(Nesokia indica) (Rodentia: Muridae)

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Geometric morphometric analyses of the short-tailed Bandicoot Rat (Nesokia indica) (Rodentia: Muridae) in the north and southeast of Iran a

a

Bentolhoda Zarei , Mansour Aliabadian , Jamshid Drvish a

Moghadam & Saeed Mohammadi

a b

, Faezeh Yazdani

c

a

Faculty of Science, Department of Biology , Ferdowsi University of Mashhad , Mashhad , Iran b

Faculty of Science, Rodentology Research Department , Ferdowsi University of Mashhad , Mashhad , Iran c

Faculty of Natural Resources, Department of Environmental Sciences , University of Zabol , Zabol , Iran Published online: 16 Sep 2013.

To cite this article: Bentolhoda Zarei , Mansour Aliabadian , Jamshid Drvish , Faezeh Yazdani Moghadam & Saeed Mohammadi , Zoology and Ecology (2013): Geometric morphometric analyses of the short-tailed Bandicoot Rat (Nesokia indica) (Rodentia: Muridae) in the north and southeast of Iran, Zoology and Ecology To link to this article: http://dx.doi.org/10.1080/21658005.2013.834657

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Zoology and Ecology, 2013 http://dx.doi.org/10.1080/21658005.2013.834657

Geometric morphometric analyses of the short-tailed Bandicoot Rat (Nesokia indica) (Rodentia: Muridae) in the north and southeast of Iran Bentolhoda Zareia*, Mansour Aliabadiana, Jamshid Drvisha,b, Faezeh Yazdani Moghadama and Saeed Mohammadic a

Faculty of Science, Department of Biology, Ferdowsi University of Mashhad, Mashhad, Iran; bFaculty of Science, Rodentology Research Department, Ferdowsi University of Mashhad, Mashhad, Iran; cFaculty of Natural Resources, Department of Environmental Sciences, University of Zabol, Zabol, Iran

Downloaded by [University of Aberdeen] at 08:50 16 September 2013

(Received 18 March 2013; accepted 9 July 2013) The short-tailed Bandicoot Rat, Nesokia indica (Gray, 1830) is a widespread species in the Iranian plateau, except Azerbaijan and Kurdistan provinces. The subspecific status of this species in Iran is controversial. Five subspecies (N. i. indica, N. i. huttoni, N. i. buxtoni, N. i. insularis and N. i. legendrei) are defined based on external morphological characters. Morphological differences among seven populations of N. indica from Mashhad, Tabas, Ferdows, Torbatjam, Bojnord, Bampor, and Gorgan were evaluated using multivariate, landmark-based geometric morphometrics for the right mandible and the elliptic Fourier method for the first lower molar. The results showed a highly significant shape variation between short-tailed Bandicoot Rats from the south and northeast of Iran. Based on these analyses, two subspecies were identified: N. i. indica from the southeast and N. i. huttoni from the northeast of Iran.

Nesokija Nesokia indica (Gray, 1830) yra plačiai paplitusi visoje Irano plynaukštėje, išskyrus Azerbaidžaną ir Kurdistaną. Žinios apie nesokijos porūšių statusą Irane yra prieštaringos. Pagal išorinius morfologinius požymius išskirti penki porūšiai: N. i. indica, N. i. huttoni, N. i. buxtoni, N. i. insularis and N. i. legendrei. Atlikus daugiamatę statistinę analizę buvo įvertinti septynių nesokijos populiacijų iš Mashhad, Tabas, Ferdows, Torbatjam, Bojnord, Bampor ir Gorgan vietovių morfologiniai skirtumai. Apatinis (dešinysis) žandikaulis analizuotas taikant geometrinės morfometrijos metodą, pirmojo apatinio krūminio danties forma analizuota taikant elipsinį Furje metodą. Paaiškėjo, kad pietų ir šiaurės rytų Irano nesokijų populiacijos ženkliai skiriasi žandikaulio forma. Šiuo pagrindu buvo apibūdinti du nesokijų porūšiai: N. i. indica pietryčių Irane ir N. i. huttoni šiaurės rytų Irane. Keywords: Nesokia indica; geometric morphometrics; subspecies; Iran

