Prevalence and Adaptive Impact of Introgression.

Alleles that introgress between species can influence the evolutionary and ecological fate of species exposed to novel environments. Hybrid offspring of different species are often unfit, and yet it has long been argued that introgression can be a potent force in evolution, especially in plants. Over the last two decades, genomic data have increasingly provided evidence that introgression is a critically important source of genetic variation and that this additional variation can be useful in adaptive evolution of both animals and plants. Here, we review factors that influence the probability that foreign genetic variants provide long-term benefits (so-called adaptive introgression) and discuss their potential benefits. We find that introgression plays an important role in adaptive evolution, particularly when a species is far from its fitness optimum, such as when they expand their range or are subject to changing environments.

Magnetic resonance linear accelerator technology and adaptive radiation therapy: An overview for clinicians.

Radiation therapy (RT) continues to play an important role in the treatment of cancer. Adaptive RT (ART) is a novel method through which RT treatments are evolving. With the ART approach, computed tomography or magnetic resonance (MR) images are obtained as part of the treatment delivery process. This enables the adaptation of the irradiated volume to account for changes in organ and/or tumor position, movement, size, or shape that may occur over the course of treatment. The advantages and challenges of ART maybe somewhat abstract to oncologists and clinicians outside of the specialty of radiation oncology. ART is positioned to affect many different types of cancer. There is a wide spectrum of hypothesized benefits, from small toxicity improvements to meaningful gains in overall survival. The use and application of this novel technology should be understood by the oncologic community at large, such that it can be appropriately contextualized within the landscape of cancer therapies. Likewise, the need to test these advances is pressing. MR-guided ART (MRgART) is an emerging, extended modality of ART that expands upon and further advances the capabilities of ART. MRgART presents unique opportunities to iteratively improve adaptive image guidance. However, although the MRgART adaptive process advances ART to previously unattained levels, it can be more expensive, time-consuming, and complex. In this review, the authors present an overview for clinicians describing the process of ART and specifically MRgART.

Genetic adaptations for the oceanic success of fish eggs.

Genetic adaptations of organisms living in extreme environments are fundamental to our understanding of where life can evolve. Water is the single limiting parameter in this regard, yet when released in the oceans, the single-celled eggs of marine bony fishes (teleosts) have no means of acquiring it. They are strongly hyposmotic to seawater and lack osmoregulatory systems. Paradoxically, modern teleosts successfully release vast quantities of eggs in the extreme saline environment and recorded the most explosive radiation in vertebrate history. Here, we highlight key genetic adaptations that evolved to solve this paradox by filling the pre-ovulated eggs with water. The degree of water acquisition is uniquely prevalent to marine teleosts, permitting the survival and oceanic dispersal of their eggs.

How exceptional are the classic adaptive radiations of passerine birds?

We investigated whether celebrated cases of evolutionary radiations of passerine birds on islands have produced exceptional morphological diversity relative to comparable-aged radiations globally. Based on eight external measurements, we calculated the disparity in size and shape within clades, each of which was classified as being tropical or temperate and as having diversified in a continental or an island/archipelagic setting. We found that the distribution of disparity among all clades does not differ substantively from a normal distribution, which would be consistent with a common underlying process of morphological diversification that is largely independent of latitude and occurrence on islands. Disparity is slightly greater in island clades than in those from continents or clades consisting of island and noninsular taxa, revealing a small, but significant, effect of island occurrence on evolutionary divergence. Nonetheless, the number of highly disparate clades overall is no greater than expected from a normal distribution, calling into question the need to invoke key innovations, ecological opportunity, or other factors as stimuli for adaptive radiations in passerine birds.

Gene and Allele-Specific Expression Underlying the Electric Signal Divergence in African Weakly Electric Fish.

