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Lack of population genetic structure and host specificity in the bat fly, Cyclopodia horsfieldi, across species of Pteropus bats in Southeast Asia.

Olival KJ, Dick CW, Simmons NB, Morales JC, Melnick DJ, Dittmar K, Perkins SL, Daszak P, Desalle R - Parasit Vectors (2013)

Bottom Line: AMOVA results support a lack of geographic and host-specific population structure, with molecular variance primarily partitioned within populations.We demonstrate the utility of parasite genetics as an additional layer of information to measure host movement and interspecific host contact.Bat flies may play a role as vectors of disease in bats, and their competence as vectors of bacterial and/or viral pathogens is in need of further investigation.

View Article: PubMed Central - HTML - PubMed

Affiliation: EcoHealth Alliance, New York, NY 10001, USA. olival@ecohealthalliance.org

ABSTRACT

Background: Population-level studies of parasites have the potential to elucidate patterns of host movement and cross-species interactions that are not evident from host genealogy alone. Bat flies are obligate and generally host-specific blood-feeding parasites of bats. Old-World flies in the family Nycteribiidae are entirely wingless and depend on their hosts for long-distance dispersal; their population genetics has been unstudied to date.

Methods: We collected a total of 125 bat flies from three Pteropus species (Pteropus vampyrus, P. hypomelanus, and P. lylei) from eight localities in Malaysia, Cambodia, and Vietnam. We identified specimens morphologically and then sequenced three mitochondrial DNA gene fragments (CoI, CoII, cytB; 1744 basepairs total) from a subset of 45 bat flies. We measured genetic diversity, molecular variance, and population genetic subdivision (FST), and used phylogenetic and haplotype network analyses to quantify parasite genetic structure across host species and localities.

Results: All flies were identified as Cyclopodia horsfieldi with the exception of two individuals of Eucampsipoda sundaica. Low levels of population genetic structure were detected between populations of Cyclopodia horsfieldi from across a wide geographic range (~1000 km), and tests for isolation by distance were rejected. AMOVA results support a lack of geographic and host-specific population structure, with molecular variance primarily partitioned within populations. Pairwise FST values from flies collected from island populations of Pteropus hypomelanus in East and West Peninsular Malaysia supported predictions based on previous studies of host genetic structure.

Conclusions: The lack of population genetic structure and morphological variation observed in Cyclopodia horsfieldi is most likely due to frequent contact between flying fox species and subsequent high levels of parasite gene flow. Specifically, we suggest that Pteropus vampyrus may facilitate movement of bat flies between the three Pteropus species in the region. We demonstrate the utility of parasite genetics as an additional layer of information to measure host movement and interspecific host contact. These approaches may have wide implications for understanding zoonotic, epizootic, and enzootic disease dynamics. Bat flies may play a role as vectors of disease in bats, and their competence as vectors of bacterial and/or viral pathogens is in need of further investigation.

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Cyclopodia horsfieldi collected from Pteropus hypomelanus, dorsal view (a) and ventral view (b). Photographs were prepared using a MicropticsTM ML-1000 digital imaging system.
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Figure 2: Cyclopodia horsfieldi collected from Pteropus hypomelanus, dorsal view (a) and ventral view (b). Photographs were prepared using a MicropticsTM ML-1000 digital imaging system.

Mentions: All bat fly specimens examined were all identified morphologically as Cyclopodia horsfieldi (Figure 2) with the exception of two individuals of Eucampsipoda sundaica[59] collected from a Pteropus vampyrus (#0709041) from Kuala Berang, Malaysia (Table 1). Some intraspecific morphological variation was noted, including minor differences in counts of ctenidial spines on male sternite and counts of dorsal abdominal setae on the females, but no systematic character variation related to host species or geography was observed. The sex ratio of C. horsfieldi specimens examined was male-biased, 1.85♂ to 1♀. We observed that most bats were parasitized by at least one fly, and that Pteropus hypomelanus individuals had higher numbers of parasites than P. vampyrus. Several P. vampyrus captured hosted no flies but this was very rarely observed for P. hypomelanus. Many P. hypomelanus examined harbored 4+ flies per individual (Figure 3); and some individuals had 10+ flies. Unfortunately, bats were not exhaustively sampled for flies and the number of fly specimens collected was generally limited to a few flies per bat regardless of parasite load, and quantitative data on intensity of infestation was not collected. The number of bat flies collected from each host was not significantly different (at the p<0.05 level) between P. vampyrus and P. hypomelanus using both a standard t-test (t=−1.85; df=13.8; p-value=0.085) and Mann–Whitney test (W=176.5; p-value=0.066). We also inadvertently collected Neolaelaps spinosa (Acari: Mesostigmata) mites as we removed individual flies with forceps. These mites appear to be phoretic with bat flies [60], a relationship that has been documented with mites and other dipteran species [61-63].


