Publicação
The Quaternary palaeobotany of Madeira and Azores volcanic archipelagos (Portugal) : insights into the past diversity, ecology, biogeography and evolution
| Resumo: | Palaeobotanical research on oceanic islands has been largely ignored despite its importance to provide empirical proofs to disentangle insular plant diversity, evolution, ecology and biogeography. Here we use the oceanic archipelagos of Madeira and Azores as a ‘testing ground’, via fieldwork, laboratorial and collection-based research, to demonstrate the existence of well-preserved and palaeobiological informative plant fossils. In Madeira Island, mid-19th century collections from São Jorge leaf bed were stratigraphically and taxonomically reappraised revealing the presence of the stink-laurel forest at 7-1.8 Ma, similar to the extant community. Porto da Cruz sediments exploration and new 40Ar-39Ar dating revealed of the existence at 1.3 Ma of the extinct Eurya stigmosa (Theaceae), the neoendemic Melanoselinum decipiens (Apiaceae) and the probable ancestor of the Madeiran besom heath, Erica scoparia (Ericaceae). Preliminary prospection and dating of limnic sediments revealed the presence of a suitable Pleisto-Holocene palynological content for palaeoecological reconstruction. In Azores archipelago, the historical fossil collection and palaeobotanical review, revealed the existence of plant fossils on all islands. On Faial Island, charcoalified wood found within the 1200 yr BP ignimbrite revealed the presence of abundant Prunus lusitanica subsp. azorica, today a rare endemic tree due to anthropic impacts. Fanal Bay leaf-beds (Terceira Island), were prospected during 2016, revealing an in-situ leaf litter forest, but these were destroyed in 2018, despite being within the Azores Geopark. Here I demonstrate, for both archipelagos, the presence of an abundant and well-preserved plant fossil record, ranging probably from the Miocene, but mostly Pleistocene to the Holocene. These plant fossils are valuable, as they provide minimum ages for future phylogeny calibration, clues on the evolution of insular syndromes and allow the inference of the anthropic impact on pristine insular vegetation. However, this information can only be retrieved if the palaeobotanical geoheritage in these archipelagos are protected and properly studied. |
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| Autores principais: | Góis-Marques, Carlos A. |
| Assunto: | Quaternário ilhas oceânicas Macaronesia fósseis de plantas paleobiologia Quaternary Oceanic island plant fossil palaeobiology |
| Ano: | 2021 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | Palaeobotanical research on oceanic islands has been largely ignored despite its importance to provide empirical proofs to disentangle insular plant diversity, evolution, ecology and biogeography. Here we use the oceanic archipelagos of Madeira and Azores as a ‘testing ground’, via fieldwork, laboratorial and collection-based research, to demonstrate the existence of well-preserved and palaeobiological informative plant fossils. In Madeira Island, mid-19th century collections from São Jorge leaf bed were stratigraphically and taxonomically reappraised revealing the presence of the stink-laurel forest at 7-1.8 Ma, similar to the extant community. Porto da Cruz sediments exploration and new 40Ar-39Ar dating revealed of the existence at 1.3 Ma of the extinct Eurya stigmosa (Theaceae), the neoendemic Melanoselinum decipiens (Apiaceae) and the probable ancestor of the Madeiran besom heath, Erica scoparia (Ericaceae). Preliminary prospection and dating of limnic sediments revealed the presence of a suitable Pleisto-Holocene palynological content for palaeoecological reconstruction. In Azores archipelago, the historical fossil collection and palaeobotanical review, revealed the existence of plant fossils on all islands. On Faial Island, charcoalified wood found within the 1200 yr BP ignimbrite revealed the presence of abundant Prunus lusitanica subsp. azorica, today a rare endemic tree due to anthropic impacts. Fanal Bay leaf-beds (Terceira Island), were prospected during 2016, revealing an in-situ leaf litter forest, but these were destroyed in 2018, despite being within the Azores Geopark. Here I demonstrate, for both archipelagos, the presence of an abundant and well-preserved plant fossil record, ranging probably from the Miocene, but mostly Pleistocene to the Holocene. These plant fossils are valuable, as they provide minimum ages for future phylogeny calibration, clues on the evolution of insular syndromes and allow the inference of the anthropic impact on pristine insular vegetation. However, this information can only be retrieved if the palaeobotanical geoheritage in these archipelagos are protected and properly studied. |
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