Evolution of trap-jaw morphology in Ponerine ants

Robert Sutherland- Biology Dept., William Paterson University

Why ponerines?

• Ants (family Formicidae) contain numerous subfamilies, at least 3 of which have their own trap-jaw ants.

• Ponerines are interesting for several reasons:– Relatively ‘primitive’ ants:

maintain wasp-like stings, don’t recruit nestmates to food sourcessmall colonies with limited polymorphism

- Jaw specializations may compensate for lack of these more complex or derived features

Goals for this project

• Objectives of this project are to 1.) Describe genetic relationships among Odontomachus and a possible sister group Anochetus.

• 2.) Find and evaluate connections between both species nearest relative within the subfamily Ponerinae.

http://www.alexanderwild.com.

Range of Odontomachus Anochetus is very similar

http://www.antark.net/trap-jaw-ant-odontomachus-sp.html Cosmotropical

Example of convergent evolution.

Fig. 3 (blue slow twitch) blue: directly attached slow fibers (long sarcomeres); scale bar: 250 μm. Green: filament-attached slow muscle fibers (long sarcomeres); black lines indicate filaments; red: directly attached fast fibers (short sarcomeres)

Odontomachus

Trap-jaw ants: power-amplified jaw strikes and jaw-jumps

• Normal ‘slow’ twitch muscle, loaded against jaws locked open at 180 degrees.

• Odontomachus ants show predatory appendage strikes among the fastest in the animal kingdom, with jaw strike speeds between 78–140 mph.

• Strikes forces exceed 300 times the body weight of the ant, and can even be used by the ant to propel itself into the air.

Genera of main concern• Two genera with oversized, power-amplified jaws inserted in

the middle of the head capsule, which lock outward and strike toward each other. Anochetus jaws are generally more elongated and graceful , Odontomachus blunter and heavier.

Odontomachus and Anochetus

http://people.bu.edu/karitr/Genus/Odontomachus.html

http://zhelezyaka.com/images/2010/03/24/

General Morphological Differences

• In Anochetus the nuchal carina is evenly curved while it forms into a sharp edge medially in Odontomachus.

• Anochetus are small (total length of workers ca. 3.5 - 8.5 mm),

• Odontomachus are large (total length of workers ca. 7.5 - 16.0 mm)

Efficient Predators

• Kingdom: Animalia• Phylum: Arthropoda• Class: Insecta• Order: Hymenoptera• Family: Formicidae• Genus: Odontomachus

http://www.alexanderwild.com.

Using the jaws killing prey

http://www.alexanderwild.com.

Using the jaws removing intruders near the nest

Also used for normal nest activities(here seen moving larvae)

http://www.alexanderwild.com.

Jaw variation, evolutionary trends may become evident from the information within new

phylogeny (Multi-gene tree).

Hypothesis 1

• The first hypothesis that will be tested is that Anochetus and Odontomachus are sister groups, and form a monophyletic group.

Hypothesis 2

• The second hypothesis is that trap-jaws evolved once in two genera, but one of the two genera is nested within the other, making the first group a paraphyletic group.

• This means the more ancient species could be either Anochetus or Odontomachus

Hypothesis 1

• Hypothesis 2- two possible outcomes

(B and C)

• Current data has indicates towards Scenario (B and C)

Hypothesis 3

• The third hypothesis is that trap-jaws each independently evolved in a polyphyletic manner. (not pictured, multitudes of possibilities)

• Currently the evidence suggests that this is the least plausible hypothesis. The data from the multi-gene tree allows us to more conclusively reject Hypothesis 3

Methods• Molecular data was collected from existing collections

(GenBank) and genetic extractions were preformed. • PCR amplifications were made for HH3, CO1, LWrh, Wg,

28s genes. Approximately 3270 base pairs comprise our data set for 30 species of Anochetus and Odontomachus.

• DNA was extracted from 15 representative colonies of the ant species being studied. Standard PCR protocols and techniques have been utilized to amplify the targeted sequences of DNA. Existing primer sets were used to amplify portions of the all five genes HH3, CO1, LWRh 28S and wingless genes.

