| 1. |
- Bolinder, Kristina, et al.
(författare)
-
Pollen morphology of Ephedra (Gnetales) and its evolutionary implications
- 2016
-
Ingår i: Grana. - : Informa UK Limited. - 0017-3134 .- 1651-2049. ; 55:1, s. 24-51
-
Tidskriftsartikel (refereegranskat)abstract
- The Ephedra lineage can be traced at least to the Early Cretaceous. Its characteristically polyplicate pollen is well-represented in the fossil record and is frequently used as an indicator of paleoclimate. However, despite previous efforts, knowledge about variation and evolution of ephedroid pollen traits is poor. Here, we document pollen morphology of nearly all extant species of Ephedra, using a combination of scanning electron microscopy (SEM) and light microscopy (LM), and reconstruct ancestral states of key pollen traits. Our results indicate that the ancestral Ephedra pollen type has numerous plicae interspaced by unbranched pseudosulci, while the derived pollen type has branched pseudosulci and (generally) fewer plicae. The derived type is inferred to have evolved independently twice, once along the North American stem branch and once along the Asian stem branch. Pollen of the ancestral type is common in Mesozoic fossil records, especially from the Early Cretaceous, but it is less commonly reported from the Cenozoic. The earliest documentation of the derived pollen type is from the latest Cretaceous, after which it increases strongly in abundance during the Paleogene. The results of the present study have implications for the age of crown group Ephedra as well as for understanding evolution of pollination syndromes in the genus.
|
|
| 2. |
- Bouchal, Johannes M., 1979-, et al.
(författare)
-
Low taxonomic resolution of papillate Cupressaceae pollen (former Taxodiaceae) impairs their applicability for palaeo-habitat reconstruction
- 2020
-
Ingår i: Grana. - London : Taylor & Francis. - 0017-3134 .- 1651-2049. ; 59:1, s. 71-93
-
Tidskriftsartikel (refereegranskat)abstract
- The former family Taxodiaceae is currently treated as nine genera in five subfamilies of the family Cupressaceae. Pollen ofthe ‘taxodiaceous’ Cupressaceae typically has a papilla in the leptoma area and is common in Cenozoic strata because someof its genera were key elements in lignite forming swamp forests. Dispersed fossil pollen of this group are often assigned toparticular genera and, based on the modern ecologies of these taxa, to particular palaeoenvironments. In this study, weinvestigated pollen of all nine genera of the former Taxodiaceae using light and scanning electron microscopy to evaluatewhether pollen morphology can be used to discriminate modern genera of this paraphyletic group. We found few genus- orsubfamily-diagnostic characters among members of taxodiaceous Cupressaceae. Features such as orbiculae and pollen andleptoma size cannot be used to discriminate subfamilies. However, three basal subfamilies share short papillae, whereas intwo more derived clades (Sequoioideae and Taxodioideae) papillae are markedly longer. In the generally non-papillate coreCupressaceae, the leptoma (aperture) area may or may not possess a distinct circular thinning as also found in the basalgrade of taxodiaceous Cupressaceae. Our results show that it is difficult if not impossible to distinguish genera of theecologically distinct Taxodioideae and Sequoioideae based on pollen morphology. In view of a much wider ecologicalamplitude of many taxodiaceous Cupressaceae during large parts of the Cenozoic, we conclude that it is not recommendableto infer particular palaeoenvironments on the basis of dispersed taxodiaceous pollen grains alone.
