**5.1 Introduction**

Genetic variation is an important factor in determining the ability of a species to adapt to new environmental conditions and therefore may be an important measure of the evolutionary potential and long-term viability of a species. The information on the amount of genetic variation within a species and its distribution within and between populations would aid in bat conservation planning [96, 97]. To understand both the past and current behavioral processes, it is vital to know the population structure of a species. Colonization and/or dispersal events can be inferred by characterization of population structure at the macro-geographical level, while social organization within a population can be used to infer the microgeographical structure [30]. Both direct (mark-recapture studies) and indirect (genetic) techniques [98] should be used to study the population structure of individuals to understand the degree of spatial variation both in distribution and genetic composition [99].

In general, the high dispersal abilities are associated with a low population structure [100], which has been reported for some mobile species, including birds [101] and bats [102]. Studies describing molecular patterns of intraspecific geographical differentiation in bats have indicated a low level of genetic divergence and a limited geographical structure in species with continental distribution [103]. However, high-intraspecific divergence levels with clearly defined geographical structuring

*Dispersal Patterns, Mating Strategy and Genetic Diversity in the Short Nosed Fruit Bat… DOI: http://dx.doi.org/10.5772/intechopen.100496*

have also been observed. These different results can be attributed to the different molecular markers used in the various studies. Studies on different bat species using the molecular genetics approach have shown genetic diversity among distant populations [102–105].

In *C. sphinx*, the behaviors of tent construction [5], reproduction [11], foraging [106], pollination and seed dispersal [107–110], influence of moonlight [111], sex and reproductive status on the foraging activity [112] are studied in detail. However, the genetic variations within and among populations of *C. sphinx* is not well defined. The lack of genetic information is undoubtedly due, in part, to the difficulties associated with studying them in the wild. The capacity for flight makes bats especially difficult to continuously follow in the wild. In addition, light-tagged animals quickly disappear into dense vegetation making them hard to follow. As a result, data collected by these methods are limited. Direct observation of both sexes are often difficult, therefore genetic analyses may be the only way to obtain reliable data on population structure [31]. An important component required in investigating the population biology of any species is the genetic discrimination of that particular species. This genetic discrimination is the major contributing factor that can help conservation geneticists in evaluating population viability. To provide valuable guidelines for proper conservation and management of *C. sphinx* population, an understanding on genetic diversity is very important.

### **5.2 Materials and methods**

Extensive field trips were carried out to collect *C. sphinx* from different geographical locations in southern Tamil Nadu, India. Bats were captured at the time of emergence from the foliage tents of *P. longifolia* and *B. flabellifer* using a hoop net with an extensible aluminum pole. A small piece of wing membrane from each bat was collected using a sterile biopsy-punch. Tissue samples were obtained from a total of 472 bats from 40 zones. Tissue samples were stored in 70% ethanol at −20°C until DNA extraction [94]. Polymorphism at molecular level was studied by RAPD DNA marker technique. Polymerase chain reaction with 30 arbitrary decamer oligonucleotide primers was applied to the 40 zone samples and to investigate the genetic diversity within and among the populations of *C. sphinx*.

#### **5.3 Results and discussion**

Genetic variation is the raw material of evolution and its magnitude is therefore of vital interest in governing the potential of a species to evolve and adapt [96]. The genetic analysis of RAPD markers showed a reasonably high level of diversity. High level of polymorphism was observed in this study which indicates that the genetic base from different zonal population was diverse and extensive. The percentage of polymorphic bands of RAPD was observed to be higher in this species (73.1%). The amount of dispersal and the formation of new social groups are the two factors that strongly affect the genetic structure of the population [113]. Population genetic data from a taxonomically diverse array of social mammals revealed low to moderately high level of genetic differentiation among social groups. This high level of heterozygosity within social groups may be a common feature of mammalian population. The majority of mammalian species exhibit a social system characterized by polygynous-mating and female philopatry [17].

