The Status ofLinshcosteusin the Triatominae (Hemiptera: Reduviidae)

Abstract

Of the 17 genera in Triatominae, only one, Linshcosteus, occurs exclusively outside the New World (India). Its relationship to the rest of the subfamily has been questioned, a question made urgent by the fact that many triatomines are vectors of the protozoan which causes Chagas' disease. Using a simple measure of similarity, we show that Linshcosteus is less similar to the other triatomine genera than each of them is to the others.

Triatominae (Hemiptera: Reduviidae): Systematic questions and some others

“…Are Triatominae polyphyletic (descended from more than two ancestors) or diphyletic (descended from two ancestors) or, as currently treated, monophyletic? These possibilities have been suggested (Schofield 1988(Schofield , 2000Schofield & Dolling 1993;Schofield & Dujardin 1999;Bargues et al 2000), and discussed by Carcavallo et al (1999Carcavallo et al ( , 2000; but the evidence is weak (see below, and Schaefer & Coscarón 2001), or controverted by other evidence (Hypša et al 2002).…”

“…This possibility has been suggested by many of those who believe Triatominae to be di-or polyphyletic, and who argue that those features of Linshcosteus that link it with Triatominae are merely features any reduviid must acquire if it is to feed on vertebrate blood; Linshcosteus, by this argument, is convergent with members of Triatominae. Schaefer & Coscarón (2001) discuss this possibility (but do not resolve it), as well as the further possibility that other members of the Triatominae are also included in this subfamily because of convergence, not common ancestry. Here again, phenetic evidence suggestsbut only suggests -that Linshcosteus is close to triatominae genera (Schaefer & Coscarón 2001); but again, I believe a cladistic analysis, not a phenetic one, will provide a more convincing answer.…”

“…Schaefer & Coscarón (2001) discuss this possibility (but do not resolve it), as well as the further possibility that other members of the Triatominae are also included in this subfamily because of convergence, not common ancestry. Here again, phenetic evidence suggestsbut only suggests -that Linshcosteus is close to triatominae genera (Schaefer & Coscarón 2001); but again, I believe a cladistic analysis, not a phenetic one, will provide a more convincing answer.…”

“…Several of those supporting the di-or polyphyletic origin of Triatominae believe Linshcosteus at least to have had a separate origin. An analysis of similarity does not quite support this idea (Schaefer & Coscarón 2001). More important, Hypša et al (2002) show with molecular data that Linshcosteus and T. rubrofasciata are sister groups and form a clade which "nests firmly within Triatomini" (quote from abstract).…”

“…The most evidence for polyphyly (actually, diphyly) has been gathered by Schofield & Dujardin (1999) in a paper not seen by Schaefer & Coscarón (2001). Schofield & Dujardin write, "Our working hypothesis considers the Triatominae to represent a polyphyletic assemblage of predatory reduviids" (p. 187); and, again, "In fact the Triatomini and Rhodniini appear to derive from different reduviid lineages, and now [why "now": did they once have more in common?]…”