Evolutionary mechanisms of runaway chromosome number change in Agrodiaetus butterflies

Abstract

Despite predictions of the classic, hybrid-sterility model of chromosomal speciation, some organisms demonstrate high rate of karyotype evolution. This rate is especially impressive in Agrodiaetus butterflies that rapidly evolved the greatest chromosome number diversity known in animal kingdom within a single subgenus. Here we analyzed karyotype evolution in Agrodiaetus using phylogenetic comparative methods. We found that chromosome numbers possess a strong phylogenetic signal. This disproves the chromosome megaevolution model that proposes multiple chromosome rearrangements to accumulate independently in each of closely related species. We found that Brownian motion gives a more adequate description of observed trait changes than Ornstein-Uhlenbeck model. This indicates that chromosome numbers evolve via random walk along branches of the phylogeny. We discovered a correlation between karyotype changes and phylogeny branch lengths. This gradual pattern is inconsistent with the hybrid-sterility model which, due to association of major chromosome changes with cladogenetic events, predicts a high degree of punctualism in karyotype evolution. Thus, low underdominace of chromosomal rearrangements and/or prevalence of the recombination-suppression model over the hybrid-sterility model of chromosome speciation are the most common engines of the runaway chromosome number change observed.

A new butterfly species from south Russia revealed through chromosomal and molecular analysis of the Polyommatus (Agrodiaetus) damonides complex (Lepidoptera, Lycaenidae)

“…The accumulation of multiple fusions/fissions can reduce gene flow between chromosomally divergent populations not only via (i) the hybrid-sterility mechanism (when chromosomal rearrangements reduce fertility of chromosomal heterozygotes), but also via (ii) the suppressed-recombination mechanism (even if chromosomal rearrangements are neutral and do not influence fertility of chromosomal heterozygotes) (Faria and Navarro 2010). Comparative phylogenetic analyses demonstrates that the second mechanism is more probable in Agrodiaetus (Vershinina and Lukhtanov 2017), and the gradual accumulation of chromosomal fusions-fissions can certainly drive speciation (Lukhtanov et al 2005, Kandul et al 2007). …”

“…Many of them have extremely local ‘dot-like’ distributions that are restricted to particular mountain valleys in the Balkan Peninsula, Asia Minor, Transcaucasus, Iran and Central Asia (Vila et al 2010, Lukhtanov et al 2015a,b, Eckweiler and Bozano 2016, Vishnevskaya et al 2016). This subgenus is a model system in studies of speciation (Lukhtanov et al 2005, Wiemers et al 2009), intraspecific differentiation (Dincă et al 2013, Przybyłowicz et al 2014), and rapid karyotype evolution (Lukhtanov and Dantchenko 2002a, Kandul et al 2007, Vershinina and Lukhtanov 2013, 2017). …”

Research of composite fuels thermophysical properties based on low-grade coals with addition of fine sawdust and flour industry wastes

“…In this case, the use of local resources in the form of solid composite fuel made of low-grade coals with addition of waste from timber industry and impurities of flour waste as binder is promising for the near future. Studies in these areas are actively conducted; their results are published in papers [1][2][3][4][5][6][7][8]. But results of [1][2][3][4][5][6][7][8] are not the basis for analyzing dependencies of composite fuels thermophysical properties based on low-grade coals with addition of fine sawdust and flour industry wastes.…”

“…Studies in these areas are actively conducted; their results are published in papers [1][2][3][4][5][6][7][8]. But results of [1][2][3][4][5][6][7][8] are not the basis for analyzing dependencies of composite fuels thermophysical properties based on low-grade coals with addition of fine sawdust and flour industry wastes. Analysis of composite fuels formation with operational and energy characteristics close to homogeneous coal, but with high environmental parameters is relevant.…”

“…It is known [1][2][3][4], that coal is a basic fuel for power generation in small-scale power engineering [4][5]. Significant expenditures of funds for its supply to remote regions of the Russian Federation lead to an increase in final cost of energy resources in two or more times, depending on territorial location [5][6][7][8].…”