Testing "species pair" hypotheses: evolutionary processes in the lichen-forming species complex Porpidia flavocoerulescens and Porpidia melinodes

Pairs of taxa are commonly found in lichen-forming ascomycetes that differ primarily in their reproductive modes: one taxon reproduces sexually, the other vegetatively. The evolutionary processes underlying such "species pairs" are unknown. The species pair formed by Porpidia flavocoerulescens (sexual) and Porpidia melinodes (vegetative) was chosen to investigate four previously proposed hypotheses. These hypotheses posit that species pairs are either two monophyletic, independently evolving species with contrasting reproductive mode; a single outcrossing species polymorphic with regard to its reproductive modes; a sexual mother lineage frequently giving rise to asexual spin-offs; or a complex of cryptic species. The phylogenetic patterns observed within the species pair in the present study were analyzed using stringent hypothesis testing and visualizations of relationships and conflict based on tree and network reconstructions. DNA sequences at the three analyzed loci revealed the same four to five deeply divergent lineages. A detailed analysis of DNA-sequence variability revealed closely linked gene loci, but high levels of conflict within each of the gene fragments, as well as between observed genetic lineages. The observed patterns of phylogenetic relationships, linkage, and conflict are not congruent with any of the previously proposed species pair hypotheses. Rather, it is proposed that the observed results can be explained by conflicting reproductive and nutritional requirements imposed by an obligate symbiotic lifestyle. These interacting constraints produce recurring selective sweeps within predominantly vegetatively reproducing lineages and are the main forces that shape the evolution within the investigated species pair.     

ANCESTRAL CHARACTER ESTIMATION UNDER THE THRESHOLD MODEL FROM QUANTITATIVE GENETICS

Evolutionary biology is a study of life's history on Earth. In researching this history, biologists are often interested in attempting to reconstruct phenotypes for the long extinct ancestors of living species. Various methods have been developed to do this on a phylogeny from the data for extant taxa. In the present article, I introduce a new approach for ancestral character estimation for discretely valued traits. This approach is based on the threshold model from evolutionary quantitative genetics. Under the threshold model, the value exhibited by an individual or species for a discrete character is determined by an underlying, unobserved continuous trait called “liability.” In this new method for ancestral state reconstruction, I use Bayesian Markov chain Monte Carlo (MCMC) to sample the liabilities of ancestral and tip species, and the relative positions of two or more thresholds, from their joint posterior probability distribution. Using data simulated under the model, I find that the method has very good performance in ancestral character estimation. Use of the threshold model for ancestral state reconstruction relies on a priori specification of the order of the discrete character states along the liability axis. I test the use of a Bayesian MCMC information theoretic criterion based approach to choose among different hypothesized orderings for the discrete character. Finally, I apply the method to the evolution of feeding mode in centrarchid fishes.     

Resolving evolutionary relationships in the lichen-forming genus Porpidia and related allies (Porpidiaceae, Ascomycota)

The lichen-forming genus Porpidia (Porpidiaceae, Ascomycota) provides excellent opportunities for evolutionary, reproductive, and ecological studies of crustose epilithic lichen symbioses. However, despite the fact that the genus itself seemed to be clearly delimited, the group was thought to be a hopeless case with regard to intrageneric relationships and species delimitations due to apparently rampant homoplasy throughout most character systems. Contrary to the situation for non-molecular data, a robust and generally well-resolved phylogeny was recovered based on DNA-sequence data. Separate and combined analyses of nuclear ribosomal RNA large subunit and nuclear beta-tubulin gene fragments were performed using maximum parsimony, maximum likelihood, and Bayesian approaches. Branch support was estimated using non-parametic bootstrapping and posterior probabilities, while monophyly of a priori defined groups was tested using posterior probabilities. The results reveal a highly supported "Porpidia sensu lato," however, Porpidia itself is not monophyletic. Several smaller genera of the Porpidiaceae and probably the large genus Lecidea (Lecideaceae) are nested within the group. Most taxa analyzed fall into one of four major subgroups within Porpidia s.l., though the basal relationships among these subgroups could not be supported. This phylogeny will make it possible to re-evaluate morphological and chemical characters in the group, and to conduct detailed studies of species delimitations within the monophyletic subgroups.     

