Development Of Phenotype Research Articles

Advances in genome sequencing reveal changes in gene content that contribute to arthropod macroevolution.

Current sequencing technology allows for the relatively affordable generation of highly contiguous genomes. Technological advances have made it possible for researchers to investigate the consequences of diverse sorts of genomic variants, such as gene gain and loss. With the extraordinary number of high-quality genomes now available, we take stock of how these genomic variants impact phenotypic evolution. We take care to point out that the identification of genomic variants of interest is only the first step in understanding their impact. Painstaking lab or fieldwork is still required to establish causal relationships between genomic variants and phenotypic evolution. We focus mostly on arthropod research, as this phylum has an impressive degree of phenotypic diversity and is also the subject of much evolutionary genetics research. This article is intended to both highlight recent advances in the field and also to be a primer for learning about evolutionary genetics and genomics.

A nematode model to evaluate microdeletion phenotype expression.

Microdeletion syndromes are genetic diseases caused by multilocus chromosomal deletions too small to be detected by karyotyping. They are typified by complex pleiotropic developmental phenotypes that depend both on the extent of the deletion and variations in genetic background. Microdeletion alleles cause a wide array of consequences involving multiple pathways. How simultaneous haploinsufficiency of numerous adjacent genes leads to complex and variable pleiotropic phenotypes is not well understood. CRISPR/Cas9 genome editing has been shown to induce microdeletion-like alleles at a meaningful rate. Here, we describe a microdeletion allele in Caenorhabditis elegans recovered during a CRISPR/Cas9 genome editing experiment. We mapped the allele to chromosome V, balanced it with a reciprocal translocation crossover suppressor, and precisely defined the breakpoint junction. The allele simultaneously removes 32 protein-coding genes, yet animals homozygous for this mutation are viable as adults. Homozygous animals display a complex phenotype including maternal effect lethality, producing polynucleated embryos that grow into uterine tumors, vulva morphogenesis defects, body wall distensions, uncoordinated movement, and a shortened life span typified by death by bursting. Our work provides an opportunity to explore the complexity and penetrance of microdeletion phenotypes in a simple genetic model system.

Diadromy Drives Elevated Rates of Trait Evolution and Ecomorphological Convergence in Clupeiformes (Herring, Shad, and Anchovies).

AbstractMigration can have a profound influence on rates and patterns of phenotypic evolution. Diadromy is the migration between marine and freshwater habitats for feeding and reproduction that can require individuals to travel tens to thousands of kilometers. The high energetic demands of diadromy are predicted to select for ecomorphological traits that maximize swimming and locomotor efficiency. Intraspecific studies have shown repeated instances of divergence among diadromous and nondiadromous populations in locomotor and foraging traits, which suggests that at a macroevolutionary scale diadromous lineages may experience convergent evolution onto one or multiple adaptive optima. We tested for differences in rates and patterns of phenotypic evolution among diadromous and nondiadromous lineages in Clupeiformes, a clade that has evolved diadromy more than 10 times. Our results show that diadromous clupeiforms show convergent evolution for some locomotor traits and faster rates of evolution, which we propose are adaptive responses to the locomotor demands of migration. We also find evidence that diadromous lineages show convergence into multiple regions of multivariate trait space and suggest that these respective trait spaces are associated with differences in migration and trophic ecology. However, not all locomotor traits and no trophic traits show evidence of convergence or elevated rates of evolution associated with diadromy. Our results show that long-distance migration influences the tempo and patterns of phenotypic evolution at macroevolutionary scales, but there is not a single diadromous syndrome.

Exosome complex components 1 and 2 are vital for early mammalian development

Exosome Complex Components 1 and 2 (EXOSC1 and 2) are two proteins in the RNA Exosome complex whose main function is 5’ → 3’ RNA degradation and processing. The RNA exosome complex is comprised of nine subunits that form two separate components: the S1/KH cap and the PH-core. EXOSC1 and 2 are both part of the S1/KH cap and are involved in binding nascent RNA. As part of a systemic characterization of early lethal alleles produced by the Knockout Mouse Project, we have examined Exosc1 and Exosc2 homozygous null (mutant) embryos to determine developmental and molecular phenotypes of embryos lacking their functions. Our studies reveal that Exosc1 null embryos implant and form an egg cylinder but are developmentally delayed and fail to initiate gastrulation by embryonic day 7.5. In contrast, Exosc2 null embryos are lethal during peri-implantation stages, and while they do form a morphologically normal blastocyst at E3.5, they cannot be recovered at post-implantation stages. We show the absence of stage-specific developmental and altered lineage-specification in both Exosc1 and Exosc2 mutant embryos and conclude that these genes are essential for the successful progression through early mammalian development.

