Ontogenetic Sequence Research Articles

Gomphodont cynodonts of the Chañares Formation: the analysis of an ontogenetic sequence

ABSTRACT A revision of gomphodont cynodonts from the Chañares Formation of Argentina, is presented. Four species in two genera: Massetognathus pascuali, M. teruggii, M. major, and Megagomphodon oligodens were originally described by Romer in 1967 and 1972. Qualitative characters proposed originally as diagnostic of the species were revised, and a bivariate analysis of allometry of 17 linear skull measurements was performed upon 31 specimens. Allometry relationships account for most of the differences among specimens. There are neither size gaps nor systematic trends across the sample. The temporal region scales with a ‘positive’ allometry, whereas components of the neuro-cranium and muzzle show ‘negative’ or isometric scaling. This results in a change from short, stocky skulls with large muzzles in small specimens, to slender skulls with small muzzles and large temporal fossae characteristic of large individuals. The reduction and ontogenetic loss of the parietal foramen in a cynodont is reported for the first time. Consideration of qualitative characters together with the allometric results lead us to conclude that all forms belong to a single species in a growth series. Consequently, Massetognathus pascuali is recognized as the only valid entity, an idea previously suggested but without a justification based upon extensive analysis.

Pollen and anther development inNelumbo(Nelumbonaceae)

The Nelumbonaceae are a small family of aquatic angiosperms comprising Nelumbo nucifera and Nelumbo lutea. Historically, the genus has been considered to be closely related to Nymphaeales, however new systematic work has allied Nelumbo with lower eudicots, particularly Platanus. In recent years, studies of pollen development have contributed greatly to the understanding of phylogenetic relationships, but little has been known about these events in Nelumbo. In this paper, pollen and anther development are morphologically described for the first time in N. lutea. A comprehensive ontogenetic sequence is documented, including the sporogenous tissue, microspore mother cell, tetrad, free spore, and mature pollen grain stages. The deposition of a microspore mother cell coat and callose wall, the co-occurrence of both tetrahedral and tetragonal tetrads, the formation of a primexine in tetrads, and primexine persistence into the late free spore stage are shown. The majority of exine development occurs during the free spore stage with the deposition of a tectate-columellate ectexine, a lamellate endexine, and an unusual granular layer below and intermixed with the endexine lamellae. A two-layered intine forms rapidly during the earliest mature pollen stage. Major events of anther development documented include the degradation of a secretory-type tapetum during the free spore stage and the rapid formation of U-shaped endothecial thickenings in the mature pollen grain stage. The majority of mature pollen grains are tricolpate, however less common monosulcate and diaperturate grains also develop. Co-occurring aperture types in Nelumbo have been suggested to be an important transition in angiosperm aperture number. However, aperture variability in Nelumbo may be correlated with the lateness of aperture ontogeny in the genus, which occurs in the early free spore stage. This character, as well as other details of pollen and anther ontogeny in Nelumbo, are compared to those of Nymphaeales and Platanus in an effort to provide additional insight into systematic and phylogenetic relationships. Although Nelumbo is similar to both groups in several characters, the ontogenetic sequence of the genus is different in many ways.

Male Ontogeny and Size-Related Variation in Mass Allocation of Bluenose Shiners (Pteronotropis welaka)

During the spawning season of Pteronotropis welaka (bluenose shiners), three types of males were present in the population that differed in size, coloration, morphology, and mass allotment. The smallest males (initial males) were less dimorphic in both coloration and morphology, whereas the largest males (terminal males) represented the peak in sexually dimorphic development. Intermediate-sized males (transitional males) were also intermediate in size and coloration. The three types of males represent phases of a continual ontogenetic sequence in which initial males were in the first phase of ontogeny of sexually mature males followed by transitional males that were in transition to the terminal phase, the climax of development. Transition into a terminal male involved the expansion of median fins and pelvic fins, formation of blue on the head, increase in iridescent patches on scales, loss of yellow pigment in the dorsal fin, and general intensification of black pigment. Variation in mass allocation among somatic, reproductive, and storage components occurred among phases of P. welaka males. Initial and terminal males allocated a similar relative amount of mass to testicular tissue. Transitional males, however, during the period of increased development of secondary sexual characters and growth allocated a lower proportion of their mass to reproduction. Simultaneously, transitional males allocated the same relative mass to storage (fat deposits). Either transitional males allocated less mass to a functional testes, or delayed gonad maturation. Similar testes gross morphology observed among the types of males may indicate the former. This may represent a trade-off of current reproductive tissue development for somatic growth and development of secondary sexual characters, while not utilizing fat reserves that may be needed for future activities.

