Philip J. Bergmann

ALTERNATE PATHWAYS OF BODY SHAPE EVOLUTION TRANSLATE INTO COMMON PATTERNS OF LOCOMOTOR EVOLUTION IN TWO CLADES OF LIZARDS

Body shape has a fundamental impact on organismal function, but it is unknown how functional morphology and locomotor performance and kinematics relate across a diverse array of body shapes. We showed that although patterns of body shape evolution differed considerably between lizards of the Phrynosomatinae and Lerista, patterns of locomotor evolution coincided between clades. Specifically, we found that the phrynosomatines evolved a stocky phenotype through body widening and limb shortening, whereas Lerista evolved elongation through body lengthening and limb shortening. In both clades, relative limb length played a key role in locomotor evolution and kinematic strategies, with long‐limbed species moving faster and taking longer strides. In Lerista, the body axis also influenced locomotor evolution. Similar patterns of locomotor evolution were likely due to constraints on how the body can move. However, these common patterns of locomotor evolution between the two clades resulted in different kinematic strategies and levels of performance among species because of their morphological differences. Furthermore, we found no evidence that distinct body shapes are adaptations to different substrates, as locomotor kinematics did not change on loose or solid substrates. Our findings illustrate the importance of studying kinematics to understand the mechanisms of locomotor evolution and phenotype‐function relationships.

Directional Evolution of Stockiness Coevolves with Ecology and Locomotion in Lizards

Although studied in many taxa, directional macroevolution remains difficult to detect and quantify. We present an approach for detecting directional evolution in subclades of species when relatively few species are sampled, and apply it to studying the evolution of stockiness in Phrynosomatine lizards. Our approach is more sensitive to detecting the tempo of directional evolution than other available approaches. We use ancestral reconstruction and phylogenetic mapping of morphology to characterize the direction and magnitude of trait evolution. We demonstrate a directional trend toward stockiness in horned lizards, but not their sister groups, finding that stockier species tend to have relatively short and wide bodies, and relatively short heads, tails, and limbs. Ornstein-Uhlenbeck models show that the directional trend in horned lizards is due to a shift in selective regime and stabilizing selection as opposed to directional selection. Bayesian evolutionary correlation analyses indicate that stockier species run more slowly and eat a larger proportion of ants. Furthermore, species with larger horns tend to be slower and more ant-specialized. Directional evolution toward a stocky body shape has evolved in conjunction with changes in a suite of traits, representing a complex example of directional macroevolution.

VERTEBRAL EVOLUTION AND THE DIVERSIFICATION OF SQUAMATE REPTILES

Taxonomic, morphological, and functional diversity are often discordant and independent components of diversity. A fundamental and largely unanswered question in evolutionary biology is why some clades diversify primarily in some of these components and not others. Dramatic variation in trunk vertebral numbers (14 to >300) among squamate reptiles coincides with different body shapes, and snake‐like body shapes have evolved numerous times. However, whether increased evolutionary rates or numbers of vertebrae underlie body shape and taxonomic diversification is unknown. Using a supertree of squamates including 1375 species, and corresponding vertebral and body shape data, we show that increased rates of evolution in vertebral numbers have coincided with increased rates and disparity in body shape evolution, but not changes in rates of taxonomic diversification. We also show that the evolution of many vertebrae has not spurred or inhibited body shape or taxonomic diversification, suggesting that increased vertebral number is not a key innovation. Our findings demonstrate that lineage attributes such as the relaxation of constraints on vertebral number can facilitate the evolution of novel body shapes, but that different factors are responsible for body shape and taxonomic diversification.

Tail Autotomy, Tail Size, and Locomotor Performance in Lizards*

The effect of tail autotomy on locomotor performance has been studied in a number of lizard species. Most of these studies (65%) show that tail autotomy has a negative effect on sprint speed, some studies (26%) show no effect of autotomy on sprint speed, and a few (9%) show a positive effect of autotomy on sprint speed. A variety of hypotheses have been proposed to explain the variation across these studies, but none has been tested. We synthesize these data using meta-analysis and then test whether any of four variables explain the variation in how tail autotomy impacts sprint speed: (1) differences in methodology in previous studies, (2) phylogeny, (3) relative tail size, and (4) habitat use. We find little evidence that methodology or habitat use influences how sprint speed changes following tail autotomy. Although the sampling is phylogenetically sparse, phylogeny appears to play a role, with skinks and iguanids showing fairly consistent decreases in speeds after autotomy and with lacertids and geckos showing large variation in how autotomy impacts speed. After removing two outlying species with unusually large and long tails (Takydromus sp.), we find a positive relationship between relative tail size and sprint speed change after autotomy. Lizards with larger tails exhibit a greater change in speed after tail loss. This finding suggests that future studies of tail autotomy and locomotor performance might profitably incorporate variation in tail size and that species-specific responses to autotomy need to be considered.

Genetic Bases of Fungal White Rot Wood Decay Predicted by Phylogenomic Analysis of Correlated Gene-Phenotype Evolution

Fungal decomposition of plant cell walls (PCW) is a complex process that has diverse industrial applications and huge impacts on the carbon cycle. White rot (WR) is a powerful mode of PCW decay in which lignin and carbohydrates are both degraded. Mechanistic studies of decay coupled with comparative genomic analyses have provided clues to the enzymatic components of WR systems and their evolutionary origins, but the complete suite of genes necessary for WR remains undetermined. Here, we use phylogenomic comparative methods, which we validate through simulations, to identify shifts in gene family diversification rates that are correlated with evolution of WR, using data from 62 fungal genomes. We detected 409 gene families that appear to be evolutionarily correlated with WR. The identified gene families encode well-characterized decay enzymes, e.g., fungal class II peroxidases and cellobiohydrolases, and enzymes involved in import and detoxification pathways, as well as 73 gene families that have no functional annotation. About 310 of the 409 identified gene families are present in the genome of the model WR fungus Phanerochaete chrysosporium and 192 of these (62%) have been shown to be upregulated under ligninolytic culture conditions, which corroborates the phylogeny-based functional inferences. These results illuminate the complexity of WR and suggest that its evolution has involved a general elaboration of the decay apparatus, including numerous gene families with as-yet unknown exact functions.

Growth of the Original Tail in Anolis grahami: Isometry of the Whole Is a Product of Regional Differences

The original tail of lizards is a segmental structure, each segment containing a vertebra. We examine how the growth of the original tail of Anolis grahami is characterized as a single structure and as a structure composed of discrete segments. It is hypothesized that the tail grows isometrically both in its entirety and regionally. The results reveal that the entire tail grows isometrically with reference to SVL but that this isometric growth pattern results from differential growth in successive regions of the tail. Seg- mentally the tail grows faster proximally than distally and incorporates a middle transitional region. These findings may have implications for the various patterns of tail growth in squamates with different functional

Taxonomic Identity in Microbial Eukaryotes: A Practical Approach Using the Testate Amoeba Centropyxis to Resolve Conflicts Between Old and New Taxonomic Descriptions

ABSTRACT. The present work focuses on 12 taxa of the genus Centropyxis Stein, 1857 to explore the conflict between traditional and contemporary taxonomic practices. We examined the morphology, biometry, and ecology of 2,120 Centropyxis individuals collected from Tiete River, Sao Paulo, Brazil; with these new data we studied the consistency of previously described species, varieties, and forms. We encountered transitional forms of test morphology that undermine specific and varietal distinctions for three species and nine varieties. Biometrical analyses made comparing the organisms at the species level suggest a lack of separation between Centropyxis aculeata and Centropyxis discoides, and a possible distinction for Centropyxis ecornis based on spine characteristics. However, incongruence between recent and previous surveys makes taking any taxonomic–nomenclatural actions inadvisable, as they would only add to the confusion. We suggest an explicit and objective taxonomic practice in order to enhance our taxonomic and species concepts for microbial eukaryotes. This will allow more precise inferences of taxon identity for studies in other areas.

Tail growth in Chamaeleo dilepis (Sauria: Chamaeleonidae): functional implications of segmental patterns

Patterns of growth of caudal vertebrae in the chameleon Chamaeleo dilepis were determined using principal component analysis, and compared to growth of the entire tail relative to snout–vent length. Despite significant positive allometry of the whole tail, growth rates of vertebrae differed along the length of the tail. Specifically, there was a proximal region that grew positively allometrically, and an extensive distal portion that grew with negative allometry. Intervening, was a short transitional region of approximate isometry. Positive allometry of the entire tail resulted from the extensive proximal region that grew in this manner. Although the region of positive allometry extended further caudad than the m. caudofemoralis longus, m. retractor penis magnus, and m. ischiocaudalis, its extent correlated more closely with the presence of neural spines (which are used as a proxy for the extent of the m. transversospinalis) and with tail coiling in this species. The positively allometric region housed the non-segmental musculature of the tail and did not bend, and the negatively allometric region identified the portion of the tail that was prehensile.

Maximal Caudal Autotomy in Podarcis hispanica (Lacertidae): The Caudofemoralis Muscle Is Not Sundered

Abstract In recent years, the pattern of maximal caudal autotomy in lizards has come under consideration, with attention being focused on how nonsegmental muscles in the tail base, specifically the m. caudofemoralis longus and the m. retractor penis magnus, may limit autotomy where they cross autotomy planes or, alternatively, how they may be ruptured if maximal autotomy is practiced. In this paper, we demonstrate that in the lacertid lizard Podarcis hispanica a number of autotomic vertebrae are spanned by the m. caudofemoralis longus, that maximal caudal autotomy does occur, and that the caudofemoralis muscle dissociates from its vertebral attachments but is not torn in the process. Anatomical and histological data reveal that this muscle has a specialized structure and relationship with surrounding muscles, skeletal elements, and connective tissues that result in minimal damage upon maximal autotomy. Furthermore, upon caudal regeneration, the m. caudofemoralis longus reestablishes contact with the newly formed cartilaginous axial skeleton of the tail.

MAMMALIAN POSTNATAL GROWTH ESTIMATES: THE INFLUENCE OF WEANING ON THE CHOICE OF A COMPARATIVE METRIC

Abstract In an investigation of the postnatal growth of the vertebral column of the Norway rat (Rattus norvegicus), we recorded hind-foot length as a standard metric, along with skull, tail, femur, and tibia lengths, against which to compare the growth of axial components. We confirmed a nonlinear relationship of head–body length against hind-foot length, tail length, and tibia length across the time course from neonate to adult and also discovered a nonlinear relationship between both skull and femur length to head–body length. Differences in growth rate are directly related to preweaning and postweaning periods. The pattern of differential growth was distinctly least pronounced for femoral length. We therefore advocate the latter as the most appropriate to use as an easily measured proxy for growth across the entire neonate to adult growth period. This study reveals implications for the choice of optimal variables used as size proxies and also suggests functional implications of shifts in form–function relationships from unweaned to weaned individuals. However, variation in body form across mammals and altricial versus precocial modes of natal expression will continue to complicate the search for appropriate comparative metrics in the study of the development and evolution of body form.