Is there a relationship between polyploidy and stressful environments? A case study of inselbergs in northeastern Brazil

Abstract

ABSTRACT. The aim of this study was to examine the hypothesis that plants with higher ploidy levels are selected by environments under more extremely stressful conditions than the same (or closely related) species from less rigorous terrestrial or epiphytic habitats. Therefore, we analyzed the chromosome numbers of 26 species belonging to 21 genera and 13 families of angiosperms that were collected on 4 inselbergs in Paraiba State, northeastern Brazil. In addition, 13 rupicolous species that grow in the study area, whose chromosome numbers were previously determined, were included in our analysis. Plant chromosome numbers varied between 2n = 12 in Callisia filiformis (Commelinaceae) to 2n = ca. 240 in Epidendrum cinnabarinum (Orchidaceae). The data as a whole do not support the hypothesis that inselberg species have greater levels of ploidy than terrestrial or epiphytic populations of the same or closely related S.R. Pitrez et al. ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 13 (4): 8353-8366 (2014) 8354species because these rupicolous species demonstrate chromosomal evolution patterns that are independent of the stressful environments of inselberg formations.

Como a variação no número cromossômico pode indicar relações evolutivas entre a Caatinga, o Cerrado e a Mata Atlântica?

“…Although the polyploidy proportions that we found are smaller, our results agree with the conclusion of that polyploidy is less frequent in tropical regions. Other studies have come to similar conclusions (Martin and Husband 2009;Glennon et al 2014;Pitrez et al 2014;Visser and Molofsky 2015).…”

“…Several studies have compared the frequency of polyploids in natural angiosperm communities across environmental stress gradients in Europe (Löve 1953), North America Martin and Husband 2009), Artic (Brochmann et al 2004), inselbergs in northeastern Brazil (Pitrez et al 2014), and the world flora . and Brochmann et al (2004) have observed that polyploids were more frequent in harsh environments.…”

“…and Brochmann et al (2004) have observed that polyploids were more frequent in harsh environments. On the other hand, Löve (1953), Martin and Husband (2009), Glennon et al (2014) and Pitrez et al (2014) 2014). Although the concepts are clearly defined, differentiating between both processes is very hard.…”

“…Essa hipótese foi confirmada por Johnson e Packer (1965), que observaram um aumento na frequência da poliploidia em angiospermas no noroeste do Alasca em gradientes edáficos e, posteriormente, por Brochmann et al (2004), que notaram que o nível de poliploidia aumenta fortemente em direção ao norte no Ártico. Mas essa hipótese foi refutada por Löve (1953), que analisou a frequência da poliploidia na flora da Islândia, por Martin e Husband (2009), que analisaram espécies de 144 gêneros de angiospermas norte-americanas, por Glennon et al (2014), ao compararem o nicho climático de poliploides e diploides na América do Norte, e por Pitrez et al (2014), ao compararem a proporção de poliploides e diploides de espécies que ocorrem em inselbergs no nordeste brasileiro. Em uma análise da distribuição de poliploides em nível global, observaram que a frequência da poliploidia aumenta em direção a altas latitudes devido, principalmente, ao aumento de ervas perenes, que apresentam maior proporção de poliploides.…”

IAPT chromosome data 28

“…Apocynaceae is a globally distributed family consisting of about 400 genera and 5000 species (Endress & al., 2007). In Brazil, about 750 species occur in different kinds of habitat, including inselbergs (Rapini, 2012;Pitrez & al., 2014a). The family is characterized by a remarkable diversity in chromosome numbers, ranging from 2n = 10 in Rhabdadenia madida (Vell.)…”