Biodiversity Data Journal :
Research Article
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Corresponding author: Truong Son Nguyen (truongsoniebr@gmail.com)
Academic editor: Miguel Camacho Sanchez
Received: 08 Mar 2024 | Accepted: 14 Jun 2024 | Published: 27 Jun 2024
© 2024 Huong Yen Vu, Tuan Hai Bui, Trung Thanh Hoang, Kim Luong Vu, Truong Son Nguyen
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:
Vu HY, Bui TH, Hoang TT, Vu KL, Nguyen TS (2024) Multivariate analysis of craniodental morphology in mouse-eared bats (Chiroptera, Vespertilionidae, Myotis) from Vietnam. Biodiversity Data Journal 12: e122597. https://doi.org/10.3897/BDJ.12.e122597
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This study conducted biostatistical multivariate analyses on 23 craniodental morphological measurements from 209 specimens to study interspecific variations amongst 15 bat species of the genus Myotis in Vietnam. Univariate and multivariate analyses demonstrated that the studied species can be divided into four groups as follows: extra-large-sized species (M. chinensis), large-sized species (M. pilosus, M. indochinensis and M. annectans), medium-sized species (M. altarium, M. hasseltii, M. montivagus, M. horsfieldii, M. ater, M. laniger and M. muricola) and small-sized species (M. annamiticus, M. aff. siligorensis, M. rosseti and M. alticraniatus). Our data revealed that the main craniodental features contributing to the variations in distinguishing Myotis species are the width of the anterior palatal, least height of the coronoid process, length of the upper and lower canine-premolar, zygomatic width and width across the upper canines and lower premolar-molar length. Based on patterns of morphological differences, we conducted comparisons between morphometrically closely resembling species pairs and further discussed additional characteristics that are expected to support the taxonomy and systematics of Vietnamese Myotis bats.
skull variation, PCA, comparison, dentition, small mammal
The vespertilionid bats of the genus Myotis, with approximately 139 extant species, are widely distributed throughout the world, including Vietnam (
In Vietnam, 72 species of vespertilionoid bats have been discovered, of which 19 species belong to the genus Myotis, including: Myotis altarium, M. alticraniatus, M. annamiticus, M. annatessae, M. ancricola, M. annectans, M. ater, M. chinensis, M. formosus, M. hasseltii, M. horsfieldii, M. indochinensis, M. laniger, M. montivagus, M. muricola, M. phanluongi, M. pilosus, M. rosseti and M. rufoniger (
Many Myotis species exhibit complex morphological and genetic characteristics that warrant further research. Prior to 2008, species classification within the genus Myotis primarily relied on external morphological traits such as fur colour, forearm length, tibia length, hind-foot length, ear length, the feature attachment of the wing membrane to the leg, characteristics of the calcar lobe in the wing membrane and craniodental morphology. Due to the similarity of some morphological characteristics and the complexity of molecular analysis amongst closely-related Myotis bats (
The present study was implemented using a total of 209 skull specimens from the mouse-eared bats of genus Myotis, which were collected from 25 localities in 21 provinces of Vietnam (Fig.
Character |
Explanation |
Cranium |
|
STOTL |
Total length of the skull (from the anterior rim of the alveolus of the first upper incisor to the most projecting point of the occipital region). |
GTL |
Greatest length of skull (from the front of the 1st upper incisor to the most projecting point of the occipital region). |
CCL |
Condylo-canine length (distance from the exoccipital condyle to the most anterior part of the canine). |
CM3L |
Maxillary toothrow length (distance from the front of upper canine to the back of the crown of the third molar). |
CP4L |
Upper canine-premolar length (from the front of the upper canine to the back of the crown of the last premolar). |
P4M3L |
Upper molariform toothrow length (from the posterior upper premolar to the last molar). |
M1M3L |
Upper molar crown length (from the front of the 1st upper molar to the last molar). |
MAW |
Mastoid width (greatest distance across the mastoid region). |
BCH |
Braincase height (from the basisphenoid at the level of the hamular processes to the highest part of the skull, including the sagittal crest, if present). |
BB |
Breadth of braincase at the posterior roots of zygomatic arches. |
GBCW |
Greatest width of the braincase. |
IOW |
Interorbital width (least width of the interorbital constriction). |
ZYW |
Zygomatic width (greatest width of the skull across the zygomatic arches). |
PWC1C1 |
Anterior palatal width (least distance between the inner borders of the upper canines). |
PWM3M3 |
Posterior palatal width (least distance between the inner borders of the last upper molars). |
C1C1W |
Width across the upper canines (greatest width across the outer borders of the upper canines). |
M3M3W |
Width across the upper molars (greatest width across the outer crowns of the last upper molars). |
Mandible |
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ML |
Mandible length (distance from the anterior rim of the alveolus of the first lower incisor to the most posterior part of the condyle). |
CPH |
Least height of the coronoid process (distance from the tip of the coronoid process to the apex of the indentation on the inferior surface of the ramus adjacent to the angular process). |
cm3L |
Mandibular tooth row length (distance from the front of the lower canine to the back of the crown of the third lower molar). |
cp4L |
Lower canine-premolar length (distance from the front of the lower canine to the back of the crown of the posterior premolar). |
p4m3L |
Lower molariform toothrow length (Posterior lower premolar to the last lower molar length). |
m1m3L |
Lower molars crown length. |
Minimum, maximum, mean values, standard deviations and interquartile range (IQR) for 23 measurements were calculated using Microsoft® Excel version Office 2021 (Microsoft, Redmond, WA, USA). Multivariate analysis of variance (MANOVA) using log-transformed craniodental measurements indicated non-significant sexual-dimorphism differences for five out of 15 Myotis species with sufficiently large sample sizes. Thus, our study was performed on all specimens without sexual discrimination in statistical analyses. Univariate analyses and multivariate analyses of craniodental morphology using Principal Component Analysis (PCA) were conducted to evaluate correlations between interspecific morphometric variations of Vietnamese Myotis bats. Differences in the mean values were examined by analysis of variance (One-way ANOVA) and Tukey’s pairwise test of variance (significant at p < 0.05). Pairwise comparisons were carried out using F and t-tests (P < 0.05) amongst taxa for difference comparison. All these analyses were performed using the PAST software ver.4.13 (
Descriptive statistics for craniodental measurements are presented in Table
Minimum, maximum in the upper row and mean and standard deviation (if n ≥ 2) in the bottom row of 23 craniodental measurements in 15 mouse-eared bat species from Vietnam.