The genomics and evolution of inter-sexual mimicry and female-limited polymorphisms in damselflies

Sex-limited morphs can provide profound insights into the evolution and genomic architecture of complex phenotypes. Inter-sexual mimicry is one particular type of sex-limited polymorphism in which a novel morph resembles the opposite sex. While inter-sexual mimics are known in both sexes and a diverse range of animals, their evolutionary origin is poorly understood. Here, we investigated the genomic basis of female-limited morphs and male mimicry in the common bluetail damselfly. Differential gene expression between morphs has been documented in damselflies, but no causal locus has been previously identified. We found that male mimicry originated in an ancestrally sexually dimorphic lineage in association with multiple structural changes, probably driven by transposable element activity. These changes resulted in ~900 kb of novel genomic content that is partly shared by male mimics in a close relative, indicating that male mimicry is a trans-species polymorphism. More recently, a third morph originated following the translocation of part of the male-mimicry sequence into a genomic position ~3.5 mb apart. We provide evidence of balancing selection maintaining male mimicry, in line with previous field population studies. Our results underscore how structural variants affecting a handful of potentially regulatory genes and morph-specific genes can give rise to novel and complex phenotypic polymorphisms.

Examining the neurodevelopmental and motor phenotypes of Bohring-Opitz syndrome (ASXL1) and Bainbridge-Ropers syndrome (ASXL3).

Chromatin Modifying Disorders (CMD) have emerged as one of the most rapidly expanding genetic disorders associated with autism spectrum disorders (ASD). Motor impairments are also prevalent in CMD and may play a role in the neurodevelopmental phenotype. Evidence indicates that neurodevelopmental outcomes in CMD may be treatable postnatally; thus deep phenotyping of these conditions can improve clinical screening while improving the development of treatment targets for pharmacology and for clinical trials. Here, we present developmental phenotyping data on individuals with Bohring-Optiz Syndrome (BOS - ASXL1) and Bainbridge-Ropers Syndrome (BRS - ASXL3) related disorders, two CMDs highly penetrant for motor and developmental delays. To phenotype the motor and neurodevelopmental profile of individuals with ASXL1 and ASXL3 related disorders (BOS and BRS). To provide a preliminary report on the association of motor impairments and ASD. Neurodevelopmental and motor phenotyping was conducted on eight individuals with pathogenic ASXL1 variants and seven individuals with pathogenic ASXL3 variants, including medical and developmental background intake, movement and development questionnaires, neurological examination, and quantitative gait analysis. Average age of first developmental concerns was 4 months for individuals with BOS and 9 months in BRS. 100% of individuals who underwent the development questionnaire met a diagnosis of developmental coordination disorder. 71% of children with BOS and 0% of children with BRS noted movement difficulty greatly affected classroom learning. Participants with BRS and presumed diagnoses of ASD were reported to have more severe motor impairments in recreational activities compared to those without ASD. This was not the case for the individuals with BOS. Motor impairments are prevalent and pervasive across the ASXL disorders with and without ASD, and these impairments negatively impact engagement in school-based activities. Unique neurodevelopmental and motor findings in our data include a mixed presentation of hypo and hypertonia in individuals with BOS across a lifespan. Individuals with BRS exhibited hypotonia and greater variability in motor skills. This deep phenotyping can aid in appropriate clinical diagnosis, referral to interventions, and serve as meaningful treatment targets in clinical trials.

A geometric approach to the evolution of altruism

Fisher’s geometric model provides a powerful tool for making predictions about key properties of Darwinian adaptation. Here, I apply the geometric model to predict differences between the evolution of altruistic versus nonsocial phenotypes. I recover Kimura’s prediction that probability of fixation is greater for mutations of intermediate size, but I find that the effect size that maximises probability of fixation is relatively small in the context of altruism and relatively large in the context of nonsocial phenotypes, and that the overall probability of fixation is lower for altruism and is higher for nonsocial phenotypes. Accordingly, the first selective substitution is expected to be smaller, and to take longer, in the context of the evolution of altruism. These results strengthen the justification for employing streamlined social evolutionary methodologies that assume adaptations are underpinned by many genes of small effect.

