Zur Anwendung der Hennigschen Methode in der Wirbeltierpaläontologie

The application of Hennig’s theory on mere fossil groups is being discussed on the example of different primitive tetrapods. It is being demonstrated that a genealogical reconstruction in Hennig’s sense is biased by the possibility of great error, the reasons being: a) The insufficient fossil record and the resulting meagreness of usuable characters. b) Hennig’s theory does not offer any new ideas to solve the basic problems of phylogeny (parallelism, direction of evolution). Cladistic analysis biased by these insufficiencies should be supported by anagenetic investigations, i. e. by functional morphology. Hennig’s methodology, however, should be applied in cladistic reconstruction, since it works on logic reasonings and demands transparent documentation.     

Willi Hennig’s dichotomization of nature

Two formal assumptions implied in Willi Hennig’s “phylogenetic systematics” were repeatedly criticized for not being biologically grounded. The first is that speciation is always dichotomous; the second is that the stem‐species always goes extinct when its lineage splits into two daughter species. This paper traces the theoretical roots of Hennig’s “principle of dichotomy”. While often considered merely a methodological principle, Hennig’s realist perspective required him to ground the “principle of dichotomy” ontologically in speciation. As a methodological principle, the adherence to a strictly dichotomously structured phylogenetic system allowed Hennig to be unequivocal in character analysis and precise in the rendition of phylogenetic relationships. The ontological grounding of the “principle of dichotomy” in speciation remains controversial, however. This has implications for the application of techniques of phylogeny reconstruction to populations of bisexually reproducing organisms (phylogeography). Beyond that, the “principle of dichotomy” has triggered an intensive debate with respect to phylogeny reconstruction at the prokaryote level. © The Willi Hennig Society 2010.     

From types to individuals: Hennig’s ontology and the development of phylogenetic systematics

Contemporary phylogenetic systematics was framed, in part, as a response to a resurgent idealistic morphology in the German‐speaking world in the first half of the 20th century. There were also conceptual and methodological challenges from Anglo‐American researchers who were sceptical about whether a phylogenetic approach to systematics could be made to work. This paper describes these challenges as a way of providing context for some ontological innovations made first by Walter Zimmermann and then by Willi Hennig. The principal argument of this paper is that what has become known as the individuality thesis played a much more important role in the conceptual foundations of Hennig’s version of phylogenetic systematics than has been widely appreciated. Understanding Hennig’s ontology illuminates his responses to objections to phylogenetic systematics from both sides of the Atlantic and sheds substantial light on the extinction part of the dichotomy rule. Although many have taken Hennig’s claim that parent species go extinct at speciation to be an arbitrary and biologically unrealistic rule, extinction of the parent follows directly from the way Hennig understands species and how they are individuated. © The Willi Hennig Society 2011.     

From Haeckel’s phylogenetics and Hennig’s cladistics to the method of maximum likelihood: Advantages and limitations of modern and traditional approaches to phylogeny reconstruction

The maximum likelihood and Bayesian methods are based on parametric models of character evolution. They assume that if we know these models as well as distribution of character states in studied organisms, we can infer the probability of different phylogenetic trajectories leading from ancestors to modern forms. In fact, these methods are mathematized variants of the traditional Haeckel’s approach to phylogeny reconstruction. In contrast to classical and parsimonious cladistics, they infer phylogenies without such limitations as necessity of strictly dichotomous evolution, exclusion of plesiomorphic characters, and acceptance of only holophyletic taxa. They assume that evolution may be reticulated, any homologous characters—both apomorphic and plesiomorphic—can be used for inferring phylogenies, and interpretation of evolutionary lineages as taxa is optional. Thus, the main difference between the new and more traditional approaches to phylogeny reconstruction lies not in the characters used (molecular or morphological) but in the methodology of analysis. It must be admitted that a revolution began in phylogenetics 10–20 years ago. However, the fundamental changes in phylogenetics have been carried out so calmly and neatly by the people who started this revolution, that many systematists still do not realize their importance.     

