Intraspecific variation in growth, morphology and toxin quotas for the cyanobacterium, Cylindrospermopsis raciborskii

•Twenty four Cylindrospermopsis raciborskii isolates from a 200 mL water sample varied in cell size, growth rate, and toxin quota.•Euclidean distance analysis grouped isolates by CYN:dCYN, QCYNs, growth rate or size.•C. raciborskii isolates have high phenotype variation on a small spatial scale.

Cylindrospermopsis raciborskii is a bloom forming cyanobacterium with complex population dynamics and toxicity. In January of 2013 a single sample was collected from surface waters in Lake Wivenhoe, Australia, and twenty-four individual trichomes were isolated. Each isolate exhibited differences in growth rate, toxin cell quota and morphology, in the absence of phylogenetic heterogeneity. This study demonstrates substantial intraspecific isolate variation within a small sample and this has implications for understanding the population dynamics of this species.