Research Article |
Corresponding author: Mónica S. Iglesias ( iglesias.fcen@gmail.com ) Academic editor: Ernesto Rázuri-Gonzales
© 2022 Julieta V. Sganga, Daniela E. Sganga, Mónica S. Iglesias.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Sganga JV, Sganga DE, Iglesias MS (2022) Review and redescription of species in the brasiliana group of Smicridea (Rhyacophylax) (Trichoptera, Hydropsychidae, Smicrideinae): exploration of the utility of geometric morphometrics as a method for delimitation and characterization of species in the genus. In: Pauls SU, Thomson R, Rázuri-Gonzales E (Eds) Special Issue in Honor of Ralph W. Holzenthal for a Lifelong Contribution to Trichoptera Systematics. ZooKeys 1111: 389-412. https://doi.org/10.3897/zookeys.1111.80961
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The Smicridea brasiliana species group includes five species distributed in northeastern Argentina and Brazil: Smicridea (Rhyacophylax) brasiliana (Ulmer), S. (R.) weidneri Flint, S. (R.) vermiculata Flint, S. (R.) arobasis Flint, and S. (R.) nanda Flint. The original descriptions of these species and their placement in the brasiliana species group were mainly based on the morphology of the male genitalia. However, the fine structure of the internal sclerites of the phallus, which proved to be useful for species delimitation, was not analyzed at the time. In this contribution, we provide a detailed description of the male genitalia and the morphology of the head, and analyze the shape of the wings using geometric morphometrics. The analyzed species can be easily differentiated by the shape of the phallus, especially by the structure of the internal sclerites, the shape of the head in dorsal view, and the shape of the cephalic setose warts. Furthermore, the geometric morphometric approach allowed their separation through the wing shape. The preliminary analysis of these features suggests that the brasiliana species group is not natural but its monophyly should be further tested within the framework of a phylogenetic analysis of all the species of the subgenus Rhyacophylax.
Forewing shape, male genitalia, Neotropical, Smicridea (Rhyacophylax) atrobasis, Smicridea (Rhyacophylax) nanda, Smicridea (Rhyacophylax) vermiculata, Smicridea (Rhyacophylax) weidneri
Smicridea is the only genus of Smicrideinae present in the Neotropical region (
The Smicridea (Rhyacophylax) brasiliana (Ulmer, 1905) species group currently contains five species: S. brasiliana, S. weidneri Flint, 1972, S. vermiculata Flint, 1978, S. atrobasis Flint, 1983, and S. nanda Flint, 1983, that are distributed in northeastern Argentina and Brazil (
The morphology of the male genitalia has been extensively used for the delimitation of species in the order Trichoptera as a whole. Other characteristics of the adult morphology, such as the shape of the antennae and palps, the presence of ocelli, spur formula, shape and distribution of setose warts, and wing venation are usually used to identify families and genera (
In recent decades, the number of geometric morphometric studies in insects has increased in the literature. This methodology became a powerful tool to detect minimal shape variations which often are undetectable by traditional morphological studies and emphasizes differences between groups (
In the present work, we aimed to redescribe the species in the Smicridea brasiliana group offering a detailed description of the genital segments, especially the phallus, and provide non-genital characters for their identification. Additionally, we tested the use of geometric morphometrics for species delimitation. Integrative taxonomic investigations, which include traditional tools together with modern methodologies, are increasingly being implemented to solve species delimitation problems (
Specimens of Smicridea brasiliana, S. nanda and S. weidneri housed in the National Museum of Natural History, Smithsonian Institution, Washington DC (
The samples were collected in December 2004 and November 2013 using light and Malaise traps. The specimens obtained were fixed and preserved in 80% EtOH. Voucher specimens were deposited at the Museo Argentino de Ciencias Naturales (Buenos Aires, Argentina).
For identification and illustration of the specimens the abdomen was cleared using a hot 10% NaOH solution. Then the cuticle was rinsed in distilled water, neutralized with acetic acid, and mounted in a dish with glycerin for observation. Line drawings of the genital structures were produced using a camera lucida attached to a microscope. Line illustrations of the heads were constructed using photographs as templates, which were obtained with a digital camera fixed to a stereomicroscope. All the images were digitalized with Adobe Illustrator (v. 15.0.0 Adobe Systems Inc.).
