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1. CONFLICTING BODY-SIZE TRENDS ACROSS THE PLIO–PLEISTOCENE MOLLUSCAN TURNOVER EVENT IN THE WESTERN ATLANTIC DESPITE SUBSEQUENT NUTRIENT LIMITATION

   https://doi.org/10.1130/abs/2023AM-391080  

   Anderson, Brendan; Behn, Jessica R.; Betz, Amy; Petsios, Elizabeth; Allmon, Warren D.; Lieberman, Bruce; Hendricks, Jonathan (August 2023, Geological Society of America Abstracts with Programs)

   Preliminary data indicate between the latest Pliocene and recent approximately 85% of bivalves and 90% of gastropod species in Florida and the Atlantic Coastal Plain became extinct, with high levels of origination resulting in similar total species richness in the region today. We expected this event may have impacted molluscan body size as body size in mollusks is generally correlated with nutrient availability and primary productivity, which decreased following the Pliocene closure of the Central American Seaway. Previous work indicated small body size is associated with extinction survival during this event in both bivalves and gastropods. Where all extant and Pliocene members of surviving bivalve clades have been compared, these have also declined in size; comparable studies of all extant and Pliocene members of gastropod clades have not yet, however, been undertaken. We investigated 3 families of gastropods of differing ecology with both high turnover and at least one boundary-crossing lineage in order to assess the impact of the turnover event on each clade’s body size. These were the predatory Conidae, the herbivorous Tegulidae, and the suspension-feeding Turritellidae. These had approximately 65%, 75%, and 90% extinction, respectively, with modern­ diversity at 110%, 100%, and 10% of their respective Pliocene species richness in the region. Despite high levels of turnover, we found no general pattern of body-size change associated with the event either within clades or among boundary-crossing lineages. While many of the largest species of Conidae and Turritellidae did become extinct, this was balanced by the loss of smaller-bodied species, while the Tegulidae increased in size. Among ancestor-descendant pairs, 1 turritellid decreased in size while 1 remained unchanged, 4 Conidae decreased in size while 2 increased in size, and 1 tegulid increased in size. These data suggest that for gastropods there were complex interactions between ecology, extinction, origination, and body-size evolution associated with this event and that a more phylogenetically-diverse dataset is needed to determine whether generalizable patterns exist which may be used to predict responses to future environmental change. 

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2. Phanerozoic parasitism and marine metazoan diversity: Dilution versus amplification

   https://doi.org/10.1098/rstb.2020.0366  

   De Baets, Kenneth; Huntley, John Warren; Scarponi, Daniele; Klompmaker, Adiël A.; Skawina, Aleksandra (January 2021, Philosophical transactions)

   Growing evidence suggests that biodiversity mediates parasite prevalence. We have compiled the first global database on occurrences and prevalence of marine parasitism throughout the Phanerozoic and assess the relationship with biodiversity to test if there is support for amplification or dilution of parasitism at the macroevolutionary scale. Median prevalence values by era are 5% for the Paleozoic, 4% for the Mesozoic, and a significant increase to 10% for the Cenozoic. We calculated period-level shareholder quorum sub-sampled (SQS) estimates of mean sampled diversity, three-timer (3T) origination rates, and 3T extinction rates for the most abundant host clades in the Paleobiology Database to compare to both occurrences of parasitism and the more informative parasite prevalence values. Generalized linear models (GLMs) of parasite occurrences and SQS diversity measures support both the amplification (all taxa pooled, crinoids and blastoids, and molluscs) and dilution hypotheses (arthropods, cnidarians, and bivalves). GLMs of prevalence and SQS diversity measures support the amplification hypothesis (all taxa pooled and molluscs). Though likely scale-dependent, parasitism has increased through the Phanerozoic and clear patterns primarily support the amplification of parasitism with biodiversity in the history of life. This article is part of the theme issue ‘Infectious disease macroecology: parasite diversity and dynamics across the globe’. 

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3. Convergence and contingency in the evolution of a specialized mode of life: multiple origins and high disparity of rock-boring bivalves

   https://doi.org/10.1098/rspb.2022.1907  

   Collins, Katie S.; Edie, Stewart M.; Jablonski, David (February 2023, Proceedings of the Royal Society B: Biological Sciences)

   Evolutionary adaptation to novel, specialized modes of life is often associated with a close mapping of form to the new function, resulting in narrow morphological disparity. For bivalve molluscs, endolithy (rock-boring) has biomechanical requirements thought to diverge strongly from those of ancestral functions. However, endolithy in bivalves has originated at least eight times. Three-dimensional morphometric data representing 75 species from approximately 94% of extant endolithic genera and families, along with 310 non-endolithic species in those families, show that endolithy is evolutionarily accessible from many different morphological starting points. Although some endoliths appear to converge on certain shell morphologies, the range of endolith shell form is as broad as that belonging to any other bivalve substrate use. Nevertheless, endolithy is a taxon-poor function in Bivalvia today. This limited richness does not derive from origination within source clades having significantly low origination or high extinction rates, and today's endoliths are not confined to low-diversity biogeographic regions. Instead, endolithy may be limited by habitat availability. Both determinism (as reflected by convergence among distantly related taxa) and contingency (as reflected by the endoliths that remain close to the disparate morphologies of their source clades) underlie the occupation of endolith morphospace. 

