Carbonate collapse and the late Paleozoic ice age marine biodiversity crisis

The late Paleozoic ice age (LPIA) was characterized by persistently low diversity of marine invertebrates following a second-order mass extinction. Here, we used a data set of North American (paleotropical) fossil occurrences of brachiopod, bivalve, and coral genera from the Paleobiology Database, combined with lithologic data from Macrostrat, to demonstrate that low diversity was caused by the collapse of carbonate environments during the LPIA. After dividing the data by lithology, low diversity was evident only in carbonate environments, whereas diversity within siliciclastic environments actually increased during the LPIA, after a brief decline in the Serpukhovian (late Mississippian). Diversity patterns closely matched respective changes in the volume of carbonate and siliciclastic rocks. The contrasting patterns observed in the two environments suggest that habitat loss was a direct cause of changes in diversity, because other factors, such as temperature, would have affected genera in both environments. A causal relationship is also supported by the finding that diversity remained high in carbonate refugia (carbonate beds within majority-siliciclastic formations) until the Bashkirian, postdating the onset of icehouse conditions by ∼8 m.y. Our results provide a unifying, mechanistic explanation for the distinctive characteristics of the biotic impact, including its disproportionate effect on the tropical marine invertebrate fauna, prolonged recovery from extinction, low macroevolutionary rates during the recovery interval, and regional differences in its expression.Fil: Balseiro, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Powell, Matthew G.. Juniata College; Estados Unido

Unveiling the consequences of environmental variation and species abundances on beach taphofacies in Bahamas: The role of cementation and exhumation

Although environmental variability generates differences in the preservation of shell assemblages, intrinsic variations in shell characteristics can confound the effects of environment on preservation. However, several studies proposed that the composition of shell supply only affects the intensity of alteration but not its preservation trend along the environmental gradient and that environmental variability represents a major driver of taphofacies preservation. Here, we examine whether taphonomic differences among four infaunal and aragonitic bivalve species differing in shell thickness affect the definition of beach taphofacies in tropical carbonate environments on San Salvador Island (Bahamas). We show that (1) taphofacies can be discriminated with respect to (a) wave and storm activity as a function of exposure to Trade Winds, and (b) sandy beaches versus beaches with a mixture of sands and beach rock (representing a source of exhumed and cemented shells), and (2) species-specific bivalve assemblages show similar gradients in preservation, documenting that differences in preservation between species have minor effects on taphonomic discrimination of beach environments. Environments with a mixture of sands and beach rock are characterized by higher frequency of external cementation and abrasion than sandy beaches. Shells from low-energy beaches are more fragmented and discolored than shells from high-energy beaches. Previous studies showed that shells from San Salvador sandy beaches are more time-averaged than shells from rocky beaches. Differences in preservation between these two environments indicate two pathways: (1) assemblages on sandy beaches are degraded at higher rate but are enriched by old exhumed and lithified shells, and (2) assemblages on rocky beaches are cemented at higher rate. Old and lithified shells on sandy beaches are probably derived from submerged or exposed beach rock patches, leading to the mixture of young, well-preserved shells with old, poorly preserved shells. Shells on sandy beaches thus experience a complex history of burial and exhumation before their final deposition. Therefore, shell assemblages in lower energy carbonate environments from San Salvador Island are highly time-averaged, with the presence of old, poorly preserved shells. The depositional environment is thus the dominant factor controlling the structure of San Salvador beach taphofacies.Fil: Bayer, María Sol. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Balseiro, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Muñoz, Diego Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Gordillo, Sandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentin

Factors shaping community assemblages and species co-occurrence of different trophic levels

