Evidence of ecotypic differentiation between populations of the tree species Parapiptadenia rigida due to flooding

Abstract

ABSTRACT. The tree species Parapiptadenia rigida, native to southern South America, is frequently used in reforestation of riverbanks in Brazil. This tree is also a source of gums, tannins and essential oils, and it has some medicinal uses. We investigated flooding tolerance and genetic diversity in two populations of P. rigida; one of them was naturally exposed to flooding. Plants derived from seeds collected from each population were submitted to variable periods of experimental waterlogging and submergence. Waterlogging promoted a decrease in biomass and structural adjustments, such as superficial roots with aerenchyma and hypertrophied lenticels, that contribute to increase atmospheric oxygen intake. Plants that were submerged had an even greater reduction in biomass and a high mortality rate (40%). The two populations varied significantly in their RAPD marker profiles, in their ability to produce aerenchyma when waterlogged and to survive when submerged, suggesting ecotypic differentiation between them. Hence, the seasonal flooding that has been challenging the tropical riparian forest appears to be genetically modifying the P. rigida populations exposed to it by selecting individuals with increased ability to live under this condition.

Genetic diversity and flooding survival in Aegiphila sellowiana (Lamiaceae), a typical tree species from upland riparian forests

“…A mortality rate similar to the one found in A. sellowiana was reported for P. rigida: 40% of the young plants died following flooding stress (Silva et al, 2010). However, P. rigida is not vulnerable to low-intensity waterlogging, where mortality is associated with long periods of a combination of soil flooding and complete submergence of saplings.…”

“…Other species use the low oxygen escape syndrome (Bailey-Serres and Voesenek, 2008), an avoidance strategy that facilitates the survival of submerged organs through the development of anatomical and morphological traits that facilitate inward diffusion of CO 2 and O 2 and reduce the resistance for internal gas diffusion, thereby improving underwater photosynthesis and aerobic metabolism. There are also species that combine those strategies in order to cope with different intensities of flooding (Silva et al, 2010).…”

“…Two tree species from riparian forests in the State of Paraná, Brazil, with distribution in lowland and upland areas were studied before, namely Luehea divaricata (Carvalho et al, 2002) and Parapiptadenia rigida (Silva et al, 2010). The authors aimed to analyze their ability to tolerate flooding by assessing survival rates, growth, and morphological adaptations and to estimate the genetic diversity between flooded and non-flooded populations, in order to find evidence of ecotypic differentiation.…”

Genetic Structure and Diversity of Brazilian Tree Species from Forest Fragments and Riparian Woods

“…In such cases, the observed genetic distance between populations was positively correlated with their geographic distances. This hypothesis could be verified from the combined analysis of two studies conducted with P. rigida, where two nearby populations (Silva et al, 2010) and eight populations distributed over a long geographic scale (Souza et al, 2011) were evaluated. For nearby populations, the Fst value obtained was only 6.2%, whilst the average F ST between the eight populations was 22.8%, and the correlation between genetic and geographic distance was positive and significant.…”

“…Briefly, the results showed that some tree species naturally distributed in this river basin but that do not occur in flooded areas, did not tolerate the stress of artificial flooding; also, there was a great variation in the response of the species from wetlands. In addition to this information, the provenance trials, conducted to compare the performance of populations of the same species from areas periodically flooded and non flooded, showed that for the studied species, Luehea divaricata and Parapiptadenia rigida, the plants that originated from populations naturally flooded were more efficient in responding to waterlooging stress (De Carvalho et al, 2008) or tolerated higher levels of stress, which was not tolerated by the plants of the other provenance (Silva et al, 2010). In a similar study with the tree species Aegiphila sellowiana, used plants regenerated from seeds collected in four regions that presented occasional flooding, showing a variation in the response of individual tolerance to waterlogging.…”