Backyard biodiversity: Unraveling life histories of the new fly species discovered by the BioSCAN Project proves harder than first assumed

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1 Journal of Negative Results Ecology & Evolutionary Biology vol. 12: 1 8 Helsinki, 19 March 2018 ISSN Backyard biodiversity: Unraveling life histories of the new fly species discovered by the BioSCAN Project proves harder than first assumed Emily A. Hartop*, Lisa A. Gonzalez & Brian V. Brown Urban Nature Research Center, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, California, 90007, United States of America (*corresponding author s emily.a.hartop@gmail.com) Received 13 December 2016, accepted 17 January 2018 In 2014, an urban biodiversity study sampling primarily from private backyards in Los Angeles, California (USA) collected 43 species of Megaselia (Diptera: Phoridae) previously unknown to science. These species have now been described, but their life histories are completely unknown. This study used traditional rearing techniques in an attempt to reveal the food resources needed for larval development and to shed light on the ecological roles of these new species. Despite dozens of attempts at attracting and rearing the newly-described flies with various substrates, however, our work failed to fully uncover any of the 43 life histories. Examination of collection data from preserved phorid flies in the extensive collection of the Natural History Museum of Los Angeles County offered few clues, none of which we were able to replicate in our work. Three of the new species were collected from a soil emergence trap, but this offers only partial data for their life histories. Our inability to attract these flies to a variety of decomposing materials, the supposed generalized larval food of phorid flies, points to the exciting potential for previously unrecorded, diverse, and specialized life histories. Introduction Megaselia Rondani is a megadiverse genus of phorid flies (Diptera: Phoridae), possibly the most diverse genus of insects on earth (Bickel 2009). Both the family Phoridae and the genus Megaselia have a large variety of lifestyles (predators, scavengers, parasitoids, fungivores, etc.) (Disney 1979, 1990, 1994). This diversity makes them especially interesting as ecological subjects. The BioSCAN (Biodiversity Science: City and Nature) Project is an ongoing insect inventory being conducted by the Natural History Museum of Los Angeles County (LACM) (project details in Brown et al. 2014). The project discovered forty-three new species of Megaselia in the city of Los Angeles (Hartop et al. 2015, 2016a, 2016b). Soon after the discovery of so many new species, a top priority became discovering what they were doing in the urban environment. Discovering the life histories of these flies will allow for better analysis of distribution and abundance data in an ecological context. The intention of this study was to introduce a variety of different baits into the same habitats (BioSCAN study sites) where the newly described species were originally collected (Hartop et al. 2015, 2016a, 2016b) with the goal of determining Editor in charge of this manuscript: Mike Fowler

2 JNR EEB vol. 12 Hartop et al.: Backyard bait trials 2 Fig. 1. Rearing chambers after exposure. Fig. 2. Baits during exposure. larval substrate preference. In addition to formal bait trials, we conducted supplementary investigations that we hoped might guide future bait trials. These included rearing from collected substrates and examination of both museum specimens and of phorids from a soil emergence trap. These exploratory studies started prior to our formal trials, with the initial collection and rearing of found materials inspiring the implementation of a more formal bait trial program. Methods Our study used thirty-two different baits to attract egg-laying phorids (Fig. 1). A diverse selection of baits was chosen, including substrates known to be utilized by species in this group (Disney 1994). Approximately 100 grams of each bait was put in the bottom half of a rearing chamber, and a fine screen was used to prevent larger invertebrates from gaining access (Fig. 2). The baits were either

