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Seasonality and synchrony of reproduction in three species of nectarivorous Philippines bats.

Heideman PD, Utzurrum RC - BMC Ecol. (2003)

Bottom Line: In one species, R. amplexicaudatus, primigravid females (in their first pregnancy) produced their young in June and July, a birth period significantly different in timing from the two birth periods of older adult females.There were few significant differences in reproductive timing among different years, and those differences were generally less than two weeks, even during a severe drought in the severe el Niño of 1983.The results suggest that these species follow an obligately seasonal pattern of reproductive timing with very little phenotypic plasticity.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biology, College of William and Mary, Williamsburg, VA, 23187-8795, USA. pdheid@wm.edu

ABSTRACT

Background: Differences among species and among years in reproductive seasonality (the tendency for clusters of events to fall at approximately the same point in each year) and synchrony (amount of clustering of events within a year) have been intensively studied in bats, but are difficult to assess. Here, we use randomization methods with circular statistics to test for synchrony and seasonality of reproduction in three species of nectarivorous megachiropteran bats on Negros Island in the central Philippines.

Results: In Rousettus amplexicaudatus, estimated dates of birth were both highly synchronous and highly seasonal. In Macroglossus minimus, estimated births were seasonal and significantly clustered within years, but within each year births occurred over a broad period, indicating a low level of synchrony. In Eonycteris spelaea, estimated births were also seasonal and had statistically significant synchrony, with birth periods within years intermediate in synchrony between R. amplexicaudatus and M. minimus. All three species had a similar seasonal pattern, with two birth periods in each year, centered on March or April and August or September. In one species, R. amplexicaudatus, primigravid females (in their first pregnancy) produced their young in June and July, a birth period significantly different in timing from the two birth periods of older adult females. This more conservative pattern of young females may allow higher survival of parents and offspring at cost of a lost reproductive opportunity. There was weak evidence that in some years primigravid females of M. minimus might differ in timing from older adults. There were few significant differences in reproductive timing among different years, and those differences were generally less than two weeks, even during a severe drought in the severe el Niño of 1983.

Conclusion: The results suggest that these species follow an obligately seasonal pattern of reproductive timing with very little phenotypic plasticity. The resampling methods were sensitive to differences in timing of under two weeks, in some cases, suggesting that these are useful methods for analyses of seasonality in wild populations of bats.

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Reproductive status of Rousettus amplexicaudatus. (a) Sample data showing parous adult females from June 1982 to July 1983 (these months have been rearranged for display to show January to December for consistency with other figures). (b) Primigravid females from June 1982 to July 1983 (these months have been rearranged to display January to December). (c) Estimated timing of births in parous adults collected from 1982 to 1992. (d) Estimated timing of births in primigravid females collected from 1982 to 1992. In (a), open circles indicate individuals lactating, solid circles indicate individuals not lactating, circles enclosing numerals indicate that number of females lactatating, and numerals alone indicate that number of individuals not lactating. In (b), solid triangles indicate individual females, triangles enclosing numerals indicate that number of females. Dashed lines in (c) indicate no data available.
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Figure 1: Reproductive status of Rousettus amplexicaudatus. (a) Sample data showing parous adult females from June 1982 to July 1983 (these months have been rearranged for display to show January to December for consistency with other figures). (b) Primigravid females from June 1982 to July 1983 (these months have been rearranged to display January to December). (c) Estimated timing of births in parous adults collected from 1982 to 1992. (d) Estimated timing of births in primigravid females collected from 1982 to 1992. In (a), open circles indicate individuals lactating, solid circles indicate individuals not lactating, circles enclosing numerals indicate that number of females lactatating, and numerals alone indicate that number of individuals not lactating. In (b), solid triangles indicate individual females, triangles enclosing numerals indicate that number of females. Dashed lines in (c) indicate no data available.

Mentions: Births of multiparous adult female R. amplexicaudatus were significantly clumped in two well-defined clusters per year, one in March/April and the other in August/September (Fig. 1a &1c, Table 2). Most females captured in April and May were lactating as well as pregnant (e.g., Fig. 1a showing 1983), indicating that most and probably nearly all female R. amplexicaudatus have young in both birth periods. In all years for which data were sufficient for analysis, clusters in both periods (Fig. 1c) were highly statistically significant (Table 2). The timing of these clusters differed slightly between some years (6 of 18 pairwise comparisons). Births in the August/September cluster of 1991 were significantly earlier than in 1982, 1983, 1987, and 1992 (p < 0.05 for all) by an average of 1 – 2 weeks.


