Miriam Leah Zelditch

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Verified

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• PhD
• Associate Research Scientist at University of Michigan

Several theories predict that rapidly diversifying clades will also rapidly diverge phenotypically; yet, there are also reasons for suspecting that diversification and divergence might not be correlated. In the widely distributed squirrel clade (Sciuridae), we test for correlations between per-lineage speciation rates, species richness, disparity a...

Convergence is widely regarded as compelling evidence for adaptation, often being portrayed as evidence that phenotypic outcomes are predictable from ecology, overriding contingencies of history. However, repeated outcomes may be very rare unless adaptive landscapes are simple, structured by strong ecological and functional constraints. One such co...

A classic hypothesis posits that lineages exhibiting long‐term stasis are broadly adapted generalists that remain well‐adapted despite environmental change. However, lacking constraints that steepen adaptive peaks and stabilize the optimum, generalists’ phenotypes might drift around a broad adaptive plateau. We propose that stasis would be likely f...

Modularity is now generally recognized as a fundamental feature of organisms, one that may have profound consequences for evolution. Modularity has recently become a major focus of research in organismal biology across multiple disciplines including genetics, developmental biology, functional morphology, population and evolutionary biology. While t...

During ontogeny, animals often undergo significant shape and size changes, coinciding with ecological shifts. This is evident in parrotfishes (Eupercaria: Labridae), which experience notable ecological shifts during development, transitioning from carnivorous diets as larvae and juveniles to herbivorous and omnivorous diets as adults, using robust...

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Modularity and integration are fundamental properties of organisms and central to theories of complex adaptation. Modularity and integration of shape can provide valuable information about the geometry and spatial structure of modules, but a recent study contends that Procrustes superimposition yields alarmingly high frequencies of statistically si...

Identifying the drivers of adaptation is key to understanding the origin and evolution of diversity. Here we study the morphological evolution of tooth morphology, a classic example of a conserved structure, to gain insights into the conditions that can overcome resistance to evolutionary change. We use geometric morphometrics of the occlusal surfa...

Allometry has been a paradigm of constraints, including intrinsic constraints on the evolvability of allometry, as a source of developmental and genetic constraints on the evolution of form, and of functional constraints, maintaining functional equivalence as body size evolves. Yet, allometry may be the simplest case of varied constraints, and of m...

The mammalian family Bovidae has been widely studied in ecomorphological research, with important applications to paleoecological and paleohabitat reconstructions. Most studies of bovid craniomandibular features in relation to diet have used linear measurements. In this study, we conduct landmark-based geometric-morphometric analyses to evaluate wh...

Spatial patterns of species richness, phylogenetic and morphological diversity are key to answering many questions in ecology and evolution. Across spatial scales, geographical and environmental features, as well as evolutionary history and phenotypic traits, are thought to play roles in shaping both local species communities and regional assemblag...

Trade‐offs are inherent features of many biomechanical systems and often are seen as evolutionary constraints. Structural decoupling may provide a way to escape those limits in some systems, but not for structures that transmit large forces, like mammalian mandibles. For such structures to evolve in multiple directions on a complex adaptive landsca...

Aim We investigate geographic patterns across taxonomic, ecological and phylogenetic diversity to test for spatial (in)congruency and identify aggregate diversity hotspots in relationship to present land use and future climate. Simulating extinctions of imperilled species, we demonstrate where losses across diversity dimensions and geography are pr...

Fishes are both extremely diverse and morphologically disparate. Part of this disparity can be observed in the numerous possible fin configurations that may differ in terms of the number of fins as well as fin shapes, sizes and relative positions on the body. Here, we thoroughly review the major patterns of disparity in fin configurations for each...

Modularity is considered a prerequisite for the evolvability of biological systems. This is because in theory, individual modules can follow quasi-independent evolutionary trajectories or evolve at different rates compared to other aspects of the organism. This may influence the potential of some modules to diverge, leading to differences in dispar...

Les poissons constituent un groupe à la fois très riche en espèces mais aussi en diversité de formes corporelles, notamment en raison de différences dans la configuration des nageoires. Afin de mieux comprendre l’origine de ces différences, il est nécessaire de clarifier le scénario évolutif traduisant l’apparition séquentielle des nageoires. Celui...

