Browsing by Author "Segovia, Ricardo A."

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    Freezing and water availability structure the evolutionary diversity of trees across the Americas
    (2020) Segovia, Ricardo A.; Pennington, R. Toby; Baker, Tim R.; de Souza, Fernanda Coelho; Neves, Danilo M.; Davis, Charles C.; Armesto, Juan J.; Olivera-Filho, Ary T.; Dexter, Kyle G.
    The historical course of evolutionary diversification shapes the current distribution of biodiversity, but the main forces constraining diversification are still a subject of debate. We unveil the evolutionary structure of tree species assemblages across the Americas to assess whether an inability to move or an inability to evolve is the predominant constraint in plant diversification and biogeography. We find a fundamental divide in tree lineage composition between tropical and extratropical environments, defined by the absence versus presence of freezing temperatures. Within the Neotropics, we uncover a further evolutionary split between moist and dry forests. Our results demonstrate that American tree lineages tend to retain their ancestral environmental relationships and that phylogenetic niche conservatism is the primary force structuring the distribution of tree biodiversity. Our study establishes the pervasive importance of niche conservatism to community assembly even at intercontinental scales.
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    GENETIC EVIDENCE FOR GLACIAL REFUGIA OF THE TEMPERATE TREE EUCRYPHIA CORDIFOLIA (CUNONIACEAE) IN SOUTHERN SOUTH AMERICA
    (2012) Segovia, Ricardo A.; Perez, Maria F.; Hinojosa, Luis F.
    Premise of the study: The temperate forests of southern South America were greatly affected by glaciations. Previous studies have indicated that some cold-tolerant tree species were able to survive glacial periods in small, ice-free patches within glaciated areas in the Andes and in southern Patagonia. Here we asked whether populations of the mesothermic species Eucryphia cordifolia also were able to survive glaciations in these areas or only in unglaciated coastal areas.
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    The extinct Notiomastodon platensis (proboscidea, Gomphoteriidae) inhabited mediterranean ecosystems during the Late Pleistocene in north-central Chile (31°S-36°S)
    (2024) Gonzalez-Guarda, Erwin; Segovia, Ricardo A.; Valenzuela, Matias; Asevedo, Lidiane; Villavicencio, Natalia; Tornero, Carlos; Ramirez-Pedraza, Ivan; Ortega, Sebastian; Capriles, Jose; Labarca, Rafael; Latorre, Claudio
    Limited pollen and limnogeological evidence show that central Chile (31 degrees S-36 degrees S) had a more temperate climate during the Late Pleistocene. Questions remain, however, regarding the extent of the mediterranean sclerophyllous forest currently found in this region and its postglacial dynamics. The extinct Notiomastodon platensis was the only proboscidean species that inhabited central Chile and ranged across a broad latitudinal range (31 degrees S-42 degrees S) during the Pleistocene. Although this species was a mixed-feeder, we reconstructed past ecosystems when these animals were alive using stable isotope evidence from dental root collagen (delta C-13 and delta N-15) of N. platensis specimens collected from present-day semi-arid and mediterranean ecosystems in central Chile (31 degrees S-36 degrees S). Compared to modern vegetation isotope baselines, we expected the isotopic value of the Estimated Consumed Diet (ECD) (the probable diet of N. platensis) to be similar to the isotopic signal (low values) from vegetation adapted to temperate rainforests. However, elevated delta N-15(ECD) values indicate a paleo-vegetation more similar to a xerophyte scrub influenced by a semi-arid paleoclimate. delta C-13(ECD) values reflect a wooded/forested environment but adapted to more arid conditions. Although high delta N-15 values could be influenced by other non-climatic factors (e.g., grazing effect), our combined evidence suggests that these gomphotheres roamed through ecosystem very similar to those found today in central Chile. Our results show the need for multiproxy reconstructions of past environmental change in Mediterranean regions where the abundance of entomophilous species can lead to biased pollen reconstructions.