A modern interpretation of the Rood Approach

The Rood Approach for the treatment of central nervous system disorders was developed by Margaret Rood in the 1950s. Rood's technique can be categorized as one of facilitation and inhibition of movement. It is one of several of the neurophysiological Approaches which developed at that time and is centered upon four basic concepts to consider during treatment: duality, the ontogenetic sequence, manipulation of the autonomic nervous system and the level of excitability of the anterior horn cell.As with the other neurophysiological Approaches (notably Bobath, PNF and Brunnstrom), Rood's rationale for treatment has been criticized for the naiveté of its physiological rationale. Although this criticism is justified, it does not mean that the techniques are without value. This paper includes a brief explanation of Rood's rationale for treatment and a review of the literature which highlights the benefits and limitations of many aspects of this approach. It can be seen that several of the basic concepts are valid and viable within current neuroscientific thinking. The conclusion is that the Rood Approach is a modular model, and as such is capable of adapting to advancing knowledge.

Oxygen and carbon isotopic "dissection" of Baculites compressus (Mollusca: Cephalopoda) from the Pierre Shale (Upper Campanian) of South Dakota: Implications for paleoenvironmental reconstructions

A systematic stable isotopic study of an exceptionally well-preserved Baculites compressus specimen from the Pierre Shale (Upper Campanian) of South Dakota was conducted to assess whether the variations recorded in the calcareous shells of baculitids can be used as a reliable indicator of paleoenvironmental conditions. We sampled the B. compressus conch along four sampling profiles: (1) an ontogenetic traverse parallel to growth direction, (2) a virtually isochronous traverse along two different lirae delineated by growth lines, (3) a septal traverse, and (4) a shell-wall traverse through the conch wall. To date, the ontogenetic sequence is the longest record produced from baculitids. We interpret the isotopic variations determined from the ontogenetic, septal, and depth-profile traverses to be dominated by an environmental signal, especially in shell material deposited prior to septal crowding (i.e., maturity). In contrast, we interpret the isotopic variations determined from the isochronous traverse along the two different lirae to be altered by biological vital effects. Our results indicate that a careful sampling strategy that avoids strongly ornamented areas of the shell is required if a true paleoenvironmental signal is to be extracted from the calcareous shells of baculitids, and perhaps other ammonites as well. Our best estimate of seasonal seawater-temperature variation in the Late Campanian Western Interior Seaway at 42 degrees N, based on the oxygen isotopic data from the baculitid specimen, is 10.0 degrees C (range of 29.7 degrees C to 19.7 degrees C).

NADPH-d positive neurons in the developing somatosensory cortex of the rat: effects of early and late environmental enrichment

The effects of environmental enrichment upon the topographic arrangement of NADPH diaphorase-positive neurons (NADPH-d + neurons) was studied in the somatosensory cortex of 56 Sprague–Dawley albino rats during early stages of development (18th, 24th, 30th and 60th postnatal days). This diaphorase is easily demonstrable, providing a convenient marker for quantitative studies. Environmental enrichment diminished the number of NADPH-d + neurons and exerted its maximal influence during lactation, a time of exceptional cortical susceptibility. This implies that the magnitude of such effects on the density of NADPH-d + neurons is age-dependent. Furthermore, it was found that the experience-dependent cortical changes persisted after a subsequent period without environmental stimulation. The effects of early environmental enrichment did not occur uniformly throughout the cerebral hemispheres but, instead, such effects were maximal in the latero-ventral sector of the cerebral cortex where a dramatic reduction in the number of NADPH-d + neurons was observed. Particularly striking was the existence of a latero-medial sequence of NADPH-d + neurons in the infragranular layer and a reversed distribution of labeled cells, in the supragranular layer. Both ontogenetic sequences of NADPH-d + neurons remained unchanged during postnatal development in controls and enriched subjects (18th–60th postnatal days).