Grundsätze der phylogenetischen Systematik (Eine praxisorientierte Übersicht)

The essential elements of phylogenetic systematics in the sense of Hennig are emphasized: The search for synapomorphies based on a special method of comparative morphology, and the aim of an exclusive use of synapomorphies for kinship proof and the basis of systematics. Special aspects of comparative morphology are: “Directed comparisons” steady reciprocal reflection between comparative morphological result and the system methodical efforts for the realization of distinctive details, comprehensive documentation and functional interpretation. This is equally true for recent and fossil forms. Most suitable for the method (in the sense defined above) are groups with numerous differentiated morphological characters, which can also be preserved in the fossil state. The less this is the case the less is the chance for achieving necessary numbers of well proven synapomorphies. Even so, it is not permitted—for those who want to perform phylogenetic systematics in the sense of Hennig—to use convergences, parallelisms or symplesiomorphies in the sense of “synapomorphies” as phylogenetic arguments for kinship relations. Numerous examples and diagrams demonstrate the methodological proceeding, and differences towards other methods of phylogenetical reconstruction and interpretation. Special attention is paid to direct and indirect conclusions drawn from fossils: Time of origin of characters, stem groups and *groups; predictions concerning the appearance (set of characters) of fossils and simultaneous existence of “neighbour groups” (sister groups, and more distantly related taxa).     

On some principles of taxonomy

In eukaryotes, in contrast to prokaryotes, phyletic lineages are usually quite distinct. Therefore, the best classifications of eukaryotes are usually phylogeny-based. However, in many groups of organisms, higher rank taxa are based on horizontal rather than phyletic groups or, more precisely, on groups of the mixed type. This is largely true for vertebrates where the division into fishes and tetrapods or into anamniotes (nonamniotes) and amniotes is just of the mixed type. Frequent parallelisms in these cases make the strict adherence to the principle of monophyly senseless and imply a compromise system. Strict cladistic practice violates this approach and ignores Hennig’s rule that his methodology should only be applied to synchronous organisms.     

Othenio Abel (1875–1946) and “the phylogeny of the parts”1

The reconstruction of the evolutionary history of animal phyla was an integral part of Othenio Abel’s paleobiology (paleozoology). Abel took issue with those phylogeneticists who, following the lead of Haeckel, would draw up phylogenetic trees on the basis of transformation series of singular characters considered to be of particular importance. Abel highlighted Louis Dollo’s principle of the chevauchement des spécialisations (crossing of specializations), which transformed phylogenetics from a search for ancestor–descendant sequences to research into relative degrees of relationships. This replacement resolved the conflict, much discussed at the time, between the continuity of ancestor–descendant lineages and the discontinuity inherent in the natural (phylogenetic) system. Walter Zimmermann refined Abel’s methodology, which he called character‐phylogenetics (Merkmalsphylogenie), an approach that was eventually adopted by Willi Hennig.     

Adolf Naef (1883–1949), systematic morphology and phylogenetics

Several authors have highlighted methodological similarities between Naef’s systematic morphology and Hennig’s phylogenetic systematics. Whereas this may indicate an influence of Naef on Hennig, the relevant issues – such as the principle of generality in character analysis and the threefold parallelism of classification, ontogeny and the Fossil Record – reach back beyond Naef and Hennig and were widely discussed in the German systematics literature of the late 19th and early 20th Century. The same is true of conceptual issues, such as the discussion of the principle of monophyly, which was first introduced by Haeckel in 1866 ( Rieppel 2011b , J Zool Syst Evol Res 49 :1). In spite of methodological and conceptual agreements, Naef’s systematic morphology differed fundamentally from Hennig’s phylogenetic systematics. Naef emphasized the role of unbiased observation and the immediate acquaintance of the investigator with the phenomena given in nature as the basis of natural science in general, and of his hierarchy of types in particular. From the hierarchy of types, Naef derived through conceptual‐logical analysis the natural system, which above the species level forms a nested hierarchy of intensionally defined classes, denoted by general names. The historical‐causal interpretation of the hierarchy of types in turn offers insight into the hypothetical reality of phylogeny. Hennig in contrast denied the possibility of theory‐free observation, indeed of assumption‐free science in general, and on that basis put metaphysical issues above epistemology. Tying individuality to spatiotemporal location, historicity and causality, Hennig took not only species (as did Naef) but also supraspecific monophyletic taxa as individuals, denoted by proper names. From the species up, the phylogenetic system thus becomes a nested hierarchy of complex wholes of increasing degrees of complexity. Diagnostic characters of species or higher taxa can then no longer define classes (as in Naef’s natural system) but are thought to indirectly indicate the phylogenetic relations on which alone the phylogenetic system is to be based.     

