Review. When to leave the brood chamber? Routes of dispersal in mites associated with burying beetles

Most nests of brood-caring insects are colonized by a rich community of mite species. Since these nests are ephemeral and scattered in space, phoresy is the principal mode of dispersal in mites specializing on insect nests. Often the mites will arrive on the nest-founding insect, reproduce in the nest and their offspring will disperse on the insect's offspring. A literature review shows that mites reproducing in the underground brood chambers of burying beetles use alternative routes for dispersal. For example, the phoretic instars of Poecilochirus spp. (Mesostigmata: Parasitidae) disperse early by attaching to the parent beetles. Outside the brood chamber, the mites switch host at carcasses and pheromone-emitting male beetles, where juvenile and mature burying beetles of several species congregate. Because they preferably switch to beetles that are reproductively active and use all species of burying beetles within their ranges, they have a good chance of arriving in a new brood chamber. Other mite associates of burying beetles (Alliphis necrophilus and Uropodina) disperse from the brood chamber on the beetle offspring. We suggest that these mites forgo the possible time gain of dispersing early on the parent beetles because their mode of attachment precludes host switching. Their phoretic instars, once attached, have to stay on their host and so only dispersing on the beetle offspring guarantees that they are present on reproducing burying beetles of the next season. The mites associated with burying beetles providean example of multiple solutions to one life history problem – how to find a new brood chamber for reproduction. Mites that have mobile phoretic instars disperse on the parent beetles and try to arrive in the next brood chamber by host switching. They are independent of the generation cycle of a single host and several generations of mites per host generation are possible. Mites that are constrained by their mode of attachment disperse on the beetle offspring and wait until their host becomes mature and reproduces. By doing this they synchronize their generation time with the generation time of their host species. Exp Appl Acarol 22: 621–631 © 1998 Kluwer Academic Publishers     

Current Intraspecific Dynamics of Sequence Evolution Differs from Long-Term Trends and Can Account for the AT-Richness of Honeybee Mitochondrial DNA

The very high AT content of hymenopteran mtDNA has warranted speculation about nucleotide substitution processes in this group. Here we investigate the pattern of honeybee, Apis mellifera, mtDNA nucleotide polymorphisms inferred from phylogeny in terms of differences between the ATPase6, COI, COII, COIII, cytochrome b, and ND2 genes and strand asymmetry in mutation rates. The observed transition/transversion ratios and the distribution of nonsynonymous substitutions between regions differed significantly. The pattern of differences between genes leading to these heterogeneities (the ATPase6 and COIII genes group apart from the rest) differed markedly from that predicted on the basis of long-term evolutionary change and may indicate differences between current and long-term dynamics of sequence evolution. Also, there is strong strand asymmetry in substitutions, which probably results in a mutability of G and C sufficiently high to account for the AT-richness of honeybee mtDNA. Received: 21 October 1998 / Accepted: 27 January 1999     

Phylogenetic relationships among bumble bees (Bombus, latreille) inferred from mitochondrial cytochrome b and cytochrome oxidase I sequences

We conducted a molecular study intending to derive an estimate of the relationships within the genus Bombus (bumble bees) by comparing the mitochondrial cytochrome b and cytochrome oxidase I (COI) genes from 19 species, spanning 10 of approximately 16 European subgenera and 3 subgenera from North and South America. Our trees differ from the most recent classifications of bumble bees. Although bootstrap values for deep branches are low, our sequences show significant data structure and low homoplasy, and all trees share some groups and patterns. In all cases, the subgenus Bombus s. str. clusters among the most derived bumble bees, contrary to other molecular studies. In all trees, B. funebris is the sister taxon of B. robustus, and in five of the six trees, B. wurflenii is the sister taxon to this clade. B. nevadensis is basal to the other species in the analysis of the cytochrome b gene, but appears to be among the most derived according to the analysis of the COI region. The species representing the subgenera Thoracobombus and Fervidobombus are consistently among the earliest diverged. Species that appear in very different positions in different trees are B. nevadensis, B. mesomelas, B. balteatus, and B. hyperboreus. All subgenera with two representatives in our analysis are apparently monophyletic except Fervidobombus, Melanobombus, and Pyrobombus. The groups formed by pocket makers and non-pocket makers within Bombus also appear to be paraphyletic, and therefore some subgenera may not accurately reflect phylogeny.     

Phylogenetic relationships within the corbiculate Apinae (Hymenoptera) and the evolution of eusociality

We provide a comparison of 520 base pairs of the mitochondrial cytochrome b gene from exemplars of the Meliponini, the Apini, the Bombini and the Euglossini to determine the phylogenetic relationships within the corbiculate Apinae. Our results strongly suggest (91–97% according to bootstrap resampling) that the Meliponini and the Bombini are sister groups. This finding agrees with those of other molecular studies, but is discordant with previous hypotheses based on morphology and the combination of molecular and morphological data. If the Bombini and Meliponini are sister groups and reversal of advanced eusociality is unlikely, then advanced eusociality arose twice within this clade. However, if reversion of eusociality occurred, then it is not possible to discriminate between single or dual origins of advanced eusociality within this group.