Character |
M. alticraniatus |
M. rosseti |
M. aff. siligorensis |
M. annamiticus |
M. montivagus |
N | 19 | 2 | 2 | 5 | 1 |
STOTL | 11.86 - 12.29 | 12.33 - 12.65 | 12.4 - 12.81 | 13.01 - 13.77 | 14.97 |
12.06 ± 0.12 | 12.49 ± 0.23 | 12.61 ± 0.29 | 13.4 ± 0.33 | ||
GTL | 11.92 - 12.53 | 12.54 - 12.86 | 12.64 - 12.91 | 13.29 - 13.91 | 15.33 |
12.21 ± 0.16 | 12.7 ± 0.23 | 12.78 ± 0.19 | 13.65 ± 0.3 | ||
CCL | 9.09 - 9.66 | 9.48 - 9.58 | 9.71 - 9.93 | 10.06 - 10.67 | 12.03 |
9.38 ± 0.15 | 9.53 ± 0.07 | 9.82 ± 0.16 | 10.37 ± 0.29 | ||
CM3L | 4.33 - 4.67 | 4.34 - 4.47 | 4.47 - 4.62 | 4.97 - 5.16 | 5.76 |
4.46 ± 0.1 | 4.41 ± 0.09 | 4.55 ± 0.11 | 5.09 ± 0.07 | ||
CP4L | 1.75 - 2.21 | 1.69 - 1.76 | 1.84 - 1.89 | 2.41 - 2.61 | 2.77 |
2.04 ± 0.12 | 1.73 ± 0.05 | 1.87 ± 0.04 | 2.53 ± 0.08 | ||
P4M3L | 3.08 - 3.31 | 3.27 - 3.44 | 3.38 - 3.51 | 3.34 - 3.51 | 4.44 |
3.18 ± 0.07 | 3.36 ± 0.12 | 3.45 ± 0.09 | 3.42 ± 0.07 | ||
M1M3L | 2.54 - 2.78 | 2.77 - 2.81 | 2.75 - 2.92 | 2.67 - 2.83 | 3.56 |
2.66 ± 0.06 | 2.79 ± 0.03 | 2.84 ± 0.12 | 2.78 ± 0.06 | ||
MAW | 6.15 - 6.72 | 6.87 - 6.93 | 6.58 - 6.69 | 6.48 - 6.98 | 7.9 |
6.39 ± 0.15 | 6.9 ± 0.04 | 6.64 ± 0.08 | 6.77 ± 0.2 | ||
BCH | 4.39 - 5.07 | 4.8 | 4.93 - 4.98 | 4.93 - 5.34 | 5.46 |
4.63 ± 0.19 | 4.8 | 4.96 ± 0.04 | 5.15 ± 0.16 | ||
BB | 5.73 - 6.38 | 6.73 - 6.75 | 6.22 - 6.37 | 6.29 - 6.58 | 7.57 |
6.02 ± 0.17 | 6.74 ± 0.01 | 6.3 ± 0.11 | 6.44 ± 0.12 | ||
GBCW | 5.71 - 6.37 | 6.35 - 6.48 | 6.47 - 6.54 | 6.54 - 6.81 | 7.13 |
5.96 ± 0.15 | 6.42 ± 0.09 | 6.51 ± 0.05 | 6.67 ± 0.11 | ||
IOW | 2.13 - 3.15 | 3.35 | 3.12 - 3.22 | 3.16 - 3.32 | 3.65 |
2.94 ± 0.22 | 3.35 | 3.17 ± 0.07 | 3.25 ± 0.08 | ||
ZYW | 6.87 - 7.84 | 8.05 - 8.36 | 7.42 - 7.49 | 7.19 - 7.67 | 10.09 |
7.1 ± 0.23 | 8.21 ± 0.22 | 7.46 ± 0.05 | 7.47 ± 0.19 | ||
PWC1C1 | 1.93 - 2.38 | 2.11 - 2.15 | 2.41 - 2.54 | 2.33 - 2.59 | 2.33 |
2.1 ± 0.11 | 2.13 ± 0.03 | 2.48 ± 0.09 | 2.49 ± 0.11 | ||
PWM3M3 | 2.31 - 2.8 | 2.71 - 2.79 | 2.61 - 2.76 | 2.69 - 2.95 | 3.31 |
2.56 ± 0.13 | 2.75 ± 0.06 | 2.69 ± 0.11 | 2.84 ± 0.11 | ||
C1C1W | 2.66 - 3.06 | 3.24 - 3.44 | 3.45 - 3.54 | 3.1 - 3.45 | 3.91 |
2.95 ± 0.1 | 3.34 ± 0.14 | 3.5 ± 0.06 | 3.3 ± 0.15 | ||
M3M3W | 4.55 - 5.02 | 5.06 - 5.24 | 4.98 - 5.05 | 4.92 - 5.11 | 6.46 |
4.77 ± 0.14 | 5.15 ± 0.13 | 5.02 ± 0.05 | 5.03 ± 0.07 | ||
ML | 8.24 - 8.68 | 8.63 - 9.11 | 8.78 - 9.07 | 9.14 - 9.58 | 11.63 |
