Further Study on the Esterase Patterns of Sibling Species in the Drosophila saltans Subgroup (saltans Group): Intraspecific and Interspecific Variations in the Development
Abstract:Twenty of the 32 esterase bands previously detected in the adults of D. prosaltans, D. saltans and D. austrosaltans were found in larvae and pupae studied in this work. The results showed that, in addition to expressing the highest number of esterase bands, the adult stage of the three species exhibited the highest degree of expression (amount of synthesis) for most of the bands. Differences between larval and pupal stages were detected in the degree of expression (amount of synthesis) of the bands and in the … Show more
“…In general, phylogenetic relationships within the saltans group based on different markers have been found to be incongruent, but monophyly of the group has always been recovered [4], [7], [17]. The same occurred in the present study.…”
Section: Discussionsupporting
confidence: 75%
“…The markers used in these evolutionary studies include morphological characters [3], [4], chromosomal polymorphisms [5], esterase patterns [6], [7], [8], degree of reproductive isolation [5], [9], gene sequence variation [10], [11] and transposable elements [12], [13], [14], [15], [16].…”
The Drosophila saltans group consists of five subgroups and 21 species, most of which have been identified only by morphological aspects of the male terminalia revealed by drawings using a camera lucida and a bright-field microscope. However, several species in the group, mainly those included in the saltans subgroup, are difficult to differentiate using only these characteristics. In this study, we used scanning electron microscopy (SEM) to analyze 19 structures of the male terminalia in 10 species from the five saltans subgroups. Among these structures, nine could be identified only through SEM analysis. We aimed to find other characteristics useful for morphological recognition of these species and to use these characteristics for phylogenetic reconstruction. These morphological differences enabled us to effectively distinguish among sibling species. These findings confirmed the monophyly of this group as previously determined in evolutionary studies based on other markers. The single most parsimonious tree (CI = 87 and RI = 90) indicated that the cordata subgroup is the most basal lineage and the saltans subgroup is the most apical lineage, as shown in earlier studies based on morphological data. However, our findings differed somewhat from these studies with respect to the phylogenetic relationships of species in the saltans group indicating that this group is still a puzzle that remains to be deciphered.
“…In general, phylogenetic relationships within the saltans group based on different markers have been found to be incongruent, but monophyly of the group has always been recovered [4], [7], [17]. The same occurred in the present study.…”
Section: Discussionsupporting
confidence: 75%
“…The markers used in these evolutionary studies include morphological characters [3], [4], chromosomal polymorphisms [5], esterase patterns [6], [7], [8], degree of reproductive isolation [5], [9], gene sequence variation [10], [11] and transposable elements [12], [13], [14], [15], [16].…”
The Drosophila saltans group consists of five subgroups and 21 species, most of which have been identified only by morphological aspects of the male terminalia revealed by drawings using a camera lucida and a bright-field microscope. However, several species in the group, mainly those included in the saltans subgroup, are difficult to differentiate using only these characteristics. In this study, we used scanning electron microscopy (SEM) to analyze 19 structures of the male terminalia in 10 species from the five saltans subgroups. Among these structures, nine could be identified only through SEM analysis. We aimed to find other characteristics useful for morphological recognition of these species and to use these characteristics for phylogenetic reconstruction. These morphological differences enabled us to effectively distinguish among sibling species. These findings confirmed the monophyly of this group as previously determined in evolutionary studies based on other markers. The single most parsimonious tree (CI = 87 and RI = 90) indicated that the cordata subgroup is the most basal lineage and the saltans subgroup is the most apical lineage, as shown in earlier studies based on morphological data. However, our findings differed somewhat from these studies with respect to the phylogenetic relationships of species in the saltans group indicating that this group is still a puzzle that remains to be deciphered.
