Grimaldi and Engel 2005
Current Views on Insect Diversity
Mina Krenz Dan Chou
Phylogenomics resolves the timing and pa@ern of insect
evolutionMisof B. et al 2014
Why Study Insect Phylogeny?
• Insects represent one of the earliest animals to make their way to terrestrial and aquatic environments
• Due to having a multitude of species, the phylogeny of insects are still well debated to this day
• Must reconstruct timelines of insect diversification in order to understand the changes in their physiology and morphology
Summary of the methods• 1478 nuclear genes from 144 extant taxa • More than 2.5 gigabases from each of the 103
species they studied • Estimating divergence events via 37 fossil records • Maximum Likelihood of mutations in DNA and
amino acids (rather than maximum parsimony)
Boot-‐‑Strapping• Acts as a resampling method in statistics • Selects a number of base pairs to see how sensitive
results are to exclusion of some data. • Resampling data to see how robust and strong it is
against randomization. • See conflict in data by providing: confidence
intervals, variance, errors, etc.
Paleoptera
Relationship between Odonates and Ephemeroptera
• The data indicates that Odonata and Ephemeroptera are nested within the Paleoptera
• However, this analysis is supported by a low boot-strapping
• What might this mean? o Odonates and Ephemeroptera possibly paraphyletic?
• Why is it difficult to determine the relationships in Paleoptera?
Relationship between Odonates and Ephemeroptera
• Paleoptera only have two extant lineages, even though they derive from all the way back in the Carboniferous
• Most likely Odonata and Ephemeroptera divided shortly after Paleoptera and Neoptera diverged, so huge variance between two Orders
• Long time span for Ephemeroptera and Odonata to diverge through gene mutations
NeopteraPolyneoptera, Holometabola/Endometabolous and
Paraneoptera***
Holometabolous• Strong statistical support for the well-nested group
of Holometabolous • High diversity of Hymenoptera, Diptera, and
Lepidoptera in early Cretaceous
Polyneoptera• Previous study supported the monophyly in groups
such as Hexapoda, Insecta, Pterygota, Neoptera, Paraneoptera, and Holometabolous
• However, there was weaker support for a monophyletic Polyneoptera (Kjer et al 2006)
Polyneoptera• Misof et al strongly support the monophyletic group
of the Polyneoptera • Boom in diversity of Blattodea, Mantodea, and
Plasmodea in Permean extinction.
Polyneoptera
Holometabolous/Endopterygota
Paraneoptera• The results suggest a diverge of Psocodea from the
rest of the Paraneoptera, forming a paraphyletic group
• The results show that Psocodea in fact a sister taxa to the Holometabolous
• Yet this claim does not have statistical support • Why include this data if it is not backed?
Age of Psocodea Taxa?• The study claims that that parasitic lice (Menopan
and Pediculus) arose in around 53mya with the emergence of the avian and mammalian taxa.
• However, their analysis looks at the crown clade, rather than the stem clade from the remaining
• Stem shows an arrival of parasitic lice ~130 mya, at the arrival of feathered theropod dinosaurs
Food for Thought• In your opinion, how to these results compare to
what has been presented in class/in the book (i.e. what critiques do you have for this study)?
• What other data or tests could have been used to make this study more reliable?
• Study of genomics is still a fairly new field of science • Science based on certain assumptions and
interpretations of the data; continuously changing and growing
Gullan and Cranston, 2014
Food for Thought• What evolutionary/environmental factors may have
given rise to these diverse groups?
Phylogeny of the Ants: Diversifica6on in the Age of Angiosperms
Moreau C.S., Bell C.D., Vila R., Archibald B., Pierce N.E.
Ants
• Key roles in symbio6c interac6ons • Soil Aera6on • Nutrient cycling • Dominant in terrestrial landscape: – 11,800 species – evolu6onary history poorly resolved
Main points
• Extant ants arose much earlier than previously proposed: 75-‐125 mya
• Began to diversify late Cretaceous – Early Eocene – 60-‐100 mya
• This 6me period corresponds with the rise of angiosperms and many herbivorous insects
Past phylogenies of Family Formicidae
• Past phylogenies proposed using morphological traits and molecular data with less data
• This phylogeny constructed from large-‐scale molecular data – 4.5 kb of sequence data – Six gene regions from 139 of 288 extant genera
• Represents 19 of 20 subfamilies
Sta6s6cal Analysis
• Maximum likelihood bootstrap • Bayesian posterior probabili6es • Maximum parsimony bootstrap
Major lineages in Formicidae
• Three main clades: – Leptanilloid (sister taxon to all other ants) • One subfamily: Leptanillinae
– Poneroid • 5 subfamilies • Amblyoponinae lacked support
– Formicoid • Contains remaining 13 subfamilies
Monophyly • 14 recovered as Monophyle6c with strong support – Leptanillinae (100%)
• Early morphological phylogenies do not show this at basal posi6on • Basal posi6on shows early tergosternal fusion of 3rd & 4th abdominal segments, lost secondarily • These characters are labile/homoplasious
• 19 recovered as monophyle6c • Cerapachyinae paraphyly
Bolton = Proposed “poneromorph” clade
-‐Amblyoponinae -‐Ectatomminae -‐Heteroponerinae -‐Paraponerinae -‐Ponerinae -‐Procer6inae
These results exclude Ectatomminae and Heteroponerinae, but add Agroecomyrmecinae
-‐Represented by Tatuidris Tatusia
Bolton = Proposed “poneromorph” clade using morphological analyses
-‐Amblyoponinae -‐Ectatomminae -‐Heteroponerinae -‐Paraponerinae -‐Ponerinae -‐Procer6inae
These results exclude Ectatomminae and Heteroponerinae, but add Agroecomyrmecinae
Historical placement of Heteroponerinae and Ectatomminae • Heteroponerinae in formicoid clade is unexpected – Historically in poneromorph clade – Same goes for Ectatomminae (closely related to Heteroponerinae)
Fossil record
• Oldest reliable fossils containing Formicidae are ~100 million yrs. old from early cretaceous in French & Burnese ambers
• Implies earlier history than expected of Formicidae
• Results show an even earlier history…
140-‐168 Million years old! Much older than previous es6mate based on fossil record
Previous studies showing early history of Formicidae
• Previous studies by Brady and Ward used molecular data to arrive at an es6mate of 130-‐140 Million years old – But…. Although these are similar dates the Moreau et al. study used: • Wider sampling • Addi6onal fossils
à Leads to an even older es6mate! (140-‐168 mil years old)
Results • Diversifica6on of major Formicidae lineages ocurred: – beginning of Early Paleoceneto Late cretaceous (60-‐100 Mya)
• Ancestors of major subfamilies present 75-‐125 mya
• If they were present much earlier, why did they take so long to diversify?
