The Enigmatic Blue Ghost Firefly Phausis reticulata (Coleoptera: Lampyridae): Observations on its Courtship, Mating and Oviposition Behaviors

Transcription

1 The Enigmatic Blue Ghost Firefly Phausis reticulata (Coleoptera: Lampyridae): Observations on its Courtship, Mating and Oviposition Behaviors Raphael De Cock 1, Lynn Faust 2 and Sara Lewis 3 1 Evolutionary Ecology Group, University of Antwerp, Antwerp, Belgium Couch Mill Road, Knoxville, Tennessee, USA 3 Department of Biology, Tufts University, Medford, Massachusetts, USA

2 De Cock R., Faust L. & Lewis S Courtship and mating in Phausis reticulata (Coleoptera: Lampyridae): male flight behaviors, female glow displays, and male attraction to light traps. Florida Entomologist 97(4) in press. Photo: Hugh Faust

3 Introduction Distribution: especially in forested regions of southern Appalachian Mountains, small populations as far west as Texas and Oklahoma

4 Introduction Distribution: especially in forested regions of southern Appalachian Mountains, small populations as far west as Texas and Oklahoma OKLAHOMA TEXAS

5 Introduction Distribution: especially in forested regions of southern Appalachian Mountains, small populations as far west as Texas and Oklahoma Habitat: generally in moist forested habitats with small streams or wetlands nearby, and soils overlain by a thick layer of leaf litter

6 Introduction Distribution: especially in forested regions of southern Appalachian Mountains, small populations as far west as Texas and Oklahoma Habitat: generally in moist forested habitats with small streams or wetlands nearby, and soils overlain by a thick layer of leaf litter Phenology - Peak mating season: early season (Apr-May ) late season (Jun-Jul)

7 Introduction Behavior: males of Phausis reticulata (Say) glow as they fly slowly over the forest floor Photo: Hugh Faust

8 Introduction Large numbers of these low-flying males create remarkable and eerie display: this gave them their often heard local nickname: Blue Ghost Firefly Photo: Blue Ghost Fireflies, by Spencer Black, North Carolina- NatGeo

9 Introduction Recently, displays have become increasingly popular as ecotourist attractions Photo: Blue Ghost Fireflies, by Spencer Black, North Carolina- NatGeo

10 Male Phausis reticulata Introduction

11 Male Phausis reticulata Introduction

12 Male Phausis reticulata Introduction

13 Introduction Males of Phausis reticulata Say glow as they fly slowly over the forest floor searching for flightless females that are likewise bioluminescent

14 Introduction strong sexual dimorphism: : normal wings, fly : neotenic, lack both elytra and wings

15 Introduction strong sexual dimorphism: : normal wings, fly : neotenic, lack both elytra and wings

16 Introduction strong sexual dimorphism: : normal wings, fly : neotenic, lack elytra and wings Because of the female s appearance: Appalachian glowworm

17 Introduction strong sexual dimorphism: : normal wings, fly : neotenic, lack elytra and wings Because of the female s appearance: Appalachian glowworm Females have several spot-like light organs whose glow is visible ventrally and dorsally through the transparent cuticle

18 Introduction Previous work described Morphology (Fender 1966), Geographic distribution (Lloyd 1965, 2004; Frick-Ruppert & Rosen 2008) Seasonal and nightly activity patterns (Frick-Ruppert & Rosen 2008) Preliminary observations on courtship behaviors (Lloyd 1965 ) and mating (Frick-Ruppert & Rosen 2008)

19 Introduction Previous work described Morphology (Fender 1966), Geographic distribution (Lloyd 1965, 2004; Frick-Ruppert & Rosen 2008) Seasonal and nightly activity patterns (Frick-Ruppert & Rosen 2008) Preliminary observations on courtship behaviors (Lloyd 1965 ) and mating (Frick-Ruppert & Rosen 2008) Surprisingly little work has been done on P. reticulata courtship, mating behavior, oviposition patterns.

20 Introduction Previous work described Morphology (Fender 1966), Geographic distribution (Lloyd 1965, 2004; Frick-Ruppert & Rosen 2008) Seasonal and nightly activity patterns (Frick-Ruppert & Rosen 2008) Preliminary observations on courtship behaviors (Lloyd 1965 ) and mating (Frick-Ruppert & Rosen 2008) Surprisingly little work has been done on P. reticulata courtship, mating behavior, oviposition patterns. Some authors suggest that pheromones might play a role (Lloyd 1965, 1997a, 1997b, 2004; Frick-Ruppert & Rosen 2008),

