Ancyronyx jhoanae sp. nov. (Coleoptera: Elmidae), A New Spider Rifﬂe Beetle Species from Luzon, Philippines, and New Records for A. tamaraw Freitag, 2013 †

: Ancyronyx jhoanae sp. nov., a new species of genus Ancyronyx Erichson, 1847 from Luzon is described using an integrative taxonomic approach. Illustrations of habitus and diagnostic characters are provided. Molecular analysis of a fragment of the COI 5’-end was employed to support the morphological species concept. Differences from closely related species based on molecular and morphological data are discussed. First records of A. tamaraw Freitag, 2013 from Luzon are reported.


Introduction
During the past decade, taxonomic surveys in major islands of the Philippine archipelago have raised the number of known spider riffle beetle species in the country from 10 in 2012 to 17 by 2022 [1][2][3]. The smaller-bodied Ancyronyx patrolus Freitag and Jäch, 2007 species group appears to be more speciose in the archipelago compared to the largerbodied Ancyronyx variegatus (Germar, 1824) species group. Members of the former tend to be regionally endemic. In fact, more than half of the known species in the Philippines are currently listed with single-island distributions [1].
The recent descriptions of new species from southern Philippines by Seno et al. [1] point to a distribution potentially spanning the entire archipelago and emphasize the presence of undiscovered diversity in the taxon. Major islands tend to harbor more than one species, which often occur syntopically [2,4]. This underscores the necessity for further taxonomic studies and the application of integrative approaches to expedite species discovery especially considering the continued decline in insect biodiversity.
An analysis of morphological and molecular data from existing collections led to the description of a new species, Ancyronyx jhoanae sp. nov., and new records for A. tamaraw Freitag, 2013 from Luzon Island, Philippines. This study constitutes the first published record of the Ancyronyx patrolus species group on the island.

Taxon Sampling
Samples were collected from the central lowlands of Luzon island, located in the northern region of the Philippines. The island is part of the Greater Luzon intra-biogeographic region, one among seventeen subregions suggested to harbor distinct sets of flora and fauna due to the geologic history of the archipelago [5]. The specimens were manually captured, either by handpicking from submerged substrates or by hand nets. Samples were subsequently stored in 95% ethanol. Based on the label, some older material was collected from submerged wood and stored dry for almost 20 years. Specimens used in this study A maximum likelihood (ML) tree with 1000 bootstrap replicates was generated using MEGA11 [11]. General time reversible (GTR + G + I) was identified through AICc as the best substitution model. Molecular species delimitation was implemented by employing three methods. First, the generated tree was used as an input for Poisson Tree Processes (PTP) [16] via an online portal (https://mptp.h-its.org/#/tree; accessed on 25 November 2022). Second, the COI sequence alignment was used to determine putative species clusters through a webserver (https://bioinfo.mnhn.fr/abi/public/asap/; accessed on 25 November 2022) that runs Assemble Species by Automatic Partitioning (ASAP) [17]. Third, pairwise intraand interspecific genetic divergences of sequences were computed through uncorrected pdistance in MEGA11 [11]. Putative species clusters were determined from the computation using a 3.00% threshold.
Etymology. The new species is named after Dr. Jhoana Garces of the Ateneo Biodiversity Research Laboratory to recognize her efforts as the collector of some of the specimens examined in this study and to honor her contributions to freshwater macroinvertebrate research in the Philippines.
Distribution. Ancyronyx jhoanae sp. nov. is currently only known to occur in Nueva Vizcaya and the Aurora province located in the midwestern portion of Luzon island, Philippines. Remarks. Individuals from the Subic Bay area (Bataan Peninsula) generally tend to have slightly larger anterior elytral patches than specimens from the type locality in Mindoro. In some specimens, the yellow anterior patches extend to the elytral suture.
Distribution. Ancyronyx tamaraw was previously only recorded from the island of Mindoro (Tamaraw Falls, Puerto Galera). Here it is reported to occur in the Subic Bay Freeport Zone (SBFZ) located in the Bataan Peninsula at the western edge of Luzon island, Philippines.

Discussion
This study provides a description of the first Ancyronyx species endemic to the island of Luzon ( Figure 5). Given previous observations in Sulawesi [6] and Mindanao [1], several species of this lineage appear to resemble each other externally, as observed here for A. jhoanae sp. nov. and A. berghaueri. Although the genus has been known for vivid coloration and species-specific markings, it appears to be not uncommon that similarity in color patterns render some species almost indistinguishable from each other in terms of external morphology. Molecular data suggest that the newly identified species is part of a lineage previously identified by Seno et al. [1]. This lineage encompasses species from Greater Mindoro, Greater Mindanao, and Sulawesi. Together with A. jhoanae sp. nov., these species constitute a subgroup genetically and geographically distinct from those of Greater Palawan where the namesake species and subgroup of the A. patrolus species group is known to occur [4]. Both clades appear to be separated by the Huxley Line ( Figure 5A), although a Sundaic origin for the A. patrolus subgroup is currently not evident due to the lack of related representatives in Borneo and other Sundaic islands.
In contrast, representatives of the A. minerva subgroup (sensu Freitag & Jäch [4]) occur on both sides of the Huxley Line in the Philippines ( Figure 5A). Ancyronyx minerva Freitag & Jäch, 2007 is known from Busuanga, Mindoro, and Palawan [4,8]. Now, the distribution area of the related A. tamaraw has also been extended and covers more than just one intra-Philippine biographic region [5]: Greater Mindoro and Greater Luzon ( Figure  5A). Presumed records from Bohol [18] still require confirmation by more detailed study.   Molecular data suggest that the newly identified species is part of a lineage previously identified by Seno et al. [1]. This lineage encompasses species from Greater Mindoro, Greater Mindanao, and Sulawesi. Together with A. jhoanae sp. nov., these species constitute a subgroup genetically and geographically distinct from those of Greater Palawan where the namesake species and subgroup of the A. patrolus species group is known to occur [4]. Both clades appear to be separated by the Huxley Line ( Figure 5A), although a Sundaic origin for the A. patrolus subgroup is currently not evident due to the lack of related representatives in Borneo and other Sundaic islands.
In contrast, representatives of the A. minerva subgroup (sensu Freitag & Jäch [4]) occur on both sides of the Huxley Line in the Philippines ( Figure 5A). Ancyronyx minerva Freitag & Jäch, 2007 is known from Busuanga, Mindoro, and Palawan [4,8]. Now, the distribution area of the related A. tamaraw has also been extended and covers more than just one intra-Philippine biographic region [5]: Greater Mindoro and Greater Luzon ( Figure 5A). Presumed records from Bohol [18] still require confirmation by more detailed study.