Non‐congruent fossil and phylogenetic evidence on the evolution of climatic niche in the Gondwana genus Nothofagus

Abstract

Aim We used fossil and phylogenetic evidence to reconstruct climatic niche evolution in Nothofagus, a Gondwana genus distributed in tropical and temperate latitudes. To assess whether the modern distribution of the genus can be explained by the tropical conservatism hypothesis, we tested three predictions: (1) species from all Nothofagus subgenera coexisted under mesothermal climates during the early Eocene; (2) tolerance to microthermal climates evolved during the Eocene-Oligocene cooling from an ancestor that grew under mesothermal conditions; and (3) the climatic niche in Nothofagus is phylogenetically conserved.Location Australia, New Zealand, New Caledonia, Papua-New Guinea and South America.Methods We estimated the palaeoclimate of the Early Eocene, fossil-bearing Ligorio Marquez Formation (LMF, Chile), using coexistence and leaf physiognomic analysis. We reconstructed ancestral climatic niches of Nothofagus using extant species distributions and a time-calibrated phylogeny. Finally, we used the morphological disparity index and phylogenetic generalized least squares to assess whether climatic variables follow a Brownian motion (BM) or an Ornstein-Uhlenbeck (OU) model of evolution.Results Our palaeoclimatic estimates suggest mesothermal conditions for the LMF, where macrofossils associated with subgenera Lophozonia and possibly Fuscospora, and fossil pollen of Brassospora and Fuscospora/Nothofagus were recorded. These results are not supported by our phylogenetic analysis, which instead suggests that the ancestor of Nothofagus lived under microthermal to marginally mesothermal conditions, with tolerance to mesothermal conditions evolving only in the subgenus Brassospora. Precipitation and temperature dimensions of the realized climatic niche fit with a gradual BM or constrained OU model of evolution. Main ConclusionsOur results suggest that the use of phylogenetic reconstruction methods based only on present distributions of extant taxa to infer ancestral climatic niches is likely to lead to erroneous results when climatic requirements of ancestors differ from their extant descendants, or when much extinction has occurred.

Southern beech (Nothofagaceae) fossil leaves from the Río Turbio Formation (Eocene–?Oligocene), Santa Cruz Province, Argentina.

“…Imprints of leaves related to Nothofagus were recently mentioned by Leppe et al (2017) from the Lower Maastrichtian of Chile but these fossils remain undescribed in detail. Confident imprints of leaves with Nothofagus affinity were recorded in the Paleocene of Antarctica (Dusén, 1908;Tosolini et al, 2013) and in the Paleocene/ Eocene boundary of central Patagonia (Okuda et al, 2006;Hinojosa et al, 2015) but the lineage only became widespread and diverse after the middle Eocene becoming more abundant during the Oligocene (Barreda & Palazzesi, 2007;Hinojosa, 2015). Moreover, the middle Eocene-early Oligocene interval was characterized by the invasion of Nothofagus forests in Patagonia in close agreement with a marked cooling trend (Barreda & Palazzesi, 2007).…”

“…Even when leaves of Nothofagus were recorded in Patagonia from the Paleocene Ligorio Marquez Formation (Hinojosa et al, 2015), they still remain absent in several associations recovered from the early Eocene (e.g. Río Pichileufú (Berry,1938), Laguna del Hunco (Berry, 1925, Wilf et al, 2003, Quinamavida (Troncoso, 1992) and the floras from Arauco, Caleta Cocholgüe and Lota Coronel, (Engelhardt, 1891;Moreno-Chacón, 2000;Moreno-Chacón et al, 2000Gayó, 2001)).…”

Historical reconstruction of climatic and elevation preferences and the evolution of cloud forest-adapted tree ferns in Mesoamerica

“…Therefore, their results suggesting that the distributions of tree fern sporophytes strongly limited by annual precipitation is consistent with the current interpretation of gametophyte ecological observations (Bystriakova, Schneider & Coomes, 2011). Thus, we used distributions of extant descendants to assess climate niches of ancestors assuming that tree ferns are only able to inhabit in warm and wet habitats as suggested by Hinojosa et al (2015). Nonetheless, the phylogenetic reconstruction methods used here to infer ancestral distributions and climatic niches based on present distributions of extant taxa are likely to lead to erroneous results when climatic requirements of ancestors differ from their extant descendants, or when much extinction has occurred (Hinojosa et al, 2015).…”

“…Thus, we used distributions of extant descendants to assess climate niches of ancestors assuming that tree ferns are only able to inhabit in warm and wet habitats as suggested by Hinojosa et al (2015). Nonetheless, the phylogenetic reconstruction methods used here to infer ancestral distributions and climatic niches based on present distributions of extant taxa are likely to lead to erroneous results when climatic requirements of ancestors differ from their extant descendants, or when much extinction has occurred (Hinojosa et al, 2015). Although some evidence of variation in extinction rates has been recently reported among three high-diversity clades (i.e., Sphaeropteris clade, A. australis clade and C. multiflora clade; a more densely sampled phylogeny would be needed to fully test hypotheses related to clade-specific extinction rates.…”

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“…stabilizing selection) that favoured the ancestral niche over time [12]. Recently, Hinojosa et al [55] [66,67]. Gunnera species also quickly colonise glacial forelands [68] and their pollen is commonly found in glacial and post-glacial sediments in both southern South America and in Tasmania [69,70].…”