1.2: Systematics and speciation of the ecologically important but taxonomically difficult ants in the Monomorium rothsteini species complex

Project overview

Sub-Project progress

Challenges

Monomorium is a highly abundant, widespread and diverse genus of ants. A recent revision of the genus in Australia highlighted several "species" which show considerable morphological variation. Although the degree of variation exhibited by some of these species is commonly associated with different but closely related species, rigorous morphological diagnosis that supported separate species proved difficult.

Historically ant species limits have been based primarily on worker morphology. However, this approach can be inadequate for groups where high levels of intra specific variation obscure differences between species. One of the more clear examples of this is M. rothsteini. This species is a widespread and dominant seed harvester throughout the tropical and arid zones of Australia. Currently described as a single species, the high level of morphological variation in clypeal margin shape, sculpture and pilosity suggests a cryptically diverse species complex.

Seeking solutions

This project will employ a diverse range of data to discover and describe new species in an ecologically important group of seed harvesting ants.

Approaches

Delimiting species in cryptically diverse taxa often requires information from a number of alternative sources. This project will use an integrative approach by combining morphological datasets with mitochondrial and nuclear DNA sequences, distributional information and ecology to form robust species hypotheses.

Collaboration

Throughout the project I will be working in close collaboration with other members of the Ant Project. Members of this group will contribute a diverse range of knowledge and skills in molecular sequencing, ant systematics, ecology and information technology.

Tools for Decision Makers

A key output of this project will be published species descriptions and identification tools (key, diagrams and images) that enable identification of species within the complex. This information will also be made available online via the CSIRO Australian Ants Online website.

It is anticipated that the methods and protocols for delimiting species in the M. rothsteini species complex can be transferred to other species complexes within Monomorium as well as other groups of ants.

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Sub-Project progress

 

January 2010

The primary focus during this period has been on data quality and report generation. Data has been checked for numerous classes of errors and these errors corrected.

Samples of Monomorium from a collecting trip to central Western Australia are being processed and added to previously collected data. Expansion to include nuclear markers is underway although results have yet to be analysed. The collection of morphological data has been expanded and preliminary analysis complete, relating the variation to biogeographic patterns.

Preliminary results, titled ‘Australian Monomorium: morphological plasticity or cryptic diversity?’, were presented by Kate Sparks at the Darwin 200: Evolution and Biodiversity conference (Darwin, September, 2009).

 

May 2009

Determining species boundaries within Monomorium ants

Ants belonging to the genus Monomorium are especially abundant in Australia’s arid zone; serious gaps exist in our understanding of species boundaries within these ants, making identifications difficult. Research on selected species of Monomorium has shown that while our current species concepts are essentially correct, the patterns of within-species variation in molecular and phenotypic characters are highly complex. This complexity involves differentiation at population-level but without emergent patterns at broader geographic scales. This is an unexpected result that will lead to new insights into the evolution of not only these specific ants, but also other groups occurring in arid Australia.

Samples of 32 Monomorium species have been assembled from museums and collections. Sequences have been generated and used to produce a preliminary phylogeny for the genus in Australia. Results from this analysis indicate that some of the previously recognized species groups are para- or polyphyletic. It is also clear that the genetic diversity within species of Monomorium is high and indicative of cryptic species.

To gain a better understanding of the species relationships, additional Monomorium species and nuclear markers will be added to the dataset resulting in a total of approximately 40 species and three genetic markers. The molecular dataset for the M. rothsteini complex will be expanded to incorporate sequences from a broader geographic range. The resultant molecular phylogeny will be analysed in combination with morphological data to begin forming hypotheses of species boundaries for the complex. A poster outlining the research project and TRIN objectives was presented at the Entomological Society of America Annual Conference in Reno, Nevada in November 2009.

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