Extant primitively segmented spiders have recently diversified from an ancient lineage

Living fossils are lineages that have retained plesiomorphic traits through long time periods. It is expected that such lineages have both originated and diversified long ago. Such expectations have recently been challenged in some textbook examples of living fossils, notably in extant cycads and coelacanths. Using a phylogenetic approach, we tested the patterns of the origin and diversification of liphistiid spiders, a clade of spiders considered to be living fossils due to their retention of arachnid plesiomorphies and their exclusive grouping in Mesothelae, an ancient clade sister to all modern spiders. Facilitated by original sampling throughout their Asian range, we here provide the phylogenetic framework necessary for reconstructing liphistiid biogeographic history. All phylogenetic analyses support the monophyly of Liphistiidae and of eight genera. As the fossil evidence supports a Carboniferous Euramerican origin of Mesothelae, our dating analyses postulate a long eastward over-land dispersal towards the Asian origin of Liphistiidae during the Palaeogene (39–58 Ma). Contrary to expectations, diversification within extant liphistiid genera is relatively recent, in the Neogene and Late Palaeogene (4–24 Ma). While no over-water dispersal events are needed to explain their evolutionary history, the history of liphistiid spiders has the potential to play prominently in vicariant biogeographic studies.     

Functional morphology of Palaeozoic ostracods: phylogenetic implications

Recent discussions of ostracod systematics have focused on soft anatomy, both as seen in extant groups and as recorded by rare examples of special fossil preservation. The position of the fossil Palaeocopina and Leperditicopida, for which no substantial soft part evidence has yet been found, remains in the view of post-Palaeozoic workers uncertain, with some doubt as to whether they should be retained within the Ostracoda. The evolution of carapace bauplans (e.g. the development of brood pouches and lobal structures in palaeocopids as well as the development of adductor muscle scar patterns, calcified inner lamellae and carapace incisures in podocopines) is discussed in relation to presumed soft anatomy. It seems possible to distinguish between plesiomorphic (ancestral, simple) and apomorphic (derived, advanced) characters and consider their significance in ostracod systematics. Although the presumed ‘protostracod’ is not known, the combination of soft anatomy, carapace architecture and behaviour (feeding techniques, brood care) provide evidence of a general body plan which appeared (at the latest) during the Ordovician and continuously evolved towards the anatomy of modern ostracods. In parallel lineages, plesiomorphic forms have died out (leperditicopids and most palaeocopines as well as metacopines), while apomorphic lineages (‘drepanellid archetype’ of palaeocopines; resistant platycopines, podocopines and myodocopines) have survived all extinction events. The evidence supports the retention of the Palaeocopina (and probably the Leperditicopida) in the Ostracoda.     

A Cretaceous dance fly (Diptera: Empididae) from Botswana

Abstract The first fossil dance fly, Empis (s.s.) orapaensis sp.nov., of the subfamily Empidinae (Diptera: Empididae) is described from Africa. It was extracted from middle Cretaceous sediments of Orapa, Botswana.
Empis orapaensis manifests a more plesiomorphous wing venational pattern then the extant species of Empis , and a list of the apomorphic and plesiomorphic characteristics is given. The specimen modifies earlier ideas on the phylogeny of the Empidoidea.
The fossil also provides us with more conclusive evidence on the environment of Cretaceous southern Africa. E.orapanenis probably had a similar life-style to extant members of the group and therefore visited flowers.     

Class Seticoronaria and Phylogeny of the Phylum Priapulida

The Recent class Seticoronaria (Priapulida) as represented by the genus Maccabeus is compared with the newly described Priapulida from the Middle Cambrian Burgess Shale. It is concluded that the Seticoronaria retained such plesiomorphic characters of the Cambrian Priapulida as sedentary life and food trapping tentacles, whereas the other Recent class, the Priapulomorpha, is the derived, apomorphic branch of this small phylum. The bearing of this hypothesis on an eventual phylogenetic sequence of the Metazoa is discussed.     

Live history evolution in Serpulimorph polychaetes: a phylogenetic analysis

The widely accepted hypothesis of plesiomorphy of planktotrophic, and apomorphy of lecithotrophic, larval development in marine invertebrates has been recently challenged as a result of phylogenetic analyses of various taxa. Here the evolution of planktotrophy and lecithotrophy in Serpulimorph polychaetes (families Serpulidae and Spirorbidae) was studied using a hypothesis of phylogenetic relationships in this group. A phylogenetic (parsimony) analysis of 36 characters (34 morphological, 2 developmental) was performed for 12 selected serpulid and 6 spirorbid species with known reproductive/developmental strategies. Four species of Sabellidae were used in the outgroup. The analysis yielded 4 equally parsimonious trees of 78 steps, with a consistency index (CI) of 0.654 (CI excluding uninformative characters is 0.625). Under the assumption of unweighted parsimony analysis, planktotrophic larvae are apomorphic and non-feeding brooded embryos are plesiomorphic in serpulimorph polychaetes. The estimated polarity of life history transitions may be strengthened by further studies demonstrating an absence of a unidirectional bias in planktotrophy-lecithotrophy transition in polychaetes.     

