Dynamics behind disjunct distribution, hotspot-edge refugia, and discordant RADseq/mtDNA variability: insights from the Emei mustache toad

Synergistic effects of Pleistocene geological and climatic events on complex phylogeographic history of widespread sympatric species of Megaloptera in East Asia

Unraveling the phylogeographic histories of species remains a key endeavor for comprehending the evolutionary processes contributing to the rich biodiversity and high endemism found in East Asia. In this study, we explored the phylogeographic patterns and demographic histories of three endemic fishfly and dobsonfly species ( Neochauliodes formosanus, Protohermes costalis, and Neoneuromus orientalis) belonging to the holometabolan order Megaloptera. These species, which share a broad and largely overlapping distribution, were analyzed using comprehensive mitogenomic data. Our findings revealed a consistent influence of vicariance on the population isolation of Neoc. formosanus and P. costalis between Hainan, Taiwan, and the East Asian mainland during the early Pleistocene, potentially hindering subsequent colonization of the later diverged Neon. orientalis to these islands. Additionally, we unveiled the dual function of the major mountain ranges in East Asia, serving both as barriers and conduits, in shaping the population structure of all three species. Notably, we demonstrated that these co-distributed species originated from Southwest, Southern, and eastern Central China, respectively, then subsequently migrated along multi-directional routes, leading to their sympatric distribution on the East Asian mainland. Furthermore, our results highlighted the significance of Pleistocene land bridges along the eastern coast of East Asia in facilitating the dispersal of mountain-dwelling insects with low dispersal ability. Overall, this study provides novel insight into the synergistic impact of Pleistocene geological and climatic events in shaping the diversity and distribution of aquatic insects in East Asia.

Male spiny frogs enter the underwater battlefield with loose skin exhibiting enhanced penetration of capillaries into the epidermis

The skin has multiple functions, and capillaries can penetrate the epidermis to shorten the diffusion path while allowing maintenance of overall epidermal thickness for nonrespiratory roles. However, a method for quantifying the capillary penetration extent is lacking. Such a method may facilitate making comparisons and detecting associations, potentially making the extent a useful variable in biological studies. We quantified the extent as the ratio of the average minimum thickness of epidermis overlying each capillary to the average epidermal thickness along a skin section and then explored its performance in the Emei mustache toad, Leptobrachium boringii, a species in which breeding males with loose skin call and fight each other with maxillary spines underwater. The ratio showed informative associations with other variables, such as perfused capillary density. It displayed small intragroup variation and could be more sensitive than other variables in revealing structural differences in the skin. The ratio estimates were lowest and were correlated with epidermal and stratum compactum thicknesses in breeding males, i.e., a covariation but not reinforcement against stabbing, constituting early evidence consistent with the increased extensibility of loose skin conferring a defensive advantage during combat in amphibians. In addition, our results lead to the hypothesis that high hemoglobin density along subepidermal capillaries favors the maintenance of low blood partial oxygen pressure and hence increases cutaneous oxygen uptake. We also provide evidence supporting the new idea that the cooccurrence of loose skin and underwater calling found in some frogs can be explained by the latter benefiting from a large functional respiratory surface area. Awareness of the usefulness of the ratio may promote its application and the quantification of the penetration. Regarding exchange surface design, these findings for L. boringii imply a case in which looseness increases surface area as well as prevents damage.

A simple PCR-RFLP method for identification and detection of medicinal toad and its crude drug even with serious degradation of DNA

The secretions of the venom glands, dry skin and whole body of several Bufo species have been used as traditional medicines in East Asia to treat heart failure and cancer. Due to the highly similar morphological features of Bufo species and their derived commercial crude drugs, along with the high similarity of chemical composition of the secretions of venom glands, it is very challenging to identify the medicinal toads and the related crude drugs. The cyt-b sequences provide useful information to authenticate medicinal Bufo species. Based on the cyt-b sequences, a simple PCR-RFLP method was established for the identification of the medicinally used Bufo species as well as their derived crude drugs. The 23 specimens from three medicinally used Bufo species, B. bufo gargarizans (Bbg), B. melanostictus (Bm) and B. raddei (Br), were clearly divided into 3 groups according to the sequences of amplified cyt-b regions, which could be digested by specific restriction enzymes NcoI, EcoRV and BstXI, respectively. Then the specific PCR-RFLP method was further used to identify 9 samples of commercial crude drugs even with serious degradation of DNA, and all nine samples were identified as B. bufo gargarizans. The method is suitable for identification of medicinally used Bufo species and the related crude drugs.