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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 ! !