Systematics of the blackfly subgenus Trichodagmia ENDERLEIN (Diptera: Simuliidae:
Simulium) in the New World
The systematics of the New World subgenus Trichodagmia has been reassessed by employing an
integrated taxonomic approach based upon revisionary taxonomy, phylogenetic (cladistics) analysis, and
DNA barcoding. This subgenus included several species of great medical importance, which are all
morphologically very similar. The history of the taxonomy and classification of the subgenus
Trichodagmia has been put into context with other subgenera within New World Simuliidae, while
descriptions and keys to the identification of species in this subgenus are also given.
The subgenus Obuchovia is here considered a new junior synonym of Trichodagmia, and all its
constituents’ species are now placed in the ALBELLUM species group to represent a Palaearctic
element within this subgenus. Three new junior synonymies are here proposed: Simulium chiriquiense
FIELD is a synonym of S. ethelae DALMAT n. syn.; S. biuxinisa COSCARÓN & IBÁÑEZ-BERNAL is a
synonym of S. paynei VARGAS n. syn.; and S. keenani FIELD is a synonym of S. earlei VARGAS, MARTÍNEZ
PALÁCIOS &DÍAZ NÁJERA n. syn. A neotype is designated for S. lahillei (PATERSON & SHANNON) and a
lectotype for S. pulverulentum KNAB.1 Simulium falculatum ENDERLEIN is transferred from the
TARSATUM species group of to the CANADENSE species group based on the morphology of the
female genitalia. Two species, S. rivasi RAMÍREZ PÉREZ and S. oviedoi RAMÍREZ PÉREZ, are transferred
from the TARSATUM species group to the subgenus Psilopelmia based on the morphology of the male
gonostyle and the ventral plate. Keys to separate all species groups and species based on the adults,
pupae and larvae are also provided.
The phylogeny and classification of the subgenus Trichodagmia is delineated using a cladistic
analysis of 63 taxa based on males, females, pupae and larvae, including two species belonging to the
subgenus Aspathia and two species of the subgenus Simulium s.str. that served as outgroups. Analysis of
the original full data set [67 taxa and 67 characters] with multistate characters treated as unordered
under equal weights led to poorly resolved trees, with many polytomies within TARSATUM [= old
subgenus Hemicnetha] and CANADENSE [= old subgenus Hearlea]. Nonetheless, the ALBELLUM [=
old subgenus Obuchovia] and PICTIPES [= old subgenus Shewellomyia] species groups, and some clades
within the CANADENSE species group were well supported. In the most parsimonious cladograms,
the position of S. falculatum was problematic as it was placed basal to Trichodagmia. The position of S.
jeteri, albeit within the ORBITALE [= old subgenera Trichodagmia + Thyrsopelma of MIRANDA-ESQUIVEL
& COSCARÓN, 2001] clade, was also poorly resolved. This was certainly due to the numerous missing
data in these two taxa. Therefore, they were removed from the data set together with other taxa in
which three life stages (> 70% of characters) were missing (e.g. S. paracarolinae and S. tarsale). A second
analysis was then performed with 63 taxa and 67 characters. In this analysis, the Strict Consensus Tree
was better resolved and certain clades within the expanded concept of Trichodagmia (sensu SHELLEY et al.,
2010) were recovered as monophyletic with high support values. The ALBELLUM species group is
monophyletic in a sister-group relationship with the other species groups in Trichodagmia (sensu SHELLEY
et al., 2010). The ORBITALE species group clade was recovered as monophyletic by a unique
combination of seven characters with 89% bootstrap support. In this clade, all species close to S.
guianense s.l. were better diagnosed by a combination of four characters, one of which (male ventral plate
with a globular median process) was unique to this group. The position of S. hirtipupa is better resolved
in the latter clade by the presence of black spiniform setae in the frontoclypeus and thorax of the pupa.
In contrast, the TARSATUM and CANADENSE species groups were diagnosed by only four
and five characters, respectively. Within the CANADENSE species group only species with larvae
having sclerotized plates in the posterior region of the abdomen were well resolved. Species in the
TARSATUM group were homoplastic. The PICTIPES group is only diagnosed by homoplasies, but the
combination of these characters is unique to this clade (polythetic taxon). In general, this study supports
some of the taxonomic changes proposed in SHELLEY et al. (2010), in which the subgeneric-names
Hearlea, Hemicnetha, Shewellomyia, Trichodagmia + Thyrsopelma (sensu MIRANDA-ESQUIVEL & COSCARÓN,
2001) are treated as species groups within the subgenus Trichodagmia. Moreover, this study also supports
the proposal of Obuchovia as a junior synonym within the clade Trichodagmia to represent the
ALBELLUM species group.
The utility of the COI DNA barcoding methodology for identification of species in the subgenus
Trichodagmia and related taxa has been tested. In total, 24 morphospecies within the current expanded
morphological concept of Trichodagmia were analyzed. In addition, three species of the subgenus
Aspathia and 10 species of the subgenus Simulium s.str. were also included in the analysis because of their
putative phylogenetic relationship with Trichodagmia. Within the barcoding neighbour-joining tree, most
of the specimens were grouped together according to morpho-taxon (species groups and species).
Mean genetic distance amongst groups (morphospecies) averaged 11.2% (ranged 2.8-19.5%), whereas
intraspecific genetic divergence within morphologically distinct species averaged 0.5% (range 0-1.3%).
In known species complexes, maximum values of genetic divergence (3.28-3.79%) indicate the probable
presence of cryptic diversity. DNA barcoding achieved nearly 100% success in identifying all specimens
of the subgenus Trichodagmia and related taxa.
The existence of well defined groups within S. piperi, S. duodenicornium, S. canadense and S. rostratum
highlighted the possible presence of species complexes in these taxa. In addition, the suspected
presence of a sibling species in S. paynei and S. tarsatum among populations of Belize, Costa Rica, and
the USA is confirmed. The use of shorter barcodes (midi and minibarcodes) from specimens held in
collections was problematic with regards to the DNA quality and PCR success. However, in the cases
that a readable sequence was obtained, they were sufficient for reliable species identification. With
regards to the different extraction and preservation techniques tested, larvae preserved in diluted
Carnoy’s (10% acetic acid) provided full DNA barcodes. Furthermore, legs added directly to the PCR
mix from freshly collected individuals provided full length barcodes sequences. However, specimens of
more than 10 years old did not yield good PCR products. In short, I conclude that DNA barcoding in
combination with a morphological benchwork platform is an effective approach for identification and
delineation of species in the subgenus Trichodagmia, and the discovery of hidden diversity in this taxon.
|Qualification||Doctor of Philosophy|
|Award date||29 Mar 2011|
|Publication status||Published - 2011|
- nearctic region