Research Article Journal of Orthoptera Research 2019, 28(1): 21-26 The floriphilic katydid, Phaneroptera brevis, is a frequent flower visitor of non- native, flowering forbs Minc KAI TAN!, Hut Lee!, HUGH TIANG WAH TAN! 1 Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Republic of Singapore. Corresponding author: Ming Kai Tan (orthoptera.mingkai@gmail.com) Academic editor: Michel Lecoq | Received 13 January 2019 | Accepted 20 February 2019 | Published 17 May 2019 http://zoobank.org/986AA 1 EA-24FE-4B30-9865-7960FCB7871F Citation: Tan MK, Lee H, Tan HTW (2019) The floriphilic katydid, Phaneroptera brevis, is a frequent flower visitor of non-native, flowering forbs. Journal of Orthoptera Research 28(1): 21-26. https://doi.org/10.3897/jor.28.33063 Abstract Distribution of consumers in a patch of vegetation can be predicted by resource availability and explained by the resource-concentration and optimal-foraging hypotheses. These hypotheses have not been explored for flower-visiting Orthoptera because they are deemed less economically or ecologically important. Some flower-visiting orthopterans can provide pollination services, which warrants more attention. We studied a Singa- porean, floriphilic katydid, Phaneroptera brevis, to investigate the following questions: 1) how frequently does P. brevis visit flowers compared to other flower visitors and 2) what factors predict the abundance of P. brevis? We col- lected abundance data for P. brevis and other flower-visiting arthropods and quantified seven environmental parameters, including flower abundance and host-plant species richness. We found that P. brevis frequents flowers significantly more often than some common and expected flower visitors such as hoverflies. In line with the prediction of the resource-concentration hypothesis, the abundance of P. brevis was positively correlated with a high- er flower abundance. Owing to the limited information on unexpected wild flower visitors and pollinators, especially from the understudied tropics of Southeast Asia, we propose that P. brevis can be a model organism for future studies to answer fundamental questions on flower visitation. Key words florivores, flower visitor, optimal foraging, Orthoptera, resource concentration Introduction Resource availability (such as that of a floral resource) can help to predict how consumers (including pollinators and floriv- ores) are distributed in a patch of vegetation, and this consumer- resource relationship has been studied extensively under various theoretical frameworks (e.g. resource-concentration hypothesis) to examine the interactions between insects and plants (e.g. Otway et al. 2005, Andersson et al. 2013). The resource-concentration hy- pothesis (Root 1973) was one of the earliest hypotheses proposed to explain insect-plant interactions, particularly of insect pests on monocultures and polycultures of agricultural crops (Andow 1991, Rhainds and English-Loeb 2003). It predicts that an insect occurs at a higher density when its host-plant species occurs at a greater density or patch size (Kareiva 1983, Rhainds and English-Loeb 2003). A mechanism to explain such a relationship is the optimal- foraging hypothesis, which predicts that the insect can forage more optimally or efficiently in a patch with a greater density of host plant species since the insect is more likely to find and utilize its host plant, for example for feeding and as a reproduction substrate, while spending less time and energy on travelling and exposing itself to predation while travelling (e.g. Pyke 1984, Sowig 1989). The resource-concentration and optimal-foraging hypotheses have been tested extensively on various flower-visiting insects, par- ticularly mutualistic pollinators such as bees (e.g. Real 1981, Sowig 1989, Goulson 2000, Westphal et al. 2003, Vrdoljak et al. 2016), probably owing to the importance of these insects in fruit farming. However, not all flower-visiting insects are equally well-studied, es- pecially those deemed to be less economically or ecologically impor- tant. Examples of these understudied flower-visiting insects include the orthopterans. Although orthopterans are probably more diverse flower-visitors than previously thought (Tan et al. 2017a), they are rarely considered as important flower visitors in ecological studies. This is partly because there are few studies on how their abundances can be predicted by floral resources or other biotic and abiotic factors. Phaneroptera brevis (Serville, 1838) (Fig. 1) is a tropical flo- riphilic katydid from Southeast Asia which has been observed to visit and feed on the flowers of many host-plant species (Tan et al. 2017a). Although Tan and Tan (2018a) recently also observed that the gentle foraging behavior can help with pollination in an insectary setting, we are unaware of how abundant these flower- visiting katydids are in their natural environment, how frequently they visit flowers, and