Research Article |
Corresponding author: Jana Christophoryová ( christophoryova@gmail.com ) Academic editor: Pavel Stoev
© 2016 Jana Christophoryová, Katarína Krajčovičová, Hans Henderickx, Stanislav Španiel.
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:
Christophoryová J, Krajčovičová K, Henderickx H, Španiel S (2016) A multivariate study of differentiating characters between three European species of the genus Lasiochernes Beier, 1932 (Pseudoscorpiones, Chernetidae). ZooKeys 629: 51-81. https://doi.org/10.3897/zookeys.629.8445
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Morphological variation in three rarely collected European species of the genus Lasiochernes Beier, 1932 is thoroughly examined in the present study. Detailed descriptions of previously ignored morphological characters of L. cretonatus Henderickx, 1998, L. jonicus (Beier, 1929) and L. pilosus (Ellingsen, 1910) are presented. The female of L. cretonatus and the nymphs of L. pilosus are described for the first time. Multivariate morphometric techniques (principal coordinate analysis and discriminant analyses) were employed to confirm morphological differentiation of the three Lasiochernes species and to identify the most reliable characters for their separation. The usefulness of particular body parts for species identification was evaluated. An identification key for the females of the Lasiochernes species studied is provided. Geographic distribution and habitat preferences of the three species are summarized.
Caves, mole nests, morphology, morphometric analysis, pseudoscorpion, taxonomy
The genus Lasiochernes Beier, 1932 belongs to the subfamily Lamprochernetinae, as defined by
Detailed morphological descriptions of European pseudoscorpion species are rare. This holds true for both the adults and nymphal stages. These descriptions of adults and all nymphal stages are available mainly for the families Chthoniidae, Neobisiidae and Cheliferidae (e.g.
Material of three Lasiochernes species was obtained during our study: L. cretonatus, L. jonicus and L. pilosus. L. cretonatus was described from a single male collected in a cave in Crete (Greece) (
Morphological differences between species of pseudoscorpions, as reported in taxonomic descriptions, are often based on quantitative traits. Multivariate morphometric methods are an effective tool to compare the role of numerous quantitative and qualitative characters and allow in-depth examination of morphological variation of phenetically similar taxa. In recent years, many papers have successfully employed multivariate morphometrics in the taxonomy of invertebrates, such as mites (
The aims of this study are to (1) assemble detailed morphological descriptions of the adults of the three investigated Lasiochernes species, (2) describe all the nymphal stages of L. pilosus, (3) assess the extent of morphological differentiation between adults of the three species, (4) identify the morphological characters that are most relevant for the differentiation of the three species and (5) provide an identification key for the females of the three species.
Lasiochernes cretonatus: Greece, Crete, Azogires (Fig.
L. jonicus: Greece, Pelion, Mouresi (Fig.
L. pilosus: Slovakia, Malé Karpaty Mts., Borinka (Fig.
Populations of Lasiochernes collected from mole nests in Belgium and Slovakia were identified as L. pilosus (
The chelicera, palp, leg I and leg IV were removed from the left side of the body of all specimens examined. In the case of L. pilosus, these appendages were mounted as permanent slide mounts using Swann’s fluid as the medium. The rest of the body was studied as a temporary slide mount using lactic acid, after which it was returned to 70% ethanol. The body and the dissected appendages of L. cretonatus and L. jonicus were studied as temporary slide mounts using lactic acid, after which they were returned to 70% ethanol.
Measurements were taken from photographs using the Zeiss AxioVision 40LE application (v. 4.6). These photographs were made using the Canon EOS Utility software and a digital camera (Canon EOS 1100D) connected to a Zeiss Stemi 2000-C stereomicroscope or a Leica ICC50 camera connected to a Leica DM1000 stereomicroscope using Leica LAS EZ 1.8.0 software. Figures
Methods of multivariate morphometrics (
Descriptive statistics of the measured morphological characters of the studied Lasiochernes species. Abbreviations: n: number of measured specimens. Mean values of the measured characters ± standard deviation (Mean ± SD) are given in upper rows; minimum and maximum (Min–Max) are in lower rows. Values of all the measured characters are in mm.
