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The study of trait evolution in modular animals is more complicated than that in solitary animals, because a single genotype of a modular colony can express an enormous range of phenotypic variation. Furthermore, traits can occur either at the module level or at the colony level. However, it is unclear how the traits at the colony level evolve. We test whether colony-level aggregate traits, defined as the summary statistics of a phenotypic distribution, can evolve. To quantify this evolutionary potential, we use parent-offspring pairs in two sister species of the bryozoan Stylopoma, grown and bred in a common garden breeding experiment. We find that the medians of phenotypic distributions are evolvable between generations of colonies. We also find that the structure of this evolutionary potential differs between these two species. Ancestral species align more closely with the direction of species divergence than the descendent species. This result indicates that aggregate trait evolvability can itself evolve.

Animals, fungi, and algae with complex multicellular bodies all evolved independently from unicellular ancestors. The early history of these major eukaryotic multicellular clades, if not their origins, co-occur with an extreme phase of global glaciations known as the Snowball Earth. Here, I propose that the long-term loss of low-viscosity environments due to several rounds global glaciation drove the multiple origins of complex multicellularity in eukaryotes and the subsequent radiation of complex multicellular groups into previously unoccupied niches. In this scenario, life adapts to Snowball Earth oceans by evolving large size and faster speeds through multicellularity, which acts to compensate for high-viscosity seawater and achieve fluid flow at sufficient levels to satisfy metabolic needs. Warm, low-viscosity seawater returned with the melting of the Snowball glaciers, and with it, by virtue of large and fast multicellular bodies, new ways of life were unveiled.

Colonial marine invertebrates, such as corals and bryozoans, have modular growth. Individual modules within a colony are homologous to an individual solitary animal body. But in contrast to the predominately sexual origin of solitary animal bodies, modules within a colony are always produced asexually. The repetition of modules and the indeterminism of their organization gives colonies the ability to grow in ways solitary animals cannot. Colonial invertebrates consequently grow in such a way as to resemble weeds, bushes, or trees. The multitude of growth forms of colonial invertebrates arise from differences how individual colonies within a species tend to invest their energy into modular growth, persistence, asexual propagation, and sexual reproduction. Moreover, many colonial invertebrates possess several body types, morphological polymorphism among modules, where modules qualitatively differ in shape, size, and function. In this paper, I propose a mechanism that links the origin of novel body types to the evolution of life‐history strategies among species. When colonies first evolve from solitary ancestors, the life‐history strategy of the colony remains constrained by the life‐history strategies of the individual modules within the colony until a new polymorph type evolves. The addition of novel body types within a colony introduces potential variation in life‐history strategies. Colonies can then change strategies by regulating the frequencies of body types within the colony. This, along with the ability of body types to simplify their structure permits colonies to evolve more complex life‐histories. Each new polymorph type that evolves permits more variation in colonial life‐histories to exist., When colonies first evolve from solitary ancestors, the life‐history strategy of the colony remains constrained by the life‐history strategies of the individual modules within the colony until a new polymorph type evolves. Colonies can evolve further strategies by regulating the frequencies of body types within the colony. This, along with the ability of body types to simplify their structure permits colonies to evolve more complex life‐histories. Each new polymorph type that evolves permits more variation in colonial life‐histories to exist., Research Highlights When coral or bryozoan colonies first evolve from solitary ancestors the life‐history strategy of the colony remains constrained by the life‐history strategies of the individual modules within the colony until a new body type evolves.

Bryozoans, simple invertebrates living on the sea floor, are emerging as a model system for understanding ecological and evolutionary processes on macroevolutionary scales.

The study of trait evolution in modular animals is more complicated than that in solitary animals, because a single genotype of a modular colony can express an enormous range of phenotypic variation. Furthermore, traits can occur either at the module level or at the colony level. However, it is unclear how the traits at the colony level evolve. We test whether colony-level aggregate traits, defined as the summary statistics of a phenotypic distribution, can evolve. To quantify this evolutionary potential, we use parent-offspring pairs in two sister species of the bryozoanStylopoma, grown and bred in a common garden breeding experiment. We find that the medians of phenotypic distributions are evolvable between generations of colonies. We also find that the structure of this evolutionary potential differs between these two species. Ancestral species align more closely with the direction of species divergence than the descendent species. This result indicates that aggregate trait evolvability can itself evolve.