Methods

• The length of each gene amplification was; HH3 360 bp, LWRh 770 bp, CO1 810 bp, wg 480 bp, and 28s 850 bp.

• The combined data set was a total of 3270 base pairs.

Methods PCR

Methods

• Electrophoresis was performed through an agrose gel stained with ethidium bromide to make the DNA fluoresce. The PCR product is auto-sequenced off-site (Genewiz, Inc., West Brunswick, NJ) and then is assembled into two single-gene data sets.

Methods

• The data sets can then be assembled into larger multi-gene datasets. Data will be aligned using the MUSCLE algorithm (Chenna et al. 2004) as implemented in the Geneious software package.

Compiled Aligned 28s Sequences

Maximum Likelihood• The genetic divergence between these two species due to

neutral mutations can indicate the time elapsed since their last common ancestor

• This method brings in the concept of a molecular clock. Mutations are assumed to be rare and happen at a consistent rate. The Max likelihood program will create trees and score each branch based on Genetic statistical analysis of mutations (A,G purines T,C pyrimidines)

• Poor scoring trees are eliminated, the others trees are kept and using them the process is repeated many times.

• As of now all tree are not time calibrated

Advantages & Disadvantages Maximum Likelihood

• Strength- allows comparisons dealing topology branching patterns to be made with other trees.

• Strength 2- allows use of more realistic molecular-evolution models

• Weakness- time consuming to generate the trees.• The trees are made by assuming the mutation rate will

be relatively consistent. This assumption is often wrong.

• This inaccurate assumption contributes to the conflict between the hypotheses each tree supports.

HH3 TreeOdontomachus sp.

Odontomachus haematodus

O. desertorum

O. bauri

O. latidens

O. hastadus

Anochetus sp.

Odontomachus clarus

0.89

0.83

1

0.56

HH3 Hypothesis

• The hypothesis this tree (Fig.1) supports is that trap jaw ants evolved from an Odontomachus. In this tree Anochetus is nested within the Odontomachus clade. Making the relationship between Anochetus and Odontomachus paraphyletic. (Fig. 1 scenario B)

CO1 Tree

0.89

0.940.76

1 10.52

0.950.79

0.98

0.59

Platythrea strenuaPlectrotena ugandensis

Odontoponera transversaLeptogenys attenuata

Anochetus princeps

Anochetus emarginatusOdontomachus hastatus

Odontomachus cephalotes

Odontomachus ruficepsOdontomachus chelifer

Odontomachus bauriOdontomachus erythrocephalus

Odontomachus haematodus

Odontomachus opaciventrisOdontomachus clarus

Odontomachus brunneusOdontomachus ruginodis

CO1 Hypothesis

• The hypothesis that this tree supports is a Ponerine sister group with no trap jaws shares a common ancestor with Anochetus and Odontomachus who in this scenario are sister groups to each other. Each genera Anochetus and Odontomachus are monophyletic according this tree. (Fig.1 scenario A)

LWRh Tree

Odontomachus erythrocephalus

Plectrotena ugandensisPonera sp.

Ponera pensylavanica1

Odontoponera transversa

0.8

Odontomachus bauriOdontomachus haematodus

0.71Odontomachus brunneus

Odontomachus clarusOdontomachus relictus

Odontomachus ruginodis0.720.53

0.96

0.97

0.52

0.79

Platythrea strenua

Odontomachus opaciventrisOdontomachus chelifer

Odontomachus cephalotesOdontomachus ruficeps0.99

Odontomachus hastatusAnochetus sp.

Anochetus princepsLeptogenys attenuata

Pachycondyla villosa

Pachycondyla wasmaniiHypoponera opacior0.98

LWRh Hypothesis

• The hypothesis this tree supports is that Anochetus and Odontomachus are sister groups creating monophyletic clade (Fig.1 scenario A).

