trailing range edge.\n\nSIGNIFICANCE STATEMENTWhile climate change is causing poleward shifts in many species' geographic distributions, some species' ranges have remained stable, particularly at low-latitude limits. One explanation for why some species' ranges have not shifted is demographic compensation, whereby declines in some demographic processes are offset by increases in others, potentially buffering populations from extinction. However, we have limited understanding of whether demographic compensation can prevent collapse of populations facing climate change. We examined the demography of natural populations of a perennial herb spanning a broad latitudinal gradient. Despite increases in reproduction, low-latitude populations declined due to diminished survival, growth, and recruitment. Thus, demographic compensation may not be sufficient to rescue low-latitude, warm-edge populations from extinction.

ecology↗

bioRxiv2016

Grow with the flow: a latitudinal cline in physiology is associated with more variable precipitation in Mimulus cardinalis

Local adaptation is commonly observed in nature: organisms perform well in their natal environment, but poorly outside it. Correlations between traits and latitude, or latitudinal clines, are among the most common pieces of evidence for local adaptation, but identifying the traits under selection and the selective agents is challenging. Here, we investigated a latitudinal cline in growth and photosynthesis across 16 populations of the perennial herb Erythranthe cardinalis (Phrymaceae). Using machine learning methods, we identify interannual variation in precipitation as a likely selective agent: Southern populations from more variable environments had higher photosynthetic rates and grew faster. We hypothesize that selection may favor a more annualized life history - grow now rather than save for next year - in environments where severe droughts occur more often. Thus our study provides insight into how species may adapt if Mediterranean climates become more variable due to climate change.

evolutionary biology↗