Skeletal remains lying on landscape surfaces are useful for evaluating historical states of living populations, but across how much time can such resources inform management and conservation? Further, how do differences in environmental setting impact the breadth of the available timeseries? Using radiocarbon dated bones from across the globe, we evaluated the relationship between the maximum duration that bones persist on landscapes and the mean annual temperature of each locality. We found that bones can persist for several millennia in cold (high-latitude) settings and that there is a strong link (R2 > 0.9, p < 0.01) between local temperature and the logged duration of maximum bone persistence. This relationship provides an initial expectation for the duration across which skeletal remains from different settings can provide historical ecological context. Across the Holarctic, caribou (Rangifer tarandus) are the most abundant large mammal and arguably the most economically significant one for multiple human cultures, including serving as a key nutritional and cultural resource. For migratory caribou, movements between winter ranges and spring calving grounds are among the longest annual migrations of any terrestrial species and maintaining access to these areas is a top conservation priority. But how long have herds used particular calving grounds? Shed female antlers lying on the tundra provide insight into historical calving geography because they are shed within days of giving birth. Following antler surveys across the Coastal Plain calving grounds (Arctic National Wildlife Refuge, Alaska) of the Porcupine Caribou Herd (PCH), we radiocarbon dated three highly weathered female antlers. Antler ages ranged between ~1,600 and >3,000 calendar years ago. These antlers provide the first physical evidence of calving activity on the PCH calving grounds from previous millennia and substantiate the long ecological legacy of the Coastal Plain as a caribou calving ground.

Evolutionary pulses of complexity The evolution of land plants has been marked by an increase in the complexity of reproductive structures. Leslie et al . analyzed the temporal pattern of this increase in a study of fossil and extant land plants across the entire paleontological record. Reproductive complexity increased in two widely separated pulses corresponding to key innovations in reproductive biology: the origin of seeds in the very late Devonian and the origin of flowering plants in the mid-Cretaceous almost 250 million years later. After the origin of flowers, there was a rapid expansion in the morphological complexity of flowering plants. In contrast to many aspects of animal morphological diversity, which expanded early in evolutionary history, most complexity in plants was achieved relatively late. —AMS

The developmental and evolutionary principles of coloniality in marine animals remain largely unexplored. Although many common traits have evolved independently in different groups of colonial animals, questions about their significance for colonial life histories remain unanswered. In 2018 (Nov. 25 - Dec. 8), the inaugural course on the Evolution of Coloniality and Modularity took place at the Center for Marine Biology of the University of Sao Paulo (CEBIMAR-USP), Brazil. During the intensive two-week graduate-level course, we addressed some of the historical ideas about animal coloniality by focal studies in bryozoans, tunicates, cnidarians, and sponges. We discussed many historical hypotheses and ways to test these using both extant and paleontological data, and we carried direct observations of animal colonies in the different phyla to address questions about coloniality. We covered topics related to multi-level selection theory and studied colonial traits, including modular miniaturization, polymorphism, brooding, and allorecognition. Course participants carried out short research projects using local species of animals to address questions on allorecognition and regeneration in ascidians and sponges, fusion and chimerism in anthoathecate hydrozoans, and evolution of polymorphism in bryozoans. Although many questions remain unanswered, this course served as a foundation to continue to develop a developmental and evolutionary synthesis of clonal and modular development in colonial marine organisms.

Nearly half of the animal phyla contain species that propagate asexually via agametic reproduction, often forming colonies of genetically identical modules, that is, ramets, zooids, or polyps. Clonal reproduction, colony formation, and modular organization have important consequences for many aspects of organismal biology. Theories in ecology, evolution, and development are often based on unitary and, mainly, strictly sexually reproducing organisms, and though colonial animals dominate many marine ecosystems and habitats, recognized concepts for the study of clonal species are often lacking. In this review, we present an overview of the study of colonial and clonal animals, from the historic interests in this subject to modern research in a range of topics, including immunology, stem cell biology, aging, biogeography, and ecology. We attempt to portray the fundamental questions lying behind the biology of colonial animals, focusing on how colonial animals challenge several dogmas in biology as well as the remaining puzzles still to be answered, of which there are many.