21 Introduction Previous work described Morphology (Fender 1966), Geographic distribution (Lloyd 1965, 2004; Frick-Ruppert & Rosen 2008) Seasonal and nightly activity patterns (Frick-Ruppert & Rosen 2008) Preliminary observations on courtship behaviors (Lloyd 1965 ) and mating (Frick-Ruppert & Rosen 2008) Surprisingly little work has been done on P. reticulata courtship, mating behavior, oviposition patterns. Some authors suggest that pheromones might play a role (Lloyd 1965, 1997a, 1997b, 2004; Frick-Ruppert & Rosen 2008), but no extensive experimental proof

22 Aims

23 Aims Provide additional insight into the reproductive ecology of this enigmatic and rather atypical firefly species:

24 Aims Provide additional insight into the reproductive ecology of this enigmatic and rather atypical firefly species: Study field populations: observations about courtship, copulation, oviposition behavior

25 Aims Provide additional insight into the reproductive ecology of this enigmatic and rather atypical firefly species: Study field populations: observations about courtship, copulation, oviposition behavior controlled field experiments to investigate courtship signals, including the relative importance of possible pheromones and bioluminescent glows

26 Aims Provide additional insight into the reproductive ecology of this enigmatic and rather atypical firefly species: Study field populations: observations about courtship, copulation, oviposition behavior controlled field experiments to investigate courtship signals, including the relative importance of possible pheromones and bioluminescent glows Additionally report: Spectrum of bioluminescence of P. reticulata variation in female light organ patterns detailed descriptions of copulation and oviposition female egg guarding

27 General Material & Methods Fieldwork 4-19 Jun 2011 and Jun 2013 (second mating peak) On several locations within Great Smoky Mountains National Park: West side of Burnt Mountain (730 m), near Park Headquarters (475 m), on the north side of Sugarlands Mountain (845 m), NW flank of Mount LeConte (946 m)

28 Result Average standardized male activity Nightly flight activity of males Time

29 Result Male Search Behaviors Males reactions to many different types of glow sources: Attracted to dimly glowing light sources small dots of phosphorescent paint small Betalights or breaklights Not to stronger light sources (LEDs, 9V lightbulbs, other firefly flashes)

30 Result Male Search Behaviors Males reactions to many different types of glow sources: Attracted to dimly glowing light sources small dots of phosphorescent paint small Betalights or breaklights Not to stronger light sources (LEDs, 9V lightbulbs, other firefly flashes)

31 Result Male Search Behaviors Males reactions to many different types of glow sources: Attracted to dimly glowing light sources small dots of phosphorescent paint small Betalights or breaklights Not to stronger light sources (LEDs, 9V lightbulbs, other firefly flashes)

32 Result Male Search Behaviors Males reactions to many different types of glow sources: Attracted to dimly glowing light sources small dots of phosphorescent paint small Betalights or breaklights Not to stronger light sources (LEDs, 9V lightbulbs, other firefly flashes)

33 Result Male Search Behaviors Males reactions to many different types of glow sources: Attracted to dimly glowing light sources small dots of phosphorescent paint small Betalights or breaklights Not to stronger light sources (LEDs, 9V lightbulbs, other firefly flashes)

34 Result Male Search Behaviors Overflying males often circle back to inspect fainter light sources: flew around sec at ~ 20 cm height moving in small circles or spirals ~10 to 80 cm in diameter often jitterbugging and spotlighting some eventually drop directly onto or within 2 cm of the glowing source

35 Result Male Search Behaviors Observations on male search behavior and glow lures suggest: More likely to inspect and land on lures closely resembling P. reticulata female glow patterns

36 Result Male Search Behaviors Observations on male search behavior and glow lures suggest: More likely to inspect and land on lures closely resembling P. reticulata female glow patterns No detection or no response to female-like glows beyond 1 m distance

37 Result Male Search Behaviors Observations on male search behavior and glow lures suggest: More likely to inspect and land on lures closely resembling P. reticulata female glow patterns No detection or no response to female-like glows beyond 1 m distance Approaches and landings only during peak male activity (21:45-22:00): later males seem to ignore glow lures

38 Female Size

39 Result Female Size Female body size was highly variable, and we found a 3-fold difference in size measured as pronotal area

40 Result Female Display Variation among Phausis reticulata females in the number, size and position of light spots

41 Result Female Display Schematics showing variation and asymmetry in light spot patterns among 14 late season female Phausis reticulata observed in Jun 2011 and 2013 from the GSMNP. Small type females 5-6mm (a- c) bear 3 to 4 light organs; Large type females 8-12mm (d-n) show 6 up to 9 lanterns.

42 Result Female Display & Size Schematics showing variation and asymmetry in light spot patterns among 14 late season female Phausis reticulata observed in Jun 2011 and 2013 from the GSMNP. Small type females 5-6mm (a- c) bear 3 to 4 light organs; Large type females 8-12mm (d-n) show 6 up to 9 lanterns.

