| 1. |
- Dyer, Adrian G, et al.
(författare)
-
Parallel evolution of angiosperm colour signals : common evolutionary pressures linked to hymenopteran vision.
- 2012
-
Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 279:1742, s. 3606-15
-
Tidskriftsartikel (refereegranskat)abstract
- Flowering plants in Australia have been geographically isolated for more than 34 million years. In the Northern Hemisphere, previous work has revealed a close fit between the optimal discrimination capabilities of hymenopteran pollinators and the flower colours that have most frequently evolved. We collected spectral data from 111 Australian native flowers and tested signal appearance considering the colour discrimination capabilities of potentially important pollinators. The highest frequency of flower reflectance curves is consistent with data reported for the Northern Hemisphere. The subsequent mapping of Australian flower reflectances into a bee colour space reveals a very similar distribution of flower colour evolution to the Northern Hemisphere. Thus, flowering plants in Australia are likely to have independently evolved spectral signals that maximize colour discrimination by hymenoptera. Moreover, we found that the degree of variability in flower coloration for particular angiosperm species matched the range of reflectance colours that can only be discriminated by bees that have experienced differential conditioning. This observation suggests a requirement for plasticity in the nervous systems of pollinators to allow generalization of flowers of the same species while overcoming the possible presence of non-rewarding flower mimics.
|
|
| 2. |
- Peyrot, Daniel, et al.
(författare)
-
The greening of Western Australian landscapes: the Phanerozoic plant record
- 2019
-
Ingår i: Journal of the Royal Society of Western Australia. - Perth : Royal Society of Western Australia. - 0035-922X. ; 102, s. 52-82
-
Tidskriftsartikel (refereegranskat)abstract
- Western Australian terrestrial floras first appeared in the Middle Ordovician (c. 460 Ma) and developed Gondwanan affinities in the Permian. During the Mesozoic, these floras transitioned to acquire a distinctly austral character in response to further changes in the continent’s palaeolatitude and its increasing isolation from other parts of Gondwana. This synthesis of landscape evolution is based on palaeobotanical and palynological evidence mostly assembled during the last 60 years. The composition of the plant communities and the structure of vegetation changed markedly through the Phanerozoic. The Middle Ordovician –Middle Devonian was characterised by diminutive vegetation in low-diversity communities. An increase in plant size is inferred from the Devonian record, particularly from that of the Late Devonian when a significant part of the flora was arborescent. Changes in plant growth-forms accompanied a major expansion of vegetation cover to episodically or permanently flooded lowland settings and, from the latest Mississippian onwards, to dry hinterland environments. Wetter conditions during the Permian yielded waterlogged environments with complex swamp communities dominated by Glossopteris. In response to the Permian–Triassic extinction event, a transitional vegetation characterised by herbaceous lycopsids became dominant but was largely replaced by the Middle Triassic with seed ferns and shrubs or trees attributed to Dicroidium. Another floristic turnover at the Triassic–Jurassic boundary introduced precursors of Australia’s modern vegetation and other southern hemisphere regions. Most importantly, flowering plants gained ascendancy during the Late Cretaceous. Characteristics of the state’s modern vegetation, such as sclerophylly and xeromorphy, arose during the Late Cretaceous and Paleogene. The vegetation progressively developed its present-day structure and composition in response to the increasing aridity during the Neogene–Quaternary.
|
|
| 3. |
- Merle, Renaud E., 1976-, et al.
(författare)
-
Cretaceous seamounts along the continent–ocean transition of the Iberian margin : U–Pb ages and Pb–Sr–Hf isotopes
- 2006
-
Ingår i: Geochimica et Cosmochimica Acta. - 0016-7037 .- 1872-9533. ; 70:19, s. 4950-4976
-
Tidskriftsartikel (refereegranskat)abstract
- To elucidate the age and origin of seamounts in the eastern North Atlantic, 54 titanite and 10 zircon fractions were dated by the U–Pb chronometer, and initial Pb, Sr, and Hf isotope ratios were measured in feldspars and zircon, respectively. Rocks analyzed are essentially trachy-andesites and trachytes dredged during the “Tore Madeira” cruise of the Atalante in 2001. The ages reveal different pulses of alkaline magmatism occurring at 104.4±1.4 (2σ) Ma and 102.8±0.7 Ma on the Sponge Bob seamount, at 96.3±1.0 Ma on Ashton seamount, at 92.3±3.8 Ma on the Gago Coutinho seamount, at 89.3±2.3 Ma and 86.5±3.4 Ma on the Jo Sister volcanic complex, and at 88.3±3.3 Ma, 88.2±3.9, and 80.5±0.9 Ma on the Tore locality. No space–time correlation is observed for alkaline volcanism in the northern section of the Tore-Madeira Rise, which occurred 20–30 m.y. after opening of the eastern North Atlantic. Initial isotope signatures are: 19.139–19.620 for 206Pb/204Pb, 15.544–15.828 for 207Pb/204Pb, 38.750–39.936 for 208Pb/204Pb, 0.70231–0.70340 for 87Sr/86Sr, and +6.9 to +12.9 for initial epsilon Hf. These signatures are different from Atlantic MORB, the Madeira Archipelago and the Azores, but they lie in the field of worldwide OIB. The Cretaceous seamounts therefore seem to be generated by melts from a OIB-type source that interact with continental lithospheric mantle lying formerly beneath Iberia and presently within the ocean–continent transition zone. Inheritance in zircon and high 207Pb of initial Pb substantiate the presence of very minor amounts of continental material in the lithospheric mantle. A long-lived thermal anomaly is the most plausible explanation for alkaline magmatism since 104 Ma and it could well be that the same anomaly is still the driving force for tertiary and quaternary alkaline magmatism in the eastern North Atlantic region. This hypothesis is agreement with the plate-tectonic position of the region since Cretaceous time, including an about 30° anti-clockwise rotation of Iberia.
|
|
