Geographic Variation And Influencing Factors In Cranial Morphology Of Three Rhinolophus Species Based On Geometric Morphometries

Divergence of evolution is a hotspot and a difficulty in evolutionary ecology.Darwin makes the theory in the book of Origin of Species: the evolution of species isinfluenced by the forces of natural selection. The evolution of phenotype plays animportant role in speciation, and is affected by several factors. Developing the studyon geographic variation and influencing factors of phenotypic variation amongdifferent populations is of paramount importance in indicating the process ofspeciation.Our sample consists of three Rhinolophus species: seven populations of greaterhorseshoe bat (Rhinolophus ferrumequinum), five populations of big-eared horseshoebat (Rhinolophus macrotis) and ten populations of least horseshoe bat (Rhinolophuspusillus). We digitized the morphology of skull with the geometric morphometricsapproach, and analyzed the divergence and variation of morphology among thepopulations in three Rhinolophus species with canonical variable analysis (CVA). Wecollected longitude, latitude, and elevation of collection sites and correspondingclimate data. Combining the mitochondrial cytb DNA sequence, we calculated theEuclidean distance matrixs of geographical distance, climate factors and geneticdivergence. To determine the key factor causing the cranial morphology, wetransacted the data by Mantel test and Partial Least Square Analysis with the softwareof Arlequin3.1, tpsPLS and PAST. The main conclusions were as follows:1. The Henan population reveals unique adaption to the environment in R.ferrumequinum. The teeth show the tendency of getting longer from southwestpopulations to northeast populations, indicating the different component of prayamong the populations. Temperature is significantly correlative with morphology ofskull, implying that cranial morphology of R. ferrumequinum is affected byenvironment though it’s not significantly correlative with climate Euclidean distance.2. The rostrum is gradually lengthening among populations in R. macrotis,hinting that the bite force is rising. The position of foramen magnum and the anglebetween rostral and braincase regions have marked geographic divergence. Thedivergence is only correlative with climate data among the three matrixs, and theannual rainfall is the most important factor.3. No distinct division was found between Hainan population and mainland populations. In addition, a notably broadening tendency happened in the structure ofrostrum from southern populations to northern populations, and it is also a reflectionof increasing of bite force. We infer that the proportion of Coleoptera is higher in thepray of southern populations. Climate condition is the main cause of morphologyvariation of cranium in Rhinolophus pusillus.4. Both size and shape reveal evident diversity in three Rhinolophus species.The lateral skull shows higher discrepancy than the ventral skull among populations,and the lateral shape came in for more environmental influence than the ventral. All ofthe three species show variation of bite force, but representing different ways ofadaption to the same function. The cranial morphological shape of the three speciesconform the evolutionary model of geographical isolation, and the natural selection isthe main impelling force of evolution of cranial morphology.