When phylogenetics met biogeography: Willi Hennig,Lars Brundin and the roots of phylogenetic and cladistic biogeography

Willi Hennig's (Beitr. Ent. 1960, 10, 15) Die Dipteren-Fauna von Neuseeland als systematisches und tiergeographisches Problem applied a phylogenetic approach to examine the distributional patterns exhibited by the Diptera of New Zealand. Hennig showed how phylogenetic trees may be used to infer dispersal, based on the progression and deviation rules, and also discussed the existence of vicariance patterns. The most important author who applied Hennig's phylogenetic biogeography was Lars Brundin, when analysing the phylogenetic relationships of two taxa of Chironomidae (Diptera) and using them to examine the biogeographic relationships of Australia, New Zealand, South America and South Africa. The relevance of Brundin's contribution was noted by several authors, as it began the cladistic or vicariance approach to biogeography, that implies the discovery of vicariance events shared by different monophyletic groups. Both phylogenetic and cladistic biogeography have a place in contemporary biogeography, the former for analysing taxon biogeography and the latter when addressing Earth or biota biogeography. The recent use of the term “phylogenetic biogeography” to refer to a posteriori methods of cladistic biogeography is erroneous and should be avoided.     

Key novelties in the evolution of the aquatic colonial phylum Bryozoa: evidence from soft body morphology

Molecular techniques are currently the leading tools for reconstructing phylogenetic relationships, but our understanding of ancestral, plesiomorphic and apomorphic characters requires the study of the morphology of extant forms for testing these phylogenies and for reconstructing character evolution. This review highlights the potential of soft body morphology for inferring the evolution and phylogeny of the lophotrochozoan phylum Bryozoa. This colonial taxon comprises aquatic coelomate filter‐feeders that dominate many benthic communities, both marine and freshwater. Despite having a similar bauplan, bryozoans are morphologically highly diverse and are represented by three major taxa: Phylactolaemata, Stenolaemata and Gymnolaemata. Recent molecular studies resulted in a comprehensive phylogenetic tree with the Phylactolaemata sister to the remaining two taxa, and Stenolaemata (Cyclostomata) sister to Gymnolaemata. We plotted data of soft tissue morphology onto this phylogeny in order to gain further insights into the origin of morphological novelties and character evolution in the phylum. All three larger clades have morphological apomorphies assignable to the latest molecular phylogeny. Stenolaemata (Cyclostomata) and Gymnolaemata were united as monophyletic Myolaemata because of the apomorphic myoepithelial and triradiate pharynx. One of the main evolutionary changes in bryozoans is a change from a body wall with two well‐developed muscular layers and numerous retractor muscles in Phylactolaemata to a body wall with few specialized muscles and few retractors in the remaining bryozoans. Such a shift probably pre‐dated a body wall calcification that evolved independently at least twice in Bryozoa and resulted in the evolution of various hydrostatic mechanisms for polypide protrusion. In Cyclostomata, body wall calcification was accompanied by a unique detachment of the peritoneum from the epidermis to form the hydrostatic membraneous sac. The digestive tract of the Myolaemata differs from the phylactolaemate condition by a distinct ciliated pylorus not present in phylactolaemates. All bryozoans have a mesodermal funiculus, which is duplicated in Gymnolaemata. A colonial system of integration (CSI) of additional, sometimes branching, funicular cords connecting neighbouring zooids via pores with pore‐cell complexes evolved at least twice in Gymnolaemata. The nervous system in all bryozoans is subepithelial and concentrated at the lophophoral base and the tentacles. Tentacular nerves emerge intertentacularly in Phylactolaemata whereas they partially emanate directly from the cerebral ganglion or the circum‐oral nerve ring in myolaemates. Overall, morphological evidence shows that ancestral forms were small, colonial coelomates with a muscular body wall and a U‐shaped gut with ciliary tentacle crown, and were capable of asexual budding. Coloniality resulted in many novelties including the origin of zooidal polymorphism, an apomorphic landmark trait of the Myolaemata.     

