new insights in phylogeny of hymenoptera

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MIODRAG GRBIC´Polyembryony in parasitic wasps: evolution of a novel mode of development
Int. J. Dev. Biol. 47: 633-642 (2003)

-Even though Hymenoptera as a group appeared 220 MYA, the first parasitic wasps fossil records date from 160 MYA (Whitfield,1998).
- New advances in the estimation of age of parasitic wasps (Whitfield, 2002)

Evaluating alternative hypotheses for the early evolution and diversification of ants
Sea´n G. Brady*†, Ted R. Schultz*, Brian L. Fisher‡, and Philip S. Ward§ PNAS 2006

-Morphological, molecular, and paleontological

-phylogenetic data set published to date, containing ca.6 kb of DNA sequence from 162 species representing all 20 ant subfamilies and 10 aculeate outgroup families.

-We use the molecular data to estimate divergence times, employing a strategy distinct from previous work by incorporating the extensive fossil record of other aculeate Hymenoptera as well as that of ants. Our age estimates for the most recent common ancestor of extant ants range from ca.115 to 135 million years ago, indicating that a Jurassic origin is highly unlikely.

- Our divergence-dating analyses, calibrated with a combination of ant and other hymenopteran fossils, indicate that the origin of extant ants occurred sometime in the early Cretaceous ca. 115–135 Mya.

-This estimate is based on the assignment of 145 Mya to the basal outgroup node, a defensible minimum age given the presence of both vespoid (Scoliidae, Vespidae) and apoid (Angarosphecidae) aculeates in deposits ca. 140 Mya (51–53).

-Major lineages of Hymenoptera appear in the same sequence in the fossil record as they are inferred to have arisen based on phylogenetic analyses of extant taxa. The first to appear is the Xyelidae 230 Mya, followed by other Symphyta 190 Mya, Apocrita 185 Mya, stem-group Aculeata 155 Mya, and crown-group Aculeata 140 Mya (13, 54).

-Jurassic hymenopteran assemblages contain a diverse array of Symphyta and nonaculeate Apocrita but no crown-group Aculeata. The Bethylonymidae, interpreted as stem-group aculeates, are known from 155–125 Mya (51, 54, 55).

-results to different age assignments to three deposits of somewhat uncertain age (Dominican amber, Sicilian amber, Green River). This analysis was motivated by a previous study (17) that reported a 28 million-year age difference in the lower (140 Mya) and upper (168 Mya) estimates for extant ants, with these differences based solely on alternate minimum-age calibrations for these three fossil strata. When we employed the same alternate calibrations on equivalent nodes in our data set, we saw a much smaller difference of 0–2 million years (depending on the particular topology and outgroup node age used) in the age estimate for extant ants.

- The range of dates estimated for the origin of extant ants in the present study (ca.115 to ca.135 Mya) contrasts with the considerably older ages (ca.140 to ca.168 Mya) generated in this previous study (17).

-Crown-group ants are known from deposits as old as 100 Mya (9, 56), and our molecular results indicate that they arose no more than 10–40 million years before this time. Of course, stem-group ants, such as Sphecomyrminae and Armaniidae (13, 43), must have originated earlier than this.

- Recent synthesis of ecological, natural history, and evolutionary data proposes that ants diversified in concert with the angiosperms (3), with the current ecologically dominant ant groups radiating primarily in the Paleogene (3) or in the late Cretaceous (17), during times of angiosperm forest proliferation. Our analyses suggest that many ant subfamilies probably originated toward the end of the Cretaceous (Table 1; see also Table 3, which is published as supporting information on the PNAS web site), with most extant genera not evolving until the Paleogene

-DNA sequence data from seven nuclear genes: 1,904 aligned bp from 18S; 2,505 bp from 28S; 421 bp from wingless; 458 bp from long-wavelength rhodopsin; 639 bp from abdominal-A; 359 bp from elongation factor 1alpha F1; and 517 bp from elongation factor 1alpha F2.

Fungus-farming insects: Multiple origins and diverse evolutionary histories Ulrich G. Mueller* and Nicole Gerardo

-termites, ants, and beetles, independently evolved the ability to grow fungi for food.

