What are patterns of rise and decline?

The notions of change, such as birth, death, growth, evolution and longevity, extend across reality, including biological, cultural and societal phenomena. Patterns of change describe how success and composition of every entity, from species to societies, vary across time. Languages develop into new languages, music and fashion continuously evolve, economies rise and decline, ecological and societal crises come and go. A common way to perceive and analyse change processes is through patterns of rise and decline, the ubiquitous, often distinctively unimodal trajectories describing life histories of various entities. These patterns come in different shapes and are measured according to varying definitions. Depending on how they are measured, patterns of rise and decline can reveal, emphasize, mask or obscure important dynamics in natural and cultural phenomena. Importantly, the variations of how dynamics are measured can be vast, making it impossible to directly compare patterns of rise and decline across fields of science. Standardized analysis of these patterns has the potential to uncover important but overlooked commonalities across natural phenomena and potentially help us catch the onset of dramatic shifts in entities' state, from catastrophic crashes in success to gradual emergence of new entities. We provide a framework for standardized recognizing, characterizing and comparing patterns of change by combining understanding of dynamics across fields of science. Our toolkit aims at enhancing understanding of the most general tendencies of change, through two complementary perspectives: dynamics of emergence and dynamics of success. We gather comparable cases and data from different research fields and summarize open research questions that can help us understand the universal principles, perception-biases and field-specific tendencies in patterns of rise and decline of entities in nature.

Early cephalopod evolution clarified through Bayesian phylogenetic inference.

BACKGROUND: Despite the excellent fossil record of cephalopods, their early evolution is poorly understood. Different, partly incompatible phylogenetic hypotheses have been proposed in the past, which reflected individual author's opinions on the importance of certain characters but were not based on thorough cladistic analyses. At the same time, methods of phylogenetic inference have undergone substantial improvements. For fossil datasets, which typically only include morphological data, Bayesian inference and in particular the introduction of the fossilized birth-death model have opened new possibilities. Nevertheless, many tree topologies recovered from these new methods reflect large uncertainties, which have led to discussions on how to best summarize the information contained in the posterior set of trees. RESULTS: We present a large, newly compiled morphological character matrix of Cambrian and Ordovician cephalopods to conduct a comprehensive phylogenetic analysis and resolve existing controversies. Our results recover three major monophyletic groups, which correspond to the previously recognized Endoceratoidea, Multiceratoidea, and Orthoceratoidea, though comprising slightly different taxa. In addition, many Cambrian and Early Ordovician representatives of the Ellesmerocerida and Plectronocerida were recovered near the root. The Ellesmerocerida is para- and polyphyletic, with some of its members recovered among the Multiceratoidea and early Endoceratoidea. These relationships are robust against modifications of the dataset. While our trees initially seem to reflect large uncertainties, these are mainly a consequence of the way clade support is measured. We show that clade posterior probabilities and tree similarity metrics often underestimate congruence between trees, especially if wildcard taxa are involved. CONCLUSIONS: Our results provide important insights into the earliest evolution of cephalopods and clarify evolutionary pathways. We provide a classification scheme that is based on a robust phylogenetic analysis. Moreover, we provide some general insights on the application of Bayesian phylogenetic inference on morphological datasets. We support earlier findings that quartet similarity metrics should be preferred over the Robinson-Foulds distance when higher-level phylogenetic relationships are of interest and propose that using a posteriori pruned maximum clade credibility trees help in assessing support for phylogenetic relationships among a set of relevant taxa, because they provide clade support values that better reflect the phylogenetic signal.

On the enigma of Palaenigma wrangeli (Schmidt), a conulariid with a partly non-mineralized skeleton.

Palaenigma wrangeli (Schmidt) is a finger-sized fossil with a tetraradiate conical skeleton; it occurs as a rare component in fossiliferous Upper Ordovician strata of the eastern Baltic Basin and is known exclusively from north Estonia. The systematic affinities and palaeoecology of P. wrangeli remained questionable. Here, the available specimens of P. wrangeli have been reexamined using scanning electron microscopy and x-ray computed tomography (microCT). Additionally, the elemental composition of the skeletal elements has been checked using energy dispersive X-ray spectroscopy. The resulting 2D-, and 3D-scans reveal that P. wrangeli consists of an alternation of distinct calcium phosphate (apatite) lamellae and originally organic-rich inter-layers. The lamellae form four semicircular marginal pillars, which are connected by irregularly spaced transverse diaphragms. Marginally, the diaphragms and pillar lamellae are not connected to each other and thus do not form a closed periderm structure. A non-mineralized or poorly mineralized external periderm existed originally in P. wrangeli but is only rarely and fragmentary preserved. P. wrangeli often co-occurs with conulariids in fossil-rich limestone with mudstone-wackestone lithologies. Based on the new data, P. wrangeli can be best interpreted as a poorly mineralized conulariinid from an original soft bottom habitat. Here the new conulariinid family Palaenigmaidae fam. nov. is proposed as the monotypic taxon for P. wrangeli.

