Is genome size influenced by colonization of new environments in dipteran species?

Abstract

Genome size differences are usually attributed to the amplification and deletion of various repeated DNA sequences, including transposable elements (TEs). Because environmental changes may promote modifications in the amount of these repeated sequences, it has been postulated that when a species colonizes new environments this could be followed by an increase in its genome size. We tested this hypothesis by estimating the genome size of geographically distinct populations of Drosophila ananassae, Drosophila malerkotliana, Drosophila melanogaster, Drosophila simulans, Drosophila subobscura, and Zaprionus indianus, all of which have known colonization capacities. There was no strong statistical differences between continents for most species. However, we found that populations of D. melanogaster from east Africa have smaller genomes than more recent populations. For species in which colonization is a recent event, the differences between genome sizes do not thus seem to be related to colonization history. These findings suggest either that genome size is seldom modified in a significant way during colonization or that it takes time for genome size of invading species to change significantly.

Genetic Architecture of Local Adaptation in Lunar and Diurnal Emergence Times of the Marine Midge Clunio marinus (Chironomidae, Diptera)

“…By comparing to organisms with known genome size, C. marinus nuclei were found to be about half the size of those of Drosophila elegans and about 0.95 fold the size of those of Drosophila subobscura . Comparison with the published C values of 0.2 pg for D. elegans [14] and 0.15 pg for D. subobscura [15] leads to two slightly inconsistent estimates for C. marinus , namely 0.1 pg and 0.14 pg. The transformation of C value into number of nucleotides depends on the AT content of the genome and possible base modifications, and a C value of 1 pg corresponds approximately to 976 Mb of DNA sequence [16].…”

Globalization and fruitfly invasion and expansion: the medfly paradigm

“…However, the genetic reorganization, resulting from TE mobilization, can also give rise to new variation, that may have beneficial consequences for the host also in terms of adaptation (Kidwell and Lish 2000;Volff 2005). In various Drosophila species, TE mobilization, hence the possibility of enhancing genome variability, has been shown to follow colonization (Viera et al 1999;McCollum et al 2002;Vieira and Bié mont 2004;Nardon et al 2005).…”

Revisiting horizontal transfer of transposable elements in Drosophila

“…Along with D. melanogaster and D. simulans, there are, for instance, D. ananassae, D. malerkotliana, D. subobscura and more recently Zaprionus indianus. Thanks to the data available, including their phylogenies, genetics, biogeography and history, these species are probably highly useful for testing this hypothesis (Nardon et al, 2005).…”