Abstract
AbstractThe Bemisia tabaci complex in Ecuador was studied with respect to phylogenetic relationships and eco‐geographical distribution. Whitefly samples were collected from natural and agricultural environments in nine provinces of Ecuador (latitude, 2° N–5° S; longitude, 78°–81° W). Mitotypes were identified based on phylogenetic analysis of the 3′‐mtCOI‐tRNAleu region (832 bp) and corrected pairwise distance analysis. The distribution of mitotypes was modeled using MaxEnt, and their predicted niches were characterized according to environmental gradients. Four B. tabaci mitotypes were identified, of which three are endemic, herein ECU1–3, and the other is the introduced B mitotype. Mitotypes ECU1 (44%), ECU2 (0.74%), and ECU3 (1.47%) grouped in the American Tropics (AMTROP) species and diverged by as much as 10%, which was higher than previous estimates for the AMTROP clade of 7–8.6%. Although haplotypes of ECU1 and ECU2 are known from the American Tropics, this is the first report of the ECU3 mitotype, which may possibly be restricted to southern Ecuador. The distribution of the three ECU‐endemic mitotypes spanned the high‐altitude niches of the western slope of the Andes, rich in microclimates with variable temperature and humidity conditions. The non‐endemic B mitotype (47%) occurred only in the irrigated cropping systems located in hot and/or dry‐tropical ecological niches. Of the endemic mitotypes, ECU1 occupied the most ecological niches. Among variables contributing to ECU1 and B mitotype niche range assignments, the most significant to influence ecological range was rainfall. The B. tabaci endemic to Ecuador were more diverse with respect to mtCOI‐tRNAleu sequence than previously known, and occupied distinct microclimate niches suggestive of ecological resilience.
Highlights
Several COI sequences for whiteflies collected from cassava and other wild plant species were identified as Bemisia tuberculata (Bondar), and belonged to a distinct clade, itself a sister to the B. tabaci sibling species group
B. tabaci endemic to Ecuador, ECU1 was phylogenetically most closely related to a mitotype previously identified in Colombia, members of the ECU1 sister group (Fig. 1)
Among available mitochondrial cytochrome oxidase I gene (mtCOI) sequences, the ECU2 sister group was most closely related to B. tabaci haplotypes from Argentina and Brazil, identified more than fifteen years ago by mtCOI sequence analysis (Fig. 1; Viscarret et al 2003)
Summary
The whitefly Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) is hypothesized to represent a sibling or cryptic species group (Brown 2010, Gill and Brown 2010, Hadjistylli et al 2016). The major clades and species abbreviations are as follows: (I, II) sub-Saharan Africa (SSA), (III) North Africa-Mediterranean-Middle East (NAFMEDME), (IV) Asian-Australo-Pacific (ASAUSPAC), (V) Asia 2 (ASIA), and (VI, VII) American Tropics (AMTROP), with the most recent revision including minor changes in the previously proposed nomenclature (Brown 2010, Dinsdale et al 2010, Gill and Brown 2010, Boykin et al 2012, Hadjistylli et al 2016, Wosula et al 2017, Elfekih et al 2018, de Moya et al 2019) to account for newly discovered variants and update the geographical context of their phylogeographical distributions. Among the mitotypes represented within these major phylogeographic (mtCOI) clades, a relatively small number have been documented to cause damage to crop plants either by feeding or by transmission of plant viruses, and surprisingly, among these, only several have been characterized to any extent (Costa et al 1993, Bedford et al 1994, Rosell et al 1997, Demichelis et al 2005, Caballero 2007, Brown 2010), and include the mitotypes, Asia 2 (ASIA [IV]), B and Q (NAFMEDME [III]), SSA-I, and A (AMTROP [VI, and tentatively, VII]) (Brown 1992, Costa et al 1993, Brown et al 1995a, Byrne et al 1995, Brown and Bird 1996, Legg et al 2002, 2014, Horowitz et al 2005, MartinezCarrillo and Brown 2007, Dennehy et al 2010)
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