In the African weakly electric fish genus Campylomormyrus, electric organ discharge signals are strikingly different in shape and duration among closely related species, contribute to prezygotic isolation, and may have triggered an adaptive radiation. We performed mRNA sequencing on electric organs and skeletal muscles (from which the electric organs derive) from 3 species with short (0.4 ms), medium (5 ms), and long (40 ms) electric organ discharges and 2 different cross-species hybrids. We identified 1,444 upregulated genes in electric organ shared by all 5 species/hybrid cohorts, rendering them candidate genes for electric organ-specific properties in Campylomormyrus. We further identified several candidate genes, including KCNJ2 and KLF5, and their upregulation may contribute to increased electric organ discharge duration. Hybrids between a short (Campylomormyrus compressirostris) and a long (Campylomormyrus rhynchophorus) discharging species exhibit electric organ discharges of intermediate duration and showed imbalanced expression of KCNJ2 alleles, pointing toward a cis-regulatory difference at this locus, relative to electric organ discharge duration. KLF5 is a transcription factor potentially balancing potassium channel gene expression, a crucial process for the formation of an electric organ discharge. Unraveling the genetic basis of the species-specific modulation of the electric organ discharge in Campylomormyrus is crucial for understanding the adaptive radiation of this emerging model taxon of ecological (perhaps even sympatric) speciation.

Considering Decoupled Phenotypic Diversification Between Ontogenetic Phases in Macroevolution: An Example Using Triggerfishes (Balistidae).

Across the Tree of Life, most studies of phenotypic disparity and diversification have been restricted to adult organisms. However, many lineages have distinct ontogenetic phases that differ from their adult forms in morphology and ecology. Focusing disproportionately on the evolution of adult forms unnecessarily hinders our understanding of the pressures shaping evolution over time. Non-adult disparity patterns are particularly important to consider for coastal ray-finned fishes, which can have juvenile phases with distinct phenotypes. These juvenile forms are often associated with sheltered nursery environments, with phenotypic shifts between adults and juvenile stages that are readily apparent in locomotor morphology. Whether this ontogenetic variation in locomotor morphology reflects a decoupling of diversification dynamics between life stages remains unknown. Here we investigate the evolutionary dynamics of locomotor morphology between adult and juvenile triggerfishes. We integrate a time-calibrated phylogenetic framework with geometric morphometric approaches and measurement data of fin aspect ratio and incidence, and reveal a mismatch between morphospace occupancy, the evolution of morphological disparity, and the tempo of trait evolution between life stages. Collectively, our results illuminate how the heterogeneity of morpho-functional adaptations can decouple the mode and tempo of morphological diversification between ontogenetic stages.

Adaptive radiation without independent stages of trait evolution in a group of Caribbean anoles.

Adaptive radiation involves diversification along multiple trait axes, producing phenotypically diverse, species-rich lineages. Theory generally predicts that multi-trait evolution occurs via a 'stages' model, with some traits saturating early in a lineage's history, and others diversifying later. Despite its multidimensional nature, however, we know surprisingly little about how different suites of traits evolve during adaptive radiation. Here, we investigated the rate, pattern, and timing of morphological and physiological evolution in the anole lizard adaptive radiation from the Caribbean island of Hispaniola. Rates and patterns of morphological and physiological diversity are largely unaligned, corresponding to independent selective pressures associated with structural and thermal niches. Cold tolerance evolution reflects parapatric divergence across elevation, rather than niche partitioning within communities. Heat tolerance evolution and the preferred temperature evolve more slowly than cold tolerance, reflecting behavioral buffering, particularly in edge-habitat species (a pattern associated with the Bogert effect). In contrast to the nearby island of Puerto Rico, closely related anoles on Hispaniola do not sympatrically partition thermal niche space. Instead, allopatric and parapatric separation across biogeographic and environmental boundaries serves to keep morphologically similar close relatives apart. The phenotypic diversity of this island's adaptive radiation accumulated largely as a by-product of time, with surprisingly few exceptional pulses of trait evolution. A better understanding of the processes that guide multidimensional trait evolution (and nuance therein) will prove key in determining whether the stages model should be considered a common theme of adaptive radiation.

The Sequential Direct and Indirect Effects of Mountain Uplift, Climatic Niche, and Floral Trait Evolution on Diversification Dynamics in an Andean Plant Clade.

