BMC ecology and evolution最新文献

Background: Among minute-sized and wingless arthropods, astigmatid mites stand out for their diverse range of symbiotic associations (parasitic, neutral and mutualistic), with both invertebrate and vertebrate hosts. When inhabiting discontinuous and ephemeral environments, astigmatid mites adapt their life cycle to produce a phoretic heteromorphic nymph. When feeding resources are depleted, phoretic nymphs disperse to new habitats through phoresy, attaching to a larger animal which transports them to new locations. This dispersal strategy is crucial for accessing patchy resources, otherwise beyond the reach of these minute arthropods. In Astigmata, the phoretic nymph is highly specialized for dispersal, equipped with an attachment organ and lacking a mouth and pharynx. Despite the common occurrence of phoretic associations in modern mites, their evolutionary origins remain poorly understood. Among Astigmata, the family Schizoglyphidae represents an early derivative lineage with phoretic tritonymphs; however, our knowledge of this family is limited to a single observation.

Results: Here, we report the oldest biotic association of arthropods fossilised in amber (~ 130 Ma, Lebanon): an alate termite with 16 phoretic tritonymphs of Schizoglyphidae (Plesioglyphus lebanotermi gen. et sp. n.). The mites are primarily attached to the membranes of the host's hindwings, using their attachment organs, pretarsal claws and tarsal setae. Additionally, we report new modern phoretic tritonymphs of this same family, on one of the earliest lineages of termites. These data collectively indicate that schizoglyphid-termite associations represent the oldest continuous mite-host associations. Notably, phoretic schizoglyphids retain a distinct mouth and pharynx, whereas these structures are absent in the modern phoretic stages of non-schizoglyphid Astigmata.

Conclusion: The discovery of Schizoglyphidae mites in Lebanese amber represents the oldest known continuous association between acariform mites and their hosts. This finding demonstrates the long-term evolutionary significance of phoresy in Astigmata, evidencing a relationship sustained for over 130 Ma. It indicates that these early mites lived inside termite nests as inquilines and used alate termites for dispersal. This ancient association offers key insights into the coevolution of both mites and termites, highlighting a potential for the future discoveries of similar mites. This fossil -a stem-group Astigmata- is important for the accurate calibration of acariform mite phylogenies, advancing our understanding of these mites evolutionary history.

Nocturnal ecology has hitherto led a shadowy existence in ecology, which traditionally focuses on diurnal species and functional relationships in the bright light of day. Yet nighttime hides exciting research insights and urgent conservation issues to be addressed. Citizen science is a promising approach to support this urgently needed exploration.

Background: In infected hosts, immune responses trigger a systemic energy reallocation away from energy storage and growth, to fuel a costly defense program. The exact energy costs of immune defense are however unknown in general. Life history theory predicts that such costs underpin trade-offs between host disease resistance and other fitness related traits, yet this has been seldom assessed. Here we investigate immune energy cost induced by infection, and their potential link to a trade-off between host resistance and fat storage that we previously exposed in sheep divergently selected for resistance to a pathogenic helminth.

Results: To this purpose, we developed a mathematical model of host-parasite interaction featuring individual changes in energy allocation over the course of infection. The model was fitted to data from an experimental infectious challenge in sheep from genetically resistant and susceptible lines to infer the magnitude of immune energy costs. A relatively small and transient immune energy cost in early infection best explained within-individual changes in growth, energy storage and parasite burden. Among individuals, predicted responses assuming this positive energy cost conformed to the observed trade-off between resistance and storage, whereas a cost-free scenario incorrectly predicted no trade-off.

Conclusions: Our mechanistic model fitting to experimental data provides novel insights into the link between energy costs and reallocation due to induced resistance within-individual, and trade-offs among individuals of selected lines. These will be useful to better understand the exact role of energy allocation in the evolution of host defenses, and for predicting the emergence of trade-offs in genetic selection.

Pterosaurs were the first vertebrates to evolve active flight. The lack of many well-preserved pterosaur fossils limits our understanding of the functional anatomy and behavior of these flight pioneers, particularly from their early history (Triassic to Middle Jurassic). Here we describe in detail the osteology of an exceptionally preserved Middle Jurassic pterosaur, the holotype of Dearc sgiathanach from the Isle of Skye, Scotland. We identify new autapomorphies of the flight apparatus (humerus and sternum), which further support the distinctiveness of Dearc compared with other early-diverging pterosaurs and describe features, such as the vertebral morphology, shared with later-diverging pterosaurs that probably developed convergently to support a large body size or as a sign of modular evolution. We used extant phylogenetic bracketing to infer the principal cranial and antebrachial musculature, indicating that Dearc had large and anteriorly placed palatal musculature that compensated for weak temporal jaw adductors and wing musculature suggestive of flight style reliant on powerful adduction and protraction of the humerus. Comparisons with other pterosaurs revealed that non-pterodactyloids such as Dearc, despite their overall conservative bauplans, adapted various flight and feeding styles. The osteology and myology of Dearc are indicative of a large predator that flew and hunted above lagoons and nearshore environments of the Middle Jurassic.

