How hidden is the diversity of the genus Cosmarium (Desmidiaceae) in the Brazilian Caatinga?

Abstract

The Caatinga domain is the largest and most diverse tropical semiarid ecoregion of South America; however, little is known about the diversity of desmids it harbors, especially the genus Cosmarium (Desmidiaceae, Zygnematophyceae). Our study contributes to the knowledge of Cosmarium in the Caatinga through the report of 42 interesting taxa, including a new species (Cosmarium imperiale), 22 new records for South America, and 19 additions to the desmid flora from Brazil. The samples were gathered from periphytic material from the "Pantanal dos Marimbus" in the Chapada Diamantina region of Northeast Brazil. We provide taxonomic notes, ecological information, including habitat conditions with limnological data, and updated global distributions for all taxa of Cosmarium. A complementary quantitative study was performed during the last year of sampling ( 2018), which revealed that most taxa have their highest densities in the months with low precipitation and when the water's conductivity and transparency are greater. Our results also have implications for the conservation of the biota from Marimbus do Baiano and understand South America's desmids' biogeography since some rare taxa identified here were previously only known from other continents such as Europe and Africa.

Periphytic algal flora of the low Doce river, Espírito Santo State, Brazil, after ore tailings flow, 1: smooth cell walled Cosmarium Corda (Zygnematophyceae, Desmidiaceae.

“…Over 600 Cosmarium taxa were recorded for Brazil (Biolo & Bicudo 2018), and the genus was more intensively studied in the south region where numerous taxonomic studies revealed its presence in both phytoplankton and periphyton of reservoirs and rivers. Recent floristic studies recording the presence of Cosmarium in Brazil include States such as Paraná (Silva & Cecy 2004, Bortolini et al 2010, Felisberto & Rodrigues 2010, Biolo et al 2013, Menezes et al 2011, Carvalho et al 2015, Aquino et al 2016, Osório et al 2018, Rodrigues & Moresco 2021), São Paulo (Bicudo et al 2019, Felisberto & Rodrigues 2010, Bahia (Oliveira et al 2010, Oliveira et al 2011, Oliveira et al 2016, Ramos et al 2018, Ramos et al 2021, Goiás (Felisberto & Rodrigues 2004), Distrito Federal (Estrela et al 2011), Amazonas (Saturnino et al 2020), Sergipe (Burle et al 2020), Mato Grosso and Rio de Janeiro (Kanetsuna 2004). Furthermore, in the last 10 years five new species of Cosmarium were described based on Brazilian material: Cosmarium bahianum G.J.P.…”

Periphytic algal flora of the low Doce river, Espírito Santo State, Brazil, after ore tailings flow, 1: smooth cell walled Cosmarium Corda (Zygnematophyceae, Desmidiaceae

“…Over 600 Cosmarium taxa were recorded for Brazil (Biolo & Bicudo 2018), and the genus was more intensively studied in the south region where numerous taxonomic studies revealed its presence in both phytoplankton and periphyton of reservoirs and rivers. Recent floristic studies recording the presence of Cosmarium in Brazil include States such as Paraná (Silva & Cecy 2004, Bortolini et al 2010, Felisberto & Rodrigues 2010, Biolo et al 2013, Menezes et al 2011, Carvalho et al 2015, Aquino et al 2016, Osório et al 2018, Rodrigues & Moresco 2021), São Paulo (Bicudo et al 2019, Felisberto & Rodrigues 2010, Bahia (Oliveira et al 2010, Oliveira et al 2011, Oliveira et al 2016, Ramos et al 2018, Ramos et al 2021, Goiás (Felisberto & Rodrigues 2004), Distrito Federal (Estrela et al 2011), Amazonas (Saturnino et al 2020), Sergipe (Burle et al 2020), Mato Grosso and Rio de Janeiro (Kanetsuna 2004). Furthermore, in the last 10 years five new species of Cosmarium were described based on Brazilian material: Cosmarium bahianum G.J.P.…”