Play, Dreams, and Creativity

Viewed ontogenetically, creating, dreaming, and playing are a variant of object relatedness. It is suggested that in recapitulating the ontogenetic sequence, creating, dreaming, and playing each as a process initiates by de-differentiation to primal union, evolves into transitional functioning, and consummates in tertiary cognitive discourse. The products of the triad—the created object, the dream, and play—are viewed as synergistic psychodynamic composites of topical, personal, and archetypical imperatives. Creating, dreaming, and playing are easily overburdened by events, becoming stereotypical and repetitious. Nowhere is this more clearly seen than in the play of chronically ill, hospitalized children. It is suggested that with development generally, playing is replaced by formalized games; only dreaming continues as the vestige of early creative abilities.

Ontogenetic changes in retinal structure and visual acuity: a comparative study of coral-reef teleosts with differing post-settlement lifestyles

Changes in retinal structure during settlement were investigated in four species of tropical reef-associated teleost fishes with differing periods of planktonic duration and post-settlement lifestyles. They were: Apogon doederleini (Apogonidae), a nocturnal planktivore; Stethojulis strigiventer (Labridae), a diurnal microcarnivore; Upeneus tragula (Mullidae), a carnivore which uses chin barbels to disturb invertebrates from the sediment; and Pomacentrus moluccensis (Pomacentridae), a diurnal herbivorous planktivore. The densities of cones, rods, cells in the inner nuclear layer and cells in the ganglion cell layer were estimated in a size range of each species. Visual acuity was calculated using cone densities and lens diameter. The ontogenetic sequence of changes in cell density was similar in all species but interspecific variation in the timing and rates of change was found and could be related to lifestyle. For example, cone densities decreased and rod densities increased most rapidly in the nocturnal species, A. doederleini, during settlement. In contrast, high cone densities were maintained in the species adopting a diurnal lifestyle. Theoretical visual acuity was found to increase rapidly as lens size increased, but was similar for all species at similar lens sizes, indicating the importance of larger eye size as a means for improving resolution during early stages of eye growth. It was concluded that for the species undergoing abrupt lifestyle changes at settlement, structural re-organisation of the retina is important for the survival of the fish as they leave the pelagic environment and take up their reef-associated lifestyle.

Rod photoreceptor neurogenesis

Abstract This article reviews evidence about the phylogenetic and ontogenetic origins of rod photoreceptors. Studies of morphology, molecular phylogeny of the opsin molecules, and retinal wiring indicate cone photoreceptors are the more ancient of the two kinds of photosensitive cells in the retina. Consistent with this view, rod photoreceptors arise later in ontogenesis in all vertebrates. The most dramatic example of this ontogenetic sequence is retinal development in cold-blooded vertebrates, particularly teleost fish, in which rods continue to be added throughout life. Because of this extension of ontogenesis into adulthood, examination of the teleost eye offers a unique model system for studying retinal development. Control of retinal rod neurogenesis requires exquisite coordination of both genetic and extrinsic factors for appropriate temporal and spatial expression.

Architectural models for apical patterns in Gelidium (Gelidiales, Rhodophyta): hypothesis of growth

SUMMARYThe great morphological variation in the apical region of main axes and branches in species of Gelidium and Pterocladia suggests different patterns of growth. Those patterns have been reconstructed from the ontogenetic sequence of morphological stages and regeneration of the apex. Using the architectural approach, models for four species of Gelidium from the Pacific coast of central Chile and the Pacific coast of Mexico's tropical region, were constructed based on the following criteria: growth pattern, specialization of laterals, symmetry, apical dominance and rhythm of apical and lateral growth. Those models allow for a formal evaluation of apical differences between species.

Morphogenetic processes in division of Uronema filificum Kahl 1931 (Ciliophora: Scuticociliatida) and implications for its systematic position in the family uronematidae

Summary Stomatogenesis in Uronema filificum was studied with pyridinated silver carbonate. Fourteen morphogenetic stages are described. The ontogenetic sequence develops for the proter: haplokinety → haplokinety and scutica; for the opisthe: haplokinety → haplokinety, Ml, M2 and scutica, and scutica → M3. This stomatogenetic pattern is similar to that described for other genera in the same family, but the anlage morphogenetic sequence differs slightly from previous descriptions. The systematic position of Uronema filificum is discussed in the light of the new morphogenetic data reported.

Four-year-old humans are different: Why?

