Comparative phylogeography of the plateau zokor (Eospalax baileyi) and its host-associated flea (Neopsylla paranoma) in the Qinghai-Tibet Plateau

Impacts of climate change and human activities on three Glires pests of the Qinghai-Tibet Plateau

BACKGROUND

The range of Glires is influenced by human activities and climate change. However, the extent to which human activities and environmental changes have contributed to this relationship remains unclear. We examined alterations in the distribution changes and driving factors of the Himalayan marmot, plateau pika, and plateau zokor on the Qinghai-Tibet Plateau (QTP) using the maximum entropy (MaxEnt) model and a geographical detector (Geodetector).

RESULTS

The MaxEnt model showed that the contribution rates of the human footprint index (HFI) to the distribution patterns of the three types of Glires were 46.70%, 58.70%, and 59.50%, respectively. The Geodetector results showed that the distribution pattern of the Himalayan marmot on the QTP was influenced by altitude and the normalized difference vegetation index (NDVI). The distribution patterns for plateau pikas and plateau zokors were driven by HFI and NDVI. Climate has played a substantial role in shaping suitable habitats for these three Glires on the QTP. Their suitable area is expected to decrease over the next 30-50 years, along with their niche breadth and overlap. Future suitable habitats for the three Glires tended to shift toward higher latitudes on the QTP.

CONCLUSION

These findings underscore the impacts of environmental and human factors on the distribution of the three Glires on the QTP. They have enhanced our understanding of the intricate relationships between Glires niches and environments. This can aid in identifying necessary interventions for developing effective early warning systems and prevention strategies to mitigate Glires infestations and plague epidemics on the QTP. © 2024 Society of Chemical Industry.

Captivity Shifts Gut Microbiota Communities in Plateau Zokor (Eospalax baileyi)

The gut microbiota in animals is a dynamic ecosystem influenced by both the host itself and the environment it inhabits. It is known that short-term captivity can significantly impact the gut microbiota of plateau zokors, leading to substantial inter-individual variation. However, the specific changes in the assembly process of the gut microbiota in plateau zokors during captivity remain unclear. In this study, we conducted a comparative analysis on the assembly process of the gut microbiota in 22 male plateau zokors from the same location in Qinglin Township, Datong County, Qinghai Province, before (W) and after (L) laboratory rearing. We performed a single-factor correlation network analysis on the top 50 genera with relative abundance in each group. The results revealed that captivity increased the complexity of the gut microbiota in plateau zokors, indicating a higher number of interactions between different microbial species. However, this increase in complexity was accompanied by a decrease in stability, suggesting a higher degree of variability and potential disruption in the microbial community. According to the results of the neutral community model, the gut microbiota of plateau zokors in the W had a higher Nm value (Nm = 48,135) compared to the L (Nm = 39,671), indicating that species dispersal of the gut microbiota was greater in the wild than in captivity. In the wild, the modified stochasticity ratio (MST) was less than 0.5, suggesting that deterministic processes dominated. However, after 15 days of laboratory rearing, the MST became greater than 0.5, indicating a shift toward stochastic processes, and this difference was highly significant (p < 0.001). This differs from research related to aboveground animals. This study provides theoretical support for the application of gut microbiota in subterranean endangered species.

Combination of nuclear and mitochondrial markers as a useful tool to identify Ctenophthalmus species and subspecies (Siphonaptera: Ctenophthalmidae)

Ctenophthalmus is considered the largest genus within the Order Siphonaptera. From a morphological point of view, only males of this genus can be identified at species and subspecies levels using morphological keys, whereas there are no morphological criteria in order to classify females at these taxonomical levels. Furthermore, the amount of available molecular and phylogenetic data for this genus is quite scarce so far. The main objective of this work was to assess the utility of the combination of nuclear and mitochondrial markers with respect to their ability to differentiate among different subspecies within the Ctenophthalmus genus. With this purpose, we carried out a comparative morphological and molecular study of three different subspecies (Ctenophthalmus baeticus arvernus, Ctenophthalmus nobilis dobyi, and Ctenophthalmus andorrensis catalaniensis) in order to clarify and discuss its taxonomic status. In addition, our study complemented the molecular data previously provided for Ctenophthalmus baeticus boisseauorum and Ctenophthalmus apertus allani subspecies. We sequenced five different molecular markers: EF1-α, ITS1, ITS2, cox1, and cytb. Our results confirmed that morphological data by themselves are not able to discriminate among Ctenophthalmus female taxa; however, the combination of the nuclear marker EF1-α together with mtDNA markers cytb and cox1 constituted a useful taxonomical and phylogenetic tool to solve this issue. Based on these results, we consider that the use of this molecular approach should be gradually used within Ctenophthalmus genus in order to complement its classical taxonomy and clarifying the complex taxonomy of other congeneric species of fleas.

New taxonomic and evolutionary insights relevant to the cat flea, Ctenocephalides felis: A geographic perspective

The cat flea, Ctenocephalides felis, is an obligate haematophagous ectoparasite of wildlife and domestic cats and dogs worldwide. Since cat fleas can affect the health of humans and their pets, an uncertain taxonomy of this taxon can greatly inhibit pest and disease management. To address the evolution and taxonomy of the cat flea, we set out to determine 1) how many genetically distinct taxa exist, 2) whether there is morphological support for the genetically distinct taxa, and 3) the role of host range and paleoclimatic events in speciation. We collected a total of 3352 fleas sampled from 576 domestic cats and dogs as well as 10 wildlife species across 30 localities in South Africa. A total of three flea genera, five species, and three of the currently recognized cat flea subspecies, C. f. damarensis, C. f. strongylus and C. f. felis were obtained. Geometric morphometric analyses on head shape were performed on 68 female and 107 male cat flea individuals. Principal component analysis demonstrated large overlap in head shape variation between C. f. strongylus and C. f. felis, rendering this character not useful for phylogenetic inferences. DNA was extracted from 188 Ctenocephalides spp. and mitochondrial COII and nuclear EF1-α sequences were generated. Bayesian and Maximum Likelihood analyses as well as a TCS parsimony haplotype network of the mitochondrial DNA confirmed the presence of three well supported monophyletic clades. These assemblages did not fully corroborate the existence of the three C. felis subspecies. A single well-supported molecular clade included only C. f. damarensis morphotypes that were mostly collected from wildlife. The recognition of this subspecies as a distinct taxon was further corroborated by sequence distances and also the number of plantar spiniform bristles on fore-tarsi V in males. Despite the overall lack of support for the recognition of C. f. damarensis and C. f. strongylus, a geographic trend was visible whereby one genetic lineage corresponded to the western dryer hot subregion, whereas the other was found throughout the region. Bayesian dating suggested that these two clades diverged during the early Pliocene (4.18 mya), a date that corresponds well with the establishment of a dry hot climate in the west of southern Africa. If so, the off-host environment, particularly temperature and humidity, are important factors to consider in the evolution of the cat flea. The present study rejects recent assertions that the three cat flea subspecies are valid entities and rather point to a situation where more sampling is required before the taxonomic status of C. f. damarensis can be resolved.

Phylogenetic heritability of geographic range size in haematophagous ectoparasites: time of divergence and variation among continents

To understand existence, patterns and mechanisms behind phylogenetic heritability in the geographic range size (GRS) of parasites, we measured phylogenetic signal (PS) in the sizes of both regional (within a region) and continental (within a continent) geographic ranges of fleas in five regions. We asked whether (a) GRS is phylogenetically heritable and (b) the manifestation of PS varies between regions. We also asked whether geographic variation in PS reflects the effects of the environment's spatiotemporal stability (e.g. glaciation disrupting geographic ranges) or is associated with time since divergence (accumulation differences among species over time). Support for the former hypothesis would be indicated by stronger PS in southern than in northern regions, whereas support for the latter hypothesis would be shown by stronger PS in regions with a large proportion of species belonging to the derived lineages than in regions with a large proportion of species belonging to the basal lineages. We detected significant PS in both regional and continental GRSs of fleas from Canada and in continental GRS of fleas from Mongolia. No PS was found in the GRS of fleas from Australia and Southern Africa. Venezuelan fleas demonstrated significant PS in regional GRS only. Local Indicators of Phylogenetic Association detected significant local positive autocorrelations of GRS in some clades even in regions in which PS has not been detected across the entire phylogeny. This was mainly characteristic of younger taxa.

Genetic structure and gene flow of the flea Xenopsylla cheopis in Madagascar and Mayotte

BACKGROUND

The flea Xenopsylla cheopis (Siphonaptera: Pulicidae) is a vector of plague. Despite this insect's medical importance, especially in Madagascar where plague is endemic, little is known about the organization of its natural populations. We undertook population genetic analyses (i) to determine the spatial genetic structure of X. cheopis in Madagascar and (ii) to determine the potential risk of plague introduction in the neighboring island of Mayotte.

RESULTS

We genotyped 205 fleas from 12 sites using nine microsatellite markers. Madagascan populations of X. cheopis differed, with the mean number of alleles per locus per population ranging from 1.78 to 4.44 and with moderate to high levels of genetic differentiation between populations. Three distinct genetic clusters were identified, with different geographical distributions but with some apparent gene flow between both islands and within Malagasy regions. The approximate Bayesian computation (ABC) used to test the predominant direction of flea dispersal implied a recent population introduction from Mayotte to Madagascar, which was estimated to have occurred between 1993 and 2012. The impact of this flea introduction in terms of plague transmission in Madagascar is unclear, but the low level of flea exchange between the two islands seems to keep Mayotte free of plague for now.

CONCLUSION

This study highlights the occurrence of genetic structure among populations of the flea vector of plague, X. cheopis, in Madagascar and suggests that a flea population from Mayotte has been introduced to Madagascar recently. As plague has not been reported in Mayotte, this introduction is unlikely to present a major concern for plague transmission. Nonetheless, evidence of connectivity among flea populations in the two islands indicates a possibility for dispersal by fleas in the opposite direction and thus a risk of plague introduction to Mayotte.

Analysis of the erythropoietin of a Tibetan Plateau schizothoracine fish (Gymnocypris dobula) reveals enhanced cytoprotection function in hypoxic environments

BACKGROUND

Erythropoietin (EPO) is a glycoprotein hormone that plays a principal regulatory role in erythropoiesis and initiates cell homeostatic responses to environmental challenges. The Qinghai-Tibet Plateau is a natural laboratory for hypoxia adaptation. Gymnocypris dobula is a highly specialized plateau schizothoracine fish that is restricted to > 4500 m high-altitude freshwater rivers and ponds in the Qinghai-Tibet Plateau. The role of EPO in the adaptation of schizothoracine fish to hypoxia is unknown.

RESULTS

The EPO and EPO receptor genes from G. dobula and four other schizothoracine fish from various altitudinal habitats were characterized. Schizothoracine EPOs are predicted to possess 2-3 N-glycosylation (NGS) sites, 4-5 casein kinase II phosphorylation (CK2) sites, 1-2 protein kinase C (PKC) phosphorylation sites, and four conserved cysteine residues within four helical domains, with variations in the numbers of NGS and CK2 sites in G. dobula. PAML analysis indicated a d N/d S value (ω) = 1.112 in the G. dobula lineage, and a few amino acids potentially under lineage-specific positive selection were detected within the G. dobula EPO. Similarly, EPO receptors of the two high-altitude schizothoracines (G. dobula and Ptychobarbus kaznakovi), were found to be statistically on the border of positive selection using the branch-site model (P-value = 0.096), and some amino acids located in the ligand-binding domain and the fibronectin type III domain were identified as potentially positive selection sites. Tissue EPO expression profiling based on transcriptome sequencing of three schizothoracines (G. dobula, Schizothorax nukiangensis Tsao, and Schizothorax prenanti) showed significant upregulation of EPO expression in the brain and less significantly in the gill of G. dobula. The elevated expression together with the rapid evolution of the EPO gene in G. dobula suggested a possible role for EPO in adaptation to hypoxia. To test this hypothesis, Gd-EPO and Sp-EPO were cloned into an expression vector and transfected into the cultured cell line 293 T. Significantly higher cell viability was observed in cells transfected with Gd-EPO than cells harboring Sp-EPO when challenged by hypoxia.

CONCLUSION

The deduced EPO proteins of the schizothoracine fish contain characteristic structures and important domains similar to EPOs from other taxa. The presence of potentially positive selection sites in both EPO and EPOR in G. dobula suggest possible adaptive evolution in the ligand-receptor binding activity of the EPO signaling cascade in G. dobula. Functional study indicated that the EPO from high-altitude schizothoracine species demonstrated features of hypoxic adaptation by reducing toxic effects or improving cell survival when expressed in cultured cells, providing evidence of molecular adaptation to hypoxic conditions in the Qinghai-Tibet Plateau.

Comparative phylogeography of the plateau zokor (Eospalax baileyi) and its host-associated flea (Neopsylla paranoma) in the Qinghai-Tibet Plateau

Background

Specific host-parasite systems often embody a particular co-distribution phenomenon, in which the parasite’s phylogeographic pattern is dependent on its host. In practice, however, both congruent and incongruent phylogeographic patterns between the host and the parasite have been reported. Here, we compared the population genetics of the plateau zokor (Eospalax baileyi), a subterranean rodent, and its host-associated flea species, Neopsylla paranoma, with an aim to determine whether the two animals share a similar phylogeographic pattern.

Results

We sampled 130 host-parasite pairs from 17 localities in the Qinghai-Tibet Plateau (QTP), China, and sequenced a mitochondrial DNA (mtDNA) segment (~2,500 bp), including the complete COI and COII genes. We also detected 55 zokor and 75 flea haplotypes. AMOVA showed that the percentage of variation among the populations of zokors constituted 97.10%, while the within population variation was only 2.90%; for fleas, the values were 85.68% and 14.32%, respectively. Moreover, the flea Fst (fixation index) values were significantly smaller than in zokor. Although the Fst values between zokors and fleas were significantly and positively correlated (N =105, R =0.439, p =0.000), only a small amount (R²= 0.19) of the flea Fst variations could be explained by the zokor Fst variations. The two animals showed very distinct haplotype network structures from each other while co-phylogenetic analyses were unable to reject the hypothesis of an independence of speciation events.

Conclusions

Zokors and fleas have very distinct population genetic patterns from each other, likely due to the influence of other sympatrically-distributed vertebrates on the transmission of fleas.