Circularity,evolution, systematics … and circularity

Many have argued strongly that incorporation of evolutionary theory into systematics is dangerously circular, while others have maintained that such an integrated approach increases the accuracy of phylogenetic inference. Here, it is demonstrated that such blanket statements regarding exclusion or inclusion of evolutionary principles in systematics fail to distinguish between two very different types of principles. ‘Phylogeny-neutral’ evolutionary principles are those inferred without any recourse to specific phylogenetic hypotheses (e.g. via developmental genetics, biomechanics). In contrast, ‘phylogeny-dependent’ principles are those which can only be inferred on the basis of specific phylogenetic hypotheses (e.g. character associations detected via ‘comparative methods’). Inclusion of phylogeny-neutral principles in systematic studies as a priori assumptions can be justified, since these principles have (often strong) external empirical support from other spheres of investigation. However, inclusion of phylogeny-dependent principles in systematic studies is circular, since such principles have no external empirical support but are themselves derived from systematic studies. Advocating inclusion or exclusion of all (or as many as possible) evolutionary principles from phylogenetic analysis is therefore misguided. Rather, phylogeny-neutral principles are independently supported and can be included, while phylogeny-dependent principles are unjustified assumptions and should be excluded to avoid circularity. However, integration of complex phylogeny-neutral principles in systematics can create operational problems, even though there are no methodological reasons against their inclusion.     

Phylogenetic interpretation of ontogenetic change: sorting out the actual and artefactual in an empirical case study of centrarchid fishes

Hypothesized relationships between ontogenetic and phylogenetic change in morphological characters were empirically tested in centrarchid fishes by comparing observed patterns of character development with patterns of character evolution as inferred from a representative phylogenetic hypothesis. This phylogeny was based on 56–61 morphological characters that were polarized by outgroup comparison. Through these comparisons, evolutionary changes in character ontogeny were categorized in one of eight classes (terminal addition, terminal deletion, terminal substitution, non-terminal addition, non-terminal deletion, non-terminal substitution, ontogenetic reversal and substitution). The relative frequencies of each of these classes provided an empirical basis from which assumptions underlying hypothesized relationships between ontogeny and phylogeny were tested. In order to test hypothesized relationships between ontogeny and phylogeny that involve assumptions about the relative frequencies of terminal change (e.g. the use of ontogeny as a homology criterion), two additional phylogenies were generated in which terminal addition and terminal deletion were maximized and minimized for all characters. Character state change interpreted from these phylogenies thus represents the maxima and minima of the frequency range of terminal addition and terminal deletion for the 8.7 × 10³⁶ trees possible for centrarchids. It was found for these data that terminal change accounts for c. 75% of the character state change. This suggests either that early ontogeny is conserved in evolution or that interpretation and classification of evolutionary changes in ontogeny is biased in part by the way that characters are recognized, delimited and coded. It was found that ontogenetic interpretation is influenced by two levels of homology decision: an initial decision involving delimitation of the character (the ontogenetic sequence), and the subsequent recognition of homologous components of developmental sequences. Recognition of phylogenetic homology among individual components of developmental sequences is necessary for interpretation of evolutionary changes in ontogeny as either terminal or non-terminal. If development is the primary criterion applied in recognizing individual homologies among parts of ontogenetic sequences, the only possible interpretation of phylogenetic differences is that of terminal change. If homologies of the components cannot be ascertained, recognition of the homology of the developmental sequence as a whole will result in the interpretation of evolutionary differences as substitutions. Particularly when the objective of a study is to discover how ontogeny has evolved, criteria in addition to ontogeny must be used to recognize homology. Interpretation is also dependent upon delimitation within an ontogenetic sequence. This is in part a function of the way that an investigator ‘sees’ and codes characters. Binary and multistate characters influence interpretation differently and predictably. The use of ontogeny for determining phylogenetic polarity as previously proposed rests on the assumptions that ancestral ontogenies are conserved and that character evolution occurs predominantly through terminal addition. It was found for these data that terminal addition may comprise a maximum of 51.9% of the total character state change. It is concluded that the ontogenetic criterion is not a reliable indicator of phylogenetic polarity. Process and pattern data are collected simultaneously by those engaged in comparative morphological studies of development. The set of alternative explanatory processes is limited in the process of observing development. These form necessary starting points for the research of developmental biologists. Separating ‘empirical’ results from interpretational influences requires awareness of potential biases in the course of character selection, coding and interpretation. Consideration of the interpretational problems involved in identifying and classifying phylogenetic changes in ontogeny leads to a re-evaluation of the purpose, usefulness and information conveyed by the current classification system. It is recommended that alternative classification schemes be pursued.     

