Usually, scholars dealing with modern and past biology of plants develop parallel and overlapping researches, sometimes with poor interchanges. A recent study of the genus Carex showed that the existing knowledge about the fossil record is neglected by people dealing with the biology of this genus, almost ignoring the wealth of information poten- tially useful for their studies that is available in several palaeobotanical collections. To overcome this missing communication we present the first step of a project aiming at revising and summarizing the fossil record of taxa recorded in the modern Italian flora. The team of authors has been assembled starting from a group of persons working with fossil records (mainly the BRAIN network) who invited experts of modern floristics to analyse and discuss the palaeobotanical data in the light of the knowledge on the modern flora. The focus is on Italy, because of the exceptionally rich plant fossil record of this country. Furthermore, the Italian record ade- quately covers the last 6 Ma, in a less discontinuous way than in other countries. Such analysis addressed to a national perspective does not preclude an expansion to an Eurasian and global scale; this is true for example when analysing evolutionary and historical bio- geography issues, for which a country-scaled analysis may not be successful. We choose to start this project with Lycopus. This genus has a highly diagnostic morphology of fossilizable parts (nutlets), it has a well-assessed phylogenetic placement and its divergence from the most closely related genera is attributed to relatively deep times. The fossil record of Lycopus is mainly represented by nutlets, that are easily preserved in sedimentary deposits containing scarcely to moderately altered organic matter, and were formed in waterlogged continental palaeoenvironments. The nutlet morphology is considered to provide diagnostic characters for the distinction of the living species. Contrarily, pollen grains are not easily identifiable at the light microscope, thus they are com- monly included in the Mentha type or in the Lamiaceae undifferentiated grains. The genus Lycopus includes approximately 16 species, distributed in the northern Hemisphere and in Australia. In Europe, three species are known: Lycopus europaeus L., L. exaltatus L.f. and L. lucidus Turcz. ex Benth., the latter intro- duced in recent times from eastern Asia. In contrast to the purported “lack of a strong fossil record”, several authors reported fossil fruit records in Europe and West Asia: from the oldest ones of the Oligocene (ca. 30 Mya), limited to West Siberia, through the more frequent Miocene (23- 5 Mya) records, ranging from West Siberia to central Europe, to the abundant Pliocene and Pleistocene records (5-0.01 Mya). The last ones were mainly assigned to the modern species L. europaeus, whereas the Oligocene and Miocene records (plus a few Pliocene ones) were assigned to the fossil-species L. antiquus E.M.Reid. The Italian fossil records assigned to Lycopus have been reported in a table, where the localities have been listed alphabetically within selected time intervals. The preliminary analysis of these data suggests that several fossil records dating from 4 Ma to 0.1 Mya show a morphology of the nutlet’s collar which is diagnostic for L. europaeus. The occur- rence of fossil nutlets which possibly refer to L. exaltatus is under investigation for a site dating ca. 1.5-1.3 Ma, while the abundant Holocene records, including some archaeologi- cal sites, are only referred to L. europaeus. The available fossil records firmly demonstrate the long-lasting presence of L. europaeus in Italy and its widespread occurrence in the Holocene. The past occurrence of other exotic or extinct species of Lycopus does not emerge from the fossil record.
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|Data di pubblicazione:||2015|
|Autori:||Martinetto, E.; Ardenghi, N.M.G.; Arobba, D.; Bertini, A.; Bosi, G.; Caramiello, R.; Castiglioni, E.; Florenzano, A.; Maritan, M.; Mazzanti, M.; Mercuri, A.M.; Miola, A.; Perego, R.; Ravazzi, C.; Rinaldi, R.; Rottoli, M.|
|Titolo:||Digging up the roots of the Italian flora, 1. Fossil record of Lycopus (Lamiaceae, Mentheae)|
|Appare nelle tipologie:||Abstract in Atti di Convegno|
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