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Variation of Insect Abundance
on Bioluminescent Fungi
Jordan Pletzer, Nashelly Meneses, and Neil Cobb
Department of Biological Sciences, Northern Arizona University, Field Experience in Conservation Biology
Introduction!
!Bioluminescence is widespread in nature, from land invertebrates to deep
ocean animals.3 Bioluminescence plays a role in attracting mates, deterring
predators, attracting tertiary predators (burglar effect), and camouflage.4
Although prevalent in the oceans, on land the occurrence of bioluminescence is
scarce. On land, bioluminescence is restricted to insects, such as fireflies and
beetles, worms, hexapods, centipedes and millipedes, and fungi. Little is still
known about fungal bioluminescence including its purpose and the key
components in its chemical reaction.
Hypotheses for the function that
bioluminescence serves to fungi include: to attract spore dispersers, to attract
predatory insects, to deter fungivores, or simply as a result of a chemical
reaction with no biological implications.1, 5, 6 The chemical reaction producing
light in fungi is not energy costly,6 suggesting it might be a by-product with no
ecological
!! ! !! significance. Glowing fungi is still an esoteric topic in the science
community and cultural community as well. !
!Three bioluminescent fungi species are found in native and mixed jungles
across Saipan, Commonwealth of the Northern Mariana Islands. Two have
been morphologically identified as Mycena chlorophos (Figure 2) and
Filoboletus manipularis (Figure 3). Both are white or light tan agarics that grow
in the forest floor leaf litter. The third unidentified bioluminescent species has a
white, flower petal-like fruiting body that develops on the bark of fallen logs,
roots and the bottom of extant trees (Figures 4, 5 and 6). The question I am
exploring is: Why do fungi glow? My hypothesis is that fungi luminate to attract
insects. !
!A total of 1,034 insects divided into 1 class, 7 orders, and 8 families were collected off of 173
fruiting bodies (Table 1). All of the above taxa were present in luminescent fruiting bodies whereas
only 1 class, 2 orders, and 2 families were gathered from all non-luminescent fruiting bodies.
Collembola, Hemiptera and Arachnida were the most abundant insects across all bioluminescent
mushroom species. Collembola included 3 families: Poduridae, Sminthuridae, and Entomobryidue.
Poduridae was, by far, the most abundant family, accounting for 85% of all insects collected across
all species of bioluminescent mushrooms (Figure 7).!
! Overall, insects were more abundant on luminescent fruiting bodies compared to nonluminescent fruiting bodies for all three fungi species combined (Wilcoxon test; N = 173, Z = -3.94,
P < 0.0001, Figure 7, 8). This was also the case for the unidentified fungi species; insects were
significantly more abundant on luminescent fruiting bodies (N = 70, Z = 6.86, P-value < 0.0001,
Figure 9). However, for F. manipularis and M. chlorophos, a Wilcoxon test showed no difference in
insect abundance on luminescent and non-luminescent mushrooms (N = 60, Z = 0.62, P = 0.54
and N = 43, Z = 0.06, P = 0.95; respectively). There were marginally significant differences in
insect diversity and richness between luminescent and non-luminescent fruiting bodies for all fungi
species (Wilcoxon test; Diversity: N = 6, Z = -1.75, P = 0.08; Richness: N=6, Z = -1.77, P = 0.07;
Table 1).!
Insect Abundance on all Fungi
1000
Species
Insect Abundance on Unidentified
800
Species
700
Total Insect Abundance
! Fungi are one of the few organisms on land that are bioluminescent.
The ultimate cause of bioluminescence in fungi is not fully understood.
I
tested the hypothesis that fungi are bioluminescent to attract insects. I
collected insects from glowing and non-glowing fruiting bodies of Mycena
chlorophos, Filoboletus manipularis, and an unidentified species. Insects were
more abundant on all luminescent fruiting bodies of all three bioluminescent
fungi species combined (N = 173, Z = -3.94, P < 0.0001). Although M.
chlorophos and F. manipularis didnʼt show significant differences, insect
abundance on the unidentified species suggests strong support for the
attraction of insects (N = 70, Z = 6.86, P-value < 0.002).
Fungal
bioluminescence may aid in the attraction of insects, but whether or not it
directly serves a greater purpose for fungi is still being questioned. !
Results
Total Insect Abundance
Abstract!
600
500
400
300
200
100
800
600
200
0
Luminescent
Non-luminescent
Fruiting Bodies
Luminescent
Non-luminescent
Fruiting Bodies
N = 70, Z = 6.86, P-value < 0.0001
N = 173, Z = -3.94, P < 0.0001
Figure 9!
Figure 8!
!
!
Figure 4, Unidentified Species!
!
!
Conclusions and Discussion
!The overwhelming abundance of Collembola and Arachnida found during my study was
not surprising as they are frequently found in soil and on a variety of species of fungi, including
non-bioluminescent species.2 Many species in these groups are fungivorous and consume the
fungi fruiting bodies and mycelium.5 The fact that they are found on luminescent and nonluminescent species of fungi illustrates that bioluminescence strictly isnʼt what has attracted
them to the fruiting body. However, insect diversity and richness neared significant results. The
abundance of a large, diverse group of insects demonstrates that bioluminescence in fungi is
indeed attracting more insects on luminescent fruiting bodies than nonluminescent fruiting
bodies.!