Cross-Testing Adaptive Hypotheses: Phylogenetic Analysis and the Origin of Bird Flight

Adaptive scenarios in evolutionary biology have always beenbased on incremental improvements through a series of adaptivestages. But they have often been justified by appeal to assumptionsof how natural selection must work or by appeal to optimalityarguments or notions of evolutionary process. Cladistic methodology,though it cannot logically falsify hypotheses of process, provideshypotheses of evolutionary pattern independent of other considerationsand so provides a useful test of consilience with genealogy.I illustrate the cross-test of hypotheses of the evolution ofseveral functions and adaptations related to the origin of birdflight with independently derived phylogenetic analysis. Consiliencedoes not support ideas that the close ancestors of birds werearboreal or evolved flight from the trees, nor that they werephysiologically intermediate between typical reptiles and livingbirds, nor that feathers evolved for flight. Rather, the ancestorsof birds were terrestrial, they were fast-growing, active animals,and the original functions of feathers were in insulation andcoloration.     

Models of parent-offspring conflict. IV. Suppression: Evolutionary retaliation by the parent

We have earlier analysed ESSs for the amount of parental investment (PI) that offspring are expected to solicit from their parents, given that parents acquiesce to offspring demands. The present paper considers evolutionary retaliation by the parent for species where only one parent provides PI. Two genetic loci are envisaged: one (the ‘conflictor’ locus) determines the extent of offspring solicitation; the other (the ‘suppressor’ locus) determines how parents retaliate. Solicitation is assumed to carry a cost which may affect a particular offspring uniquely if time and energy are the major costs, or may affect all offspring in a brood equally if the main cost is predation risk. Two kinds of parental retaliation are possible. Parents may supply PI in proportion to offspring demands, or may ignore solicitation altogether and give a fixed PI. Analytical models of conflict in which the parent supplies PI in proportion to solicitation yield pure ESSs with PI at a compromise level between parent and offspring interests. These are termed ‘pro rata’ ESSs. Where solicitation costs are high, an ‘offspring wins’ ESS (offspring get all they ‘want’) is possible especially for forms of conflict that affect future sibs, and a ‘parent wins’ ESS (parent supplies its optimum) is possible especially for conflict that affects contemporary sibs. When parental retaliation takes the form of ignoring offspring solicitation, this can lead to a ‘parent wins’ ESS if costs of ignoring solicitation are negligible, but where parental insensitivity carries costs, the result is an unresolvable evolutionary chase with cycling frequencies of alleles coding for parent and offspring strategies. ‘Pro rata’ ESSs cannot be invaded by ‘ignore solicitation’ mutants but ‘pro rata’ mutants can often invade at certain stages in ‘ignore solicitation’ limit cycles. We therefore conclude that the probable evolutionary end product for most species will be the ‘pro rata’ ESS in which the parent supplies more PI than would be optimal in the absence of conflict, but less PI than would be an ESS for the offspring in the absence of parental retaliation. Such ESSs will be characterized by solicitation costs; offspring will ‘ask’ for more PI than they get. In nature, under similar conditions, highest conflict will occur when both parents sustain equally the effects of conflict, or when conflict affects contemporary rather than future sibs.     

Investigating the evolutionary effects of one feature on another: does muscle spread suppress caudal autotomy in lizards?