8.52 ± 0.11 | 8.87 ± 0.34 | 8.93 ± 0.21 | 9.39 ± 0.18 | ||
CPH | 2.05 - 2.26 | 2.6 - 2.61 | 2.29 - 2.35 | 2.16 - 2.58 | 3.74 |
2.14 ± 0.07 | 2.61 ± 0.01 | 2.32 ± 0.04 | 2.35 ± 0.15 | ||
cm3L | 4.38 - 4.82 | 4.52 - 4.65 | 4.61 - 5.03 | 5.05 - 5.36 | 6.45 |
4.62 ± 0.11 | 4.59 ± 0.09 | 4.82 ± 0.3 | 5.26 ± 0.13 | ||
cp4L | 1.69 - 2.01 | 1.61 - 1.62 | 1.83 - 1.93 | 1.98 - 2.46 | 2.38 |
1.79 ± 0.09 | 1.62 ± 0.01 | 1.88 ± 0.07 | 2.28 ± 0.18 | ||
p4m3L | 3.11 - 3.62 | 3.42 - 3.56 | 3.61 - 3.69 | 3.53 - 3.65 | 4.7 |
3.38 ± 0.1 | 3.49 ± 0.1 | 3.65 ± 0.06 | 3.58 ± 0.05 | ||
m1m3L | 2.68 - 2.95 | 2.87 - 3.06 | 3.09 - 3.15 | 2.87 - 3.06 | 3.76 |
2.84 ± 0.08 | 2.97 ± 0.13 | 3.12 ± 0.04 | 2.98 ± 0.08 | ||
Character |
M. muricola |
M. laniger |
M. ater |
M. horsfieldii |
M. altarium |
N | 30 | 85 | 26 | 13 | 1 |
STOTL | 13.09 - 14.04 | 13.36 - 14.54 | 14.04 - 15.09 | 13.85 - 15.1 | 15.19 |
13.52 ± 0.22 | 14.09 ± 0.26 | 14.48 ± 0.27 | 14.61 ± 0.37 | ||
GTL | 13.39 - 14.32 | 13.81 - 14.78 | 14.31 - 15.34 | 13.98 - 15.36 | 15.69 |
13.81 ± 0.2 | 14.33 ± 0.22 | 14.78 ± 0.25 | 14.88 ± 0.41 | ||
CCL | 10.48 - 11.21 | 10.65 - 11.69 | 11.21 - 12.11 | 11.01 - 12.05 | 12.45 |
10.8 ± 0.19 | 11.24 ± 0.21 | 11.6 ± 0.21 | 11.51 ± 0.28 | ||
CM3L | 4.97 - 5.33 | 5.25 - 5.8 | 5.23 - 5.81 | 5.28 - 5.68 | 6.21 |
5.18 ± 0.1 | 5.56 ± 0.11 | 5.58 ± 0.13 | 5.53 ± 0.14 | ||
CP4L | 2.16 - 2.62 | 2.51 - 2.95 | 2.21 - 2.7 | 2.27 - 2.79 | 3.15 |
2.4 ± 0.1 | 2.69 ± 0.09 | 2.49 ± 0.11 | 2.55 ± 0.13 | ||
P4M3L | 3.53 - 3.99 | 3.66 - 4.11 | 3.96 - 4.46 | 3.81 - 4.12 | 4.24 |
3.81 ± 0.11 | 3.87 ± 0.1 | 4.19 ± 0.12 | 3.95 ± 0.1 | ||
M1M3L | 2.89 - 3.34 | 2.91 - 3.31 | 3.25 - 3.62 | 3.13 - 3.39 | 3.44 |
3.14 ± 0.09 | 3.15 ± 0.08 | 3.45 ± 0.09 | 3.24 ± 0.08 | ||
MAW | 6.49 - 7.38 | 6.78 - 7.47 | 7.09 - 7.97 | 7.35 - 7.91 | 8.23 |
7.09 ± 0.18 | 7.16 ± 0.15 | 7.54 ± 0.21 | 7.66 ± 0.19 | ||
BCH | 4.42 - 5.15 | 4.88 - 5.92 | 4.95 - 5.59 | 5.14 - 5.87 | 5.95 |
4.85 ± 0.16 | 5.38 ± 0.18 | 5.31 ± 0.16 | 5.54 ± 0.24 | ||
BB | 6.55 - 7.14 | 6.43 - 7.28 | 6.86 - 7.62 | 7.15 - 7.65 | 8.26 |
6.87 ± 0.16 | 6.74 ± 0.17 | 7.37 ± 0.2 | 7.36 ± 0.14 | ||
GBCW | 6.01 - 6.74 | 6.73 - 7.37 | 6.37 - 7.05 | 7.05 - 7.58 | 7.85 |
6.35 ± 0.17 | 7.06 ± 0.12 | 6.78 ± 0.19 | 7.31 ± 0.18 | ||
IOW | 3.18 - 3.54 | 3.18 - 3.76 | 3.23 - 3.94 | 3.37 - 3.81 | 4.74 |
3.37 ± 0.08 | 3.39 ± 0.11 | 3.57 ± 0.17 | 3.62 ± 0.12 | ||
