Genetic diversity in Egeria densa and E. najas in Jupiá Reservoir, Brazil

Abstract

Guries. 2012. Genetic diversity in Egeria densa and E. najas in JupiáReservoir, Brazil. Cien. Inv. Agr. 39(2):321-330. The aquatic plant species Egeria densa (Planch.) Casp and E. najas Planchon occur naturally in the Paraná River Basin of southeastern Brazil. Hydroelectric dam construction in the river basin has created several lakes, changing the ecology of the river and altering the population ecology of Egeria. Large, dense populations of Egeria now grow in Jupiá Lake and its tributaries, occasionally blocking hydroelectric turbines. This study is part of a larger project examining environmental changes associated with large dam projects; the research objective of this study was to assess patterns of genetic diversity in Egeria populations growing in Jupiá and Três Irmãos Lakes and their Paraná River tributaries using genetic markers. Forty-two plants of E. najas and 46 of E. densa (for a total of 88 samples) were collected from 13 sites. Genotypes were identified by isoenzymes and Random Amplification of Polymorphic DNA RAPD markers. Using a genetic distance dendrogram we grouped all E. densa plants into one set and all E. najas plants into another set. The plant sample 8a, which presented intermediary morphological characteristics of both species, also presented intermediary genetic characteristics, indicating the possibility that gene introgression between these Egeria species may occur. The creation of Três Irmãos Lake appears to have increased some measures of genetic diversity in Egeria populations by facilitating outcrossing among previously semiisolated genotypes. Increased migration of large numbers of seeds and vegetative branches of E. densa and E. najas into Jupiá Lake and its tributaries can account for most of the changes in patterning of genetic diversity observed in these populations of Egeria.

Invasion of Egeria densa Planch. in semiarid reservoirs

“…This plant forms large monospecific banks with no genetic diversity (Thiébaut et al 2016). Reproduction by seeds is rare, since plants of the same sex are commonly found living in the same environment (Mori et al 2012). E. densa develops well in polluted locations contaminated with heavy metals (Mori et al 2012), has a C4 metabolism (Casati et al 2002), grows in both lotic and lentic environments (Yarrow et al 2009) and survives in a temperature range of 10º to 25 °C, with optimum growth at a temperature of 16 °C (Thiébaut et al 2016).…”