Palaeogeography and palaeoenvironments of northern Patagonia from the Late Cretaceous to the Miocene: the Palaeogene Andean gap and the rise of the North Patagonian High Plateau

Species diversification in the lowlands of mid-latitude South America: Turnera sidoides subsp. carnea as a case study

The lowlands of mid-latitude South America comprise complex temperate ecoregions characterized by a unique biodiversity. However, the processes responsible for shaping its species diversity are still largely unknown. Turnera sidoides subsp. carnea is a variable subspecies occurring in the lowlands of northeastern Argentina and Uruguay, extending to southern Paraguay and Brazil. It constitutes a good model to perform evolutionary studies. Here we used an integrative approach to understand the process of diversification within this subspecies and to increase the knowledge concerning patterns and processes responsible for shaping the species diversity in the temperate lowlands of South America. The results provided strong evidences that this subspecies is an autopolyploid complex per se, being in an active process of intrasubspecific diversification. Morphological and genetic data show that the diversity of T. sidoides subsp. carnea is in congruence with the great past and present abiotic and biotic variability of the mid-latitude South American lowlands. The evolutionary history of this subspecies is consistent with past fragmentation and allopatric differentiation at diploid level. Geographic isolation and local adaptation would have promoted strong morphological, ecological, and genetic differentiation, resulting in two morphotypes and different genetic groups indicative of incipient speciation.

New Insights into the Distribution, Physiology and Life Histories of South American Galaxiid Fishes, and Potential Threats to This Unique Fauna

South American galaxiids occupy both Patagonia and the ichthyogeographic Chilean Province, encompassing glacial Andean deep lakes, shallow plateau lakes, reservoirs, short Pacific rivers and long Atlantic rivers. The total fish fauna includes 29 species, comprising Neotropical fishes (siluriforms and characids), galaxiids, percichthyids, atherinopsids and mugilids, two lamprey species, and several exotic fishes (salmonids, Gambusia spp. and common carp). The family Galaxiidae shares a common ancestry with the Gondwanan temperate fish fauna, played a major role in the post-glacial colonization of Andean lakes and streams, and contributes key species to the food webs. Galaxiid species occupy an enormous latitudinal gradient, show a wide variety of life history patterns and are the southernmost native freshwater fishes of the world. Knowledge of South American galaxiids has improved notably, but new challenges arise due to climate change, biological invasions, damming, aquaculture and contamination. In this changing environment, the future of South American galaxiids should be carefully considered as a legacy of the old Gondwana and a unique attribute of the freshwaters of southern South America.

Phylogeographical patterns shed light on evolutionary process in South America

The South American continent is composed of several biogeographical regions harbouring the highest biodiversity on the globe, encompassing five of the world's biodiversity 'hot spots'. Nonetheless, the patterns and processes responsible for shaping its astonishing species diversity are largely unknown. Here, we present a review of current South American phylogeographical knowledge based on published articles on this topic. An appraisal of the literature reveals emerging phylogeographical patterns in the biota of South America. The striking phylogeographical divergence observed among organism lineages in South American studies is suggestive of high levels of undocumented species diversity. The interplay between Pleistocene climatic oscillations and Pliocene/Miocene orogenic events has contributed to shaping the current diversity and distribution of modern lineages in both the tropical and temperate regions of South America. Although older divergence times were observed for a range of species, most herpetofauna underwent an intraspecific lineage split much earlier than other organisms. The geographical ranges of species associated with forest habitats were reduced mainly during glacial cycles, whereas species associated with open vegetation domains have shown variable responses to climatic oscillations. The results suggest a highly complex mosaic of phylogeographical patterns in South America. We suggest future research directions to promote a better understanding of the origin and maintenance of the South American biota.

Rainforest conifers of Eocene Patagonia: attached cones and foliage of the extant Southeast Asian and Australasian genus Dacrycarpus (Podocarpaceae)

PREMISE OF THE STUDY

Eocene caldera-lake beds at Laguna del Hunco (LH, ca. 52.2 Ma) and Río Pichileufú (RP, ca. 47.7 Ma) in Argentine Patagonia provide copious information about the biological history of Gondwana. Several plant genera from these sites are known as fossils from southern Australia and New Zealand and survive only in Australasian rainforests. The potential presence of Dacrycarpus (Podocarpaceae) holds considerable interest due to its extensive foliage-fossil record in Gondwana, its remarkably broad modern distribution in Southeast Asian and Australasian rainforests, its high physiological moisture requirements, and its bird-dispersed seeds. However, the unique seed cones that firmly diagnose Dacrycarpus were not previously known from the fossil record.

METHODS

I describe and interpret fertile (LH) and vegetative (LH and RP) material of Dacrycarpus and present a nomenclatural revision for fossil Dacrycarpus from South America.

KEY RESULTS

Dacrycarpus puertae sp. nov. is the first fossil occurrence of the unusual seed cones that typify living Dacrycarpus, attached to characteristic foliage, and of attached Dacrycarpus pollen cones and foliage. Dacrycarpus puertae is indistinguishable from living D. imbricatus (montane, Burma to Fiji). Dacrycarpus chilensis (Engelhardt) comb. nov. is proposed for Eocene vegetative material from Chile.

CONCLUSIONS

Modern-aspect Dacrycarpus was present in Eocene Patagonia, demonstrating an astonishingly wide-ranging paleogeographic history and implying a long evolutionary association with bird dispersers. Dacrycarpus puertae provides the first significant Asian link for Eocene Patagonian floras, strengthens the biogeographic connections from Patagonia to Australasia across Antarctica during the warm Eocene, and indicates high-rainfall paleoenvironments.