BMC ecology and evolution最新文献

Background: Sea cucumbers are a highly diverse, enigmatic, ecologically and economically important group of echinoderms, however understanding of their taxonomy is complicated by cryptic morphology, hidden diversity and the presence of species complexes. The sandfish Holothuria (Metriatyla) scabra, is a high-value tropical sea cucumber exploited in multispecies fisheries across the Indo-Pacific with historically chaotic taxonomy, that has never been examined using molecular information. To evaluate its taxonomic identity, a phylogeographic approach was used to examine evolutionary relationships at 9 sites (n = 98) across the ~ 16,500 Km Indo-Pacific species distribution. Two genome-wide (1,500 PAV and 2,000 SNP) loci and one mitochondrial marker (cox1: 69 sequences) were employed in phylogenetic reconstructions, estimations of genetic distance, and assessments of species boundaries and evolutionary history.

Results: Both genome-wide and cox1 data indicate sandfish constitute a species complex containing a minimum of 7 operational taxonomic units (OTUs), with inter-ocean divergence patterns supporting non-conspecifity of Indian and Pacific Ocean specimens. Six OTUs were resolved in the Pacific Ocean across 3 broad lineages corresponding to putative subspecies, along with one OTU in the Indian Ocean. Analyses of evolutionary history estimate divergence of H. (Metriatyla) scabra in the early Pliocene ~ 4.36 MYa (95% HPD 3.3-5.42 MYa), from a germinate point likely in Southeast Asia within the Coral Triangle region, with subsequent diversification into the Indian and Pacific Ocean basins.

Conclusions: The presence of a species complex in the sandfish H. (Metriatyla) scabra is reported, providing clarity on its taxonomic identity, which prior to this study had been described exclusively on morphological characters. Given the degree of ambiguity associated with interspecific morphological descriptions of many Holothuroid taxa, data presented here describe intraspecific diversity of this valuable echinoderm.

This study evaluates the ecological status of the Aras River Basin (Türkiye) by analyzing benthic macroinvertebrate communities in relation to seasonal variations and anthropogenic pressures. During 2014-2015 sampling campaigns, we identified 126 taxa, of which 107 were identified at the species level and 19 at the genus level across 17 stations, with Insecta (87 taxa, 69%) showing the highest richness, followed by Clitellata (23 taxa, 18%). The dominant species Tubifex tubifex (15.87%), Chironomus riparius (15.60%), and Gammarus balcanicus (15.11%) served as key bioindicators, revealing significant organic pollution impacts, particularly in lentic habitats. Canonical Correspondence Analysis (CCA) for the summer period identified dissolved oxygen (DO) and pH as the primary environmental drivers, with pollution-tolerant taxa (e.g., Chironomus riparius) clustering in low-DO areas, while sensitive species (e.g., Baetis rhodani) were predominantly associated with well-oxygenated, alkaline conditions. Seasonal analyses demonstrated autumn as the most productive period (3,765 ind., 91 taxa), with Station 9 maintaining pristine conditions (BMWP score: 66, "Good") year-round. Conversely, spring showed the poorest water quality (BMWP < 25 at most stations), while summer exhibited intermediate conditions. Multivariate analyses (UPGMA, TWINSPAN) confirmed spatial clustering based on pollution gradients, with tolerant taxa (e.g., aquatic leeches, Chironomus spp.) dominating organically enriched sites and sensitive species (e.g., Plecoptera) restricted to high-quality habitats. Our findings highlight: (1) severe degradation at stations receiving agricultural/domestic waste (Stations 1-6), (2) the critical role of seasonal monitoring in detecting climate-driven stressors, and (3) the utility of macroinvertebrate-based indices (BMWP/ASPT) for basin-scale water quality assessment. The study provides a scientific basis for conserving transboundary freshwater ecosystems through targeted pollution control and habitat protection measures.

