Abstract:Behavioral changes in evolution have attracted the attention of many evolutionary biologists. Closely related species, or even individuals from different populations within a species, often exhibit remarkably different behaviors. Such behavioral diversification has been implicated as a cause of speciation in some cases, yet the mechanisms that produce and maintain these changes remain largely unknown. Drosophila melanogaster, an outstanding model organism with which to explore the causal link among the gene, n… Show more
“…Naturally occurring variants affecting behavioral traits are of particular interest because of their potential contribution to the behavioral differences that have emerged in the evolution of closely related species and, in some cases, may have even contributed to speciation (Yamamoto and Ishikawa 2013). For example, latitudinal variation in the length of a Thr-Gly repeat in the Per protein in D. melanogaster is inferred to reflect an important role in thermal adaptation (Sawyer et al 1997).…”
Although evolutionary changes must take place in neural connectivity and synaptic architecture as nervous systems become more complex, we lack understanding of the general principles and specific mechanisms by which these changes occur. Previously, we found that morphology of the larval neuromuscular junction (NMJ) varies extensively among different species of Drosophila but is relatively conserved within a species. To identify specific genes as candidates that might underlie phenotypic differences in NMJ morphology among Drosophila species, we performed a genetic analysis on one of two phenotypic variants we found among 20 natural isolates of Drosophila melanogaster. We discovered genetic polymorphisms for both positive and negative regulators of NMJ growth segregating within the variant line. Focusing on one subline, that displayed NMJ overgrowth, we mapped the phenotype to Mob2 [Monopolar spindle (Mps) one binding protein 2)], a gene encoding a Nuclear Dbf2 (Dumbbell formation 2)-Related (NDR) kinase activator. We confirmed this identification by transformation rescue experiments and showed that presynaptic expression of Mob2 is necessary and sufficient to regulate NMJ growth. Mob2 interacts in a dominant, dose-dependent manner with tricornered but not with warts, to cause NMJ overgrowth, suggesting that Mob2 specifically functions in combination with the former NDR kinase to regulate NMJ development. These results demonstrate the feasibility and utility of identifying genetic variants affecting NMJ morphology in natural populations of Drosophila. These variants can lead to discovery of new genes and molecular mechanisms that regulate NMJ development while also providing new information that can advance our understanding of mechanisms that underlie nervous system evolution.
“…Naturally occurring variants affecting behavioral traits are of particular interest because of their potential contribution to the behavioral differences that have emerged in the evolution of closely related species and, in some cases, may have even contributed to speciation (Yamamoto and Ishikawa 2013). For example, latitudinal variation in the length of a Thr-Gly repeat in the Per protein in D. melanogaster is inferred to reflect an important role in thermal adaptation (Sawyer et al 1997).…”
Although evolutionary changes must take place in neural connectivity and synaptic architecture as nervous systems become more complex, we lack understanding of the general principles and specific mechanisms by which these changes occur. Previously, we found that morphology of the larval neuromuscular junction (NMJ) varies extensively among different species of Drosophila but is relatively conserved within a species. To identify specific genes as candidates that might underlie phenotypic differences in NMJ morphology among Drosophila species, we performed a genetic analysis on one of two phenotypic variants we found among 20 natural isolates of Drosophila melanogaster. We discovered genetic polymorphisms for both positive and negative regulators of NMJ growth segregating within the variant line. Focusing on one subline, that displayed NMJ overgrowth, we mapped the phenotype to Mob2 [Monopolar spindle (Mps) one binding protein 2)], a gene encoding a Nuclear Dbf2 (Dumbbell formation 2)-Related (NDR) kinase activator. We confirmed this identification by transformation rescue experiments and showed that presynaptic expression of Mob2 is necessary and sufficient to regulate NMJ growth. Mob2 interacts in a dominant, dose-dependent manner with tricornered but not with warts, to cause NMJ overgrowth, suggesting that Mob2 specifically functions in combination with the former NDR kinase to regulate NMJ development. These results demonstrate the feasibility and utility of identifying genetic variants affecting NMJ morphology in natural populations of Drosophila. These variants can lead to discovery of new genes and molecular mechanisms that regulate NMJ development while also providing new information that can advance our understanding of mechanisms that underlie nervous system evolution.
“…While previous studies have identified differences in specific behaviors, such as courtship behavior, between these species [14,16,32,33], here we assayed the full repertoire of behaviors the flies performed in the arena, with the aim of identifying combinations of behaviors that may be evolving together. To measure this repertoire, we used a previously-described behavior mapping method [19,22] that starts from raw video images and attempts to find each animals stereotyped movements in an unsupervised manner.…”
Section: Experiments and Behavioral Quantificationmentioning
confidence: 99%
“…Variable behaviors and rapid behavioral evolution likely allows species to adapt rapidly to new or varying environments [3,4]. Despite the importance of animal behavior, progress in revealing the genetic basis of behavioral evolution has been slow [5][6][7][8]. In contrast, recent decades have seen significant progress in understanding the genetic causes of morphological evolution [9][10][11][12].…”
Although extensive behavioral changes often exist between closely related animal species, our understanding of the genetic basis underlying the evolution of behavior has remained limited. Here, we propose a new framework to study behavioral evolution by computational estimation of ancestral behavioral repertoires. We measured the behaviors of individuals from six species of fruit flies using unsupervised techniques and identified suites of stereotyped movements exhibited by each species. We then fit a Generalized Linear Mixed Model to estimate the suites of behaviors exhibited by ancestral species, as well as the intra- and inter-species behavioral covariances. We found that much of intraspecific behavioral variation is explained by differences between individuals in the status of their behavioral hidden states, what might be called their "mood." Lastly, we propose a method to identify groups of behaviors that appear to have evolved together, illustrating how sets of behaviors, rather than individual behaviors, likely evolved. Our approach provides a new framework for identifying co-evolving behaviors and may provide new opportunities to study the genetic basis of behavioral evolution.
“…Song is not restricted to males, and in some clades male-female duets are an important aspect of courtship (Satokangas et al 1994). The courtship song of D. melanogaster has been extensively studied with more than a dozen genes identified as contributing to song (Gleason 2005;Yamamoto and Ishikawa 2013). In contrast, only a few loci have been identified that also affect reproductive isolation.…”
The question of how new species evolve has been examined at every level, from macroevolutionary patterns of diversification to molecular population genetic analyses of specific genomic regions between species pairs. has been at the center of many of these research efforts. Though our understanding of the speciation process has grown considerably over the past few decades, very few genes have been identified that contribute to barriers to reproduction. The development of advanced molecular genetic and genomic methods provides promising avenues for the rapid discovery of more genes that contribute to speciation, particularly those involving prezygotic isolation. The continued expansion of tools and resources, especially for species other than, will be most effective when coupled with comparative approaches that reveal the genetic basis of reproductive isolation across a range of divergence times. Future research programs in have high potential to answer long-standing questions in speciation. These include identifying the selective forces that contribute to divergence between populations and the genetic basis of traits that cause reproductive isolation. The latter can be expanded upon to understand how the genetic basis of reproductive isolation changes over time and whether certain pathways and genes are more commonly involved.
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