Browsing by Author "Stech, Michael"
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- Climate-driven vicariance and long-distance dispersal explain the Rand Flora pattern in the liverwort Exormotheca pustulosa (Marchantiophyta)Publication . Rodrigues, Ana S. B.; Martins, Anabela; Garcia, César Augusto; Sérgio, Cecília; Porley, Ron; Fontinha, Susana; González-Mancebo, Juana M.; Gabriel, Rosalina; Phephu, Nonkululo; Van Roy, Jacques; Dirkse, Gerard; Long, David; Stech, Michael; Patiño, Jairo; Sim-Sim, ManuelaThe ‘Rand flora’ is a biogeographical disjunction which refers to plant lineages occurring at the margins of the African continent and neighbouring oceanic archipelagos. Here, we tested whether the phylogeographical pattern of Exormotheca pustulosa Mitt. was the result of vicariance induced by past climatic changes or the outcome of a series of recent long-distance dispersal events. Two chloroplast markers (rps4-trnF region and psbA-trnH spacer) and one nuclear marker (ITS2) were analysed. Phylogenetic and phylogeographical relationships were inferred as well as divergence time estimates and ancestral areas. Exormotheca possibly originated in Eastern Africa during the Late Oligocene/Early Miocene while Exormotheca putulosa diversified during the Late Miocene. Three main E. pustulosa groups were found: the northern Macaronesia/Western Mediterranean, the South Africa/Saint Helena and the Cape Verde groups. The major splits among these groups occurred during the Late Miocene/Pliocene; diversification was recent, dating back to the Pleistocene. Climate-driven vicariance and subsequent long-distance dispersal events may have shaped the current disjunct distribution of E. pustulosa that corresponds to the Rand Flora pattern. Colonization of Macaronesia seems to have occurred twice by two independent lineages. The evolutionary history of E. pustulosa populations of Cape Verde warrants further study.
- Explaining the «anomalous» distribution of Echinodium Jur. (Bryopsida) : independent evolution in Macaronesia and AustralasiaPublication . Stech, Michael; Sim-Sim, Manuela; Esquível, M. Glória; Fontinha, Susana; Tangney, Ray; Lobo, Carlos; Gabriel, Rosalina; Quandt, DietmarThe peculiar disjunction between Macaronesia and Australasia of the morphologically isolated pleurocarpous moss genus Echinodium is one of the most prominent questions in bryology. Echinodium as traditionally circumscribed comprises six extant species, four restricted to the Macaronesian archipelagos and two confined to the Australasian/Pacific regions. Molecular phylogenetic analyses based on plastid trnLUAA intron and nuclear ribosomal ITS sequences indicate that Echinodium is polyphyletic and split into three groups. Three of the four Macaronesian species (E. spinosum and the single island endemics E. renauldii and E. setigerum) are closely related to each other and treated as Echinodium s.str. (Echinodiaceae). Further clarification of the relationships of Echinodium s.str. with Orthostichella, a segregate of Lembophyllaceae, is needed. The remaining Macaronesian species, E. prolixum, is transferred to Isothecium (Lembophyllaceae); this systematic position is also strongly supported by leaf characters. The two Australasian species, E. hispidum and E. umbrosum, are molecularly unrelated to the Macaronesian species and are transferred to Thamnobryum in the Neckeraceae. While the molecular data suggest that the peculiar distribution pattern of ‘Echinodium’ is an artefact, the striking morphological similarity observed in Macaronesian and Australasian species cannot be dismissed. Possible explanations are: (i) parallel morphological evolution of the ‘Echinodium habit’ in Macaronesia and Australasia, or (ii) retention of a set of plesiomorphic characters in non-related groups in relict habitats, the Macaronesian laurel forest and the austral temperate rain forests, respectively. Of these hypotheses, the evolutionary parallelism hypothesis seems more plausible for several reasons, which are discussed.
- Patterns of intraspecific genetic variation of Andoa berthelotiana (Myuriaceae, Bryophyta) in the Azores (Macaronesia)Publication . Matins, Soraia; SIM-SIM, Manuela; Gabriel, Rosalina; Stech, MichaelMacaronesia is home to several endemic bryophytes, such as Andoa berthelotiana. Recent genetic studies revealed the existence of two intraspecific lineages within this species, one in Madeira and the Canary Islands and another in the Azores. However, patterns of intraspecific variation within archipelagos, remain a relatively unexplored area of research. In this study we investigate patterns of intraspecific variation of Andoa berthelotiana within the Azorean archipelago and potential associations with elevation. Our investigation is based on the analysis of chloroplast DNA sequences and AFLP data. The dataset includes trnL-trnF sequences from 23 samples and AFLP data from 34 samples collected in seven of the nine Azorean islands, encompassing elevations of up to 1200 m. For the DNA sequence data haplotype diversity, nucleotide diversity and a statistical parsimony haplotype network were calculated. The AFLP data were analyzed by AMOVA (Analysis of Molecular Variance) and PCoA (Principal Coordinates Analysis). A Chi-Square test was carried out to assess the significance of the relationship between elevation and AFLP groups or trnL-trnF haplotypes, respectively. The observed intraspecific genetic variation clustered into three trnL-trnF haplotypes and two AFLP groups, without a clear geographical structure across the Azorean archipelago. Group AFLP1 and haplotypes trnL_F1 and trnL_F3 only appeared below 600 m elevation, where low-elevation vegetation (coastal woodlands, lowland forests and montane Laurus azorica forests) prevails, while group AFLP2 and haplotype trnL_F2 occurring along the whole elevational range, but with most samples above 600 m. Associations between elevation and molecular groups were significant according to the Chi- Square test. Our study reveals the presence of genetic variation within Andoa berthelotiana in the Azorean archipelago. The two main genetic groups do not seem to be related to geographical location of islands nor groups of islands, but rather to elevation. One group exhibits a broader ecological amplitude, whereas the other may be genetically adapted to environmental conditions at lower elevations (below 600 m), which includes the area where the native laurel forests dominate and where anthropogenic activities have altered the majority of natural vegetation. Conservation efforts should therefore not only consider the species Andoa berthelotiana itself, which is associated with natural forest, but also intraspecific genetic diversity of Andoa populations, in particular genotypes restricted to lower elevations.