The tempo and mode of character evolution in the assembly of mimetic communities.

Multitrait adaptive evolution is shaped by factors such as phylogenetic and functional constraints as well as the intensity and direction of selection. The tempo and mode of such multitrait evolution can differentially impact the assembly of biological communities. Batesian mimicry, in which undefended prey gain a fitness advantage by evolving a resemblance to aposematic models, involves adaptive evolution of multiple traits such as color patterns and flight morphology. To elucidate the evolutionary mechanisms of such multitrait adaptations, we evaluated the tempo and mode of adaptive convergence in flight morphology and color patterns in mimetic butterfly communities. We found that compared with Batesian mimics or nonmimetic sister species, models showed significantly faster rates of aposematic trait evolution, creating adaptive peaks for mimicry. At the community level, the degree of mimetic resemblance between mimics and models was positively correlated with the rate of character evolution, but independent of phylogenetic relatedness. Monomorphic mimics and female-limited mimics converged on the color patterns of models to a similar degree, showing that there were no constraints on mimetic trait evolution with respect to sex-specific selections. Convergence was driven by the greater lability of color patterns, which evolved at significantly faster rates than the phylogenetically conserved flight morphological traits, indicating that the two traits evolve under differential selection pressures and/or functional and genetic constraints. These community-wide patterns show that during the assembly of a community, the tempo of adaptive evolution is nonlinear, and specific to the underlying functional relationships and key traits that define the community.

The deep sea is a hot spot of fish body shape evolution.

Deep-sea fishes have long captured our imagination with striking adaptations to life in the mysterious abyss, raising the possibility that this cold, dark ocean region may be a key hub for physiological and functional diversification. We explore this idea through an analysis of body shape evolution across ocean depth zones in over 3000 species of marine teleost fishes. We find that the deep ocean contains twice the body shape disparity of shallow waters, driven by elevated rates of evolution in traits associated with locomotion. Deep-sea fishes display more frequent adoption of forms suited to slow and periodic swimming, whereas shallow living species are concentrated around shapes conferring strong, sustained swimming capacity and manoeuvrability. Our results support long-standing impressions of the deep sea as an evolutionary hotspot for fish body shape evolution and highlight that factors like habitat complexity and ecological interactions are potential drivers of this adaptive diversification.

The evolution of red blood cell shape in fishes.

The size and shape of red blood cells (RBCs) provide key information on life-history strategies in vertebrates. However, little is known about how RBC shape evolved in response to environmental factors, body size and the role of evolutionary rate. Here, we analysed RBC morphometrics in a set of Teleostei (bony fishes) and Elasmobranchii (sharks and rays) species testing the hypothesis that phylogenetic relationship explains species occupation of morphospace. We collected data on cell and nucleus area and volume, nucleus:cytoplasm ratio and shape factor for 65 species belonging to 28 orders. Then, we built phylomorphospaces separately for bony fish and sharks and rays. To test whether phylogenetic relationships predicted phenotypic similarity, we calculated multivariate phylogenetic signal. We also estimated the evolutionary rate of RBC shape for each node and tip using ridge regression. Finally, we tested whether habitat and body size influenced RBC shape using a PGLS. We found a significant phylogenetic signal in RBC shape for bony fish, but not sharks and rays. Saltwater teleost species were more clustered than freshwater ones in the phylomorphospace, suggesting clade disparity. Accordingly, the rate of evolution was highly heterogeneous, with significant decrease in Acanthopterygii. Neither habitat nor body size influenced RBC shape. In conclusion, RBC shape seems to have evolved in fishes in response to multiple selective pressures independent of life-history characters.

RNA-Seq of three free-living flatworm species suggests rapid evolution of reproduction-related genes.