Wings are primarily used in flight but also play a role in mating behaviour in many insects. Drosophila species exhibit a variety of pigmentation patterns on their wings. In some sexually dimorphic Drosophilids, a pigmented spot pattern is found at the top-right edge of the male wings. Our understanding of wing spot thermal plasticity in sexually dimorphic species is limited with wing spots being primarily associated with sexual selection. Here, we investigated the wing pigmentation response of two species with wing spots: D. biarmipes and D. suzukii species to thermal variation. We exposed freshly hatched larvae of both the species to three different growth temperatures and checked for wing pigmentation in adult males. Our results indicate wing pigmentation is a plastic trait in the species studied and that wing pigmentation is negatively correlated with higher temperature. In both species, wings were darker at lower temperature compared to higher temperature. Further, D. suzukii exhibits darker wing pigmentation compared to D. biarmipes. Variation in wing pigmentation in both D. suzukii and D. biarmipes could reflect habitat level differences; indicating a strong G*E interaction. Raman spectral analysis indicated a shift in chemical profiles of pigmented vs. non-pigmented areas of the wing. The wing spot was found enriched with carbon-carbon double-bond compared to the non-pigmented wing area. We report that C = C formation in spotted area is thermally controlled and conserved in two members of the suzukii subgroup i.e. D. biarmipes and D. suzukii. Our study indicated a conserved mechanism of the spot formation in two Drosophila species coming from contrasting distribution ranges.

As the extinction risk of plants increases globally, there is need to prioritize areas with high floristic richness and diversity to inform the design of evidence-based conservation interventions. As such, this study aimed to comparatively analyse floristic diversity in six central forest reserves (CFR) of north eastern Uganda. This was guided by two objectives namely; (i) to determine the floristic richness and diversity in the CFRs and (ii) to evaluate the similarity and complementarity of floristic composition. Data was collected from nested quadrats (20 × 20 m for trees, 10 × 10 m for shrubs and 5 × 5 m for herbaceous climbers, forbs and grasses) placed at intervals of 100 m along a transect of 1000 - 1500 m. Species richness, diversity and evenness were determined for each CFR. Binary similarity coefficients were computed because only presence/absence data of plant species was recorded. A sum of 417 plant species in 76 families were recorded representing 8.7% of known vascular plants reported in Uganda. The CFRs have significantly variable Shannon-Wiener diversity indices ranging from 4.2 in Kano CFR to 4.47 in Bululu hill CFR (t = 85.291, df = 4, p = 0.00). The CFRs cluster into two groups namely Onyurut and Ogera hills and Akur, Kano, Bululu hills and Mount Moroto. The lowest similarity index was between Ogera hills and Moumt Moroto CFRs (0.37 or 37%) while the highest was between Akur and Kano CFRs (0.63 or 63%). The CFRs complement one another by supporting plant species not recorded elsewhere with three CFRs (Bululu hills, Mount Moroto and Onyurut) accounting for 81.53% of the plant taxa. The CFRs in NE Uganda have richness and floristic diversity with up to 8.7% of the known plants in Uganda present. The conservation status of these species is Vulnerable (4), Near Threatened (4), Least Concern (137), Data Deficient (1) and Not Evaluated (271). The two similarity clusters depict variation in altitudinal, proximity and climatic conditions. Five CFRs are required to conserve 95% of the species recorded. Therefore, the CFRs investigated play a complementary role in conserving the floristic diversity in north eastern Uganda.

Background: Trait variation is shaped by functional roles of traits and the strength and direction of selection acting on the traits. We hypothesized that in butterflies, sexually selected colouration is more variable owing to condition-dependent nature and directional selection on sexual ornaments, whereas naturally selected colouration may be less variable because of stabilising selection. We measured reflectance spectra, and extracted colour parameters, to compare the amount of variation in sexually versus naturally selected colour patches across wing surfaces and sexes of 20 butterfly species across 4 families (Nymphalidae, Papilionidae, Pieridae, Lycaenidae).