AbstractThe intentionality schema is an abstraction that relates phylogenetic and ontogenetic sequences of social understanding, but it also obscures the differences between humans and other primates. In particular, it ignores human social developmental and communicative history and the important roles that language plays in human understanding of others' intentional states.

Graptolite ontogeny and the size of the graptolite zooid

AbstractTwo methods of estimating the size of the graptolite zooid are described and discussed. It is possible to size a zooid by reference to cortical bandages or with reference to modem Rhabdopleura and its tubes. These two methods give very different results, with the first suggesting small zooids relative to thecal size and the second suggesting zooids that filled their thecae completely. Comparison is made with the evidence available from rare cases of preserved zooids. When all these observations are considered in the light of the ontogeny of modem pterobranchs, an ontogenetic sequence for the graptolite zooid can be inferred which helps to reconcile the two methods of estimating zooid size. This sequence postulates that most skeletal building occurred early in the life of the zooid, before it developed the capacity to feed or to reproduce, and it implies that only the first of three stages in the zooid's life is recorded in the skeleton. The later stages occurred without normally leaving any trace on the preservable remains of the colony. Finally, there is discussion of the effects which different zooid sizes would have had on some aspects of the functional morphology of a theca and on the hydrodynamic behaviour of the rhabdosome as a whole.

The sequential hypothesis of the function of sleep

In addition to modulatory roles concerning bodily functions, sleep is assumed to play a main processing role with regard to newly acquired neural information. Elaboration of memory traces acquired during the waking period is assumed to require two sequential steps taking place during slow wave sleep (SWS) and eventually during paradoxical sleep (PS). This view is suggested by several considerations, not the least of which concerns the natural sequence of appearance of SWS and PS in the adult animal. While the involvement of PS in memory processing is well documented, the involvement of SWS is supported by the results of baseline and post-trial EEG analyses carried out in rats trained for a two-way active avoidance task or a spatial habituation task. Together with control analyses, these data indicate that the marked increase in the average duration of post-trial SWS episodes does not reflect the outcome of non-specific contingent factors, such as sleep loss or stress, but is related to memory processing events. Several considerations have furthermore led to the proposal that, during SWS, after a preliminary selection step, the first processing operation consists in the weakening of non-adaptive memory traces. The remaining memory traces would then be stored again under a better configuration during the ensuing PS episode. This view is in agreement with several relevant features of sleep, including the EEG waveforms prevailing during SWS and PS, as well as the ontogenetic sequence of appearance of SWS and PS. Some theoretical considerations on the role of sleep are also in agreement with the sequential hypothesis. More recent data indicate that the learning capacity of rats is correlated with several baseline EEG features of sleep and wakefulness. They include the average duration of PS episodes and of SWS episodes followed by wakefulness (longer in fast learning rats), and the waking EEG power spectrum of fast learning rats whose output is more balanced in the frequency range below 10 Hz than in show learning and in non-learning rats. Additional EEG data suggest that fast learning rats may accomplish ‘on line’ processing of newly acquired information according to a sequence of events not dissimilar from the one proposed by the sequential hypothesis.

Life Cycle Evolution in Asteroids: What is a Larva?

The diversity of larval forms and developmental patterns in asteroid echinoderms has become increasingly apparent over the past 10-15 years. However, the classification of developmental patterns has been ambiguous because the patterns have not been defined as unique sets of ecological and developmental character states. In addition, character states have not been defined consistently. Thus attempts to understand the evolutionary changes in development (e.g., heterochrony and heterotopy in morphogenesis) that underlie larval diversity have been hampered. We propose a multifactor classification of asteroid developmental patterns that uses an explicit set of characters that provide information on habitat (e.g., pelagic or benthic) and mode of nutrition (e.g., feeding or nonfeeding) of the developing young, as well as the type of morphological development (indirect = larval; direct = nonlarval). We conclude that direct development is exceptionally rare. All asteroids whose development has been studied, except Pteraster tesselatus, have the indirect type of development. We also propose definitions of some important terms that have been used inconsistently in the literature (e.g., larva, metamorphosis, indirect development, and direct development). Our definitions take into account the continuous nature of development and the evolutionary diversification of ontogenetic sequences. These definitions are intended to provide a clear conceptual basis for analyzing asteroid life cycle evolution. We argue that the ancestral asteroid life cycle involved pelagic larval development with both bipinnarian and brachiolarian stages. We then present a series of hypotheses for six types of evolutionary transitions in development that can account for the diversity of larval forms and developmental patterns in starfish.