Hypotheses of secondary evolutionary change, where alteration in a particular feature is thought to result in change in another, can be tested in two main ways. First, phylogenies can be used to identify separate cases where one of the features changes and each case can then be examined to see whether the other change also actually takes place and if the perceived sequence of the alterations is appropriate. Secondly, the mechanism by which change in the second feature is supposed to be effected can be scrutinized and, in some cases, subjected to experimental investigation.
This approach was applied to a recent hypothesis, that backward spread of the caudifemoralis longus muscle in the tail base of lizards was the primary cause of loss of capacity to autotomize the tail. Some 23 to 25 independent cases of total autotomy loss in adult lizards were identified. In all but six of these there was no substantial spread of the muscle. In two of the remainder, the muscle appears to have spread ufiev autotomy loss, and another case cannot be tested properly as information about relationships is equivocal. The final three cases exhibit extension of the caudifemoralis longus before autotomy loss, but the latter is not found in related species that also inherit muscle extension, which suggests that other causal factors may be involved. In about 15 other cases, where autotomy becomes restricted to the tail base, there is no marked spread of the caudifemoralis longus. The proposed functional link between muscle extension and autotomy loss is also discussed and discounted     

Phylogenetic analyses of the genus Aeromonas based on housekeeping gene sequencing and its influence on systematics

The phylogenies derived from housekeeping gene sequence alignments, although mere evolutionary hypotheses, have increased our knowledge about the Aeromonas genetic diversity, providing a robust species delineation framework invaluable for reliable, easy and fast species identification. Previous classifications of Aeromonas, have been fully surpassed by recently developed phylogenetic (natural) classification obtained from the analysis of so‐called ‘molecular chronometers’. Despite ribosomal RNAs cannot split all known Aeromonas species, the conserved nature of 16S rRNA offers reliable alignments containing mosaics of sequence signatures which may serve as targets of genus‐specific oligonucleotides for subsequent identification/detection tests in samples without culturing. On the contrary, some housekeeping genes coding for proteins show a much better chronometric capacity to discriminate highly related strains. Although both, species and loci, do not all evolve at exactly the same rate, published Aeromonas phylogenies were congruent to each other, indicating that, phylogenetic markers are synchronized and a concatenated multigene phylogeny, may be ‘the mirror’ of the entire genomic relationships. Thanks to MLPA approaches, the discovery of new Aeromonas species and strains of rarely isolated species is today more frequent and, consequently, should be extensively promoted for isolate screening and species identification. Although, accumulated data still should be carefully catalogued to inherit a reliable database.     

Genesis of phenotypic and genotypic diversity in land plants: The present as the key to the past

