Diversity and evolutionary ecology of the Rhaphidophoridae of Taiwan

Abstract

Cave crickets (Orthoptera: Rhaphidophoridae) are a wingless insect group that plays important ecological roles in cave and forest-floor ecosystems, particularly in seed dispersal and nutrient cycling (Figure 1). Recent morphological and molecular studies have revealed remarkable regional diversification and a complex evolutionary history of this family, especially across East Asia and adjacent island systems. However, taxonomic studies on Taiwanese Rhaphidophoridae remain extremely limited, and many early species descriptions lack sufficient diagnostic information for reliable identification. This project aims to systematically document the species diversity and taxonomic status of Taiwanese Rhaphidophoridae and to investigate their phylogenetic relationships and biogeographic history. Extensive field surveys will be conducted throughout Taiwan and its offshore islands to establish representative voucher specimens and DNA reference collections. Targeted sampling will also be carried out at or near historical type localities, accompanied by detailed morphological re-examination of previously described species. Molecular phylogenetic analyses will be performed using mitochondrial and nuclear gene markers to reconstruct evolutionary relationships and delimit species boundaries. Preliminary results indicate that, in addition to the currently recorded taxa, Taiwan harbors several previously unrecorded genera and multiple undescribed species. This study is expected to establish the first comprehensive taxonomic framework for Taiwanese Rhaphidophoridae, provide formal descriptions of new species and taxonomic revisions, clarify the evolutionary diversification of East Asian islands lineages, and generate fundamental data for biodiversity conservation, cave ecosystem research, and long-term ecological monitoring.

Keywords: Integrative taxonomy; Biogeography; Molecular phylogenetics; Cave ecosystems; Orthoptera

Methodology and Implementation Steps

This study will first compile and review the taxonomic literature and museum collections of Taiwanese Rhaphidophoridae. Historical taxonomic records will be re-evaluated, and the type specimen of Rhaphidophora taiwana preserved in the National Taiwan University Insect Museum has already been examined as a reference for subsequent taxonomic comparisons. Comprehensive field surveys will then be conducted throughout Taiwan and its offshore islands, covering diverse geographic regions and elevational gradients. One to ten individuals will be collected from each locality. Specimens will be preserved in 95% ethanol for DNA extraction, while corresponding voucher specimens will be prepared as dried museum specimens for morphological examination.

Morphological analyses will follow recent taxonomic studies on East Asian Rhaphidophoridae. Standard measurements, including body length, pronotum length, hind femur length, hind tibia length, and ovipositor length, will be recorded. Additional characters with potential taxonomic significance, such as the lengths of the paired movable spines at the apex of the mid femur, the length of the first hind tarsomere, and the numbers of movable spines on the fore and mid tibiae, will also be documented to refine diagnostic characters for each taxon.

Molecular analyses will generate DNA sequence data from mitochondrial genes (COI, 16S, and 12S) and nuclear genes (18S and 28S). Phylogenetic relationships will be reconstructed by integrating molecular and morphological evidence, and genetic distances will be analyzed to evaluate species boundaries. Using Neotachycines as a model group, this study will further investigate the evolutionary relationships and biogeographic history between Taiwanese and Ryukyu populations, providing a robust framework for taxonomic revision and biodiversity research on Taiwanese Rhaphidophoridae.

Innovation and Cross-Disciplinary Collaboration

This project represents the first integrative taxonomic study focusing on Taiwanese Rhaphidophoridae by combining morphology, molecular evidence, and biogeographic analyses to establish a comprehensive taxonomic framework. In addition to re-examining type specimens and historical taxonomic literature, this study collaborates with the Osaka Museum of Natural History, Japan, to examine type materials of Japanese taxa, assist in specimen digitization, and evaluate previously overlooked diagnostic characters(Figure 6). Through international collaboration and the integration of taxonomy, molecular phylogenetics, and biodiversity research, this project aims to clarify the taxonomic status and evolutionary relationships of Taiwanese and Japanese cave crickets within the East Asian region.

Expected Results and Contributions

This project is expected to establish the first comprehensive taxonomic framework for Taiwanese Rhaphidophoridae by documenting newly recorded genera and describing previously unknown species. An integrated reference database consisting of voucher specimens, morphological information, and DNA sequence data will be established to support future taxonomic and evolutionary studies. Phylogenetic and biogeographic analyses will clarify the evolutionary relationships among Taiwanese and East Asian islands lineages, providing new insights into species diversification across island systems. The results are expected to be published in international peer-reviewed journals and will provide essential baseline information for biodiversity inventories, environmental impact assessments, and conservation planning in Taiwan. Furthermore, this study will improve our understanding of cave and forest ecosystem functioning, promote public awareness of cave biodiversity, and enhance Taiwan's international visibility in the taxonomy, systematics, and evolutionary research of Rhaphidophoridae.