BACKGROUND: The genus Macrostomum consists of small free-living flatworms and contains Macrostomum lignano, which has been used in investigations of ageing, stem cell biology, bioadhesion, karyology, and sexual selection in hermaphrodites. Two types of mating behaviour occur within this genus. Some species, including M. lignano, mate via reciprocal copulation, where, in a single mating, both partners insert their male copulatory organ into the female storage organ and simultaneously donate and receive sperm. Other species mate via hypodermic insemination, where worms use a needle-like copulatory organ to inject sperm into the tissue of the partner. These contrasting mating behaviours are associated with striking differences in sperm and copulatory organ morphology. Here we expand the genomic resources within the genus to representatives of both behaviour types and investigate whether genes vary in their rate of evolution depending on their putative function. RESULTS: We present de novo assembled transcriptomes of three Macrostomum species, namely M. hystrix, a close relative of M. lignano that mates via hypodermic insemination, M. spirale, a more distantly related species that mates via reciprocal copulation, and finally M. pusillum, which represents a clade that is only distantly related to the other three species and also mates via hypodermic insemination. We infer 23,764 sets of homologous genes and annotate them using experimental evidence from M. lignano. Across the genus, we identify 521 gene families with conserved patterns of differential expression between juvenile vs. adult worms and 185 gene families with a putative expression in the testes that are restricted to the two reciprocally mating species. Further, we show that homologs of putative reproduction-related genes have a higher protein divergence across the four species than genes lacking such annotations and that they are more difficult to identify across the four species, indicating that these genes evolve more rapidly, while genes involved in neoblast function are more conserved. CONCLUSIONS: This study improves the genus Macrostomum as a model system, by providing resources for the targeted investigation of gene function in a broad range of species. And we, for the first time, show that reproduction-related genes evolve at an accelerated rate in flatworms.

The Red Queen and King in finite populations.

In antagonistic symbioses, such as host-parasite interactions, one population's success is the other's loss. In mutualistic symbioses, such as division of labor, both parties can gain, but they might have different preferences over the possible mutualistic arrangements. The rates of evolution of the two populations in a symbiosis are important determinants of which population will be more successful: Faster evolution is thought to be favored in antagonistic symbioses (the "Red Queen effect"), but disfavored in certain mutualistic symbioses (the "Red King effect"). However, it remains unclear which biological parameters drive these effects. Here, we analyze the effects of the various determinants of evolutionary rate: generation time, mutation rate, population size, and the intensity of natural selection. Our main results hold for the case where mutation is infrequent. Slower evolution causes a long-term advantage in an important class of mutualistic interactions. Surprisingly, less intense selection is the strongest driver of this Red King effect, whereas relative mutation rates and generation times have little effect. In antagonistic interactions, faster evolution by any means is beneficial. Our results provide insight into the demographic evolution of symbionts.

Rapid evolution of testis size relative to sperm morphology suggests that post-copulatory selection targets sperm number in Anolis lizards.

Post-copulatory sexual selection is thought to be responsible for much of the extraordinary diversity in sperm morphology across metazoans. However, the extent to which post-copulatory selection targets sperm morphology versus sperm production is generally unknown. To address this issue, we simultaneously characterized the evolution of sperm morphology (length of the sperm head, midpiece and flagellum) and testis size (a proxy for sperm production) across 26 species of Anolis lizards, a group in which sperm competition is likely. We found that the length of the sperm midpiece has evolved 2-3 times faster than that of the sperm head or flagellum, suggesting that midpiece size may be the most important aspect of sperm morphology with respect to post-copulatory sexual selection. However, testis size has evolved faster than any aspect of sperm morphology or body size, supporting the hypothesis that post-copulatory sexual selection acts more strongly upon sperm production than upon sperm morphology. Likewise, evolutionary increases in testis size, which typically indicate increased sperm competition, are not associated with predictable changes in sperm morphology, suggesting that any effects of post-copulatory selection on sperm morphology are either weak or variable in direction across anoles. Collectively, our results suggest that sperm production is the primary target of post-copulatory sexual selection in this lineage.

Fungal mitochondrial genomes and genetic polymorphisms.

