| 1. |
|
|
| 2. |
- Kruger, M., et al.
(författare)
-
Differential contribution of nitrifying prokaryotes to groundwater nitrification
- 2023
-
Ingår i: ISME Journal. - 1751-7362. ; 17, s. 1601-1611
-
Tidskriftsartikel (refereegranskat)abstract
- The ecophysiology of complete ammonia-oxidizing bacteria (CMX) of the genus Nitrospira and their widespread occurrence in groundwater suggests that CMX bacteria have a competitive advantage over ammonia-oxidizing bacteria (AOB) and archaea (AOA) in these environments. However, the specific contribution of their activity to nitrification processes has remained unclear. We aimed to disentangle the contribution of CMX, AOA and AOB to nitrification and to identify the environmental drivers of their niche differentiation at different levels of ammonium and oxygen in oligotrophic carbonate rock aquifers. CMX ammonia monooxygenase sub-unit A (amoA) genes accounted on average for 16 to 75% of the total groundwater amoA genes detected. Nitrification rates were positively correlated to CMX clade A associated phylotypes and AOB affiliated with Nitrosomonas ureae. Short-term incubations amended with the nitrification inhibitors allylthiourea and chlorate suggested that AOB contributed a large fraction to overall ammonia oxidation, while metaproteomics analysis confirmed an active role of CMX in both ammonia and nitrite oxidation. Ecophysiological niche differentiation of CMX clades A and B, AOB and AOA was linked to their requirements for ammonium, oxygen tolerance, and metabolic versatility. Our results demonstrate that despite numerical predominance of CMX, the first step of nitrification in oligotrophic groundwater appears to be primarily governed by AOB. Higher growth yields at lower ammonia turnover rates and energy derived from nitrite oxidation most likely enable CMX to maintain consistently high populations.
|
|
| 3. |
- Clark, Adam Thomas, et al.
(författare)
-
General statistical scaling laws for stability in ecological systems
- 2021
-
Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 24:7, s. 1474-1486
-
Tidskriftsartikel (refereegranskat)abstract
- Ecological stability refers to a family of concepts used to describe how systems of interacting species vary through time and respond to disturbances. Because observed ecological stability depends on sampling scales and environmental context, it is notoriously difficult to compare measurements across sites and systems. Here, we apply stochastic dynamical systems theory to derive general statistical scaling relationships across time, space, and ecological level of organisation for three fundamental stability aspects: resilience, resistance, and invariance. These relationships can be calibrated using random or representative samples measured at individual scales, and projected to predict average stability at other scales across a wide range of contexts. Moreover deviations between observed vs. extrapolated scaling relationships can reveal information about unobserved heterogeneity across time, space, or species. We anticipate that these methods will be useful for cross-study synthesis of stability data, extrapolating measurements to unobserved scales, and identifying underlying causes and consequences of heterogeneity.
|
|
| 4. |
|
|
| 5. |
- Nilsson, E., et al.
(författare)
-
Multiple cryptic species of sympatric generalists within the avian blood parasite Haemoproteus majoris
- 2016
-
Ingår i: Journal of evolutionary biology. - : Wiley. - 1010-061X. ; 29:9, s. 1812-1826
-
Tidskriftsartikel (refereegranskat)abstract
- The avian haemosporidian parasite Haemoproteus majoris has been reported to infect a wide range of passerine birds throughout the Holarctic ecozone. Five cytochrome b (cyt b) lineages have been described as belonging to the morphological species H. majoris, and these form a tight phylogenetic cluster together with 13 undescribed lineages that differ from each other by < 1.2% in sequence divergence. Records in a database (MalAvi) that contains global findings of haemosporidian lineages generated by universal primers suggest that these lineages vary substantially in host distribution. We confirm this pattern in a data set collected at Lake Kvismaren, Sweden, where three of the generalist lineages have local transmission. However, whether these lineages represent intraspecific mitochondrial diversity or clusters of cryptic species has previously not been examined. In this study, we developed novel molecular markers to amplify the partial segments of four nuclear genes to determine the level of genetic diversity and gene phylogenies among the five morphologically described cyt b lineages of H. majoris. All five cyt b lineages were strongly associated with unique nuclear alleles at all four nuclear loci, indicating that each mitochondrial lineage represents a distinct biological species. Within lineages, there was no apparent association between nuclear alleles and host species, indicating that they form genetically unstructured populations across multiple host species.
|
|
