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Background: The genomes of eukaryotes vary enormously in size, with much of this diversity driven by differences in the abundances of transposable elements (TEs). There is also substantial structural and phylogenetic diversity among TEs, such that they can be classified into distinct classes, superfamilies, and families. Possible relationships between TE diversity (and not just abundance) and genome size have not been investigated to date, though there are reasons to expect either a positive or a negative correlation. This study compares data from 257 species of animals, plants, fungi, and "protists" to determine whether TE diversity at the superfamily level is related to genome size. Results: No simple relationship was found between TE diversity and genome size. There is no significant correlation across all eukaryotes, but there is a positive correlation for genomes below 500Mbp and a negative correlation among land plants. No relationships were found across animals or within vertebrates. Some TE superfamilies tend to be present across all major groups of eukaryotes, but there is considerable variance in TE diversity in different taxa. Conclusions: Differences in genome size are thought to arise primarily through accumulation of TEs, but beyond a certain point (~500 Mbp), TE diversity does not increase with genome size. Several possible explanations for these complex patterns are discussed, and recommendations to facilitate future analyses are provided. [ABSTRACT FROM AUTHOR]

This study provides C-value (haploid nuclear DNA content) estimates for 31 species of ladybird beetles (representing 6 subfamilies and 8 tribes), the first such data for the family Coccinellidae. Despite their unparalleled diversity, the Coleoptera have been very poorly studied in terms of genome size variation, such that even this relatively modest sample of species makes the Coccinellidae the third best studied family of beetles, behind the Tenebrionidae and Chrysomelidae. The present study provides a comparison of patterns of genome size variation with these two relatively well-studied families. No correlation was found between genome size and body size in the ladybirds, in contrast to some other invertebrate groups but in keeping with findings for other beetle families. However, there is some indication that developmental time and/or feeding ecology is related to genome size in this group. Some phylogenetic patterns and possible associations with subgenomic features are also discussed. [ABSTRACT FROM AUTHOR]