Molecular data support a rapid radiation of aphids in the Cretaceous and multiple origins of host alternation

Abstract

Many aphids display a remarkably complex life cycle of host alternation, in which cyclical parthenogenesis is combined with the obligate use of two unrelated host plants. We used mitochondria1 ribosomal DNA @artial 12s and 16s) sequences to reconstruct the phylogeny of aphids, to determine how many origins of host alternation and correlated major hostplant shifts have occurred. Our results agreed with previous morphological studies in that species clustered with good support at the level of tribes. There was little well-supported phylogenetic structure at levels deeper than tribes, however, except for the monophyly of two subfamilies, Aphidinae and Lachninae. We argue that aphids experienced a rapid radiation at the tribal level, after host shifting from gymnosperms to angiosperms. A rapid radiation is consistent with aphid fossils, which record the presence of few subfamilies in the late Cretaceous, but most extant tribes by the early Tertiary. Plant fossils also record host plants of aphid tribes diversifying during this time. A hypothesized mechanism by which host alternation has evolved (fundatrix specialization), coupled with the rapid radiation, implies that this life cycle may have originated as often as in the ancestor of each tribe that displays it. We also consider, however, an alternative hypothesis of fewer origins. The basal radiation of Aphididae was dated from molecular sequences to have occurred at approximately 80-1 50 Mya.

Sequence Conservation and Functional Constraint on Intergenic Spacers in Reduced Genomes of the Obligate Symbiont Buchnera

“…We reconstructed phylogenies based on sequences of proteins inferred from the sequenced genomes; these were consistent both with those based on 16S rRNA sequences for a larger set of species (Figure S1) and with current knowledge of aphid phylogenetic relationships [20]–[21]. Relationships were unambiguous except that the branching order of the 3 Buchnera -Ap genomes could not be resolved unequivocally due to the recency of their divergence.…”

Developmental Origin and Evolution of Bacteriocytes in the Aphid–Buchnera Symbiosis

“…Using the anti-Dll antibody, we examined development of the bacteriocytes in two species of aphids that diverged from A. pisum (subfamily Aphidinae) approximately 80–150 million years ago (von Dohlen and Moran 2000): Pemphigus spyrothecae (Eriosomatinae) and Tuberaphis styraci (Hormaphidinae) (discussed below). In both cases, Dll is expressed in a small number of bacteriocyte nuclei of the blastoderm-stage embryo and additional Dll-expressing cells are recruited later.…”

Macroevolutionary Patterns in the Aphidini Aphids (Hemiptera: Aphididae): Diversification, Host Association, and Biogeographic Origins

“…Fossils of most extant subfamilies are known from the Eocene, but only two extant groups, Aphidinae and Neophyllaphidinae, are known from the Late Cretaceous [15], [16]. Although there are few fossils of extant aphids that can be used to infer the exact time for molecular calibration, molecular dating for aphids was attempted in previous phylogenetic studies [16], [38].…”