ZYW | 7.88 - 9.05 | 7.75 - 8.59 | 8.99 - 9.74 | 8.68 - 9.38 | 10.01 |
8.68 ± 0.25 | 8.19 ± 0.17 | 9.46 ± 0.2 | 8.98 ± 0.22 | ||
PWC1C1 | 1.74 - 2.38 | 2.14 - 2.68 | 1.95 - 2.61 | 2.16 - 2.68 | 2.67 |
2 ± 0.14 | 2.34 ± 0.11 | 2.25 ± 0.14 | 2.47 ± 0.17 | ||
PWM3M3 | 2.71 - 3.28 | 2.73 - 3.32 | 2.88 - 3.26 | 2.97 - 3.34 | 3.63 |
2.97 ± 0.13 | 2.99 ± 0.11 | 3.1 ± 0.09 | 3.18 ± 0.11 | ||
C1C1W | 3.21 - 3.71 | 3.22 - 3.79 | 3.62 - 4.23 | 3.71 - 4.34 | 3.92 |
3.47 ± 0.13 | 3.53 ± 0.12 | 4.02 ± 0.12 | 4.06 ± 0.2 | ||
M3M3W | 5.22 - 5.9 | 5.13 - 5.76 | 5.87 - 6.28 | 5.55 - 6.08 | 6.62 |
5.62 ± 0.17 | 5.46 ± 0.15 | 6.06 ± 0.12 | 5.81 ± 0.16 | ||
ML | 9.65 - 10.36 | 9.76 - 11.01 | 10.43 - 11.44 | 9.99 - 11.11 | 11.85 |
10.04 ± 0.22 | 10.28 ± 0.22 | 10.92 ± 0.22 | 10.61 ± 0.34 | ||
CPH | 2.65 - 3.17 | 2.55 - 2.97 | 3.13 - 3.62 | 2.82 - 3.28 | 3.61 |
2.95 ± 0.13 | 2.72 ± 0.09 | 3.37 ± 0.13 | 3.08 ± 0.15 | ||
cm3L | 4.11 - 5.91 | 5.14 - 6.29 | 5.69 - 6.43 | 5.51 - 6.12 | 6.68 |
5.45 ± 0.29 | 5.73 ± 0.17 | 5.92 ± 0.17 | 5.87 ± 0.17 | ||
cp4L | 1.91 - 2.48 | 2 - 2.54 | 2.09 - 2.45 | 2.15 - 2.62 | 3.06 |
2.15 ± 0.12 | 2.33 ± 0.11 | 2.29 ± 0.1 | 2.4 ± 0.12 | ||
p4m3L | 3.81 - 4.36 | 3.87 - 4.3 | 4.13 - 4.6 | 3.96 - 4.54 | 4.59 |
4.03 ± 0.13 | 4.11 ± 0.09 | 4.41 ± 0.11 | 4.24 ± 0.16 | ||
m1m3L | 3.22 - 3.52 | 3.13 - 3.73 | 3.44 - 3.91 | 3.35 - 3.73 | 3.87 |
3.37 ± 0.07 | 3.41 ± 0.09 | 3.69 ± 0.11 | 3.5 ± 0.11 | ||
Character |
M. hasseltii |
M. annectans |
M. indochinensis |
M. pilosus |
M. chinensis |
N | 2 | 1 | 15 | 3 | 4 |
STOTL | 15.62 - 15.67 | 17.69 | 16.96 - 17.98 | 19.41 - 20.24 | 22.19 - 24.61 |
15.65 ± 0.04 | 17.51 ± 0.36 | 19.83 ± 0.42 | 23.54 ± 1 | ||
GTL | 15.87 - 16.01 | 17.91 | 17.41 - 18.52 | 19.68 - 20.51 | 22.81 - 25.01 |
15.94 ± 0.1 | 18.04 ± 0.37 | 20.11 ± 0.42 | 23.97 ± 0.9 | ||
CCL | 12.11 - 12.29 | 14.33 | 13.8 - 14.72 | 15.9 - 16.29 | 18.83 - 19.68 |
12.2 ± 0.13 | 14.33 ± 0.28 | 16.1 ± 0.2 | 19.36 ± 0.37 | ||
CM3L | 5.72 - 5.87 | 6.99 | 6.86 - 7.41 | 8.01 - 8.37 | 9.57 - 9.97 |
5.8 ± 0.11 | 7.13 ± 0.17 | 8.18 ± 0.18 | 9.78 ± 0.2 | ||
CP4L | 2.49 - 2.82 | 3.34 | 2.89 - 3.41 | 3.57 - 3.84 | 4.53 - 4.79 |
2.66 ± 0.23 | 3.17 ± 0.15 | 3.67 ± 0.15 | 4.69 ± 0.11 | ||
P4M3L | 3.93 - 4.33 | 5.21 | 5.09 - 5.42 | 5.81 - 6.14 | 6.37 - 7.05 |
4.13 ± 0.28 | 5.27 ± 0.11 | 5.95 ± 0.17 | 6.7 ± 0.31 | ||
M1M3L | 3.43 - 3.54 | 4.22 | 4.18 - 4.53 | 4.81 - 5.02 | 4.96 - 5.69 |
3.49 ± 0.08 | 4.3 ± 0.09 | 4.89 ± 0.11 | 5.45 ± 0.33 | ||
MAW | 8.21 - 8.27 | 8.98 | 8.64 - 9.63 | 9.66 - 10.11 | 12.01 - 12.14 |
8.24 ± 0.04 | 9.05 ± 0.3 | 9.91 ± 0.23 | 12.08 ± 0.05 | ||
BCH | 6.05 - 6.24 | 5.86 | 5.81 - 6.68 | 6.64 - 7.04 | 8.31 - 9.21 |
6.15 ± 0.13 | 6.27 ± 0.26 | 6.81 ± 0.21 | 8.77 ± 0.42 | ||
BB | 7.76 - 7.98 | 8.87 | 8.56 - 9.42 | 9.16 - 9.62 | 11.06 - 11.59 |
7.87 ± 0.16 | 9.07 ± 0.25 | 9.43 ± 0.24 | 11.37 ± 0.22 | ||
GBCW | 7.48 - 8.03 | 8.29 | 7.53 - 8.35 | 9.26 - 9.84 | 10.44 - 10.57 |
7.76 ± 0.39 | 7.89 ± 0.24 | 9.58 ± 0.29 | 10.51 ± 0.05 | ||
IOW | 3.8 - 4.08 | 4.34 | 4.17 - 4.66 | 4.85 - 4.86 | 5.29 - 5.57 |
3.94 ± 0.2 | 4.38 ± 0.14 | 4.86 ± 0.01 | 5.45 ± 0.12 | ||
ZYW | 9.61 - 9.82 | 11.48 | 11.57 - 12.71 | 12.34 - 12.77 | 15.81 - 16.22 |
9.72 ± 0.15 | 11.91 ± 0.3 | 12.62 ± 0.25 | 15.98 ± 0.19 | ||
PWC1C1 | 2.33 - 2.51 | 2.86 | 2.37 - 3.33 | 3.29 - 3.85 | 3.73 - 3.91 |
2.42 ± 0.13 | 2.77 ± 0.22 | 3.58 ± 0.28 | 3.83 ± 0.08 | ||
PWM3M3 | 3.2 - 3.51 | 3.91 | 3.64 - 4.28 | 3.92 - 4.43 | 4.62 - 5.03 |
3.36 ± 0.22 | 4.01 ± 0.14 | 4.18 ± 0.26 | 4.85 ± 0.21 | ||
C1C1W | 4.19 - 4.21 | 4.98 | 4.75 - 5.18 | 5.33 - 5.69 | 5.89 - 6.48 |
4.2 ± 0.01 | 4.94 ± 0.16 | 5.54 ± 0.19 | 6.18 ± 0.27 | ||
M3M3W | 6.07 - 6.38 | 7.56 | 7.63 - 8.06 | 7.57 - 8.23 | 9.3 - 10.06 |
6.23 ± 0.22 | 7.76 ± 0.12 | 7.98 ± 0.36 | 9.69 ± 0.35 | ||
ML | 10.95 - 11.39 | 13.28 | 12.96 - 14.03 | 14.9 - 15.51 | 18.52 - 18.91 |
11.17 ± 0.31 | 13.64 ± 0.32 | 15.18 ± 0.31 | 18.68 ± 0.17 | ||
CPH | 3.34 - 3.46 | 4.08 | 4.11 - 4.67 | 4.41 - 4.72 | 6.16 - 6.39 |
3.4 ± 0.08 | 4.44 ± 0.16 | 4.56 ± 0.16 | 6.25 ± 0.1 | ||
cm3L | 6.15 - 6.35 | 7.45 | 7.27 - 7.89 | 8.73 - 8.85 | 10.17 - 10.68 |
6.25 ± 0.14 | 7.59 ± 0.17 | 8.8 ± 0.06 | 10.41 ± 0.27 | ||
cp4L | 2.45 - 2.6 | 2.95 | 2.81 - 3.22 | 3.34 - 3.72 | 4.21 - 4.31 |
2.53 ± 0.11 | 2.99 ± 0.11 | 3.48 ± 0.21 | 4.25 ± 0.05 | ||
p4m3L | 4.4 - 4.58 | 5.72 | 5.39 - 5.97 | 6.19 - 6.31 | 7.16 - 7.81 |
4.49 ± 0.13 | 5.63 ± 0.14 | 6.26 ± 0.06 | 7.44 ± 0.29 | ||
m1m3L | 3.71 - 3.82 | 4.66 | 4.47 - 4.83 | 5.17 - 5.35 | 5.86 - 6.43 |
3.77 ± 0.08 | 4.67 ± 0.1 | 5.25 ± 0.09 | 6.05 ± 0.26 |
- Group S (small size, STOTL: Mean = 12.45, range = 11.86–13.77, ML < 9.58 mm) includes four species of M. alticraniatus, M. rosseti, M. aff. siligorensis and M. annamiticus.
- Group M (medium size, STOTL: 14.123, 13.09–15.67, ML: 10.394, 9.65–11.85) includes seven species in the descending order: M. altarium, M. hasseltii, M. montivagus, M. horsfieldii, M. ater, M. laniger and M. muricola.
- Group L (large size, STOTL: 17.89, 16.96–20.24, ML: 13.87, 12.96–15.51) comprises three distinctive species: M. pilosus, M. indochinensis and M. annectans.
- Group XL (extra-large size, STOTL: 23.54, 22.19–24.61, ML: 18.68, 18.52–18.91) comprises one species, Myotis chinensis, which was considered the greatest and most noteworthy difference in size compared to other Myotis species of the aforementioned groups, as indicated by measurements.
The differences amongst these four groups can be easily detected by direct observation of the appearances of the skulls (Fig.
The factor loadings for log-transformed measurements are presented in Table
Character loadings for log-transformed measurements (PCs 1, 2) of 15 Vietnamese Myotis, Group S, Group M and Group L.
Character |
All Taxa |
Group S |
Group M |
Group L |
||||
PC 1 |
PC 2 |
PC 1 |
PC 2 |
PC 1 |
PC 2 |
PC 1 |
PC 2 |
|
STOTL |
0.179 |
0.072 |
0.183 |
0.012 |
0.146 |
0.087 |
0.212 |
0.077 |
GTL |
0.183 |
0.054 |
0.193 |
0.019 |
0.152 |
0.072 |
0.189 |
0.089 |
CCL |
0.197 |
0.063 |
0.175 |
-0.019 |
0.149 |
0.081 |
0.197 |
0.068 |
CM3L |
0.214 |
0.161 |
0.215 |
-0.120 |
0.119 |
0.181 |
0.231 |
0.136 |
CP4L |
0.209 |
0.421 |
0.354 |
-0.588 |
0.036 |
0.383 |
0.225 |
0.409 |
P4M3L |
0.221 |
-0.069 |
0.134 |
0.084 |
0.193 |
-0.029 |
0.203 |
0.145 |
M1M3L |
0.215 |
-0.118 |
0.081 |
0.111 |
0.205 |
-0.079 |
0.210 |
0.179 |
MAW |
0.173 |
-0.030 |
0.114 |
0.142 |
0.194 |
0.003 |
0.163 |
-0.132 |
BCH |
0.157 |
0.244 |
0.206 |
0.078 |
0.162 |
0.305 |
0.160 |
0.016 |
BB |
0.186 |
-0.148 |
0.127 |
0.199 |
0.237 |
-0.096 |
0.075 |
-0.068 |
GBCW |
0.145 |
0.267 |
0.201 |
0.140 |
0.118 |
0.319 |
0.319 |
-0.070 |
IOW |
0.181 |
-0.033 |
0.227 |
0.297 |
0.208 |
0.017 |
0.173 |
0.012 |
ZYW |
0.235 |
-0.283 |
0.110 |
0.287 |
0.287 |
-0.247 |
0.112 |
-0.052 |
PWC1C1 |
0.161 |
0.430 |
0.320 |
0.085 |
0.199 |
0.511 |
0.448 |
-0.727 |
PWM3M3 |
0.191 |
-0.038 |
0.204 |
0.156 |
0.168 |
0.019 |
0.089 |
-0.194 |
C1C1W |
0.228 |
-0.141 |
0.213 |
0.221 |
0.354 |
-0.050 |
0.196 |
-0.010 |
M3M3W |
0.213 |
-0.193 |
0.102 |
0.139 |
0.234 |
-0.142 |
0.059 |
-0.003 |
ML |
0.217 |
-0.005 |
0.170 |
0.022 |
0.191 |
0.017 |
0.188 |
0.052 |
CPH |
0.313 |
-0.432 |
0.195 |
0.339 |
0.405 |
-0.390 |
0.089 |
0.195 |
cm3L |
0.228 |
0.096 |
0.228 |
-0.103 |
0.179 |
0.118 |
0.248 |
0.061 |
cp4L |
0.233 |
0.287 |
0.426 |
-0.360 |
0.156 |
0.277 |
0.261 |
0.191 |
p4m3L |
0.229 |
-0.053 |
0.123 |
0.050 |
0.193 |
-0.015 |
0.175 |
0.053 |
m1m3L |
0.222 |
-0.081 |
0.105 |
0.073 |
0.193 |
-0.042 |
0.187 |
0.122 |
% Variance |
91.36 |
3.68 |
59.63 |
19.49 |
48.73 |
25.76 |
75.24 |
8.55 |
The PC scatterplots distinguished large- and extra-large-sized Myotis being greater compared to two smaller Myotis groups (Fig.
Bivariate scatterplots of PC 1 and PC 2 completely separated the four groups by considering only the PC 1 values (Fig.
Descriptive statistics of first two principal components of 15 studied Myotis in Vietnam.
Species | PC1 | PC2 |
M. alticraniatus | –1.73 - –1.34 | –0.72 - 0.38 |
–1.52 ± 0.11 | –0.09 ± 0.28 | |
M. rosseti | –1.25 - –1.06 | –2.11 - –2.1 |
–1.16 ± 0.13 | –2.11 ± 0.003 | |
M. aff. siligorensis |
–1.13 - –1.02 |
–0.33 - –0.09 |
–1.07 ± 0.08 | –0.21 ± 0.17 | |
M. muricola | –0.71 - –0.23 | –1.87 - –0.51 |
–0.38 ± 0.11 | –1.24 ± 0.34 | |
M. laniger | –0.45 - 0.01 | 0.38 - 1.31 |
–0.19 ± 0.11 | 0.86 ± 0.22 | |
M. ater | –0.06 - 0.43 | –1.84 - –0.68 |
0.23 ± 0.12 | –1.27 ± 0.303 | |
M. horsfieldii | 0.23 ± 0.12 | –0.49 - 0.52 |
0.16 ± 0.15 | 0.03 ± 0.33 | |
M. montivagus | 0.59 | –1.1296 |
M. hasseltii | 0.59 - 0.66 | 0.23 - 0.06 |
0.63 ± 0.046 | 0.08 ± 0.21 | |
M. altarium | 0.97 | 0.76 |
M. annectans |
1.8 |
–0.16 |
M. indochinensis | 1.68 - 2.09 | –1.34 - –0.21 |
1.89 ± 0.12 | –0.82 ± 0.28 | |
M. pilosus |
2.53 - 2.81 |
0.97 - 1.13 |
2.68 ± 0.14 | 1.07 ± 0.08 | |
M. chinensis |
3.78 - 4.12 |
1.11 - 1.27 |
3.99 ± 0.15 | 1.19 ± 0.07 |
The range and mean value of PC 1 scores showed craniodental-sized variation of each mouse-eared bat in Fig.
The complete separation amongst the studied species is further clarified in the plots in Fig.
The PCA result of group S (Fig.
One-way ANOVA detected significant differences amongst all four small Myotis species (p < 0.001) in PC 1, which represented the apparent distinctions between M. alticraniatus and M. aff. siligorensis (One-way ANOVA, F = 23.19, p < 0.001), M. alticraniatus and M. annamiticus (F = 163.9, p < 0.001), between M. annamiticus and 2 species of M. rosseti, M. aff. siligorensis (F = 26.24, p < 0.001) (Fig.
The scatterplot of PCA for medium-sized Myotis between PC 1 and PC 2 displayed the absolute differences and plainly separating these seven sub-groups within non-intersecting clusters (Fig.
One-way ANOVA test and Mann-Whitney pairwise test indicated significant differences between pairwise species according to PC 1 and PC 2, as shown in the following Table
Significance level when comparing PC1 and PC2 scores between species of Myotis.
M. hasseltii | M. altarium | M. montivagus | M. horsfieldii | M. ater | M. laniger | M. muricola | |
M. hasseltii | s, s | n, s | s, n | s, s | s, n | s, s | |
M. altarium | s, s | s, s | s, s | s, s | s, s | ||
M. montivagus | s, s | s, n | s, s | s, n | |||
M. horsfieldii | n, s | s, n | s, s | ||||
M. ater | s, s | s, n | |||||
M. laniger | n, s | ||||||
M. muricola |
One-way ANOVA with PC 1 signified the distinct differences between M. muricola and M. ater (F = 407.3, p < 0.01), M. muricola and M. horsfieldii (F = 150, p < 0.01), M. laniger and M. ater (F = 512.3, p < 0.01), M. laniger and M. horsfieldii (F = 172.3, p < 0.01) (Fig.
Scatter plots between PC 1 and PC 2, based on PCA results, showed a clear separation of the M. pilosus sub-group with the M. indochinensis sub-group and a point of M. annectans completely mosaic within it (Fig.
In PCA, PC 1 explained 75.24% of the interspecific variation in craniodental measurements, but this consequence arose because of the completely different cranium and mandible sizes of pilosus from the other two species (Fig.