Why and how organismal lineages radiate is commonly studied through either assessing abiotic factors (biogeography, geomorphological processes, and climate) or biotic factors (traits and interactions). Despite increasing awareness that both abiotic and biotic processes may have important joint effects on diversification dynamics, few attempts have been made to quantify the relative importance and timing of these factors, and their potentially interlinked direct and indirect effects, on lineage diversification. We here combine assessments of historical biogeography, geomorphology, climatic niche, vegetative, and floral trait evolution to test whether these factors jointly, or in isolation, explain diversification dynamics of a Neotropical plant clade (Merianieae, Melastomataceae). After estimating ancestral areas and the changes in niche and trait disparity over time, we employ Phylogenetic Path Analyses as a synthesis tool to test eleven hypotheses on the individual direct and indirect effects of these factors on diversification rates. We find strongest support for interlinked effects of colonization of the uplifting Andes during the mid-Miocene and rapid abiotic climatic niche evolution in explaining a burst in diversification rate in Merianieae. Within Andean habitats, later increases in floral disparity allowed for the exploitation of wider pollination niches (i.e., shifts from bee to vertebrate pollinators), but did not affect diversification rates. Our approach of including both vegetative and floral trait evolution, rare in assessments of plant diversification in general, highlights that the evolution of woody habit and larger flowers preceded the colonization of the Andes, but was likely critical in enabling the rapid radiation in montane environments. Overall, and in concert with the idea that ecological opportunity is a key element of evolutionary radiations, our results suggest that a combination of rapid niche evolution and trait shifts was critical for the exploitation of newly available niche space in the Andes in the mid-Miocene. Further, our results emphasize the importance of incorporating both abiotic and biotic factors into the same analytical framework if we aim to quantify the relative and interlinked effects of these processes on diversification.

Rapid radiation in a highly diverse marine environment.

Rapid diversification is often observed when founding species invade isolated or newly formed habitats that provide ecological opportunity for adaptive radiation. However, most of the Earth's diversity arose in diverse environments where ecological opportunities appear to be more constrained. Here, we present a striking example of a rapid radiation in a highly diverse marine habitat. The hamlets, a group of reef fishes from the wider Caribbean, have radiated into a stunning diversity of color patterns but show low divergence across other ecological axes. Although the hamlet lineage is ∼26 My old, the radiation appears to have occurred within the last 10,000 generations in a burst of diversification that ranks among the fastest in fishes. As such, the hamlets provide a compelling backdrop to uncover the genomic elements associated with phenotypic diversification and an excellent opportunity to build a broader comparative framework for understanding the drivers of adaptive radiation. The analysis of 170 genomes suggests that color pattern diversity is generated by different combinations of alleles at a few large-effect loci. Such a modular genomic architecture of diversification has been documented before in Heliconius butterflies, capuchino finches, and munia finches, three other tropical radiations that took place in highly diverse and complex environments. The hamlet radiation also occurred in a context of high effective population size, which is typical of marine populations. This allows for the accumulation of new variants through mutation and the retention of ancestral genetic variation, both of which appear to be important in this radiation.

Replicated Functional Evolution in Cichlid Adaptive Radiations.

AbstractAdaptive radiations highlight the mechanisms by which species and traits diversify and the extent to which these patterns are predictable. We used 1,110 high-speed videos of suction feeding to study functional and morphological diversification in 300 cichlid species from three African Great Lake radiations of varying ages (Victoria, Malawi, and Tanganyika) and an older, spatially dispersed continental radiation in the Neotropics. Among African radiations, standing diversity was reflective of time. Morphological and functional variance in Lake Victoria, the youngest radiation, was a subset of that within Lake Malawi, which itself was nested within the older Tanganyikan radiation. However, functional diversity in Neotropical cichlids was often lower than that in Lake Tanganyika, despite being much older. These two radiations broadly overlapped, but each diversified into novel trait spaces not found in the youngest lake radiations. Evolutionary rates across radiations were inversely related to age, suggesting extremely rapid trait evolution at early stages, particularly in lake radiations. Despite this support for early bursts, other patterns of trait diversity were inconsistent with expectations of adaptive radiations. This work suggests that cichlid functional evolution has played out in strikingly similar fashion in different radiations, with contingencies eventually resulting in lineage-specific novelties.

Mosaic evolution underlies feliform morphological disparity.

Constraint is a fundamental concept in evolutionary theory. Morphology and ecology both are limited by functional, historical and developmental factors to a subset of the theoretical range species could occupy. Cat-like carnivorans (Feliformia) offer a unique opportunity to investigate phenotypic constraint, as several feliform clades are purported to be limited to generalized ecomorphological roles, while others possess extremely specialized durophagous (bone-crushing) and sabretooth morphology. We investigated the evolutionary history of feliforms by considering their phylogeny, morphological disparity and rates of evolution. We recover results that show a mosaic pattern exists in the degree of morphological disparity per anatomical region per clade and ecology. Non-hypercarnivores, such as viverrids (civets and genets), Malagasy euplerids and lophocyonids (extinct hypocarnivores), have the greatest dental disparity, while hypercarnivores (felids, nimravids, many hyaenids) have the lowest dental disparity but highest cranial and mandibular disparity (excluding dentition). However, high disparity is not necessarily associated with high rates of evolution, but instead with ecological radiations. We reveal that relationships between specialization and disparity are not as simple as past research has concluded. Instead, morphological disparity results from an anatomical mosaic of evolution, where different ecologies correlate with and likely channel unique patterns/combinations of disparity per anatomical partition.

