J o u r. T r o p. C o l e o p. 1 ( 2 ), 25 - 34 C o p y r i g h t @ 2 0 2 0 U n i v e r s i t y P r e s s J O U R N A L O F T R O P I C A L C O L E O P T E R O L O G Y Notes on habitat specificity and occurrence of some Philippine tiger beetles: Input to tropical biodiversity conservation Milton Norman Medina Institute for Biodiversity and Environment, Coleoptera Research Center, University of Mindanao, Davao City, 8000, Philippines Email: [email protected] Abstract This paper provides additional proof that tiger beetles have specific habitat preferences based on ten years of field observations from the five protected mountain ranges in Davao Region, Mindanao, Philippines. Species-specific occurrence is more helpful in habitat assessment than using the whole taxon. Each tiger beetle species reflects specific habitat types. Thopeutica Chaudoir, 1861 prefers healthy forest and pristine fluvial systems. Heptodonta nigrosericea (W.Horn, 1930) prefers to inhabit between close forest canopy and agro-ecosystem, while species under Calomera Motschulsky, 1862, Cylindera Westwood, 1831, and Therates Latreille, 1816 can tolerate certain degrees of human disturbance. Using tiger beetles as indicator species should require identification up to species level and the type of habitat they occupy. Furthermore, species occurrence is more dependent on ecosystem type rather than the elevation gradient. Keywords: Cicindelidae, ecosystem, indicator species, tiger beetles, Philippines Introduction It is already known that tiger beetles serve as indicator species (Cassola & Pearson, 2000; Dangalle et al., 2014; Rainio & Niemela, 2003; Spector & Forsyth,1998) and occupy a narrow or very narrow habitat specialization (Ganeshaiah & Belavadi, 1986; Jaskuła, 2011; Satoh et al. 2006). However, detailed notes on intergeneric analysis on species specificity seem not fully studied. Based on 10 years of observations in the field, it was found that some species have a range of tolerance to various types of habitats, i.e. species that thrive in lowland to upland, from greatly disturbed to secondary forests while others have a very restricted distribution. In this paper, a landscape overview of how tiger beetles are distributed from lowland to upland, secondary and primary forests is presented. Notes on which species indicates the state of certain habitat is also added. For the first time, a more specific perspective of how tiger beetles thrive in a specific habitat particularly in the Philippines and perhaps other tropical countries is provided and illustrated. This is very important particularly in analyzing habitat change and the data will also serve as input to policy towards conservation of our species (Cassola & Pearson, 2000). Considering that the Philippines is a mega-diverse country at the same time a mega- diverse hotspot (Catibog-Sinha & Heaney, 2006; Heaney & Regalado, 1998; Mittermeier et al. 2004, 1999; Myers, 1998; Myers et al. 2000) while climate change (Lasco et al. 2008) and human disturbance (Arndt et al. 2005; Costa & Zalmon, 2019; Knisley, 2010; Knisley & Brzoska, 25 Published: 22 Nov. 2020 J o u r. T r o p. C o l e o p. 1 ( 2 ), 25 - 34 C o p y r i g h t @ 2 0 2 0 U n i v e r s i t y P r e s s J O U R N A L O F T R O P I C A L C O L E O P T E R O L O G Y 2018; Knisley & Hill, 1992) impaired tiger beetles population, thus, conservation of our species (Hague et al. 1986; Posa et al. 2008) requires specific conservation plans coupled with transformative education (Medina & Taylor, 2019). By looking at a landscape model of how our tiger beetles are spread across micro and macro habitats (Nolte et al. 2019; Schultz & Hadley, 1987), we can have a general perspective as to the extent of habitat deterioration and necessary actions can be more specific especially those areas that hold endemic and threatened species. By looking at a landscape model of how our tiger beetles are spread across micro and macro habitats (Nolte et al. 2019; Schultz & Hadley, 1987), we can have a general perspective of the extent of habitat deterioration and the specific actions to be taken especially those areas that hold endemic and threatened species. Materials and Methods The analysis of tiger beetles’ habitat preferences was taken from the proponent’s 10 years of fieldwork from 2010 up to 2020 in the Eastern Side of Mindanao Philippines. These include field visits to important biologically diverse mountains in the Eastern Mindanao Biodiversity Corridor (EMBC) which includes Mt. Hamiguitan Range Wildlife Sanctuary in Davao Oriental [6°46'23.72"N, 