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4. Approaches to macroevolution: 2. Sorting of variation, some overarching issues, and general conclusions.

   Jablonski, D. (July 2017, Evolutionary biology)

   Abstract Approaches to macroevolution require integration of its two fundamental components, within a hierarchical framework. Following a companion paper on the origin of variation, I here discuss sorting within an evolutionary hierarchy. Species sorting—sometimes termed species selection in the broad sense, meaning differential origination and extinction owing to intrinsic biological properties—can be split into strict-sense species selection, in which rate differentials are governed by emergent, species-level traits such as geographic range size, and effect macroevolution, in which rates are governed by organism-level traits such as body size; both processes can create hitchhiking effects, indirectly causing the proliferation or decline of other traits. Several methods can operationalize the concept of emergence, so that rigorous separation of these processes is increasingly feasible. A macroevolutionary tradeoff, underlain by the intrinsic traits that influence evolutionary dynamics, causes speciation and extinction rates to covary in many clades, resulting in evolutionary volatility of some clades and more subdued behavior of others; the few clades that break the tradeoff can achieve especially prolific diversification. In addition to intrinsic biological traits at multiple levels, extrinsic events can drive the waxing and waning of clades, and the interaction of traits and events are difficult but important to disentangle. Evolutionary trends can arise in many ways, and at any hierarchical level; descriptive models can be fitted to clade trajectories in phenotypic or functional spaces, but they may not be diagnostic regarding processes, and close attention must be paid to both leading and trailingedges of apparent trends. Biotic interactions can have negative or positive effects on taxonomic diversity within a clade, but cannot be readily extrapolated from the nature of such interactions at the organismic level. The relationships among macroevolutionary currencies through time (taxonomic richness, morphologic disparity, functional variety) are crucial for understanding the nature of evolutionary diversification. A novel approach to diversity-disparity analysis shows that taxonomic diversifications can lag behind, occur in concert with, or precede, increases in disparity. Some overarching issues relating to both the origin and sorting of clades and phenotypes include the macroevolutionary role of mass extinctions, the potential differences between plant and animal macroevolution, whether macroevolutionary processes have changed through geologic time, and the growing human impact on present-day macroevolution. Many challenges remain, but progress is being made on two of the key ones: (a) the integration of variation-generating mechanisms and the multilevel sorting processes that act on that variation, and (b) the integration of paleontological and neontological approaches to historical biology. 

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5. CONNECTING EARLY PALEOZOIC ECHINODERM DIVERSITY DYNAMICS TO SHIFTING CLIMATE PATTERNS

   https://doi.org/10.1130/abs/2023AM-393219  

   Harris, Ohav; Sheffield, Sarah; Lam, Adriane R.; Bauer, Jennifer E.; Deline, Bradley; Lamsdell, James C. (October 2023, Geological Society of America Abstracts with Programs)

   The Paleozoic Era was host to many significant biotic events such as the Great Ordovician Biodiversification Event, the Late Ordovician Mass Extinction, and the Late Devonian extinctions. These events were likely catalyzed by abiotic (e.g. climate) versus biotic drivers. Echinoderms are globally distributed, temporally expansive, and easily identifiable; these qualities make them an excellent model system to test hypotheses relating biodiversity with abiotic factors. Biodiversity patterns of echinoderms are currently not well understood because of a lack of focus on the dynamics of the entire clade. To remedy this, we have worked to expand current understandings of Paleozoic echinoderm diversity patterns by investigating the global distribution and temporal occurrences of taxa spanning the entire clade. Results suggest patterns of diversity unique to previously established trends that predominantly centered on a limited number of echinoderm groups. To examine the connection between climate change and Paleozoic echinoderm biodiversity (i.e., diversification, extinction, and origination rates), we collated stable oxygen isotope data from the primary literature spanning the Ordovician to the Devonian. We compiled these data to create a continuous curve of δO values during the described period to better evaluate in tandem with echinoderm diversity metrics. When the δO curve is compared to the echinoderm biodiversity patterns, we found that cooling periods coincide with increased extinction rates, corroborating prior hypotheses that major end-Ordovician cooling triggered changes in echinoderm biodiversity at a global level and further identifying a potential pattern in abiotic drivers in echinoderm biodiversity. The connection between Paleozoic echinoderm biodiversity and other abiotic factors will be further studied by comparing these recovered patterns with paleolatitudinal distributions. 

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