The Origin And Evolution Of Pollinating Fig Wasps In Ficus Altissima

In the long course of evolution, figs and fig pollinators form obligate symbioses, so called the ―one-to-one‖ rule. However, with the deepening of the research, some examples have been found to break the rule, such as the pollinators in Ficus altissima. In Ficus altissima, Eupristina altissima is the only pollinator known for long time. Another species of same pollinating genus, Eupristina sp. was found in F. altissima in 2003. Subsequently, some morphological characteristics in antenna, body colour, pollen pockets and coxal comb were found to discriminate the two species for females. It was further found that Eupristina altissima is an active pollinator, while Eupristina sp. is a ―cheater‖. But, it is difficult to tell the difference between the two males, either with the preferred COI genes of DNA barcode or direct observe the morphology.For this special case breaking the ―one-to-one‖rule, can we find more morphological diagnostic characters for the two species? Especially for males? How do those two species originate and evolve?To address above question, we has extracted the genomic DNA of female and male from the pollinators in Ficus altissima, by using the fast extraction and nondestructive extraction method respectively, and amplified the nuclear ITS2 and mitocontrial COI gene sequences. We want to confirm the mitochondrial COI species delimitation by nuclear ITS2, and furthermore to find more morphological diagnostic characters for two specie, especially for males, on the basis of the molecular identification. We downloaded sequences of other species of Eupristina, ITS2 sequences from NCBI; COI sequences from The Barcode of Life Data System, with the integration of our data. We aim at analyzing the base composition, base substitution rates, the genetic distance, the divergence time between species of Eupristina, and deciphering evolutionary relationship and the origin of the two species. Main results are listed as follows:1. Besides the antenna, body colour, pollen pockets and coxal comb, a newly found difference of the female between E. altissima and Eupristina sp. is that stigmatal peritremata of eighth urotergite of E. altissima small, width much shorter than the distance between the two stigmata peritremata; but stigmatal peritremata of eighth urotergite of Eupristina sp. large, width slightly longer than the distance between the two stigmata peritremata. Male of E. altissima hind tarsusslightly longer, last segment longer than its basitarsus; Male of Eupristina sp hind tarsus short and robust, last segment shorter than its basitarsus.2. ITS2 and COI gene evolutionary tree respectively showed that the two pollinators in Ficus altissima are sister species with closed genetic relationship.3. The base composition statistics showed that all the ITS2 sequences of Eupristina do not present base bias: average percentage of A+T is 45%; all the COI sequences of Eupristina presents base bias: average percentage of A+T is at least 74%;4. Base substitution analysis of ITS2 sequences showed that transition mostly occoured between T and C, and transversion number was average among the four kinds of circumstances; Base substitution analysis of COI sequences showed that transversion number was more than transition number,futher more, transversion of all was a transversion between thymine T and purine.5. The ITS2 genetic distance between species of Eupristina was 0.130-0.383. The ITS2 genetic distance whinin species of Eupristina was 0.001-0.007, except the pollinators in Ficus. Benjamina from Yun Nan, whose genetic distance whinin species was 0.039; The COI genetic distance between species of Eupristina was 0.045-0.317. The COI genetic distance whinin species of Eupristina was 0.000-0.018, except the pollinators in Ficus altissima from Hai Nan and Ficus drupacea from Yun Nan, whose genetic distance whinin species has exceeded the Barcoding limit, namely 2%.6. The ITS2 divergence time between E. altissima and Eupristina sp. in Ficus altissima from Hai Nan was 7.44 MYA; the COI divergence time was 3.47 MYA. Compared with the divergence time among the whole Eupristina, E. altissima and Eupristina sp. were involed in a speciation event.7. In Eupristina, the ITS2 divergence time between different species was longer than The COI divergence time, suggesting that nuclear genes diverged earlier than mitochondrial genes.