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How to score taxa?

Every taxon (element) should be assigned to one of the components listed above. The taxa have been scored as “present” (1) or “absent” (0) in every flora. When a taxon cannot be unambiguously attributed to one of the components, it can be given a fractional value in more than one component. This assignment has been primarily based on taxonomy and autecology (zonal or azonal), the latter derived from observations of the fossil record and the nearest living relatives (NLRs). If the botanical affinity of a taxon is dubious, it can be assigned according to its leaf physiognomy (available in the leaf record) and observations in the overall fossil record (zonal versus azonal).

Kovar-Eder et al. (2008) showed several examples of scoring based on the fossil record. The genus Magnolia includes deciduous and evergreen trees with entire-margined leaves. Today, Magnolia species occur in either mesic or wetland habitats. Leaves of the fossil Magnolia liblarensis (Kräusel & Weyland) Kvaček possess rather thin cuticles and occur quite commonly, but not exclusively, in coal facies, indicating a preference of this plant for wetland environments (Kovar-Eder & Meller, 2001). The folige may have been evergreen or deciduous. Consequently, Magnolia liblarensis is assigned to the BLD, BLE, and AZW components (one-third each). The fruits of Magnolia burseracea (Menzel) Mai are assigned exclusively to the AZW component because they are characteristically found in swampy facies where they may occur in great quantities (Mai 1975). Based on the physiognomy and autecology of modern and fossil Magnolia species, fossil Magnolia pollen is assigned to the BLD, BLE, and AZW components (one-third each). Grasses (Poaceae), available in the pollen record but hardly ever subdivided further, are split: two-thirds to the zonal herbs (one-third DRH and one-third MEH) and one-third to the AZH component. This assignment is based on the wide autecology of modern Poaceae. Bambusoid grasses as well as many basal grasses prefer shady (zonal and azonal) habitats, and high abundance of Poaceae pollen does not necessarily indicate Open vegetation conditions. This aspect has been exhaustively discussed by Strömberg (2004). In contrast, pollen of sedges (Cyperaceae), which is not further subdivided in the fossil record, is assigned 0.8 to the AZNW and 0.2 to the M-HERB component because most, but not all, sedges thrive in damp sites (Judd et al., 1999).

Within the leaf record, the taxonomy and leaf physiognomy of every taxon in almost all assemblages has been checked individually for the correct assignment to the established components. This has been performed mainly by screening all publications (descriptions and figures of leaf and fruit floras), partly by investigating collection material. For palynological data, the evaluation has largely been based on floral lists, and the assignment has been restricted to sporomorph and palynomorph taxa whose natural affinities are well understood. Unfortunately, these data are not available for all taxa, and many of them still await detailed comparative studies. All taxa (leaf, fruit, pollen) that are assignable based on the above criteria have been counted but excluded from any further evaluation having been scored as problematic taxa (Kovar-Eder et al., 2008).