Mitochondria are the powerhouses of eukaryotic cells, responsible for ATP generation and playing a role in a diversity of cellular and organismal functions. Different from the majority of other intracellular membrane structures, mitochondria contain their own genetic materials that are capable of independent replication and inheritance. In this mini-review, we provide brief summaries of fungal mitochondrial genome structure, size, gene content, inheritance, and genetic variation. We pay special attention to the relative genetic polymorphisms of the mitochondrial vs nuclear genomes at the population level within individual fungal species. Among the 20 species/groups of species reviewed here, there is a range of variation among genes and species in the relative nuclear and mitochondrial genetic polymorphisms. Interestingly, most (15/20) showed a greater genetic diversity for nuclear genes and genomes than for mitochondrial genes and genomes, with the remaining five showing similar or slower nuclear genome genetic variations. This fungal pattern is different from the dominant pattern in animals, but more similar to that in plants. At present, the mechanisms for the variations among fungal species and the overall low level of mitochondrial sequence polymorphisms are not known. The increasing availability of population genomic data should help us reveal the potential genetic and ecological factors responsible for the observed variations.

SFREEMAP - A simulation-free tool for stochastic mapping.

BACKGROUND: Stochastic mapping is frequently used in comparative biology to simulate character evolution, enabling the probabilistic computation of statistics such as number of state transitions along a tree and distribution of states in its internal nodes. Common implementations rely on Continuous-time Markov Chain simulations whose parameters are difficult to adjust and subjected to inherent inaccuracy. Thus, researchers must run a large number of simulations in order to obtain adequate estimates. Although execution time tends to be relatively small when simulations are performed on a single tree assumed to be the "true" topology, it may become an issue if analyses are conducted on several trees, such as the ones that make up posterior distributions obtained via Bayesian phylogenetic inference. Working with such distributions is preferable to working with a single tree, for they allow the integration of phylogenetic uncertainty into parameter estimation. In such cases, detailed character mapping becomes less important than parameter integration across topologies. Here, we present an R-based implementation (SFREEMAP) of an analytical approach to obtain accurate, per-branch expectations of numbers of state transitions and dwelling times. We also introduce an intuitive way of visualizing the results by integrating over the posterior distribution and summarizing the parameters onto a target reference topology (such as a consensus or MAP tree) provided by the user. RESULTS: We benchmarked SFREEMAP's performance against make.simmap, a popular R-based implementation of stochastic mapping. SFREEMAP confirmed theoretical expectations outperforming make.simmap in every experiment and reducing computation time of relatively modest datasets from hours to minutes. We have also demonstrated that SFREEMAP returns estimates which were not only similar to the ones obtained by averaging across make.simmap mappings, but also more accurate, according to simulated data. We illustrate our visualization strategy using previously published data on the evolution of coloniality in scleractinian corals. CONCLUSION: SFREEMAP is an accurate and fast alternative to ancestral state reconstruction via simulation-based stochastic mapping.

Revisiting a Classic Study of the Molecular Clock.

A constant rate of molecular evolution among homologous proteins and across lineages is known as the molecular clock. This concept has been useful for estimating divergence times. Here, we revisit a study by Richard Dickerson (J Mol Evol 1:26-45, 1971), wherein he provided striking visual evidence for a constant rate of amino acid changes among various evolutionary branch points. Dickerson's study is commonly cited as support of the molecular clock and a figure from it is often reproduced in textbooks. Since its publication, however, there have been updates made to dates of common ancestors based on the fossil record that should be considered. Additionally, collecting the accession numbers and carefully outlining Dickerson's methods serves as a resource to students of the molecular clock hypothesis.

Evolution of circoviruses in lorikeets lags behind its hosts.

