BMC ecology and evolution最新文献

Background: The Russian desman (Desmana moschata) is a critically endangered, elusive semi-aquatic mammal. While understanding its historical population dynamics is crucial for conservation, genomic data on its evolutionary and demographic history remain scarce.

Results: Here, we present a comprehensive whole-genome phylogenetic analysis of Desmana moschata within the Talpidae family, including heterozygosity assessments and inferred population size changes, as determined by PSMC and MSMC analyses. Our results demonstrate that, similar to its closest relative the Pyrenean desman (Galemys pyrenaicus), this species has undergone a long-term population decline preceding significant human influence. The phylogenetic component of our study involved a multigene analysis based on over 2,000 exons, producing a well-resolved, dated phylogeny of the Talpidae family at the tribal level.

Conclusions: Although anthropogenic factors have undoubtedly contributed to recent declines, our data reveal that the reduction in the desman population is primarily an ancient process driven by natural causes. This has resulted in persistent declines in both effective population size and geographic range and then subsequent evolutionary extinction of ancient taxa with limited adaptive capabilities. These findings lay the groundwork for future genomic conservation studies, incorporating expanded sampling and targeted investigation of specific genomic features.

Background: The phylogenetic relationships of fossil birds near the origin of the avian crown group remain debated, in part due to a limited amount of character evidence from incomplete fossils. The avian lower jaw provides a potentially rich source of additional character data, yet fusion of the individual bony elements composing the avian post-dentary complex has impeded efforts to explore its phylogenetic signal. Here, we use high-resolution µCT-scanning to separate the individual bony elements of the mandibles of several immature crown birds and key fossil taxa, and use those data to assess support for alternative phylogenetic hypotheses for fossils near the origin of crown birds.

Results: We find that evidence from Asteriornis fails to support interpretations of derived mandibular similarities with palaeognaths, and instead strongly favours galloanseran, and specifically galliform, affinities. Our results also illustrate striking similarities in the architecture of the lower jaws between the toothed ornithurine Ichthyornis, Pelagornithidae and Vegavis, which, in addition to the absence of derived features linking them to Galloanserae, highlights questions regarding the phylogenetic position of these perennially controversial taxa.

Conclusions: Our data reveal new insight into patterns of morphological evolution near the origin of the avian crown group while raising new phylogenetic questions, emphasising the potential untapped value of detailed comparative investigations of morphological complexes such as the post-dentary complex of the mandible for informing the early evolutionary history of crown birds.

Background: Permineralized fossil wood is frequently found in the Jurassic deposits of China. Many studies of fossil stems are based on anatomical descriptions, yet phylogenetic analyses could provide important insights for systematics studies of fossil wood.

Results: Here, we conducted a phylogenetic analysis of four fossil stems from Yiwu Jurassic Forest to elucidate their systematic relationships with extant gymnosperms. Phylogenetic trees were constructed using data from two nucleotide regions (trnK-matK, rbcL) and xylological characters of six extant gymnosperms. Tree Analysis Using New Technology under maximum parsimony revealed that the four fossil stems were basal to the Araucariaceae in the dataset that combined genetic and xylological characters.

Conclusions: Our findings indicate that phylogenetic analysis combined with characterizations of wood anatomical characters are effective for taxonomic investigations of fossil wood from Yiwu Jurassic Forest.

Background: The microbial community within the gastrointestinal tract, known as the gut microbiome (GMB), is a complex micro-ecosystem that is modulated by the life history and physiological traits of the host as well as environmental conditions experienced by the host. In addition, phylogeny can be an important driver of GMB variability across mammalian species, with closely-related species sharing more similar microbial communities than distantly-related species, an eco-evolutionary pattern known as phylosymbiosis. In this study, we examined GMB diversity across 11 species of large herbivores in Etosha National Park (ENP), Namibia, to determine whether host species exhibit phylosymbiosis and whether different herbivore families host distinct microbial communities. The large herbivore community of ENP is an excellent model system because the herbivore species represent distinct evolutionary lineages and have evolved a variety of gut morphologies, dietary niches, and habitat requirements, all of which shape gut microbial diversity.

Results: While we found no evidence of phylosymbiosis across the greater ENP herbivore community, phylosymbiosis was detected among bovid species based on a positive correlation between microbial relative abundance and host evolutionary divergence times. Our results also revealed distinct microbial membership (e.g., Bacteroides, Treponema, and Alistipes) that distinguished bovid species from elephants and giraffes.

Conclusions: Our study provides new insights into the impact of phylogeny on GMB diversity in a closely-related African herbivore community. In particular, phylosymbiosis patterns observed in bovids but not all herbivore species demonstrates that microbial communities are dynamic and respond to a mixture of host evolutionary strategies and corresponding adaptations.

Background: The terrestrial ribbon worm Geonemertes pelaensis Semper, 1863 (phylum Nemertea) is widely reported from tropical regions worldwide. In Japan, this species has been recorded from subtropical islands including the Ogasawara Islands, a UNESCO World Heritage Site south of Tokyo recognized for its unique biodiversity, where it has been implicated in the decline of native soil invertebrates. Here, we demonstrate that the nemerteans in the Ogasawara Islands are genetically and morphologically distinct from those found on Yonaguni Island (Okinawa, Japan), indicating the presence of at least two separate species in Japan.

Results: We sequenced the complete mitochondrial genomes of both populations (18,755 bp for Ogasawara; 31,745 bp for Yonaguni), revealing substantial differences in genome size and gene arrangement. The mitochondrial genome of the Yonaguni population is unusually large, exceeding typical sizes reported for metazoans. Uncorrected p-distances in cytochrome c oxidase subunit I (COX1) sequences between the two populations ranged from 6.75 to 8.59%, which is above the widely used threshold for intraspecific variation in nemerteans. Morphological comparisons also support species-level distinction: live specimens from Yonaguni have a pale body with a prominent mid-dorsal stripe (body width-to-stripe ratio: 1:0.078-0.110), whereas individuals from Ogasawara are pale to light brown with a narrower and fading stripe (ratio: 1:0.042-0.050). Moreover, accessory-stylet pouches differ between populations: Yonaguni specimens possess four to five pouches, each containing 3-5 stylets, while Ogasawara specimens have two pouches, each with two stylets. Examination of museum specimens collected in the 1980s from Chichijima showed the extremely similar external morphology as our recent Ogasawara specimens, indicating that this form has been the only Geonemertes species in the Ogasawara Islands for nearly half a century.

Conclusions: Our results indicate the presence of species-level diversity in Japanese terrestrial nemerteans and demonstrate that accurate species identification using molecular barcodes is essential in insular ecosystems. Recognizing cryptic or pseudocryptic lineages is critical for effective biodiversity monitoring and for preventing mismanagement in ecologically sensitive regions such as the Ogasawara Islands.