Coding Polymorphic Data: Examples from Allozymes and Ontogeny

Limitations for using polymorphic characters in phylogenetic analysis include the lack of computer algorithms that allow input of complex branched or reticulate character state trees and the inability to use polymorphisms as data in tree building and character optimization. The step matrix option in PAUP version 3.0 and MacClade versions 2.1 and 3.0 provides a solution to these problems, allowing all homology information among character states to be utilized while retaining a biologically realistic definition of characters. For genetic data, this means that the locus can be coded as the character and allelic combinations can be coded as the character states. For ontogenetic data, this means that the entire ontogenetic sequence can be coded as the character and combinations of observed conditions within ontogenies can be coded as the character states. The unity of the locus or character ontogeny is preserved, and homology information from shared electrophoretic or ontogenetic conditions is not lost. Attention has not been called to the loss of homology information that accompanies coding the locus or an entire ontogeny as the character, possibly because of the lack of a coding option through which these data could be retained. The step matrix option allows any and all assumptions of transformation (order) among character states while retaining the unity of the locus or a whole ontogeny as the character and can be utilized for coding these and other polymorphic characters for phy? logenetic analysis. (Polymorphic; allozyme; ontogeny; character; order; coding; homology; step matrix.)

Ontogenetic Scaling of Jump Performance in the African Desert Locust (Schistocerca Gregaria)

ABSTRACT Ontogenetic growth was used as a model for the effect of body size on jumping performance of the African desert locust (Schistocerca gregaria). Using models that generated relationships between morphology and body size proposed by McMahon and the relationships between morphology and performance described by Hill, we generated testable predictions of how jumping performance measures may change as a function of body mass. Data were collected over an ontogenetic sequence that ranged from 1-day-old first instars to 45-day-old adults. Performance was quantified using a high-sensitivity, three-dimensional force plate. Performance parameters quantified included the force, acceleration, take-off velocity, kinetic energy and power output. With the exception of power output, each measure of performance scaled to body mass in a manner consistent with the predictions of the elastic similarity model. Power output scaled to body mass in a manner consistent with the predictions of the constant stress similarity model. As we noted previously for the scaling of flexural stiffness of the metathoracic tibiae, the elastic similarity model is approximated by the performance of the locust in spite of the morphological design that deviates from that model’s predictions. These results indicate that the jump has separate functions in the flightless juvenile instars and in the flying adult stage of the life history. Juvenile locusts produce take-off velocities of between 0.9 and 1.2 ms−1 that are relatively scale-independent. The take-off velocity in juveniles produces a distance of ballistic travel that averages between 20 and 30cm. In adults, the take-off velocity is also relatively scale-independent at a level approximately twice as high as in juveniles (i.e. 2.5 ms−1). This velocity is coincident with the minimum flight speed reported by Weis-Fogh and a minimum flight speed that we have estimated using actuator disc theory. We suggest that, in juveniles, the jump is designed to achieve a characteristic distance travelled and in adults the jump is designed to achieve a minimum velocity necessary to fly.

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 × 10 36 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.

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

Abstract 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 × 10 36 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.

Application of the biogenetic law to behavioral ontogeny: a test using nest architecture in paper wasps

AbstractGeneral principles derived from studies of morphological ontogeny are useful in ethology. Behavioral ontogeny may be interpreted from an holistic view in which a series of behaviors is treated as an ontogeny toward a larger, complex, behavioral product. If the component behaviors are defined broadly, many taxa may be compared to find general principles that are not evident when behaviors are dissected to their smallest recognizable units. Flow charts can illustrate such general ontogenetic sequences in a manner that shows what sorts of modifications have evolved from the general pattern. Certain changes may illustrate forms of ontogenetic evolution that are well known for morphological development, such as addition or embellishment of terminal ontogenetic steps, or compression of ontogeny by acceleration or deletion of early steps. The major modifications in nest construction behavior of 28 genera of paper wasps are presented to test the predictions of the biogenetic rule with respect to character polarity. Cladistic analyses of separate morphological and behavioral data sets show that polarity is accurately inferred with respect to the five major patterns of nest construction in paper wasps.