PERSPECTIVE: EVOLUTIONARY PATTERNS IN THE FOSSIL RECORD

The study of large-scale evolutionary patterns in the fossil record has benefited from a diversity of approaches, including analysis of taxonomic data, ecology, geography, and morphology. Although genealogy is an important component of macroevolution, recent visions of phylogenetic analysis as replacing rather than supplementing other approaches are short-sighted. The ability of traditional Linnaean taxa to document evolutionary patterns is mainly an empirical rather than a theoretical issue, yet the use of these taxa has been dismissed without thorough evaluation of their empirical properties. Phylogenetic analysis can help compensate for some of the fossil record's imperfections. However, the shortcomings of the phylogenetic approach have not been adequately acknowledged, and we still lack a rigorous comparison between the phylogenetic approach and probabilistic approaches based on sampling theory. Important inferences about the history of life based on nongenealogical data have later been corroborated with genealogical and other analyses, suggesting that we risk an enormous loss of knowledge and understanding if we categorically dismiss nonphylogenetic data.     

Evolutionary theory and systematics: relationships between process and patterns

The relevance of the Modern Evolutionary Synthesis to the foundations of taxonomy (the construction of groups, both taxa and phyla) is reexamined. The nondimensional biological species concept, and not the multidimensional, taxonomic, species notion which is based on it, represents a culmination of an evolutionary understanding. It demonstrates how established evolutionary mechanisms acting on populations of sexually reproducing organisms provide the testable ontological basis of the species category. We question the ontology and epistemology of the phylogenetic or evolutionary species concept, and find it to be a fundamentally untenable one. We argue that at best, the phylogenetic species is a taxonomic species notion which is not a theoretical concept, and therefore should not serve as foundation for taxonomic theory in general, phylogenetics, and macroevolutionary reconstruction in particular. Although both evolutionary systematists and cladists are phylogeneticists, the reconstruction of the history of life is fundamentally different in these two approaches. We maintain that all method, including taxonomic ones, must fall out of well corroborated theory. In the case of taxonomic methodology the theoretical base must be evolutionary. The axiomatic assumptions that all phena, living and fossil, must be holophyletic taxa (species, and above), resulting from splitting events, and subsequently that evaluation of evolutionary change must be based on a taxic perspective codified by the Hennig ian taxonomic species notion, are not testable premises. We discuss the relationship between some biologically, and therefore taxonomically, significant patterns in nature, and the process dependence of these patterns. Process-free establishment of deductively tested “genealogies” is a contradiction in terms; it is impossible to “recover” phylogenetic patterns without the investment of causal and processual explanations of characters to establish well tested taxonomic properties of these (such as homologies, apomorphies, synapomorphies, or transformation series). Phylogenies of either characters or of taxa are historical-narrative explanations (H-N Es), based on both inductively formulated hypotheses and tested against objective, empirical evidence. We further discuss why construction of a “genealogy”, the alleged framework for “evolutionary reconstruction”, based on a taxic, cladistic outgroup comparison and a posteriori weighting of characters is circular. We define how the procedure called null-group comparison leads to the noncircular testing of the taxonomic properties of characters against which the group phylogenies must be tested. This is the only valid rooting procedure for either character or taxon evolution. While the Hennig -principle is obviously a sound deduction from the theory of descent, cladistic reconstruction of evolutionary history itself lacks a valid methodology for testing transformation hypotheses of both characters and species. We discuss why the paleontological method is part of comparative biology with a critical time dimension ana why we believe that an “ontogenetic method” is not valid. In our view, a merger of exclusive (causal and interactive, but best described as levels of organization) and inclusive (classificatory) hierarchies has not been accomplished by a taxic scheme of evolution advocated by some. Transformational change by its very nature is not classifiable in an inclusive hierarchy, and therefore no classification can fully reflect the causal and interactive chains of events constituting phylogeny, without ignoring and contradicting large areas of corroborated evolutionary theory. Attempts to equate progressive evolutionary change with taxic schemes by Haeckel were fundamentally flawed. His ideas found 19th century expression in a taxic perception of the evolutionary process (“phylogenesis”), a merger of typology, hierarchic and taxic notions of progress, all rooted in an ontogenetic view of phylogeny. The modern schemes of genealogical hierarchies, based on punctuation and a notion of “species” individuality, have yet to demonstrate that they hold promise beyond the Haeckel ian view of progressive evolution.     