Dinoflagellate algae form symbiotic partnerships with hosts from across a wide swath of the tree of life. New work shows that the genus Symbiodinium should now be considered a family, and importantly that the group is 110 million years older than previously thought. This expanded time period resolves long-standing questions about the evolution of photosymbiosis.

Colonial animals reconcile selection among organisms and colonies by limiting the evolutionary potential of organism., The evolution of modular colonial animals such as reef corals and bryozoans is enigmatic because of the ability for modules to proliferate asexually as whole colonies reproduce sexually. This reproductive duality creates an evolutionary tension between modules and colonies because selection operates at both levels. To understand how this evolutionary conflict is resolved, we compared the evolutionary potential of module- and colony-level traits in two species of the bryozoan Stylopoma, grown and bred in a common garden experiment. We find quantitatively distinct differences in the evolutionary potential of modular and colony traits. Contrary to solitary organisms, individual traits are not heritable from mother to daughter modules, but colony traits are strongly heritable from parent to offspring colonies. Colony-level evolution therefore dominates because no evolutionary change can accumulate among its modules.

The two major approaches to studying macroevolution in deep time are the fossil record and reconstructed relationships among extant taxa from molecular data. Results based on one approach sometimes conflict with those based on the other, with inconsistencies often attributed to inherent flaws of one (or the other) data source. Any contradiction between the molecular and fossil records represents a failure of our ability to understand the imperfections of our data, as both are limited reflections of the same evolutionary history. We therefore need to develop conceptual and mathematical models that jointly explain our observations in both records. Fortunately, the different limitations of each record provide an opportunity to test or calibrate the other, and new methodological developments leverage both records simultaneously. However, we must reckon with the distinct relationships between sampling and time in the fossil record and molecular phylogenies. These differences impact our recognition of baselines and the analytical incorporation of age estimate uncertainty., Paleobiology, 44 (4), ISSN:1938-5331, ISSN:0094-8373

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Recognizing the threat of additive risk Humans are accelerating the extinction rates of species in both terrestrial and marine environments. However, species extinctions have occurred across time for a variety of other reasons. Finnegan et al. looked at the extinction rates across marine genera (groups of species) over the past 23 million years to determine intrinsic extinction rates and what traits or regions correspond to the highest rates. Combining patterns of intrinsic extinction with regions of high anthropogenic threat revealed taxa and areas, particularly in the tropics, where the risk of extinction will be especially high. Science , this issue p. 567

Many processes can contribute to macroevolutionary change. This fact is the source of the wide variety of macroevolutionary change across time and taxa as well as the bane of pale-obiological research trying to understand how macroevolution works. Here, I present a general framework for understanding the variety of macroevolutionary phenomena. Based on Price’s theorem, this framework provides a simple quantitative means to understand (1) the macroevolutionary processes that are possible and (2) the way those processes interact with each other. The major qualitative features of macroevolution depend first on the number of processes that co-occur and then on the magnitudes and evolutionary directions of those processes. Species selection, the major macroevolutionary process, consists of patterns of differential rates of speciation and extinction. Its macroevolutionary efficacy depends on the presences of sufficient microevolutionary change. Conversely, microevolutionary change is limited in power by the independent evolution of species, and species selection acting across populations of species can amplify or suppress microevolution. Non-trends may result if species selection sufficiently neutralizes microevolution and may yield stable macroevolutionary patterns over many millions of years.

The degree to which organisms retain their environmental preferences is of utmost importance in predicting their fate in a world of rapid climate change. Notably, marine invertebrates frequently show strong affinities for either carbonate or terrigenous clastic environments. This affinity is due to characteristics of the sediments as well as correlated environmental factors. We assessed the conservatism of substrate affinities of marine invertebrates over geological timescales, and found that niche conservatism is prevalent in the oceans, and largely determined by the strength of initial habitat preference. There is substantial variation in niche conservatism among major clades with corals and sponges being among the most conservative. Time-series analysis suggests that niche conservatism is enhanced during times of elevated nutrient flux, whereas niche evolution tends to occur after mass extinctions. Niche evolution is not necessarily elevated in genera exhibiting higher turnover in species composition.

