Geological and climatic changes in quaternary shaped the evolutionary history of Calibrachoa heterophylla, an endemic South-Atlantic species of petunia

Abstract

BackgroundThe glacial and interglacial cycles that characterized the Quaternary greatly affected the distribution and genetic diversity of plants. In the Neotropics, few phylogeographic studies have focused on coastal species outside of the Atlantic Rainforest. Climatic and sea level changes during the Quaternary played an important role in the evolutionary history of many organisms found in coastal regions. To contribute to a better understanding of plant evolution in this environment in Southern South America, we focused on Calibrachoa heterophylla (Solanaceae), an endemic and vulnerable wild petunia species from the South Atlantic Coastal Plain (SACP).ResultsWe assessed DNA sequences from two cpDNA intergenic spacers and analyzed them using a phylogeographic approach. The present phylogeographic study reveals the influence of complex geologic and climatic events on patterns of genetic diversification. The results indicate that C. heterophylla originated inland and subsequently colonized the SACP; the data show that the inland haplogroup is more ancient than the coastal one and that the inland was not affected by sea level changes in the Quaternary. The major diversification of C. heterophylla that occurred after 0.4 Myr was linked to sea level oscillations in the Quaternary, and any diversification that occurred before this time was obscured by marine transgressions that occurred before the coastal sand barrier’s formation. Results of the Bayesian skyline plot showed a recent population expansion detected in C. heterophylla seems to be related to an increase in temperature and humidity that occurred at the beginning of the Holocene.ConclusionsThe geographic clades have been formed when the coastal plain was deeply dissected by paleochannels and these correlate very well with the distributional limits of the clades. The four major sea transgressions formed a series of four sand barriers parallel to the coast that progressively increased the availability of coastal areas after the regressions and that may have promoted the geographic structuring of genetic diversity observed today. The recent population expansion for the entire species may be linked with the event of marine regression after the most recent sea transgression at ~5 kya.

Diversification in the South American Pampas: the genetic and morphological variation of the widespread Petunia axillaris complex (Solanaceae)

“…) and one lowland species from the sister species Calibrachoa (Mäder et al . ). Interestingly, both of the latter studies also estimated N e s to be approximately 1E 6 , and these are large numbers as expected for herbaceous species with large distributions.…”

“…A similar pattern of population increase following the end of the LGM was found in Calibrachoa heterophylla , a species that is also distributed (although much more restricted) in the eastern lowlands of the Pampas, a region that was much affected by the increase in temperature and humidity at the beginning of the Holocene (Mäder et al . ).…”

Phylogeography of thePetunia integrifoliacomplex in southern Brazil

“…If the individuals belonging to the mainland and coastal lineages have ecologically differentiated genotypes adapted for low and high salinity, respectively, they may not be able to establish themselves outside their environment of origin, as initially described by Linhart & Grant () for many other plant species. This low flexibility to adapt to different environments has been described for another plant species (Mäder et al ., ) and animals (Lopes & Freitas, ) occurring in the same region (comparing South Atlantic Coastal Plain and the countryside in south Brazil). Therefore, the coastal haplogroup could be considered as a biogeographical island, as proposed by other authors for different regions, such as the tropical Andean mountains (Särkinen et al ., , ).…”

Effects of past climate onPassiflora actinia(Passifloraceae) populations and insights into future species management in the Brazilian Atlantic forest

“…The current geographical distribution of animal and plant species along the Brazilian coast was highly influenced by climatic oscillations in the Quaternary, particularly by the direct and indirect effects of sea‐evel changes that occurred during this period (Villwock et al ., ; Mäder et al ., ). These processes substantially affected the Atlantic Forest over the past 20 000 years and resulted in periods of expansion and contraction that may have led to fragmentation (Werneck, Costa & Colli, ).…”