Characters/Species Mean ± SD Min–Max |
Lasiochernes cretonatus | Lasiochernes jonicus | Lasiochernes pilosus | |||
---|---|---|---|---|---|---|
Adults | Adults | Adults | Tritonymphs | Deutonymphs | Protonymphs | |
n = 5 | n = 2 | n = 12 | n = 15 | n = 15 | n = 15 | |
Body length | 4.23±0.20 4.03–4.51 |
2.98±1.00 2.27–3.69 |
3.92±0.65 3.12–4.98 |
2.73±0.36 2.18–3.38 |
2.50±0.20 2.11–2.78 |
1.59±0.13 1.41–1.80 |
Carapace length | 1.01±0.02 0.99–1.03 |
1.03±0.03 1.01–1.05 |
1.22±0.08 1.12–1.36 |
0.97±0.05 0.91–1.09 |
0.77±0.05 0.69–0.89 |
0.58±0.04 0.54–0.67 |
Carapace posterior width | 1.00±0.00 0.99–1.00 |
1.09±0.01 1.08–1.09 |
1.28±0.13 1.12–1.55 |
1.04±0.06 0.92–1.13 |
0.85±0.06 0.73–0.95 |
0.66±0.04 0.60–0.75 |
Carapace length/posterior width ratio | 1.02±0.02 0.99–1.03 |
0.95±0.03 0.93–0.97 |
0.96±0.05 0.88–1.05 |
0.94±0.03 0.88–0.99 |
0.91±0.05 0.84–0.99 |
0.88±0.03 0.83–0.95 |
Chelicera length | 0.35±0.01 0.35–0.36 |
0.36±0.00 0.36–0.36 |
0.37±0.04 0.33–0.45 |
0.28±0.02 0.26–0.31 |
0.22±0.01 0.21–0.23 |
0.16±0.01 0.15–017 |
Chelicera width | 0.18±0.01 0.17–0.18 |
0.17±0.01 0.16–0.18 |
0.23±0.02 0.20–0.27 |
0.18±0.01 0.16–0.19 |
0.13±0.01 0.12–0.14 |
0.10±0.01 0.09–0.11 |
Chelicera length/width ratio | 2.01±0.07 1.94–2.12 |
2.13±0.18 2.00–2.25 |
1.67±0.09 1.54–1.86 |
1.61±0.07 1.44–1.72 |
1.72±0.08 1.57–1.83 |
1.63±0.07 1.55–1.78 |
Cheliceral movable finger length | 0.26±0.01 0.26–0.27 |
0.21±0.01 0.20–0.21 |
0.30±0.03 0.25–0.34 |
0.22±0.07 0.21–0.23 |
0.17±0.00 0.17–0.18 |
0.13±0.01 0.12–0.15 |
Palpal trochanter length | 0.52±0.01 0.50–0.53 |
0.53±0.01 0.52–0.53 |
0.63±0.06 0.53–0.69 |
0.42±0.02 0.39–0.45 |
0.30±0.03 0.27–0.33 |
0.20±0.01 0.18–0.24 |
Palpal trochanter width | 0.38±0.00 0.38–0.38 |
0.42±0.02 0.40–0.43 |
0.43±0.05 0.34–0.51 |
0.30±0.02 0.27–0.33 |
0.21±0.01 0.18–0.23 |
0.14±0.01 0.13–0.15 |
Palpal trochanter length/width ratio | 1.33±0.05 1.27–1.39 |
1.27±0.05 1.23–1.30 |
1.46±0.11 1.30–1.63 |
1.40±0.06 1.29–1.48 |
1.44±0.11 1.23–1.68 |
1.42±0.07 1.33–1.60 |
Palpal femur length | 0.95±0.03 0.93–0.99 |
0.97±0.05 0.93–1.00 |
1.11±0.09 0.91–1.26 |
0.72±0.04 0.66–0.79 |
0.50±0.02 0.47–0.55 |
