Rom time to time, a morphologically distinct clade. The Hawaiian Drosophilidae, for example, display a

Rom time to time, a morphologically distinct clade. The Hawaiian Drosophilidae, for example, display a remarkable degree of morphological variation, with monophyletic clades characterized by bizarre modifications of mouthparts, legs, and antennae [120]. Just as TE insertions in plant genes have been shown to be associated with morphological changes [76], I posit that a major contributor to the evolution of morphological novelties in Hawaiian Drosophila may be TE insertions that modified the developmental program of adult body patterning, thereby initiating several novel and morphologically unique clades of flies in this remarkable radiation. Transposition bursts of multiple transposons could also potentially lead to rewiring of sexual behaviors and production of a cluster of species differentiated only by secondary sexual characters. This phenomenon could be the driver for diversification of the clade of morphologically cryptic Laupala crickets endemic to Hawaiian forests [121]. Among the endemic Hawaiian Drosophila, courtship behaviors are extraordinarily diverse [122, PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/25112874 123], butCraddock Biology Direct (2016) 11:Page 7 ofspecies are also morphologically diverse, suggesting that sexual selection [38, 39] has acted in concert with other forces in the evolutionary diversification of these flies.arthropods [127]. These findings are consistent with that claim that TEs serve to dramatically increase rates of molecular evolution [66].Rates of chromosomal rearrangement, and chromosomal length polymorphismTesting the hypothesisSome predicted outcomes of the hypothesis and pertinent available data Species richness and rates of evolution on volcanic islandsIf the dynamic volcanic environment induces recurrent transposition bursts and genome reorganization that facilitates speciation as hypothesized herein, then one would expect to observe (a) a higher level of species richness and single-island endemics in groups on volcanic Pedalitin permethyl ether site islands compared to the level of diversification in the same genus on (non-volcanic) continental islands; and (b) a higher total proportion of TEs in genomes of species that evolved in situ on volcanic islands compared to those that evolved on continental islands. It may be hard to precisely test these two predictions because of the difficulty in identifying matching pairs of volcanic and non-volcanic islands of similar geological age, island area, topographic complexity, and distance from source continents (a factor that likely affects immigration rates). These are all factors that play a role in the expansion of biodiversity on islands according to the General Dynamic Model of island biogeography [124] that was developed to explain plant diversification in the Canary Islands. Evidence in support of prediction (b) has yet to be collected; this topic will be addressed later in the section Proposed experimental studies. A corollary of the hypothesis of elevated levels of TE activity and genome remodeling induced by the stress of volcanic environments is the expectation for higher overall rates of evolution and speciation on volcanic islands, compared to non-volcanic islands and continents. The extremely high rates of speciation in many Hawaiian plants and animals [13, 40] are consistent with this expectation. For example, in the radiation of the Hawaiian silversword alliance, the diversification rate is much higher than in non-Hawaiian taxa [125]. Moreover, rates of regulatory gene evolution in the Hawaiian silverswords are sig.