-the fungus-growing termites of the Old World (1x evolved), the fungus-growing ants of the New World (1x evolved), and the cosmopolitan, fungusgrowing beetles (7x evolved)

-In ants, the ability to cultivate fungi for food has arisen only once, dating back ca.50–60million years ago

A formicine in New Jersey Cretaceous amber (Hymenoptera: Formicidae) and early evolution of the ants
David Grimaldi* and Donat Agosti - 2000

-A worker ant (Formicina, morphagenetically basal position) preserved with microscopic detail has been discovered in Turonian-aged New Jersey amber [ca. 92 mega-annum (Ma)].

-Formicinae and Ponerinae in the mid Cretaceous indicate divergence of basal lineages of ants near the Albian (ca. 105–110 Ma) when they presumably diverged from the Sphecomyrminae.

-Ant abundance in major deposits of Cretaceous and Tertiary insects indicates that they did not become common and presumably dominant in terrestrial ecosystems until the Eocene (ca. 45 Ma). It is at this time that modern genera that form very large colonies (at least 10,000 individuals) first appear. During the Cretaceous, eusocial termites, bees, and vespid wasps also first appear—they show a similar pattern of diversification and proliferation in the Tertiary.

-Termites and vespid wasps originated in the Lower Cretaceous (Aptian to Hauterivian) (29–31)—only one certain and several possible records of social wasp nests occur in the Upper Cretaceous (32). Termites were apparently eusocial for their entire fossil record beginning in the Lower Cretaceous.

-The age of the only Cretaceous bee (33) is equivocal. However, it is probably uppermost Cretaceous (34) and belongs to the recently derived tribe Meliponini (Apidae sensu lato). The first significant record of corbiculate, social bees is in Baltic amber (Eocene), when an impressive diversity of extinct clades occurred (M. Engel, personal communication). These patterns of diversity and abundance parallel those seen in ants

-The earliest records of ant–homopteran symbioses are based on two examples involving extant ant genera in Tertiary ambers: Iridomyrmex and aphids in Baltic amber (43) and several pieces of Miocene Dominican amber containing a queen Acropyga ant carrying a pseudococcid mealybug (unpublished data).

-Honeydew was available in abundance to Cretaceous ants but may not have been exploited until the Tertiary.

In search of ant ancestors
Ted R. Schultz

convincingly that the ancestral ant diverged from aculeate wasp during the Cretaceous, no earlier than 140 mya, and more likely between 110 and 130 mya, for the following reasons:

(i) Ant-like fossils (including the Armaniidae) originating before 115 mya are entirely unknown;

(ii) the oldest known hymenopteran fossils date from the Triassic and are represented solely by the most plesiomorphic hymenopteran family, the Xyelidae;

(iii) the earliest aculeate fossils, representing the most primitive stinging wasps, appear in the late Jurassic; and

(iv) there is strong fossil evidence for a Cretaceous origin for the Vespidae, which, together with the Scoliidae and the Bethylidae, is the most likely sister group to the ants.

Michener 1988 - The oldest fossil bee - Apoid history, evolutionary stasis, and antiquity of social behavior. PNAS

-Trigona pisca, a stingess honey bee (Apidae; Meliponinae), is reported from Cretaceous New Jersey amber (96-74 million years before present). This is about twice the age of the oldest previously known fossil bee, although Tigona is one of the most derived bee genera. T. prisca is closely similar to modern neotropical species. Most of bee evolution probably occurred during the ca. 50 million years between the ginning of the Cretaceous when flowering plants (on which bees depend) appeared and the time of T. prisca. Since then, in this phyletic line of Meliponinae, there has been almost no morphological evolution. Since the fossil is a worker, social organization had arisen by its time.

-Angiosperms appeared at least by the earliest Cretaceous (about 130 Myr B.P.) (23, 24).

-Angiosperms appeared at least by the earliest Cretaceous (about 130 Myr B.P.) (23, 24). Since Trigona is a specialized genus (25) in a derived family (Apidae) of a supposedly derived group of families (longtongued bees) (26), it seems that much of bee evolution must have occurred during the period from about 130 Myr B.P. to about 80 Myr B.P. when T. prisca lived. During part or all of this 50-Myr period, evolutionary changes such as the following occurred: change from prey to pollen as the protein source for larval feeding; from solitary to highly social with a caste system; from short-tongued to long-tongued; from having simple labial palpi to sheath-like palpi that form part of the complex proboscidial sucking apparatus; from complete to much reduced wing venation; from grooming behavior patterns that serve only for cleaning to modified grooming behavior that manipulates pollen, perhaps related to the origin and maintenance of plumose hairs; perhaps from transporting pollen internally in the crop to carrying it dry in a bushy scopa, and certainly thence to carrying it moistened in a smooth corbicula surrounded by long hairs; and many more.

