Ecology, Epidemiology, and Management of Whiteflies and Whitefly-transmitted Viruses in the United States
2: Analysis of nuclear orthologs and the mtCOI sequences resolves at least five cryptic species of the whitefly Bemisia tabaci (Genn.) cryptic species with some basis in microclimate associations
School of Plant Sciences; The University of Arizona Tucson, Arizona
The whitefly Bemisia tabaci cryptic and/or sibling species group comprises mitotypes important as plant virus vectors and pests in agriculture as well as relatively benign exemplars occupying wild/uncultivated habitats. Based on analysis of the mitochondria cytochrome oxidase I (mtCOI) gene, global mitotypes are known to affiliate as geographically structured phylogenetic clades, however, species boundaries have remained unresolved because the mtCOI marker is saturated with mutations (24-26%, globally). To address this impediment, distance analysis of nuclear orthologs was undertaken to resolve 14 lineages within and/or basal to the five recognized species clades (delimited by 2184 nuclear orthologs): American Tropics (AM-TROP) (1), Asia (ASIA) (3 lineages), Asia-Pacific-Australia (AS-PAC-AU) (6), North Africa-Mediterranean-Middle East (NAF-MED-ME) (1), or Sub-Saharan Africa (SSA) (1), and an ‘undefined’ sweet potato-Uganda (UGswpot) (1) and Italian highlands-T mitotype. Well-supported patterns of geographic isolation (rM=0.61, p< 0.05) influenced primarily by seasonal temperatures (rM=0.4702, p=0.00001) may explain at least some diversification among the cryptic species. Based on the nuclear ortholog estimates for species cut-offs, a global phylogeny was reconstructed for the same exemplars using the mtCOI marker) for whitefly specimens (n=1,923). The intragroup nucleotide (nt) divergence (corrected nt distances) was estimated using a 12.5% cut-off to estimate species boundaries that was consistent with five cryptic species predicted by the nuclear sequences. Additional cryptic species are expected following analysis of additional, divergent representatives. A better understanding of the B. tabaci cryptic species requires increased representation of non-agricultural species exemplars, validation of predicted habitat with genotype-phenotype character state associations.