Skeletal marine animal biodiversity is built by families with long macroevolutionary lag times.

The clade dynamics of marine animals have changed markedly over the Phanerozoic. Long-term diversification is associated with decreasing origination and extinction rates, and with increasing taxon longevity. Here we use the diversification trajectories of skeletal non-colonial marine families to infer the mechanisms that generated these trends. Suggested mechanisms behind these trends include stochastic extinction of taxa with high evolutionary volatility and selection for traits that buffer against extinction. We find an increasing predominance of Phanerozoic families with long lag times between first appearance and peak diversity, over those with 'early burst' diversification trajectories. Long-lag families persisted for longer and had lower evolutionary volatilities, higher genus-level occupancies and genera with larger niche breadths than early burst families. However, they do not preferentially show ecological modes known to protect against extinction. We interpret the rise of the long-lag families as reflecting an intensification of ecosystem-level mechanisms supporting both long-term coexistence and transient dynamics, which increased the capacity of marine ecosystems to accommodate highly diverse communities.

Impacts of spatial and environmental differentiation on early Palaeozoic marine biodiversity.

The unprecedented diversifications in the fossil record of the early Palaeozoic (541-419 million years ago) increased both within-sample (α) and global (γ) diversity, generating considerable ecological complexity. Faunal difference (ß diversity), including spatial heterogeneity, is thought to have played a major role in early Palaeozoic marine diversification, although α diversity is the major determinant of γ diversity through the Phanerozoic. Drivers for this Phanerozoic shift from ß to α diversity are not yet resolved. Here, we evaluate the impacts of environmental and faunal heterogeneity on diversity patterns using a global spatial grid. We present early Palaeozoic genus-level α, ß and γ diversity curves for molluscs, brachiopods, trilobites and echinoderms and compare them with measures of spatial lithological heterogeneity, which is our proxy for environmental heterogeneity. We find that α and ß diversity are associated with increased lithological heterogeneity, and that ß diversity declines over time while α increases. We suggest that the enhanced dispersal of marine taxa from the Middle Ordovician onwards facilitated increases in α diversity by encouraging the occupation of narrow niches and increasing the prevalence of transient species, simultaneously reducing spatial ß diversity. This may have contributed to a shift from ß to α diversity as the major determinant of γ diversity increase over this critical evolutionary interval.

The evolutionary dynamics of the early Palaeozoic marine biodiversity accumulation.

The early Palaeozoic Era records the initial biodiversification of the Phanerozoic. The increase in biodiversity involved drastic changes in taxon longevity, and in rates of origination and extinction. Here, we calculate these variables in unprecedented temporal resolution. We find that highly volatile origination and extinction rates are associated with short genus longevities during the Cambrian Period. During the Ordovician and Silurian periods, evolutionary rates were less volatile and genera persisted for increasingly longer intervals. The 90%-genus life expectancy doubled from 5 Myr in the late Cambrian to more than 10 Myr in the Ordovician-Silurian periods. Intervals with widespread ecosystem disruption are associated with short genus longevities during the Cambrian and with exceptionally high longevities during the Ordovician and Silurian periods. The post-Cambrian increase in persistence of genera, therefore, indicates an elevated ability of the changing early Palaeozoic marine ecosystems to sustainably maintain existing genera. This is evidence of a new level of ecosystem resilience which evolved during the Ordovician Period.

Cascading trend of Early Paleozoic marine radiations paused by Late Ordovician extinctions.

The greatest relative changes in marine biodiversity accumulation occurred during the Early Paleozoic. The precision of temporal constraints on these changes is crude, hampering our understanding of their timing, duration, and links to causal mechanisms. We match fossil occurrence data to their lithostratigraphical ranges in the Paleobiology Database and correlate this inferred taxon range to a constructed set of biostratigraphically defined high-resolution time slices. In addition, we apply capture-recapture modeling approaches to calculate a biodiversity curve that also considers taphonomy and sampling biases with four times better resolution of previous estimates. Our method reveals a stepwise biodiversity increase with distinct Cambrian and Ordovician radiation events that are clearly separated by a 50-million-year-long period of slow biodiversity accumulation. The Ordovician Radiation is confined to a 15-million-year phase after which the Late Ordovician extinctions lowered generic richness and further delayed a biodiversity rebound by at least 35 million years. Based on a first-differences approach on potential abiotic drivers controlling richness, we find an overall correlation with oxygen levels, with temperature also exhibiting a coordinated trend once equatorial sea surface temperatures fell to present-day levels during the Middle Ordovician Darriwilian Age. Contrary to the traditional view of the Late Ordovician extinctions, our study suggests a protracted crisis interval linked to intense volcanism during the middle Late Ordovician Katian Age. As richness levels did not return to prior levels during the Silurian-a time of continental amalgamation-we further argue that plate tectonics exerted an overarching control on biodiversity accumulation.