Evolution of the Spider Homeobox Gene Repertoire by Tandem and Whole Genome Duplication.

Gene duplication generates new genetic material that can contribute to the evolution of gene regulatory networks and phenotypes. Duplicated genes can undergo subfunctionalization to partition ancestral functions and/or neofunctionalization to assume a new function. We previously found there had been a whole genome duplication (WGD) in an ancestor of arachnopulmonates, the lineage including spiders and scorpions but excluding other arachnids like mites, ticks, and harvestmen. This WGD was evidenced by many duplicated homeobox genes, including two Hox clusters, in spiders. However, it was unclear which homeobox paralogues originated by WGD versus smaller-scale events such as tandem duplications. Understanding this is a key to determining the contribution of the WGD to arachnopulmonate genome evolution. Here we characterized the distribution of duplicated homeobox genes across eight chromosome-level spider genomes. We found that most duplicated homeobox genes in spiders are consistent with an origin by WGD. We also found two copies of conserved homeobox gene clusters, including the Hox, NK, HRO, Irx, and SINE clusters, in all eight species. Consistently, we observed one copy of each cluster was degenerated in terms of gene content and organization while the other remained more intact. Focussing on the NK cluster, we found evidence for regulatory subfunctionalization between the duplicated NK genes in the spider Parasteatoda tepidariorum compared to their single-copy orthologues in the harvestman Phalangium opilio. Our study provides new insights into the relative contributions of multiple modes of duplication to the homeobox gene repertoire during the evolution of spiders and the function of NK genes.

Plant morpho evo-devo.

Evo-devo is often thought of as being the study of which genes underlie which phenotypes. However, evo-devo is much more than this, especially in plant science. In leaf scars along stems, cell changes across wood growth rings, or flowers along inflorescences, plants trace a record of their own development. Plant morpho evo-devo provides data that genes could never furnish on themes such as heterochrony, the evolution of temporal phenotypes, modularity, and phenotype-first evolution. As plant science surges into increasingly -omic realms, it is essential to keep plant morpho evo-devo in full view as an honored member of the evo-devo canon, ensuring that plant scientists can, wherever they are, generate fundamental insights at the appropriate level of biological organization.

Exposing the error hidden in plain sight: A critique of Calder's (1983) group selectionist seed-dispersal hypothesis for mistletoe "mimicry" of host plants.

Some mistletoe species (Loranthaceae) resemble their host plants to a striking degree. Various mechanisms have been proposed for the developmental origins of novel traits that cause mistletoes to appear similar to their hosts, as well as for the adaptive phenotypic evolution of such traits. Calder (1983) proposed a logically flawed group selectionist seed-dispersal hypothesis for mistletoes to resemble their hosts. Calder's (1983) hypothesis does not provide a viable potential explanation for mistletoe resemblance to hosts.

TOR coordinates cytokinin and gibberellin signals mediating development and defense.

Plants constantly perceive and process environmental signals and balance between the energetic demands of growth and defense. Growth arrest upon pathogen attack was previously suggested to result from a redirection of the plants' metabolic resources towards the activation of plant defense. The energy sensor Target of Rapamycin (TOR) kinase is a conserved master coordinator of growth and development in all eukaryotes. Although TOR is positioned at the interface between development and defense, little is known about the mechanisms by which TOR may potentially regulate the relationship between these two modalities. The plant hormones cytokinin (CK) and gibberellin (GA) execute various aspects of plant development and defense. The ratio between CK and GA was reported to determine the outcome of developmental programmes. Here, investigating the interplay between TOR-mediated development and TOR-mediated defense in tomato, we found that TOR silencing resulted in rescue of several different aberrant developmental phenotypes, demonstrating that TOR is required for the execution of developmental cues. In parallel, TOR inhibition enhanced immunity in genotypes with a low CK/GA ratio but not in genotypes with a high CK/GA ratio. TOR-inhibition mediated disease resistance was found to depend on developmental status, and was abolished in strongly morphogenetic leaves, while being strongest in mature, differentiated leaves. CK repressed TOR activity, suggesting that CK-mediated immunity may rely on TOR downregulation. At the same time, TOR activity was promoted by GA, and TOR silencing reduced GA sensitivity, indicating that GA signalling requires normal TOR activity. Our results demonstrate that TOR likely acts in concert with CK and GA signalling, executing signalling cues in both defense and development. Thus, differential regulation of TOR or TOR-mediated processes could regulate the required outcome of development-defense prioritisation.

