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| 2. |
- Gremare, A., et al.
(författare)
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Feeding behaviour and functional response of Abra ovata and A-nitida compared by image analysis
- 2004
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Ingår i: Marine Ecology-Progress Series. - 0171-8630. ; 267, s. 195-208
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Tidskriftsartikel (refereegranskat)abstract
- An automated image analysis system was used to monitor sediment surface feeding activity of 2 bivalves (Abra ovata and A. nitida) inhabiting contrasting environments. A larger variety of feeding behaviours was recorded in A. nitida, whereas A. ovata mostly fed at the sediment surface. There were also clear differences in the behaviour of the 2 species during surface deposit feeding (i.e. a wider extension of the inhalant siphon in A. ovata, and the exhalant siphon being located below the sediment-water interface in A. ovata and above this interface in A. nitida). In A. nitida, increase in feeding activity resulted mostly from an increase in feeding intensity, and not from an increase in the amount of time devoted to feeding. In A. ovata, the most active bivalves tended to increase their activity mostly by increasing the amount of time devoted to feeding. This suggests that feeding intensity was limited in A. ovata but not in A. nitida. Food dilution and food addition experiments were carried out to assess the functional response in the 2 species. The results of the food dilution experiments were statistically insignificant due to high inter-individual variability. Food addition significantly affected feeding activity in A. ovata and A. nitida, although in different ways. In A. ovata, feeding activity was highest at intermediate food concentrations, and inhibited at the highest ones. In A. nitida, increased feeding activity was induced at higher concentrations than in A. ovata, and feeding activity was greatest at the highest food concentration. Such discrepancies in feeding behaviour and functional response in closely related species characterise the difficulty in delineating functional groups in benthic deposit-feeders.
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| 3. |
- Hempel, Elisabeth, et al.
(författare)
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Blue Turns to Gray : Paleogenomic Insights into the Evolutionary History and Extinction of the Blue Antelope (Hippotragus leucophaeus)
- 2022
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Ingår i: Molecular biology and evolution. - : Oxford University Press (OUP). - 0737-4038 .- 1537-1719. ; 39:12
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Tidskriftsartikel (refereegranskat)abstract
- The blue antelope (Hippotragus leucophaeus) is the only large African mammal species to have become extinct in historical times, yet no nuclear genomic information is available for this species. A recent study showed that many alleged blue antelope museum specimens are either roan (Hippotragus equinus) or sable (Hippotragus niger) antelopes, further reducing the possibilities for obtaining genomic information for this extinct species. While the blue antelope has a rich fossil record from South Africa, climatic conditions in the region are generally unfavorable to the preservation of ancient DNA. Nevertheless, we recovered two blue antelope draft genomes, one at 3.4× mean coverage from a historical specimen (∼200 years old) and one at 2.1× mean coverage from a fossil specimen dating to 9,800–9,300 cal years BP, making it currently the oldest paleogenome from Africa. Phylogenomic analyses show that blue and sable antelope are sister species, confirming previous mitogenomic results, and demonstrate ancient gene flow from roan into blue antelope. We show that blue antelope genomic diversity was much lower than in roan and sable antelope, indicative of a low population size since at least the early Holocene. This supports observations from the fossil record documenting major decreases in the abundance of blue antelope after the Pleistocene–Holocene transition. Finally, the persistence of this species throughout the Holocene despite low population size suggests that colonial-era human impact was likely the decisive factor in the blue antelope's extinction.
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| 4. |
- Liu, Shanlin, et al.