0.31±0.02 0.28–0.35 |
Palpal femur width | 0.38±0.01 0.37–0.39 |
0.50±0.12 0.41–0.58 |
0.44±0.05 0.38–0.53 |
0.32±0.02 0.29–0.34 |
0.22±0.01 0.19–0.25 |
0.14±0.01 0.12–0.15 |
Palpal femur length/width ratio | 2.50±0.05 2.44–2.54 |
2.02±0.59 1.60–2.44 |
2.51±0.19 2.19–2.80 |
2.29±0.12 2.09–2.48 |
2.28±0.11 2.17–2.47 |
2.29±0.14 2.07–2.62 |
Palpal patella length | 0.96±0.03 0.93–0.99 |
1.02±0.01 1.01–1.02 |
1.04±0.10 0.82–1.18 |
0.67±0.04 0.62–0.72 |
0.46±0.02 0.43–0.48 |
0.29±0.01 0.27–0.30 |
Palpal patella width | 0.44±0.01 0.42–0.45 |
0.43±0.01 0.42–0.44 |
0.49±0.06 0.41–0.60 |
0.35±0.02 0.32–0.40 |
0.24±0.01 0.23–0.27 |
0.15±0.00 0.15–0.16 |
Palpal patella length/width ratio | 2.21±0.06 2.15–2.30 |
2.36±0.06 2.32–2.40 |
2.14±0.16 1.90–2.41 |
1.91±0.08 1.79–2.06 |
1.87±0.06 1.74–1.96 |
1.88±0.04 1.80–2.00 |
Palpal hand with pedicel length | 0.89±0.01 0.88–0.91 |
0.94±0.08 0.88–0.99 |
1.06±0.10 0.81–1.18 |
0.77±0.05 0.68–0.83 |
0.54±0.03 0.51–0.59 |
0.36±0.02 0.33–0.39 |
Palpal hand without pedicel length | 0.77±0.03 0.74–0.81 |
0.80±0.06 0.75–0.84 |
0.93±0.09 0.74–1.05 |
0.69±0.04 0.60–0.76 |
0.49±0.03 0.45–0.55 |
0.32±0.02 0.31–0.37 |
Palpal hand width | 0.58±0.02 0.57–0.61 |
0.59±0.00 0.59–0.59 |
0.65±0.06 0.54–0.74 |
0.47±0.03 0.42–0.52 |
0.31±0.02 0.28–0.34 |
0.19±0.01 0.17–0.20 |
Palpal hand with pedicel length/width ratio | 1.53±0.05 1.44–1.58 |
1.58±0.13 1.49–1.68 |
1.64±0.08 1.50–1.72 |
1.53±0.08 1.36–1.65 |
1.74±0.06 1.64–1.84 |
1.89±0.14 1.70–2.18 |
Palpal fixed finger length | 0.84±0.06 0.80–0.95 |
0.74±0.04 0.71–0.77 |
0.93±0.05 0.83–1.01 |
0.62±0.04 0.54–0.68 |
0.43±0.02 0.41–0.48 |
0.30±0.02 0.27–0.33 |
Palpal chela length | 1.66±0.09 1.58–1.78 |
1.61±0.07 1.56–1.66 |
1.93±0.15 1.55–2.12 |
1.34±0.09 1.20–1.47 |
0.93±0.03 0.88–0.98 |
0.63±0.02 0.60–0.69 |
Palpal chela length/palpal hand width | 2.86±0.09 2.77–2.96 |
2.73±0.12 2.64–2.81 |
3.00±0.19 2.69–3.36 |
2.88±0.11 2.71–3.13 |
2.96±0.13 2.79–3.21 |
3.35±0.17 3.15–3.65 |
Leg I trochanter length | 0.23±0.02 0.21–0.24 |
0.22±0.02 0.20–0.23 |
0.27±0.03 0.23–0.31 |
0.20±0.01 0.17–0.24 |
0.13±0.01 0.12–0.15 |
0.09±0.01 0.08–0.10 |