The Bale Mountains National Park (BMNP), situated in the southeast highlands of Ethiopia's Bale eco-region, is a globally recognized hotspot for biodiversity. The devastating rate of habitat degradation across various agro-climatic zones, in spite of its enormous ecological significance, puts many species' survival in jeopardy. This study aims to examine the effects of agro-climatic variation on floristic composition, structure, and explore human-induced factors driving the changes in ecosystem. To gather representative vegetation data, 144 sampling plots spanning 5.76 ha were set up along three altitudinal gradients with four replications. One-way ANOVA was used to compare the mean species composition and structure among agro-climatic zones, and significant differences were reported with p < 0.05. Results showed that mean DBH (49.63 ± 1.34 cm) and species richness (76) of the sub-moist mid highland were found to be significantly higher than in the cool moist mid highlands (44.50 ± 1.42 cm and 31, respectively) and in the cold humid afro-alpine zone (29). The sub-moist mid highland had a significantly higher density of seedlings, saplings, and mature trees than the cool moist mid highlands. Although the mean density and basal area of woody species did not differ significantly (p < 0.05) between the sub-moist mid highland and the cool moist mid highland, the sub-moist mid highland exhibited higher overall values, with 914 stems per hectare and 91.16 m² ha⁻¹, compared to 653 stems per hectare and 79.10 m² ha⁻¹ in the cool moist mid highland. The study concludes that the sub-moist mid highland supports a majority of species and contains trees with bigger space occupancy, and ecologically diverse communities which requires urgent protection measures. Because of the cold humid afro-alpine zone is ecologically delicate, it requires a comprehensive ecological approach to manage natural resource that incorporates ecosystem protection and restoration.

Background: Patterns of discordance between gene trees and the species trees they reside in are crucial to the coalescent vs. concatenation debate and may be key to resolving rapid radiations. However, errors in gene trees complicate the issue as topological errors can cause gene trees to appear erroneously discordant with the species tree. In this study, we evaluate the prevalence of discordance between gene trees and their species tree using an empirical dataset for a clade with a rapid radiation (Blaberidae). One key advance of our study is the use of complex, computationally intensive, selection-based codon models (FMutSel0 and SelAC) to identify the maximum likelihood gene tree. Our main hypothesis predicted that, if there are two competing topologies for a particular gene tree, then the one that is less discordant with the species tree will have less systematic error.

Results: Our experimental framework failed to show evidence for this, but only when discordance was measured in reference to a concatenation topology. In follow-up tests we see that the best candidate gene set yielded a coalescent species tree that was less discordant with gene trees.

Conclusions: We conclude from these tests that, although the frequency of discordance is on the low end of what is predicted by a range of modelling strategies, it is still extremely common overall and must be accounted for in order to achieve a biologically realistic outcome. These results allow us to support other relationships among blaberid cockroaches that were previously in flux as they now demonstrate molecular and morphological congruence. We suggest a few key improvements to the Blaberidae phylogeny, including identification of an anomaly zone spanning 10 backbone nodes and 6 additional nodes.

Prey species often develop toxic chemical defenses against predators, prompting predators to evolve traits that counteract these toxins. A prime example of this evolutionary arms race involves resistance to lethal cardiotonic steroids, which is associated with specific amino acid mutations in the α-subunit of Na+/K+-ATPase (ATP1A) across diverse predator species. The Japanese Crested Serpent-eagle (Spilornis cheela perplexus), which is endemic to the adjacent islands of Ishigaki and Iriomote in Okinawa, provides an intriguing example of this convergent evolution. This eagle preys on cane toads (Rhinella marina), an invasive species anthropogenically introduced only to Ishigaki Island, which defends itself by secreting cardiotonic steroids. Notably, no native prey species of the Crested Serpent-eagle on Ishigaki or Iriomote Island secrete cardiotonic steroids as a defense mechanism. To investigate the genetic and evolutionary background of potential toxin resistance in this eagle, we analyzed the genetic population structure and ATP1A gene sequences from individuals on Ishigaki and Iriomote Islands, as well as from the subspecies population on Simeulue Island, Indonesia. Whole-genome analysis revealed significant genetic isolation among the three island populations. However, the amino acid sequences of ATP1A paralogs were identical across all populations. Notably, the Q111E amino acid mutation in ATP1A1, which is associated with toxin resistance in other species, was detected in this eagle. A comparative analysis of ATP1A amino acid sequences across nine raptor species revealed that the Crested Serpent-eagle and Black-chested Snake Eagle (Circaetus pectoralis), both of which belong to the subfamily Circaetinae, share similar sequences that are distinct from those of other raptors. These findings indicate that possible lineage-specific adaptations in ATP1A provide the Crested Serpent-eagle with resistance to cardiotonic steroids. The conservation of this adaptive gene within species might have origins unrelated to the recent distribution of cardiotonic steroid-secreting prey but has coincidentally enabled the Crested Serpent-eagle on Ishigaki Island to prey on invasive species introduced by humans.

