Trombiculid mites (Acariformes) are unique among arthropods of medical importance in that only the larval instar (chigger) is parasitic, which can result in the transmission of zoonotic scrub typhus. The use of molecular approaches for chigger species discrimination has been very limited until recently, especially for those parasitizing bird hosts, where data remain scarce. Here, we aimed to generate DNA barcodes of chiggers parasitizing birds in Malaysia based on the mitochondrial cytochrome c oxidase subunit I (COI) gene following DNA extraction, PCR and sequencing. Fifty-four COI sequences from 8 bird-associated chigger species in Malaysia were combined with 50 GenBank sequences comprising 7 genera from various countries for DNA barcode and phylogenetic analysis. The correct identification rates for the 95 COI barcodes were 96.84% (Best Match) and 86.31% (Best-Close Match). DNA barcode analyses effectively clustered the 8 nominal species from this study into their respective genera. Genetic divergence of less than 3% was observed within Ascoschoengastia lorius, Neoschoengastia gallinarum, Parascoschoengastia heynemani, Leptotrombidium imphalum, and Blankaartia acuscutellaris, all of which formed a monophyletic clade, confirming their conspecific nature. Conversely, intraspecific divergences of 17.64%, 15.49%, and 11.63% were obtained for Toritrombicula densipiliata, Odontacarus audyi, and Leptotrombidium deliense. These divergences, supported by evidence of distinct entities through delimitation analyses, indicate potential cryptic diversity within these populations. In conclusion, this study represents the first molecular genetic analysis of bird chiggers in Malaysia, revealing varying levels of genetic divergence. Our findings highlight the utility of DNA barcoding for understanding chigger diversity and aiding in accurate identification.

Chigger mites were collected from 65 bird species in different regions of Thailand and Malaysia. In total, 21 species were recorded. The previously unknown fauna of chiggers parasitizing shorebirds of Thailand included one new species, Neacariscus (Whartonacarus) andamanensis n. sp. as well as Neacariscus (Neacariscus) pluvius (Wharton, 1945) previously recorded only in Oceania; Neacariscus (Whartonacarus) shiraii (Sasa, Kano and Obata, 1952) (known from Oceania and Japan); and Neacariscus (Whartonacarus) sulae (Oudemans, 1910) and Schoengastia archaea (Taufflieb, 1960), both described from West Africa. Toritrombicula kirhocephales Goff, 1982 described from Papua New Guinea was for the first time recorded in Asia (Thailand). Neoschoengastia gallinarum (Hatori, 1920) and Helenicula comata (Womersley, 1952) were for the first time recorded in Thailand. Ascoschoengastia lorius (Gunther, 1939) was for the first time recorded in Malaysia. Finally, Ericotrombidium cosmetopode (Vercammen-Grandjean and Langston, 1971) described from free larvae, was for the first time recorded on a host (bird Pellorneum ruficeps Swainson); and Leptotrombidium miculum (Traub and Audy, 1954) was for the first time recorded on a bird host. New host species were recorded for a large part of the collected chigger species.

Neoschoengastia gallinarum is widely distributed in Asia, preferentially parasitising birds, and heavy infestations have clinical impacts on domestic fowl. In common with other trombiculid mites, the genetic diversity and potential variation in host preferences or pathology induced by N. gallinarum are poorly understood. This study aimed to unravel the geographical variation and population structure of N. gallinarum collected from galliform birds in Peninsular Malaysia and Thailand by inference from concatenated mitochondrial-encoded cytochrome c oxidase subunit I (COI), and nuclear-encoded internal transcribed spacer 2 (ITS2) and 18S ribosomal DNA gene sequences, including a comparison with previously published data from southeastern China. Our multi-locus sequence analysis revealed three monophyletic clades comprising (A) specimens from Peninsular Malaysia, (B) the samples from Thailand together with a minority of Chinese sequences, and (C) the majority of sequences from China. Similarly, most species delimitation approaches divided the specimens into three operational taxonomic units. Analysis of molecular variance revealed 96.41% genetic divergence between Malaysian and Thai populations, further supported by the absence of gene flow (Nm = 0.01). In conclusion, despite the two countries sharing a land border, populations of N. gallinarum from Peninsular Malaysia and Thailand appear to be genetically segregated and may represent distinct cryptic species.

Chiggers (Acariformes: Trombiculidae) are ectoparasites of small mammals and important vectors of scrub typhus, yet their taxonomy and molecular diversity in Southeast Asia remain poorly resolved. This study represents the first DNA barcoding and phylogenetic assessment of chiggers from small mammals across Peninsular Malaysia, integrating mitochondrial (COI) and nuclear (28 S rDNA) genes. A total of 192 chiggers representing 11 morphospecies from six genera were sequenced, with tree topologies inferred using maximum likelihood and supported by multiple species delimitation methods. The COI gene discriminated five species as monophyletic, while analysis of the 28 S rDNA gene clarified phylogenetic relationships within Walchia and Leptotrombidium. Discordance between morphological and molecular boundaries in several taxa, particularly Gahrliepia fletcheri, Leptotrombidium deliense, and Walchiella oudemansi, suggests the existence of cryptic lineages and potential regional diversification. Importantly, this study provides the first molecular records for eight species, including the only barcodes from the genera Gahrliepia and Walchiella worldwide. These findings provide important resources for the molecular identification of Southeast Asian chiggers and underscore the need for integrative approaches combining morphology, molecular data, and biogeography to resolve complex species boundaries and improve vector surveillance for mite-borne diseases.

This study presents the first confirmed records of Mops johorensis (Dobson, 1873) (Chiroptera, Molossidae) from Borneo. Specimens were recorded at three sites: Sabah (Sungai Kangkawat, 50 m a.s.l) and Sarawak (Lubok Antu, 30 m a.s.l and Mount Penrissen, 1200 m a.s.l). Echolocation analysis revealed site-based variation in call frequencies. Morphological comparisons showed subtle differences between Bornean and Peninsular populations. Genetic analysis using the mitochondrial COI gene showed minimal divergence between Bornean and Peninsular individuals. Spatial modelling identified hotspots for Molos-sidae in northern Sabah and central Sarawak, with habitat suitability strongly influenced by bat and cave density, climate, and land use.