Something for nothing? Reconstruction of ancestral character states in asterinid sea star development

SUMMARY Traits from early development mapped onto phylogenetic trees can potentially offer insight into the evolutionary history of development by inferring the states of those characters among ancestors at nodes in the phylogeny. A key and often-overlooked aspect of such mapping is the underlying model of character evolution. Without a well-supported and realistic model ("nothing"), character mapping of ancestral traits onto phylogenetic trees might often return results ("something") that lack a sound basis. Here we reconsider a challenging case study in this area of evolutionary developmental biology: the inference of ancestral states for ecological and morphological characters in the reproduction and larval development of asterinid sea stars. We apply improved analytical methods to an expanded set of asterinid phylogenetic data and developmental character states. This analysis shows that the new methods might generally offer some independent insight into choice of a model of character evolution, but that in the specific case of asterinid sea stars the quantitative features of the model (especially the relative probabilities of different directions of change) have an important effect on the results. We suggest caution in applying ancestral state reconstructions in the absence of an independently corroborated model of character evolution, and highlight the need for such modeling in evolutionary developmental biology.     

Reconstructing ancestral character states: a critical reappraisal

Using parsimony to reconstruct ancestral character states on a phylogenetic tree has become a popular method for testing ecological and evolutionary hypotheses. Despite its popularity, the assumptions and uncertainties of reconstructing the ancestral states of a single character have received less attention than the much less challenging endeavor of reconstructing phylogenetic trees from many characters. Recent research suggests that parsimony reconstructions are often sensitive to violations of the almost universal assumption of equal probabilities of gains and losses. In addition, maximum likelihood has been developed as an alternative to parsimony reconstruction, and has also revealed a surprising amount of uncertainty in ancestral reconstructions.     

More is better: the uses of developmental genetic data to reconstruct perianth evolution

The origin and evolution of the perianth remains enigmatic. While it seems likely that an undifferentiated perianth consisting of tepals arose early in angiosperm evolution, it is unclear when and how differentiated perianths consisting of distinct organs, such as petals and sepals, arose. Phylogenetic reconstructions of ancestral perianth states across angiosperms have traditionally relied on morphological data from extant species, but these analyses often produce equivocal results. Here we describe the use of developmental genetic data as an additional strategy to infer the ancestral perianth character state for different angiosperm clades. By assessing functional data in combination with expression data in a maximum likelihood framework, we provide a novel approach for investigating the evolutionary history of the perianth. Results of this analysis provide new insights into perianth evolution and provide a proof of concept for using this strategy to explore the incorporation of developmental genetic data in character state reconstructions. As the assumptions outlined here are tested and more genetic data are generated, we hope that ancestral state reconstructions based on multiple lines of evidence will converge.     

Optimal outgroup analysis

We present and critically examine a statistical criterion for the selection of outgroup taxa for rooting evolutionary trees. The criterion is the amount of phylogenetic signal for the ingroup when the states of the candidate outgroup taxa are assumed to be plesiomorphic relative to the ingroup for the purpose of measuring plesiomorphy content of the outgroup taxon. A statistical measure of rooted, ingroup signal was subjected to a suite of critical tests which indicate that it provides a proxy measure of plesiomorphy content. As the evolutionary distance between the ingroup ancestral node and outgroup taxa increases, the tree-independent measure of signal decreases, tracking the decay in plesiomorphy content and the increase in convergence to the ingroup states. We show that a priori generalizations about optimal outgroup taxon sampling strategies are likely to be misleading, and that testing for the suitability of available outgroup taxon sampling in specific instances is warranted. Software for optimal outgroup analysis is available.     

Mapping uncertainty and phylogenetic uncertainty in ancestral character state reconstruction: an example in the moss genus Brachytheciastrum