Leg I trochanter width | 0.17±0.01 0.17–0.18 |
0.18±0.00 0.18–0.18 |
0.21±0.02 0.19–0.24 |
0.16±0.01 0.15–0.19 |
0.12±0.01 0.11–0.14 |
0.08±0.01 0.07–0.09 |
Leg I trochanter length/width ratio | 1.31±0.08 1.23–1.41 |
1.19±0.12 1.11–1.28 |
1.27±0.08 1.14–1.41 |
1.24±0.09 1.13–1.40 |
1.13±0.05 1.07–1.18 |
1.07±0.06 1.00–1.14 |
Leg I femur length | 0.27±0.01 0.27–0.28 |
0.26±0.03 0.24–0.28 |
0.31±0.03 0.25–0.35 |
0.20±0.02 0.17–0.23 |
0.13±0.01 0.12–0.15 |
0.10±0.01 0.09–0.12 |
Leg I femur width | 0.17±0.01 0.17–0.18 |
0.19±0.01 0.18–0.20 |
0.23±0.02 0.20–0.25 |
0.16±0.01 0.14–0.20 |
0.11±0.01 0.10–0.13 |
0.08±0.01 0.07–0.11 |
Leg I femur length/width | 1.58±0.07 1.50–1.65 |
1.37±0.05 1.33–1.40 |
1.37±0.08 1.24–1.50 |
1.23±0.08 1.13–1.43 |
1.17±0.11 1.00–1.40 |
1.19±0.08 1.00–1.29 |
Leg I patella length | 0.50±0.06 0.44–0.58 |
0.48±0.01 0.47–0.48 |
0.55±0.04 0.46–0.61 |
0.38±0.02 0.34–0.41 |
0.27±0.02 0.25–0.30 |
0.18±0.01 0.16–0.19 |
Leg I patella width | 0.17±0.02 0.15–0.19 |
0.16±0.00 0.16–0.16 |
0.20±0.02 0.17–0.22 |
0.15±0.01 0.13–0.17 |
0.11±0.01 0.10–0.12 |
0.08±0.01 0.07–0.09 |
Leg I patella length/width ratio | 3.03±0.20 2.75–3.22 |
2.97±0.04 2.94–3.00 |
2.78±0.19 2.42–3.06 |
2.57±0.12 2.33–2.67 |
2.57±0.14 2.36–2.80 |
2.26±0.13 2.11–2.57 |
Leg I tibia length | 0.52±0.06 0.46–0.60 |
0.47±0.04 0.44–0.49 |
0.55±0.05 0.46–0.62 |
0.36±0.02 0.33–0.41 |
0.24±0.01 0.23–0.26 |
0.16±0.01 0.15–0.17 |
Leg I tibia width | 0.13±0.01 0.12–0.15 |
0.12±0.01 0.11–0.12 |
0.15±0.01 0.13–0.16 |
0.11±0.02 0.10–0.13 |
0.08±0.00 0.08–0.09 |
0.06±0.00 0.06–0.07 |
Leg I tibia length/width | 3.97±0.21 3.73–4.29 |
4.04±0.06 4.00–4.08 |
3.81±0.29 3.44–4.21 |
3.23±0.15 3.00–3.50 |
2.88±0.10 2.67–3.00 |
2.55±0.15 2.29–2.83 |
Leg I tarsus length | 0.42±0.05 0.38–0.47 |
0.33±0.03 0.31–0.35 |
0.49±0.04 0.42–0.56 |
0.35±0.02 0.31–0.38 |
0.25±0.01 0.23–0.26 |
0.17±0.01 0.15–0.19 |
Leg I tarsus width | 0.11±0.01 0.10–0.12 |
0.09±0.01 0.08–0.09 |
0.11±0.01 0.09–0.12 |
0.09±0.01 0.08–0.09 |
0.07±0.01 0.06–0.07 |
0.05±0.00 0.05–0.06 |
Leg I tarsus length/width ratio | 3.88±0.52 3.25–4.70 |
3.91±0.66 3.44–4.38 |
4.48±0.40 3.83–5.11 |
4.02±0.19 3.67–4.38 |
