Phylogeography of the freshwater red alga S irodotia ( B atrachospermales, R hodophyta) in B razil

Summary Considering the lack of knowledge on genetic variation on members of the freshwater red algal of the order Batrachospermales in tropical regions, phylogeographic patterns in S irodotia populations were investigated using two mitochondrial regions: the cox 2‐3 spacer and partial cox1 gene (barcode). Individuals identified as S irodotia delicatula were analyzed from 14 stream segments across its distribution in B razil. Phylogenetic analyses based on the ribulose‐1,5‐bisphosphate carboxylase/oxygenase large sub‐unit gene showed three clades, one representing S . delicatula, from all locations in southeastern B razil and other regions from B razil. The remaining samples formed two clades, which were highly divergent and distantly positioned from those of S . delicatula : 2.5–2.7% and 3.4–3.7%. This level of variation would warrant the species split of these taxa from mid‐western B razil. A total of eight cox 2‐3 spacer and nine cox 1 haplotypes were observed among the 122 individuals studied. One location had two cox 2‐3 haplotypes and three locations had two cox 1 haplotypes; all others had a single dominant haplotype each. The existence of high intraspecific genetic variation among individuals of distinct locations (several haplotypes), but little variation within a location seems to be a pattern for the Batrachospermales. Haplotype networks showed low variation among the haplotypes from southeastern B razil (10 locations with divergence of 0.3–1.1% for cox 2‐3, 0.1–0.3% for cox 1) and high variation among the haplotypes from the mid‐west region (four locations, 4.0–9.3% for cox 2‐3, 6.2–8.4% for cox 1). Thus, the present data clearly suggest the existence of cryptic species in Sirodotia in B razil.