Background: Fishes are extremely speciose and also highly disparate in their fin configurations, more specifically in the number of fins present as well as their structure, shape, and size. How they achieved this remarkable disparity is difficult to explain in the absence of any comprehensive overview of the evolutionary history of fish appendages....

Integrating studies of ontogeny with analyses of disparity can reveal important and surprising insights into the origins of disparity and why it varies among groups. One such potentially surprising insight is that disparity could be constant over ontogeny even though species differ in both rates and timings of development and in their ontogenetic c...

Actinopterygians demonstrate high levels of morphological disparity, especially in the variation of fin positions, sizes and shapes. One hypothesis to explain the diversity of fin morphologies is that it is facilitated by a modular organization. According to this hypothesis, fin modules would be quasi-independent during ontogeny or evolution, facil...

Comparative studies of ontogenies of closely related species provide insights into the mechanisms responsible for morphological diversification. Using geometric morphometrics, we investigated the ontogenetic dynamics of postlarval skull shape and disparity in three closely related crested newt species. The skull shapes of juveniles just after metam...

Among fishes, actinopterygians have achieved a phenomenal ecological and evolutionary success: this group includes approximately 30 000 living species as well as an abundant fossil record. No less impressive is the extent of morphological disparity that can be observed among them, notably in terms of fin configurations, which includes position, siz...

The mouse mandible is a popular model system that continues to be the focus of studies in evo-devo and other fields. Yet, little attention has been given to the role of postnatal growth in producing the adult form. Using cleared and stained specimens, we describe the timing of tooth and jaw development and changes in jaw size and shape from postnat...

The first edition of Geometric Morphometrics for Biologists has been the primary resource for teaching modern geometric methods of shape analysis to biologists who have a stronger background in biology than in multivariate statistics and matrix algebra. These geometric methods are appealing to biologists who approach the study of shape from a varie...

Developing organisms must reconcile conflicts between demands of survival within the current life-history stage, with those of maturation, while negotiating the transitions through succeeding stages. In the case of feeding performance, the parts of the feeding apparatus and their biomechanics must maintain functional integrity to meet the feeding n...

Phenotypic integration can influence evolutionary rate and direction by channeling variation into few dimensions. The extent to which that channeling serves as a constraint over macroevolutionary timescales is determined in part by the evolutionary lability of phenotypic integration. Evolutionary change in patterns of pleiotropy, potentially reduci...

Developing animals must resolve the conflicting demands of survival and growth, ensuring that they can function as infants or juveniles while developing toward their adult form. In the case of the mammalian skull, the cranium and mandible must maintain functional integrity to meet the feeding needs of a juvenile even as the relationship between par...

Modularity of the cranidium of Crassifimbra? metalaspis, a Cambrian ptychoparioid trilobite, is investigated using landmark-based geometric morphometric methods to gain insight into the integration among morphogenetic processes responsible for shaping the head of an ancient arthropod. Of particular interest is the extent to which the structure of p...

Natural selection arising from resource competition and environmental heterogeneity can drive adaptive radiation. Ecological opportunity facilitates this process, resulting in rapid divergence of ecological traits in many celebrated radiations. In other cases, sexual selection is thought to fuel divergence in mating signals ahead of ecological dive...

In the absence of a substantial functional shift, morphological evolution is usually expected to follow an allometric trajectory, however, studies of tree squirrel jaws have found isometry across most of their size range. This isometry appears to reflect the integration of a small number of lever arm lengths that are critical for generating bite fo...

Weaning represents a challenging transition for young mammals, one particularly difficult for species coping with extreme conditions during feeding. Spotted hyenas (Crocuta crocuta) experience such extreme conditions imposed by intense feeding competition during which the ability to consume large quantities of food quickly is highly advantageous. A...

Morphological integration can respond to environmental conditions, a response that may be dynamic through ontogeny. Among fishes, brook charrs (Salvelinus fontinalis) display a trophic polymorphism that makes it a good species for analyzing the ontogeny of morphological integration. To better understand the processes regulating variation and integr...

The mammalian mandible is a developmentally modular but functionally integrated system. Whether morphological integration can evolve to match the optimal pattern of functional integration may depend on the developmental origin of integration, specifically, on the role that direct epigenetic interactions play in shaping integration. These interactio...

The contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is an environmental pollutant and teratogen that has been shown to alter craniofacial development. Differences in sensitivity to TCDD are attributed primarily to differences in alleles at the Ahr locus coding for the aryl-hydrocarbon receptor (AHR) that binds TCDD and mediates its effects b...

Summary Several models explain how a complex integrated system like the rodent mandible can arise from multiple developmental modules. The models propose various integrating mechanisms, including epigenetic effects of muscles on bones. We test five for their ability to predict correlations found in the individual (symmetric) and fluctuating asymmet...

Abstract: This chapter has two complementary aims. The first is to review the methods for morphometric data collection and the statistical techniques currently used to analyze morphological variation on the types of data obtained by physical anthropologists. The second and more important aim is to contextualize the analysis of phenotypic variation...

Skeletal anomalies are common in patients with muscular dystrophy, despite an absence of mutations to genes that specifically direct skeletogenesis. In order to understand these anomalies further, we examined two strains of muscular dystrophy (laminin- and merosin-deficient) relative to controls, to determine how the weakened muscle forces affected...

Evolutionary stasis has often been explained by stabilizing selection, intrinsic constraints, or, more recently, by spatially patterned population dynamics. To distinguish which of these mechanisms explains a given case of stasis in the fossil record, stasis must first be rigorously documented in a high-resolution stratigraphic time series of fossi...

The semi-dominant Br mutation affects presphenoid growth, producing the facial retrognathism and globular neurocranial vault that characterize heterozygotes. We analysed the impact of this mutation on skull shape, comparing heterozygotes to wildtype mice, to determine if the effects are skull-wide or confined to the sphenoid region targeted by the...

Canalization may play a critical role in molding patterns of integration when variability is regulated by the balance between processes that generate and remove variation. Under these conditions, the interaction among those processes may produce a dynamic structure of integration even when the level of variability is constant. To determine whether...

Although it is well known that many mutations influence phenotypic variability as well as the mean, the underlying mechanisms for variability effects are very poorly understood. The brachymorph (bm) phenotype results from an autosomal recessive mutation in the phosphoadenosine-phosphosulfate synthetase 2 gene (Papps2). A major cranial manifestation...

Phenotypic variability is often taken for granted by evolutionary biologists even though variability is generally regarded as limited and nonrandom. Efforts to understand processes limiting and structuring variation have tended to focus on evolutionary mechanisms, especially stabilizing selection. In theory, stabilizing selection leads to the evolu...

Consideration of the ways in which ontogenetic development may be modified to give morphological novelty provides a conceptual framework that can greatly assist in formulating and testing hypotheses of patterns and constraints in evolution. Previous attempts to identify distinct modes of ontogenetic modification have been inconsistent or ambiguous...

A/WySnJ mice are an inbred strain that develops cleft lip with or without cleft palate (CL/P) with a frequency of 25-30% and a predominantly unilateral expression pattern. As in humans, the pattern of incomplete penetrance, and variable and frequent unilateral expression suggests a role for altered regulation of variability (developmental stability...

Geometric Morphometrics for Biologists is an introductory textbook for a course on geometric morphometrics, written for graduate students and upper division undergraduates, covering both theory of shape analysis and methods of multivariate analysis. It is designed for students with minimal math background; taking them from the process of data colle...

In the absence of processes regulating morphogenesis and growth, phenotypic variance of a population experiencing no selective mortality should increase throughout ontogeny. To determine whether it does, we measure variance of skull shape using geometric morphometrics and examine its ontogenetic dynamics in the precocial cotton rat (Sigmodon fulviv...

A new voice in the nature-nurture debate can be heard at the interface between evolution and development. Phenotypic integration--or, how large numbers of characteristics are related to make up the whole organism, and how these relationships evolve and change their function--is a major growth area in research, attracting the attention of evolutiona...

Heterochrony, evolutionary changes in rate or timing of development producing parallelism between ontogeny and phylogeny, is viewed as the most common type of evolutionary change in development. Alternative hypotheses such as heterotopy, evolutionary change in the spatial patterning of development, are rarely entertained. We examine the evidence fo...

Variation in neonatal maturity among mammals is often explained by variation in gestation length, but species may also differ in developmental rate, a quantity that is difficult to measure because the conventional formalism makes two important and potentially unrealistic assumptions: (1) ontogeny of form can be described by a single line, and (2) s...

To the extent that growth markers provide more information about developmental processes than is typically available in ontogenetic shape analyses, analyses of them are richer than those relying on size and shape data alone. Most workers will not have access to that kind of data because most species do not naturally record growth processes, and few...

Disparity appears to decrease or remain stable over geological time in numerous groups. This pattern is sometimes explained in terms of developmental constraints, but labile developmental systems might produce the same pattern should novelties interact, counterbalancing their individual effects. We test the hypothesis that counterbalancing can redu...

Heterochrony, evolutionary changes in rate or timing of development producing parallelism between ontogeny and phylogeny, is viewed as the most common type of evolutionary change in development. Alternative hypotheses such as heterotopy, evolutionary change in the spatial patterning of development, are rarely entertained. We examine the evidence fo...

Morphologists and systematists have long suspected that dietary consistency can affect skull and dental form in mammals. We examined plasticity of skull shape and tooth morphology in prairie deer mice (Peromyscus maniculatus bairdii) by feeding mice diets that differed in consistency but not nutritional quality. Shape differences were analyzed qual...

Heterochrony, change in developmental rate and timing, is widely recognized as an agent of evolutionary change. Heterotopy, evolutionary change in spatial patterning of development, is less widely known or understood. Although Haeckel coined the term as a complement to heterochrony in 1866, few studies have detected heterotopy or even considered th...

TO test the hypothesis that developmental integration coordinates evolutionary change through history, we dissect the spatial and temporal integration of ontogenetic allometries of piranha body form and examine the evolutionary coordination among ontogenetic features by a phylogenetic analysis. Few of our characters provide evidence in support of t...

Heterochrony, change in developmental rate and timing, is widely recognized as an agent of evolutionary change. Heterotopy, evolutionary change in spatial patterning of development, is less widely known or understood. Although Haeckel coined the term as a complement to heterochrony in 1866, few studies have detected heterotopy or even considered th...

Piranhas, like many teleosts, change their diets on both ontogenetic and phylogenetic time scales. Prior studies have suggested that pervasive morphological changes in body form on a phylogenetic time scale may be related to changes in diet, but previous reports have found little shape change in piranhas on an ontogenetic time scale. We re-examine...

Developmental constraint is a theoretically important construct bridging ontogenetic and evolutionary studies. We propose a new operationalization of this notion that exploits the unusually rich measurement structure of landmark data. We represent landmark configurations by their partial warps, a basis for morphospace that represents a set of local...

Because development is epigenetic, diverse aspects of morphology are integrated during ontogeny. Using the method of thin-plate splines, and the decomposition of these splines by their principal warps, we examine the ontogeny of integrated features of skull growth of the cotton rat, Sigmodon fulviventer as observed in landmark locations in the vent...

Developmental constraints can be interpreted as factors of developmental origin responsible for covariation among measured variables. Several hypotheses have been proposed to link the possession of such constraints to subsequent evolution. Using confirmatory factor analysis, we compare developmental factors across selected taxa of cotton rats, genu...

Skulls of seven rodent species were measured by a triangulation-measurement scheme and subjected to multivariate analysis. Results were compared to studies from the literature based on traditional measurements for the proportion of variance explained by overall body size, the number of shape factors, and the ease of interpretation of these factors....

We examined the degree to which measurements of the skull and jaw are interdependent at six ages of Sigmodon fulviventer. The extent to which measurements are interdependent varies throughout growth, generally increasing until puberty, when it declines to pre-pubescent levels. Growth and other factors explain variable proportions of integration. Ou...

Patterns of variation and covariation within populations can influence how characters respond to natural selection and random genetic drift and so constrain the ability of natural selection to modify the phenotype. We examined several potential developmental and functional explanations of character covariation throughout ontogeny using known-age sa...

I used confirmatory factor analysis to evaluate the ability of causal developmental models to predict observed phenotypic integration in limb and skull measures at five stages of postnatal ontogeny in the laboratory rat. To analyze the dynamics of phenotypic integration, I fit successive age-classes simultaneously to a common model. Growth was the...

This study describes a procedure for constructing and evaluating developmental models by using confirmatory factor analysis which predicts covariation among morphological measures. The principal advantage of confirmatory factor analysis lies in its ability to reject poorly fitting hypotheses in favor of those better able to reconstruct observed var...

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