For the description of the heads the following distances were measured (Fig.
Heads in dorsal view of the species of the brasiliana group A Smicridea (Rhyacophylax) brasiliana B S. (R.) weidneri C S. (R.) vermiculata D S. (R.) atrobasis E S. (R.) nanda. Abbreviations: CSL length of the coronal suture, IOD interocular distance, MEW maximum eye width, MHW maximum head width. Scale bar: 1 mm.
IOD interocular distance;
CSL length of the coronal suture;
MEW maximum eye width;
MHW maximum head width.
All the measures were taken using a stereomicroscope with a graduated eyepiece. The terminology used by
For the morphometric analysis, all the species included in the brasiliana group were used along with five additional species from the same subgenus, in order to increase the discriminatory power of the methodology.
The left forewings of males (n = 154) of Smicridea (Rhyacophylax) mesembrina (Navás, 1918) (n = 21), S. weidneri (n = 16), S. vermiculata (n = 22), S. (R.) spinulosa Flint, 1972 (n = 18), S. atrobasis (n = 18), S. (R.) vekona Oláh & Johanson, 2012 (n = 19), S. (R.) pampeana Flint, 1980 (n = 18), S. (R.) unguiculata Flint, 1983 (n = 20), S. nanda (n = 1), and S. brasiliana (n = 1) were dissected. Then, the removed wings were extended and mounted on a slide, using alcohol as medium, and covered with a coverslip. The alcohol was left to evaporate before taking photographs with a digital camera fixed to a stereomicroscope (two photographs were taken of each wing). Cartesian coordinates of ten landmarks of each wing (Fig.
Permutation tests for distances by species pairs (20,000 rounds of permutations) for the Mahalanobis (Table
Canonical variate analysis (CVA) was performed on aligned landmark coordinates and the specimens were reclassified to each species (jackknife method) to evaluate the effectivity of the discriminant analysis for assigning them to their own group using the software Past v. 4.02 (
The species S. nanda and S. brasiliana were excluded from all the statistical tests mentioned above due to an insufficient number of specimens.
A principal component analysis (PCA) with the consensus configurations of the species of the brasiliana group (S. brasiliana, S. weidneri, S. vermiculata, S. atrobasis, and S. nanda) was performed. In addition, the thin plate spline method was used to illustrate the transformations of the wing shapes compared to the consensus wing shape of the group. Mahalanobis distances between the mean shapes of each species of the brasiliana group were used to construct a dendrogram using the Unweighted pair-group method with arithmetic mean (UPGMA) with the software Past v. 4.02 (
For wing size analysis, centroid size (CS) was used as a measure of size and was computed as the square root of the sum of squared distances from all landmarks to the centroid of the landmarks configuration (
Subfamily Smicrideinae Schefter, 1996
Genus Smicridea Mclachlan, 1871
Smicridea (Rhyacophylax) brasiliana
(Ulmer), 1905: 107 [as Rhyacophylax brasilianus].
Argentina • 1 male; Misiones, Río Iguazú, camp. Nandu; 25 Feb. 1973; OS Flint Jr. det.;
Flint (1972) examined the type series of this species from the Ulmer collection (housed at the Zoologisches Museum Hamburg) where he found two mixed species, Smicridea (Rhyacophylax) brasiliana and another closely related species that he described as S. (R.) weidneri. The specimen we used for this redescription was collected in 1973 in Misiones province (Argentina) and identified by Dr. Flint. This specimen was borrowed from the
Adult male. General color of the body light brown. Length of the forewings: 6.3 mm (n = 1). Coloration of the forewings similar to the body, with a subapical transverse, sinuous, white stripe, and a white, rectangular spot at midlength of the costal margin.
Head
(Fig.
Male genitalia. Anterolateral margin of segment IX rounded and produced (Fig.
Male genitalia of Smicridea (Rhyacophylax) brasiliana A segments IX, X, inferior appendages and phallus, lateral view B segments IX, X and inferior appendages, dorsal view C tip of the phallus, lateral view (lateral spines removed) D tip of the phallus, dorsal view E tip of the phallus, ventral view.