why. Without these data, it is not possible to assess the importance of these flower-visiting katydids in flowering communities and their pollinating efficiency. In this study, we aim to investigate the following two research questions: 1) how frequently does P. brevis visit flowers compared to other flower visitors and 2) what factors predict the abundance of P. brevis? We counted the types of flower-visiting arthropods (including P. brevis) and measured environmental and resource parameters in a wasteland site in Singapore that is representative of the habitat of P. brevis. We predicted that P. brevis is a frequent flower visitor and that its abundance can be predicted by resource abundance in accord- ance to the prediction of the resource-concentration hypothesis. JOURNAL OF ORTHOPTERA RESEARCH 2019, 28(1) 22 Fig. 1. A. Immature and B. Adult male individuals of Phaneroptera brevis visiting a capitulum of Sphagneticola trilobata (A) and an in- florescence of Sesbania sesban (B) at the study site in Singapore in the day (A) and at night (B). The arrows in the inset (a-i) indicate pollen grains attached to the body of the individual. Materials and methods Study subject.—Phaneroptera brevis belongs to the subfamily Phan- eropterinae which is a group of katydids known to visit flowers. Native to Southeast Asia, P. brevis has been observed to visit and feed on the flowers of at least 13 species (Tan et al. 2017a). In Sin- gapore, it is relatively common in open grasslands and forest edges that contain many flowering forbs, particularly on sites which con- tain Bidens pilosa L. (Asteraceae), Sphagneticola trilobata (L.) Pruski (Asteraceae), and Neptunia plena (L.) Benth. (Fabaceae) (Tan et al. 2017a). Although little is known about the life history of this ka- tydid, several studies have examined the foraging behavior of P. brevis (e.g. Tan and Tan 2017, Tan et al. 2017b) and showed that this katydid prefers flowers to leaves (Tan and Tan 2017) and that its foraging performance can be influenced by flower abundance (Tan et al. 2017b). Study locations and sampling.—Sampling for flower-visiting ar- thropods was conducted in a wasteland site of about 2,390 m7? in Lorong Lada Hitam, off Mandai Road, Singapore (N1.41846°, E103.79164°). This site is dominated by non-native, naturalized weedy plants including Bidens pilosa and Neptunia plena. Surveys were conducted about once a week on non-rainy days at three broad time periods: in the morning (10 am-12 pm), afternoon M.K. TAN, H. LEE AND H.T.W. TAN (3-5 pm), and evening (7-9 pm). The surveys were conducted between August and September 2018. The same surveyor was in- volved in observing and recording the data throughout the surveys. Data collection.—To minimize sampling bias, we first generated ran- domized points within the 2,390 m? wasteland site using QGIS software version 2.18.7 (QGIS Development Team 2019). A circu- lar PVC hoop (i.e. hula hoop) of 70 cm interior diameter was used to delineate sampling quadrats, with the center of the hoop placed over the location of the GPS coordinates of the randomized points. We used a circular quadrat (area 0.385 m7’) because it has a lower perimeter-to-edge ratio than a square quadrat. For each survey, six quadrats were sampled. The hoop was gently placed over the vege- tation with minimal disturbance. The hoop was then left for at least 20 min for the insects to acclimatize to the hoop before sampling began. Two methods were then employed (in the following order) to ensure a comprehensive survey of the flower-visiting insects: 1) Snapshot method (Garbuzov and Ratnieks 2014). For 30 s we counted and visually identified flower-visiting insects within each hoop. Earlier trials suggested that 30 s provided more than sufficient time for a snapshot survey of the flower-visiting insects for the size of the hoop used. This method allowed for a com- prehensive sampling of the most prominent but fleeting flow- er-visiting insects such as Lepidoptera (butterflies and moths), Aculeata (bees and wasps), and Diptera (including hoverflies). 2) Timed interval method. While the snapshot method allowed a comprehensive sampling of Lepidoptera and Aculeata, less- fleeting and more well-camouflaged flower visitors (e.g. P. bre- vis and crab spiders) may be overlooked. To compensate for this, for the next 5 min we did a more thorough search for more cryptic insects, which included P. brevis, within the hoop. As it was impracticable to count the number of ants within the hoop, we only recorded the absence or presence of ants. To obtain the total number and species of flower-visiting in- sects within each sampling point, data from both methods were pooled together. Only active flower-visiting insects, defined as any insect that intentionally moved in or on an inflorescence thereby touching the reproductive organs of the flower (Knop et al. 2018), were included. The total number of P. brevis adults and immatures