• Previous fossil record indicates later evolu6on
Correspondence with Angiosperm radia6on
• Rise in Angiosperm dominated forests was essen6al to the diversifica6on of ants – Why would this happen?
Discussion
Given the importance of plants in determining the 6ming of evolved traits in insects, as well as human’s adverse impact on nature (eg: deforesta6on), is it possible that insect evolu6on is being dampened? Would insects be bemer off without humans or are all organisms interconnected and important for others to thrive, despite some downfalls?
Lineages through 6me plot
• LTT plot: Accumula6on of ant lineages around ~100 (following angiosperm radia6on) – Also seen in Coleopteran & Hemipteran diversifica6on
Is there something wrong with the way this Histogram was constructed?
Are LTT graphs a good method for researchers to infer phylogene6c rela6onships? Why or why not?
Why the correla,on between Angiosperm radia,on and diversifica,on of Formicidae?
• Forests are more diverse – Wider array of habitats
• Expansion of herbivorous insects – Provided direct food source – Indirect food source: honeydew – Shio in diet à evolu6on of social behaviors
Significance?
• Evolu6onary inves6ga6on of life history, ecology, biogeography in order to: – Observe pamerns of diversifica6on and distribu6on of this dominant group of insects
• This highlights need for conserva6on of ant habitats to foster biodiversity to further research poorly understood evolu6onary history
The Fossil record and Macroevolu6onary history of
beetles Smith D.M. and Marcot J.D.
Main points • Compiled a database of
global beetle fossil data in order to study evolu6onary history
• Polyphaga responsible for most taxononmic richness of beetles – Also increase in diversifica6on rate in Cretaceous like Formicidae, but not due to Angiosperm radia6on
• Observed mechanisms that inhibited beetle ex6nc6on rather than mechanisms promo6ng specia6on
Polyphagan vs. Non-‐Polyphagan diversifica6on
• Degree of dietary varia6on and specializa6on within subgroups in Polyphaga – Algae, fluid feeders, carnivores, xylophages
• Non-‐polyphagans first to appear in fossil record – Reach peak of family richness in Triassic – Jurassic: low origina6on rates and higher ex6nc6on rates than Polyphaga
• Polyphagans surpass richness of non-‐polyphagans in Jurassic – Established early and longlived (family ex6nc6on rate of zero)
Non-‐polyphagans reach family richness peak
Polyphagans diversifica6on rate surpasses that of non-‐polyphagans (who have a higher ex6nc6on rate in this 6me period)
Increase in diversifica6on rate of Polyphagans
Should this middle-‐cretacean increase in the diversifica6on rate of Polyphagans be amributed to the rise in Angiosperms during the same 6me period? Like that of the Ant paper?
Origin of non-‐polyphagans
Amber deposits
• Instead of amribu6ng this to Angiosperm radia6on, Smith and Marcot connect this pulse of Polyphagan origina6on to: – First ocurrence of beetle-‐bearing amber deposits in fossil record
– They used different types of fossils in their database: lacustrine deposits
Why Polyphaga beetles may not be as suscep6ble to ex6nc6on
• Ability to change geographical distribu6on in response to climate change – Diet
Discussion
Why must phylogenies always be regarded as working hypotheses and considered with a certain level of scru6ny?
References• Main Papers:
o Misof et al. 2014. Phylogenomics resolves the timing and pattern of insect evolution. Science 346.620: 763-767
o Moreau C.S., Bell C.D., Vila R., Archibald S.B, Pierce N.E.. 2006. Phylogeny of the Ants: Diversification in the Age of Angiosperms. Science 312: 101-104.
• Resources: o Grimaldi D. and Engel M.S. 2005. Evolution of the Insects. Cambridge
University Press: New York. o Kjer K.M. Carle F.L. Litman J., and Ware J. 2006. A Molecular Phylogeny of
Hexapoda. Arthropod Systematics & Phylogeny 61(1): 35-44. o Smith D.M and Marcot J.D. 2015. The fossil record and macroevolutionary
history of the beetles. Proc. R. Soc. B 282: 1-8.
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