Research On Coexistent Mechanism In 6 Species Of Sympatric Rhinolophids And Mechanism Of Echolocation Call Frequency Deviating From Allometry In 3 Species Of Rhinolophids From Phillippinensis-group

Bats constitute the second largest order of mammals worldwide with high species richness. As an important biological indicator for ecosystem, the bats diversity has declined dramatically due to human disturbance. So, the ecology study for bats is seriously needed. The stable coexistence of sympatric species maintains species diversity. Bats are ideal organisms with which to test hypotheses related to coexistence. Research on the coexistent mechanism in bats communities can provide the significant knowledge for conservation biology. Furthermore, the echolocation calls and morphologies of bats have profound effects on the way they live and they often have an allometry relationship. However, some bats species deviated from this correlation. The physics of echolocation is intimately related to the ecology of insectivorous bats. Deviations from allometric relationships may imply the response of bats to nature selection pressure, providing insight into the evolutionary radiation and the adaptive evolution of bats.From 2004 to 2008, we studied the coexistent mechanism in six sympatric rhinolophids species: Rhinolophus ferrumequinum, R. sinisus, R. affinis, R. macrotis, R. lepidus, R. pusillus in Shuanghe town, Yunnan Province. We also studied the ecological and physical factors which are responsible for deviation of echolocation call frequencies from allometry in rhinolophids from Phillippinensis-group. The details are as follow.1. The skull form of six sympatric rhinolophids species was compared by geometric morphometrics method. Both size and shape of crania and mandible were significant different among these sympatric species. The variances in shape of crania and mandible were related to the size variances of crania and mandible, respectively. The variances in crania may imply the complex adaptation for multiply functions, such as echolocation and food chew, while the variances in mandible may be the result of adaptation for diet.2. The Variance Tests were used to detect community-wide characters displacement in five character parameters collected from 6 sympatric species, including peak frequency, forearm length, wing loading and centroid size of crania and skull, which associated with the resource using. The results showed support for evenly displaced acoustic character, no support on other four parameters. These results showed the importance of sensory echology in maintaining animal coexistence and the mixed support for competition.3. The prey selection experiment was conducted to test the ecological factor leading to deviating peak frequency of echolocation call in Rhinolophus macrotis, one species from Phillippinensis-group. The prey selection strategy of R. macrotis was compared with the R.lepidus. These two sympatric species are morphologically similar but acoustically divergent: R.macrotis has an echolocation frequency significantly lower than that predicted by the allometric relationship, whereas that of R. lepidus agreed with expectations. These results confirmed the existence of finely tuned trophic niche differentiation and suggested that food resource partitioning is one of the factors leading to lower peak frequency of calls in R. macrotis.4. Nasal cavity and outer ear are important part of sound emission and echo reception for rhinolophids, respectively. We compared the nasal chamber size and ear length of 10 species rhinolophids, including three species from Phillippinensis-group, to investigate the physical factor relating the divergent peak frequency of echolocation call in Phillippinensis-group bats. The results showed that the nasal cavity size and ear length were positively related to the forearm length, respectively. We found that both of the nasal chamber size and ear length of three species of rhinolophids from Phillippinensis-group also deviated from the allomety relationship with body size. This result indicated that the distinct developed sound signal system is one of the physical bases for divergent peak frequency of echolocation call from prediction by forearm in Phillippinensis-group bats. The result of partial correlation among three morphology parameters showed that the relationship between sound emission and echo reception were stronger than that with body size, implying the closely adaption between those different functional parts.5. We also studied the relationship between echolocation call frenquency and different morphology parameters. The results of bivariate correlation analysis and linear regression analysis showed that the call peak frequency was negtively related to the forearm length, nasal cavity size and ear length, respectively. The call peak frequencies of three rhinolophid species from Phillippinensis-group were accordance with the prediction basing on nasal cavity size or ear length. The results of Mantel test suggested that the divergence in call frequency were positively with divergences in nasal cavity size or era length but not to that in forearm length. The results of partial correlation analysism, multiply regression analysis and path analysis suggested that the peak frequency was stronger with the morphology of sound manage system than that with body size. Those results also implied that the nasal cativty form may be the most important physical factor influencing the call frequency.