43 Result Female Display & Size Schematics showing variation and asymmetry in light spot patterns among 14 late season female Phausis reticulata observed in Jun 2011 and 2013 from the GSMNP. Small type females 5-6mm (a- c) bear 3 to 4 light organs; Large type females 8-12mm (d-n) show 6 up to 9 lanterns.

44 Result Pronotum size (mm 2 ) Female Display & Size Pearson r = 0.78, p = # Glow spots

45 Result Pronotum size (mm 2 ) Female Display & Size Pearson r = 0.78, p = # Glow spots Q: Are P. reticulata males more strongly attracted to females with a greater number of glow spots?

46 Male Attraction and N Glow Spots Q: Are P. reticulata males more strongly attracted to females with a greater number of glow spots?

47 Method Male Attraction and N Glow Spots Field experiments artificial light lures mounted in traps (Jun 2013) Data: number of trapped males as an estimate for the attractiveness of a glow display N = 12? <

48 Result Male Attraction and N Glow Spots < 5 males 20 males (binomial P = 0.002)

49 Result Male Attraction and N Glow Spots? < 5 males 20 males (binomial P = 0.002) However possible violation of assumption of independent trials: glows of trapped males attract additional males into traps?

50 Result Male Attraction and N Glow Spots (binomial P = 0.002) 5 males 20 males However possible violation of assumption of independent trials: glows of trapped males attract additional males into traps?? < Re-analysis with more conservative approach considering only catch success per trap

51 Result Male Attraction and N Glow Spots? < (binomial P = 0.002) 5 males 20 males < 4/12 traps 8/12 traps 33% capture success 66% capture success

52 Result Male Attraction and N Glow Spots? < (binomial P = 0.002) 5 males 20 males (Fisher s Exact P = 0.2)? < 4/12 traps 8/12 traps 33% capture success 66% capture success

53 Conclusion Male Attraction and N Glow Spots Inconclusive though highly suggestive evidence that males prefer displays with more light spots

54 Courtship Signals: Glows and Pheromones Q: What is the relative importance of possible pheromones vs. bioluminescent glows?

55 Method Courtship Signals: Glows and Pheromones Field experiment (Jun 2013) Live field-collected P. reticulata females Compare the number of males attracted to 3 treatments:

56 Method Courtship Signals: Glows and Pheromones 3 treatments: 1. GLOW (n=5) : sealed with an airtight transparent cover

57 Method Courtship Signals: Glows and Pheromones 3 treatments: 1. GLOW (n=5) : sealed with an airtight transparent cover 2. GLOW + PHEROMONE (n=6) : mesh cover allowing female s glow and possible sex pheromones to disperse (closest to natural condition)

58 Method Courtship Signals: Glows and Pheromones 3 treatments: 1. GLOW (n=5) : sealed with an airtight transparent cover 2. GLOW + PHEROMONE (n=6) : mesh cover allowing female s glow and possible sex pheromones to disperse (closest to natural condition)

59 Method Courtship Signals: Glows and Pheromones 3 treatments: 1. GLOW (n=5) : sealed with an airtight transparent cover 2. GLOW + PHEROMONE (n=6) : mesh cover allowing female s glow and possible sex pheromones to disperse (closest to natural condition) 3. PHEROMONE (n=7) : mesh cover allowing any possible sex pheromones + cardboard shield preventing males from seeing female s glow

60 Result Courtship Signals: Glows and Pheromones Comparison females success in attracting males (landed yes/no): PHEROMONE (n=7): 57% GLOW (n=5): 60% GLOW+PHEROMONE (n=6): 100%

61 Result Courtship Signals: Glows and Pheromones Comparison females success in attracting males (landed yes/no): PHEROMONE (n=7): 57% GLOW (n=5): 60% GLOW+PHEROMONE (n=6): 100% Freeman-Halton exact two-tailed p = 0.2

62 Result Courtship Signals: Glows and Pheromones Proportion of overflying males that landed directly on or within 1 m of females (mean + 1 SE)

63 Result Courtship Signals: Glows and Pheromones Two-way ANOVA: NS Proportion of overflying males that landed directly on or within 1 m of females (mean + 1 SE)

64 Bioluminescence Emission Spectrum

65 Result Bioluminescence Emission Spectrum P. reticulata emission spectrum maximum wavelength male = 552 nm; female max. wavelength = 547 nm.

66 Mating

67 Result Mating VIDEO mating behavior

68 Result Mating Mean copulation duration (± SE) : 7.9 ± 1.3 min (n = 5)

69 Result Mating Mean copulation duration (± SE) : 7.9 ± 1.3 min (n = 5) Small females (<6mm, 4 or less glow spots) were ignored even after antennal contact!