Background: Wolbachia are maternally inherited arthropod endosymbionts known for their diverse effects on host reproduction, which serve to increase their prevalence in host populations. As Wolbachia spreads, the frequency of the associated mitochondrial DNA (mtDNA) haplotypes tends to increase within the host population. Two distinct Wolbachia strains, wCI and wFem, are shared by two pierid butterfly sister species: Eurema mandarina and Eurema hecabe. The congruence of mtDNA phylogeny and Wolbachia infection status suggests hybrid introgression of mtDNA from E. hecabe to E. mandarina. This inference is based on the observation that uninfected E. mandarina have unique mtDNA haplotypes, distinct from the mtDNA haplotypes found in Wolbachia-infected E. mandarina and E. hecabe. In E. hecabe, Wolbachia infection has been considered fixed, with no expectation of uninfected individuals.

Results: Unexpectedly, Wolbachia-free E. hecabe individuals were discovered on the Yonaguni Island of Japan. We included these individuals in the phylogenetic analyses to reassess the impact of Wolbachia infection on Eurema butterflies. The nuclear Triosephosphate isomerase gene-based phylogenetic tree formed two discrete clades corresponding to E. mandarina and E. hecabe. Contrastingly, the mitochondrial cytochrome c oxidase subunit I gene-based tree consisted of three clades, Wolbachia-free E. mandarina, Wolbachia-free E. hecabe, and a clade consisting of Wolbachia-infected E. mandarina and E. hecabe, as well as two other Eurema species, Eurema ada and Eurema lacteola.

Conclusions: Our findings indicate that the mitochondria shared by E. mandarina and E. hecabe likely originate from a different species of Eurema (E. ada, E. lacteola, or others). Although the origin was not identified, our results indicate that Wolbachia provides significant evolutionary advantages to the associated mtDNA haplotypes across multiple Eurema species, leading to a complex mtDNA phylogeny.

Body mass plays a fundamental role in the macroevolutionary dynamics of morphological, ecological, and phylogenetic diversification. Given biomechanical principles, large body masses in terrestrial vertebrates may impose important constraints on the adaptative potential of skeletal morphology. This is especially true for the limbs, which are involved in both supporting and propelling the body during locomotion. We present a novel framework for evaluating how body mass structures patterns of morphological, ecological, and phylogenetic diversification using a dataset of forelimb traits for more than 600 terrestrial mammal species. We found that forelimb shape disparity increases with body mass for mammals generally as well as within mammalian subclades, suggesting that this trend is robust to phylogenetic scale. However, both phylogenetic and locomotor diversity (a proxy for ecological diversity) were high for all except the largest mammals and were not strongly associated with body mass. This suggests that small mammals are capable of speciating widely and evolving novel locomotor modes without requiring drastic changes to forelimb shape. However, as body mass increases, biomechanical constraints require substantial morphological changes to the forelimb to adapt to similar levels of locomotor mode disparity. We also show that different limb bone elements do not respond in the same way to increases in body mass when analyzed individually, perhaps due to differing developmental constraints. We provide new insights on how body mass structures macroevolutionary processes in mammals, and our approach can be generalized to examine this question for a variety of traits, ecological modes, and phylogenetic groups.