C*. sphinx* is a polygynous-mating bat and both sexes were found to disperse completely from their natal harems [4]. Moreover, it was observed that the young females either became a member of an already established harem group much earlier when compared to their male counterparts or formed a new harem group of subadult females with an adult male. As a result, the colonies were mainly composed of females which are unrelated or distantly related and with diverse age group [4]. This method of group formation by this species enhances genetic variation. Currently, the high level of genetic diversity can be explained using three factors (i) natal dispersal (ii) formation of new groups and (iii) gene flow between the zones. These are a few such probable reasons for some of the zones to be closely related at the genetic level, although geographically they are from distinct zones of highly distinct locations in Tamil Nadu. This situation can arise in natural populations when there is a possibility of free/random mating and this association between genotypes from contiguous zones may be the result of similar geographical habitat conditions. In addition, recent habitat loss and degradation, which may have led to the concentration of the surviving individuals in the remaining areas, the long generation time and lifespan of the species allowed populations to retain diversity for long periods after habitat loss [17].

Genetic differentiation coefficient of *C. sphinx* from RAPD analysis suggests that the species is of a higher genetic diversity among populations than other bat species [94]. For example, the Brazilian free-tailed bat *Tadarida brasiliensis*, southwestern populations that include those occupying distinct migrational groups show low level of genetic differentiation among populations, even though banding and recapture data suggest low exchange among migratory groups and the inter-colony differences in the bat species are even lower [114]. Similarly, the range of genetic mixing during the seasonal migration of the little red flying-fox *Pteropus scapulatus,* exceeded 3.5 million km<sup>2</sup> [103]. Low degree of differentiation among populations and large amount of gene flow between sub-populations was elaborated using allozymes and RAPD data. A similar result has been reported in gray-headed flying fox *P. poliocephalus* [115].

Genetic studies of migratory bats support high level of gene flow among populations even when separated by large geographical distances (up to 4000 km) [102]. Studying the migratory species using mtDNA markers can further confirm the predicted pattern with little or no genetic structure over broad distance. The individuals of lesser long-nosed bats *Leptonycteris curasoae*, shared identical mtDNA haplotypes when sampled at distances up to 1800 km apart [116]. Similar results have been reported in *P. alecto* [117], *T. brasiliensis* [118], *M. myotis* [119], *Hipposideros speoris* and *Megaderma lyra* [105, 109]. The pattern of population structure and gene flow in species that do not undergo seasonal migration is less clearly known although, in general, gene flow among populations appear more restricted than in migratory species. The gene flow mainly occurs through extracopulation between the colonies without permanent dispersal from the natal colony [105]. But the distance, availability of mating sites or the recently fragmented population might limit the gene flow. Interestingly, no natal dispersal was found to occur in both the sexes, while extra-colony copulation was observed in most animal species [120].

A greater range of genetic differentiation was identified among the migratory species. Also, a significant correlation between geographic and genetic distances is explained in several species. Extraordinarily, in the Australian ghost bat *Macroderma gigas* the degree of structure was found to be high, with significant correlation between geographic and genetic distances studied using both microsatellites and mtDNA markers [121], similar, results have also been reported in *P. auritus* [30], *M. bechsteinii* [33], *Rhinolophus affinis* [122] and the non-migratory island population of *Eidolon helvum* [123], although as the latter two species were located on islands, gene flow may have been also restricted by sea crossing distance. From such studies, it is apparent that whilst individual colonies within a population may show some genetic heterogeneity due to co-ancestry, little genetic subdivision

#### *Dispersal Patterns, Mating Strategy and Genetic Diversity in the Short Nosed Fruit Bat… DOI: http://dx.doi.org/10.5772/intechopen.100496*

is apparent, possibly due to low reproductive skew or high levels of dispersal [124]. Moreover, differences in social structure are frequently associated with different mating and dispersal behaviors, which also influence the amount of gene flow among groups and populations [125]. However, not all sedentary species show evidence of population subdivision, even at considerable geographic scales. In particular, genetically effective gene flow appears to occur among populations of vampire bats *D. rotundus* distributed from Mexico to Costa Rica [126]. As discussed above, the molecular studies at inter-population level has verified a greater diversity of population genetic structure within the order.