This species seems to be related to S. weidneri and S. nanda. Genitalically, these species share the presence two pairs of elongate sclerites, dorsal and ventrad to the ejaculatory duct, which take different forms in the three species. Additionally, the morphology of the setose warts of the head of these species is similar, with the anterolateral setose warts bifid and the posterior ones triangular. Smicridea brasiliana can be distinguished by the presence of the elongate, sinuous, and pointed dorsal plate at the distal end of the ejaculatory duct, absent in the other two species, and the shape of the ventral plates that are spine-like, and the lateroventral ones that are subrectangular and pointed. Also, S. brasiliana has series of spines surrounding lateroventrally the end of the phallus, which are lacking in the other two species.
Argentina (new record), Brazil.
Smicridea (Rhyacophylax) weidneri
Flint, 1972: 238; 1966:8 [as brasilianus, distribution].
Argentina • 1 male; Misiones, Capiovy; 5 Apr. 1971; CM & OS Flint Jr. col.; paratype;
Adult male. Coloration of the body stramineous. Length of the forewings 4.5 mm (n = 16), coloration similar to that of the body, with two transverse, brown bands, one subapical, almost straight and the other sinuous, at midlength.
Head
(Fig.
Male genitalia. Anterolateral margin of segment IX slightly rounded. Tergum of segment X triangular in lateral view, dorsal and ventral margins straight, the ventral one with a sclerotized Y-shaped area directed anteriorly through segment IX (Fig.
This species seems to be closely related to S. brasiliana and S. nanda (see Systematic considerations section for S. brasiliana). Smicridea weidneri can be identified by the spindle-shaped distal end of the ejaculatory duct, that is simple in the other two species, and the shape of the two pairs of plates, two rhomboidal, with ventral and posterior margins serrated, and covered with small spines, and two spine-like, wide, directed posteriorly.
Argentina, Brazil.
Smicridea (Rhyacophylax) vermiculata
Flint, 1978: 381.
Argentina • 27 males; Misiones, Oberá, Centro de Investigación y Refugio de Selva Antonia Ramos, A° Ramos; 17 Nov. 2013; JV Sganga col.; light trap.
Adult male. General coloration of the body brown. Length of forewings 4.5 mm (n = 22), coloration similar to that of the body, with a distinct transverse, white band subapically.
Head
(Fig.
Male genitalia. Anterolateral margin of segment IX rounded, produced. Tergum of segment X triangular in lateral view, dorsal margin straight, ventral slightly rounded, with a subapical lobe, and a sclerotized Y-shaped area directed anteriorly through segment IX (Fig.
This species seems to be related to S. (R.) dentifera Flint, 1983 and S. (R.) unguiculata. The three species have simple ejaculatory ducts and lateroventral spines at the apex of the phallus. The features that allow the differentiation of S. vermiculata are the position of the spines of the phallus (it has 4 mesoventral spines on each side directed posteriorly), the ejaculatory duct that is curved upwards and bears a posterior concavity, and the presence of the apicolateral lobe on tergum X.
Argentina, Brazil, Paraguay.
Smicridea (Rhyacophylax) atrobasis
Flint, 1983: 63.
Uruguay • 22 males; Salto, Salto Grande; 19 Nov. 1955; a la luz, en la cascada; FHCM • 1 male; Artigas, río Uruguay, barra Arroyo Guaviyú; 22 Nov. 1954; CS Carbonell leg. (OS Flint Jr. det.) • 1 male; San Gregorio; 29 Nov. 1959; Carbonell, Mesa, San Martín leg. (OS Flint Jr. det.).
Adult male. Coloration of the body in alcohol stramineous. Length of forewings 5.4 mm (n = 18). We were not able to observe the coloration of the wings in the specimens preserved in alcohol due to discoloration of the cuticle through time, but Flint (1983) described it from dried specimens as follows: “forewings dark purplish black in basal quarter and in two transverse bands apicad, otherwise covered with golden hair”.
Head
(Fig.
Male genitalia. Anterolateral margin of segment IX sinuous. Tergum of segment X triangular in lateral view, dorsal and ventral margins rounded, with a ventral sclerotized Y-shaped area directed anteriorly through segment IX (Fig.
This species seems to be closely related to Smicridea mesembrina. These two species bear apicolateral lobes on the phallus, but while the apex of the sclerotized section of the ejaculatory duct in S. mesembrina is simple, in S. atrobasis it is shaped like an arrowhead. Additionally, S. atrobasis has a very distinctive feature that is the prominent eyes and reduced interocular area.