3.77±0.20 3.57–4.17 |
3.33±0.21 3.00–3.60 |
Leg IV trochanter length | 0.39±0.02 0.37–0.42 |
0.33±0.04 0.30–0.35 |
0.43±0.06 0.34–0.53 |
0.33±0.01 0.30–0.35 |
0.21±0.02 0.20–0.24 |
0.13±0.01 0.10–0.15 |
Leg IV trochanter width | 0.20±0.01 0.19–0.21 |
0.18±0.01 0.17–0.19 |
0.26±0.03 0.21–0.29 |
0.21±0.01 0.19–0.22 |
0.14±0.01 0.12–0.16 |
0.09±0.01 0.08–0.11 |
Leg IV trochanter length/width ratio | 1.91±0.12 1.81–2.10 |
1.80±0.05 1.76–1.84 |
1.69±0.13 1.48–1.91 |
1.61±0.06 1.55–1.75 |
1.59±0.10 1.40–1.71 |
1.48±0.15 1.11–1.67 |
Leg IV femoropatella length | 0.81±0.05 0.74–0.85 |
0.91±0.09 0.84–0.97 |
1.04±0.09 0.88–1.18 |
0.71±0.04 0.63–0.76 |
0.51±0.02 0.48–0.54 |
0.33±0.02 0.30–0.35 |
Leg IV femoropatella width | 0.19±0.02 0.17–0.21 |
0.19±0.01 0.18–0.19 |
0.23±0.03 0.19–0.27 |
0.20±0.01 0.18–0.23 |
0.15±0.01 0.13–0.16 |
0.10±0.01 0.09–0.11 |
Leg IV femoropatella length/width ratio | 4.26±0.34 3.76–4.72 |
4.89±0.31 4.67–5.11 |
4.51±0.33 4.00–4.95 |
3.67±0.18 3.30–3.89 |
3.51±0.14 3.27–3.77 |
3.39±0.13 3.10–3.56 |
Leg IV tibia length | 0.76±0.03 0.74–0.80 |
0.72±0.03 0.70–0.74 |
0.84±0.08 0.71–0.96 |
0.56±0.03 0.50–0.60 |
0.37±0.02 0.35–0.40 |
0.23±0.01 0.21–0.25 |
Leg IV tibia width | 0.13±0.00 0.12–0.13 |
0.14±0.00 0.14–0.14 |
0.15±0.02 0.12–0.17 |
0.13±0.01 0.12–0.15 |
0.11±0.01 0.10–0.11 |
0.08±0.01 0.07–0.08 |
Leg IV tibia length/width | 5.97±0.28 5.69–6.33 |
5.14±0.20 5.00–5.29 |
5.57±0.45 4.44–6.33 |
4.29±0.32 3.79–4.75 |
3.53±0.09 3.36–3.70 |
3.06±0.12 2.88–3.29 |
Leg IV tarsus length | 0.48±0.02 0.46–0.50 |
0.40±0.03 0.38–0.42 |
0.57±0.04 0.49–0.64 |
0.41±0.02 0.38–0.44 |
0.29±0.01 0.27–0.31 |
0.20±0.01 0.18–0.21 |
Leg IV tarsus width | 0.11±0.00 0.11–0.11 |
0.10±0.01 0.09–0.10 |
0.12±0.01 0.09–0.14 |
0.10±0.01 0.09–0.11 |
0.08±0.01 0.07–0.09 |
0.06±0.00 0.05–0.06 |
Leg IV tarsus length/width ratio | 4.40±0.15 4.18–4.55 |
4.23±0.61 3.80–4.67 |
4.80±0.43 4.17–5.70 |
4.02±0.21 3.64–4.44 |
3.60±0.25 3.11–4.00 |
3.46±0.18 3.00–3.80 |
The statistical analyses were performed as follows:
(1) As the first step, the Shapiro-Wilk statistic for the test of normality of distribution was computed for each character.