-Of course if angiosperms arose earlier than we now believe-for example, in the Jurassic-bees could have had a longer evolutionary history. The same could be true if early bees depended on something other than angiosperm flowers. For example, the Mesozoic gymnosperm order Bennettitales had showy bracts around its reproductive structures (27) and was probably insect pollinated, possibly visited by bees before the Cretaceous. No matter when it began, however, the meliponine characteristics of structure, physiology, and behavior, as listed above, involved impressive changes from the ancestral characteristics of sphecoid wasps.

Phylogeny of the Ants: Diversification in the Age of Angiosperms
Corrie S. Moreau,1* Charles D. Bell,2 Roger Vila,1 S. Bruce Archibald,1 Naomi E. Pierce1
Science 2006

-The monophyly of the Formicidae itself was strongly supported in all analyses.

-all analyses: division of the familiy into 3 linages:

-leptanilloid clade - basal, sister group to all other ants

-poneroid clade

-formicoid clade

-The ant fossil record is extensive, with more than 60 extant and 100 extinct genera. The oldest reliably dated fossils are ca. 100 million years (My) old, from Early Cretaceous French and Burmese ambers (14, 15). These include both Gerontoformica and Burmomyrma (Aneuretinae), with features typical of modern "crown group" ants, as well as Sphecomyrminae, with features typical of basal "stem group" ants.

-Our divergence time estimates (11) suggest that crown group ants last shared a common ancestor during the Early Cretaceous to Middle Jurassic: 140 T 8.0 million years ago (Ma) (using minimum ages) to 168 T 7.6 Ma (using maximum ages) (Fig. 1A). This is considerably older than the È125-My age estimate based on fossil data. Our findings partially overlap with those of Crozier et al. (17), who used about six taxa and mitochondrial sequence data to estimate the age of Formicidae
at 185 T 36 My.

-Brady (18) and Ward and Brady (19) used molecular clock evidence to arrive at an age estimate of 130 to 140 My for crown group ants. but....

-If ancestors of the major subfamilies were present as early as 75 to 125 Ma, why were they so slow to diversify? We infer that the rise in angiospermdominated forests was harbinger to the diversification of the ants. The window encompassing angiosperm dominance shifts on our chronogram depending on whether we accept the minimumor maximum ages for the ant fossil calibration points (Fig. 1A, shaded green areas). A lineage-throughtime (LTT) plot shows a dramatic accumulation of ant lineages at È100 Ma, either toward the end or immediately following the radiation of the angiosperms (Fig. 1B). These analyses indicate that ant diversification closely tracks the rise of angiosperm-dominated forests, between the Early Paleocene and the Late Cretaceous, 60 to 100 Ma (21–24).

G. O. Poinar, Jr., et al. A Fossil Bee from Early Cretaceous Burmese Amber, Science 314, 614 (2006)

-We report here fossil evidence of bees in the Early Cretaceous.
The fossil bears several derived features of bees as well as morphological structures (e.g., branched hairs) presumed to be
associated with pollen collection.

-Palynomorphs obtained from the amber beds where the fossil originated have been assigned to the Upper Albian [~100 million years ago (Ma)] of the Early Cretaceous (4).

-M. burmensis establishes that many traits of extant bees were present by ~100Ma, near the time of the origin of the eudicots [120 to 125 Ma (3)

-younger. The small size of Melittosphex indicates that at least some of the earliest bees were minute. This is consistent with the small sizes reported for some Early Cretaceous flowers (6).

-M. burmensis exhibits traits unique to bees (branched hairs, absence of hind-leg strigil, and absence of hind-tibial spines) as well as groundplan features of apoid wasps (paired mid-tibial spurs and slender hind basitarsus). This mosaic of wasp and bee traits is to be expected from an early, transitional form that bridges the gap between extant bees and crabronid wasps.

