Monti and Confalonieri—Comparing the use of phylogenetics and morphometrics in systematics
positively correlates with LPF/LOR, LPF/LPA, WPF/WOR, and WIG/Wgl.E; and negatively correlates with Lgl/LC (Table 5). Specimens located on the positive side of this axis have higher values for these variables. Specimens assigned to Parabolinella are mostly located in the positive values of the PC1 (Fig. 3.3), therefore they are characterized by a more developed preglabellar field related to the length of the occipital ring (sag.), more developed preglabellar field related
to the length of the preglabellar area (sag.), wider posterior fixigenae related to the width of the occipital ring (tr.), wider interocular genae related to the width of the glabella (at the eye line) (tr.), and shorter glabella related to the length of the cranidium (sag.) (Fig. 4.1). On the other hand, specimens of
the genus Bienvillia have a poorly developed preglabellar field related to the lengths of the occipital ring (sag.) and preglabllar area (sag.), narrower posterior fixigenae related to the width of the occipital ring (tr.), narrower interocular genae related to the width of the glabella (at the eye line) (tr.), and larger glabella related to the length of the cranidium (sag.) (Figs. 3.3, 4.2). Both methods are equally effective in reducing the size
effect. They do not show any correlation between the PC1 and the variables that estimate size (Coefficient of Pearson correlation: PC1 [RD] vs. Log LC: 0.02 [p=0.822];
Table 3. Eigenvalues and correlation coefficients for each variable with the two first components of the PCA obtained with log-transformed data (Fig. 3.1). Abbreviations of variables according to Figure 1 and Table 1. Asterisks indicate significant correlation.
Eigenvalue LPL
LC Lgl
WOR WglB WPF WIG WglE LPA LPF
Variable LOR
PC1
–0.2861 –0.2976 –0.2934 –0.2705 –0.3112 –0.2944 –0.3206 –0.2846 –0.3054 –0.3223 –0.3251
PC2
–0.4714 –0.6056
–0.2299 –0.0795 0.2791
0.2407 0.0779 0.2262 0.2028 0.2321 0.2526
PC1
0.9533* 0.9948* 0.9731* 0.9401* 0.9749* 0.9671* 0.9618* 0.9691* 0.9633* 0.9196* 0.8840*
Correlation PC2
–0.1929 –0.0756 0.2461
–0.3760 –0.4602
0.2242 0.0728 0.2096 0.1971 0.2033 0.2320
925
PC1 [RD] vs. Log GM: 0.09 [p=0.397]; PC1 [GMD] vs. Log LC: 0.06 [p=0.548]; PC1 [GMD] vs. Log GM: 0.13 [p=0.235]).
Figure 4. Cranidia of two specimens representing Parabolinella Brøgger, 1882 and Bienvillia Clark, 1924: (1) Parabolinella pompadouris Monti et al., 2016 from the Bocoyá River (CPBA 4036); (2) Bienvillia tetragonalis Harrington, 1938 from the Quebrada Rupasca (Holotype, CPBA 705). Scale bars represent 5mm.
Table 4. Eigenvalues with confidence intervals at 95% and correlation coefficients for each variable with the two first components of the PCA obtained with the data corrected by the geometric mean (Fig. 3.2). Abbreviations of variables according to Figure 1 and Table 1. Asterisks indicate significant correlation.
Eigenvalue
Variable LOR
LC Lgl
LPL
WOR WglB WPF WIG WglE LPA LPF
PC1
–0.2325 –0.0669 –0.2144 –0.2041 –0.2114 –0.2398 0.2471 0.0805
–0.2605 0.4844 0.6178
Lower limit –0.2807
–0.2840 0.4465 0.5938
–0.0877 –0.2384 –0.2664 –0.2354 –0.2600 0.1884 0.0244
Upper limit –0.1838
–0.2351 0.5200 0.6385
–0.0457 –0.1890 –0.1397 –0.1878 –0.2198 0.3041 0.1381
PC2
–0.2331 –0.1639 –0.4237 0.2433
–0.1428 –0.0087 –0.0855 0.7873
–0.1209 0.1328 0.0151
Lower limit –0.3899
–0.3163 –0.2215 –0.7499 –0.2212 –0.2303 –0.1263 –0.1474
–0.1123 –0.1785 0.5004
Upper limit 0.1370
–0.1247 –0.0782 –0.0221 0.6976
0.0961 0.0243 0.9410
–0.0049 0.3589 0.1683
PC1
–0.7316* –0.6607* –0.9000* –0.5737 –0.8618* –0.9008* 0.7270 0.3030
–0.8898* 0.9601* 0.9854*
Correlation PC2
–0.1594 –0.0306 –0.1275
–0.3375 –0.2186 –0.4429 0.3258
–0.1468 0.0936 0.0085
Figure 3. Scatter plot of the two first components of the PCAs: (1) analysis using log-transformed raw data; (2) analysis using log-transformed data corrected by the geometric mean (GMD); (3) analysis using log-transformed ratio variables (RD). Black circles: Bienvillia Clark; white squares: Parabolinella Brogger; black star: Holotype of P.? triarthroides (CPBA 5); gray star: P.? triarthroides (CPBA 54); gray circle: P.? triarthroides.
0.7858*
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