126°13'15.43"], eastern side of Mt. Apo in Catigan Toril [7°01' 11.89"N, 125°22'18.56"], Marilog Forests [7°26'55.00"N, 125°22'28.10"], Mt. Candalaga in Maragusan Davao de Oro [7°21'16.97"N, 126°11'05.09"], and Mainit Hot Spring Protected Landscape [7°28' 45.91"N, 126°01'47.79"] (Fig. 1). Each mountain was visited at least once a year for 10 years with 5 days of minimum fieldwork, a total of at least 50 field observations. The established elevation levels are based on the change of habitat types which ranges from 80 masl to 1400 masl. Observations were made in three elevation types: lowland from 80 – 300 masl usually occupied mostly by human habitation, farmlands; midrange from 300 – 800 masl with less human habitation with prominent secondary dipterocarps; and highland forest from 800-1,400 masl which is covered by secondary to primary forests and pristine fluvial systems. Identification of specimens was made by examining the type materials in the following museums’ and personal collections: Museum fur Tierkunde Dresden (MTD), University of Mindanao Coleoptera Research Center (UMCRC), Jürgen Wiesner Collections (JWC), Daugavpils University Biological Collections (DUBC), and author personal collections. Photographs were made using Canon EOS200DII using MP-E 65mm Canon Macro Photo Lens. Helicon Focus 7.5.6 Pro software was used to process photo stacking, and a licensed Photoshop software was used to clean the digital images. Results and Discussion The species of tiger beetles in focus include Calomera mindanaoensis Cassola, 2000, Thopeutica petertaylori Medina, Cabras, Wiesner, 2019, T. rollandmuelleri Cassola 2000, Therates fasciatus quadrimaculatus Horn, 1895, T. fulvipennis everetti Bates, 1878, Prothyma heteromallicollis heteromallicollis W.Horn, 1909, Cylindera (Ifasina) discreta elaphroides (Dokhtouroff, 1882), C. (Ifasina) mouthiezi Dheurle, 2015, and Heptodonta nigrosericea (W.Horn, 1930). It is fascinating to note that tiger beetles showed a consistent range of preferred habitats. For example, species under the genus Cylindera, specifically C. (Ifasina) mouthiezi Dhuerle, 2015 and C. (Ifasina) discreta elaphroides (Dokhtouroff, 1882) are found in the lowland ecosystems and can tolerate human disturbance. These are strictly epigeic species that heavily rely on fluvial 26 Published: 22 Nov. 2020 J o u r. T r o p. C o l e o p. 1 ( 2 ), 25 - 34 C o p y r i g h t @ 2 0 2 0 U n i v e r s i t y P r e s s J O U R N A L O F T R O P I C A L C O L E O P T E R O L O G Y ecosystem. Similar observation for both species in Barangay Linoan, Montevista Davao de Oro (30-80 masl) where C. mouthiezi Dhuerle, 2015 and C. discreta elaphroides co-inhabit at the same micro-habitat. Although, there is no observation recorded for both species having a predatory relationship towards each other. Moreover, field observation at the foot of Mt. Candalaga Range (~800-1,200 m a.s.l.) documented the existence of C. discreta elaphroides (Dokhtouroff, 1882) but without co-existence with other Cylindera species. Despite its high elevation, the ecosystem is prominently agro-ecosystem with patches of secondary forest with few human habitations. This proves that the occurrence of species do not necessarily follow the elevation gradient but on the change of ecosystem type. Figure 1. Map of Mindanao showing the location of observation sites Cassola (2000) noted in his description of Calomera mindanaoensis (Cassola, 2000) that this species may sympatrically or even syntopically occurred with C. lacrymosa Dejean, 1825. My field observations in Barangay Tawan-tawan in Davao City proved that the two species occurred sympatrically in one river but both species occupy different microhabitats within the same river bed (Fig. 3). There is no evidence that both species syntopically occurred in a single microhabitat thus each species co-exists as separate populations. Moreover, C. lacrymosa Dejean, 1825 seems to inhabit a lowland ecosystem with direct sunlight as they need it for faster metabolism (Pearson, 1998) and often prefer sandy soil to rocky as compared to C. mindanaoensis Cassola, 2000. Calomera mindanaoensis Cassola, 2000 has a longer range of habitats and greatly distributed in the entire greater Mindanao from lowland to middle 27 Published: 22 Nov. 2020 J o u r. T r o p. C o l e o p. 1 ( 2 ), 25 - 34 C o p y r i g h t @ 2 0 2 0 U n i v e r s i t y P r e s s J O U R N A L O F T R O P I C A L C O L E O P T E R O L O G Y elevation (i.e. 800-900 masl) and thrives in several soil types, rocky, sandy, clayish, and ultramafic as observed in Mt.