Species assemblages are the results of various processes, including dispersion and habitat filtering. Disentangling the effects of these different processes is challenging for statistical analysis, especially when biotic interactions should be considered. In this study, we used plants (producers) and leafhoppers (phytophagous) as model organisms, and we investigated the relative importance of abiotic versus biotic factors that shape community assemblages, and we infer on their biotic interactions by applying three-step statistical analysis. We applied a novel statistical analysis, that is, multiblock Redundancy Analysis (mbRA, step 1) and showed that 51.8% and 54.1% of the overall variation in plant and leafhopper assemblages are, respectively, explained by the two multiblock models. The most important blocks of variables to explain the variations in plant and leafhopper assemblages were local topography and biotic factors. Variation partitioning analysis (step 2) showed that pure abiotic filtering and pure biotic processes were relatively less important than their combinations, suggesting that biotic relationships are strongly structured by abiotic conditions. Pairwise co-occurrence analysis (step 3) on generalist leafhoppers and the most common plants identified 40 segregated species pairs (mainly between plant species) and 16 aggregated pairs (mainly between leafhopper species). Pairwise analysis on specialist leafhoppers and potential host plants clearly revealed aggregated patterns. Plant segregation suggests heterogeneous resource availability and competitive interactions, while leafhopper aggregation suggests host feeding differentiation at the local level, different feeding microhabitats on host plants, and similar environmental requirements of the species. Using the novel mbRA, we disentangle for the first time the relative importance of more than five distinct groups of variables shaping local species communities. We highlighted the important role of abiotic processes mediated by bottom-up effects of plants on leafhopper communities. Our results revealed that in-field structure diversification and trophic interactions are the main factors causing the co-occurrence patterns observed.Fil: Trivellone, Valeria. Swiss Federal Institute for Forest, Snow and Landscape Research; SuizaFil: Bougeard, Stephanie. French Agency for Food, Environmental and Occupational Health Safety; FranciaFil: Giavi, Simone. Swiss Federal Institute for Forest, Snow and Landscape Research; SuizaFil: Krebs, Patrik. Swiss Federal Institute for Forest, Snow and Landscape Research; SuizaFil: Balseiro, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Dray, Stephane. Université Claude Bernard Lyon 1; FranciaFil: Moretti, Marco. Swiss Federal Institute for Forest, Snow and Landscape Research; Suiz

Radiaciones y extinciones del Paleozoico temprano

Entre los temas de divulgación científica relacionados con la naturaleza o con acontecimientos biológicos, las catástrofes suelen atraer la mayor atención, entre ellas las extinciones masivas del tipo de la que eliminó a los dinosau- rios. No es tan frecuente que se recalquen sucesos más promisorios para el devenir de la vida, por ejemplo, la grandes radiaciones o diversificaciones. No obstante, extinciones y radiaciones han marcado la vida en el planeta y están ín- timamente relacionadas entre sí, ya que luego de las pri- meras sobrevienen las segundas y abren caminos para que se generan cambios profundos en la biota. La edad de la Tierra se suele estimar en unos 4600 mi- llones de años (Ma). En ese marco temporal, se calcula que los primeros registros de seres vivos, en forma de rastros de bacterias, datan de hace aproximadamente 3500Ma. El progreso de la vida en sus tiempos iniciales fue sumamen- te lento, pues solo a partir de hace unos 541Ma, cuando comenzó el Cámbrico, el primer período de la era paleo- zoica, se produjo un importante incremento de su ritmo de avance. Nos referimos a la radiación o explosión cámbrica –también tratada en el artículo ‘Los trilobites y el Paleo- zoico temprano’ en la página 17 de este número–, que causó la mayor diversificación de la que se tiene noticias y dio lugar a la aparición de los grandes tipos o phyla de animales. Luego de ese episodio ocurrió otra radiación, de menor escala, considerada por algunos una continuación de la anterior, que abarcó los taxones de menor rango de cada phylum. Se la conoce como la gran radiación ordovícica y acaeció a lo largo de casi todo el período geológico de ese nombre (485-444Ma), el segundo del Paleozoico.Fil: Carrera, Marcelo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Balseiro, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentin

Origen y diversificación de la Fauna Evolutiva de Trilobites Ibex-II (Furongiano tardío-Ordovícico Temprano) en el noroeste argentino