3 JNR EEB vol. 12 Hartop et al.: Backyard bait trials 3 Table 1. Exposed baits and reared species (* indicates bait found and used locally, all other baits were purchased at the supermarket for the purpose of these trials). Exposed bait Reared species Location Start exposure End exposure Emergence date Crushed Eisenia fetida* none LACM Gardens 14 June June 2016 none Crushed slugs (species unknown, collected at site)* none LACM Gardens 14 June June 2016 none Crushed Armadillium vulgare* none LACM Gardens 14 June June 2016 none Chopped beef (Bos taurus) muscle none LACM Gardens 21 June June 2016 none Cow (Bos taurus) foot none LACM Gardens 21 June June 2016 none Pig (Sus domesticus) foot Megaselia scalaris LACM Gardens 21 June June August 2016 Beef (Bos taurus) tripe none LACM Gardens 21 June June 2016 none Dead cockroaches (species unknown, collected at site)* none Highland Park, CA 1 July July 2016 none Fresh strawberries (Fragaria ananassa) none Highland Park, CA 1 July July 2016 none Cracked chicken (Gallus gallus domesticus) egg none Highland Park, CA 12 July 2016 Trap destroyed none Crushed Armadillium vulgare* none LACM Gardens 29 June July 2016 none Chicken (Gallus gallus domesticus) wing none LACM Gardens 29 June July 2016 none Pork (Sus domesticus) rib none LACM Gardens 29 June July 2016 none Beef (Bos taurus) muscle none LACM Gardens 29 June July 2016 none Penaeid shrimp (sold commercially Spiniphora bergenstammi LACM Gardens 29 June July August 2016 as Jumbo shrimp, species unknown) Store-bought White Fish Fillet (species unknown) none LACM Gardens 29 June 2016 Trap destroyed none Cat (Felis catus) feces* none LACM Gardens 30 June July 2016 none Chicken (Gallus gallus domesticus) jerky none Highland Park, CA 14 September September 2016 none

4 JNR EEB vol. 12 Hartop et al.: Backyard bait trials 4 Table 2. Buried baits and reared species (* indicates bait found and used locally, all other baits were purchased at the supermarket for the purpose of these trials). Buried bait type Reared species Location Start exposure End exposure Emergence date Beef (Bos taurus) liver Megaselia scalaris LACM Gardens 12 July July August 2016 Beef (Bos taurus) steak none LACM Gardens 12 July July 2016 none Beef (Bos taurus) tendon none LACM Gardens 12 July July 2016 none Beef (Bos taurus) tongue none LACM Gardens 12 July July 2016 none Beef (Bos taurus) tripe none LACM Gardens 12 July July 2016 none Cow (Bos taurus) foot Megaselia scalaris LACM Gardens 12 July July 2016 Began 26 July 2016 and continued for weeks Chicken (Gallus gallus domesticus) meat none LACM Gardens 12 July July 2016 none Mourning Dove (Zenaida macroura)* none Monrovia, CA 12 August August 2016 none Pork (Sus domesticus) feet none Monrovia, CA 12 August August 2016 none Chicken (Gallus gallus domesticus) breast none Monrovia, CA 12 August August 2016 none Salmon (store-bought, species unknown) none Monrovia, CA 12 August August 2016 none Penaeid shrimp (sold commercially none Monrovia, CA 12 August August 2016 none as Jumbo shrimp, species unknown) Beef (Bos taurus) tripe none Monrovia, CA 12 August August 2016 none Dog (Canis familiaris) feces* none Monrovia, CA 12 August August 2016 none