Argentina, Bolivia, Brazil, Uruguay.
Smicridea (Rhyacophylax) nanda
Flint, 1983:65.
Argentina • 1 male; Misiones, Río Iguazú, camp. Nandu; 25 Feb. 1973; OS Flint Jr. col.; paratype;
Adult male. General coloration of the body light brown. Length of forewings 6.8 mm (n = 1), coloration similar to that of the body, with a soft darkening on the crossveins and a pale, subapical, transverse band.
Head
(Fig.
Male genitalia. Anterolateral margin of segment IX slightly rounded on the dorsal half (Fig.
This species seems to be related to S. brasiliana and S. weidneri (see Systematic considerations section for S. brasiliana). Smicridea nanda is characterized by the ejaculatory duct that is curved dorsad at midlength and distally upturned, and the shape of the two pairs of sclerotized plates: the dorsolateral ones elongated, oval in lateral view and the other two spine-like lying beneath them.
Argentina.
This approach allowed the differentiation of the analyzed species based on their wing shape. In the CVA analysis, the first two axes explained 79.25% of the shape variance. The shape configurations of S. mesembrina and S. weidneri occupied extreme morphospaces in the CV1 axis, and S. mesembrina and S. vermiculata in the CV2 axis (Fig.
Canonical variate analysis of Smicridea species mean wing shape. Number of individuals used of each species are indicated in diagonal. The percentage of correct classification above the main diagonal and Mahalonobis distances are below. The P-values < 0.05 for permutation tests (2000 permutation runs) are marked with asterisks (*).
S. atrobasis | S. vekona | S. weidneri | S. spinulosa | S. unguiculata | S. vermiculata | S. mesembrina | S. pampeana | |
---|---|---|---|---|---|---|---|---|
S. atrobasis | 18 | 100.00% | 79.41% | 100.00% | 100.00% | 100.00% | 100.00% | 100.00% |
S. vekona | 5.9096* | 19 | 88.57% | 86.48% | 88.74% | 97.56% | 100.00% | 91.89% |
S. weidneri | 4.0849* | 4.9467* | 16 | 100.00% | 97.22% | 100.00% | 100.00% | 97.05% |
S. spinulosa | 6.9183* | 4.7454* | 6.12* | 18 | 92.10% | 92.50% | 100.00% | 100.00% |
S. unguiculata | 6.1731* | 5.1658* | 6.2365* | 2.8877* | 20 | 92.85% | 100.00% | 92.10% |
S. vermiculata | 9.1635* | 8.2066* | 8.518* | 4.5723* | 4.3243* | 22 | 100.00% | 100.00% |
S. mesembrina | 9.1130* | 9.3375* | 10.8162* | 8.0428* | 7.1655* | 9.1801* | 21 | 97.44% |
S. pampeana | 5.1981* | 5.1464* | 6.3722* | 5.3095* | 4.6305* | 7.9502* | 6.4921* | 18 |
A Canonical Variate Analysis (CVA) scatter plot of the wing shape landmark data of eight Smicridea species B, C patterns of shape change along each axis by superposition of the mean configurations of the species located in extreme morphospaces of each axis B superposition of the mean (average) wings shape of Smicridea (Rhyacophylax) mesembrina - S. (R.) weidneri C superposition of the mean wings shape of S. (R.) mesembrina - S. (R.) vermiculata.
The principal component analysis of the consensus shapes of the species included in the brasiliana group revealed that S. nanda showed the furthest configuration and S. (R.) brasiliana the closest from the consensus shape of the group (Fig.
Principal Component Analysis (PCA) of the geometric landmark data of the wings of the brasiliana species group A scatter plot showing the average configuration of the wing shape in the deformation grids of each species from consensus shape of species group (indicate in the center of the plot) in the first two CPs. The circles represent the locations of the reference points in the mean shape of each species B UPGMA. Dendrogram from Mahalanobis distance of brasiliana species group and C without Smicridea (Rhyacophylax) atrobasis.
All species included in the analysis differed in CS (p < 0.05), except S. (R.) spinulosa with S. (R.) atrobasis (p > 0.05) and S. (R.) vermiculata with S. (R.) weidneri (p > 0.05) (Fig.