Differences in the relative diversification rates of species with variant traits are known as species selection. Species selection can produce a macroevolutionary change in the frequencies of traits by changing the relative number of species possessing each trait over time. But species selection is not the only process that can change the frequencies of traits, phyletic microevolution of traits within species and phylogenetic trait evolution among species, the tempo and mode of microevolution can also change trait frequencies. Species selection, phylogenetic, and phyletic processes can all contribute to large-scale trends, reinforcing or canceling each other out. Even more complex interactions among macroevolutionary processes are possible when multiple covarying traits are involved. Here I present a multilevel macroevolutionary framework that is useful for understanding how macroevolutionary processes interact. It is useful for empirical studies using fossils, molecular phylogenies, or both. I illustrate the framework with the macroevolution of coloniality and photosymbiosis in scleractinian corals using a time-calibrated molecular phylogeny. I find that standing phylogenetic variation in coloniality and photosymbiosis deflects the direction of macroevolution from the vector of species selection. Variation in these traits constrains species selection and results in a 200 million year macroevolutionary equilibrium.

The mere existence of speciation and extinction make macro-evolutionary processes possible. Speciation and extinction introduce discontinuities in the microevolutionary change within lineages by initiating, disrupting, and terminating the continuity of species lineages. Within a clade, speciation and extinction become potent means of macroevolution in and of themselves. This process, termed species selection, is a macroevolutionary analogue of natural selection, with species playing an analogous part akin to that played by organisms in microevolution. That said, it has proven difficult to think about levels of selection. The concept of species sorting was introduced to help our thinking on this issue by identifying two aspects inherent in hierarchical systems can confuse our attempts to understand them: uncertainty in the level that selection acts and uncertainty about if the pattern of selection is in fact caused at all. Thanks to insights from evolutionary transitions in individuality, we now know more about how to identify the level of selection and how to parse the causal structure in hierarchical evolutionary circumstances. We know that if the fitness of organisms causes the fitness of more inclusive species then they must covary. However, there is no evidence of such a covariance between fitnesses at these two levels. This covariance is just not observed; neither between cells and organisms nor between organisms and species. Rather, speciation and extinction rates appear to be completely divorced from organismal fitness. With this insight, the concept of species sorting shrinks so that it only covers the two processes of species selection and drift. I argue that we are better off focusing on understanding the processes of species selection and drift and that there is therefore no further need for the concept of species sorting.

The Last Interglacial (LIG; ca. 125,000 y ago) resulted from rapid global warming and reached global mean temperatures exceeding those of today. The LIG thus offers the opportunity to study how life may respond to future global warming. Using global occurrence databases and applying sampling-standardization, we compared reef coral diversity and distributions between the LIG and modern. Latitudinal diversity patterns are characterized by a tropical plateau today but were characterized by a pronounced equatorial trough during the LIG. This trough is governed by substantial range shifts away from the equator. Range shifts affected both leading and trailing edges of species range limits and were much more pronounced in the Northern Hemisphere than south of the equator. We argue that interglacial warming was responsible for the loss of equatorial diversity. Hemispheric differences in insolation during the LIG may explain the asymmetrical response. The equatorial retractions are surprisingly strong given that only small temperature changes have been reported in the LIG tropics. Our results suggest that the poleward range expansions of reef corals occurring with intensified global warming today may soon be followed by equatorial range retractions.

Understanding historical patterns of diversity dynamics is of paramount importance for many evolutionary questions. The fossil record has long been the only source of information on patterns of diversification, but the molecular record, derived from time-calibrated phylogenies, is becoming an important additional resource. Both fossil and molecular approaches have shortcomings and biases. These have been well studied for fossil data but much less so for molecular data and empirical comparisons between approaches are lacking. Here, we compare the patterns of diversification derived from fossil and molecular data in scleractinian reef coral species. We also assess the robustness of molecular diversification rates to poor taxon sampling. We find that the temporal pattern of molecular diversification rates is robust to incomplete sampling when rates are calculated per interval. The major obstacle of molecular methods is that rate estimates are distorted because diversification rates can never be negative, whereas the fossil record suffers from incomplete preservation and inconsistent taxonomy. Nevertheless, the molecular pattern of diversification is comparable to the pattern we observe in the fossil record, with the timing of major diversification pulses coinciding in each dataset. For example, both agree that the end-Triassic coral extinction was a catastrophic bottleneck in scleractinian evolution.

