Herbivory on the Holoparasitic Plant Mitrastemon yamamotoi Makino, 1909 (Mitrastemonaceae) by the Bark Beetle Coccotrypes cardamomi Schaufuss, 1905 (Coleoptera: Curculionidae)

Abstract

The bark beetle genus Coccotrypes Eichhoff (Coleoptera: Curculionidae: Scolytinae) contains ca. 120 species (Wood and Bright 1992; Bright and Skidmore 1997). Coccotrypes species are mainly distributed in tropical forests of Asia and Africa, although the northernmost limits of distribution of a few species are in warm temperate areas (Wood and Bright 1992; Bright and Skidmore 1997). Most Coccotrypes species show a preference for feeding on seeds over other plant structures, although several species in this genus are generalists capable of breeding inmultiple tissues of plants belonging to several different taxa (Browne 1961; Jordal et al. 2002). For example, Coccotrypes species have been collected from petioles (Beaver 1979a; Jordal and Kirkendall 1998) and the pith of twigs (Browne 1959). Furthermore, Coccotrypes is known to breed in ferns (Gray 1970, 1972; Browne 1973) and mangrove radicles (Browne 1961; Woodruff 1970). Coccotrypes cardamomi Schaufuss, 1905 is recorded from Sri Lanka, India, China, Sarawak (Malaysia), Sumatra (Indonesia), Taiwan, and Japan (Schaufuss 1905; Beeson 1939, 1941; Schedl 1960; Gray 1972; Nobuchi 1981). During a recent life history investigation of the holoparasitic plant Mitrastemon yamamotoi Makino (Mitrastemonaceae) (e.g., Suetsugu 2019; Suetsugu and Yoshiyasu 2019), we found C. cardamomi infesting the axes of M. yamamotoi infructescences. This was unexpected because C. cardamomi has mainly been collected in fallen fruits (Browne 1961). Here we report in detail the novel feeding ecology of C. cardamom on M. yamamotoi. During 15–16 January 2019, we haphazardly collected 20 M. yamamotoi infructescences from two populations (40 total infructescences) on Yakushima Island, Kyushu district, Japan. Infructescences were sampled from host trees, placed in separate plastic bags, and brought to the laboratory for rearing and identification of insect communities found in them. Each infructescence was placed in a separate plastic container filled with vermiculite and incubated at 20° C in the laboratory. The containers were examined daily for the presence of insects and for documenting insect feeding behavior. We found frass protruding from small holes in some of the infructescences (Fig. 1A, B). On 1 March 2019, we dissected all the infructescences. Five infructescences from site 1 were infested with an average of 3.0 ± 1.9 (mean ± SD) bark beetle adults per infructescence. Seven infructescences from site 2 were infested with an average of 3.6 ± 3.3 (mean ± SD) C. cardamomi adults per infructescence. Six larvae were obtained in an infructescence that was also infested by two adults. Furthermore, three pupae were obtained in another infructescence that was also infested by two adults (Fig. 1C). The adult beetles were examined using a stereomicroscope (Wild M3Z, Leica, Germany). They were identified by a combination of keys and descriptions in Nobuchi (1972) andMurayama (1957), then compared with specimens in our collection, which were previously identified by Hideaki Goto and Akira Ueda. Consequently, we identified all the specimens asC. cardamomi.Voucher specimens are deposited at Kyushu Research Center, Forestry and