In ovo feeding of probiotic lactobacilli differentially alters expression of genes involved in the development and immunological maturation of bursa of Fabricius in pre-hatched chicks

Compelling evidence indicates that immunological maturation of the gut-associated lymphoid tissues, including the bursa of Fabricius, is dependent upon antigenic stimulation post-hatch. In view of these data, the present study investigated the impact of exposing the immune system of chick embryos to antigenic stimuli, via in ovo delivery of poultry-specific lactobacilli, on the expression of genes associated with early bursal development and maturation. Broiler line embryonated eggs were inoculated with 106 and 107 colony-forming units (CFUs) of an individual or a mixture of Lactobacillus species, including L. crispatus (C25), L. animalis (P38), L. acidophilus (P42), and L. reuteri (P43), at embryonic day 18 (ED18). The bursa of Fabricius was collected from pre-hatched chicks (ED20) to measure the expression levels of various immune system genes. The results revealed that L. acidophilus and the mixture of Lactobacillus species at the dose of 106 CFU consistently elicited higher expression of genes responsible for B cell development, differentiation, and survival (B cell activating factor (BAFF), BAFF-receptor (BAFF-R)), and antibody production (interleukin (IL)-10) and diversification (TGF-β). Similar expression patterns were also noted in T helper (Th) cell-associated cytokine genes, including Th1-type cytokines (interferon (IFN)-γ and IL-12p40), Th2-type cytokines (IL-4 and IL-13) and Th17 cytokine (IL-17). Overall, these results suggest that the supplementation of poultry-specific lactobacilli to chick embryos might be beneficial for accelerating the development and immunological maturation of the bursa of Fabricius. However, further studies are required to determine if the changes in gene expression are associated with the developmental trajectory and phenotypes of bursal cells.

Genomic signatures of convergent shifts to plunge-diving behavior in birds

Understanding the genetic basis of convergence at broad phylogenetic scales remains a key challenge in biology. Kingfishers (Aves: Alcedinidae) are a cosmopolitan avian radiation with diverse colors, diets, and feeding behaviors—including the archetypal plunge-dive into water. Given the sensory and locomotor challenges associated with air-water transitions, kingfishers offer a powerful opportunity to explore the effects of convergent behaviors on the evolution of genomes and phenotypes, as well as direct comparisons between continental and island lineages. Here, we use whole-genome sequencing of 30 diverse kingfisher species to identify the genomic signatures associated with convergent feeding behaviors. We show that species with smaller ranges (i.e., on islands) have experienced stronger demographic fluctuations than those on continents, and that these differences have influenced the dynamics of molecular evolution. Comparative genomic analyses reveal positive selection and genomic convergence in brain and dietary genes in plunge-divers. These findings enhance our understanding of the connections between genotype and phenotype in a diverse avian radiation.

A collaborative backbone resource for comparative studies of subterranean evolution: The World Asellidae database.

Transition to novel environments, such as groundwater colonization by surface organisms, provides an excellent research ground to study phenotypic evolution. However, interspecific comparative studies on evolution to groundwater life are few because of the challenge in assembling large ecological and molecular resources for species-rich taxa comprised of surface and subterranean species. Here, we make available to the scientific community an operational set of working tools and resources for the Asellidae, a family of freshwater isopods containing hundreds of surface and subterranean species. First, we release the World Asellidae database (WAD) and its web application, a sustainable and FAIR solution to producing and sharing data and biological material. WAD provides access to thousands of species occurrences, specimens, DNA extracts and DNA sequences with rich metadata ensuring full scientific traceability. Second, we perform a large-scale dated phylogenetic reconstruction of Asellidae to support phylogenetic comparative analyses. Of 424 terminal branches, we identify 34 pairs of surface and subterranean species representing independent replicates of the transition from surface water to groundwater. Third, we exemplify the usefulness of WAD for documenting phenotypic shifts associated with colonization of subterranean habitats. We provide the first phylogenetically controlled evidence that body size of males decreases relative to that of females upon groundwater colonization, suggesting competition for rare receptive females selects for smaller, more agile males in groundwater. By making these tools and resources widely accessible, we open up new opportunities for exploring how phenotypic traits evolve in response to changes in selective pressures and trade-offs during groundwater colonization.

