Light and scanning electron microscopic investigations of pollen of Ericales (Ericaceae, Sapotaceae, Ebenaceae, Styracaceae and Theaceae) from five lower and mid-Eocene localities.

As scanning electron microscopy (SEM) has not been routinely used in palaeo-palynology, affiliations of fossil pollen to botanical equivalents, based only on light microscopy (LM), are always equivocal. Here 29 taxa of Ericales 55.8–41.2 My in age have been identified using LM and SEM, modifying the evolutionary and palaeo-biogeographical framework of some Ericales. Seven Ericaceae types, 17 Sapotaceae types, three Ebenaceae types, one Styracaceae type and one Theaceae type were identified to tribe or genus level. A 56-My-old Erica -type affiliated with Erica arborea might be the ancestor of African Erica taxa, whereas a younger type with affinities to palaeo-Arctic Erica might be the precursor of northern European heathers. The Kalmia -type suggests a European origin and a wider geographical distribution for this type during the mid-Eocene, and a Rhododendron -type of contemporaneous age corroborates the existence of numerous Rhododendron taxa in Europe. Both the 56-My-old Vaccinium -type, affiliated with temperate continental Asian taxa, and the Gaultheria -type, affiliated with several South American taxa, represent the oldest occurrences of these taxa and suggest a Eurasian origin. The Sapotaceae are represented by Sarcospermatoideae, with two Sarcosperma -types, Chrysophylloideae, with three Chrysophylleae-types affiliated with South American Pouteria / Elaeoluma and one affiliated with Asian Planchonella / Sersalisia , and Sapotoideae with three Mimusopeae/Isonandreae-types with mixed affinities, two Mimusopeae-types affiliated with African/Malegasy Mimusops / Vitellariopsis taxa, one Mimusopeae-type affiliated with South American Manilkara taxa, four Isonandreae-types affiliated with SE Asian Palaquium and one South American Sideroxylon -type. All Sapotaceae types are older than postulated in the literature by molecular dating analyses. Three Diospyros -types affiliated with African taxa corroborate a Gondwanan–African origin of the genus. A Styrax -type resembles extant South American and East Asian taxa and is interpreted as being an early European ancestor of Styrax. The contemporaneous Camellia -type represents the oldest record of Camellia. [ABSTRACT FROM AUTHOR]