The history of early bee diversification based on five genes plus morphology
Bryan N. Danforth†, Sedonia Sipes‡, Jennifer Fang§, and Sea´n G. Brady
PNAS 2006

-angiosperms). We reconstructed a robust phylogeny of bees at the family and subfamily levels using a data set of five genes (4,299 nucleotide sites) plus morphology (109 characters). The molecular data set included protein coding (elongation factor-1alpha, RNA polymerase II, and LW Rhodopsin) as well as ribosomal (28S and 18S) nuclear gene data.

-analyses yielded a single well supported family-level tree topology that places Melittidae as a paraphyletic group at the base of the phylogeny of bees.

-The earliest branches of bee phylogeny include lineages that are predominantly host–plant specialists, suggesting that host–plant specificity is an ancestral trait in bees. Our results suggest an African origin for bees, because the earliest branches of the tree include predominantly African lineages. These results also help explain the predominance of Melittidae, Apidae, and Megachilidae among the earliest fossil bees.

-currently bees are divided into seven extant families: the longtongued (LT) bee families Megachilidae and Apidae and the short-tongued (ST) bee families Colletidae, Stenotritidae,Andrenidae, Halictidae, and Melittidae sensu lato (s.l.) (9). Colletidae is widely considered the most basal family of bees (i.e., the sister group to the rest of the bees), because all females and most males possess a glossa (tongue) with a bifid (forked) apex, much like the glossa of an apoid wasp (18–22).

-Placing the root between Colletidae and the rest of the bees yields the Colletidae basal topology, whereas placement of the root node near or within Melittidae s.l. yields the Melittidae-LT basal topology. The biological implications of these alternative topologies are radically different.
The Colletidae basal topology implies an Australian and or South American origin for bees and suggests the earliest bees were a mix of floral generalists and specialists. Melittidae-LT basal implies anAfrican origin for bees and indicates that the earliest bees were likely to have been floral specialists. These alternative topologies also have implications for understanding the fossil record and antiquity of bees.

-Addition of morphology to the molecular data set did not alter the relationships among families obtained in the combined molecular data set.

-This study establishes phylogenetic relationships among bee families and subfamilies with high levels of support. Our results unambiguously support the Melittidae-LT basal topology.

-The Colletidae basal topology is more widely accepted because of the perception that the bifid glossa of Colletidae is a plesiomorphic trait shared with apoid wasps. This hypothesis appears in numerous publications but is rarely supported by characters other than the overall appearance of the glossa.

-the Melittidae-LT basal hypothesis has been largely overlooked in the bee phylogenetic literature. Among the most convincing morphological characters that support the tree presented herein is the morphology of the midcoxa.
Michener (32) discovered that in apoid wasps, Melittidae s.l., and LT bees, themidcoxa is exposed, whereas in the remaining ST bee families, the upper portion of the midcoxa is internal and hidden beneath the mesopleuron (a condition described as ‘‘hemicryptic’’). The hemicryptic condition is a unique and unreversed character congruent with monophyly of Andrenidae, Halictidae, Colletidae, and Stenotritidae (Figs. 1 and 2), thus strongly supporting the Melittidae-LT basal topology.

-The hypothesis that Melittidaes s.l. represents the earliest branch(es) of bee phylogeny suggests an African rather than an Australian or South American origin for the bees. Melittidae s.l. is absent from Australia and South America, and Africa is the only continent where all major lineages (e.g., families) of Melittidae s.l. occur (20). Meganomiidae are restricted to Africa, and for Dasypodaidae and Melittidae sensu stricto (s.s.).

-Host–plant specialization is widespread within Melittidae s.s., including Melitta, Rediviva, Redivivoides, and Macropis. All species of Macropis are narrow host–plant specialists on oil-producing plants in the genus Lysimachia (Primulaceae; ref. 35), and all species possess modified legs for collecting and manipulating viscous floral oils.

-Given the placement of Melittidae s.l. as a paraphyletic group at the base of the tree, our results indicate that host–plant specialization is the primitive state for bees.

-abundance of Melittidae s.l., Apidae, and Megachilidae in the oldest deposits, such as Eocene (Baltic) amber (22, 38) and Cretaceous amber from New Jersey (39–41).