5 JNR EEB vol. 12 Hartop et al.: Backyard bait trials 5 exposed (Table 1) or buried under 2 inches (5.1 cm) of soil in the chamber (Table 2). Soil used was topsoil collected at the exposure site and was not modified in any way. Baits were contained in cages (closed live animal traps) to prevent disturbance by mammals (Fig. 2). The aggregation of baits is not thought to be a complicating issue for this study; these are small flies that must regularly navigate complex urban environments with many competing sensory cues. Baits were exposed for one week during either June or August 2016 (two of our baits had slightly longer exposure times, see Tables 1 and 2). Most species of Megaselia are present year-round as adults, and the genus is collected by the tens-of-thousands in the BioS- CAN project (Brown & Hartop 2016). We conducted our trials in June and August because these are months with high numbers of phorids caught in the BioSCAN Project and moderate temperatures (lows around 16 C and highs between 27 and 33 C) (Brown & Hartop 2016). Traps were positioned in partially sheltered spots allowing for full, but not continuous, sun. Malaise trapping from the BioSCAN project at these same sites clearly indicates there is no scarcity of phorids at either site, hundreds of phorids representing dozens of species were trapped weekly at both sites used in this study (Brown & Hartop 2016). After exposure, rearing chambers were collected and brought back to LACM and placed on outside shelving units under a shade shelter. Chambers were monitored daily over the course of three months and any emergence was recorded. Flies were collected with an aspirator from the upper half of the rearing chambers (if necessary, chambers were briefly placed in a freezer to slow fly movement for easy capture) and preserved in 95% ethanol for identification. All specimens were examined with a Leica M165C stereo microscope. Reared specimens were identified by Emily Hartop, a phorid taxonomist who is an expert on the local fauna (Brown & Hartop 2016, Hartop et al. 2015, 2016a, 2016b). Species were all abundant and common; specimens were discarded after identification. In addition to our bait trapping, we conducted secondary collection using three methods. These were not experimental trials, but exploratory investigations. We collected a wide variety of materials (dead/decaying) that might be likely to be used by phorids, in addition to mushrooms (a known food source for some phorids), and one species of flower/bud (a known, but uncommon substrate for phorids) (reviewed by Disney 1994). We also examined specimens that were found in a soil emergence trap in Monrovia, CA, and examined specimens from the collection at the LACM that had associated life history data. It was our hope that these bits of data might prove interesting and could be replicated in later bait trials. We include this information as supplementary data, as they may provide preliminary data that could be useful in setting up future experiments. Secondary methods: 1. Collection of found materials that were possible breeding substrates from around Los Angeles, including from BioSCAN backyards and the LACM Nature Gardens (Table 3). 2. Collection of specimens from a soil emergence trap in a backyard in Monrovia, CA. 3. Examination of the LACM collection for any unidentified Megaselia with life history data. Results Bait trials Four of the baits in our trials yielded phorids. Megaselia scalaris, a well-known generalist (Disney 2008), was reared from exposed pig feet, buried beef liver and buried cow foot (Tables 1 and 2). Spiniphora bergenstammi, a known scavenger, was reared only from exposed jumbo shrimp. Secondary collection methods Most of the collected materials (Table 3) did not produce any phorids, but both the dead opossum and trash yielded M. scalaris. The three types of fungi collected (Table 3) all yielded M. agarici, a common species in Los Angeles and known fungivore. Phorids from a long-running emergence trap from a backyard in Monrovia, CA yielded three

6 JNR EEB vol. 12 Hartop et al.: Backyard bait trials 6 Table 3. Collected materials. Location of collection noted, species noted if known/identifiable when found. Collected material Reared species Location Collection date Emergence date Agaricus sp. Megaselia agarici Peck Reservoir, CA 16 April 2016 Exact date unknown; within a week of collection Calvatia pachyderma Megaselia agarici Eagle Rock, CA 1 May 2016 Exact date unknown; within a week of collection Chlorophyllum brunelum Megaselia agarici Monrovia, CA 6 April 2016 Exact date unknown; within a week of collection Crushed snail (Cornu aspersum) none Rosemead, CA 24 May 2016 none Rotten fish (species unknown) none Lake Gregory, CA 28 June 2016 none Deer feces (species unknown) none Monrovia, CA 3 July 2016 none Dog vomit fungus (Fuligo septica) none Monrovia, CA 3 July 2016 none Dead crickets (species unknown) none Indoors in animal care, LACM 5 11 July 2016 none Erigonum cinereum buds none LACM Gardens 13 July 2016 none Erigonum arborenscens flowers none LACM Gardens 13 July 2016 none Vulture pellets (species unknown) none Monrovia, CA 9 July 2016 none Dead dragonfly (species unknown) none Lake Gregory, CA 28 June 2016 none Dead opossum (species unknown) Megaselia scalaris LACM Gardens 13 July July 2016 Dog (Canis familiaris) feces n/a Highland Park, CA 14 September 2016 none Trash (mixed food, paper and plastic waste) Megaselia scalaris Highland Park, CA 14 September September 2016