The evolutionary history of vascular plants is reviewed by extrapolation back through time from a wide range of data recently derived from the present flora, using as the central theme evolutionary inferences gained from phylogenies reconstructed as cladograms. Any region of the genome can be used to infer relationships, but only a combination of knowledge of morphology and the developmental genes that underpin morphology can allow evolutionary interpretation of macroevolutionary transitions; this in turn is necessary to identify bona fide evolutionary radiations and any putative causal key innovations. Such studies require clades to be delimited not by the inclusion of particular extant ‘crown’ species but rather by specific apo‐morphies, thereby giving important phylogenetic roles to extinct as well as extant species. Dating phylogenetic divergences via molecular clocks remains seriously inaccurate, and ultimately relies primarily on fossil benchmarks. First principles suggest that evolution of most regions of the genome is fundamentally gradual, whereas evolution of regions especially prone to strong selection pressure, and of the many facets of the phenotype, is punctuational, being characterized through time dominantly by stasis. Sequence data have proved valuable for inferring monophyletic groups, but within the now widely accepted context of monophyly the taxonomic hierarchy should primarily reflect degrees of morphological rather than molecular divergence. Incongruence among contrasting data sets is best explained by understanding the biological constraints operating on each type of phylogenetic information. The conventional ‘uniformitarian’ view of evolution has only limited applicability as one traces the history of land plants through time. Diversity increased in stepwise fashion, reflecting either attainments of complexity and/or fitness thresholds by the lineage (intrinsic) or the availability of unusually permissive environments, often following major perturbations (extrinsic). The Quaternary period demonstrates especially well the resilience, and ease of migration, of the Earth's vegetation. A higher frequency of generation of novel phenotypes in the deep past is possible, but a far higher frequency of their establishment is certain; together, these factors generate an evolutionary pattern of nested radiations that is fractal, as saturation of the resource space rendered the environment decreasingly permissive through time. In the immediate future, evolutionary‐developmental genetics will have increasing value for testing homology, interpreting homoplasy and elucidating evolutionary constraints, and will become easier to pursue as whole‐genome sequences of additional ‘model’ species further invigorate comparative genomics. Complexity of gene regulation, both by other genes and by the cellular and extra‐cellular environment, appears a particularly fruitful area for further research. Nonetheless, environmental filtering of evolutionary novelties (whether instantaneously isolated mutant ‘prospecies’ or classic neoDarwinian ‘selfish genes’ selectively spreading through panmictic populations) can only be effectively understood by longer term monitoring of populations in the wild, to better capture rare evolutionary and ecological events and to better assess the efficacy of traditional microevolutionary processes. We believe that the resulting renaissance in macroevolutionary studies will encourage a broader systematic perspective ‐ one that better encompasses the remarkable diversity of evolutionary processes that together generated the present diversity of life.     

Is specialization an evolutionary dead end? Testing for differences in speciation,extinction and trait transition rates across diverse phylogenies of specialists and generalists

Specialization has often been claimed to be an evolutionary dead end, with specialist lineages having a reduced capacity to persist or diversify. In a phylogenetic comparative framework, an evolutionary dead end may be detectable from the phylogenetic distribution of specialists, if specialists rarely give rise to large, diverse clades. Previous phylogenetic studies of the influence of specialization on macroevolutionary processes have demonstrated a range of patterns, including examples where specialists have both higher and lower diversification rates than generalists, as well as examples where the rates of evolutionary transitions from generalists to specialists are higher, lower or equal to transitions from specialists to generalists. Here, we wish to ask whether these varied answers are due to the differences in macroevolutionary processes in different clades, or partly due to differences in methodology. We analysed ten phylogenies containing multiple independent origins of specialization and quantified the phylogenetic distribution of specialists by applying a common set of metrics to all datasets. We compared the tip branch lengths of specialists to generalists, the size of specialist clades arising from each evolutionary origin of a specialized trait and whether specialists tend to be clustered or scattered on phylogenies. For each of these measures, we compared the observed values to expectations under null models of trait evolution and expected outcomes under alternative macroevolutionary scenarios. We found that specialization is sometimes an evolutionary dead end: in two of the ten case studies (pollinator‐specific plants and host‐specific flies), specialization is associated with a reduced rate of diversification or trait persistence. However, in the majority of studies, we could not distinguish the observed phylogenetic distribution of specialists from null models in which specialization has no effect on diversification or trait persistence.     

DOLLO'S LAW AND THE IRREVERSIBILITY OF DIGIT LOSS IN BACHIA

Several recent studies conclude that exceptions to Dollo's law are more common than used to be thought. If the claims are true this would change our view on the role of developmental constraints in the evolution of body plans. One study claims the reevolution of lost digits in the lizard genus Bachia ( Kohlsdorf and Wagner 2006 ). We evaluate this claim. We conclude that the proposed molecular phylogenetic tree is in conflict with evolutionary mechanisms concerning the biogeography of lizards and with morphology‐based phylogenies. A reanalysis of the molecular data does not support the topology of the published tree. Furthermore, two implicit assumptions, that digit numbers are fixed and that polydactyly evolves independently from other characters, are incorrect. We conclude that there is no convincing support for reevolution of digits in Bachia. We discuss our findings in the light of the current evidence for the reversal of losses of complex traits. We conclude that in metazoans, exceptions to Dollo's law are mainly found among meristic traits that originate relatively late during embryogenesis, when developmental systems are more compartmentalized. Finally, our study shows that phylogenetic analyses should incorporate evolutionary mechanisms including constraints, variation, and selection, not only for correct phylogenetic reconstruction, but also for correct evolutionary inference.     

