52 million years old Eucalyptus flower sheds more than pollen grains

Abstract

PREMISE Fossils provide fundamental evidence of the evolutionary processes that crafted today’s biodiversity and consequently for understanding life on Earth. We report the finding of Myrtaceidites eucalyptoides pollen grains preserved within the anthers of a 52‐million‐year‐old Eucalyptus flower collected at Laguna del Hunco locality of Argentinean Patagonia and discuss its implications in understanding the evolutionary history of the iconic Australian genus Eucalyptus. METHODS Pollen grains were extracted from the flower’s anthers and were then observed under light microscopy and scanning electron microscopy. The phylogenetic position of the fossil was investigated by adding pollen data to a previously published total‐evidence matrix and analyzing it using parsimony. RESULTS We erect the species Eucalyptus xoshemium for the fossil flower. Pollen extracted from E. xoshemium belongs to the species Myrtaceidites eucalyptoides, which, until now, was only known as dispersed pollen. The numerous pollen grains recovered from the single flower allowed estimation of M. eucalyptoides’ variability. Results of the phylogenetic analysis reinforce the position of this fossil within crown group Eucalyptus. CONCLUSIONS The discovery of these pollen grains within a Patagonian Eucalyptus fossil flower confirms the hypothesis that Myrtaceidites eucalyptoides represents fossil pollen in the Eucalyptus lineage, extends the geographic and stratigraphic fossil pollen record, and supports an earlier age for crown‐group eucalypts.

Cunoniaceae infructescences from the early Eocene Laguna del Hunco flora, Patagonia, Argentina

“…Thus, the age of all the fossils is close to 52 Ma, within the Early Eocene Climatic Optimum. The paleoflora includes leaf, flower, fruit, pollen, and wood fossils (Zamaloa et al, 2006, 2020; Gonzalez et al, 2007; Wilf et al, 2009, 2014, 2017a, 2017b, 2019; Gandolfo et al, 2011; Hermsen et al, 2012; Wilf, 2012; Knight and Wilf, 2013; Carpenter et al, 2014; Hermsen and Gandolfo, 2016; Deanna et al, 2020; Barreda et al, 2020; Brea et al, 2021) and is considered to be one of the most diverse Eocene fossil compression floras ever discovered (Wilf et al, 2003, 2005). The paleoflora also has extensive, significant biogeographic connections to the West Pacific, particularly the extant montane rainforests of the Malay Archipelago and subtropical notophyll forests of eastern Australia (Wilf et al, 2013; Kooyman et al, 2014; Merkhofer et al, 2015).…”

Propagation of a U16 hybid Eucalyptus line by plant cell tissue culture

“…Eucalyptus spp., be long to Myrtaceae are trees variety recognized for its remarkable traits including rapid growth and superior wood quality [1]. Them have cultivated spanning over 20 million hectares across more than 90 nations, with focal points situated predominantly in Brazil (covering 5.7 million hectares), India (spanning 3.9 million hectares), and China (encompassing 4.5 million hectares) [2]. Its status as one of the most widely cultivated hardwood trees globally remains prominent.…”