The presence of endogenous viral elements in host genomes hints towards much older host-virus relationships than predicted by exogenous phylogenies, with highly mutable single-stranded DNA (ssDNA) viruses and RNA viruses often occupying entangled multispecies ecological niches. The difficulty lies in unravelling the long-term evolutionary history of vertebrate virus-host relationships and determining the age of a potentially ancient tree based only fresh shoots at the tips. Resolving such lineages, and the sometimes great discrepancy amongst evolutionary timescales, is problematic, especially when purifying selection or recombination can significantly alter the accuracy of phylogenetic reconstruction methods. Pathogens which occupy entangled multispecies ecological niches add a further layer of complexity but we show that multi-host scenarios may also provide opportunities to identify allopatric or sympatric paleobiological signals that can unlock longer term phylogenies. We identified host-based, cryptic, sympatric differentiation in beak and feather disease virus in the Psittaciformes tribe Loriini along with endogenous circovirus motifs in Kea (Nestor notabilis) and Gondwanan vicariance estimates to infer the evolutionary timescale of the circoviruses. This demonstrated a chronology of psittacine circovirus speciation aligned to conservative Zealandic divergences for relic circovirus motifs in Kea and a 10million year divergence coinciding with the Papuan central range orogeny that triggered the radiation of Loriini and segregation of an antecedent viral clade in Australian lorikeets. Estimates of circovirus speciation in birds highlighted a Gondwanan dominant group in Neoaves with passerine, columbid and larid circoviruses deeply separated from those in waterfowl, consistent with a Triassic divergence of Galloanserae. The circovirus tree had a deep ancestry in invertebrates with a Palaeozoic expansion in fish and mammals. We show that longer term evolutionary relationships in viruses which have a high rate of mutation and admixture can be disentangled, highlighting that contemporary virus host-switching can be explained by deep intra-lineage host phylogeny.

Can We Identify Genes with Increased Phylogenetic Reliability?

Topological heterogeneity among gene trees is widely observed in phylogenomic analyses and some of this variation is likely caused by systematic error in gene tree estimation. Systematic error can be mitigated by improving models of sequence evolution to account for all evolutionary processes relevant to each gene or identifying those genes whose evolution best conforms to existing models. However, the best method for identifying such genes is not well established. Here, we ask if filtering genes according to their clock-likeness or posterior predictive effect size (PPES, an inference-based measure of model violation) improves phylogenetic reliability and congruence. We compared these approaches to each other, and to the common practice of filtering based on rate of evolution, using two different metrics. First, we compared gene-tree topologies to accepted reference topologies. Second, we examined topological similarity among gene trees in filtered sets. Our results suggest that filtering genes based on clock-likeness and PPES can yield a collection of genes with more reliable phylogenetic signal. For the two exemplar data sets we explored, from yeast and amniotes, clock-likeness and PPES outperformed rate-based filtering in both congruence and reliability.

Purifying selection on splice-related motifs, not expression level nor RNA folding, explains nearly all constraint on human lincRNAs.

There are two strong and equally important predictors of rates of human protein evolution: The amount the gene is expressed and the proportion of exonic sequence devoted to control splicing, mediated largely by selection on exonic splice enhancer (ESE) motifs. Is the same true for noncoding RNAs, known to be under very weak purifying selection? Prior evidence suggests that selection at splice sites in long intergenic noncoding RNAs (lincRNAs) is important. We now report multiple lines of evidence indicating that the great majority of purifying selection operating on lincRNAs in humans is splice related. Splice-related parameters explain much of the between-gene variation in evolutionary rate in humans. Expression rate is not a relevant predictor, although expression breadth is weakly so. In contrast to protein-coding RNAs, we observe no relationship between evolutionary rate and lincRNA stability. As in protein-coding genes, ESEs are especially abundant near splice junctions and evolve slower than non-ESE sequence equidistant from boundaries. Nearly all constraint in lincRNAs is at exon ends (N.B. the same is not witnessed in Drosophila). Although we cannot definitely answer the question as to why splice-related selection is so important, we find no evidence that splicing might enable the nonsense-mediated decay pathway to capture transcripts incorrectly processed by ribosomes. We find evidence consistent with the notion that splicing modifies the underlying chromatin through recruitment of splice-coupled chromatin modifiers, such as CHD1, which in turn might modulate neighbor gene activity. We conclude that most selection on human lincRNAs is splice mediated and suggest that the possibility of splice-chromatin coupling is worthy of further scrutiny.

Functional coupling constrains craniofacial diversification in Lake Tanganyika cichlids.