|
|
| 3. |
- Bouchal, Johannes M., 1979-
(författare)
-
Pollen and spores of the uppermost Eocene Florissant Formation, Colorado: A combined light and scanning electron microscopy study
- 2016
-
Ingår i: Grana. - : Taylor & Francis Group. - 0017-3134 .- 1651-2049. ; 55:3, s. 179-245
-
Tidskriftsartikel (refereegranskat)abstract
- The uppermost Eocene Florissant Formation, Rocky Mountains, Colorado, has yielded numerous insect, vertebrate, and plant fossils. Three previous comprehensive palynological studies investigated sections of lacustrine deposits of the Florissant Formation and documented the response of plant communities to volcanic eruptive phases but overall found little change in plant composition throughout the investigated sections. These studies reported up to 150 pollen and spore phenotypes. In the present paper we used a taxonomic approach to the investigation of dispersed pollen and spores of the Florissant Formation. Sediment samples from the shale units containing macrofossils were investigated using light microscopy (LM) and scanning electron microscopy (SEM). The general picture of the palynoflora is in agreement with previous studies. However, the combined LM and SEM investigation provides important complementary information to previous LM studies. While a fairly large amount of previous pollen determinations could be confirmed, the purported taxonomic affinities of several pollen phenotypes need to be revised. For example, pollen referred to as Podocarpus or Podocarpidites sp. belongs to the Pinaceae Cathaya, Malus/Pyrus actually belongs to Dryadoideae, pollen of the form genus Boehlensipollis referred to as Proteaceae/Sapindaceae/Elaeagnaceae or Cardiospermum belongs to Sapindaceae but not to Cardiospermum, and pollen of Persicarioipollis sp. B with previously assumed affinities to Polygonaceae actually belongs to Thymelaeaceae. Pandaniidites and one type of Malvacipollis cannot be linked with Pandanaceae and Malvaceae. A few taxa are new records for Florissant (Ebenaceae: Diospyros; Mernispermaceae; Trochodendraceae: Tetracentron). In general, SEM investigations complement the LM palynological studies and improve the identification of dispersed pollen and spores and enable integration of data from dispersed fossil pollen into a wide range of comparative morphological, taxonomic, evolutionary, biogeographic, and phylogenetic studies.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
- Friis, Else Marie, et al.
(författare)
-
Kenilanthus, a new eudicot flower with tricolpate pollen from the Early Cretaceous (early-middle Albian) of eastern North America
- 2017
-
Ingår i: Grana. - London : Taylor & Francis. - 0017-3134 .- 1651-2049. ; 56:3, s. 161-173
-
Tidskriftsartikel (refereegranskat)abstract
- Fossil evidence strongly indicates that the initial phylogenetic diversification of angiosperms during the Early Cretaceous involved many kinds of plants that are now extinct, and suggests that their closest living relatives are among extant angiosperms in the ANA-grade (Amborellales, Nymphaeales, Austrobaileyales), Chloranthaceae, eumagnoliids and early lineages of monocots (Friis et al. 2011). Eudicots also appear early in the diversification of angiosperms, as evidenced by the presence of isolated tricolpate pollen grains in palynological assemblages from around the Barremian-Aptian boundary onwards (Penny 1988, 1991; Doyle 1992; Hughes 1994). Early tricolpate pollen is known from floral remains and in coprolites in early mesofossil floras from Portugal (Friis et al. 2010a, 2011) and there are scattered reports of eudicot leaf fossils from Aptian to mid-Albian strata (e.g. Jud 2015). Eudicots become more common towards the end of the Albian. The earliest pollen grains that can unequivocally be assigned to eudicots are tricolpate, like the pollen produced by many extant early-diverging lineages in this clade. Tricolporate pollen grains, which occur in some basal grade eudicots, but that are more characteristic of core eudicots (Furness et al. 2007), are also present in the fossil record by the end of the Early Cretaceous.
|
|
| 10. |
- Friis, Else Marie, et al.
(författare)
-
Paisia, an Early Cretaceous eudicot angiospermflower with pantoporate pollen from Portugal
- 2018
-
Ingår i: Grana. - : Informa UK Limited. - 0017-3134 .- 1651-2049. ; 57, s. 1-15
-
Tidskriftsartikel (refereegranskat)abstract
- A new fossil angiosperm, Paisia pantoporata, is described from the Early Cretaceous Catefica mesofossil flora, Portugal, based on coalified floral buds, flowers and isolated floral structures. The flowers are actinomorphic and structurally bisexual with a single whorl of five fleshy tepals, a single whorl of five stamens and a single whorl of five carpels. Tepals, stamens and carpels are opposite, arranged on the same radii and tepals are involute at the base clasping the stamens. Stamens have a massive filament that grades without a joint into the anther. The anthers are dithecate and tetrasporangiate with extensive connective tissue between the tiny pollen sacs. Pollen grains are pantoporate and spiny. The carpels are free, apparently plicate, with many ovules borne in two rows along the ventral margins. Paisia pantoporata is the oldest known flower with pantoporate pollen. Similar pantoporate pollen was also recognised in the associated dispersed palynoflora. Paisia is interpreted as a possibly insect pollinated, herbaceous plant with low pollen production and low dispersal potential of the pollen. The systematic position of Paisia is uncertain and Paisia pantoporata most likely belongs to an extinct lineage. Pantoporate pollen occurs scattered among all major groups of angiosperms and a close match to the fossils has not been identified. The pentamerous floral organisation together with structure of stamen, pollen and carpel suggests a phylogenetic position close to the early diverging eudicot lineages, probably in the Ranunculales.
|
|