Introduction The short-tailed Bandicoot Rat, Nesokia indica (Gray 1830) is among the most widespread muridae rodents in the Palearctic region. The Bandicoot Rat is a polytypic species and the taxonomic status of the species is highly debated. The identification of the subspecies may rely on the typological concept, which has been used since the beginning of systematics. Therefore, analyses of size and shape employing conventional methods or geometric morphometrics have suggested a subspecific separation. Ziaei (1996) recorded this species in most parts of Iran except Azerbaijan and Kurdistan provinces, and Lay (1967) reported their existence throughout the plains of Iran. This species lives predominantly underground and is a strong burrowing animal. It often lives in large colonies and inhabits banks of streams and irrigation channels, cultivated fields, and neighborhoods of humancreated gardens, parks, and buildings (Gaisler 1975). According to Walker (1975), it usually inhabits areas along irrigation ditches at elevations ranging from 26 m below the sea level to about 1500 m above it. Five subspecies have already been reported for the Bandicoot Rat in Iran. As a widespread species, *Corresponding author. Email: [email protected] Ó 2013 Nature Research Centre

N. i. indica (Gray and Hardwick 1832) has been recorded in the area extending from the north of India to the vicinity of the Caspian Sea and Bandar Gaz. N. i. huttoni (Blyth, 1846) is reported from the north-east of Iran. N. i. buxtoni (Thomas 1919) is recorded in the south and the southwest of Iran. N. i. insularis occurs in Miankaleh, which is south of the Caspian Sea and, finally, N. i. legendrei (Goodwin 1931) is reported to occur in Goladagh of Bojnord (Ellerman 1961). In biosystematics, the presence of two subspecies in the same geographic region is not viewed as possible, but some subspecies of N. indica have been reported to be found in the same locality in Iran. Some of them are represented only by one sample or small numbers, but the most important thing is that the typological concept of the subspecies is not linked to the geographic concept. Therefore, in this study, we made use of both multivariate and geometric morphometric attributes to re-examine the taxonomic status of N. indica from the north and southeast of Iran. The goal of this study was also to investigate shape and size differences of the mandible and the first lower molar in the Bandicoot Rat from the Iranian plateau.

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Table 1. Investigated Iranian populations of N. indica. Locality

Number of specimens

Coordinates

Mashhad

23

36°17′24.25″N 59°35′48.66″E 36°50′11.66″N 54°25′57.46″E 35°33′39.95″N 56°55′5.40″E 34°1′21.97″N 58°10′19.95″E 35°13′54.05″N 60°38′28.40″E 37°28′15.32″N 57°18′56.71″E 29°30′2.01″N 60°52′22.94″E

Gorgan

9

Tabas

7


Ferdows

16

Torbatjam

4

Bojnord

6

Bampor

4

(M1), length of the upper and lower right molar 2 (M2), width of the upper and lower right molar 2 (M2), length of the upper and lower right molar 3 (M3), and width of the upper and lower right molar 3 (M3). Skull and dental measurements were recorded using pointer calipers with accuracy of 0.05 mm and a Nikon measuring microscope MM-40 mm to the nearest 0.001 mm, respectively. The data were transformed for normalization. The one-way analysis of variance (ANOVA) was carried out to check significant differences between groups and sexual dimorphism was also established. The univariate and multivariate statistical analysis, Canonical Variate Analysis (CVA), clustering of morphometric centroids of samples extracted using Canonical Discriminate Analysis (CDA), and Unweighed Pair Group Method Analysis (UPGMA) were performed to evaluate the subspecific status of this species in the Iranian plateau. Geometric morphometric analysis Landmark method Geometric morphometric analysis was performed for 50 specimens of N. indica that belong to seven populations in Iran. Mandible images were taken using a canon camera connected to a personal computer, and coordinates of each landmark were calculated using the TPSdig program (Rohlf 2003). Eight distinctive features were determined on the lateral part of the right mandible. The landmarks (Figure 2) were defined according Duarte et al. (2000). To compare the overall mandible size among populations, the centroid size – the square root of the sum of square distances between each landmark and the centroid (Bookstein 1991) was calculated for each

Figure 1. Sampling localities of N. indica in Iran (see Table 1 for more details).