MicroRNA-218 instructs proper assembly of hippocampal networks.

The assembly of the mammalian brain is orchestrated by temporally coordinated waves of gene expression. Post-transcriptional regulation by microRNAs (miRNAs) is a key aspect of this program. Indeed, deletion of neuron-enriched miRNAs induces strong developmental phenotypes, and miRNA levels are altered in patients with neurodevelopmental disorders. However, the mechanisms used by miRNAs to instruct brain development remain largely unexplored. Here, we identified miR-218 as a critical regulator of hippocampal assembly. MiR-218 is highly expressed in the hippocampus and enriched in both excitatory principal neurons (PNs) and GABAergic inhibitory interneurons (INs). Early life inhibition of miR-218 results in an adult brain with a predisposition to seizures. Changes in gene expression in the absence of miR-218 suggest that network assembly is impaired. Indeed, we find that miR-218 inhibition results in the disruption of early depolarizing GABAergic signaling, structural defects in dendritic spines, and altered intrinsic membrane excitability. Conditional knockout of Mir218-2 in INs, but not PNs, is sufficient to recapitulate long-term instability. Finally, de-repressing Kif21b and Syt13, two miR-218 targets, phenocopies the effects on early synchronous network activity induced by miR-218 inhibition. Taken together, the data suggest that miR-218 orchestrates formative events in PNs and INs to produce stable networks.

The impact of genetic background during laboratory evolution of Pseudomonas aeruginosa in a cystic fibrosis-like environment.

Genetic background has the potential to influence both the tempo and trajectory of adaptive change: Different genotypes of a given species may adopt varied solutions to the same environmental challenge, or they may approach the same solution at different rates. Laboratory selection has been widely used to experimentally examine the evolutionary consequences of variation in genetic background, although largely using genotypes differing by only a few mutations. Here, we leverage natural variation in the bacterium Pseudomonas aeruginosa to investigate whether different adaptive solutions are accessible from distant points of departure on an adaptive landscape. We evolved 17 diverse genotypes in a laboratory medium that partially mimics the lung sputum of cystic fibrosis patients, and we measured changes in 10 phenotypes as well as in fitness. Using phylogenetically informed analyses, we found that genetic background impacted the tempo, but not the trajectory, of phenotypic evolution: Different starting genotypes converged toward similar phenotypes, but at varying rates. Our findings add to a growing body of evidence supporting widespread diminishing return epistasis during adaptation. The importance of genetic background toward the trajectory of adaptation remains inconsistent across experimental systems and conditions.

Evolutionary transition from surface to subterranean living in Australian water beetles (Coleoptera: Dytiscidae) through adaptive and relaxed selection

Abstract Over the last 5 million years, numerous species of Australian stygobiotic (subterranean and aquatic) beetles have evolved underground following independent colonization of aquifers by surface ancestors, providing a set of repeated evolutionary transitions from surface to subterranean life. We used this system as an ‘evolutionary experiment’ to investigate whether relaxed selection has provided a source of variability for adaptive radiations into ecosystems containing open niches and whether this variability underpins phenotypic evolution in cave animals. Linear and landmark-based measurements were used to quantify the morphology of subterranean species from different aquifers, compared to interstitial and closely related aquatic surface species. Subterranean dytiscids were observed to be morphologically distinct, suggesting they have a different lifestyle compared to their surface relatives. However, variation in the measured traits was much greater in the subterranean species, and unstructured, showing no evidence of clustering that would indicate adaptation to specific niches. Furthermore, a previously identified pattern of repeated nonoverlapping size variation in beetles across aquifers was not correlated with repeated body shape evolution. The observed variability across body shape and limb traits provides support for the hypothesis that relaxed selection and neutral evolution underlie the phenotypic evolution in these species.

Introgression Underlies Phylogenetic Uncertainty But Not Parallel Plumage Evolution in a Recent Songbird Radiation.

