Further insight into reproductive incompatibility between putative cryptic species of the Bemisia tabaci whitefly complex

Abstract

The whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), with its global distribution and extensive genetic diversity, is now known to be a complex of over 35 cryptic species. However, a satisfactory resolution of the systematics of this species complex is yet to be achieved. Here, we designed experiments to examine reproductive compatibility among species with different levels of mitochondrial cytochrome oxidase I (mtCOI) divergence. The data show that putative species with mtCOI divergence of >8% between them consistently exhibited complete reproductive isolation. However, two of the putative species, Asia II 9 and Asia II 3, with mtCOI divergence of 4.47% between them, exhibited near complete reproductive compatibility in one direction of their cross, and partial reproductive compatibility in the other direction. Together with some recent reports on this topic from the literature, our data indicates that, while divergence in the mtCOI sequences provides a valid molecular marker for species delimitation in most clades, more genetic markers and more sophisticated molecular phylogeny will be required to achieve adequate delimitation of all species in this whitefly complex. While many attempts have been made to examine the reproductive compatibility among genetic groups of the B. tabaci complex, our study represents the first effort to conduct crossing experiments with putative species that were chosen with considerations of their genetic divergence. In light of the new data, we discuss the best strategy and protocols to conduct further molecular phylogenetic analysis and crossing trials, in order to reveal the overall pattern of reproductive incompatibility among species of this whitefly complex.

Global genetic diversity and geographical distribution of Bemisia tabaci and its bacterial endosymbionts

“…tabaci species complex members. Though few controversies did occur [65,66], reclassification based on the 3.5% and 4% genetic divergence revealed that 42 groups are clearly distinct (Fig 1).…”

Genome-wide analyses of the Bemisia tabaci species complex reveal contrasting patterns of admixture and complex demographic histories

“…These patterns were further confirmed by an ABBA-BABA test which identified signatures of introgression between MEAM1 and IO confirming previous studies reporting gene flow between IO and MEAM1 in the field in Réunion Island [ 62 ]. Furthermore, evidence of incomplete mating isolation among the more closely related members of the complex where mtCOI diverge by ≤ 7% has been repeatedly demonstrated [ 63 , 64 ]. Our results also show evidence of introgression between IO and MED in Réunion Island which had not been detected previously through the use of microsatellite DNA markers [ 20 ].…”

Species‐complex diversification and host‐plant associations in Bemisia tabaci: A plant‐defence, detoxification perspective revealed by RNA‐Seq analyses

“…Dinsdale et al (2010) proposed a general threshold of 3.5% for mitochondrial cytochrome oxidase I (mtCOI) DNA sequence divergence for species delimitation, which currently leads to the identification of at least 35 distinct species assigned to~11 major clades (Barbosa et al, 2014;Hu et al, 2014). With few minor nonconclusive exceptions, reproductive compatibilities' experiments confirm so far the accuracy of the cryptic species concept adding credibility to the mtCOI approach (Liu et al, 2012;Qin, Pan, & Liu, 2016).…”