Seasonal movement is expected to be the main influence among the populations of migratory species because the genetic structure generally appears to be low. However, a wide range of factors including dispersal ability, extrinsic barriers to gene flow and historical events determines the degree of genetic partitioning among population of sedentary species [102]. Dispersal and migration do not essentially equate with the gene flow and hence it is important to consider this factor while accessing the impact of migratory behavior on the genetic structure of bat population. In migratory species, the level genetic structure can be low only when the individual's mate during their migration. Patterns of genetic population structure for both migratory and non-migratory species may resemble if mating and conception in migratory species occur prior to their migration [102]. Gene flow may also be greater than the dispersal capability of individuals of a species which might indicate, provided the population distribution is continuous. For example, radio tracking of individual brown long-eared bats *P. auritus* showed that maximum foraging distances from the summer roost were no greater than 2.8 and 2.2 km for males and females, respectively. Furthermore, this non-migratory species is not thought likely to travel much further at other times of the year [30]. A hierarchical analysis of genetic population structure in *P*. *auritus* across North-east Scotland identified no genetic differentiation among three adjacent regions when data from colonies within each region were combined. This suggests that colonies across the three regions of North-east Scotland form a continuously distributed population, within which genes move *via* a `stepping stone' model [30].

In our study, the maximum similarity was observed as many zones were closer to each other. Therefore, when populations remain closer, the gene flow is expected to be greater. As a result, the nearby populations should remain more similar at neutral loci. This relationship is referred as the method of isolation by distance and serves as the stepping stone model of gene flow [127]. However, the distance between populations and the nature of the surrounding landscape between population are the two factors on which the level of gene flow depends [128]. These findings support that *C. sphinx* is not known to undergo seasonal migrations. Moreover, it is a common plant-visiting bat that occurs throughout India and much of mainland Southeast Asia [1]. Our results showing the high genetic variations in *C. sphinx* population is not surprising because, the distribution of these bats is continuous and the level of gene flow is also high. Similarly, study has been carried out among *C. sphinx* of the Indian subcontinent which suggests high gene flow and equilibrium population dynamics [129]. Thus, for the long-term persistence of *C. sphinx* populations, maintaining the gene flow is considered as a key factor.

#### **5.4 Conclusion**

Our study deals with the genetic diversity in natural population of *C. sphinx* at the molecular level. We concluded that *C. sphinx* population maintains high levels of genetic variability despite of increase in fragmentation of their habitat. Though this may be beneficial factor for the conservation of these bat species, some caution should be observed. The results suggest that bats move rather freely between zones and current bat populations may continue to decrease in many of the habitats investigated. Furthermore, *C. sphinx* is still a relatively widespread species; it has suffered dramatic population declines during the past several years. Using coalescent based Bayesian analysis, a significant demographic contraction was found to be evident among a large sample of *C. sphinx* genotypes [129], which were one of the eight localities included in the Indian latitudinal study [130]. These results suggest that Indian *C. sphinx* is strongly associated with open habitat [90]. In addition, our direct observation and mark recapture data show a gradual decline of natural populations of *C. sphinx.* However, this study provides baseline genetic information for future studies. To look at the long-term effects of human induced habitat fragmentation and degradation on genetic diversity and structure, microsatellite and mitochondrial DNA variation should be reassessed among this species. It can be concluded that RAPD analysis revealed high levels of genetic polymorphism and differentiation might play a role in the dynamic evolution of *C. sphinx* in southern India. These results would help in developing an effective and meaningful method in conservation of this species. Future studies of Old-World fruit bats from these areas will be of great bio-geographic and evolutionary interest.