-In contrast, ST bee families, such as Halictidae, are much less well represented in the Eocene, and representatives of Andrenidae and Colletidae are completely absent in the fossil record up until the Miocene (42, 43).

-Outgroups included representatives of two of the four apoid wasp families, Crabronidae and Sphecidae (51).

The rise of the ants: A phylogenetic and ecological explanation
Edward O. Wilson*† and Bert Ho¨ lldobler
PNAS 2005

Phylogenomic analysis reveals bees and wasps (Hymenoptera) at the base of the radiation of Holometabolous insects
Joël Savard,1 Diethard Tautz,1 Stephen Richards,2 George M. Weinstock,2 Richard A. Gibbs,2 John H. Werren,3 Hervé Tettelin,4 and Martin J. Lercher5,6,7
Genome Research 2006

-Here, we utilize emerging genome projects to assemble and analyze a data set of 185 nuclear genes, resulting in a fully resolved phylogeny of the major insect model species. Contrary to the most widely accepted phylogenetic hypothesis, bees and wasps (Hymenoptera) are basal to the other major holometabolous orders, beetles (Coleoptera), moths (Lepidoptera), and flies (Diptera) (monophyly of these major orders is shown).

-A close relationship between Diptera (flies) and Lepidoptera (moths) within the long-recognized Mecopterida assemblage is generally recovered. However, the affinities of Coleoptera (beetles) and more particularly of Hymenoptera (wasps and bees) (Castro and Dowton 2005) remain elusive. In the most widely accepted phylogenetic hypothesis (Kristensen 1999; Whiting 2002b), a preference is given to a sister-group relationship between Hymenoptera and Mecopterida, while Coleoptera are placed at a more basal position as a sister group to the Neuropterida, another long-recognized assemblage.

-To resolve the phylogenetic relationships of the major holometabolous orders, we adopt a phylogenomic approach, utilizing a large number of nuclear genes to maximize phylogenetic signal over noise (Eisen and Fraser 2003; Rokas et al. 2003; Delsuc et al. 2005; DeSalle 2005; Philippe et al. 2005a). Such approaches, based on the simultaneous analysis of a large number of nuclear genes, have already been shown to be a promising route to understand deep metazoan relationships (Dopazo and Dopazo 2005; Philippe et al. 2005b).--> using EST's

-analysis focuses on six holometabolous model species, for which large scale sequencing projects are available or in progress.
-two dipterans (the fruit fly Drosophila melanogaster and the mosquito Anopheles gambiae)
-one lepidopteran (the silk moth Bombyx mori)
-one coleopteran (the flour beetle Tribolium castaneum)
-two hymenopterans (the honey bee Apis mellifera, and the sibling parasitic wasp species Nasonia vitripennis and Nasonia giraulti).
We further include one orthopteran (the grasshopper Locusta migratoria) and one hemipteran (the pea aphid Acyrthosiphon pisum), both of which are uncontested outgroups to the holometabolous insects based on morphological and molecular markers

-we assembled the remaining sequences into a concatenated alignment of 33,809 amino acid positions from 185 nuclear genes (most genes included here perform housekeeping functions).

-This data set supported the topology in Figure 1 regardless of the phylogenetic methodology (maximum likelihood [Guindon and Gascuel 2003], Bayesian [Yang and Rannala 1997], or maximum parsimony [Felsenstein 2004]), with nearly 100% bootstrap support or 100% posterior probabilities in each case.
The previously recognized close relationship of Diptera and Lepidoptera is recovered and thus substantiated. However, Hymenoptera and not Coleoptera is the most basal of the four major holometabolous orders.

-The Mecopterida, encompassing Diptera (flies) and Lepidoptera (moths), seem now more closely related to Coleoptera (beetles) than to Hymenoptera (wasps and bees).

-Why was the basal position of hymenopterans not discovered in previous molecular phylogenetic studies?
A plausible explanation is the lack of resolution power of single molecules when radiations are old or compressed in time (Rokas et al. 2005). Because the phylogenetic split in question occurred at least 275 million years ago (Mya) (Ponomarenko 2002; Rasnitsyn 2002), analyses based on a single molecule (e.g., 18S rRNA) did not provide sufficient resolution (Whiting 2002a). While 60% of the 185 protein alignments analyzed here were better explained by the tree in Figure 1 than by the previously assumed tree (based on likelihood comparisons), only two proteins supported the basal position of Hymenoptera with a bootstrap support >50% when analyzed individually

-Accordingly, a consensus tree based on single gene tree reconstructions yielded the same topology as in Figure 1, but without strong bootstrap support (Table 1).