Seasonality and synchrony of reproduction in three species of nectarivorous Philippines bats.

Heideman PD, Utzurrum RC - BMC Ecol. (2003)

Reproductive status of Rousettus amplexicaudatus. (a) Sample data showing parous adult females from June 1982 to July 1983 (these months have been rearranged for display to show January to December for consistency with other figures). (b) Primigravid females from June 1982 to July 1983 (these months have been rearranged to display January to December). (c) Estimated timing of births in parous adults collected from 1982 to 1992. (d) Estimated timing of births in primigravid females collected from 1982 to 1992. In (a), open circles indicate individuals lactating, solid circles indicate individuals not lactating, circles enclosing numerals indicate that number of females lactatating, and numerals alone indicate that number of individuals not lactating. In (b), solid triangles indicate individual females, triangles enclosing numerals indicate that number of females. Dashed lines in (c) indicate no data available.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC305358&req=5

Figure 1: Reproductive status of Rousettus amplexicaudatus. (a) Sample data showing parous adult females from June 1982 to July 1983 (these months have been rearranged for display to show January to December for consistency with other figures). (b) Primigravid females from June 1982 to July 1983 (these months have been rearranged to display January to December). (c) Estimated timing of births in parous adults collected from 1982 to 1992. (d) Estimated timing of births in primigravid females collected from 1982 to 1992. In (a), open circles indicate individuals lactating, solid circles indicate individuals not lactating, circles enclosing numerals indicate that number of females lactatating, and numerals alone indicate that number of individuals not lactating. In (b), solid triangles indicate individual females, triangles enclosing numerals indicate that number of females. Dashed lines in (c) indicate no data available.
Mentions: Births of multiparous adult female R. amplexicaudatus were significantly clumped in two well-defined clusters per year, one in March/April and the other in August/September (Fig. 1a &1c, Table 2). Most females captured in April and May were lactating as well as pregnant (e.g., Fig. 1a showing 1983), indicating that most and probably nearly all female R. amplexicaudatus have young in both birth periods. In all years for which data were sufficient for analysis, clusters in both periods (Fig. 1c) were highly statistically significant (Table 2). The timing of these clusters differed slightly between some years (6 of 18 pairwise comparisons). Births in the August/September cluster of 1991 were significantly earlier than in 1982, 1983, 1987, and 1992 (p < 0.05 for all) by an average of 1 – 2 weeks.

Bottom Line: In one species, R. amplexicaudatus, primigravid females (in their first pregnancy) produced their young in June and July, a birth period significantly different in timing from the two birth periods of older adult females.There were few significant differences in reproductive timing among different years, and those differences were generally less than two weeks, even during a severe drought in the severe el Niño of 1983.The results suggest that these species follow an obligately seasonal pattern of reproductive timing with very little phenotypic plasticity.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biology, College of William and Mary, Williamsburg, VA, 23187-8795, USA. pdheid@wm.edu

ABSTRACT

Background: Differences among species and among years in reproductive seasonality (the tendency for clusters of events to fall at approximately the same point in each year) and synchrony (amount of clustering of events within a year) have been intensively studied in bats, but are difficult to assess. Here, we use randomization methods with circular statistics to test for synchrony and seasonality of reproduction in three species of nectarivorous megachiropteran bats on Negros Island in the central Philippines.

Results: In Rousettus amplexicaudatus, estimated dates of birth were both highly synchronous and highly seasonal. In Macroglossus minimus, estimated births were seasonal and significantly clustered within years, but within each year births occurred over a broad period, indicating a low level of synchrony. In Eonycteris spelaea, estimated births were also seasonal and had statistically significant synchrony, with birth periods within years intermediate in synchrony between R. amplexicaudatus and M. minimus. All three species had a similar seasonal pattern, with two birth periods in each year, centered on March or April and August or September. In one species, R. amplexicaudatus, primigravid females (in their first pregnancy) produced their young in June and July, a birth period significantly different in timing from the two birth periods of older adult females. This more conservative pattern of young females may allow higher survival of parents and offspring at cost of a lost reproductive opportunity. There was weak evidence that in some years primigravid females of M. minimus might differ in timing from older adults. There were few significant differences in reproductive timing among different years, and those differences were generally less than two weeks, even during a severe drought in the severe el Niño of 1983.

Conclusion: The results suggest that these species follow an obligately seasonal pattern of reproductive timing with very little phenotypic plasticity. The resampling methods were sensitive to differences in timing of under two weeks, in some cases, suggesting that these are useful methods for analyses of seasonality in wild populations of bats.

Show MeSH