Materials and methods Morphometric analysis Around 59 specimens of N. indica from seven populations were studied (Table 1 and Figure 1). The specimens were collected using various live traps in different localities. All specimens are deposited in the collection of rodents of the Zoological Museum, Ferdowsi University of Mashhad, Iran. Twenty-three morphometric characters were studied and the following measurements were carried out: occipitonasal length, condylobasal length, zygomatic width, inferaorbital width, braincase breadth across bullae, nasal length, diastema length, anterior palatine foramen length, tympanic bullae length, tympanic bullae width, upper cheek teeth length, lower cheek teeth length, skull height, rostrum width, mandible length, nasal height, palatal length, length of the upper and lower right molar 1 (M1), width of the upper and lower right molar 1

Figure 2. Positions of eight morphological landmarks from the lateral view of Nesokia mandible: 1 – the junction of the upper incisor teeth with the molar alveolus; 2 – the most ventral points of the molar alveolus; 3 – the anterior edge of the tooth row; 4 – the posterior edge of the tooth row; 5 – the most ventral points on the curve of the coronoid process; 6 – the tip of the angular process; 7 – the most dorsal point on the ventral border of the horizontal ramus; and 8 – the most ventral points of the incisor alveolus. Terminology after Atchley and Hall (1991) and Duarte et al. (2000).


Zoology and Ecology individual and tested by the ANOVA (Sokal and Rohlf 1995). An error bar of the centroid size was also plotted. Coordinates of the landmarks were superimposed using the procrustes-generalized least-squares algorithm method, which fits one configuration over another by minimizing the sum of squared distances between homologous landmarks (Gower 1975; Rohlf 1990, 1993; Rohlf and Slice 1990; Bookstein 1991). The consensus configuration of landmarks was computed according to this method as the average shape of all specimens (Rohlf, Loy, and Corti 1996). Shape variables were used as an input for a CVA to evaluate intraspecific differences among populations. Deformation grids of the shape changes, associated with the canonical variate axes, were calculated through multivariate of the canonical scores on the thin plate spline parameters (Rohlf, Loy, and Corti 1996). The UPGMA Cluster analysis was performed to investigate morphometric similarities among populations. Procrustean superimposition and centroid size were calculated using the TpsRelw software (Rohlf 2005). All analyses were performed with SPSS version 15 and PAST version 1.98 (Hammer and Harper 2010). Elliptic Fourier method The outline-based geometric morphometric analysis of the first lower molar was performed (Marcolini 2006). Digital images were captured using a JVC closed circuit camera, an Olympus microscope (BH2) at magnification 2.5. The Cartesian coordinates of the lower molar were calculated using the TPSdig 1.37 (Rohlf 2003) software. In order to change the format of data from TPS to Elliptic Fourier Analysis (EFA), the output data of the TPSdig software were transferred to the Geometric Morphometric Tools Package (GMTP) Program (Taravati 2009). The EFA described by Kuhl and Giardina (1982) and the corresponding to the Elliptic Fourier Transform were

Figure 3. CVA of all N. indica samples from the north and southeast of Iran. Solid square: Bojnord, open square: Tabas, multiplication sign: Ferdows, plus sign: Bampor, open circles: Gorgan, open triangles: Mashhad, and open rectangular: Torbatjam.