Faunas Evolutivas de Trilobites (FET) fueron propuestas como grupos de familias de trilobites que tienen trayectorias de diversidad en común. En particular la FET whiterockiana, objeto de intensos estudios, se habría originado en ambientes intermedios de plataforma carbonática y sólo más tarde accedería a ambientes litorales y marino profundos. Analizamos aquí en detalle la trayectoria de diversidad y abundancia de la etapa de desarrollo inicial, y posterior expansión de la FET Ibex-II durante el Furongiano tardío-Ordovícico Temprano. La fauna estudiada se desarrolló en una cuenca de foreland con altas tasas de sedimentación silicoclástica (Grupo Santa Victoria, Cordillera Oriental, noroeste argentino). En este contexto, la FET Ibex-II tiene su origen como elementos raros en ambientes intermedios de la plataforma durante el Furongiano tardío. Más tarde (Tremadociano medio), los miembros de la FET Ibex-II son poco diversas pero abundantes (no dominantes) en ambientes litorales si bien están aún ausentes en los ambientes más profundos. Los miembros de la FET Ibex-II dominan las comunidades a lo largo de todo el perfil batimétrico a partir del Tremadociano tardío. En el Floiano la FET Ibex-II es diversa y dominante, tanto a través del gradiente onshore-offshore como del óxico-disóxico, y muestra una dinámica de diversificación variada con un fuerte control ambiental dada por la radiación de formas endémicas y en menor medida inmigración. Estudios paleoecológicos de detalle muestran que la FET Ibex-II se relaciona en su origen con comunidades desarrolladas en ambientes con disturbio intermedio y sus componentes son formas en mayor medida cosmopolitas. Su trayectoria de diversidad y abundancia subsecuente sugiere que las distintas familias de trilobites que componen la FET Ibex-II exhiben historias y patrones de diversificación dispares tanto a escala regional como global. Estudios de mayor detalle permitirán esclarecer si la FET Ibex-II es una entidad biológica o un epifenómeno macroevolutivo.Sesiones libresFacultad de Ciencias Naturales y Muse

BRACHIOPOD ASSEMBLAGES OF THE EURYDESMA FAUNA IN GLACIAL- DEGLACIAL SEQUENCES FROM ARGENTINA AND AUSTRALIA

The Eurydesma Fauna characterizes the Late Pennsylvanian-Permian glacial-postglacial sediments recorded in several Gondwanan basins during the Late Paleozoic Ice Age (LPIA). Brachiopods, as one the most significant components of this fauna, are herein analyzed along with the associated bivalves, in two key sections from western and eastern Gondwana (Bonete Formation in the Sauce Grande Basin, eastern Argentina, and the Wasp Head Formation in the southern Sydney Basin, eastern Australia). The preliminary quantitative analysis indicates a high compositional similarity in both regions but occupancy exhibits important differences: brachiopod-dominated faunas can be found in eastern Australia (Tomiopsis and Trigonotreta are the most frequent taxa), and bivalve-dominated faunas are characteristic in eastern Argentina, where the brachiopods are poorly represented with the genera Tivertonia and Tomiopsis. In this locality, the development of r-strategy taxa, such as the bivalve Eurydesma, during the end of a glacial episode would adversely affect brachiopods’ abundance. This is also consistent with previous studies that indicate that brachiopods already showed a decrease in importance in Pennsylvanian communities from Argentina. Relative abundances of brachiopods and bivalves in both localities may reflect differences in the regional environmental conditions but, unfortunately, eastern Argentina lacks younger records to compare the faunal turnover with that of the Australian sequences. Despite the ecological structural differences identified (i.e. brachiopod:bivalve ratio), the postglacial Eurydesma fauna flourished in western and eastern Gondwana and it is striking that two faunas located on the opposite margins of this paleocontinent show such high compositional similarity during the development of a global postglacial event. This is particularly significant considering that the type of the basins (i.e. restricted vs open basins), biological features, paleoenvironmental conditions directly related to glacial dynamics, and also the diachronism of the transgression, can be controlling the composition of this fauna

Glaciomarine sequence stratigraphy in the Mississippian Río Blanco Basin, Argentina, southwestern Gondwana: Basin analysis and palaeoclimatic implications for the Late Paleozoic Ice Age during the Tournaisian