Functional coupling, where a single morphological trait performs multiple functions, is a universal feature of organismal design. Theory suggests that functional coupling may constrain the rate of phenotypic evolution, yet empirical tests of this hypothesis are rare. In fish, the evolutionary transition from guarding the eggs on a sandy/rocky substrate (i.e. substrate guarding) to mouthbrooding introduces a novel function to the craniofacial system and offers an ideal opportunity to test the functional coupling hypothesis. Using a combination of geometric morphometrics and a recently developed phylogenetic comparative method, we found that head morphology evolution was 43% faster in substrate guarding species than in mouthbrooding species. Furthermore, for species in which females were solely responsible for mouthbrooding the males had a higher rate of head morphology evolution than in those with bi-parental mouthbrooding. Our results support the hypothesis that adaptations resulting in functional coupling constrain phenotypic evolution.

Genes that escape X-inactivation in humans have high intraspecific variability in expression, are associated with mental impairment but are not slow evolving.

In female mammals most X-linked genes are subject to X-inactivation. However, in humans some X-linked genes escape silencing, these escapees being candidates for the phenotypic aberrations seen in polyX karyotypes. These escape genes have been reported to be under stronger purifying selection than other X-linked genes. Although it is known that escape from X-inactivation is much more common in humans than in mice, systematic assays of escape in humans have to date employed only interspecies somatic cell hybrids. Here we provide the first systematic next-generation sequencing analysis of escape in a human cell line. We analyzed RNA and genotype sequencing data obtained from B lymphocyte cell lines derived from Europeans (CEU) and Yorubans (YRI). By replicated detection of heterozygosis in the transcriptome, we identified 114 escaping genes, including 76 not previously known to be escapees. The newly described escape genes cluster on the X chromosome in the same chromosomal regions as the previously known escapees. There is an excess of escaping genes associated with mental retardation, consistent with this being a common phenotype of polyX phenotypes. We find both differences between populations and between individuals in the propensity to escape. Indeed, we provide the first evidence for there being both hyper- and hypo-escapee females in the human population, consistent with the highly variable phenotypic presentation of polyX karyotypes. Considering also prior data, we reclassify genes as being always, never, and sometimes escape genes. We fail to replicate the prior claim that genes that escape X-inactivation are under stronger purifying selection than others.

The effect of gene overlapping on the rate of RNA virus evolution.

Gene overlapping is widely employed by RNA viruses to generate genetic novelty while retaining a small genome size. However, gene overlapping also increases the deleterious effect of mutations as they affect more than one gene, thereby reducing the evolutionary rate of RNA viruses and hence their adaptive capacity. Although there is general agreement on the benefits of gene overlapping as a mechanism of genomic compression for rapidly evolving organisms, its effect on the pace of RNA virus evolution remains a source of debate. To address this issue, we collected sequence data from 117 instances of gene overlapping across 19 families, 30 genera, and 55 species of RNA viruses. On these data, we analyzed how genetic distances, selective pressures, and the distribution of RNA secondary structures and conserved protein functional domains vary between overlapping (OV) and nonoverlapping (NOV) regions. We show that gene overlapping generally results in a decrease in the rate of RNA virus evolution through a reduction in the frequency of synonymous mutations. However, this effect is less pronounced in genes with a terminal rather than an internal gene overlap, which might result from a greater proportion of protein functional conserved domains in NOV than in OV regions, in turn reducing the number of nonsynonymous mutations in the former. Overall, our analyses clarify the role of gene overlapping as a modulator of the evolutionary rates exhibited by RNA viruses and shed light on the factors that shape the genetic diversity of this important group of pathogens.

Ancient dates or accelerated rates? Morphological clocks and the antiquity of placental mammals.