inside the hoop was counted and we took note of whether the katydid was on a flower or on the leaves. We grouped the flower-visiting arthropods into broad flower visitors: 1. Crickets and other katydids (suborder Ensifera, order Orthop- tera); 2. Grasshoppers (suborder Caelifera, order Orthoptera); 3. Bees and wasps (subclade Aculeata, suborder Apocrita, order Hymenoptera, but not including the ants); 4. Ants (family Formicidae, suborder Apocrita, order Hymenop- tera); 5. Floriphilic hoverflies (family Syrphidae, order Diptera); 6. All other flies (order Diptera); 7. Butterflies and moths (order Lepidoptera); 8. Cockroaches (order Blattodea); 9. Beetles (order Coleoptera); 10. True bugs (order Hemiptera); 11. Flower-visiting crab spiders (family Thomisidae, order Araneae). The vegetation was also sampled within the hoop. Specifi- cally, the number of plant species was recorded. For flowering JOURNAL OF ORTHOPTERA RESEARCH 2019, 28(1) M.K. TAN, H. LEE AND H.T.W. TAN species, the number of flowers was also counted for each spe- cies. For Asteraceae and Fabaceae species, inflorescences were counted instead of individual florets or flowers, respectively. We excluded the data for the Poaceae (grasses) owing to the vast- ly different floral morphology. Poaceae from the site are also mostly wind-pollinated so do not usually attract insect visitors (Culley et al. 2002). Environmental variables, including the brightness and temperature, were recorded using a HOBO pen- dant temperature/light 64K data logger. In total, 36 quadrats were sampled for altogether 107 times (over three time periods). One quadrat did not have complete data over the three time periods because of the presence of aggressive territorial dogs in the evening. Data analysis. —To examine how frequently P. brevis visited flowers in comparison with other flower-visiting insects, we compared the frequency of visits to flowers for each type of flower-visiting insect. This was done by fitting a generalized linear mixed-effects model (GLMM) with the Poisson error via the log-link function using the glmer function from the R package Ime4 (Bates et al. 2014). The flower visitor group was used as a fixed effect. The plot number was used as a random effect since each plot was sampled three times over the three time periods. We compared the least-square means of the frequency of visits to flowers between P. brevis and the different flower visitors using the emmeans function of the R package emmeans (Lenth 2018). To investigate which factors predict the abundance of P. bre- vis, we performed a model selection via the information-theo- retic approach (see Suppl. material 1 for more details). We first proposed a total of 39 candidate models with the abundance of P. brevis as the response (see Suppl. material 1 for the details and explanation of each proposed model). Each model con- tained a different combination of the following predictors: 1) abundance of all flower-visiting insects, 2) abundance of am- bush predator crab spiders, 3) abundance of main competitors (bees, see Lindstr6m et al. 2016), 4) presence or absence of ants, 5) time period of sampling (see Knop et al. 2018), 6) total flow- er abundance, and 7) plant species richness. We ensured that all models were biologically meaningful and not overfitted. We then ranked the models using the small sample size-corrected version using the Akaike information criterion (AICc) and the Akaike weights using the R package MuMIn (Barton and Barton 2015) (see Suppl. material 1 for how they were used to compare the models). All statistical analyses were conducted using R software v.3.5.1 (R Core Team 2018). Results We observed that P. brevis frequents flowers significantly more often than some common and expected flower visitors such as hoverflies (Fig. 2); only bees and crab spiders visited flowers more frequently. P. brevis also frequents flowers more than lepidopter- ans, although this difference is not significant (Fig. 2). We did not observe any flower-visiting grasshoppers, beetles, and true bugs. Ants were encountered in 23 of 107 samples. The best performing model for explaining the abundance of P. brevis (among 39 proposed models) contained flower abun- dance and the presence or absence of ants as important vari- ables (R’gisimmy = 9-06, Rem = 0-22) (Table 1). Specifically, a high abundance of P. brevis was found to be associated with 23 Least-square mean frequency of visitors on flowers P. brevis Bees Lepidopterans Hoverflies Dipterans Cockroaches Spiders Flower visitors Fig. 2. Comparison of the least-square means of the frequency of visitors on flowers between P. brevis and other flower visitors. A generalized linear mixed-effects model with Poisson errors was fit- ted with different flower visitor as the fixed effect and the replicate number as the random effect. The significance between P. brevis and each flower visitor group is denoted as follows: **P<0.01; PS P