The evolution of ectomycorrhizal symbiosis in the Late Cretaceous is a key driver of explosive diversification in Agaricomycetes.

Ectomycorrhizal (EcM) symbiosis, a ubiquitous plant-fungus interaction in forests, evolved in parallel in fungi. Why the evolution of EcM fungi did not necessarily increase ecological opportunities for explosive diversification remains unclear. This study aimed to reveal the driving mechanism of the evolutionary diversification in the fungal class Agaricomycetes, specifically by testing whether the evolution of EcM symbiosis in the Late Cretaceous increased ecological opportunities. The historical character transitions of trophic state and fruitbody form were estimated based on phylogenies inferred from fragments of 89 single-copy genes. Moreover, five analyses were used to estimate the net diversification rates (speciation rate minus extinction rate). The results indicate that the unidirectional evolution of EcM symbiosis occurred 27 times, ranging in date from the Early Triassic to the Early Paleogene. The increased diversification rates appeared to occur intensively at the stem of EcM fungal clades diverging in the Late Cretaceous, coinciding with the rapid diversification of EcM angiosperms. By contrast, the evolution of fruitbody form was not strongly linked with the increased diversification rates. These findings suggest that the evolution of EcM symbiosis in the Late Cretaceous, supposedly with coevolving EcM angiosperms, was the key drive of the explosive diversification in Agaricomycetes.

The biogeographic and evolutionary processes shaping population divergence in Laupala.

Speciation generates biodiversity and the mechanisms involved are thought to vary across the tree of life and across environments. For example, well-studied adaptive radiations are thought to be fuelled by divergent ecological selection, but additionally are influenced heavily by biogeographic, genomic and demographic factors. Mechanisms of non-adaptive radiations, producing ecologically cryptic taxa, have been less well-studied but should likewise be influenced by these latter factors. Comparing among contexts can help pinpoint universal mechanisms and outcomes, especially if we integrate biogeographic, ecological and evolutionary processes. We investigate population divergence in the swordtail cricket Laupala cerasina, a wide-spread endemic on Hawai'i Island and one of 38 ecologically cryptic Laupala species. The nine sampled populations show striking population genetic structure at small spatio-temporal scales. The rapid differentiation among populations and species of Laupala shows that neither a specific geographical context nor ecological opportunity are pre-requisites for rapid divergence. Spatio-temporal patterns in population divergence, population size change, and gene flow are aligned with the chronosequence of the four volcanoes on which L. cerasina occurs and reveal the composite effects of geological dynamics and Quaternary climate change on population dynamics. Spatio-temporal patterns in genetic variation along the genome reveal the interplay of genetic and genomic architecture in shaping population divergence. In early phases of divergence, we find elevated differentiation in genomic regions harbouring mating song loci. In later stages of divergence, we find a signature of linked selection that interacts with recombination rate variation. Comparing our findings with recent work on complementary systems supports the conclusion that mostly universal factors influence the speciation process.

Exploring the phylogeny and depth evolution of cusk eels and their relatives (Ophidiiformes: Ophidioidei).

