Research On Adaption Of Skull Morphology And Biteforce In A Bird-eating Bat(Ia Io)

Genetic and ecological factors influence morphology,and morphology is compatible with function.Different diets,feeding behavior patterns and food selection strategy promote the evolution of animal feeding organs to form specific morphologies to satisfy the animal life habits and feeding requirements.There are a wide variety of bat species and diverse food types,the morphology and bite performance of skulls of bats show a number of characteristic feeding adaptations.?The study on the ecological adaptability of skull morphology and bite force is helpful to reveal the evolutionary trends related to bat feeding habits.Currently,the relationships between skull morphology,bite force,and diets have been investigated in a variety of animal groups.However,studies on bats are focused on the Phyllostomidae,and two-dimensional geometric morphology and bite force estimation are mostly used in the studies,but lacking research that combines the three-dimensional(3D)geometric morphology method of the skull and in vivo bite force.Ia io is the only known bird-eating bat in China,eats both insects and passerine birds,how the skull morphology or bite force in I.io are related to the expanded diet(that is,birds)remains unknown.Therefore,we selected I.io and many different feeding bats(sympatric or closely related species)as the research objects,combined mitochondrial genes(Cytb)and nuclear gene(ACOX2,CHD1)construct a phylogenetic tree,used three-dimensional(3D)geometry of the skulls and measurements of bite force to investigate the characteristics and the correlation of skull morphology and bite force to bat diets in a phylogenetic context.The main results are as follows:1.The bite force of bats is affected by body size and skull morphology.After correcting for body size,Ia io have a high bite force comparable to that of the carnivorous bats(all P > 0.05),which is one of the reasons for the expansion of their feeding niche.2.Significant differences in skull morphology(mandibule,cranium)and size(skull size and head dimensions)exists among bat species with different diets(all P < 0.01),the Ia io exhibits similar characteristics to the carnivorous bat(P > 0.05),but significantly differs from that of the piscivorous and insectivorous bats(all P < 0.05).3.Phylogeny significantly affects the skull shape(K > 0.8,P < 0.01)and size(K > 0.6,P < 0.05)of bats,which results in similar skull morphology between the I.io and its related species,but have no effect on the bite force(K= 0.439,P = 0.287).There is no significant correlations were found between diets and the skulls,or between diets and residual bite force after controlling for phylogeny(all P > 0.05).However,the skull morphology of bats is significantly associated with bite force whether or not controlling for phylogeny(Correlation coefficient r-PLS > 0.6,P < 0.05),a large bite force is often accompanied by high mechanical advantage of skull shape and size,such as a strong mandible,a larger cranium,a high sagittal crest and a wide zygomatic arch.4.The bird-eating bats of I.io displayslarger skull size and head dimensions,robust mandibles,shortened dentitions,higher coronoid processes,expanded angular processes,low condyles,and taller cranial sagittal crests,shorter orbital spacing,wider faces and zygomatic arches that provide this species with high mechanical advantages,which are the morphological basis for their high bite force.To sum up,the specific skull morphology and bite force of the bat are mainly influenced by genetic factors,phylogeny affects the bite force by influencing the characteristics of skull morphology of bat,and finally affecting the feeding type and prey range of I.io.The high mechanical advantage of the skull,the larger bite force and the larger body size help the I.io to capture and utilize prey in the process of hunting,so that the larger and hard-bodied birds are used as a dietary component.This study provides an important supplement to the study of the skull and bite force of bird-eating bats,and provides a scientific basis for a deeper understanding of the co-evolution between bats and birds,as well as a theoretical basis for the evolution of animal skull morphology and predatory behavior.