Analyses of a comprehensive morphological character matrix of mammals using 'relaxed' clock models (which simultaneously estimate topology, divergence dates and evolutionary rates), either alone or in combination with an 8.5 kb nuclear sequence dataset, retrieve implausibly ancient, Late Jurassic-Early Cretaceous estimates for the initial diversification of Placentalia (crown-group Eutheria). These dates are much older than all recent molecular and palaeontological estimates. They are recovered using two very different clock models, and regardless of whether the tree topology is freely estimated or constrained using scaffolds to match the current consensus placental phylogeny. This raises the possibility that divergence dates have been overestimated in previous analyses that have applied such clock models to morphological and total evidence datasets. Enforcing additional age constraints on selected internal divergences results in only a slight reduction of the age of Placentalia. Constraining Placentalia to less than 93.8 Ma, congruent with recent molecular estimates, does not require major changes in morphological or molecular evolutionary rates. Even constraining Placentalia to less than 66 Ma to match the 'explosive' palaeontological model results in only a 10- to 20-fold increase in maximum evolutionary rate for morphology, and fivefold for molecules. The large discrepancies between clock- and fossil-based estimates for divergence dates might therefore be attributable to relatively small changes in evolutionary rates through time, although other explanations (such as overly simplistic models of morphological evolution) need to be investigated. Conversely, dates inferred using relaxed clock models (especially with discrete morphological data and MrBayes) should be treated cautiously, as relatively minor deviations in rate patterns can generate large effects on estimated divergence dates.

Global biogeography of the ectomycorrhizal /sebacina lineage (Fungi, Sebacinales) as revealed from comparative phylogenetic analyses.

Compared with plants and animals, large-scale biogeographic patterns of microbes including fungi are poorly understood. By the use of a comparative phylogenetic approach and ancestral state reconstructions, we addressed the global biogeography, rate of evolution and evolutionary origin of the widely distributed ectomycorrhizal (EcM) /sebacina lineage that forms a large proportion of the Sebacinales order. We downloaded all publicly available internal transcribed spacer (ITS) sequences and metadata and supplemented sequence information from three genes to construct dated phylogenies and test biogeographic hypotheses. The /sebacina lineage evolved 45-57 Myr ago that groups it with relatively young EcM taxa in other studies. The most parsimonious origin for /sebacina is inferred to be North American temperate coniferous forests. Among biogeographic traits, region and biome exhibited stronger phylogenetic signal than host family. Consistent with the resource availability (environmental energy) hypothesis, the ITS region is evolving at a faster rate in tropical than nontropical regions. Most biogeographic regions exhibited substantial phylogenetic clustering suggesting a strong impact of dispersal limitation over a large geographic scale. In northern Holarctic regions, however, phylogenetic distances and phylogenetic grouping of isolates indicate multiple recent dispersal events.

Stasis and convergence characterize morphological evolution in eupolypod II ferns.

BACKGROUND AND AIMS: Patterns of morphological evolution at levels above family rank remain underexplored in the ferns. The present study seeks to address this gap through analysis of 79 morphological characters for 81 taxa, including representatives of all ten families of eupolypod II ferns. Recent molecular phylogenetic studies demonstrate that the evolution of the large eupolypod II clade (which includes nearly one-third of extant fern species) features unexpected patterns. The traditional 'athyrioid' ferns are scattered across the phylogeny despite their apparent morphological cohesiveness, and mixed among these seemingly conservative taxa are morphologically dissimilar groups that lack any obvious features uniting them with their relatives. Maximum-likelihood and maximum-parsimony character optimizations are used to determine characters that unite the seemingly disparate groups, and to test whether the polyphyly of the traditional athyrioid ferns is due to evolutionary stasis (symplesiomorphy) or convergent evolution. The major events in eupolypod II character evolution are reviewed, and character and character state concepts are reappraised, as a basis for further inquiries into fern morphology. METHODS: Characters were scored from the literature, live plants and herbarium specimens, and optimized using maximum-parsimony and maximum-likelihood, onto a highly supported topology derived from maximum-likelihood and Bayesian analysis of molecular data. Phylogenetic signal of characters were tested for using randomization methods and fitdiscrete. KEY RESULTS: The majority of character state changes within the eupolypod II phylogeny occur at the family level or above. Relative branch lengths for the morphological data resemble those from molecular data and fit an ancient rapid radiation model (long branches subtended by very short backbone internodes), with few characters uniting the morphologically disparate clades. The traditional athyrioid ferns were circumscribed based upon a combination of symplesiomorphic and homoplastic characters. Petiole vasculature consisting of two bundles is ancestral for eupolypods II and a synapomorphy for eupolypods II under deltran optimization. Sori restricted to one side of the vein defines the recently recognized clade comprising Rhachidosoraceae through Aspleniaceae, and sori present on both sides of the vein is a synapomorphy for the Athyriaceae sensu stricto. The results indicate that a chromosome base number of x =41 is synapomorphic for all eupolypods, a clade that includes over two-thirds of extant fern species. CONCLUSIONS: The integrated approach synthesizes morphological studies with current phylogenetic hypotheses and provides explicit statements of character evolution in the eupolypod II fern families. Strong character support is found for previously recognized clades, whereas few characters support previously unrecognized clades. Sorus position appears to be less complicated than previously hypothesized, and linear sori restricted to one side of the vein support the clade comprising Aspleniaceae, Diplaziopsidaceae, Hemidictyaceae and Rachidosoraceae - a lineage only recently identified. Despite x =41 being a frequent number among extant species, to our knowledge it has not previously been demonstrated as the ancestral state. This is the first synapomorphy proposed for the eupolypod clade, a lineage comprising 67 % of extant fern species. This study provides some of the first hypotheses of character evolution at the family level and above in light of recent phylogenetic results, and promotes further study in an area that remains open for original observation.

