Home Economics American Trypanosomiasis Chagas Disease, Second Edition: One Hundred Years of Research
Tribe: Triatomini (genera: Dipetalogaster, Eratyrus, Hermanlentia, Linshcosteus, Panstrongylus, Paratriatoma, Triatoma)
The Triatomini is the most speciose of the tribes of Triatominae, with the widest geographical distribution covering a wide variety of ecotopes although the majority seem naturally associated with rupicoline habitats. The original tribal and generic concepts are morphological7,57 although a number of phylogenetic studies now offer extensive support for these concepts.56,58-60
Phylogenetic analyses using nuclear or mitochondrial gene fragments generally indicate that the Triatomini form three main clades that are broadly consistent with their geographical distribution: the Triatoma of Central and North America (and the Old World species) (i.e., north of the Amazon region) with which Dipetalogaster, Eratyrus, Linshcosteus, Paratriatoma, and Panstrongylus are usually clustered; the Triatoma of South America, i.e., south and east of the Amazon region (except for T. maculata; and Hermanlentia has not yet been included); and representatives of the dispar complex that occur mainly along the Andean cordillera from Venezuela to Bolivia (i.e., west of the Amazon region). Perhaps significantly, all species of all genera so far examined that form the “northern clade” (except for T. lecticularia) show multiple X chromosomes, whereas those of the southern clade generally show single X chromosomes.61 Of the exceptions, T. tibiamaculata and T. vitticeps, both Brazilian species, show two and three X chromosomes, respectively, and often cluster with the northern Triatomini in phylogenetic analyses. The other exceptions are species of the spinolai complex (spinolai, gajardoi, eratyrusiformis, breyeri) that show two or three X chromosomes61,62 and often cluster apart from others of the southern clade of Triatomini. The morphological similarities that placed these species as the spinolai complex,7 together with the recent karyotype studies, lend support to the concept of these species forming a separate genus: Mepraia.63
Within the northern Triatomini, several other concerns have been raised. The genus “Meccus” was originally proposed for some members of the phyllosoma complex, which were subsequently reduced to subspecific rank by Usinger57; these subspecies were then divided and raised to specific rank by Lent and Wygozinsky7 and grouped as the phyllosoma complex. The genus was re-erected by Hypsa et al.56 but without including all species that had been assigned to the phyllosoma complex, nor including T. dimidiata which appears very closely related by phylogenetic analyses.31,64-67 The phylogenetic approach to sustain such a genus56 might be questionable because the terminal entities are not reproductively isolated. Their interfertility has been demonstrated many times and recently confirmed by a molecular marker analysis on natural populations.68 Thus, according to the Hennigian and to the biological type of species (see Table 6.5) the members of this genus constitute one single polytypic species. Even as evolutionary species (see below) they are not convincing. Very small genetic divergences as based on functional or pseudogenic nuclear rDNA sequences were detected between them34’35’59’65’67’69 and the relatively higher number of nucleotide differences found in the mtDNA genes analyzed (16S, COI, and Cyt b)17,36,56,66,67 cannot be used to support species level’ as argued by Pfeiler et al.66 Recently’ the parallelism between the trees obtained with the pseudogenic 5.8S + ITS-2 and the functional ITS-2 sequences suggested that at least two derived lineages could be distinguished within this complex.34
Some concern is also valid for the idea of resurrecting the genus “Nesotriatoma” for the flavida complex of Triatoma (flavida’ bruneri’ obscura) which is a set of geographical populations assembled on the basis of morphological characters.7 Phylogenetic confirmation as a monophyletic clade has not been obtained using a sample including T. obscura and the dimidiata/phyllosoma complex of species.
The Old World species of Triatomini have also raised concern’ with the six species of Linshcosteus raised to tribal rank (as “Linshcosteusini”) by Carcavallo et al.70 on the basis of their uniquely Indian distribution and morphological characters not shared with most other Triatomini’ especially the abbreviated rostrum that does not reach the prosternal sulcus. However’ phylogenetic analyses tend to show Linshcosteus close to T. rubrofasciata56’71 which is believed to have been spread from North America to port areas throughout the Old and New World tropics and subtropics by its association with rats on sailing ships.71’72 The close proximity of Northern (New World) and Asiatic Triatoma has been recently observed also through morphometric techniques (contour of internal wing cells)’ as well as on the base of cytogenetics and new DNA sequence data.73
Table 6.5 Most common concepts of species
TYPO’ typological concept; BIOL’ biological concept; HENN’ hennigian concept; EVOL’ evolutionary concept; PHG I’ phylogenetic concept sensu Wheeler & Platnick; PHG II’ phylogenetic concept sensu Mishler & Theriot; /’ not relevant; (1) Carl von Linnaeus; (2) Earl of Buffon; (3) Ref. ; (4’5) Refs. [4J4]; (6’7) Refs. [75’76];
(8) Ref. ; (9) Ref. . Refs’ references; RI’ reproductive isolation; TD’ temporal dimension; ST’ stem species survival; SC’ exclusive use of synapomorphic characters; A’ allopatry; H’ hybridism; M’ exclusive use of morphological characters; S’ subjectivity.
|< Prev||CONTENTS||Next >|