Instances of parallel phenotypic evolution offer great opportunities to understand the evolutionary processes underlying phenotypic changes. However, confirming parallel phenotypic evolution and studying its causes requires a robust phylogenetic framework. One such example is the "black-and-white wagtails," a group of 5 species in the songbird genus Motacilla: 1 species, Motacilla alba, shows wide intra-specific plumage variation, while the 4r others form 2 pairs of very similar-looking species (M. aguimp + M. samveasnae and M. grandis + M. maderaspatensis, respectively). However, the 2 species in each of these pairs were not recovered as sisters in previous phylogenetic inferences. Their relationships varied depending on the markers used, suggesting that gene tree heterogeneity might have hampered accurate phylogenetic inference. Here, we use whole genome resequencing data to explore the phylogenetic relationships within this group, with a special emphasis on characterizing the extent of gene tree heterogeneity and its underlying causes. We first used multispecies coalescent methods to generate a "complete evidence" phylogenetic hypothesis based on genome-wide variants, while accounting for incomplete lineage sorting (ILS) and introgression. We then investigated the variation in phylogenetic signal across the genome to quantify the extent of discordance across genomic regions and test its underlying causes. We found that wagtail genomes are mosaics of regions supporting variable genealogies, because of ILS and inter-specific introgression. The most common topology across the genome, supporting M. alba and M. aguimp as sister species, appears to be influenced by ancient introgression. Additionally, we inferred another ancient introgression event, between M. alba and M. grandis. By combining results from multiple analyses, we propose a phylogenetic network for the black-and-white wagtails that confirms that similar phenotypes evolved in non-sister lineages, supporting parallel plumage evolution. Furthermore, the inferred reticulations do not connect species with similar plumage coloration, suggesting that introgression does not underlie parallel plumage evolution in this group. Our results demonstrate the importance of investing genome-wide patterns of gene tree heterogeneity to help understand the mechanisms underlying phenotypic evolution. [Gene tree heterogeneity; incomplete lineage sorting; introgression; parallel evolution; phylogenomics; plumage evolution; wagtails.].

Genomic evolution and insights into agronomic trait innovations of Sesamum species

Sesame is an ancient oilseed crop with high oil content and quality. However, the evolutionary history and genetic mechanisms of its valuable agronomic traits remain unclear. Here, we report chromosome-scale genomes of cultivated sesame (Sesamum indicum L.) and six wild Sesamum species, representing all three karyotypes within this genus. Karyotyping and genome-based phylogenic analysis revealed the evolutionary route of Sesamum species from n = 13 to n = 16 and revealed that allotetraploidization occurred in the wild species Sesamum radiatum. Early divergence of the Sesamum genus (48.5–19.7 million years ago) during the Tertiary period and its ancient phylogenic position within eudicots were observed. Pan-genome analysis revealed 9164 core gene families in the 7 Sesamum species. These families are significantly enriched in various metabolic pathways, including fatty acid (FA) metabolism and FA biosynthesis. Structural variations in SiPT1 and SiDT1 within the phosphatidyl ethanolamine-binding protein gene family lead to the genomic evolution of plant-architecture and inflorescence-development phenotypes in Sesamum. A genome-wide association study (GWAS) of an interspecific population and genome comparisons revealed a long terminal repeat insertion and a sequence deletion in DIR genes of wild Sesamum angustifolium and cultivated sesame, respectively; both variations independently cause high susceptibility to Fusarium wilt disease. A GWAS of 560 sesame accessions combined with an overexpression study confirmed that the NAC1 and PPO genes play an important role in upregulating oil content of sesame. Our study provides high-quality genomic resources for cultivated and wild Sesamum species and insights that can improve molecular breeding strategies for sesame and other oilseed crops.

Modelling the impacts of male alternative reproductive tactics on population dynamics.

Observations of male alternative reproductive tactics (ARTs) in a variety of species have stimulated the development of mathematical models that can account for the evolution and stable coexistence of multiple male phenotypes. However, little attention has been given to the population dynamic consequences of ARTs. We present a population model that takes account of the existence of two male ARTs (guarders and sneakers), assuming that tactic frequencies are environmentally determined and tactic reproductive success depends on the densities of both types. The presence of sneakers typically increases overall population density. However, if sneakers comprise a sufficiently large proportion of the population-or, equivalently, if guarders are sufficiently rare-then it is possible for the total population to crash to extinction (in this extreme regime, there is also an Allee effect, i.e. a threshold density below which the population will go extinct). We apply the model to the example of the invasive round goby (Neogobius melanostomus). We argue that ARTs can dramatically influence population dynamics and suggest that considering such phenotypic plasticity in population models is potentially important, especially for species of conservation or commercial importance.