Results: We found that: (a) males had more conspicuous, i.e., brighter and more saturated colour patches compared with females (as expected of sexually selected traits but not necessarily of naturally selected traits), and (b) dorsal surfaces in both sexes had more conspicuous sexual ornaments as well as protective (aposematic/mimetic) colour patches on darker wing backgrounds, compared with ventral surfaces. However, colour patches did not differ in the amount of variation either in selection (ecological/sexual functions), sex or wing surface-specific manner.

Conclusions: These findings show that functional roles and selection influence colour parameters but not the amount of variation in butterfly wing colour patterns.

Climate warming has become a hot issue of common concern all over the world, and wind energy has become an important clean energy source. Wind farms, usually built in wild lands like grassland, may cause damage to the initial ecosystem and biodiversity. However, the impact of wind farms on the functional diversity of plant communities remains a subject with unclear outcomes. In this study, we chose 108 sample plots and identified 10 plant functional traits through a field vegetation survey. We used general linear regression analysis to assess how wind farm influenced vegetation community diversity, focusing on ten distinct plant functional traits. The study revealed that wind farm had significant impacts on grassland plant communities, diminishing diversity and functional traits, which leads to species composition convergence. Additionally, wind farm increased certain functional traits, like height and leaf area, while decreasing phosphorus content. Furthermore, the productivity of these plant communities was reduced by wind farm presence. This study highlights the negative consequences of wind farms in Inner Mongolia on plant diversity, aiming to offer scientific recommendations for the optimal arrangement of wind farms to safeguard biodiversity.

The Sydney funnel-web spider Atrax robustus O. Pickard-Cambridge, 1877 is an iconic Australian species and considered among the most dangerously venomous spiders for humans. Originally described in 1877 from a single specimen collected in "New Holland", this spider has a complex taxonomic history. The most recent morphological revision of funnel-web spiders (Atracidae) lists this species as both widespread and common in the Sydney Basin bioregion and beyond, roughly 250 km from the Newcastle area south to the Illawarra, and extending inland across the Blue Mountains. Morphological variability and venom diversity in this species appear to be unusually high, raising questions about species concepts and diversity in these spiders. In this study, we use a combination of molecular phylogenetics, divergence time analyses and morphology to establish the Sydney funnel-web spider as a complex of three species. The "real" Sydney funnel-web spider Atrax robustus is relatively widespread in the Sydney metropolitan region. A second species, Atrax montanus (Rainbow, 1914), which is revalidated here, overlaps but mainly occurs further south and west, and a third larger species, Atrax christenseni sp. nov., is found in a small area surrounding Newcastle to the north. The revised taxonomy for funnel-web spiders may have practical implications for antivenom production and biochemical studies on spider venoms. Although no human fatalities have occurred since the development of antivenom in the 1980s, antivenom for Sydney funnel-web spiders might be optimized by considering biological differentiation at the species level.

Background: Semi-aquatic mammals represent a transitional phase in the evolutionary spectrum between terrestrial and aquatic mammals. The sense of balance is crucial for mammalian locomotion, and in semi-aquatic mammals, the structural foundation of this sense (the vestibular system) shows distinct morphological adaptations to both aquatic and terrestrial environments compared to their terrestrial counterparts. Despite this, the precise molecular mechanisms driving these adaptations remain elusive. Our study endeavors to unravel the genetic components associated with the sense of balance in semi-aquatic mammals and to examine the evolutionary trajectories of these genes, shed light on the molecular mechanisms underlying the adaptive evolution of balance perception in semi-aquatic mammals.

Results: We selected 42 mammal species across 20 orders, 38 families, and 42 genera for analysis. We analyzed a comprehensive set of 116 genes related to the vestibular system's development or function. Our findings indicate that 27 of these genes likely experienced adaptive evolution in semi-aquatic mammals. Particularly, genes such as SLC26A2, SOX10, MYCN, and OTX1 are implicated in collectively orchestrating morphological adaptations in the semicircular canals to suit semi-aquatic environments. Additionally, genes associated with otolith development, including SLC26A2, OC90, and OTOP1, likely regulate otolith sensitivity across various locomotor modes. Moreover, genes linked to vestibular disorders, such as GJB2, GJB6, and USH1C, may provide a molecular foundation for averting vertigo amidst intricate locomotor scenarios in semi-aquatic mammals.

Conclusions: Our research offers insights into the molecular mechanisms underlying the evolution of the sense of balance in semi-aquatic mammals, while also providing a new research direction for the adaptive evolution of mammals undergoing a secondary transition to an aquatic lifestyle.