تاکسونومی و بیوسیستماتیک (Sep 2022)
Investigating the Morphometric Variation in the Populations of Megachernes Pavlovskyi Redikorzev, 1949 (Pseudoscorpiones: Chernetidae) in Zagros Mountain Caves, Iran
Abstract
In the present study, morphometric characteristics among four populations of Megachernes pavlovskyi found in caves located in the Zagros Mountains were studied. The length/width proportions of 14 meristic traits of 95 specimens were considered. Data analyses were performed by statistical analysis tools (e.g. ANOVA, MANOVA, PCA, DFA, and cluster analysis). The results of ANOVA showed that there was a significant difference between 12 characters (p<0.05). Principal Component Analysis revealed three main components, which accounted for 64.98% of the total variance. Due to the differences in environmental factors of the studied caves and the influence of morphological traits on ecological factors, the morphological differences among populations could be due to differences in habitat characteristics of species to live in.Key words: Morphological Flexibility, Scatter Chart, PCA, Cave Habitat, Pseudoscorpiones. IntroductionAnimals with wide distribution ranges usually exhibit broad morphological differences in response to a diversity of biotic and abiotic factors (Ennen et al., 2014). The close relationship between the environment and numerous geographic variables is known (Mayr, 1991). Pseudoscorpiones are small and interesting organisms belonging to the order arachnids, which have a widespread distribution, and live in subterranean environments such as caves, and under tree bark and stones (Murienne et al., 2008). Caves are very sensitive, specialized, and unique ecosystems, with special biological conditions, relatively constant ecological conditions (light, temperature, evaporation, and humidity) during different seasons of the year, lack of light, and high humidity (Medeiros et al., 2009; Romero, 2009). One of the animals living inside the cave is the species of Megachernes pavlovskyi, which belongs to pseudoscorpions, and has been reported from some caves in Iran (Darvishnia, 2018). The aim of the present study was to investigate the morphometric changes of M. pavlovskyi populations in some caves of the Zagros Mountain in western Iran. Materials and MethodsPseudoscorpions were sampled individually using forceps from Malek, Palangan, Botkhaneh, and Sarab caves, and stored in 75% ethanol. In order to prepare microscopic slides, clarification of specimens was done. Photos of different parts of the body were taken using a Nikon Eclipse 80i microscope with a digital camera, then all measurement was done with the software ImageJ (ver.1.8.0). For this purpose, first, the length and width (L/W ratio) of 14 measurable traits, including trochanter, femur, tibia, and tarsus of legs I and IV; trochanter, femur, patella, and hand of pedipalps; chelicera, and carapace were measured. Morphometric differences among four populations of this species in caves were evaluated by data analysis and statistical analyses of ANOVA, MANOVA, PCA, DFA, and cluster analysis. ResultsOne-way analysis of variance (ANOVA) was performed to test the significance of the difference in relative morphometric traits of four cave-dwelling populations of M. pavlovskyi species. Twelve relative traits from 14 morphometric traits showed significant differences (except the L/W ratio of padipalp femur, and trochanter of leg IV) (p<0.05). Based on the multivariate analysis of the variance test, a significant difference was observed among patterns of population changes (p<0.05). Principal component analysis (PCA) led to the extraction of three statistically significant components. These three components accounted for 64.98% of the variance. The first component includes the relative characteristics of the femur, tibia, and tarsus of leg IV; tibia and tarsus of leg I; femur, and hand of the pedipalp. The second component includes the patella of the pedipalp, and chelicerae. The third component includes the femur of leg I, and the trochanter of legs I and IV. These components, and traits placed in them, had the highest role in the separation of populations of each cave from each other. According to the classification provided by the scatter plot, Botkhane and Sarab populations are well separated from Malek and Palangan populations, but there is an overlap between Botkhane and Sarab populations as well as Malek and Palangan populations. The total analysis of the measured relative morphological traits of the four studied populations using the discriminant function analysis (DFA) showed that 98% of the groups were correctly classified. Based on the cluster analysis of the relative morphological traits, the studied samples were divided into two main clusters. The first cluster includes the populations of Malek and Palangan caves in Ilam and Fars provinces, and the second cluster includes the populations of Botkhaneh and Sarab caves in Lorestan and Chahar Mahal and Bakhtiari provinces. Discussion An ecosystem may have several populations of the same species. There are many ways to compare or identify different populations of the same species, one of which is the investigation of relative morphometric traits. Therefore, by studying morphometric traits and using statistical methods, it is possible to obtain appropriate information about the morphological diversity of populations (Wootton, 1991). Based on the results of ANOVA analysis, there is a significant difference between most of the relative traits. In the PCA, three significant components were extracted, which accounted for 64.98% of the total variance. Based on the presented three components, Botkhaneh and Sarab populations were well separated from Malek and Palangan populations. Wainwright and Shaw (1999) suggested that morphological traits can change flexibly as a response to environmental changes. In this study, the separation of the populations of this species can be due to the similarity of environmental factors including relative humidity and temperature in Sarab and Botkhane caves compared to Malek and Palangan caves.Based on the scatter plot of discriminant analysis, the groups were correctly classified. The populations of Malek and Palangan caves are in one dendrogram cluster, and Botkhaneh and Sarab are in another cluster. The inside environment of Sarab and Botkhaneh caves has higher humidity and lower temperature than Malek and Palangan caves, and the CO2 concentration of Botkhaneh cave is much higher than the other three caves. Although it is difficult to explain the causes of these morphological differences among populations, contrary to the past ideas stating that morphological changes are only affected by genetics, today it has been proved that in addition to genetic factors, environmental factors also affect morphological traits (Akbarzadeh et al., 2009).Considering that morphological traits are also influenced by ecological factors, the difference in the relative sizes of morphological traits may be due to the difference in the type of ecosystem studied and the different responses of species to environmental conditions (Safaei et al., 2014). In this study, the difference in the relative size of the morphological traits among the studied populations can be due to the difference in the characteristics of the habitat in which these populations live, and the population living in each cave can increase its chance of stability with its morphological flexibility. The morphological flexibility of animals is usually a response to environmental conditions that appear in the form of morphological, physiological, and behavioral changes (Mayr, 1991). In the present study, although Sarab and Botkhaneh caves are far from each other in terms of distance and are different in height from the sea level of the entrance of the cave, it seems that due to the similarity of the environmental factors inside the cave such as having higher humidity, factors such as lower temperature and more accumulation of bats guano have provided similar conditions for the life of this species. This factor can influence the similarity of the population of these two caves compared to Malek and Palangan caves. Based on the obtained results, it could be said that environmental factors such as the temperature of the cave environment, humidity level, and the type of substrate can be considered influencing factors on the morphology of Megachernes pavlovskyi species and can explain the observed differences.
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