With 289 known species in 51 genera, the ophidiiform family Ophidiidae together with their relatives from the Carapidae (36 species in eight genera) of the same suborder Ophidioidei dominate the deep sea, but some occur also in shallow water habitats. Despite their high species diversity in the deep sea and wide bathymetric distributions, their phylogenetic relationships and evolution remain unexplored due in part to sampling difficulties. Thanks to the biodiversity exploratory program entitled "Tropical Deep-Sea Benthos" and joint efforts between Taiwan and French teams for sampling from different localities across the Indo-West Pacific over the last two decades, we are able to compile comprehensive datasets for investigations. In this study, 59 samples representing 36 of 59 known ophidioid genera are selected and used to construct a multi-gene dataset to infer the phylogenetic relationships of ophidioid fishes and their relatives. Our results reveal that the Ophidiidae forms a paraphyletic group with respect to the Carapidae. The four main clades of Ophidioidei resolved are the (1) clade comprising species from the subfamily Brotulinae; (2) clade that includes species in the genera Acanthonus and Xyelacyba; (3) clade grouping Hypopleuron caninum with species from the family Carapidae; and (4) clade containing the species in the subfamily Brotulotaenilinae, Neobythitinae (in part), and Ophidiinae. Accordingly, we suggest the following new revisions based on our results and proposed morphological diagnoses. The subfamily Brotulinae should be elevated to the family level. The genera Xyelacyba and probably Tauredophidium (unsampled in this study) should be included in the newly established family Acanthonidae with Acanthonus. The families Carapidae and Ophidiidae are re-defined. Our time-calibrated phylogenetic and ancestral depth reconstructions enable us to clarify the evolutionary history of ophidiiform fishes and infer past patterns of species distributions at different depths. While Ophidiiformes is inferred to have originated in shallow waters around 96.25 million years ago (Mya), the common ancestor to the Ophidioidei is inferred to have invaded the deep sea around 90.22 Mya, the dates coinciding with the global anoxic event of the OAE2. The observed bathymetric distribution patterns in Ophidioidei most likely point to the mesopelagic zone as the center of origin and diversification. This was followed by multiple events of depth transitions or range expansions towards either shallower waters or greater depth zones, which were likely triggered by past climate changes during the Paleogene-Neogene.

Artificial intelligence for treatment delivery: image-guided radiotherapy.

Radiation therapy (RT) is a highly digitized field relying heavily on computational methods and, as such, has a high affinity for the automation potential afforded by modern artificial intelligence (AI). This is particularly relevant where imaging is concerned and is especially so during image-guided RT (IGRT). With the advent of online adaptive RT (ART) workflows at magnetic resonance (MR) linear accelerators (linacs) and at cone-beam computed tomography (CBCT) linacs, the need for automation is further increased. AI as applied to modern IGRT is thus one area of RT where we can expect important developments in the near future. In this review article, after outlining modern IGRT and online ART workflows, we cover the role of AI in CBCT and MRI correction for dose calculation, auto-segmentation on IGRT imaging, motion management, and response assessment based on in-room imaging.

A late burst of colour evolution in a radiation of songbirds (Passeriformes: Parulidae) suggests secondary contact drives signal divergence.

Evolutionary radiations provide important insights into species diversification, which is especially true of adaptive radiations. New World wood warblers (Parulidae) are a family of small, insectivorous, forest-dwelling passerine birds, often considered an exemplar of adaptive radiation due to their rapid diversification followed by a slowdown. However, they deviate from the expectations of an adaptive radiation scenario due to the lack of conspicuous morphological and ecological differentiation. We fitted several macroevolutionary models to trait data in 105 species of wood warblers. We tested whether morphological traits underwent an early burst of evolution (suggesting adaptation to new ecological niches in adaptive radiations) and whether song and colour underwent a diversity-dependent acceleration of trait evolutionary rate (consistent with reproductive interference driving signal evolution). Morphology and song evolved gradually under stabilizing selection, suggesting niche conservatism, with morphology possibly acting as a constraint on song evolution. In contrast, many feather colour traits underwent a diversity-dependent burst of evolution occurring late in the clade's history. We suggest that a two-step process has led to the remarkable diversification of wood warblers. First, their early diversification probably proceeded by allopatric speciation. Second, feather colour divergence likely occurred during secondary contact after range expansion. This diversification of signalling traits might have facilitated species coexistence, in combination with behavioural niche partitioning. Wood warblers seem to present characteristics of both adaptive and non-adaptive radiations.

Sympatry and parapatry among rocky reef cichlids of Lake Victoria explained by female mating preferences.