The evolution of species traits along a phylogeny can be examined through an increasing number of possible, but not necessarily complementary, approaches. In this paper, we assess whether deriving ancestral states of discrete morphological characters from a model whose parameters are (i) optimized by ML on a most likely tree; (II) optimized by ML onto each of a Bayesian sample of trees; and (III) sampled by a MCMC visiting the space of a Bayesian sample of trees affects the reconstruction of ancestral states in the moss genus Brachytheciastrum. In the first two methods, the choice of a single- or two-rate model and of a genetic distance (wherein branch lengths are used to determine the probabilities of change) or speciational (wherein changes are only driven by speciation events) model based upon a likelihood-ratio test strongly depended on the sampled trees. Despite these differences in model selection, reconstructions of ancestral character states were strongly correlated to each others across nodes, often at r > 0.9, for all the characters. The Bayesian approach of ancestral character state reconstruction offers, however, a series of advantages over the single-tree approach or the ML model optimization on a Bayesian sample of trees because it does not involve restricting model parameters prior to reconstructing ancestral states, but rather allows a range of model parameters and ancestral character states to be sampled according to their posterior probabilities. From the distribution of the latter, conclusions on trait evolution can be made in a more satisfactorily way than when a substantial part of the uncertainty of the results is obscured by the focus on a single set of model parameters and associated ancestral states. The reconstructions of ancestral character states in Brachytheciastrum reveal rampant parallel morphological evolution. Most species previously described based on phenetic grounds are thus resolved of polyphyletic origin. Species polyphylly has been increasingly reported among mosses, raising severe reservations regarding current species definition.     

EXAMINING TWO STANDARD ASSUMPTIONS OF ANCESTRAL RECONSTRUCTIONS: REPEATED LOSS OF DICHROMATISM IN DABBLING DUCKS (ANATINI)

Although phylogenetic reconstruction of ancestral character states is becoming an increasingly common technique for studying evolution, few researchers have assessed the reliability of these reconstructions. Here I test for congruence between a phylogenetic reconstruction and a widely accepted scenario based on independent lines of evidence. I used Livezey's (1991) phylogeny to reconstruct ancestral states of plumage dichromatism in dabbling ducks (Anatini). Character state mapping reconstructs monochromatic ancestors for the genus Anas as well as most of its main clades. This reconstruction differs strongly from the widely accepted scenario of speciation and plumage evolution in the group (e.g., Delacour and Mayr 1945; Sibley 1957). This incongruence may occur because two standard assumptions of character state reconstruction are probably not met in this case. Violating either of these two assumptions would be a source of error sufficient to create misleading reconstructions. The first assumption that probably does not apply to ducks is that terminal taxa, in this case species, are monophyletic. Many of the widespread dichromatic species of ducks may be paraphyletic and ancestral to isolated monochromatic species. Three lines of evidence support this scenario: population-level phylogenies, biogeography, and vestigial plumage patterns. The second assumption that probably does not apply to duck plumage color is that gains and losses of character states are equally likely. Four lines of evidence suggest that dichromatic plumage might be lost more easily than gained: weak female preferences for bright male plumage, biases toward the loss of sexually dichromatic characters, biases toward the loss of complex characters, and repeated loss of dichromatism in other groups of birds. These seven lines of evidence support the accepted scenario that widespread dichromatic species repeatedly budded off isolated monochromatic species. Drift and genetic biases probably caused the easy loss of dichromatism in ducks and other birds during peripatric speciation. In order to recover the accepted scenario using Livezey's tree, losses of dichromatism must be five times more likely than gains. The results of this study caution against the uncritical use of unordered parsimony as the sole criterion for inferring ancestral states. Detailed population-level sampling is needed and altered transformation weighting may be warranted in ducks and in many other groups and character types with similar attributes.     

The historical biogeography of Mammalia

Palaeobiogeographic reconstructions are underpinned by phylogenies, divergence times and ancestral area reconstructions, which together yield ancestral area chronograms that provide a basis for proposing and testing hypotheses of dispersal and vicariance. Methods for area coding include multi-state coding with a single character, binary coding with multiple characters and string coding. Ancestral reconstruction methods are divided into parsimony versus Bayesian/likelihood approaches. We compared nine methods for reconstructing ancestral areas for placental mammals. Ambiguous reconstructions were a problem for all methods. Important differences resulted from coding areas based on the geographical ranges of extant species versus the geographical provenance of the oldest fossil for each lineage. Africa and South America were reconstructed as the ancestral areas for Afrotheria and Xenarthra, respectively. Most methods reconstructed Eurasia as the ancestral area for Boreoeutheria, Euarchontoglires and Laurasiatheria. The coincidence of molecular dates for the separation of Afrotheria and Xenarthra at approximately 100 Ma with the plate tectonic sundering of Africa and South America hints at the importance of vicariance in the early history of Placentalia. Dispersal has also been important including the origins of Madagascar's endemic mammal fauna. Further studies will benefit from increased taxon sampling and the application of new ancestral area reconstruction methods.     