THE HETEROMORPHS AND AMMONOID EXTINCTION

The heteromorph ammonoids are quoted as a favourite example of degeneration and the decline of a Bauplan‘condemned’ to extinction. With astonishing tenacity this view of the heteromorphs as ‘phylogenetic end-forms’ has embedded itself in the palaeontological literature and is still current. This is contradicted by the most recent investigations, directed especially at the Cretaceous heteromorphs, which necessitate correction of the typolysis concept as well as modification of the most uncontested of the phylogenetic ‘laws’, Dollo's ‘law of irreversibility’. Contrary to the usual textbook hypothesis, the heteromorphs return in several evolutionary lineages to normal coiling of the shell and, in general, to a phylogenetically older type of suture line. At the same time these results encourage fresh reflexion on possible exogenous causes of phylogenetic extinction of the ammonoids. A clear causal connexion exists between this extinction and the far-reaching epirogenic changes in sea level in the late Cretaceous; cosmic explanations are unnecessary. In conclusion it may be added that the precipitate formulation of phylogenetic ‘laws’ and ‘principles’ based on too little basic information has encumbered this branch of palaeontology with a stifling set of prejudices rather than providing it with guide lines crystallized from long experience and observation. It is vitally necessary in the interests of palaeontology that interpretation and observation be separated far more than has been the case in the past.     

CONDUCTING PHYLOGENETIC COMPARATIVE STUDIES WHEN THE PHYLOGENY IS NOT KNOWN

A method is proposed to conduct phylogenetic analyses of comparative or interspecific data when the true phylogeny is not known. Standard models of speciation and/or extinction or other methods are used to generate a sample from the set of all possible phylogenies for the measured species. The comparative data are then analyzed on each of the possible trees to obtain a distribution of possible evolutionary statistics for these data. The mean of this distribution is proposed as a reasonable estimate of the true evolutionary statistic of interest. Ways of obtaining confidence intervals and of developing hypothesis tests for this mean statistic are also proposed. The method can be used with any comparative method or phylogenetic analysis technique when phylogenetic relationships among species are not known or when branch lengths for a phylogeny in units of expected character change (as required by most methods) are not available. Computer programs to conduct the analyses are available on request.     

EVOLUTIONARY CHARACTER ANALYSIS: TRACING CHARACTER CHANGE ON A CLADOGRAM

Abstract— There has been little formal discussion concerning character analysis in cladistics, even though characters and their character state trees are central to phylogenetic analyses. We refer to this field as Evolutionary Character Analysis. This paper defines the components of evolutionary character analysis: character state trees, transmodal characters, cladogram characters, attribute and character phylogenies; and the use of these components in phylogenetic inference and evolutionary studies. Character state trees and their effect on cladogram construction are discussed. A new method for numerically coding complex character state trees is described that further reduces the number of variables required to describe them. This method, ordinal coding, reduces the size of data matrices, and facilitates retrieval of state codes. This paper advocates the use of both biological evidence and evidence internal to the cladogram itself to construct character state trees (CSTs). We discuss general models of character evolution (morphocline analysis, Fitch minimum mutation model, etc.) and their role in forming CSTs. Character state trees formed with theories of character evolution are referred to as transmodal characters. These transmodal characters are contrasted with cladogram characters (Mickevich, 1982), and the place of each in a phylogenetic analysis is discussed. The method for determining cladogram characters is detailed with more complicated examples than found in previous publications. We advocate testing transmodal characters by comparing them with the resultant cladogram characters. This comparison involves transformation series analysis (TSA; Mickevich, 1982) which is viewed as an extension of reciprocal illumination. The TSA procedure and its place in hypothesis testing are reviewed. Tracing the evolution of characters interests both systematists and non-systematists alike. When character state trees (transmodal characters) are optimized on pre-existing phylogenies, character phylogenies and attribute phylogenies result. Attributes are defined as a feature that may or may not be homologous (i.e., ecological categories, plant hosts, etc.). We provide two illustrations of this approach, one involving the evolution of the anuran ear and another involving the coevolution of the butterfly Heliconius and its hostplants. Finally, the components of phylogenetic character analysis can be used to test more general evolutionary theories such as the biogenetic law and vicariance biogeography.     