7 JNR EEB vol. 12 Hartop et al.: Backyard bait trials 7 of the newly described species (M. steptoeae, M. wiegmanae and M. lombardorum). Examination of previously collected material in the LACM collection gave records for M. lombardorum in liver and snail Buck traps (Buck 1994) from collections done in October 1988 in Santa Ynez Canyon, a natural area in the Santa Monica Mountains just outside of Los Angeles. A single specimen of M. risoria (Hartop et al. 2016a) from a dead Malacosoma (Lepidoptera: Lasiocampidae) caterpillar from Edmonton, Alberta, Canada (12 July 1989) was an interesting, but lone, data point. Discussion Our bait trials were completely unsuccessful in revealing life history data for any of the newly described phorid flies in Los Angeles despite the diversity of baits utilized. Partial data for only four of the forty-three newly described species were recovered from our secondary study materials. Interestingly, although we found records of M. lombardorum in liver and snail Buck traps in Santa Ynez Canyon in the Santa Monica Mountains, just outside of Los Angeles, we were unable to replicate these results in our bait trials. The emergence of three species (M. steptoeae, M. wiegmanae and M. lombardorum), from soil requires further investigation to determine specific host data. The presence of M. scalaris on three of the baits and in two of the collected items was not surprising, given the wide variety of rearing records for this species. More surprising is that this species occurs in relatively low numbers in BioS- CAN samples, but is clearly the most commonly encountered generalist scavenger. Interestingly, another well-known generalist, Dohrniphora cornuta, was not reared from any of our baits. Conclusions Although at first disappointing, our negative results point to the intriguing possibility that many of the newly described Megaselia have unique and specific life histories that may take many years (and some luck!) to unravel. Perhaps some are kleptoparasites on native tarantulas (Weinmann & Disney 1997), predators of amphibian eggs (Davis & Disney 2003), or visiting unusual regional flowers (Bänziger & Disney 2006). It is our hope that a wide variety of fascinating life histories that these flies exhibit can be revealed with continued efforts. Acknowledgments We thank the entire BioSCAN team, including our many students and volunteers. Support for BioSCAN comes from the Natural History Museum of Los Angeles County, the Seaver Foundation, and Western Exterminator. This is publication number 15 of the BioSCAN Project. References Bänziger, H. & Disney, R. H. L. 2006: Scuttle flies (Diptera: Phoridae) imprisoned by Aristolochia baenzigeri (Aristolochiaceae) in Thailand. Bulletin de la Société Entomologique Suisse 79: Bickel, D. 2009: Why Hilara is not amusing. In: Pape, T., Bickel, D. & Meier, R. (eds.), Diptera Diversity: Status, Challenges, and Tools: Koninklijke Brill NV. Brown, B. V., Borkent, A., Wetzer, R. & Pentcheff, D. 2014: New types of inventories at the Natural History Museum of Los Angeles County. American Entomologist 60: Brown B. V. & Hartop, E. A. 2016: Big data from tiny flies: patterns revealed from over 42,000 phorid flies (Insecta: Diptera: Phoridae) collected over one year in Los Angeles, California, USA. Urban Ecosystems 20: Buck, M. 1994: Community structure and niche partioning of Diptera breeding in small-sized and buried carrion (Phoridae, Sphaeroceridae). In: O Hara, J. E. (ed.), Third International Congress of Dipterology, August 1994, Abstract Volume: University of Guelph, Guelph. Davis, R. A. & Disney, R. H. L. 2003: Natural history and description of Aphiura breviceps Schmitz, a scuttle fly (Diptera: Phoridae) whose larvae prey on the eggs of frogs (Anura: Myobatrachidae) in Western Australia. Australian Journal of Entomology 42: Disney, R. H. L. 1979: Natural history notes on some British Phoridae (Diptera) with comments on a changing picture. Entomologist s Gazette 30: Disney, R. H. L. 1990: Some myths and the reality of scuttle fly biology. Antenna 14: Disney, R. H. L. 1994: Scuttle Flies: The Phoridae. Chapman and Hall, London. Disney, R. H. L. 2008: Natural history of the scuttle fly: Megaselia scalaris. Annual Review of Entomology 53:

8 JNR EEB vol. 12 Hartop et al.: Backyard bait trials 8 Hartop, E. A., Brown, B. V. & Disney, R. H. L. 2015: Opportunity in our ignorance: urban biodiversity study reveals 30 new species and one new Nearctic record for Megaselia (Diptera: Phoridae) in Los Angeles (California, USA). Zootaxa 3941: Hartop, E. A., Wong, M. A. & Eiseman, C. S. 2016a: A new species of Megaselia rondani (Diptera: Phoridae) from the BioSCAN Project in Los Angeles, California, with clarification of confused type series for two other species. Proceedings of the Entomological Society of Washington 118: Hartop, E. A., Brown, B. V. & Disney, R. H. L. 2016b: Flies from L.A., the sequel: a further twelve new species of Megaselia (Diptera: Phoridae) from the BioSCAN Project in Los Angeles (California: USA). Biodiversity Data Journal 4: e7756, doi: /BDJ.4.e7756. Weinmann, D. & Disney, R. H. L. 1997: Two new species of Phoridae (Diptera) whose larvae associate with large spiders (Araneae: Theraphosidae). Journal of Zoology 243: