Macroevolutionary Approaches Research Articles

Gene loss and relaxed selection of plaat1 in vertebrates adapted to low-light environments.

Gene loss is an important mechanism for evolution in low-light or cave environments where visual adaptations often involve a reduction or loss of eyesight. The plaat gene family encodes phospholipases essential for the degradation of organelles in the lens of the eye. These phospholipases translocate to damaged organelle membranes, inducing them to rupture. This rupture is required for lens transparency and is essential for developing a functioning eye. Plaat3 is thought to be responsible for this role in mammals, while plaat1 is thought to be responsible in other vertebrates. We used a macroevolutionary approach and comparative genomics to examine the origin, loss, synteny and selection of plaat1 across bony fishes and tetrapods. We showed that plaat1 (probably ancestral to all bony fish + tetrapods) has been lost in squamates and is significantly degraded in lineages of low-visual-acuity and blind mammals and fishes. Our findings suggest that plaat1 is important for visual acuity across bony vertebrates, and that its loss through relaxed selection and pseudogenization may have played a role in the repeated evolution of visual systems in low-light environments. Our study sheds light on the importance of gene-loss in trait evolution and provides insights into the mechanisms underlying visual acuity in low-light environments.

Tangled Banks, Braided Rivers and Complex Hierarchies: Beyond Microevolution and Macroevolution.

Ever since the Modern Synthesis, a debate about the relationship between microevolution and macroevolution has persisted - specifically, whether they are equivalent, distinct, or explain one another. How one answers this has become shorthand for a much broader set of theoretical debates in evolutionary biology. Here, we examine microevolution and macroevolution in the context of the vast proliferation of data, knowledge, and theory since the advent of the Modern Synthesis. We suggest that traditional views on microevolution and macroevolution are too binary and reductive. For example, patterns and processes are not confined to micro- and macro- domains; they are interconnected at various temporal and spatial scales and across hierarchical entities. Further, biological entities have variably fuzzy boundaries, and evolutionary processes that influence macroevolution occur at micro- and macro- levels. In addition, these conceptual advances in phylodynamics have yet to be fully integrated with contemporary macroevolutionary approaches. Finally, holding microevolution and macroevolution as distinct domains thwarts synthesis and collaboration on important research questions. We propose that the focal entities and processes considered by evolutionary studies be contextualized within the newfound complexity of the multidimensional, multi-modal, multi-level phylogenetic system.

Tropical Origin, Global Diversification, and Dispersal in the Pond Damselflies (Coenagrionoidea) Revealed by a New Molecular Phylogeny.

The processes responsible for the formation of Earth's most conspicuous diversity pattern, the latitudinal diversity gradient (LDG), remain unexplored for many clades in the Tree of Life. Here, we present a densely sampled and dated molecular phylogeny for the most speciose clade of damselflies worldwide (Odonata: Coenagrionoidea) and investigate the role of time, macroevolutionary processes, and biome-shift dynamics in shaping the LDG in this ancient insect superfamily. We used process-based biogeographic models to jointly infer ancestral ranges and speciation times and to characterize within-biome dispersal and biome-shift dynamics across the cosmopolitan distribution of Coenagrionoidea. We also investigated temporal and biome-dependent variation in diversification rates. Our results uncover a tropical origin of pond damselflies and featherlegs ~105 Ma, while highlighting the uncertainty of ancestral ranges within the tropics in deep time. Even though diversification rates have declined since the origin of this clade, global climate change and biome-shifts have slowly increased diversity in warm- and cold-temperate areas, where lineage turnover rates have been relatively higher. This study underscores the importance of biogeographic origin and time to diversify as important drivers of the LDG in pond damselflies and their relatives, while diversification dynamics have instead resulted in the formation of ephemeral species in temperate regions. Biome-shifts, although limited by tropical niche conservatism, have been the main factor reducing the steepness of the LDG in the last 30 Myr. With ongoing climate change and increasing northward range expansions of many damselfly taxa, the LDG may become less pronounced. Our results support recent calls to unify biogeographic and macroevolutionary approaches to improve our understanding of how latitudinal diversity gradients are formed and why they vary across time and among taxa.

Spiritual Foundations for an Ecologically Sustainable Society

This article takes a broad macroevolutionary approach to our changing relationship to Nature in the light of the teachings or the Bahá’í Faith. It suggests that humanity is in a process of evolving consciousness leading to the development of a new planetary culture based on spiritual principles. In an ecological sense, humanity has in many respects appeared to be a delinquent species running out of control. Within a larger vision of humanity’s spiritual and social evolution, however, the present environmental crisis and the race’s reaction to it can be seen as portending a momentous transformation. The process of evolving consciousness that can be discerned in emerging knowledge in physics, ecology, psychology, and other fields of science is leading to the possibility of a mature cooperative relationship between humanity and the ecosphere which gave it birth. After a brief overview of the current range of responses to environmental issues and the view of Nature on which they are based, this article will explore the basic attitudes to Nature contained within the Bahá’í writings. The second part of the article examines how the emergence of an ecologically sustainable social order is linked to basic principles of the Bahá’í Faith. Implicit throughout is the Bahá’í view of the balance and cohesion of material and spiritual realities.
 * An earlier version of this article appeared in the Journal of Bahá’í Studies 2.1 (1989): 33–57. A special pamphlet version was co-published with the Bahá’í International Community–Office of the Environment and was distributed at the 1992 Earth Summit in Brazil. The updated version in this issue was prepared for Bahá’í World Yearbook 1992-93.

Explosive radiation at the origin of Old World fruit bats (Chiroptera, Pteropodidae)

Pteropodidae constitutes one of the most diverse bat families. These bats have evolved a phytophagous diet, likely lost laryngeal echolocation capability, and attained the largest body sizes among bats. Previous phylogenetic studies suggested that the family might have experienced an explosive diversification at its origin. Here, we readdress this hypothesis using a macroevolutionary approach based on Bayesian statistics (BAMM), a sampling of 139 pteropodid species, and divergence date estimates obtained in a comprehensive phylogenetic study of Chiroptera with multiple fossil calibration points. We evaluated the effect of missing data and of a reduced outgroup by repeating the analyses across simulated complete phylogenies and across a comprehensive Yinpterochiroptera phylogeny, respectively. Additionally, we performed an alternative analysis to detect diversification-rate shifts through time, the birth-death-shift method. In contrast with a previous study, we found strong statistical signals of rapid diversification at the origin of Pteropodidae. BAMM also detected diversification-rate shifts (increases) at the origin of Pteropus, as well as at crown Hipposideridae and Rhinolophidae. The birth-death-shift method detected a shift at approximately 25 million years ago, the estimated crown ages of both Pteropodidae and Hipposideridae. Our results point to a complex dynamics in the evolution of bat families, likely related to key innovations, demographic factors, and environmental opportunity enhanced by global-scale climatic and geographic changes.

Shoot-level flammability across the Dracophyllum (Ericaceae) phylogeny: evidence for flammability being an emergent property in a land with little fire.

Plant flammability varies across species, but the evolutionary basis for this variation is not well understood. Phylogenetic analysis of interspecific variation in flammability can provide insights into the evolution of plant flammability. We measured four components of flammability (ignitability, sustainability, combustibility and consumability) to assess the shoot-level flammability of 21 species of Dracophyllum (Ericaceae). Using a macroevolutionary approach, we explored phylogenetic patterns of variation in shoot-level flammability. Shoot-level flammability varied widely in Dracophyllum. Species in the subgenus Oreothamnus had higher flammability and smaller leaves than those in the subgenus Dracophyllum. Shoot flammability (ignitability, combustibility and consumability) and leaf length showed phylogenetic conservatism across genus Dracophyllum, but exhibited lability among some closely related species, such as D.menziesii and D.fiordense. Shoot flammability of Dracophyllum species was negatively correlated with leaf length and shoot moisture content, but had no relationship with the geographic distribution of Dracophyllum species. Shoot-level flammability varied widely in the genus Dracophyllum, but showed phylogenetic conservatism. The higher flammability of the subgenus Oreothamnus may be an incidental or emergent property as a result of the evolution of flammability-related traits, such as smaller leaves, which were selected for other functions and incidentally changed flammability.

Phylogenetic analysis of secondary metabolites in a plant community provides evidence for trade-offs between biotic and abiotic stress tolerance

Plants' responses to conflicting stresses may result in physiological trade-offs due to the inter-dependent and costly nature of physiological investments. Physiological tradeoffs have been proved within species, but to what extent these trade-offs are the result of phylogenetic constraints remains poorly known. Environmental stresses can vary widely in different biomes, and therefore assessing physiological tradeoffs across species must account for this variation. One way of doing so is to assess it within a community, where the co-occurring species have faced a shared combination of filters to establish. Considering a representative sample of species in a single community, we use a macroevolutionary approach to test the hypothesis that plant physiological trade-offs are evolutionarily conserved within this community (i.e., closely-related species tend to solve the trade-offs similarly). We analyze the content of five metabolites in thirty co-occurring plant species, capturing their range of contrasting exposures to abiotic and biotic stresses (growing solitary and in vegetation patches). Our results support that species investment in response to abiotic stress (i.e., proline and abscisic acid content) is traded off against their investment to face biotic stress (i.e., jasmonic acid and salicylic acid), shown by the contrasting loadings of these two groups of metabolites in the first axes of a principal component analysis (PCA). In addition, the metabolic strategies observed in this community are evolutionarily conserved, as closely related species tend to have similar scores in this PCA, and thus resemble each other in their balance. This is shown by a significant phylogenetic signal in the species’ scores along the first axes of the PCA. Incorporating the evolutionary history of plant species into physiological studies can help to understand the response of plants to multiple stresses currently acting in ecological communities.

Evolution of Reproductive Behavior.

Behaviors associated with reproduction are major contributors to the evolutionary success of organisms and are subject to many evolutionary forces, including natural and sexual selection, and sexual conflict. Successful reproduction involves a range of behaviors, from finding an appropriate mate, courting, and copulation, to the successful production and (in oviparous animals) deposition of eggs following mating. As a consequence, behaviors and genes associated with reproduction are often under strong selection and evolve rapidly. Courtship rituals in flies follow a multimodal pattern, mediated through visual, chemical, tactile, and auditory signals. Premating behaviors allow males and females to assess the species identity, reproductive state, and condition of their partners. Conflicts between the “interests” of individual males, and/or between the reproductive strategies of males and females, often drive the evolution of reproductive behaviors. For example, seminal proteins transmitted by males often show evidence of rapid evolution, mediated by positive selection. Postmating behaviors, including the selection of oviposition sites, are highly variable and Drosophila species span the spectrum from generalists to obligate specialists. Chemical recognition features prominently in adaptation to host plants for feeding and oviposition. Selection acting on variation in pre-, peri-, and postmating behaviors can lead to reproductive isolation and incipient speciation. Response to selection at the genetic level can include the expansion of gene families, such as those for detecting pheromonal cues for mating, or changes in the expression of genes leading to visual cues such as wing spots that are assessed during mating. Here, we consider the evolution of reproductive behavior in Drosophila at two distinct, yet complementary, scales. Some studies take a microevolutionary approach, identifying genes and networks involved in reproduction, and then dissecting the genetics underlying complex behaviors in D. melanogaster. Other studies take a macroevolutionary approach, comparing reproductive behaviors across the genus Drosophila and how these might correlate with environmental cues. A full synthesis of this field will require unification across these levels.

Transitions between foot postures are associated with elevated rates of body size evolution in mammals

Terrestrial mammals have evolved various foot postures: flat-footed (plantigrady), tiptoed (digitigrady), and hooved (unguligrady) postures. Although the importance of foot posture on ecology and body size of mammalian species has been widely recognized, its evolutionary trajectory and influence on body size evolution across mammalian phylogeny remain untested. Taking a Bayesian phylogenetic approach combined with a comprehensive dataset of foot postures in 880 extant mammalian species, we investigated the evolutionary history of foot postures and rates of body size evolution, within the same posture and at transitions between postures. Our results show that the common ancestor of mammals was plantigrade, and transitions predominantly occurred only between plantigrady and digitigrady and between digitigrady and unguligrady. At the transitions between plantigrady and digitigrady and between digitigrady and unguligrady, rates of body size evolution are significantly elevated leading to the larger body masses of digitigrade species (∼1 kg) and unguligrade species (∼78 kg) compared with their respective ancestral postures [plantigrady (∼0.75 kg) and digitigrady]. Our results demonstrate the importance of foot postures on mammalian body size evolution and have implications for mammalian body size increase through time. In addition, we highlight a way forward for future studies that seek to integrate morphofunctional and macroevolutionary approaches.

Evidence for distinct evolutionary optima in the morphology of migratory and resident birds

Seasonal migration is prevalent in approximately one fifth of all bird species. Due to the high energetic costs of migration, consistent morphological patterns can be observed across migratory species. These include longer, more pointed wings and shorter tails in comparison to resident species. While evidence for distinct morphological adaptations of migratory species is well‐established, little is known about evolutionary trajectories of these morphological adaptations within groups of related species, and whether the evolution of these traits is consistent across different bird families. Here we apply a macroevolutionary approach to address this knowledge gap by comparing morphological traits and their evolution in migratory and resident species across eight families of passerine birds. We find a significant relationship of wing shape and tail length with migratory distance. When testing the evolution of wing shape and tail length in migratory and resident species, we find that a model with two distinct optima for migratory and resident species better explains the evolution of each morphological trait than a model with one evolutionary optimum. Thus, our results suggest consistent adaptive peaks in the evolution of these traits, and consistent selective pressures which improve the efficiency of long‐distance flight in migratory species and the efficiency of foraging flight in resident species. Our data provide a novel insight into the general patterns of morphological trait evolution in birds, thereby expanding the existing knowledge to a macroevolutionary scale in a field that has previously been dominated by species‐ or genera‐ specific studies.

Ecology shapes the evolutionary trade-off between predator avoidance and defence in coral reef butterflyfishes.

Antipredator defensive traits are thought to trade-off evolutionarily with traits that facilitate predator avoidance. However, complexity and scale have precluded tests of this prediction in many groups, including fishes. Using a macroevolutionary approach, we test this prediction in butterflyfishes, an iconic group of coral reef inhabitants with diverse social behaviours, foraging strategies and antipredator adaptations. We find that several antipredator traits have evolved adaptively, dependent primarily on foraging strategy. We identify a previously unrecognised axis of diversity in butterflyfishes where species with robust morphological defences have riskier foraging strategies and lack sociality, while species with reduced morphological defences feed in familiar territories, have adaptations for quick escapes and benefit from the vigilance provided by sociality. Furthermore, we find evidence for the constrained evolution of fin spines among species that graze solely on corals, highlighting the importance of corals, as both prey and structural refuge, in shaping fish morphology.

Plant-herbivore interactions and secondary metabolites of plants: Ecological and evolutionary perspectives

AbstractBackground: Throughout disciplines including paleontology and molecular biology, hence using the fossil record or DNA sequences, ancestral and current plant-herbivore associations mediated by secondary compounds have been assessed. The coevolutionary model of “escape and radiation” predicts adaptive patterns at micro- and macro-evolutionary scale, resulted from the plant-herbivore interaction.Questions: The study of plant-herbivore interaction and secondary metabolites, has been bias for two main reasons: (1) the interdisciplinary study of the interaction has “atomized" the field. (2) The conceptual framework of coevolution favored analysis either within populations or across taxa.Methods: I review the evolutionary history of the interaction and secondary metabolites, from paleontological and palebiochemical data. Then, based on empirical evidence of quantitative genetics and comparative methods, I examine the main assumptions of micro- and macro-evolutionary postulates of the coevolutionary model. Further, I overview the analytical approach for the study of plant defense within-species and across phylogeny. Results: Within species, (1) the coevolutionary dynamics shaping plants and herbivore phenotypes, and (2) the role of plant chemistry to constraint ecological interactions, are the most stressed patterns. Across phylogeny, (1) the role of plant chemistry to constraint insect host shifts, and (2) the implications of, and mechanism behind the evolutionary novelties, are more recently assessed.Conclusion: I suggest that future research should integrate both conceptual and analytical perspectives of micro- and macro-evolutionary approaches. One promising direction relies in modern molecular techniques that may open new research avenues by providing evidence for the function of complex genetic and genomic machineries behind biotic interactions.

Has frugivory influenced the macroecology and diversification of a tropical keystone plant family?

Seed dispersal by fruit-eating animals is a pivotal ecosystem function in tropical forests, but the role that frugivores have played in the biogeography and macroevolution of species-rich tropical plant families remains largely unexplored. This project investigates how frugivory-relevant plant traits (e.g. fruit size, fruit color, fruit shape etc.) are distributed within the angiosperm family of palms (Arecaceae), how this relates to diversification rates, and whether and how it coincides with the global biogeographic distribution of vertebrate frugivores (birds, bats, primates, other frugivorous mammals) and their ecological traits (e.g. diet specialization, body size, flight ability, color vision etc.). Palms are particularly suitable because they are well studied, species-rich, characteristic of tropical rainforests, and dispersed by all groups of vertebrate seed dispersers. Using newly compiled data on species distributions and ecological traits in combination with phylogenies we will test (1) how fruit trait variability relates to palm phylogeny and other aspects of plant morphology (e.g. leaf size, plant height, growth form), (2) whether geographic variability in fruit traits correlates with geographic distributions of animal consumers and their traits, and (3) to what extent interaction-relevant plant traits are related to palm diversification rates. This combined macroecological and macroevolutionary approach allows novel insights into the global ecology and the evolution of a tropical keystone plant family. This is important for the conservation and sustainable management of tropical rainforests because palms are often key components of subsistence economies, ecosystem dynamics and carbon storage and therefore help to enhance nature’s goods, benefits and services to humanity.

Molecular ecology studies of species radiations: current research gaps, opportunities and challenges.

Understanding the drivers and limits of species radiations is a crucial goal of evolutionary genetics and molecular ecology, yet research on this topic has been hampered by the notorious difficulty of connecting micro- and macroevolutionary approaches to studying the drivers of diversification. To chart the current research gaps, opportunities and challenges of molecular ecology approaches to studying radiations, we examine the literature in the journal Molecular Ecology and revisit recent high-profile examples of evolutionary genomic research on radiations. We find that available studies of radiations are highly unevenly distributed among taxa, with many ecologically important and species-rich organismal groups remaining severely understudied, including arthropods, plants and fungi. Most studies employed molecular methods suitable over either short or long evolutionary time scales, such as microsatellites or restriction site-associated DNA sequencing (RAD-seq) in the former case and conventional amplicon sequencing of organellar DNA in the latter. The potential of molecular ecology studies to address and resolve patterns and processes around the species level in radiating groups of taxa is currently limited primarily by sample size and a dearth of information on radiating nuclear genomes as opposed to organellar ones. Based on our literature survey and personal experience, we suggest possible ways forward in the coming years. We touch on the potential and current limitations of whole-genome sequencing (WGS) in studies of radiations. We suggest that WGS and targeted ('capture') resequencing emerge as the methods of choice for scaling up the sampling of populations, species and genomes, including currently understudied organismal groups and the genes or regulatory elements expected to matter most to species radiations.

The Geography of Ecological Niche Evolution in Mammals

Convergent adaptive evolution of species' ecological niches-i.e., the appearance of similar niches in independent lineages-is the result of natural selection acting on niche-related species traits ("traits" hereafter) and contrasts with neutral evolution [1-4]. Although trait convergences are recognized as being of importance at the species scale, we still know little about the impact of species convergence on the overall trait and niche structure of entire biotas at large spatial scales [5]. Here, we map the convergent evolution of four traits (diet, body mass, activity cycle, and foraging strata) for mammal species and assemblages (defined at 200× 200km resolution) at a global scale. Using data on the geographic distributions, traits, and phylogenetic relationships of species and by comparing observed patterns of trait β-diversity to evolutionary neutral expectations, we show that trait convergence is not restricted to particular lineages but scales up to entire assemblages (i.e., whole species communities). We find region-wide biota convergence in traits between regions with similar climates, particularly between Australia and other continents. Pairs of assemblages that show trait divergence often involves Arctic regions where rapid evolutionary changes occurred in response to extreme climatic constraints. By integrating both macroecological and macroevolutionary approaches into a single framework, our study quantifies the crucial role of evolutionary processes such as natural selection in the spatial distribution and structure of large-scale species assemblages.

Sexual selection on male size drives the evolution of male-biased sexual size dimorphism via the prolongation of male development.

Sexual size dimorphism (SSD) arises when the net effects of natural and sexual selection on body size differ between the sexes. Quantitative SSD variation between taxa is common, but directional intraspecific SSD reversals are rare. We combined micro- and macroevolutionary approaches to study geographic SSD variation in closely related black scavenger flies. Common garden experiments revealed stark intra- and interspecific variation: Sepsis biflexuosa is monomorphic across the Holarctic, while S. cynipsea (only in Europe) consistently exhibits female-biased SSD. Interestingly, S. neocynipsea displays contrasting SSD in Europe (females larger) and North America (males larger), a pattern opposite to the geographic reversal in SSD of S. punctum documented in a previous study. In accordance with the differential equilibrium model for the evolution of SSD, the intensity of sexual selection on male size varied between continents (weaker in Europe), whereas fecundity selection on female body size did not. Subsequent comparative analyses of 49 taxa documented at least six independent origins of male-biased SSD in Sepsidae, which is likely caused by sexual selection on male size and mediated by bimaturism. Therefore, reversals in SSD and the associated changes in larval development might be much more common and rapid and less constrained than currently assumed.

The origins of Dinosauria: much ado about nothing

AbstractResearch this century has greatly improved our knowledge of the origin and early radiation of dinosaurs. The unearthing of several new dinosaurs and close outgroups from Triassic rocks from various parts of the world, coupled with improved phylogenetic analyses, has set a basic framework in terms of timing of events and macroevolutionary patterns. However, important parts of the early dinosauromorph evolutionary history are still poorly understood, rendering uncertain the phylogenetic position of silesaurids as either non‐dinosaur Dinosauriformes or ornithischians, as well as that of various early saurischians, such as Eoraptor lunensis and herrerasaurs, as either noneusaurischians or members of the sauropodomorph or theropod lineages. This lack of agreement in part derives from a patchy distribution of traits among early members of the main dinosauromorph lineages and requires a more meticulous assessment of characters and homologies than those recently conducted. Presently, the oldest uncontroversial dinosaur records come from Late Triassic (Carnian) rocks of South America, southern Africa and India, hinting at a south‐western Pangaea origin of the group. Besides, macroevolutionary approaches suggest that the rise of dinosaurs was a more gradual process than previously understood. Obviously, these tentative scenarios need to be tested by new fossil finds, which should also help close the major gaps recognized in the fossil record of Triassic dinosauromorphs.

Linking Life-History Traits, Ecology, and Niche Breadth Evolution in North American Eriogonoids (Polygonaceae)

Macroevolutionary and microevolutionary studies provide complementary explanations of the processes shaping the evolution of niche breadth. Macroevolutionary approaches scrutinize factors such as the temporal and spatial environmental heterogeneities that drive differentiation among species. Microevolutionary studies, in contrast, focus on the processes that affect intraspecific variability. We combine these perspectives by using macroevolutionary models in a comparative study of intraspecific variability. We address potential differences in rates of evolution of niche breadth and position in annual and perennial plants of the Eriogonoideae subfamily of the Polygonaceae. We anticipated higher rates of evolution in annuals than in perennials owing to differences in generation time that are paralleled by rates of molecular evolution. Instead, we found that perennial eriogonoid species present greater environmental tolerance (wider climate niche) than annual species. Niche breadth of perennial species has evolved two to four times faster than in annuals, while niche optimum has diversified more rapidly among annual species than among perennials. Niche breadth and average elevation of species are correlated. Moreover, niche breadth increases more rapidly with mean species elevation in perennials than in annuals. Our results suggest that both environmental gradients and life-history strategy influence rates and patterns of niche breadth evolution.

Disparity Changes in 370 Ma Devonian Fossils: The Signature of Ecological Dynamics?

Early periods in Earth's history have seen a progressive increase in complexity of the ecosystems, but also dramatic crises decimating the biosphere. Such patterns are usually considered as large-scale changes among supra-specific groups, including morphological novelties, radiation, and extinctions. Nevertheless, in the same time, each species evolved by the way of micro-evolutionary processes, extended over millions of years into the evolution of lineages. How these two evolutionary scales interacted is a challenging issue because this requires bridging a gap between scales of observation and processes. The present study aims at transferring a typical macro-evolutionary approach, namely disparity analysis, to the study of fine-scale evolutionary variations in order to decipher what processes actually drove the dynamics of diversity at a micro-evolutionary level. The Late Frasnian to Late Famennian period was selected because it is punctuated by two major macro-evolutionary crises, as well as a progressive diversification of marine ecosystem. Disparity was estimated through this period on conodonts, tooth-like fossil remains of small eel-like predators that were part of the nektonic fauna. The study was focused on the emblematic genus of the period, Palmatolepis. Strikingly, both crises affected an already impoverished Palmatolepis disparity, increasing risks of random extinction. The major disparity signal rather emerged as a cycle of increase and decrease in disparity during the inter-crises period. The diversification shortly followed the first crisis and might correspond to an opportunistic occupation of empty ecological niche. The subsequent oriented shrinking in the morphospace occupation suggests that the ecological space available to Palmatolepis decreased through time, due to a combination of factors: deteriorating climate, expansion of competitors and predators. Disparity changes of Palmatolepis thus reflect changes in the structure of the ecological space itself, which was prone to evolve during this ancient period where modern ecosystems were progressively shaped.

The Neolithic Macro-(R)evolution: Macroevolutionary Theory and the Study of Culture Change

The macroevolutionary approach in archaeology represents the most recent example in a long tradition of applying principles of biological evolution to the study of culture change. Archaeologists working within this paradigm see macroevolutionary theory as an effective response to the shortcomings of neo-Darwinian biological evolution for studying cultural evolution. Rather than operating at the level of individual traits, macroevolutionary archaeologists emphasize the role of hierarchical processes in culture change. While neo-Darwinian archaeologists disavow any element of human intent in culture change, to macroevolutionary archaeologists human agency is a key component of cultural evolution that allows cultures to respond to pressures more quickly and with greater degree of flexibility and directedness than found in biological evolution. Major culture change, when it happens, is likely to be rapid, even revolutionary, with periods of rapid change separated by periods of relative stasis of actively maintained stability. The emergence of Neolithic cultures has long been recognized as one of two periods of major revolutionary culture change in human prehistory. Here I examine the record for the Near East, tracing the empirical record for the origin of agriculture in this region, as well as other demographic, social, and ideological components of Neolithic emergence. While the empirical record from the Near East subscribes in a general way to basic principles of macroevolutionary theory, cultural evolution cannot be understood through appeal to principles of biological evolution alone, whether based in macroevolutionary theory or neo-Darwinianism. Instead, the key role of human agency in culture change distinguishes cultural evolution from biological evolution and requires a more pluralistic and less doctrinaire appeal to multiple models of change based in both the biological and social sciences.