Reconsidering the conservation of an endangered tree in Brazil: one species or a hybrid?

Have you ever gone for a walk and noticed that the landscape has changed? Changes in plant species are easy to spot between, for example, a meadow and a forest. The transition area of biomes is called an ecotone which provides a natural laboratory for scientists for studying plant adaptations and evolution. 

Muniz and colleagues from Universidade Federal de Minas Gerais (Brazil) used genetic methods to reveal that a critically endangered tree in an ecotone is actually a hybrid between two other species from different habitats. Whilst a comprehensive National Action Plan was launched in 2014 (Spanish) to conserve and restore the endangered tree, this research suggests that the management strategy needs to be reconsidered. 

Dimorphandra wilsonii, known as Faveiro-de-Wilson, is a Critically Endangered tree which can only be found in Brazil in an area of 5,000 km². The tree can reach 17 m in height and 1.2 m in diameter, it has small yellow flowers and produces pods of reddish-brown beans. The tree belongs to the legume family (Fabaceae) and it is exploited by the pharmaceutical industry as it produces high levels of rutin, an antioxidant. 

The Cerradão is most biodiverse savanna in the world whilst the Atlantic Forest is one of the most diverse and threatened tropical forests. D. wilsonii is mainly found in the ecotone in between the two biomes while D. mollis grows in Cerradão and D. exaltata can be found in the Atlantic Forest. Initially, scientists aimed to sample these three tree species from different habitats to help the conservation of D. wilsonii.

The scientists sampled a total of 152 trees from ten municipalities of central Minas Gerais state, southeastern Brazil. The genetic diversity, structure and heterozygosity were analysed from DNA sequencing using 11 simple sequence repeat (SSR) markers.

Genetic analysis revealed that 73% of D. wilsonii individuals were likely the F1 descendants of D. mollis and D. exaltata. Further analysis found that D. wilsonii was diploid, had the same chromosome number and allelic richness as D. mollis. 

Muniz and colleagues explain, “Our study offers insights about the evolutionary origin of D. wilsonii and increases our understanding of the evolutionary processes that contribute to the high biodiversity of the Cerrado and the Brazilian Atlantic Forest. It also provides useful information for the conservation and management of Dimorphandra taxa that are facing habitat loss, fragmentation and climate change.”

Hybridisation has led to the extinction of many species directly and indirectly and so, conservation of hybrids alone is not a good strategy. As D. exaltata is a more threatened species, it might be receiving some genetic diversity from backcrossing with D. wilsonii. The leading scientists have previously analysed the genetic diversity of herbarium specimens of D. exaltata and concluded in the journal Scientific Reports that it is highly at risk of extinction due to lack of diversity. 

The research team concludes, “This study highlights the value of genetic information for the design of conservation strategies”.

The article is available through Researchgate as well.