Based on the analysis of the fine structure of the genitalia of the species of the brasiliana group we consider that the group is heterogeneous. Smicridea brasiliana, S. weidneri, and S. nanda seem to be closely related species with complex phallic structures, including internal plates of different shapes associated with the distal end of the sclerotized ejaculatory duct that are absent in S. atrobasis and S. vermiculata. In particular the genitalia of S. vermiculata is most similar to that of S. dentifera Flint and S. unguiculata Flint, which are unplaced to species groups, that have a simple ejaculatory duct and lateral subapical spines at the phallus. The analysis of the morphology of the heads of these species also supports a closer relationship between S. brasiliana, S. weidneri, and S. nanda, with anterolateral setose warts bifid and posterior setose warts triangular. The head of S. vermiculata is more similar in shape to these species but differs in the structure of the posterior setose warts that bear internal lobes and the postgenal areas that are more developed. In contrast, the head of S. atrobasis is unique in the group, with a more quadrangular outline, very large eyes, a reduced interocular area, and oval anterolateral setose warts. The genitalia of this species is also different from the rest: the apex of the ejaculatory duct is shaped like an arrowhead in dorsal view and the phallus ends in two laterodorsal and two lateroventral lobes. The presence of apicolateral lobes on the phallus is also found in S. (R.) mesembrina, not placed in a species group. The relationships between S. brasiliana, S. weidneri, and S. nanda are also strengthened by the configurations of the forewings, as was observed through the geometric morphometrics analysis.
The placement of S. atrobasis in the brasiliana group is conflictive. As stated before, although the configuration of the forewing of this species is similar to that of S. weidneri, the genitalia and the morphology of the head of both species differ. The relationships of the forewing configurations in the brasiliana species group were compared in the dendrogram, with and without S. atrobasis. The exclusion of this species from the analysis shows the same patterns that the ones observed using the morphology of the genitalia and features of the head. In this context, the similarities in the forewing configuration could be seen as a homoplasy rather than a homology, although further phylogenetic analyses are needed for confirmation.
The geometric morphometric analysis of wing shapes was useful for discriminating the species herein studied. This is the first study that uses this methodology in the order Trichoptera and needs to be examined in more species of Smicridea, and other caddisfly taxa as well, using not only wing shapes but other structures of the body. The larvae of Smicridea (Rhyacophylax) are good candidates to test this approach. In this subgenus the larvae are generally very similar, with no clear defining characters to separate them, but there are subtle interspecific differences in the shape of the head and the frontoclypeal apotome (JS pers. obs.). These differences in shape could be tested with this methodology. Taking into consideration that landmark configurations can be used in phylogenetic reconstructions (
In this study, we provided a new approach for the delimitation of species in the genus. The head morphology is somewhat overlooked in the descriptions of most Trichoptera species. Here, we propose a more comprehensive approach including more detailed descriptions of relevant characters, besides the male genitalia, that would be useful for differentiating closely related species. Likewise, we demonstrated that the geometric morphometrics analysis of wing shapes can be used to discriminate the species of Smicridea (Rhyacophylax) herein studied. This fast, simple, and inexpensive method proved to be an efficient technique to confirm the identity of the specimens and could potentially be used to differentiate cryptic species, which were previously reported in Smicridea and other insect genera (
Even though the analyzed features indicate that the brasiliana group might not be a natural group as informally defined, the relationships between these species and the rest of the species in the subgenus Rhyacophylax must be established by a phylogenetic analysis and the monophyly of all the current groups of species should be tested.
We appreciate the comments and suggestions made by the two reviewers that improved the quality of the manuscript. We specially thank the late Dr. Oliver Flint, Jr. (National Museum of Natural History, Washington DC, USA), Dr. Enrique Morelli (Facultad de Humanidades y Ciencias, Universidad de la República, Uruguay) and Dr. Paola A. Rueda Martín (Instituto de Biodiversidad Neotropical, CONICET-Universidad Nacional de Tucumán, Argentina) for the loan of specimens. We extend our gratitude to the forest rangers of Salto Encantado Provincial Park and Forest Refuge and research center Antonia Ramos for field assistance and to Alejandro A. Fernandez for laboratory assistance. We also thank the Ministerio de Ecología y Recursos Naturales Renovables from Misiones Province for its support and for providing the permits to sample in the protected areas.
This project received financial support from UBACyT 20020130200240BA and Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires.