Judul: Identifikasi dan Pendugaan Jumlah Instar Kumbang Penggerek Ranting (Coleoptera: Curculionidae) pada Albizia, Falcataria moluccana (Miquel) Barneby & J.W. Grimes di Maluku
Abstrak: Albizia, or Falcataria moluccana (Miq.) Barneby & J.W. Grimes is known as “sengon” in Indonesian, “jeungjing” in Java, and “salawaku” in Maluku. This tree is native to Indonesia, originating from Maluku and Papua. As a fast-growing tree, F. moluccana is reported to be an invasive species in the lowland humid forests on the Pacific and Indian Ocean islands. In the natural habitat of F. moluccana, the twig borer weevil (Coleoptera: Curculionidae) is found. The weevil is an important pest of F. moluccana and can be used as a candidate for its natural enemies. Information regarding the weevil was not available before. The aims of this study are (1) to study the taxonomy of the Albizia twig borer weevil through morphological and molecular characters in Maluku Province, (2) to descibe sexual dimorphism based on morphological characteristics and measuring the morphometrics of the Albizia twig borer weevil in Maluku Province, (3) to estimate the number of larval instars of the Albizia twig borer weevil in Maluku Province. The study provides information of taxonomy, morphological, morphometric, and molecular characters, as well as estimation of the larval instar numbers of the Albizia twig borer weevil in Maluku Province, Indonesia. This research was conducted from February to December 2022. Samples of weevils and larvae were collected at Albizia plantations which grow naturally around the roadside in Maluku Province, which are spread over three islands: Ambon, Seram, and Haruku Islands. The research was conducted with three main topics: morphological and molecular identification; sexual dimorphism of adults through external body morphology and morphometric measurements, and estimation of larval instar numbers. Morphological identification was conducted using a dichotomous key at the subfamily and tribe levels, and it was further compared and matched with type specimens in the museum. Molecular identification utilized the mtCOI gene, employing the forward primer (3'-GGTCAACAAATCATAAAAGATATTGG-5') and the reverse primer (5'-TAAACTTCAGGGTGACCAAAAAATCA-3'). Morphometry involved measuring 25 females and 21 males on 18 body parts, including BL (total body length), RL (rostrum length), MRL (metarostrum length), RAW (rostrum apex width), RBW (rostrum base width), SL (scape length), FL (funicle length), ProL (pronotum length), ProW (pronotum width), ProBW (pronotum base width), EL (elytra length), EBW (elytra base width), EWMax (elytra maximum width), EWMin (elytra minimum width), EAW (elytra apex width), Fem1L (first femur length), Tib1L (first tibia length), and Tar1L (first tarsus length). Differences in morphometric measurements between males and females were analyzed using a t-test (P < 0.05) on Minitab ver. 21. Principal component analysis (PCA) was used to assess variation in morphometric characters and determine which characters were the most representative in size between males and females on PAST ver. 4.11. Larval instar numbers were estimated by measuring head capsule width at the widest point of the head capsule. Kernel density estimation (KDE) was used to estimate the number and limits of instars. Gaussian mixture model (GMM), a clustering model, was applied to ensure the number of instars derived from KDE. The results of this study were expected to provide important information regarding the Albizia twig borer weevil in Maluku Province, Indonesia and offer basic insights into natural
Keyword: Ithyporini, molecular, morphology, rostrum, sengon