Anthropogenic rise in the carbon dioxide concentration in the atmosphere leads to global warming and acidification of the oceans. Ocean acidification (OA) is harmful to many organisms but especially to those that build massive skeletons of calcium carbonate, such as reef corals. Here, we test the recent suggestion that OA leads not only to declining calcification of reef corals and reduced growth rates of reefs but may also have been a trigger of ancient reef crises and mass extinctions in the sea. We analyse the fossil record of biogenic reefs and marine organisms to (1) assess the timing and intensity of ancient reef crises, (2) check which reef crises were concurrent with inferred pulses of carbon dioxide concentrations and (3) evaluate the correlation between reef crises and mass extinctions and their selectivity in terms of inferred physiological buffering. We conclude that four of five global metazoan reef crises in the last 500 Myr were probably at least partially governed by OA and rapid global warming. However, only two of the big five mass extinctions show geological evidence of OA.

All evolution attributable to natural selection, at any level, is due to a causal covariance between fitness and phenotype. Over macroevolutionary time scales, species selection is one of many possible mechanisms for generating large-scale morphological trends. For species selection to sort morphology, a correlation between morphology and taxonomic diversification rate must be present. Other trend mechanisms (driven mechanisms, e.g., a bias in the direction of speciation) produce a systematic change in the mean phenotype over time. All mechanisms can co-occur. Here I demonstrate (1) an inverse correlation between diversification rate and calyx complexity that demonstrates the effect of species selection on morphology. Genera with simple calyces tend to increase in diversity, whereas genera with complex calyces have a net decrease in diversity; and (2) the presence of a driven trend mechanism in monobathrid crinoids where descendant genera tend to be simpler than their ancestors. The separate effects of these two classes of trend mechanisms can be combined by using the Price's Theorem, which partitions the contribution to the overall change in calyx complexity over time accurately among selection and driven mechanisms. Price's Theorem provides significant conceptual and methodological clarification of the contribution of multiple and interacting hierarchical mechanisms in generating large-scale trends.

Abundance is one of the primary factors believed to influence extinction yet little is known about its relationship to extinction rates over geologic time. Using data from the Paleobiology Database we show that abundance was an important factor in the extinction dynamics of marine bivalve genera over the post-Paleozoic. Contrary to expectations, our analyses reveal a nonlinear relationship between abundance and extinction rates, with rare and abundant genera exhibiting rates elevated over those of genera of moderate abundance. This U-shaped pattern is a persistent feature of the post-Paleozoic history of marine bivalves and provides one possible explanation for why we find strong support for heterogeneous extinction rates among genera grouped by similarity in abundance yet effectively no net relationship among these rates when using models of directional selection on abundance.

The German Pentecostal Movement began in 1907 but too few people are aware of its history or origins. In Confidence, published 1908 - 1926, A. A. Boddy preserved many vital insights into the genesis of the German Pentecostal Movement. Some articles were reproduced in the German magazine Pfingstgruse, 1909 - 1919, originally edited by Jonathan Paul who became the prominent leader of Pentecost in Germany. Both publications were established to promote Pentecostalism and provide invaluable primary source material in the form of editorials, teaching, sermons, stories and testimonies, mostly long forgotten, recording exciting days, reminiscent of the Early Church. Germany provided European Pentecostalism with some key leaders, preachers and teachers, principally Jonathan Paul, but also Emil Meyer, and Emil Humburg and Carl Octavius Voget. The first seven years were marked by influential conferences, a major attack against the Pentecostals in the form of the Berlin Declaration, and the formation of the M...

