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Insect Lineages (insect + lineage)
Selected AbstractsPHYTOPHAGOUS INSECT,MICROBE MUTUALISMS AND ADAPTIVE EVOLUTIONARY DIVERSIFICATIONEVOLUTION, Issue 5 2008Eric M. Janson Adaptive diversification is a process intrinsically tied to species interactions. Yet, the influence of most types of interspecific interactions on adaptive evolutionary diversification remains poorly understood. In particular, the role of mutualistic interactions in shaping adaptive radiations has been largely unexplored, despite the ubiquity of mutualisms and increasing evidence of their ecological and evolutionary importance. Our aim here is to encourage empirical inquiry into the relationship between mutualism and evolutionary diversification, using herbivorous insects and their microbial mutualists as exemplars. Phytophagous insects have long been used to test theories of evolutionary diversification; moreover, the diversification of a number of phytophagous insect lineages has been linked to mutualisms with microbes. In this perspective, we examine microbial mutualist mediation of ecological opportunity and ecologically based divergent natural selection for their insect hosts. We also explore the conditions and mechanisms by which microbial mutualists may either facilitate or impede adaptive evolutionary diversification. These include effects on the availability of novel host plants or adaptive zones, modifying host-associated fitness trade-offs during host shifts, creating or reducing enemy-free space, and, overall, shaping the evolution of ecological (host plant) specialization. Although the conceptual framework presented here is built on phytophagous insect,microbe mutualisms, many of the processes and predictions are broadly applicable to other mutualisms in which host ecology is altered by mutualistic interactions. [source] Analysis of nubbin expression patterns in insectsEVOLUTION AND DEVELOPMENT, Issue 5 2004Hua Li Summary Previous studies have shown that the gene nubbin (nub) exhibits large differences in expression patterns between major groups of arthropods. This led us to hypothesize that nub may have evolved roles that are unique to particular arthropod lineages. However, in insects, nub has been studied only in Drosophila. To further explore its role in insects in general, we analyzed nub expression patterns in three hemimetabolous insect groups: zygentomans (Thermobia domestica, firebrat), dyctiopterans (Periplaneta americana, cockroach), and hemipterans (Oncopeltus fasciatus, milkweed bug). We discovered three major findings. First, observed nub patterns in the ventral central nervous system ectoderm represent a synapomorphy (shared derived feature) that is not present in other arthropods. Furthermore, each of the analyzed insects exhibits a species-specific nub expression in the central nervous system. Second, recruitment of nub for a role in leg segmentation occurred early during insect evolution. Subsequently, in some insect lineages (cockroaches and flies), this original role was expanded to include joints between all the leg segments. Third, the nub expression in the head region shows a coordinated change in association with particular mouthpart morphology. This suggests that nub has also gained an important role in the morphological diversification of insect mouthparts. Overall, the obtained data reveal an extraordinary dynamic and diverse pattern of nub evolution that has not been observed previously for other developmental genes. [source] Molecular evidence for dispersal rather than vicariance as the origin of flightless insect species on the Chatham Islands, New ZealandJOURNAL OF BIOGEOGRAPHY, Issue 5 2000Steven A. Trewick Abstract Aim The aim was to use mitochondrial DNA sequence data to test between vicariance and oversea dispersal explanations for the origin of the Chatham Islands biota. Location New Zealand and the Chatham Islands, separated by c. 800 km in the south-west Pacific Ocean. Methods DNA sequences from the mitochondrial gene cytochrome oxidase I (COI) were obtained from four genera of relatively large and flightless insects (Coleoptera, Geodorcus, Mecodema; Orthoptera,Talitropsis; Blattoidea,Celatoblatta). These were used to test alternative hypotheses for the origin of the Chatham taxa. Results Phylogenetic analysis revealed the Chatham taxa in each genus to be monophyletic. Genetic distances exhibited by these genera, between taxa found on the Chatham Islands and mainland New Zealand were relatively low (11.2, 2.8, 3.0 and 4.9%, respectively). Main conclusions Even allowing for variation in molecular evolutionary rates, these genetic distances indicate phylogenetic separation of New Zealand and Chatham insect lineages in the Pliocene (2,6 Ma). Such dates are more than one order of magnitude too recent to be explained by vicariant (tectonic) processes. Oversea dispersal from New Zealand to the Chatham Islands is implicated and this conclusion is in keeping with the taxonomy of the endemic avifauna, flora and fossil molluscan fauna. [source] Evolution of a complex coevolved trait: active pollination in a genus of fig waspsJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2004J. M. Cook Abstract Only three insect lineages have evolved complex active pollination behaviour and only fig wasps (Agaonidae) have also reverted from active to passive pollination. Previously, it was assumed that there was a single origin of active pollination in fig wasps, followed by one independent loss in each of five genera. We show here that there have been three to six changes in pollination behaviour within just one genus (Pleistodontes). The results suggest multiple gains of active pollination in fig wasps, but are sensitive to assumptions about the relative costs of gaining and losing this complex behaviour. In addition, previous comparative studies at higher taxonomic levels have reported correlated evolution between active pollination in wasps and low anther/ovule ratios in figs. We report that changes in pollination behaviour between congeneric species correlate perfectly with changes in anther/ovule ratios in the host figs, showing no phylogenetic inertia in coadaptation at the species level. [source] Mating biology of the leaf-cutting ants Atta colombica and A. cephalotesJOURNAL OF MORPHOLOGY, Issue 10 2006Boris Baer Abstract Copulation behavior has often been shaped by sexually selected sperm competition or cryptic female choice. However, manipulation of previously deposited ejaculates is unknown in the social Hymenoptera and the degree to which sperm competes after insemination or is actively selected by females has remained ambiguous. We studied the mating process in the leaf-cutting ants Atta colombica and A. cephalotes, which belong to one of the few derived social insect lineages where obligate multiple mating has evolved. As copulations often occur at night and in remote places, direct observations were impossible, so we had to reconstruct the sequential copulation events by morphological analysis of the male and female genitalia and by tracking the process of sperm transfer and sperm storage. We show that Atta male genitalia have two external rows of spiny teeth, which fit into a specialized pouch organ in the female sexual tract. Reconstruction of the sperm storage process indicated that sperm is transferred to the spermatheca during or immediately after ejaculation and without being mixed with sperm and seminal fluids from other males. A convergent mechanism of direct sperm transfer to the spermatheca of queens is known from two species of dwarf honeybees. Direct sperm transfer may restrict female control over the sperm storage process and the number of males that contribute to the stored sperm. J. Morphol. © 2006 Wiley-Liss, Inc. [source] The problem with "the Paleoptera Problem:" sense and sensitivityCLADISTICS, Issue 5 2003T.Heath Ogden While the monophyly of winged insects (Pterygota) is well supported, phylogenetic relationships among the most basal extant pterygote lineages are problematic. Ephemeroptera (mayflies) and Odonata (dragonflies) represent the two most basal extant lineages of winged insects, and determining their relationship with regard to Neoptera (remaining winged insects) is a critical step toward understanding insect diversification. A recent molecular analysis concluded that Paleoptera (Odonata Ephemeroptera) is monophyletic. However, we demonstrate that this result is supported only under a narrow range of alignment parameters. We have further tested the monophyly of Paleoptera using additional sequence data from 18SrDNA, 28S rDNA, and Histone 3 for a broader selection of taxa and a wider range of analytical methodologies. Our results suggest that the current suite of molecular data ambiguously resolve the three basal winged insect lineages and do not provide independent confirmation of Odonata + Neoptera as supported via morphological data. [source] | |||||||||||||||||||