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Seminarios científicos en el Real Jardín Botánico, CSIC, el día 8 de abril de 2011 Friday, 08 de April de 2011 | Unidad de Cultura Científica

Programa Synthesys

Título 1: "Hidding for surviving: comparative phylogeography in European bryophytes" por Aurélie abstract

Resumen:


Bryophytes are a paraphyletic assemblage of land plants sharing a common ancestor with tracheophytes. Their ancient origin, coupled with a vicariancist interpretation of their strikingly disjunct distributions, have led to the traditional perception of bryophytes as ‘sphinxes of the past’. Mounting evidence from molecular dating, ecological modelling, and population genetics, conversely, indicates that recent, wind-driven asymmetrical dispersal predominantly shapes current bryophyte distributions.

The substantial role of dispersal in bryophyte distributions challenges key biogeographic hypotheses and in particular, the notion that islands are ‘the end of the colonization road’.
Given that the climate of oceanic islands would have been buffered by their geographic location, it is possible that taxa may have persisted in the islands during glacial periods and that the archipelagos may have served as a source for the post-glacial colonization of continental areas.
We aim to test the significance of Macaronesia as a source for the post-glacial recolonization of Europe based on two complementary approaches. In a first instance, we will use ecological niche models and paleoclimatic data to infer past species’ distributions. This approach will be complemented by molecular phylogeography to determine whether the potential refugia identified by niche modeling indeed are consistent with the current patterns of genetic diversity and structure. In particular, we aim at testing the hypothesis that Macaronesian populations hold much of the genetic variation and served as sources from which the European continent was subsequently recolonized.


Título 2: "Significance of the mating system in the dispersal ability at different nested spatial scales: Insights from the European bryoflora" por Benjamin Laenen

Resumen:


For more than two centuries, the diversity of plant mating systems has captured the curiosity and imagination of biologists and stimulated fruitful research by both ecologists and population geneticists. In angiosperms, only 6% of the species are dioecious, but their scattered taxonomic position within the group suggests that shifts in mating systems occurred independently multiple times. Dioecious species may benefit from reduced inbreeding depression, but since only females produce seeds, dioecious females must produce more or better seeds than their hermaphrodite counterparts and/or disperse those seeds to an equivalent number of suitable sites to ensure an equivalent number of progeny. In early-diverging land plants like bryophytes, where sexual reproduction depends on sperms swimming to eggs via free water, separation of sexes can present serious problems for successful sexual fusion. Fertilization requires that sperm swim to the archegonia, a process that is greatly limited by the distance between male and female plants. Dioecious species therefore often fail to reproduce sexually. For instance, 87% of the species wherein sporophytes are unknown in the UK, are dioecious, whereas sporophytes are regarded as occasional to common in 83% of the monoecious species.

Despite this, about 70% of liverworts and 60% of mosses are dioecious. In fact, asexual reproduction is of utmost importance in bryophytes and may compensate for the limited ability of spore dispersal at the local scale. Spores and asexual gemmae display, however, contrasting tolerances to UV radiation, desiccation, and frost, which prevail in high altitude air currents, and hence, play different roles i.e., routine short-distance dispersal via gemmae and random long-distance dispersal by spores. Since most bryophyte species are wind-dispersed, differences in mating systems may directly impact on long-distance dispersal, gene flow, and hence, isolation and speciation.

 

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