Marine taxa are threatened by anthropogenic impacts, but knowledge of their extinction vulnerabilities is limited. The fossil record provides rich information on past extinctions that can help predict biotic responses. We show that over 23 million years, taxonomic membership and geographic range size consistently explain a large proportion of extinction risk variation in six major taxonomic groups. We assess intrinsic risk-extinction risk predicted by paleontologically calibrated models-for modern genera in these groups. Mapping the geographic distribution of these genera identifies coastal biogeographic provinces where fauna with high intrinsic risk are strongly affected by human activity or climate change. Such regions are disproportionately in the tropics, raising the possibility that these ecosystems may be particularly vulnerable to future extinctions. Intrinsic risk provides a prehuman baseline for considering current threats to marine biodiversity.

The concept of a worldview is often loosely understood but is clearly defined by Jon Newton as a ‘plausibility structure’. He argues that considerable conflict exists in current Christian worldview...

Perhaps the most pressing issue in predicting biotic responses to present and future global change is understanding how environmental factors shape the relationship between ecological traits and extinction risk. The fossil record provides millions of years of insight into how extinction selectivity (i.e., differential extinction risk) is shaped by interactions between ecological traits and environmental conditions. Numerous paleontological studies have examined trait-based extinction selectivity; however, the extent to which these patterns are shaped by environmental conditions is poorly understood due to a lack of quantitative synthesis across studies. We conducted a meta-analysis of published studies on fossil marine bivalves and gastropods that span 458 million years to uncover how global environmental and geochemical changes covary with trait-based extinction selectivity. We focused on geographic range size and life habit (i.e., infaunal vs. epifaunal), two of the most important and commonly examined predictors of extinction selectivity. We used geochemical proxies related to global climate, as well as indicators of ocean acidification, to infer average global environmental conditions. Life-habit selectivity is weakly dependent on environmental conditions, with infaunal species relatively buffered from extinction during warmer climate states. In contrast, the odds of taxa with broad geographic ranges surviving an extinction (>2500 km for genera, >500 km for species) are on average three times greater than narrow-ranging taxa (estimate of odds ratio: 2.8, 95% confidence interval = 2.3–3.5), regardless of the prevailing global environmental conditions. The environmental independence of geographic range size extinction selectivity emphasizes the critical role of geographic range size in setting conservation priorities.

Expanding on the work of Ulrich Beck and other social theorists, the central thesis of this article is that individuals in contemporary North American society are increasingly motivated by the need to alleviate expanding levels of perceived risks associated with interpersonal love relationships and mate selection. In response to these perceived risks, men and women today are altering their relationship patterns in such a way that the process of relationship formation and assessment has become increasingly rationalized. As a result, a paradox has been created between the rational management of interpersonal risk associated with romance and the production of risk. This article is primarily a theoretical treatment of the issues, augmented with data on the social history of adolescence, courtship, and marriage and a review of the literature on mate selection processes in contemporary society.

Rarity is widely used to predict the vulnerability of species to extinction. Species can be rare in markedly different ways, but the relative impacts of these different forms of rarity on extinction risk are poorly known and cannot be determined through observations of species that are not yet extinct. The fossil record provides a valuable archive with which we can directly determine which aspects of rarity lead to the greatest risk. Previous palaeontological analyses confirm that rarity is associated with extinction risk, but the relative contributions of different types of rarity to extinction risk remain unknown because their impacts have never been examined simultaneously. Here, we analyse a global database of fossil marine animals spanning the past 500 million years, examining differential extinction with respect to multiple rarity types within each geological stage. We observe systematic differences in extinction risk over time among marine genera classified according to their rarity. Geographic range played a primary role in determining extinction, and habitat breadth a secondary role, whereas local abundance had little effect. These results suggest that current reductions in geographic range size will lead to pronounced increases in long-term extinction risk even if local populations are relatively large at present.