70 Result Mating Mean copulation duration (± SE) : 7.9 ± 1.3 min (n = 5) Small females (<6mm, 4 or less glow spots) were ignored even after antennal contact! Females polyandrous: mated females show typical glow display on subsequent nights and remate with new males in captivity

71 Oviposition Behaviors

72 Result Oviposition Behaviors After ovipositing, females (n = 4) curl their bodies tightly around their eggs, using one or more legs to grasp them.

73 Conclusions

74 Conclusions New insights into the courtship signals and mating behavior

75 Conclusions New insights into the courtship signals and mating behavior Phausis reticulata obstacle-filled habitats with dense understory: may favor evolution of mixed signaling systems that use a combination of pheromones (long-range attraction) and bioluminescence (short-range localization)

76 Conclusions New insights into the courtship signals and mating behavior Phausis reticulata obstacle-filled habitats with dense understory: may favor evolution of mixed signaling systems that use a combination of pheromones (long-range attraction) and bioluminescence (short-range localization) Our experiments provide additional suggestive, though inconclusive, evidence that female-produced pheromones may play a role in P. reticulata courtship

77 Conclusions Signaling system much more complex than previously thought: Begin flight activity: primarily focus on female light signals?

78 Conclusions Signaling system much more complex than previously thought: Begin flight activity: primarily focus on female light signals? Later perhaps switching to pheromones at lower densities of unmated females (pheromone plumes more distinct OR unmated females might release pheromone only later at night)?

79 Conclusions Novel evidence that P. reticulata males could use female courtship glows as an honest signal of female reproductive potential: Across many insects, female body size is correlated with fecundity

80 Conclusions Novel evidence that P. reticulata males could use female courtship glows as an honest signal of female reproductive potential: Across many insects, female body size is correlated with fecundity Extensive variation in P. reticulata female body size

81 Conclusions Novel evidence that P. reticulata males could use female courtship glows as an honest signal of female reproductive potential: Across many insects, female body size is correlated with fecundity Extensive variation in P. reticulata female body size Size positively correlated with number light spots in female glow display

82 Conclusions Novel evidence that P. reticulata males could use female courtship glows as an honest signal of female reproductive potential: Across many insects, female body size is correlated with fecundity Extensive variation in P. reticulata female body size Size positively correlated with number light spots in female glow display Suggestive evidence from glow lure experiments that males prefer displays with more light spots

83 Conclusions Novel evidence that P. reticulata males could use female courtship glows as an honest signal of female reproductive potential: Across many insects, female body size is correlated with fecundity Extensive variation in P. reticulata female body size Size positively correlated with number light spots in female glow display Suggestive evidence from glow lure experiments that males prefer displays with more light spots overall brightness or glow spot pattern that plays a role?

84 New research questions Need for more detailed research on complex mixed signaling strategies in this and other glow-worm fireflies

85 New research questions Need for more detailed research on complex mixed signaling strategies in this and other glow-worm fireflies Characterize pheromones + examine possible effects of female age, mating status, environmental conditions

86 New research questions Need for more detailed research on complex mixed signaling strategies in this and other glow-worm fireflies Characterize pheromones + examine possible effects of female age, mating status, environmental conditions Single species or a complex of several species or subspecies? 2 seasonal peaks + occurrence of ignored small 4-spotted vs. larger females with >6 glow spots

87 New research questions Need for more detailed research on complex mixed signaling strategies in this and other glow-worm fireflies Characterize pheromones + examine possible effects of female age, mating status, environmental conditions Single species or a complex of several species or subspecies? 2 seasonal peaks + occurrence of ignored small 4-spotted vs. larger females with >6 glow spots Function of male glow?

88 New research questions Need for more detailed research on complex mixed signaling strategies in this and other glow-worm fireflies Characterize pheromones + examine possible effects of female age, mating status, environmental conditions Single species or a complex of several species or subspecies? 2 seasonal peaks + occurrence of ignored small 4-spotted vs. larger females with >6 glow spots Function of male glow? - Hypothesis: male glow triggers female glow = not supported

89 Thanks for listening any questions?

90 Acknowledgments We thank the organisors of the 2014 International Firefly Symposium to offer this chance to share our results. Becky Nichols and Adriean Mayor of the GSMNP for guidance, help and assistance. Raphael De Cock was funded in 2011 by a research grant from the Research Foundation Flanders (F.W.O. file K N) and thanks Erik Matthysen for support and advice. We thank Patti Edwards, Kathrin Stanger-Hall and Sarah Sander for their enthusiastic company, assistance and support during 2011 field trips, Henri Tellegen of OceanOptics Inc. for advice on spectrophotometry, Tristan Mooij (Betalight b.v., The Netherlands) for providing information and solutions with Betalights. Special thanks to Zach Kobrinsky and David Liittschwager, on assignment for National Geographic Magazine for housing and help in This study was performed with the necessary permits (Permit numbers: GRSM sci-0017, GRSM-2013-sci-0096).