“…In addition to specific expression variation between sexes and in parts of the body, detected in the present study, variation of esterase expression during development of species in the saltans group were also described, showing that, besides the presence of stage-specific bands, the expression of the bands from loci 1 to 3 predominated in pupae, while, in larvae, bands from loci 4 to 9 were predominantly produced, with some variation among strains and species (Nascimento and Bicudo 2006). Taken together, the observations on the esterases of species from the saltans group may be considered a good tool for further studies on gene structure divergence in the evolutionary process and corresponding functional changes.…”
Section: Discussionsupporting
confidence: 71%
“…Nascimento and Bicudo (2006) had already suggested its involvement in the physiology of the nervous system.…”
Esterases are known for their involvement in several physiological processes and high degree of polymorphism, in many organisms. Such polymorphism has been used to characterize species and species groups and to study genetic changes occurred in their evolutionary history. In the present study, the esterase patterns of 19 strains from 10 species representative of the five subgroups of the saltans species group were analyzed using polyacrylamide gel electrophoresis and alpha- and beta- naphthyl acetates as substrates. Fifty-one esterase bands were detected and classified as 31 alpha-esterases, 18 beta-esterases and two alpha/beta-esterases. On the basis of the inhibition patterns using Malathion and eserine sulfate, 34 bands were classified as carboxylesterases, 14 as acethylesterases and three as cholinesterases. Ten gene loci were tentatively established on the basis of data on band position in the gel, substrate preference and inhibition pattern. Twenty bands were species-specific, the remaining being shared by species from the same or different subgroups. Bands detected exclusively in males and bands with a different frequency or degree of expression between sexes were also detected. In the gels prepared for analysis of gene expression in the body parts (head, thorax and abdomen), the degree of expression of the beta-esterases was higher in the thorax, while the alpha-esterases were expressed predominantly in the abdomen and thorax. A global view of the data available at present on the esterases of the species from the saltans group and their degree of polymorphism are presented, as well as the possibility of using some beta-esterases, because of their characteristics in the gels, as markers for species identification.
“…Although the monophyly of the subgroups has been confirmed by different phylogenetic methods, the relationships among and within them are not. Hypothesis for their evolutionary relationships have been proposed using different methods and different morphological characters (Magalhães and Björnberg 1957; Throckmorton 1962; Throckmorton and Magalhães 1962; O’Grady et al 1998; Yassin 2009; Souza et al 2014; Roman et al 2022), chromosome polymorphism (Bicudo 1973a), reproductive isolation (Bicudo 1973b; Bicudo and Prioli 1978; Bicudo 1979), protein polymorphism (Nascimento and Bicudo 2002) and gene sequences (Pélandakis and Solignac 1993; O’Grady et al 1998; Rodríguez-Trelles et al 1999; de Castro and Carareto 2004; de Setta et al 2007; Roman et al 2022). The evolutionary relationships proposed are summarized in Supplementary Table S1.…”
Phylogenomics revealed reticulate evolution to be widespread across taxa, but whether reticulation is due to low statistical power (soft polytomy) or true evolutionary patterns (hard polytomy) remains a field of investigation. Here, we investigate the phylogeny and quantify reticulation in the Drosophila saltans species group, a Neotropical clade of the subgenus Sophophora comprising 23 species arranged in five subgroups, namely cordata, elliptica, parasaltans, saltans and sturtevanti, whose relationships have long been problematic. We sequenced and assembled the genomes of 15 species. Phylogenetic analyses revealed conflicting topologies between the X chromosome, autosomes and the mitochondria. We extended the ABBA-BABA test of asymmetry in phylogenetic discordance to cases where no "true" species tree could be inferred, and applied our new test (called 2A2B) to >50 kb-long 1,797 syntenic blocks with conserved collinearity across Neotropical Sophophora. High incidences of reticulation (sometimes up to 90% of the blocks) were restricted to three nodes on the tree, at the split between the cordata-elliptica-saltans subgroups and at the origin of the sturtevanti and saltans subgroups. By contrast, cases with asymmetric discordances, which are often interpreted as evidence for interspecific introgression, did not exceed ~5% of the blocks. Historical biogeography analysis revealed that short inter-speciational times and greater overlap of ancestral geographical ranges partly explain cases with predominant reticulation. Therefore, episodic rapid radiations have played a major role in the evolution of this largely understudied Neotropical clade.
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