! Overall, across all three mushrooms species, insects were more abundant on
luminescent than non-luminescent fruiting bodies. However, when broken up into individual
species, only the unidentified fungus had a higher abundance of insects on luminescent fruiting
bodies. Differences in the life history of these species could explain these results. The
unidentified fungi fruiting bodies grow in clusters (30+ fruiting bodies in one close area) on the
bottom of trees and across logs. Also, the fruiting bodies of this unidentified species are
generally larger in size (average 2-3cm) and haves a longer lifecycle, frequently longer than two
weeks. This longer lifecycle could serve as a dependable, longer-term food source for insects.
M. chlorophos and F. manipularis have smaller fruiting bodies (average 1cm). These
mushrooms are found on the forest floor in leaf litter and are less visible. Furthermore, the
fruiting body caps tend to be covered with a viscous, sticky substance. M. chlorophos and F.
manipularis are more frequently found alone or in small groups (up to 10-12). In addition, their
life cycle is extremely ephemeral, lasting 1-3 nights. These factors alone may explain why
fewer insects were gathered off the fruiting bodies.!
400
0
Figure 3, Filoboletus manipularis!
! Weather could also explain my results. Saipan has particularly steady humidity and
temperature. However, rainfall is extremely sporadic and may contribute to bug abundance
differences throughout my study. An analysis of the effect of rainfall on insect abundance is
currently underway. Although insects are more abundant on luminescent fruiting bodies, this
doesnʼt necessarily explain why fungi glow. Insects could just be attracted strictly to the glow,
without benefiting the fungi at all. If the glow attracts more spore dispersers, then we should
see the fungiʼs fitness increase as a result.!
Figure 6, Unidentified Species!
Figure 2, Mycena chlorophos!
References
!
Methods!
" To test the hypothesis that bioluminescence in fungi serves to attract
insects, I collected insects off luminescent and non-luminescent fruiting bodies of
three different species (Mycena chlorophos, Filoboletus manipularis, and an
unidentified species). Fruiting bodies from the fungi species used in this study
were haphazardly selected in various native and mixed jungle locations across
the island of Saipan, Commonwealth of the Northern Mariana Islands. The
objective was to detect if insects are more attracted to luminescent fruiting bodies
than to non-luminescent fruiting bodies. The insects gathered off these fruiting
bodies were preserved in vials filled with ethanol. Afterward, the insects were
classified to order and/or family using a dissecting microscope and with the
assistance of Dr. Neil Cobb, Colorado Plateau Museum of Arthropod Biodiversity.
Species richness and species diversity were also considered. The formula used
for calculating species diversity was the Shannon Index (
). N is the
total number of taxa, ni is the specific species in context. Ex: i=1 is species 1, i=2
is species 2. Wilcoxon tests were utilized to determine if there was a difference in
insect abundance, richness and diversity between luminescent and nonluminescent fruiting bodies.!
1 Desjardin, Dennis. (2008) Fungi bioluminescence revisited.
Photobiological Sciences. Volume 7, issue 2!
Photochemical and
2 Klironomos, John N., Kendrick, Bryce. (1995) Relationships among microarthropods,
fungi, and the environment. The Significance and Regulation of Soil Biodiversity. Volume
63!
3 McAda, Harleen Workman. (1966). Bioluminescence. The American Biology Teacher.
Vol. 28, No. 7!
Figure 7!
4 McCapra, F. (1982). Review Lecture: The Chemistry of Bioluminescence. Proceedings
of the Royal Society of London. Series B, Biological Sciences, Vol. 215, No. 1200!
!
Shannon Diversity Index Richness Mycena chlorophos Glow Non-­‐glow Filoboletus manipularis Glow Unidenti'ied All Fungi Species Figure 5, Unidentified Species growing on Casuarina!
Non-­‐glow Glow Non-­‐glow Glow Non-­‐glow 1.56 0.06 1.24 0 0.64 0.24 0.90 0.22 5 2 13 1 13 3 17 5 Table 1!
!
5 Sivinski, John. (1981). Arthropods attracted to luminous fungi. Psyche. 88:383-390!
6 Weitz, Hedda J. (2004). Naturally bioluminescent fungi. Mycologist. Volume 18, Part 1!
!
!
Acknowledgments
Russell Benford, Dr. Stephen Shuster, Northern Arizona University, GO Scholarship, Danielle Varnes, Rosie Alling, Monique Brown, Brittani Bulger,
Johnna “Battie” Eilers, Eliza Hottel, Michael “Lionheart” Marshall, Adrianna Nimer, Sarah Raber, Karah Roof, Natalie Senini, Zachary Watson, Tom
Pangelinan, Julius Reyes, Jay Camacho, Jesse Hapadei, Paul Lisua, Manny Pangelinan, Marvin Pangelinan, Arnold Palacios, Bernice Sablan,
Tammy Summers, Northern Marianas College, Severino Alforeza III, John Furey, Lee Roy Sablan, APASEEM, Ross Miller, Kim Peterson, KKMP,
Karen and Scott Pletzer !
!