High-resolution X-ray computed tomography of an Early Cretaceous gekkonomorph (Squamata) from Öösh (Övörkhangai; Mongolia)

We describe the braincase of AMNH FR 21444, a gecko-like squamate from the Early Cretaceous of Mongolia, based on high-resolution X-ray computed tomography scans (CT scans) and incorporate it in a phylogenetic analysis of 36 squamate taxa scored for 226 morphological characters. Our analysis corroborates the Eublepharidae-Gekkonoidea split as the basal gekkotan dichotomy, but retrieves Teratoscincus as the sister-taxon to pygopodines + diplodactylines. The combination of plesiomorphic and apomorphic character states within AMNH FR 21444 demonstrates a decoupled evolutionary history between the braincase and the rest of the skull and mandible within gekkonomorph squamates. Enclosure of the lateral head vein and mandibular branch of the trigeminal nerve are both plesiomorphic for gekkonomorphs. The mechanisms responsible for the transition from the plesiomorphic skull roof of basal gekkonomorphs to the modern gekkotan condition cannot be anticipated given the current data.     

The phylogenetic position of the Clitellata and the Echiura - on the problematic assessment of absent characters*

Absent characters (negative characters) are difficult to assess and their correct interpretation as symplesiomorphies, synapomorphies or convergencies (homoplasies) is one of the greatest challenges in phylogenetic systematics. Different phylogenetic assessments often result in contradictory phylogenetic hypotheses, in which the direction of evolutionary changes is diametrically opposed. Especially in deciding between primary (plesiomorphic) and secondary (apomorphic) absence, false conclusions may be reached if only the outgroup comparison and the principle of parsimony are employed without attempting any biological evaluation or interpretation of characters. For example, in the higher‐level systematization of the Annelida and related taxa different assessments of absent characters have led to conflicting hypotheses about the phylogenetic relationships and the ground pattern of the annelid stem species. Varying phylogenetic interpretations regarding the absence of the chemosensory nuchal organs in the clitellates and their presence in polychaetes initiated a controversy that produced two alternative phylogenetic hypotheses: (1) the Clitellata are highly derived Annelida related to a subtaxon within the, in this case, paraphyletic ‘Polychaeta’ or (2) the Clitellata are comparatively primitive Annelida representing the sister group of a monophyletic taxon Polychaeta. In the former, the absence of nuchal organs in the Clitellata is regarded as a secondary character, in the latter as primary. As most Clitellata are either limnetic or terrestrial, we must ask which characters are plesiomorphies, taken from their marine stem species without changes. In addition to a thorough investigation and evaluation of clitellate characters, a promising approach to these questions is to look for such characters in limnetic and terrestrial annelids clearly not belonging to the Clitellata. A similar problem applies to the evaluation of the position of the Echiura, which lack both segmentation and nuchal organs. Evidence is presented that in both taxa these absent characters represent derived, apomorphic character states. The consequences for their phylogenetic position and the questionable monophyly of the Polychaeta are discussed. The conclusion drawn from morphological character assessments is in accordance with recently published hypotheses based on molecular data.     

CLADISTIC TESTS OF ADAPTATIONAL HYPOTHESES

Abstract— A cladistic viewpoint provides an historical definition of adaptation and an operational ecological test for evolutionary adaptations. Adaptation is apomorphic function promoted by natural selection, as compared with plesiomorphic function. Adaptation is thus a conditional, hierarchical, comparative term, like homology. Hypotheses of adaptation that do not specify levels of apomorphy are weak; they should refer to and explain the function at the level at which it is apomorphic with respect to the plesiomorphic (outgroup) condition. The adaptational hypothesis serves as a prior prediction in the comparison of the apomorphic function of the derived trait with the plesiomorphic function of the plesiomorphic trait serving as the null hypothesis. It is useful to distinguish whether hypotheses about characters identify selection as facilitating: 1) the origin of a character; 2) its maintenance; 3) neither; or 4) both. The latter two are uniformitarian and testable in a strong sense. The former two possibilities use ancillary arguments to protect the hypothesis of the role of natural selection in one way or another, but might still be tested by the weak criterion of plausibility. Given an hypothesis of both origin and maintenance due to selection, the test of adaptation may still be thwarted because only certain kinds of cladistic structure allow feasible tests. Few of the really classic and common examples of supraspecific adaptation survive this kind of cladistic test.