Vicariance ofPyrocoeliafireflies (Coleoptera: Lampyridae) in the Ryukyu islands, Japan

Function of snail shell hairs in anti-predator defense

The function and evolutionary background of the hairs on the shells of terrestrial gastropods is largely unknown. Many hypotheses proposed by malacologists have never been proven, and the long-held hypothesis of mechanical stability in wet environments has been rejected by recent studies. It would therefore be worthwhile to reexamine other hypotheses regarding the adaptive significance of shell hairs. We investigated the defense function of shell hairs against a specialist predator, the snail-eating firefly, in the long-haired snail Moellendorffia diminuta. The firefly larvae, which hunt snails using abdominal suckers, were unable to attach to the shell because of the shell hairs but were able to attach to the shells that had lost their hairs. About half of the hairy snails successfully defended themselves by swinging their shells and dropping firefly larvae, but most of the snails without hair failed to defend. The hairs reduce the ability of the larva to attach to the shell and increase the effectiveness of the shell-swinging defense behavior in removing the larva from the shell. As shell hairs grow longer with shell development, they may confer an advantage based on the predator's growth stage. Our findings highlight the anti-predator defense role of shell hairs in land snails, introducing a hypothesis previously overlooked in the evolutionary context of hairy snails.

Geologically calibrated mammalian tree and its correlation with global events, including the emergence of humans

A robust timetree for Mammalia was constructed using the time calibration function of BEAST v1.10.4 and MEGA 11. The analysis involved the application of times of the most recent common ancestors, including a total of 19 mammalian fossil calibration ages following Benton et al. (Palaeontologia Electronica, 2015, 1-106) for their minimum ages. Additionally, fossil calibration ages for Gorilla, Pan, and a geologic event calibration age for otters were incorporated. Using these calibration ages, I constructed a geologically calibrated tree that estimates the age of the Homo and Pan splitting to be 5.69 Ma. The tree carries several significant implications. First, after the initial rifting at 120 Ma, the Atlantic Ocean expanded by over 500 km around Chron 34 (84 Ma), and vicariant speciation between Afrotheria (Africa) and Xenarthra (South America) appears to have commenced around 70 Ma. Additionally, ordinal level differentiations began immediately following the K-Pg boundary (66.0 Ma), supporting previous hypothesis that mammalian radiation rapidly filled ecological niches left vacant by non-avian dinosaurs. I constructed a diagram depicting the relationship between base substitution rate and age using an additional function in BEAST v1.10.4. The diagram reveals an exponential increase in the base substitution rate approaching recent times. This increased base substitution rate during the Neogene period may have contributed to the expansion of biodiversity, including the extensive adaptive radiation that led to the evolution of Homo sapiens. One significant driving factor behind this radiation could be attributed to the emergence and proliferation of C4 grasses since 20 Ma. These grasses have played a role in increasing carbon fixation, reducing atmospheric CO2 concentration, inducing global cooling, and initiating Quaternary glacial-interglacial cycles, thereby causing significant climatic changes.

Luminescent characteristics and mitochondrial COI barcodes of nine cohabitated Taiwanese fireflies

Background

Over 50 Taiwanese firefly species have been discovered, but scientists lack information regarding most of their genetics, bioluminescent features, and cohabitating phenomena. In this study, we focus on morphological species identification and phylogeny reconstructed by COI barcoding, as well as luminescent characteristics of cohabited Taiwanese firefly species to determine the key factors that influenced how distinct bioluminescent species evolved to coexist and proliferate within the same habitat.

Methods

In this study, 366 specimens from nine species were collected in northern Taiwan from April to August, 2016-2019. First, the species and sex of the specimens were morphologically and genetically identified. Then, their luminescent spectra and intensities were recorded using a spectrometer and a power meter, respectively. The habitat temperature, relative humidity, and environmental light intensity were also measured. The cytochrome oxidase I (COI) gene sequence was used as a DNA barcode to reveal the phylogenetic relationships of cohabitated species.