Lack of population genetic structure and host specificity in the bat fly, Cyclopodia horsfieldi, across species of Pteropus bats in Southeast Asia.

Olival KJ, Dick CW, Simmons NB, Morales JC, Melnick DJ, Dittmar K, Perkins SL, Daszak P, Desalle R - Parasit Vectors (2013)

Cyclopodia horsfieldi collected from Pteropus hypomelanus, dorsal view (a) and ventral view (b). Photographs were prepared using a MicropticsTM ML-1000 digital imaging system.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3750525&req=5

Figure 2: Cyclopodia horsfieldi collected from Pteropus hypomelanus, dorsal view (a) and ventral view (b). Photographs were prepared using a MicropticsTM ML-1000 digital imaging system.
Mentions: All bat fly specimens examined were all identified morphologically as Cyclopodia horsfieldi (Figure 2) with the exception of two individuals of Eucampsipoda sundaica[59] collected from a Pteropus vampyrus (#0709041) from Kuala Berang, Malaysia (Table 1). Some intraspecific morphological variation was noted, including minor differences in counts of ctenidial spines on male sternite and counts of dorsal abdominal setae on the females, but no systematic character variation related to host species or geography was observed. The sex ratio of C. horsfieldi specimens examined was male-biased, 1.85♂ to 1♀. We observed that most bats were parasitized by at least one fly, and that Pteropus hypomelanus individuals had higher numbers of parasites than P. vampyrus. Several P. vampyrus captured hosted no flies but this was very rarely observed for P. hypomelanus. Many P. hypomelanus examined harbored 4+ flies per individual (Figure 3); and some individuals had 10+ flies. Unfortunately, bats were not exhaustively sampled for flies and the number of fly specimens collected was generally limited to a few flies per bat regardless of parasite load, and quantitative data on intensity of infestation was not collected. The number of bat flies collected from each host was not significantly different (at the p<0.05 level) between P. vampyrus and P. hypomelanus using both a standard t-test (t=−1.85; df=13.8; p-value=0.085) and Mann–Whitney test (W=176.5; p-value=0.066). We also inadvertently collected Neolaelaps spinosa (Acari: Mesostigmata) mites as we removed individual flies with forceps. These mites appear to be phoretic with bat flies [60], a relationship that has been documented with mites and other dipteran species [61-63].

Bottom Line: AMOVA results support a lack of geographic and host-specific population structure, with molecular variance primarily partitioned within populations.We demonstrate the utility of parasite genetics as an additional layer of information to measure host movement and interspecific host contact.Bat flies may play a role as vectors of disease in bats, and their competence as vectors of bacterial and/or viral pathogens is in need of further investigation.

View Article: PubMed Central - HTML - PubMed

Affiliation: EcoHealth Alliance, New York, NY 10001, USA. olival@ecohealthalliance.org

ABSTRACT

Background: Population-level studies of parasites have the potential to elucidate patterns of host movement and cross-species interactions that are not evident from host genealogy alone. Bat flies are obligate and generally host-specific blood-feeding parasites of bats. Old-World flies in the family Nycteribiidae are entirely wingless and depend on their hosts for long-distance dispersal; their population genetics has been unstudied to date.

Methods: We collected a total of 125 bat flies from three Pteropus species (Pteropus vampyrus, P. hypomelanus, and P. lylei) from eight localities in Malaysia, Cambodia, and Vietnam. We identified specimens morphologically and then sequenced three mitochondrial DNA gene fragments (CoI, CoII, cytB; 1744 basepairs total) from a subset of 45 bat flies. We measured genetic diversity, molecular variance, and population genetic subdivision (FST), and used phylogenetic and haplotype network analyses to quantify parasite genetic structure across host species and localities.

Results: All flies were identified as Cyclopodia horsfieldi with the exception of two individuals of Eucampsipoda sundaica. Low levels of population genetic structure were detected between populations of Cyclopodia horsfieldi from across a wide geographic range (~1000 km), and tests for isolation by distance were rejected. AMOVA results support a lack of geographic and host-specific population structure, with molecular variance primarily partitioned within populations. Pairwise FST values from flies collected from island populations of Pteropus hypomelanus in East and West Peninsular Malaysia supported predictions based on previous studies of host genetic structure.

Conclusions: The lack of population genetic structure and morphological variation observed in Cyclopodia horsfieldi is most likely due to frequent contact between flying fox species and subsequent high levels of parasite gene flow. Specifically, we suggest that Pteropus vampyrus may facilitate movement of bat flies between the three Pteropus species in the region. We demonstrate the utility of parasite genetics as an additional layer of information to measure host movement and interspecific host contact. These approaches may have wide implications for understanding zoonotic, epizootic, and enzootic disease dynamics. Bat flies may play a role as vectors of disease in bats, and their competence as vectors of bacterial and/or viral pathogens is in need of further investigation.

Show MeSH
Related in: MedlinePlus