(2) Principal coordinate analysis, PCoA (
(3) Correlation between the principal coordinate axes of PCoA and original quantitative characters was computed using Pearson correlation coefficient (
(4) Discriminant analyses (
(5) Finally, descriptive statistics were computed for adults of the three Lasiochernes species, and for nymphs of L. pilosus. Variations in the morphological characters that differentiate between them are shown as box-and-whisker plots. The minimum and maximum values for the measured characters are reported in identification key and morphological descriptions. The analyses were performed using SAS 9.1.3 software SAS/STAT v.9.2 (
Morphological descriptions. Adults of the studied Lasiochernes species share the following characteristic. Setae on body relatively short and clavate. Carapace approximately as long as broad, granulate and rectangular, epistome absent, anterior margin straight, eyes or eyespots absent, anterior and posterior transverse furrows distinct (Figs
Palpal chela of Lasiochernes species, showing the trichobothrial pattern. A L. cretonatus male B L. jonicus female C L. pilosus male. Abbreviations in terminology of trichobothria: movable finger: t–terminal, st–subterminal, sb–subbasal, b–basal; fixed finger: et–exterior terminal, est–exterior subterminal, esb–exterior subbasal, eb–exterior basal, it–interior terminal, ist–interior subterminal, isb–interior subbasal, ib–interior basal. Scale lines: 0.5 mm.
Female (4 specimens analyzed) (Table
Male (1 specimen analyzed) (Fig.
Female (1 specimen analyzed) (Table
Male (1 specimen analyzed) (figs 2A, 2C; Table
Female (7 specimens analyzed) (Table
Male (5 specimens analyzed) (Fig.
Nymphs (Fig.
Tritonymphs (15 specimens analyzed) (Table
Deutonymphs (15 specimens analyzed) (Table
Protonymphs (15 specimens analyzed) (Table
Most of the measured characters showed departures from a normal distribution. Therefore, the nonparametric correlation coefficient (Spearman) (apart from the Pearson parametric coefficient) and nonparametric classificatory discriminant analyses were used.
The ordination diagram of PCoA of the three Lasiochernes species, based on 85 morphological characters for 19 adult specimens, showed two large groupings of specimens separated along the first principal coordinate axis (Fig.
Principal coordinate analysis (PCoA) of 19 adult specimens of three species of Lasiochernes based on 85 morphological characters: L. cretonatus (green circles), L. jonicus (red squares) and L. pilosus (blue hearts). The first three coordinate axes explain 37.8%, 15.1% and 12.6% of the variation.
Eight canonical (CDA 1–CDA 8) and classificatory discriminant analyses (DA 1–DA 8) were performed to identify the characters and body parts that are most important for the differentiation of the three species, and to evaluate the degree of differentiation in each case. The three character pairs (length and posterior width of carapace, length of palpal hand with and without pedicel, length of patella and tibia of leg I) exceeded the correlation threshold of 0.95 in datasets with the body parts and, therefore, three characters (posterior width of carapace, length of palpal hand with pedicel and length of leg I patella) were excluded from further analyses. In CDAs (CDA 1–8), three species mostly formed their own clouds in the ordination space without overlaps (Fig.
Eight canonical discriminant analyses (CDA 1–8) of three Lasiochernes species (L. cretonatus: green circles; L. jonicus: red squares; L. pilosus: blue hearts) based on 19 adult specimens and morphological characters measured/scored on eight different parts of the body (A–G): ACDA 1: Carapace BCDA 2: Chelicera CCDA 3: Palp (without chela) DCDA 4: Chela ECDA 5: Leg I FCDA 6: Leg IV GCDA 7: Tergites HCDA 8: Sternites. For total canonical structure and the lists of characters measured/scored on each body parts, see Supplementary file 1.
Results of eight canonical discriminant analyses (CDA 1–CDA 8, Fig.