Results

Nine species-eight adult species (Abscondita chinensis, Abscondita cerata, Aquatica ficta, Luciola curtithorax, Luciola kagiana, Luciola filiformis, Curtos sauteri, and Curtos costipennis) and one larval Pyrocoelia praetexta-were morphologically identified. The nine species could be found in April-August. Six of the eight adult species shared an overlap occurrence period in May. Luminescent spectra analysis revealed that the λ _max of studied species ranged from 552-572 nm (yellow-green to orange-yellow). The average luminescent intensity range of these species was about 1.2-14 lux (182.1-2,048 nW/cm²) for males and 0.8-5.8 lux (122.8-850 nW/cm²) for females, and the maximum luminescent intensity of males was 1.01-7.26-fold higher than that of females. Compared with previous studies, this study demonstrates that different λ _max, species-specific flash patterns, microhabitat choices, nocturnal activity time, and/or an isolated mating season are key factors that may lead to the species-specific courtship of cohabitated fireflies. Moreover, we estimated that the fireflies start flashing or flying when the environmental light intensity decreased to 6.49-28.1 lux. Thus, based on a rough theoretical calculation, the sensing distance between male and female fireflies might be 1.8-2.7 m apart in the dark. In addition, the mitochondrial COI barcode identified species with high resolution and suggested that most of the studied species have been placed correctly with congeners in previous phylogenies. Several cryptic species were revealed by the COI barcode with 3.27%-12.3% variation. This study renews the idea that fireflies' luminescence color originated from the green color of a Lampyridae ancestor, then red-shifted to yellow-green in Luciolinae, and further changed to orange-yellow color in some derived species.

Physiological Responses of the Firefly Pyrocoelia analis (Coleoptera: Lampyridae) to an Environmental Residue From Chemical Pesticide Imidacloprid

Imidacloprid, a neonicotinoid insecticide, is widely applied to control insect pests across a broad spectrum. Though the impact of residues from this chemical pesticide on non-target organisms in the field has been reported, it was not well characterized across a wide range of ecosystems, especially for some species considered as environmental indicators that live in forests. The effects of sublethal dose of imidacloprid on firefly, Pyrocoelia analis, were analyzed physiologically and biochemically in this study to better understand the impact of chemical pesticide application on environmental indicators such as fireflies. After imidacloprid treatment, the midgut tissues of the larva presented an abnormal morphology featured as atrophy of fat body cells, shrinking cells, and the destruction of a midgut structure. The activities of antioxidant enzymes, superoxide dismutase, catalase, and peroxidase were noticeably increased during early exposure to sublethal imidacloprid and then decreased at later stages. The malondialdehyde content significantly increased after 12 h of exposure to imidacloprid compared with the control. Similarly, the enzyme activities of polyphenol oxidase and acetylcholinesterase were increased after the imidacloprid treatment and then decreased at the later stage. In summary, a sublethal dose of imidacloprid caused destructive change in the tissue structure, and this damage was followed by an excessive reactive oxygen species that could not be eliminated by antioxidant enzymes. Our results indicated that the residues of imidacloprid might cause severe toxicity to non-target insects in the environment even far away from the agro-ecosystem where the chemicals were applied.

Quaternary Vicariance of Lotic Coeliccia in the Ryukyu-Taiwan Islands Contrasted with Lentic Copera

Lotic dragonflies and damselflies are expected to be more affected by vicariance than lentic sister species. We demonstrated that severe vicariant speciation acted on lotic Coeliccia in contrast to lentic Copera damselflies, which are both included in the family Platycnemididae. We constructed maximum likelihood and Bayesian inference trees of these Platycnemididae species from the continental islands of Ryukyu (Amami, Okinawa, and Yaeyama islands), Taiwan, and Japan relative to Chinese species using raxmlGUI and BEAST, based on the mitochondrial COI gene (682 bp), COII gene (494 bp), 16SrRNA (478 bp), and the nuclear 28SrRNA gene (807 bp). In BEAUti, we calibrated the splitting age of the MRCA of all the Coeliccia species as 1.55-0.15 million years ago (Ma), a date that corresponds to a geologic constraint: the Okinawa trough and associated straits, including the Yilan basin in Taiwan, began to rift at 1.55 Ma, isolating the Ryukyu-Taiwan islands from the Chinese continent. The vicariance split Coeliccia into the Ryukyu-side clade of Coeliccia ryukyuensis (Coe. r. ryukyuensis in Okinawa and Coe. r. amamii in Amami) and Coeliccia flavicauda (Coe. f. masakii in Yaeyama and Coe. f. flavicauda in southern Taiwan), and the Chinese-side clade of Coeliccia cyanomelas (northern Taiwan and China), separated by the Okinawa trough. These Coeliccia species were further deeply differentiated to form local populations on the major islands and some of the minor islands. The Copera clade constituted a sister of the lotic Coeliccia clade, but genetic differentiation was not recognizable in lentic Copera between China, Taiwan, and Japan. Base substitution rates applying a strict clock model were estimated for COI: 0.0783, COII: 0.0803, 18SrRNA: 0.0186, 28SrRNA: 0.00577, and combined: 0.0408 substitutions/site/myr, and these rates are relatively high.