Inferring the ancestral sexuality and reproductive condition in sponges (Porifera)

Considerable diversity abounds among sponges with respect to reproductive and developmental biology. Their ancestral sexual mode (gonochorism vs. hermaphroditism) and reproductive condition (oviparity vs. viviparity) however remain unclear, and these traits appear to have undergone correlated evolution in the phylum. To infer ancestral traits and investigate this putative correlation, we used DNA sequence data from two loci (18S ribosomal RNA and cytochrome c oxidase subunit I) to explore the phylogenetic relationships of 62 sponges whose reproductive traits have been previously documented. Although the inferred tree topologies, using the limited data available, favoured paraphyly of sponges, we also investigated ancestral character‐state reconstruction on a phylogeny with constrained sponge monophyly. Both parsimony‐ and likelihood‐based ancestral state reconstructions indicate that viviparity (brooding) was the likely reproductive mode of the ancestral sponge. Hermaphroditism is favoured over gonochorism as the sexual condition of the sponge ancestor under parsimony, but the reconstruction is ambiguous under likelihood, rendering the ancestry of sexuality unresolved in our study. These results are insensitive to the constraint of sponge monophyly when tracing the reproductive characters using parsimony methods. However, the maximum likelihood analysis of the monophyletic hypothetical tree rendered gonochorism as ancestral for the phylum. A test of trait correlation unambiguously favours the concerted evolution of sexuality and reproductive mode in sponges (hermaphroditism/viviparity, gonochorism/oviparity). Although testing ecological hypotheses for the pattern of sponge reproduction is beyond the scope of our analyses, we postulate that certain physiological constrains might be key causes for the correlation of reproductive characters.     

Phylogeny,biogeography, and morphological ancestral character reconstruction in the Mediterranean genus Fumana (Cistaceae)

Fumana is a diverse genus of the Cistaceae family, consisting of 21 currently accepted species. In this study, nuclear (ITS) and plastid (matK, trnT‐L) molecular markers were used to reconstruct the phylogeny and to estimate divergence times, including 19 species of Fumana. Phylogenetic analyses (Bayesian Inference, Maximum Parsimony and Maximum Likelihood) confirmed the monophyly of Fumana and did not support the infrageneric divisions previously established. The results support four main clades that group species that differ in vegetative and reproductive characters. Given the impossibility to define morphological characters common to all species within the clades, our proposal is to reject infrageneric divisions. Molecular dating and ancestral area analyses provide evidence for a Miocene diversification of the genus in the north‐western Mediterranean. Ancestral state reconstructions revealed ancestral character states for some traits related to xeric and arid habitats, suggesting a preadaptation to the Mediterranean climate.     

Can higher‐level phylogenies of weevils explain their evolutionary success? A critical review

We review a series of related publications that combine higher‐level phylogenies of weevils (Coleoptera: Curculionoidea) with host plant information to explain the success of this megadiverse lineage in the context of a co‐evolutionary escape‐and‐radiation hypothesis. We argue that the authors' approach is marred by the cumulative effect of: (1) inadequate taxon sampling, particularly within the most diverse family Curculionidae; (2) insufficient reconciliation of systematic evidence, including the reassessment of morphological characters and necessary classificatory emendations; (3) exceedingly wide concepts of ecological similarity, leading to uninformative tests of adaptation; (4) insufficient resolution of the temporal sequence of associated weevil and angiosperm radiations; and (5) inadequate consideration of alternatives to the escape‐and‐radiation hypothesis. As a result, there are very few new and reliable inferences about the evolutionary success of weevils that depend precisely on the phylogenetic data presented in these studies. Improved taxon sampling alone is not the solution, because the existing mid‐level classification of weevils is too deficient to permit inferences about natural lineages and their ancestral traits. We therefore recommend abandoning such an approach in favour of more narrowly focused reconstructions of the evolutionary history of generic and tribal groupings.     

