Article
Species replacement along a linear coastal habitat: phylogeography and speciation in the red alga Mazzaella laminarioides along the south east pacific
Registro en:
BMC Evolutionary Biology 12
1471-2148
Autor
Montecinos, Alejandro
Broitman, Bernardo R.
Faugeron, Sylvain
Haye, Pilar A.
Tellier, Florence
Guillemin, Marie-Laure
Resumen
Artículo de publicación ISI Background: The Chilean shoreline, a nearly strait line of coast expanding across 35 latitudinal degrees, represents
an interesting region to assess historical processes using phylogeographic analyses. Stretching along the temperate
section of the East Pacific margin, the region is characterized by intense geologic activity and has experienced
drastic geomorphological transformations linked to eustatic and isostatic changes during the Quaternary. In this
study, we used two molecular markers to evaluate the existence of phylogeographic discontinuities and detect the
genetic footprints of Pleistocene glaciations among Patagonian populations of Mazzaella laminarioides,
a low-dispersal benthic intertidal red seaweed that inhabits along ~3,700 km of the Chilean coastal rocky shore.
Results: Three main genetic lineages were found within M. laminarioides. They are distributed along the Chilean
coast in strict parapatry. The deep divergence among lineages suggests that they could be considered putative
genetic sibling species. Unexpectedly, genetic breaks were not strictly concordant with the biogeographic breaks
described in the region. A Northern lineage was restricted to a broad transition zone located between 30°S and
33°S and showed signals of a recent bottleneck. The reduction of population size could be related to warm events
linked to El Niño Southern Oscillation, which is known to cause massive seaweed mortality in this region. To the
south, we propose that transient habitat discontinuities driven by episodic tectonic uplifting of the shoreline
around the Arauco region (37°S-38°S); one of the most active forearc-basins in the South East Pacific; could be at
the origin of the Central/South genetic break. The large beaches, located around 38°S, are likely to contribute to the
lineages’ integrity by limiting present gene flow. Finally, the Southern lineage, occupies an area affected by
ice-cover during the last glaciations. Phylogeny suggested it is a derived clade and demographic analyses showed
the lineage has a typical signature of postglacial recolonization from a northern glacial refugium area.
Conclusions: Even if environmental adaptation could have strengthened divergence among lineages in
M. laminarioides, low dispersal capacity and small population size are sufficient to generate phylogeographic
discontinuities determined by genetic drift alone. Interestingly, our results confirm that seaweed population
connectivity over large geographic scales does not rely only on dispersal capacity but also seem to depend highly
on substratum availability and population density of the receiving locality