Work on the Lake Victoria cichlids Pundamilia nyererei (red dorsum males, deeper water), Pundamilia pundamilia (blue males, shallower water) and related species pairs has provided insights into processes of speciation. Here, we investigate the female mating behaviour of 5 Pundamilia species and 4 of their F1 hybrids through mate choice trials and paternity testing. Complete assortative mating was observed among all sympatric species. Parapatric species with similar depth habitat distributions interbred whereas other parapatric and allopatric species showed complete assortative mating. F1 hybrids mated exclusively with species accepted by females of the parental species. The existence of complete assortative mating among some currently allopatric species suggests that pre-existing mating barriers could be sufficient to explain current patterns of co-existence, although, of course, many other factors may be involved. Regardless of the mechanism, mating preferences may influence species distribution in potentially hybridizing taxa, such as in the adaptive radiation of cichlid fish. We suggest that this at least partly explains why some species fail to establish breeding populations in locations where they are occasionally recorded. Our results support the notion that the mating preferences of potentially cross-breeding species ought to be included in coexistence theory.

Populating a Continent: Phylogenomics Reveal the Timing of Australian Frog Diversification.

The Australian continent's size and isolation make it an ideal place for studying the accumulation and evolution of biodiversity. Long separated from the ancient supercontinent Gondwana, most of Australia's plants and animals are unique and endemic, including the continent's frogs. Australian frogs comprise a remarkable ecological and morphological diversity categorized into a small number of distantly related radiations. We present a phylogenomic hypothesis based on an exon-capture dataset that spans the main clades of Australian myobatrachoid, pelodryadid hyloid, and microhylid frogs. Our time-calibrated phylogenomic-scale phylogeny identifies great disparity in the relative ages of these groups which vary from Gondwanan relics to recent immigrants from Asia and include arguably the continent's oldest living vertebrate radiation. This age stratification provides insight into the colonization of⁠, and diversification on, the Australian continent through deep time, during periods of dramatic climatic and community changes. Contemporary Australian frog diversity highlights the adaptive capacity of anurans, particularly in response to heat and aridity, and explains why they are one of the continent's most visible faunas.

The Non-Dereliction in Evolution: Trophic Specialisation Drives Convergence in the Radiation of Red Devil Spiders (Araneae: Dysderidae) in the Canary Islands.

Natural selection plays a key role in deterministic evolution, as clearly illustrated by the multiple cases of repeated evolution of ecomorphological characters observed in adaptive radiations. Unlike most spiders, Dysdera species display a high variability of cheliceral morphologies, which has been suggested to reflect different levels of specialization to feed on isopods. In this study, we integrate geometric morphometrics and experimental trials with a fully resolved phylogeny of the highly diverse endemic species from the Canary Islands to 1) quantitatively delimit the different cheliceral morphotypes present in the archipelago, 2) test their association with trophic specialization, as reported for continental species, 3) reconstruct the evolution of these ecomorphs throughout the diversification of the group, 4) test the hypothesis of convergent evolution of the different morphotypes, and 5) examine whether specialization constitutes a case of evolutionary irreversibility in this group. We show the existence of 9 cheliceral morphotypes and uncovered their significance for trophic ecology. Further, we demonstrate that similar ecomorphs evolved multiple times in the archipelago, providing a novel study system to explain how convergent evolution and irreversibility due to specialization may be combined to shape phenotypic diversification in adaptive radiations.

A multi-peak performance landscape for scale biting in an adaptive radiation of pupfishes.

The physical interactions between organisms and their environment ultimately shape diversification rates, but the contributions of biomechanics to evolutionary divergence are frequently overlooked. Here, we estimated a performance landscape for biting in an adaptive radiation of Cyprinodon pupfishes, including scale-biting and molluscivore specialists, and compared performance peaks with previous estimates of the fitness landscape in this system. We used high-speed video to film feeding strikes on gelatin cubes by scale eater, molluscivore, generalist and hybrid pupfishes and measured bite dimensions. We then measured five kinematic variables from 227 strikes using the SLEAP machine-learning model. We found a complex performance landscape with two distinct peaks best predicted gel-biting performance, corresponding to a significant non-linear interaction between peak gape and peak jaw protrusion. Only scale eaters and their hybrids were able to perform strikes within the highest performance peak, characterized by larger peak gapes and greater jaw protrusion. A performance valley separated this peak from a lower performance peak accessible to all species, characterized by smaller peak gapes and less jaw protrusion. However, most individuals exhibited substantial variation in strike kinematics and species could not be reliably distinguished by their strikes, indicating many-to-many mapping of morphology to performance. The two performance peaks observed in the lab were partially consistent with estimates of a two-peak fitness landscape measured in the wild, with the exception of the new performance peak for scale eaters. We thus reveal a new bimodal non-linear biomechanical model that connects morphology to performance to fitness in a sympatric radiation of trophic niche specialists.