HERITABILITY OF MANTLE AREOLAR CHARACTERS IN AULACOSEIRA SUBARCTICA (BACILLARIOPHYTA)¹

Abstract

Are size and arrangement of valve mantle areolae in Aulacoseira Thwaites adapted to light intensity? To test one criterion demonstrating an adaptation, heritability experiments were run on isolates of Aulacoseira subarctica (Müller) Haworth. Several clones of A. subarctica were isolated from Yellowstone Lake (Wyoming, USA), Lewis Lake (Wyoming), and East Rosebud Lake (Montana, USA). Two to four clones from each lake were grown in batch cultures under three irradiance levels: 2, 11.4, and 115 lmol photons . m À 2 . s À 1 . Five randomly chosen valves for each of two replicates of each clone were examined using a scanning electron microscope for a total of 300 valves. Size measurements were taken for each valve examined, and images of mantle areolae were captured on film at a magnification of 20,000 Â . Each image was digitized, and quantitative morphometric areolar characters were measured. A quantitative genetic analysis was performed within each light environment for the mean area of the external opening of mantle areolae, the mean distance between areolae within pervalvar striae, and the mean distance between pervalvar striae. Resulting estimates of heritability from among-lake and within-lake analyses indicate that all three mantle areolar characters could presently respond to selection and thus have potentially done so in the past.

Genetic diversity and evolution in eukaryotic phytoplankton: revelations from population genetic studies

“…Experimental studies provide some support for this hypothesis. Provided sufficient genetic variation in phenotypic traits for selection to act on, a rapid evolutionary response can be predicted (Wood et al, 1987(Wood et al, , 2005Edgar and Theriot, 2003). Moreover, several authors have suggested that the seemingly cosmopolitan distribution and maintenance of relatively high abundances of many species of phytoplankton result from changes in genotype composition within species (cf.…”

Molecular Systematics and the Diatom Species

“…Since virtually every diatom species is inextricably linked to a morphological, character-based definition, candidates for mating experiments are chosen on the basis of their characters, which suggests some level of confidence in the character-based classification. Note also that classic heritability studies still provide an excellent way to explore the potential evolutionary importance of morphological characters in diatoms (Edgar and Theriot 2003;Wood et al 1987). A positive trend in BSC-based diatom research is the increasing number of studies that cite direct evidence from mating experiments (Amato et al 2007;Behnke et al 2004;Mann et al 2004;Vanormelingen et al 2007Vanormelingen et al , 2008, rather than indirect character-based evidence, to support species boundaries under the BSC.…”

Centric and Araphid Diatoms

“…The genus may extend back to the Late Cretaceous (Ambwani et al, 2003). Edgar and Theriot (2004) conducted a phylogenetic analysis of Aulacoseira using morphological and molecular data and studied the heritability of valve mantle features (Edgar and Theriot, 2003).…”