Body parts | Can 1 | Can 2 |
---|---|---|
Carapace (CDA 1, Fig. |
Length | Total setae number |
Number of setae on anterior disk | ||
Number of setae on posterior margin | ||
Chelicera (CDA 2, Fig. |
Width | Length of movable finger |
Length/width ratio | ||
Number of blades in serrula exterior | ||
Palp (CDA 3, Fig. |
Length of trochanter | Width of femur |
Length of femur | Length/width ratio of femur | |
Chela (CDA 4, Fig. |
Length of hand without pedicel | Length/width ratio of hand |
Length of fixed finger | Number of marginal teeth on fixed finger | |
Length of chela | Number of antiaxial accessory teeth on movable finger | |
Number of antiaxial accessory teeth on fixed finger | ||
Number of antiaxial accessory teeth on movable finger | ||
Leg I (CDA 5, Fig. |
Length of tarsus | Length/depth ratio of femur |
Leg IV (CDA 6, Fig. |
Length of trochanter | Length/depth ratio of trochanter |
Depth of trochanter | Length of femur | |
Length of tarsus | Depth of tibia | |
depth of tarsus | ||
Tergites (CDA 7, Fig. |
Number of setae on tergite II | Number of setae on tergite III |
Number of setae on tergite V | Number of setae on tergite X | |
Number of setae on tergite IX | ||
Sternites (CDA 8, Fig. |
Number of setae on sternite IV | Lyrifissures number on genital operculum posterior |
Number of setae on sternite X | ||
Lyrifissures number on genital operculum posterior |
Finally, the classificatory DA 9 and CDA 9 were computed to assess the differentiation of the three species based on the selection of the most important characters from all the parts of the body, as revealed in CDA 1–8. In the classificatory DA 9, the classification success rate reached 100% for all the specimens. The three species were clearly separated in the ordination space of CDA 9 (Fig.
The variations in morphological characters that are most useful for differentiation of the three Lasiochernes species are shown in Fig.
Results of the canonical discriminant analysis (CDA 9, Fig.
Morphological characters | Can 1 | Can 2 |
---|---|---|
Number of setae on posterior carapace margin | -0.635 | -0.420 |
Total number of setae on carapace | 0.766 | -0.072 |
Number of setae on anterior disk | 0.829 | 0.311 |
Width of chelicera | 0.653 | 0.523 |
Length/width ratio of chelicera | -0.649 | -0.641 |
Number of blades in serrula exterior | 0.779 | 0.484 |
Length of palpal trochanter | 0.661 | 0.415 |
Length of palpal femur | 0.611 | 0.388 |
Length of palpal hand without pedicel | 0.625 | 0.342 |
Length of palpal chela | 0.573 | 0.500 |
Number of antiaxial accessory teeth on movable chelal finger | 0.805 | 0.355 |
Depth of tibia of leg I | 0.355 | 0.584 |
Length/depth ratio of femur of leg I | -0.449 | 0.012 |
Length of tarsus of leg I | 0.411 | 0.742 |
Length of tarsus of leg IV | 0.459 | 0.734 |
Based on all the results obtained, nine morphological characters that differentiate females of the three species were selected (Table
1 | Movable finger of chelicera 0.20 mm long; tarsus of leg I 0.35 mm long; femoropatella of leg IV 5.11 times longer than deep | L. jonicus |
‒ | Movable finger of chelicera over 0.26 mm long; tarsus of leg I over 0.38 mm long; femoropatella of leg IV less than 4.95 times longer than deep | 2 |
2 | Palpal hand with pedicel 0.88–0.91 mm long; palpal chela 1.58–1.78 mm long; femur of leg I 1.50–1.65 longer than deep; 71–74 setae on carapace, 31–38 of them situated in front of anterior transverse furrow; tarsus of leg IV with long tactile seta situated one third from base | L. cretonatus |
‒ | Palpal hand with pedicel 1.00–1.18 mm long; palpal chela 1.88–2.06 mm long; femur of leg I 1.24–1.46 longer than deep; 81–96 setae on carapace, 49–63 of them situated in front of anterior transverse furrow; tarsus of leg IV with long tactile seta situated approximately in middle of segment | L. pilosus |
Comparison of adult females of L. cretonatus, L. jonicus, and L. pilosus in values of most differentiating morphological characters (measurements in mm). Boldface values indicate the characters that unambiguously differentiate all the three species.