Dentition characteristics, coronoid process and braincase height have often been mentioned as informative diagnostic features in Myotis species and in other bats and small mammals such as rodents and insectivores. The associated craniodental measurements have been indicated to be suitable for species discrimination, alongside external morphological characters (
In group S, despite STOTL and ML representing M. alticraniatus as the smallest species, our PCA detected that CP4L and cp4L contributed the most differences, indicating that M. rosseti had the smallest canine-premolar lengths. This can be explained by M. rosseti being the only species of genus Myotis that lacks the third premolars on both the maxilla and mandible. Likewise, CP4L displayed that M. aff. siligorensis was partially smaller than M. alticraniatus due to the lack of third upper premolars, leading to a significant difference from M. rosseti. In contrast, CPH was distinctly larger in M. rosseti, although it was observed to be smaller in the remaining three Myotis. Myotis rosseti was characterised by having a larger CPH/cp4L and IOW/cp4L ratio compared to the other three small-sized species (Table
In this study, two specimens of Myotis aff. siligorensis collected on Phu Quoc Island (Kien Giang Province) were examined. Due to abnormalities in the dentition structure and craniodental characteristics, these specimens were listed in "siligorensis species complex" (
In comparison to M. alticraniatus, these two smallest Vietnamese Myotis in our study have relatively similar cranial appearances, although these two specimens of M. aff. siligorensis exhibit significantly greater craniodental characteristics and a dissimilar dentition formula (Fig.
Due to the noticeable differences in craniodental morphology compared to the other 14 Myotis species in this study, further analysis of the taxonomy of these two Myotis aff. siligorensis specimens is needed. Simultaneously, PCA analyses are necessary to be conducted with three Vietnamese mouse-eared bats with comparable size to Myotis aff. siligorensis, which are not reported in this study due to insufficient specimens, namely: Myotis phanluongi, M. ancricola and M. annatessae in subsequent taxonomic investigations.
In group M, PCA results indicated dentition features, namely: CP4L, C1C1W, PWC1C1 and CPH, contributed the most differences amongst species, considering the interference between two first principal components (Table
In group L, dentition characteristics (CP4L, PWC1C1, CPH and cm3L) contributed the most differences, representing Myotis pilosus as being much greater than the others. Likewise, M. pilosus is distinguished by a distinctly larger cranium size and skull appearance compared to the other two species in the group (Fig.
Cranial morphology: The skull and mandible sizes of both species almost completely overlap (Table
Dental morphology: The dentition of Myotis annectans tends to shorten and widen, while in M. indochinensis, the teeth are more robust, taller and more pointed. The canines and large premolars are more developed in M. indochinensis compared to M. annectans. The c1 of M. annectans are insignificantly shorter in height and barely exceed the height of p4, while the c1 of M. indochinensis is pointier, approximately reaching the height of p4. The most basic characteristic that distinguishes these two species is that M. annectans has reduced dentition, with P3 and p3 of both the maxilla and mandible being typically absent, although they remain intact in M. indochinensis.
Our analyses demonstrated craniodental morphology variations of 15 Myotis species in Vietnam, which could be divided into four group clusters with distinct sizes: small-sized, medium-sized, large-sized, extra-large-sized, all with significant interspecific variances. Multivariate analyses also specified noteworthy differentiations in craniodental morphology based on the principal measurements: P4M3L, ZYW, C1C1W, CPH, cm3L, cp4L, p4m3L, m1m3L, CP4L, PWC1C1 and CPH, which contributed the most to the interspecific craniodental variation in Vietnamese mouse-eared bats. Simultaneously, we revealed two specimen of Myotis aff. siligorensis with distinct craniodental morphology that could be listed in the "Myotis siligorensis" complex. Furthermore, our study established comparisons between morphometrically similar species according to patterns of morphological differences in the study area, which will be helpful for classifying and constructing a comprehensive craniodental morphometric identification key for all species of the genus Myotis in Vietnam and neighbouring southeast Asian regions in further research.
We are grateful to Prof. Vu Dinh Thong, Dr. Ngo Xuan Tuong, Mr. Nguyen Thanh Luong, Mr. Ly Ngoc Tu and Mrs. Vu Thuy Duong for supporting our implementation process and providing specimens. We are thankful to Editor Miguel Camacho Sanchez, Reviewer Roberto Leonan Novaes, Formal Reviewer Mike Skinner and an Anonymous reviewer for their insightful comments during submission. This research was independently supported by VAST to TSN and THB under grant number ĐL0000.04/24-26, and Nagao NEF to HYV and KLV.
Huong Yen Vu – Formal analysis and interpretation; Conceptualisation; Morphological identifications; Visualisation; Dataset curation and analyses; Manuscript writing; Final manuscript approval.
Tuan Hai Bui – Conceptualisation; Software assistant; Dataset analyses; Manuscript revision; Funding acquisition; Final manuscript approval; Supervision.
Truong Son Nguyen – Specimen management; Morphological identifications; Software assistant; Funding acquisition; Final manuscript approval; Supervision.
Trung Thanh Hoang – Software assistant; Supervision.
Kim Luong Vu – Software assistant.
List of species, number of specimens and collected sample localities recorded in this study.
Lateral view (A, a), dorsal view (C, c) and ventral view (D, d) of cranium; lateral view (B, b) and dorsal views (E, e) of mandible; occlusal view of left upper (G, g) and right lower (H, h) toothrows.