Systematics of the genus Eupleura H. & A. Adams, 1853 (Mollusca: Gastropoda) in the Neogene to Recent of Tropical America (original) (raw)
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Boletín de la Sociedad Geológica Mexicana, 2019
RESUMEN El declive de la diversidad de especies dulceacuícolas es un fenómeno mundial, pero es especialmente pro-nunciado en las regiones áridas como en el Desierto Chihuahuense de Coahuila y Durango, norte-centro de México. Existen pocos datos históricos sobre la distribución y ninguna información sobre extinciones de gasterópodos dulceacuícolas mexicanos. En tales casos, los datos paleontológicos pueden ser muy útiles y, a menudo, son la única forma de documentar las distribuciones pasadas y los eventos locales de extin-ción u extirpación. Este nuevo enfoque paleoecológico, llamado Paleobiología de Conservación, puede propor-cionar perspectivas importantes para los esfuerzos de conservación de ecosistemas análogos recientes. El sitio de estudio contiene depósitos fósiles (Holoceno Tardío) del Distrito Laguna, un área pequeña en Coahuila y Durango. De estos depósitos fósiles describimos una nueva especie y reportamos varios registros nuevos de gasterópodos cochliópidos, hidróbidos, planórbidos y neritidos. La mayoría de estas especies y algunos géne-ros no se conocen como fósiles de México y todos ellos desaparecieron en tiempos muy recientes. En conjunto con datos de nuestros estudios paleomalacológicos anteriores, presentamos aquí un ejemplo de una extir-pación local "silenciosa" en el norte de México la cual comenzó en el Holoceno Medio. Esta pérdida de espe-cies aumentó rápidamente en la segunda mitad del siglo XX. De las 32 especies de caracoles dulceacuícolas presentes en el área de estudio durante el Holoceno, solo 4 (12.5%) aún existen. Al menos 24 (75.0%) de ellos desaparecieron del área en el siglo XX debido a la pérdida de hábitat causada por actividades antropogé-nicas. Nuestros resultados muestran que especialmente los hidróbidos con intervalos geográficos pequeños (especies endémicas locales) son altamente sensibles y vulnerables a tales acontecimientos de extirpación. La extirpación de los caracoles dulceacuícolas en el área de estudio ocurrió silenciosamente (sin registros), mien-tras que al mismo tiempo unos doscientos kilómetros más al norte, uno de los mayores focos de diversidad de gasterópodos en América del Norte permaneció en la cuenca de Cuatrociénegas. Las mismas amenazas que llevaron a la extirpación local en nuestra área de estudio aún amenazan a las comunidades de caracoles dulceacuícolas del valle de Cuatrociénegas. Palabras clave: Paleobiología, extirpación, gasterópodos, dulceacuícolas, pérdida de hábitat.
Functional diversity based on species traits is a powerful tool to investigate how changes in species richness and composition affect ecosystem functioning. However, studies aimed at understanding changes in functional diversity over large temporal and spatial scales are still scant. Here we evaluate the combined effect of diversification and species sorting on functional diversity of fossil marine gastropods during the Pliocene-Quaternary transition in the Pacific coast of South America. We analyzed a total of 172 species in 29 Pliocene and 97 Quaternary sites. Each species was characterized according to six functional traits: body size, feeding type, mobility, attachment, life-habit, and larval mode. Functional diversity was estimated according to four indexes (functional richness, evenness, divergence and dispersion) based on functional traits measured. Extrapolated species richness showed a slight yet not significant decrease from the Pliocene to the Quaternary despite the fact that a large faunal turnover took place; furthermore, a large extinction of Pliocene species (61–76%) was followed by a high pulse of appearances (49–56%) during the Quaternary. Three out of four indices of functional diversity (evenness, divergence and dispersion) increased significantly towards the Quaternary which is more than expected under a random turnover of species. The increase in functional diversity is associated with a loss of large-sized carnivore forms, which tended to be replaced by small-sized grazers. Hence, this trait-selective species turnover, even in the absence of significant changes in species richness, likely had a large effect and has shaped the functional diversity of present-day assemblages.
Non-native mollusks throughout South America: emergent patterns in an understudied continent
Biological Invasions, 2020
Non-native species have been introduced at escalating rates during the last decades, mainly due to the dispersion generated by the increasing trade and transport worldwide. Mollusks, the second largest metazoan phylum in terms of species richness, are no exception to this pattern, but, to date, a comprehensive synthesis of non-native mollusk species (NNMS) in South America was not available. For this purpose, an e-discussion group was formed with malacologists and taxonomists from South America, where we exchanged and analyzed bibliography, databases and information about NNMS, providing expert opinion to this assessment. The first list of non-native mollusk species for South America, considering terrestrial, freshwater and marine environments, includes 86 NNMS distributed in 152 ecoregions (terrestrial, freshwater and marine) of the 189 recognized for the South American continent. Information on their native region, vectors, first record for South America and distribution, are also provided. In the analysis of the distribution of the NNMS and the entry points of each species (e.g., ports, cargo and passenger airports, cities) and status of conservation of the ecoregions, four hot spots were recognized: Subtropical-Atlantic,
Thalassas: an International Journal of Marine Sciences, 2010
Among the several groups of molluscs in the southern hemisphere, the genus Trophon Montfort, 1810 has a particular importance, because it is a highly diversified taxon in the Southern Ocean and SubAntarctic waters. In the middle of the XX century, 27 species were known, which increased to 33 species at the beginning of the XXI century, but more than 100 species were described under this genus along the time, most of them being synonyms or belonging to other genera at the moment. Despite the great diversification of this genus, no summarizing data from these areas are known and some records are confused by using of combining genera/subgenera (i.e. Coronium Simone, 1996, Pagodula Monterosato, 1884, Nodulotrophon Habe & Ito, 1965 and Fuegotrophon Powell, 1951). In this work we gathered data of the distribution, shell morphology and taxonomic remarks of 46 species of Trophon (s.l.) starting from a performed database with all records toward the pole from about 20oS in South-American wate...