Browsing by Author "Sequeira, Miguel"
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- Biologia, paisagem e diversidadePublication . Sequeira, Miguel
- Divergence and biogeography of the recently evolved Macaronesian red Festuca (Gramineae) species inferred from coalescence-based analysesPublication . Diáz-Pérez, A. J.; Sequeira, Miguel; Santos-Guerra, A.; Catalán, P.Studying the biogeography and the phylogeography of the endemic Macaronesian red Festuca species (Loliinae, Poaceae) is of prime interest in understanding the speciation and colonization patterns of recently evolved groups in oceanic archipelagos. Coales cence-based analyses of plastid trnLF sequences were employed to estimate evolutionary parameters and to test different species-history scenarios that model the pattern of species divergence. Bayesian IM estimates of species divergence times suggested that ancestral lineages of diploid Macaronesian and Iberian red fescues could have diverged between 1.2 and 1.57 Ma. When empirical data were compared to coalescence-based simulated distributions of discordance and p-distance statistics, two species-history models were chosen in which the first branching lineage derived in Canarian Festuca agustinii. Its sister lineage could have involved a recent polytomy leading to the Madeiran Festuca jubata, the Azorean Festuca francoi + Festuca petraea and the continental Festuca rivularis lineages (Canarian model) or the sequential branching of lineages leading to F. jubata and finally to the sister clades of F. rivularis and F. francoi + F. petraea (Sequential model). Nested clade phylogeographic analysis (NCPA) and a first adapted host–parasite co-evolutionary ParaFit method were used to detect the phylogeographic signal. NCPA inferred long-distance colonizations for the entire diploid red Festuca complex, but allopatric-fragmentation and isolation by-distance (IBD) patterns were inferred within archipelagos. In addition, the ParaFit method suggested a generalized pattern of a stepping-stone model at all hierarchical levels. Maximum-likelihood-based dispersal-extinction-cladogenesis (DEC) models were superimposed on the Sequential model species tree. The three-independent-colonization (3IC) model was the best supported biogeographic scenario, concurring with previous analysis based on multilocus AFLP data.
- Multiple colonizations, in situ speciation, and volcanism-associated stepping-stone dispersals shaped the phylogeography of the Macaronesian red fescues (Festuca L., Gramineae)Publication . Díaz-Pérez, Antonio; Sequeira, Miguel; Santos-Guerra, Arnoldo; Catalán, PilarWhereas examples of insular speciation within the endemic-rich Macaronesian hotspot flora have been documented, the phylogeography of recently evolved plants in the region has received little attention. The Macaronesian red fescues constitute a narrow and recent radiation of four closely related diploid species distributed in the Canary Islands (F. agustinii), Madeira (F. jubata), and the Azores (F. francoi and F. petraea), with a single extant relative distributed in mainland southwest Europe (F. rivularis). Bayesian structure and priority consensus tree approaches and population spatial correla tions between genetic, geographical, and dispersal distances were used to elucidate the phylogeographical patterns of these grasses. Independent versus related origins and dispersal versus isolation by distance (IBD) hypotheses were tested to explain the genetic differentiation of species and populations, respectively. Genetic structure was found to be geographi cally distributed among the archipelagos and the islands endemics. The high number of shared AFLP fragments in all four species suggests a recent single origin from a continental Pliocene ancestor. However, the strong allelic structure detected among the Canarian, Madeiran, and Azorean endemics and the significant standardized residual values obtained from structured Bayesian analysis for pairwise related origin hypotheses strongly supported the existence of three independent continental-oceanic colonization events. The Canarian F. agustinii, the Madeiran F. jubata, and the two sister F. francoi and F. petraea Azorean species likely evolved from different continental founders in their respective archipelagos. Despite the short span of time elapsed since colonization, the two sympatric Azorean species probably diverged in situ, following eco logical adaptation, from a common ancestor that arrived from the near mainland. Simple dispersal hypotheses explained most of the genetic variation at the species level better than IBD models. The optimal dispersal model for F. agustinii was a bidirectional centripetal stepping-stone colonization pattern, an eastern-to-western volcanism-associated dispersion was fa vored for F. francoi, whereas for the recently derived F. petraea a counterintuitive direction of colonization (west-to-east) was suggested. The population-based phylogeographical trends deduced from our study could be used as predictive models for other Macaronesian plant endemics with similar distribution areas and dispersal abilities. [Bayesian genetic analyses; colonization of oceanic islands; dispersal models; Festuca sect. Aulaxyper; Macaronesia; phylogeography.]