The phylogeny of gutierrezia: An eclectic approach

One approach to the problem of deducing the genealogy of a set of organisms is to propose several hypotheses using different procedures, based on different evolutionary inferences. Such an approach was followed here, and four different phylogenies were constructed, three of them computer built. Consistency with independently obtained phenetic, cytological, and phytogeographical data was used to select the most probable phylogenetic tree among the four. It is shown that the most probable tree is one constructed under the assumption that character states found close to the mean and/or modal values for the genus are primitive. It is also shown that certain phylogenetic conclusions obtain in all four phylogenies.     

A Phylogenetic Analysis of the Evolution of the Stridulatory Apparatus in True Crickets (Orthoptera, Grylloidea)

The stridulatory apparatus (or stridulum) is currently assumed ancestral in crickets. Models of its subsequent evolution consider only one modality of evolutionary change: the stridulum would have been progressively lost in multiple cricket lineages. A phylogenetic test of this hypothesis is presented here. The morpho-functional types of stridulum have been optimized on the cladistic phylogenies of two monophyletic cricket clades, and parsimonious evolutionary scenarios of the evolution of the stridulum in these clades have been derived. The phylogenetic patterns thus obtained support the hypothesis that the stridulum has been lost several times convergently in crickets. They indicate, however, that the loss of the stridulum could be reversible, and that several modalities of evolutionary change exist for the stridulum. Phylogenetic analysis thus reveals an unsuspected complexity in the evolution of acoustic communication in crickets.     

Limitations of Metazoan 18S rRNA Sequence Data: Implications for Reconstructing a Phylogeny of the Animal Kingdom and Inferring the Reality of the Cambrian Explosion

We document the phylogenetic behavior of the 18S rRNA molecule in 67 taxa from 28 metazoan phyla and assess the effects of among-site rate variation on reconstructing phylogenies of the animal kingdom. This empirical assessment was undertaken to clarify further the limits of resolution of the 18S rRNA gene as a phylogenetic marker and to address the question of whether 18S rRNA phylogenies can be used as a source of evidence to infer the reality of a Cambrian explosion. A notable degree of among-site rate variation exists between different regions of the 18S rRNA molecule, as well as within all classes of secondary structure. There is a significant negative correlation between inferred number of nucleotide substitutions and phylogenetic information, as well as with the degree of substitutional saturation within the molecule. Base compositional differences both within and between taxa exist and, in certain lineages, may be associated with long branches and phylogenetic position. Importantly, excluding sites with different degrees of nucleotide substitution significantly influences the topology and degree of resolution of maximum-parsimony phylogenies as well as neighbor-joining phylogenies (corrected and uncorrected for among-site rate variation) reconstructed at the metazoan scale. Together, these data indicate that the 18S rRNA molecule is an unsuitable candidate for reconstructing the evolutionary history of all metazoan phyla, and that the polytomies, i.e., unresolved nodes within 18S rRNA phylogenies, cannot be used as a single or reliable source of evidence to support the hypothesis of a Cambrian explosion. Received: 9 December 1997 / Accepted: 23 March 1998     

The phylogenetic affinities of the Socotra Bunting Emberiza socotrana

The monophyly of the African ‘brown bunting’ complex was corroborated by a recent molecular study. However, the little-known Socotran endemic Emberiza socotrana, which is morphologically similar to the other taxa in this complex, was not included. Here we present a hypothesis of the phylogenetic relationships of the Socotra Bunting based on one mitochondrial gene and one nuclear intron. We found the Socotra Bunting to be deeply nested within the African ‘brown bunting’ complex and, although morphologically most similar to E. capensis, it proved to be more closely related to the E. striolata/sahari and E. tahapisi/goslingi species groups. The phylogenetic uniqueness of the Socotra Bunting underpins once more the evolutionary importance of the Endemic Bird Area of Socotra, which is often considered the ‘Galápagos of the Indian Ocean’.     

