Eyal is busy nowadays writing the next ISF grant for continued genomic work in the Cataglyphis social polymorphism system, and the lab is very busy with new projects and revisions of papers. No time to post news now!
This year, Eyal and Pnina represented the lab in SMBE and ESEB. Pnina presented a poster on her mutation rate study and Eyal gave a talk on the Solenopsis positive selection study (Mol Ecol 2018). We had lots of great opportunities for hearing excellent talks and interacting with colleagues and collaborators.
Here's a link to the video recording of Eyal's talk (starting on 1:12:00)
Pnina's paper was published in BMC Evolutionary Biology!
This is a demographic history study that developed from our collaboration with DeWayne Shoemaker. Pnina used a large dataset of RADseq from 300 population samples from two species of Solenopsis fire ants, from both their native and introduced ranges. The most valuable result is in dating the speciation of the two species, and showing that they did not have any substantial gene flow between them in South America in the past two million generations. This is in contrast to the extensive hybridization between them in the introduced range in the USA.
Our paper is online at Scientific Reports!
This was a collaboration led by Tali Reiner Brodetzki and Abraham Hefetz (TAU) to resolve species delimitation in the Cataglyphis niger complex. Previous studies identified three clades within this species complex: C. niger, C. savignyi, and C. drusus. The three were distinct monophyletic clades according to their mitochondrial haplotypes, and they also display distinct social colony structures: C. niger is polygyne, whereas C. savignyi and C. drusus are monogyne. In this new paper we show using RAD sequencing and population structure analysis of thousands of SNP loci that these three mitochondrial clades are not monophyletic in terms of their nuclear DNA. In fact, there is no detectable genetic divergence among them, and they form one un-differentiated population cluster in the STRUCTURE results:
We also conducted a maximum likelihood test for gene flow (using 3s) and rejected the null model of no gene flow between these clades. That is, there is significant evidence for gene flow between all these populations and between colonies of different social structure. Finally, we show that the spermatheca of polygyne queens with the C. niger mitotype contains mostly sperm with the C. savignyi mitotype. That is, polygyne queens mate mostly with males from monogyne colonies. Therefore, C. niger is one species that harbors a social polymorphism similar to other ants such as Solenopsis invicta and Formica selysi.
We do not know yet if the social polymorphism in C. niger is controlled by a supergene ("social chromosome") as found in the other two systems. C. niger is also distinct in that the social form is completely linked to the mitochondrial lineage. That is, daughter queens always inherit the social form of their mothers. This raises the intriguing possibility of maternal imprinting. It remains to be seen if this system will turn out to be genetically controlled as in the social chromosome systems, or rather epigenetically controlled.
Tal's paper was published in Scientific Reports!
We evaluated the benefit of using a haploid sample in a denovo genome sequencing project. We saw that the scaffolds assembled from a haploid samples were three times longer than those from a diploid sample! We also evaluated the benefit of using the RNA from the same haploid individual for transcriptome sequencing and alignment to the genome for gene annotation, but this did not provide a substential advantage relative to RNA from other samples.
This study can inform future genome projects in Hymenoptera, such as the GAGA project or in bees, wasps, or other haplodiploid species.