Wingless tree

0.75

1

1

1

111

0.65 0.690.88

1

0.58 0.96

0.77

.94

0.94

0.58

0.83

0.870.9

Wg Hypothesis

• The hypothesis this tree supports is that Anochetus and Odontomachus are sister groups creating monophyletic clade. (Fig.1 scenario A)

28s Tree

Odontomachus ruficeps RSOdontomachus haematodusOdontomachus relictusOdontomachus chelifer RS2Odontomachus clarus RS1

Odontomachus troglodytes RS1Odontomachus chelifer RS1Odontomachus opaciventrisO. troglodytesO. hastadusO. erythrocephalusO. ruginodisO. clarusOdontomachus sp.

Phrynoponera gabonesisPonera pennsylvanica

Pachycondyla commutataPachycondyla marginata

Anochetus princepsAnochetus madagascarensis

Anochetus emarginatusAnochetus mayri

11 1

11

1

0.99

0.97

0.87

0.69

0.86

0.85

0.85

0.860.870.6

28s Hypothesis

• This tree supports the hypothesis stating trap-jaws evolved once, but one of the two genera is nested within the other, making the relationship between the Anochetus and Odontomachus paraphyletic. A nested branching pattern. (Fig.1 scenario B)

Multigene TreeHypoponera OpaciorPlatyhyrea strenua

Leptogenys attenataPonera pennsylvanica

0.87

0.730.76

0.730.79 0.75

0.8

0.81

0.84

0.80.8

0.760.8 0.77

0.78

0.85

Anochetus madagascarensisAnochetus sp.Anochetus emarginatus

Anochetus mayriOdontomachus relictus

Odontomachus ruficepsOdontomachus cephalotes

Odontomachus cheliferOdontomachus haematodus

Odontomachus clarusOdontomachus opaciventris

Odontomachus brunneusOdontomachus ruginodisOdontomachus erythrocephalusOdontomachus bauri

Odontomachus hastadusAnochetus princeps

Plectotena ugandensisOdontoponera transversa

Final Hypothesis

• This tree supports the hypothesis stating that Anochetus is the more ancient genus and all Odontomachus species are nested within the Anochetus making the relationship between the two groups paraphyletic (Fig.1 scenario C).

• Goals for the project have been accomplished

• This information can serve as a basis for future experiments (formulating and testing new hypotheses regarding the evolution of trap-jaws ants).

Evolutionary InferencesA completed phylogeny will:• Combine morphological and molecular data. This can let us

see what the jaws of the nearest non-trap-jaw relative look like, giving us a strong ‘hint’ about the ancestral jaw shape.

• Note trends of change in size, shape, and force production in jaws over time.

• Allow us to estimate the rate of speciation in both groups, which seem to have diversified very rapidly (esp. in Anochetus)

• Angiosperm diversification may coincide with the radiation of these genera.

Summary

• A more accurate phylogeny expands our knowledge of the course of evolutionary development regarding this extreme trait.

• The final tree indicates that Anochetus is the older of the two genera and Odontomachus is nested within this clade creating a paraphyletic group.

Acknowledgements• Dr. Spagna for being always being positive and

patient• SURP funding for Rob Sutherland• Lab help from Edgar Valdivia, Mike Lora, and

Chris Satch• CfR funding for Rob Sutherland

SourcesBrady, S.G., Schultz, T.R., Fisher, B.L., Ward, P.S. (2006). Evaluating alternative hypotheses for the early evolution and diversification of ants 10.1073/pnas.0605858103. Proceedings of the National Academy of Sciences of the United States of America 103, 18172-18177.

Moreau, C.S., Bell, C.D., Vila, R., Archibald, B., Pierce, N.E. (2006). Phylogeny of the ants: diversification in the age of angiosperms. Science 312, 101-104.

Spagna, J. C., Vakis, A. I., Schmidt, C. A., Patek, S. N., Zhang, X., Tsutsui, N. D. and Suarez, A. V. (2008). Phylogeny, scaling, and the generation of extreme forces in trap-jaw ants. Journal of Experimental Biology 211, 2358-2368.

(Figure 3) Mandible movements in ants. ‘Learning about the Comparative Biomechanics of Locomotion and Feeding’, Liège July 26–27, 2000. Würzburg, Theodor-Boveri-Institut (Biozentrum), Würzburg, Germany