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performed using EFAwin (Ferson, Rohlf, and Koehn 1985). Then, the GMTP software was used to convert data to an identifiable format for the PAST software. After that, the multivariate analysis of the data was performed using PAST version 1.98 (Hammer and Harper 2010). Results Morphometric analysis As the results did not show significant sexual dimorphism (F = 0.2; p = 0.6), all the data were analyzed

Figure 4. Clustering of morphometric centroids of all samples extracted from CDA.

Figure 5. Error bar diagram of the mandible centroid size in seven studied populations of Nesokia. The square is the mean; bars represent the confidence interval for the mean at the 95% level (see Table 1).


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Figure 6. Ordination of seven populations of N. indica in the space of canonical axes 1 and 2. Deformation grids on the extremities of each axis are shown. Open rhombus: Ferdows, open rectangular: Bampor, open circles: Tabas, multiplication sign: Gorgan, solid square: Mashhad, plus sign: Bojnord, and open triangles: Torbatjam.

together in subsequent analyses. The ANOVA was also carried out to extract meaningful data, which showed that 12 variables are statistically significant (p < 0.05). The CVA discriminated the south-eastern population (Bampor) from others on the first axis (Figure 3). In CVA the first two canonical variate axes explained 70.93 and 11.28% of variation respectively. The clustering tree based on centroid confirms that the south-eastern population (Bampor) occurs in a very distinct cluster from others (Figure 4). Geometric morphometric analyses The univariate ANOVA of the centroid size was significant among populations (p < 0.001). The error bar graph of the centroid size in different populations is given in Figure 5. The Tabas population showed the largest size of the mandible, while the Bampor population the smallest. The multivariate ANOVA of the total shape space revealed significant differences among populations (p < 0.003). The first two axes of CVA explained 49.5 and 32.08% of the variance, respectively (Figure 6). The CVA discriminated the south-eastern population (Bampor) from other populations on the second axis. Shape changes associated with CV1 and CV2 are shown as deformation grids in Figure 6. The major shape deformation associated with the second axis is localized in the molar alveolus and the incisor alveolus region. The south-eastern population (Bampor) with a positive score on CV2 has a long Molar alveolus and an incisor alveolus region, whereas the other populations show the opposite trend. The multivariate regression of the relative warps against the centroid size showed no significant correlation (p > 0.25; Wilk’s A). This suggested that the differences in the mandible shape are not due to allometry.

The CVA scatter plot of Elliptic Fourier coefficients indicated a slight distinction among the south-eastern population and other populations on the first (cv1) axis (Figure 7). The first two CV axes (cv1 and cv2) explain 89.94% (77.16 and 12.78%, respectively) of the variance among populations (Figure 7). Shape differences are represented in Figure 7. The south-eastern population (Bampor) on the first axis has a wider entoconid cusp, whereas Bojnord, Ferdows, Torbatjam, and Mashhad populations show the opposite trend. In conclusion, based on our geometric morphometric study, the following key identifications can be provided. N. i. indica: The fur of this subspecies is woodbrown dorsally and bright-brown ventrally. The skull is

Figure 7. Canonical Variates analysis of seven N. indica populations based on the first and the second axis. Solid square: Bojnord, horizontal open rectangular: Tabas, multiplication sign: Ferdows, plus sign: Bampor, open circles: Gorgan, open triangles: Mashhad, and vertical open rectangular: Torbatjam.

Zoology and Ecology larger and heavier than that of N. i. huttoni. The nasal bone is short, width in the anterior part being highly limber on top. Sometimes it becomes thin and round at the back end. The partial bone is almost large and the tympanic bulla is like in N. i. huttoni. It has a larger body and a stronger skull. In general, the ventral-most point on the curve of the coronoid process is longer. The length of the lower cheek teeth and the size of the mandible is smaller than in N. i. huttoni. N. i. huttoni: The fur color of this subspecies is darker on the back. It has a shorter ventral-most point on the curve of the coronoid process, a longer anterior edge of the tooth row and a narrow mandible.