Plausibility of inferred ancestral phenotypes and the evaluation of alternative models of limb evolution in scincid lizards

Phylogenetic approaches to inferring ancestral character states are becoming increasingly sophisticated; however, the potential remains for available methods to yield strongly supported but inaccurate ancestral state estimates. The consistency of ancestral states inferred for two or more characters affords a useful criterion for evaluating ancestral trait reconstructions. Ancestral state estimates for multiple characters that entail plausible phenotypes when considered together may reasonably be assumed to be reliable. However, the accuracy of inferred ancestral states for one or more characters may be questionable where combined reconstructions imply implausible phenotypes for a proportion of internal nodes. This criterion for assessing reconstructed ancestral states is applied here in evaluating inferences of ancestral limb morphology in the scincid lizard clade Lerista. Ancestral numbers of digits for the manus and pes inferred assuming the models that best fit the data entail ancestral digit configurations for many nodes that differ fundamentally from configurations observed among known species. However, when an alternative model is assumed for the pes, inferred ancestral digit configurations are invariably represented among observed phenotypes. This indicates that a suboptimal model for the pes (and not the model providing the best fit to the data) yields accurate ancestral state estimates.     

How the worm got its pharynx: phylogeny, classification and Bayesian assessment of character evolution in Acoela

Acoela are marine microscopic worms currently thought to be the sister taxon of all other bilaterians. Acoels have long been used as models in evolutionary scenarios, and generalized conclusions about acoel and bilaterian ancestral features are frequently drawn from studies of single acoel species. There is no extensive phylogenetic study of Acoela and the taxonomy of the 380 species is chaotic. Here we use two nuclear ribosomal genes and one mitochondrial gene in combination with 37 morphological characters in an analysis of 126 acoel terminals (about one-third of the described species) to estimate the phylogeny and character evolution of Acoela. We present an estimate of posterior probabilities for ancestral character states at 31 control nodes in the phylogeny. The overall reconstruction signal based on the shape of the posterior distribution of character states was computed for all morphological characters and control nodes to assess how well these were reconstructed. The body-wall musculature appears more clearly reconstructed than the reproductive organs. Posterior similarity to the root was calculated by averaging the divergence between the posterior distributions at the nodes and the root over all morphological characters. Diopisthoporidae is the sister group to all other acoels and has the highest posterior similarity to the root. Convolutidae, including several "model" acoels, is most divergent. Finally, we present a phylogenetic classification of Acoela down to the family level where six previous family level taxa are synonymized.     

GROUNDPLANS AND EXEMPLARS: PATHS TO THE TREE OF LIFE

Abstract — During cladistic analysis of a diverse higher taxon it is impractical to code every species as a separate terminal. In such cases, workers proceed in one of two distinct ways: (1) examine a number of member species in order to deduce groundplan character states of the higher group before the analysis is begun, here called the intuitive method, or (2), code a number of real species belonging to the group as terminals in the analysis, called the exemplar method. Both methods have the same aim, to estimate the groundplan of the higher taxon concerned.
Both groundplan estimation methods will lead to identical results when the character in question has the same state in all members of the terminal group, however when the character has two or more states, the two methods may give different results. The precise methods employed in the intuitive approach have not been articulated in the literature, but possible techniques may result in non-parsimonious ancestral state assignments, even in simple cases.
Groundplan estimation in the exemplar method is an extension of parsimony. The exemplar method allows groundplan state/s at internal nodes to be calculated during tree search. In many cases the exemplar method assigns a number of possible states to the groundplan, and the state assignment is therefore equivocal. This is not a deficiency of the method but reflects the notion that the parsimony criterion alone cannot always distinguish a single state present in a hypothetical ancestor. The optimal choice of exemplars required to estimate the groundplan most efficiently is discussed under a simple and common hypothesis of character transformation. For complex character distributions up to three exemplars may be required, each from a separate lineage of the group close to its hypothetical common ancestral node.     

On phylogenetic tests of irreversible evolution

"Dollo's law" states that, following loss, a complex trait cannot reevolve in an identical manner. Although the law has previously fallen into disrepute, it has only recently been challenged with statistical phylogenetic methods. We employ simulation studies of an irreversible binary character to show that rejections of Dollo's law based on likelihood-ratio tests of transition rate constraints or on reconstructions of ancestral states are frequently incorrect. We identify two major causes of errors: incorrect assignment of root state frequencies, and neglect of the effect of the character state on rates of speciation and extinction. Our findings do not necessarily overturn the conclusions of phylogenetic studies claiming reversals, but we demonstrate devastating flaws in the methods that are the foundation of all such studies. Furthermore, we show that false rejections of Dollo's law can be reduced by the use of appropriate existing models and model selection procedures. More powerful tests of irreversibility require data beyond phylogenies and character states of extant taxa, and we highlight empirical work that incorporates additional information.     