Introduction Everything biological varies. Without variation, evolution would not be possible. This is a truism in macroevolution as much as it is within and between organisms. Species vary in their phenotypic and macroecological traits (Brown 1995) and variation also exists in the taxonomic rates of speciation and extinction over time (Alroy 2008), among taxa (Van Valen 1973; Sepkoski 1981; Raup and Boyajian 1988), and within taxa (Van Valen 1973, 1975; Liow et al . 2008; McPeek 2008; Simpson and Harnik 2009; Simpson 2010). Variation in diversification rates produces the major patterns of diversification we observe in the fossil record. Understanding the patterns and causes of variation in diversification rates has been the focus of palaeobiology for decades (Simpson 1944, 1953; Van Valen 1973; Raup 1978; Gould and Calloway 1980; Sepkoski 1981; Raup 1991a, 1991b). Palaeobiologists, however, are not the only ones interested in understanding the patterns and causes of diversification. Diversification is also interesting to ecologists for at least two reasons. Major spatial patterns of diversity such as the latitudinal diversity gradient are likely to be underpinned by historical patterns of speciation and extinction (Jablonski and Hunt 2006; Krug et al . 2007, 2008; Kiessling et al . 2010). Also, many distributions of ecologically important traits, for example body size, may be, in part, a product of the historical patterns of differential diversification (Stanley 1975; Van Valen 1975). The second interest is the issue of diversity limitation. Data from the fossil record and molecular phylogenetics of extant organisms have been brought in to study this issue and evidence is accumulating that diversity is, in fact, constrained (Cracraft 1982; Nee et al . 1992b; Paradis 1997; Pybus and Harvey 2000; Nee 2001; Ricklefs 2007; Alroy 2008, 2009, 2010; Alroy et al . 2008; McPeek 2008; Phillimore and Price 2008; Rabosky and Lovette 2008a, 2009b; Phillimore and Price 2009; Quental and Marshall 2009, 2010; Rabosky 2009b).

In the coming century, life in the ocean will be confronted with a suite of environmental conditions that have no analog in human history. Thus, there is an urgent need to determine which marine species will adapt and which will go extinct. Here, we review the growing literature on marine extinctions and extinction risk in the fossil, historical, and modern records to compare the patterns, drivers, and biological correlates of marine extinctions at different times in the past. Characterized by markedly different environmental states, some past periods share common features with predicted future scenarios. We highlight how the different records can be integrated to better understand and predict the impact of current and projected future environmental changes on extinction risk in the ocean.

Understanding historical patterns of diversity dynamics is of paramount importance for many evolutionary questions. The fossil record has long been the only source of information on patterns of diversification, but the molecular record, derived from time-calibrated phylogenies, is becoming an important additional resource. Both fossil and molecular approaches have shortcomings and biases. These have been well studied for fossil data but much less so for molecular data and empirical comparisons between approaches are lacking. Here, we compare the patterns of diversification derived from fossil and molecular data in scleractinian reef coral species. We also assess the robustness of molecular diversification rates to poor taxon sampling. We find that the temporal pattern of molecular diversification rates is robust to incomplete sampling when rates are calculated per interval. The major obstacle of molecular methods is that rate estimates are distorted because diversification rates can never be negative, whereas the fossil record suffers from incomplete preservation and inconsistent taxonomy. Nevertheless, the molecular pattern of diversification is comparable to the pattern we observe in the fossil record, with the timing of major diversification pulses coinciding in each dataset. For example, both agree that the end-Triassic coral extinction was a catastrophic bottleneck in scleractinian evolution.

Functional specialization, or division of labour (DOL), of parts within organisms and colonies is common in most multi-cellular, colonial and social organisms, but it is far from ubiquitous. Several mechanisms have been proposed to explain the evolutionary origins of DOL; the basic feature common to all of them is that functional differences can arise easily. These mechanisms cannot explain the many groups of colonial and social animals that exhibit no DOL despite up to 500 million years of evolution. Here, I propose a new hypothesis, based on a multi-level selection theory, which predicts that a reproductive DOL is required to evolve prior to subsequent functional specialization. I test this hypothesis using a dataset consisting of the type of DOL for living and extinct colonial and social animals. The frequency distribution of DOL and the sequence of its acquisition confirm that reproductive specialization evolves prior to functional specialization. A corollary of this hypothesis is observed in colonial, social and also within multi-cellular organisms; those species without a reproductive DOL have a smaller range of internal variation, in terms of the number of polymorphs or cell types, than species with a reproductive DOL.