- On a coal specimen possibly associated with the classical Mio-Pleistocene São Jorge leaf bed site, Madeira Island, PortugalPublication . Marques, Carlos A. Góis; Correia, Pedro; Sequeira, Miguel Menezes de; Góis-Marques, Carlos A.; Sequeira, MiguelDue to the unusual presence of coal seams within a volcanic island, the São Jorge lignite, located in the north side of Madeira Island, was since the early 19th century a magnet for naturalists. In 1854 the site was visited by Sir Charles Lyell and Georg Hartung, where both discovered a leaf-bed associated with the lignite. This finding pro vided key proofs to Lyell's uniformitarian theory of the formation of volcanic islands and the long-term existence of laurel forests in Macaronesia. Despite its historical importance, lignite specimens from São Jorge remain unknown to date. Recently, the study of Funchal Natural History Museum (MMF, Madeira Island, Portugal) collections revealed a coal specimen associated with the classical site of São Jorge. Here we provide a critical anal ysis of this specimen using historical and palaeobotanical approaches. We show that this coal is not a lignite from São Jorge and that it was not collected in ca. 1905. Historically, the São Jorge site was covered by a landslide until 1917, making it inaccessible. Furthermore, the coal is either a bituminous coal or anthracite and contains typical rhizomorph fossils of extinct Lycophytes known as Stigmaria ficoides (Sternb.) Brongn., as already indicated in the old MMF record books. The coal is most likely a late Carboniferous (Pennsylvanian, 323.4–298.9 Ma) specimen from the early 20th century British coaling industry on Madeira Island, imported from the UK, which, at some point, was erroneously labelled as originating from the 7–1.8 Ma São Jorge outcrop in Madeira.
- Trees as habitat islands: temporal variation in alpha and beta diversity in epiphytic laurel forest bryophyte communitiesPublication . Patiño, Jairo; Gómez-Rodríguez, Carola; Pupo-Correia, Aida; Sequeira, Miguel; Vanderpoorten, AlainAim: Trees represent striking examples of habitat islands, with various degrees of spatial isolation and evolving properties during their life cycle. Here, we investigate whether changes in habitat conditions, dispersal limitations or competition cause variation in patterns of epiphytic species richness and turnover. Location: Madeira island. Taxon: Bryophytes. Methods: Using linear mixed effect models, we test whether species richness exhi bits a monotonic or hump-shaped relationship with time. Two groups of host-tree species, late- and early-successional, were considered. We further identify the mechanisms explaining the observed variation in species composition by dividing beta diversity into its nestedness (bsne) and turnover (bsim) components and correlat ing them with tree age and geographical distance among trees. Results: The best-fit models all included tree age (T), but its quadratic term (T2 ) and tree height (H, here a surrogate of area) were not systematically included. bsim, but not bsne, correlated with host-tree age, and both bsim and bsne correlated with geo graphical distance. Main conclusions: Tree age was consistently included in all of the best-fit models, reflecting the progressive increase in epiphyte bryophyte species richness through time. The limited contribution of T2 and H to the best models suggests that compe tition for space is not a key factor on mature trees. The correlation of bsim, but not bsne, with host-tree age, and of bsim and bsne with distance among trees, suggests that variation in species composition is caused by (1) temporal community shifts due to allogenic drivers and (2) dispersal limitations, which are reflected by the higher similarity of the epiphyte communities on clustered trees rather than by an increasing probability of colonization with tree age. Since actual ancient laurel for ests may no longer exist in Madeira, the conservation of clusters of late-succes sional trees, enhancing connectivity at small spatial scales, is of utmost importance for the conservation and recovery of the unique laurel forest epiphytic flora.