(författare)
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Ancient and modem genomes unravel the evolutionary history of the rhinoceros family
- 2021
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Ingår i: Cell. - : Elsevier. - 0092-8674 .- 1097-4172. ; 184:19, s. 4874-4885.e16
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Tidskriftsartikel (refereegranskat)abstract
- Only five species of the once-diverse Rhinocerotidae remain, making the reconstruction of their evolutionary history a challenge to biologists since Darwin. We sequenced genomes from five rhinoceros species (three extinct and two living), which we compared to existing data from the remaining three living species and a range of outgroups. We identify an early divergence between extant African and Eurasian lineages, resolving a key debate regarding the phylogeny of extant rhinoceroses. This early Miocene (similar to 16 million years ago [mya]) split post-dates the land bridge formation between the Afro-Arabian and Eurasian landmasses. Our analyses also show that while rhinoceros genomes in general exhibit low levels of genome-wide diversity, heterozygosity is lowest and inbreeding is highest in the modern species. These results suggest that while low genetic diversity is a long-term feature of the family, it has been particularly exacerbated recently, likely reflecting recent anthropogenic-driven population declines.
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| 5. |
- Tagliabue, Giulia, et al.
(författare)
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Ultrafast hot-hole injection modifies hot-electron dynamics in Au/p-GaN heterostructures
- 2020
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Ingår i: Nature Materials. - : Springer Nature. - 1476-1122 .- 1476-4660. ; 19:12, s. 1312-1318
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Tidskriftsartikel (refereegranskat)abstract
- A fundamental understanding of hot-carrier dynamics in photo-excited metal nanostructures is needed to unlock their potential for photodetection and photocatalysis. Despite numerous studies on the ultrafast dynamics of hot electrons, so far, the temporal evolution of hot holes in metal-semiconductor heterostructures remains unknown. Here, we report ultrafast (t < 200 fs) hot-hole injection from Au nanoparticles into the valence band of p-type GaN. The removal of hot holes from below the Au Fermi level is observed to substantially alter the thermalization dynamics of hot electrons, reducing the peak electronic temperature and the electron-phonon coupling time of the Au nanoparticles. First-principles calculations reveal that hot-hole injection modifies the relaxation dynamics of hot electrons in Au nanoparticles by modulating the electronic structure of the metal on timescales commensurate with electron-electron scattering. These results advance our understanding of hot-hole dynamics in metal-semiconductor heterostructures and offer additional strategies for manipulating the dynamics of hot carriers on ultrafast timescales. Photo-excited gold nanoparticles are shown to provide ultrafast and efficient hot-hole injection to the valence band of p-type GaN, substantially altering hot-electron dynamics in the nanoparticles and forming a basis to design hot-hole-based optoelectronics.
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| 6. |
- Westbury, Michael V, et al.
(författare)
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Ecological Specialization and Evolutionary Reticulation in Extant Hyaenidae
- 2021
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Ingår i: Molecular biology and evolution. - : Oxford University Press (OUP). - 0737-4038 .- 1537-1719. ; 38:9, s. 3884-3897
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Tidskriftsartikel (refereegranskat)abstract
- During the Miocene, Hyaenidae was a highly diverse family of Carnivora that has since been severely reduced to four species: the bone-cracking spotted, striped, and brown hyenas, and the specialized insectivorous aardwolf. Previous studies investigated the evolutionary histories of the spotted and brown hyenas, but little is known about the remaining two species. Moreover, the genomic underpinnings of scavenging and insectivory, defining traits of the extant species, remain elusive. Here, we generated an aardwolf genome and analyzed it together with the remaining three species to reveal their evolutionary relationships, genomic underpinnings of their scavenging and insectivorous lifestyles, and their respective genetic diversities and demographic histories. High levels of phylogenetic discordance suggest gene flow between the aardwolf lineage and the ancestral brown/striped hyena lineage. Genes related to immunity and digestion in the bone-cracking hyenas and craniofacial development in the aardwolf showed the strongest signals of selection, suggesting putative key adaptations to carrion and termite feeding, respectively. A family-wide expansion in olfactory receptor genes suggests that an acute sense of smell was a key early adaptation. Finally, we report very low levels of genetic diversity within the brown and striped hyenas despite no signs of inbreeding, putatively linked to their similarly slow decline in effective population size over the last ∼2 million years. High levels of genetic diversity and more stable population sizes through time are seen in the spotted hyena and aardwolf. Taken together, our findings highlight how ecological specialization can impact the evolutionary history, demographics, and adaptive genetic changes of an evolutionary lineage.
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