Ly younger members of a lineage that have dispersed down an island chain as new volcanic islands in the archipelago arose from the ocean floor and became habitable. The youngest species in such a lineage would have undergone more founder events and much more exposure to volcanic environments in the course of their evolutionary history than ancestral species on older islands that are now volcanically inactive. In accord with this prediction, Hunt and colleagues [147, 148] showed via in situ hybridization an inverse correlation between euchromatic copy numbers of the Uhu element, a Tc-1 like transposon [149], and the age of the island to which each species is endemic in both the planitibia and adiastola species groups of the picture wing clade of Hawaiian Drosophila, as well as a similar relationship for the LOA element in the planitibia species group [148]. The in situ hybridization data also demonstrated variability in occupancy of TE euchromatic chromosomal sites among the populations and species sampled, confirming active transposition through evolutionary and geological time. Copy numbers of these particular TEs in the heterochromatin (and thus total genome copy numbers) for these species could not be precisely assessed due to underreplication of heterochromatic regions in Drosophila larval polytene chromosomes. However, Hunt et al. did note that the majority of the in situ labeling was concentrated at the centromeric regions of the polytene chromosomes [147], suggesting higher density and copy numbers of the Uhu element in the centromeric heterochromatin. Further, since TE insertions would initially be heterozygous, according to the hypothesis outlined here, one would expect high levelsFew organisms have the giant banded polytene chromosomes of Drosophila species that make them so favorable for in situ detection of specific nucleotide sequences. Even in these species, the in situ technique PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/25679764 has some limitations with respect to detection in heterochromatic regions, as mentioned above, and lacks the resolution to determine whether a positive signal at a particular chromosomal site is due to a single copy or several tandem copies of the sequence in question. Further, each target sequence must be Biotin-VAD-FMK custom synthesis assayed individually. For optimal detection and quantification of the TE content of an individual organism (experimental or fieldcollected), there is no substitute for access to the whole genome sequence (WGS). Although WGS data for most single-island endemic species of interest are currently lacking, the availability and decreasing cost of highthroughput next-generation sequencing technologies has significantly increased the feasibility of obtaining the requisite genome sequence data for analyses and comparisons of TE content. To acquire comprehensive TE data for multiple genomes requires targeted methods. In the first instance, transposon display methods [150] could be used to evaluate numbers and genome proportions of specific selected TEs. This approach could be used to compare representatives of the same genus on volcanic vs. continental islands, for example, to test the prediction of increased TE representation in species that evolved on volcanic islands, mentioned at the beginning of this section (prediction b). For a more comprehensive assessment of all TEs, several post-sequencing bioinformatics methods have been developed [151], which will facilitate the task of identifying and quantifying novel TE insertions in the genomes of treated.