-The present analysis thus supports the notion that concatenated sequence trees provide more resolution than consensus gene trees (Rokas et al. 2003; Gadagkar et al. 2005): Combined analysis of a large number of sequences was necessary to resolve the deep evolutionary relationships among holometabolous orders.

-This study highlights the importance of selecting close outgroup species, and the necessity to test the influence of an alternative outgroup choice.

-we note that phylogenies based on 18S rRNA sequences also yielded a basal Hymenoptera among holometabolous insects, although not with a credible level of support

Recent and simultaneous origins of eusociality in halictid bees. Brady et al 2006 Proc.Biol.Sci.

Eusocial organisms are characterized by cooperative brood care, generation overlap and reproductive division of labour. Traits associated with eusociality are most developed in ants, termites, paper wasps and corbiculate bees; the fossil record indicates that each of these advanced eusocial taxa evolved in the Late Cretaceous or earlier (greater than 65 Myr ago). Halictid bees also include a large and diverse number of eusocial members, but, in contrast to advanced eusocial taxa, they are characterized by substantial intra- and inter-specific variation in social behaviour, which may be indicative of more recent eusocial evolution. To test this hypothesis, we used over 2400 bp of DNA sequence data gathered from three protein-coding nuclear genes (opsin, wingless and EF-1a) to infer the phylogeny of eusocial halictid lineages and their relatives. Results from relaxed molecular clock dating techniques that utilize a combination of molecular and fossil data indicate that the three independent origins of eusociality in halictid bees occurred within a narrow time frame between approximately 20 and 22 Myr ago. This relatively recent evolution helps to explain the pronounced levels of social variation observed within these bees. The three origins of eusociality appear to be temporally correlated with a period of global warming, suggesting that climate may have had an important role in the evolution and maintenance of eusociality in these bees.

Micro-morphology of the ovipositor in Hymenoptera and evolution from phytophagous Symphyta to parasitoid Apocrita. Nenon et al. 1995 C R Acad Sci III (Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie)

The ovipositor of 1 Symphyta and 12 primitive parasitoid Apocrita belonging of the family of Ichneumonidae has been studied with the scanning electron microscope (SEM) and for 2 species, semi-thin sections were used. The study shows the presence of closed trachea in the 3 pairs of valvulae and a secretory system in the 2 pairs of valvulae interlocked into a piercing stylus. We discuss the role of trachea and a secretory system leading to excretory pores on the lancets of valvulae which occupy very precisely the site of sensory chemoreceptors known in more advanced species lacking this secretory system. The micromorphological data support the phylogeny within Hymenoptera, from Symphyta to primitive parasitoid Apocrita.

Castro et al 2006 Invert Syst. Molecular analyses of the Apocrita (Insecta : Hymenoptera) suggest that the Chalcidoidea are sister to the diaprioid complex

Despite recent efforts, hypothesised phylogenetic relationships among apocritan wasps remain unresolved. In this study, molecular analyses were employed to analyse a dataset that included the 16S, the 28S and the COI genes of 87 apocritan representatives. Partial sequences of the 18S gene were also generated and added to this dataset. The topological effects of outgroup choice, method of phylogenetic analysis, and inclusion of the 18S data were systematically investigated, with particular focus on the relationship of the Chalcidoidea with other members of the Proctotrupomorpha (Platygastroidea, Proctotrupoidea, Cynipoidea). We report that ingroup topology was sensitive to the choice of outgroup, the method of phylogenetic analysis, and inclusion of 18S data. However, the Proctotrupomorpha were always monophyletic, and the Chalcidoidea were recovered, in every analysis except one, as the sister to the diaprioid complex (Diapriidae + Monomachidae + Maamingidae). The single exception, where the Chalcidoidea + Platygastroidea were recovered, utilised a more distant outgroup (Symphyta : Cephidae : Hartigia), maximum parsimony, and excluded the 18S data. Our results suggest the Chalcidoidea + (Diapriidae + Monomachidae + Maamingidae) relationship is more likely.