Cephalopod origin and evolution: A congruent picture emerging from fossils, development and molecules: Extant cephalopods are younger than previously realised and were under major selection to become agile, shell-less predators.

Cephalopods are extraordinary molluscs equipped with vertebrate-like intelligence and a unique buoyancy system for locomotion. A growing body of evidence from the fossil record, embryology and Bayesian molecular divergence estimations provides a comprehensive picture of their origins and evolution. Cephalopods evolved during the Cambrian (∼530 Ma) from a monoplacophoran-like mollusc in which the conical, external shell was modified into a chambered buoyancy apparatus. During the mid-Palaeozoic (∼416 Ma) cephalopods diverged into nautiloids and the presently dominant coleoids. Coleoids (i.e. squids, cuttlefish and octopods) internalised their shells and, in the late Palaeozoic (∼276 Ma), diverged into Vampyropoda and the Decabrachia. This shell internalisation appears to be a unique evolutionary event. In contrast, the loss of a mineralised shell has occurred several times in distinct coleoid lineages. The general tendency of shell reduction reflects a trend towards active modes of life and much more complex behaviour.

[On natural history museums and their purpose. A lecture given by Leopold von Buch (1774-1853) in April 1838]. / Uber Museen der Naturgeschichte und ihren Zweck. Ein Vortrag gehalten von Leopold von Buch (1774-1853) im April 1838.

A manuscript of a lecture by the Prussian geologist Leopold von Buch given at the Berlin Society of the Friends of the Humanity was discovered at the Museum für Naturkunde, Berlin. The text is a raw version of a passionate plea for the formation of natural history collections as science places, with a partly biting humor. Based on until now unknown anecdotes about naturalists like Kaspar Maria Graf Sternberg (1761-1838) and Friedrich Wilhelm Hoeninghaus (1771-1854) Leopold von Buch argues with von Sternberg for the scientific value of natural history collections. The repeating references to the works of Goethe and an extensive addendum of various Dante translations into German are striking. The lecture manuscript complements our knowledge about the thinking of this important geologist, and provides new insights into the science policy of his time.

The origin and initial rise of pelagic cephalopods in the Ordovician.

BACKGROUND: During the Ordovician the global diversity increased dramatically at family, genus and species levels. Partially the diversification is explained by an increased nutrient, and phytoplankton availability in the open water. Cephalopods are among the top predators of today's open oceans. Their Ordovician occurrences, diversity evolution and abundance pattern potentially provides information on the evolution of the pelagic food chain. METHODOLOGY/PRINCIPAL FINDINGS: We reconstructed the cephalopod departure from originally exclusively neritic habitats into the pelagic zone by the compilation of occurrence data in offshore paleoenvironments from the Paleobiology Database, and from own data, by evidence of the functional morphology, and the taphonomy of selected cephalopod faunas. The occurrence data show, that cephalopod associations in offshore depositional settings and black shales are characterized by a specific composition, often dominated by orthocerids and lituitids. The siphuncle and conch form of these cephalopods indicate a dominant lifestyle as pelagic, vertical migrants. The frequency distribution of conch sizes and the pattern of epibionts indicate an autochthonous origin of the majority of orthocerid and lituitid shells. The consistent concentration of these cephalopods in deep subtidal sediments, starting from the middle Tremadocian indicates the occupation of the pelagic zone early in the Early Ordovician and a subsequent diversification which peaked during the Darriwilian. CONCLUSIONS/SIGNIFICANCE: The exploitation of the pelagic realm started synchronously in several independent invertebrate clades during the latest Cambrian to Middle Ordovician. The initial rise and diversification of pelagic cephalopods during the Early and Middle Ordovician indicates the establishment of a pelagic food chain sustainable enough for the development of a diverse fauna of large predators. The earliest pelagic cephalopods were slowly swimming vertical migrants. The appearance and early diversification of pelagic cephalopods is interpreted as a consequence of the increased food availability in the open water since the latest Cambrian.