Discussion Our study discriminates the south-eastern population (Bampor) from other populations of N. indica in Iran based on morphometric analysis, employing the first lower molar Elliptic Fourier method, especially mandible morphometrics. Our analysis of the centroid size showed that the south-eastern population (Bampor) has significantly smaller mandibles than others. Perhaps, the population of N. indica in the eastern part of Iran has two different origins. The studied populations were divided into two groups. Populations of short-tailed Bandicoot Rats from Sistan and Baluchestan province are probably different at the taxonomical subspecies level. The separation of these two different groups may be related to the presence of two subspecies in the east. Populations of N. indica in the northeast of Iran belong to the N. i. huttoni subspecies, though until now, subspecies from the southeast of Iran have not been reported. But morphometric studies (average head and body length = 206 mm; average zygomatic breadth = 24.93 mm; average tail length = 96.75 mm; and average hind foot length = 34 mm) of the population in the southeast of Iran (Bampor) are congruent with morphometric measurements (head and body length = 210 mm; zygomatic breadth = 30 mm; tail length = 110 mm; and hind foot length = 34 mm) reported by Wroughton (1908). Therefore, morphometrically, the south-eastern population (Bampor) of the short-tailed Bandicoot Rat is similar to the N. i. indica subspecies, and it can be grouped as N. i. indica. However, Darvish (2001) showed that this species from the territory extending from Khorasan to the south of Sistan and Baluchestan and Kerman provinces has morphological, cranial, and dental character variations. Darvish’s studies also demonstrated that populations of the short-tailed Bandicoot Rat from Sistan and Baluchestan tend to have a larger body, a stronger skull, and a greater length of the low molar row than that of N. indica in the north of Khorasan. All in all, the results revealed the importance of morphometric characters and geometric morphometric analysis for the determination of variations among the seven populations of N. indica studied in Iran. Mayer (1963) defined a subspecies as an aggregate of local populations of a species inhabiting a geographic

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subdivision of the species range. Subdivisions differ taxonomically from other populations of the species. The subspecies is not supposed to be an evolutionary unit, but only a taxonomic unit (or more units) distinguishable phylogenetically, still being reproductively compatible with other groups (Avise and Ball 1990). Based on logical biosystematics, the presence of two subspecies in the same geographic region is not possible (Mayer 1963). Local populations are nature’s real building blocks. When local populations do not differ consistently from other populations, the entire series form a single subspecies or a species. At the species or subspecies level, complex characters commonly vary in terms of measurements, in color details or more rarely in facial patterns, etc. In most widespread species, one or more of these complexes vary geographically, forming more or less well-defined subspecies. There are also areas where variations are more evident. Such variable populations should not be arbitrarily squeezed into one or another truly distinct subspecies (Phillips 1982). The basis for the description of a subspecies is character differences observable in representatives (usually specimens) of that population. Thus, adequate materials for forming a good series of specimens are mandatory (O’Neill 1982). There are five subspecies of N. indica in Iran (N. i. indica, N. i. huttoni, N. i. buxtoni, N. i. insularis, and N. i. legendrei (Ellerman 1961). Lay (1967) reported that N. indica of Iran belongs to the N. i. indica subspecies and the other subspecies are synonymous with it. Afshari et al. (1993) investigated morphological differences and the skull of N. indica to determine subspecies and their distribution ranges. The subspecies of N. i. buxtoni were identified from Khuzestan and Kerman, N. i. insularis from Gorgan, and N. i. bailwardi from Tehran and Arak provinces. In order to resolve the taxonomic status of eastern populations, this study provides some useful insights into morphometric and geometric morphometric relationships. However, further investigations involving molecular and cytogenetic (C and Gbanding) studies should be undertaken to shed more light on the taxonomic status of this species in the Iranian plateau. Moreover, the resolution of the evolutionary differentiation level among the south-eastern population (Bampor) and other populations of N. indica will require further geographical sampling.

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