Evolutionary history shapes patterns of mutualistic benefit in Acacia–rhizobial interactions

The ecological and evolutionary factors that drive the emergence and maintenance of variation in mutualistic benefit (i.e., the benefits provided by one partner to another) in mutualistic symbioses are not well understood. In this study, we evaluated the role that host and symbiont phylogeny might play in determining patterns of mutualistic benefit for interactions among nine species of Acacia and 31 strains of nitrogen‐fixing rhizobial bacteria. Using phylogenetic comparative methods we compared patterns of variation in mutualistic benefit (host response to inoculation) to rhizobial phylogenies constructed from housekeeping and symbiosis genes; and a multigene host phylogeny. We found widespread genotype‐by‐genotype variation in patterns of plant growth. A relatively large component of this variation (21–28%) was strongly influenced by the interacting evolutionary histories of both partners, such that phylogenetically similar host species had similar growth responses when inoculated with phylogenetically similar rhizobia. We also found a relatively large nonphylogenetic effect for the average mutualistic benefit provided by rhizobia to plants, such that phylogenetic relatedness did not predict the overall benefit provided by rhizobia across all hosts. We conclude that phylogenetic relatedness should frequently predict patterns of mutualistic benefit in acacia‐rhizobial mutualistic interactions; but that some mutualistic traits also evolve independently of the phylogenies.     

Are Polyphaga (Coleoptera) really a basal neopteran lineage – a reply to Kazantsev

In a study on the mandible and mandibular articulation of larvae of the lycid genus Platerodrilus Kazantsev proposes a phylogenetic scheme with Polyphaga as a basal group of Neoptera and Lycidae as a basal group within Polyphaga. Here we point out different problems with his interpretation. The taxon sampling was not sufficient. The characters of endopterygote larvae cannot be compared to characters of adults in a phylogenetic context. The neotenic characters of female and adult male Lycidae are not sufficiently taken into account. A phylogenetic hypothesis should be based on multiple character systems and all available data must be considered. Kazantsev based his conclusions on a single isolated character complex. His hypothesis is in deep conflict with a phylogeny based on the molecular data, which clearly show that Lycidae are nested within Elateroidea. The molecular and morphological evidence also implies that females are aberrant neotenic forms and by no means ‘primitive’. Kazantsev's hypothesis is problematic because the presented data are insufficient and the character evaluation is not based on a numerical analysis.     

Ernst Haeckel (1834–1919) and the monophyly of life

Ernst Haeckel, who first introduced the term ‘monophyly’ into the biological literature, has in the past been appealed to in adjudication of the modern use of that concept. A contextual analysis of his writings reveals an inconsistent use of the term ‘monophyly’ by Haeckel. Morphological phylogeny was decoupled in Haeckel’s thinking from the evolutionary history of taxa. Monophyly could mean the derivation of one taxon from another, ancestral one, where these taxa could be species or of supraspecific rank. Monophyly could also mean the phylogenetic differentiation of a diversity of organismal ‘forms’ (morphologies) from a common primitive ‘form’ (morphological stage). And finally, monophyly, as also polyphyly, could apply to the origin of specific anatomical structures, in which case the monophyly/polyphyly of anatomical structures needed not to correlate with the monophyly/polyphyly of the taxon characterized by these structures. With respect to the issue of the unity and reality of monophyletic taxa, Haeckel’s writings again are indeterminate as is his stance on the monophyletic origin of life.