Trends in morphological evolution in homobasidiomycetes inferred using maximum likelihood: a comparison of binary and multistate approaches

The homobasidiomycetes is a diverse group of macrofungi that includes mushrooms, puffballs, coral fungi, and other forms. This study used maximum likelihood methods to determine if there are general trends (evolutionary tendencies) in the evolution of fruiting body forms in homobasidiomycetes, and to estimate the ancestral forms of the homobasidiomycetes and euagarics clade. Character evolution was modeled using a published 481-species phylogeny under two character-coding regimes: additive binary coding, using DISCRETE, and multistate (five-state) coding, using MULTISTATE. Inferences regarding trends in character evolution made under binary coding were often in conflict with those made under multistate coding, suggesting that the additive binary coding approach cannot serve as a surrogate for multistate methods. MULTISTATE was used to develop a"minimal"model of fruiting body evolution, in which the 20 parameters that specify rates of transformations among character states were grouped into the fewest possible rate categories. The minimal model required only four rate categories, one of which is approaching zero, and suggests the following conclusions regarding trends in evolution of homobasidiomycete fruiting bodies: (1) there is an active trend favoring the evolution of pileate-stipitate forms (those with a cap and stalk); (2) the hypothesis that the evolution of gasteroid forms (those with internal spore production, such as puffballs) is irreversible cannot be rejected; and (3) crustlike resupinate forms are not a particularly labile morphology. The latter finding contradicts the conclusions of a previous study that used binary character coding. Ancestral state reconstructions under binary coding suggest that the ancestor of the homobasidiomycetes was resupinate and the ancestor of the euagarics clade was pileate-stipitate, but ancestral state reconstructions under multistate coding did not resolve the ancestral form of either node. The results of this study illustrate the potential sensitivity of comparative analyses to character state definitions.     

Congruence between comparative morphology and molecular phylogenies: the final stage of evolution of the skeletal characters of male genitalia in the subtribe Polyommatina (Lepidoptera,Lycaenidae). Part 2. Uncus and subunci

The morphology of the male terminalia (uncus and subunci) was studied in 39 species of the subtribe Polyommatina (Lycaenidae). Traces of nine established characters were mapped on the molecular phylogeny of the subtribe proposed by Talavera et al. (2013). The ancestral character states for these morphological structures were established in Plebejus s. l. and Polyommatus s. l. According to the time calibration of the proposed molecular tree, the studied skeletal structures (uncus and subunci) evolved very slowly within the last million years. It was shown that the similar shape of the uncus and subuncus branches arose independently and underwent parallel morphological transformations. In particular, wide and, as a rule, ventrally directed uncus lobes arose independently in Polyommatus s. str., Alpherakya, Glabroculus, and Aricia. Yet, in various evolutionary lines of Polyommatina similar changes in the length ratio of the proximal and distal parts of the subunci as well as in the shape of their apical hooks were observed. The character states marking the groups Polyommatus s. str. and Aricia were established. The evolutionary changes in the uncus morphology were highly non-uniform in the various monophyletic lines of Polyommatina. As a result, representatives of some “old” lines have more specialized features of the uncus morphology in comparison with those belonging to “young” lines that retain ancestral character states. In Polyommatina, the transformation of the male terminalia was directed toward development of the most effective mechanism of female fixation during copulation. This goal was reached in similar ways in various evolutionary lines of Polyommatina, which explains numerous parallelisms in morphology of these structures.     

Reverse evolution of fitness in Drosophila melanogaster

Abstract The evolution of fitness is central to evolutionary theory, yet few experimental systems allow us to track its evolution in genetically and environmentally relevant contexts. Reverse evolution experiments allow the study of the evolutionary return to ancestral phenotypic states, including fitness. This in turn permits well‐defined tests for the dependence of adaptation on evolutionary history and environmental conditions. In the experiments described here, 20 populations of heterogeneous evolutionary histories were returned to their common ancestral environment for 50 generations, and were then compared with both their immediate differentiated ancestors and populations which had remained in the ancestral environment. One measure of fitness returned to ancestral levels to a greater extent than other characters did. The phenotypic effects of reverse evolution were also contingent on previous selective history. Moreover, convergence to the ancestral state was highly sensitive to environmental conditions. The phenotypic plasticity of fecundity, a character directly selected for, evolved during the experimental time frame. Reverse evolution appears to force multiple, diverged populations to converge on a common fitness state through different life‐history and genetic changes.