The Late Paleozoic Ice Age (LPIA) has been well recorded in the uppermost Mississippian?Pennsylvanian of Gondwana. Nevertheless, little is known about the temporal and geographic dynamics, particularly during the early Mississippian. We report on exceptional Tournaisian glaciomarine stratigraphic sections from central Argentina (Río Blanco Basin). Encompassing c. 1400 m, these successions contain conspicuous glacigenic strata with age constraints provided bypalaeontological data and U/Pb detrital zircon age spectra. A variety of marine, glaciomarine and fan-deltaic environments indicate relative sea-level variations mainly associated with tectonism and repetitive cycles of glacial activity. Provenance analysis indicates a source from the Sierras Pampeanas basement located to the east. Fifteen sequences were grouped into threedepositional models: (1) Transgressive Systems Tracts (TST) to Highstand Systems Tracts (HST) sequences unaffected by glacial ice; (2) Lowstand Systems Tracts (LST) to TST and then to HST with glacial influence; and (3) non-glacial Falling-Stage Systems Tracts (FSST) to TST and HST. The glacial evidence indicates that the oldest Mississippian glacial stage of the LPIA in southwestern Gondwana is constrained to the middle Tournaisian. In contrast with previous descriptions of Gondwanan coeval glacial records, our sequence analysis confirms complex hierarchical climate variability, rather than a single episode of ice advance and retreat.Fil: Ezpeleta, Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina. Universidad Nacional de La Rioja; ArgentinaFil: Rustán, Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina. Universidad Nacional de La Rioja; ArgentinaFil: Balseiro, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Davila, Federico Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Dahlquist, Juan Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Vaccari, Norberto Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina. Universidad Nacional de La Rioja; ArgentinaFil: Sterren, Andrea Fabiana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Prestianni, Cyrille. Royal Belgian Institute of Natural Sciences; BélgicaFil: Cisterna, Gabriela Adriana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina. Universidad Nacional de La Rioja; ArgentinaFil: Basei, Miguel. Universidade de Sao Paulo; Brasi

Compositional turnover and ecological changes related to the waxing and waning of glaciers during the Late Paleozoic Ice Age in ice-proximal regions (Pennsylvanian, Western Argentina)

The Late Palezoic Ice Age had a profound effect on the biota. Despite much research has been focused on paleotropical regions or global-scale analyses, regional ecological changes have seldom been studied in ice-proximal basins. Here, I study the compositional turnover and diversity structure across the main Carboniferous glacial event recorded in western Argentina and the subsequent non glacial interval. Brachiopod and bivalve data from western Argentina suggest that the transition from glacial to non-glacial climates caused major compositional changes. Turnover, however, was not uniform across the bathymetric gradient, being higher in deep environments. Because extirpation was concentrated in brachiopods, but immigration was similar in both clades, the taxonomic structure of the region was significantly modified. Although regional hierarchical diversity structure and occupancy distributions remained stable, dissecting the analysis in brachiopods and bivalves underscores that both clades had different responses to climate change. Brachiopods, on the one hand, show stability in the diversity structure and a very slight decrease in occupancies of intermediate genera, while bivalves show an important rise in diversity both at the environment and regional scale, and an increase in genera with intermediate occupancies. The bathymetric diversity gradient was also modified from humped shaped with maximum diversity in the deep subtidal, to a linear gradient with maximum values towards the offshore. However, relative compositional differences within environments remained stable with maximum values at intermediate depths both in glacial and non-glacial intervals. Moreover, local scale coexistence between brachiopods and bivalves changed in the non-glacial interval showing significant segregation, indicating relevant modifications in community assembly dynamics. Results from western Argentina highlight the magnitude of regional scale ecological changes during the LPIA in ice-proximal regions, suggesting that the waxing and waning of glaciers was able to cause regional taxonomic turnover and medium-scale ecological changes even during intervals of relative macroevolutionary quiescence.Fil: Balseiro, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentin

Systematic classification

Systematic classification of each genus used in the analyse

List of Taxa

List of genera present in each studied interval (i.e. Bashkirian or Moscovian-Kasimovian