Unintentional selection, unanticipated insights: introductions, stocking and the evolutionary ecology of fishes.

Natural environmental change has produced countless opportunities for species to disperse into and persist in habitats where they previously did not exist. Introduction and stocking programmes have facilitated similar sorts of colonization opportunities across considerably greater geographical scales and often in much shorter periods of time. Even though the mechanism of colonization differs, the result can be the same: evolutionary change in the colonizing population in response to novel selection pressures. As a consequence, some human-mediated fish transfers have unintentionally yielded novel research opportunities to study how phenotypes and genes interact with their environment and affect ecological and evolutionary change. The primary purpose here is to explore how work, directly or indirectly involved with human-mediated transfers, has unintentionally yielded novel research and research opportunities in fish ecology and evolution. Insights have produced new knowledge or altered previously held perceptions on topics such as local adaptation, rate of evolutionary change, phenotypic plasticity, alternative reproductive strategies, population structure and colonization probability. Well-documented stocking programmes, especially in terms of history, numbers and original population sources, can provide highly fertile ground for generating further insights on the ecology and evolution of fishes and of the factors likely to influence the success of conservation-based, restoration programmes.

Evolutionary patterns of cat-like carnivorans unveil drivers of the sabertooth morphology.

The sabertooth morphology stands as a classic case of convergence, manifesting recurrently across various vertebrate groups, prominently within two carnivorans clades: felids and nimravids. Nonetheless, the evolutionary mechanisms driving these recurring phenotypes remain insufficiently understood, lacking a robust phylogenetic and spatiotemporal framework. We reconstruct the tempo and mode of craniomandibular evolution of Felidae and Nimravidae and evaluate the strength of the dichotomy between conical and saber-toothed species, as well as within saber-toothed morphotypes. To do so, we investigate morphological variation, convergence, phenotypic integration, and evolutionary rates, employing a comprehensive dataset of nearly 200 3D models encompassing mandibles and crania from both extinct and extant feline-like carnivorans, spanning their entire evolutionary timeline. Our results reject the hypothesis of a distinctive sabertooth morphology, revealing instead a continuous spectrum of feline-like phenotypes in both the cranium and mandible, with sporadic instances of unequivocal convergence. Disparity peaked at the end of the Miocene and is usually higher in clades containing taxa with extreme sabertoothed adaptations. We show that taxa with saberteeth exhibit a lower degree of craniomandibular integration, allowing to exhibit a greater range of phenotypes. Those same groups usually show a burst of morphological evolutionary rate at the beginning of their evolutionary history. Consequently, we propose that a reduced degree of integration coupled with rapid evolutionary rates emerge as key components in the development of a sabertooth morphology in multiple clades.