Characters/species | L. cretonatus | L. jonicus | L. pilosus |
---|---|---|---|
Total setae number on carapace | 71–74 | 93 | 81–96 |
Number of setae on anterior disk of carapace | 31–38 | 51 | 49–63 |
Number of antiaxial accessory teeth on fixed chelal finger | 9–13 | 10 | 11–16 |
Length of movable cheliceral finger | 0.26–0.27 | 0.20 | 0.28–0.33 |
Length of palpal hand with pedicel | 0.88–0.91 | 0.99 | 1.00–1.18 |
Length of palpal chela | 1.58–1.78 | 1.66 | 1.88–2.06 |
Length/depth ratio of femur of leg I | 1.50–1.65 | 1.40 | 1.24–1.46 |
Length of tarsus of leg I | 0.38–0.47 | 0.35 | 0.46–0.56 |
Length/depth ratio of femoropatella of leg IV | 3.76–4.72 | 5.11 | 4.20–4.95 |
Lasiochernes cretonatus was described from Souré Cave (Cave of 99 Holy Fathers) in Crete, based on one male collected under a small piece of stone near the cave wall (
Lasiochernes jonicus was described as Chelifer (Trachychernes) jonicus by
The original description of L. cretonatus was based on one male (
Lasiochernes pilosus was described from one male by
In this paper, the potential of multivariate morphometric techniques for the diagnostic of pseudoscorpion species has been explored. Our study provides a first reference library of morphometric measurements that might be used for the identification of Lasiochernes specimens. The PCoA, which depicts the variation without prior definition of the groups in the dataset, showed rather clear differences between the three species. Two large groupings of specimens were visible in the PCoA, the first consisting of L. pilosus and the second of L. cretonatus and L. jonicus. The proximity of the latter two species in PCoA was probably caused by one specimen of L. cretonatus with significantly higher numbers of setae on the carapace (total and number on anterior disk). Discriminant analyses, which, unlike the PCoA, weight the characters to stress the between-group variation component, revealed considerable differences between the three species. These analyses were also used to identify the most differentiating body parts and the most important characters. The characters traditionally used most in identification keys to pseudoscorpions are those of the palps (
Multivariate morphometrics have been successfully applied in many other taxonomic studies of various invertebrates. For instance, they were very helpful in interpreting morphological differences between two cryptic species of Sancassania Oudemans, 1916, Acari (
The genus Lasiochernes is noteworthy for its sexual dimorphism (
Based on the results obtained, we assume that future studies will benefit from application of multivariate morphometric analyses, and could potentially help to find new characters and contribute to a more reliable identification of pseudoscorpion species.
We are grateful to the following colleagues for help with literature and distribution data: Theo Blick (Germany), Christoph Hörweg (Austria), Juan A. Zaragoza (Spain), Giulio Gardini (Italy), Volker Mahnert (Switzerland) and Dick van den Tooren (Netherlands). We thank Oto Majzlan for donating L. pilosus specimens, as well as Alica Christophory and Erika Igondová for technical assistance with figures. We would like to thank Juan A. Zaragoza for helping us with figures of pedipalps and reviewers Vincent Debat, Volker Mahnert and Mark Judson for all their corrections and comments that rapidly improved our manuscript. The project was financially supported by VEGA 1/0191/15.
Results of eight canonical discriminant analyses
Data type: statistical data
Explanation note: Results of eight canonical discriminant analyses (CDA 1–CDA 8, fig. 8) based on morphological characters measured/scored on 19 specimens and eight body segments of Lasiochernes cretonatus, L. jonicus, and L. pilosus. Values of the total canonical structure listed in the table express correlations of characters with canonical axes (Can 1 and Can 2) in each CDA. Higher total canonical structure values are in bold type.