Seed protein and isozyme variations in Triticum tauschii (Aegilops squarrosa)

Sixty Triticum tauschii (Aegilops squarrosa, 2n=2x=14, DD) accessions were evaluated for the variability of high-molecular-weight (HMW) glutenins, gliadins and isozymes of seed esterase, -amylase and glucose-phosphate isomerase. Wide variability was observed for HMW-glutenins and gliadins. The implications of unique HMW-glutenin alleles for quality parameters are discussed. Isozyme evaluations indicated more variability for the Est-D ^t 5 locus as compared to the Est-D5 of bread-wheat. The polymorphism for -Amy-D ^t 1 was less than that of -Amy-D1. Similar to the bread-wheat situation, Gpi-D ^t 1 showed no polymorphism. The variability observed with the traits evaluated can be readily observed in T. turgidum x T. tauschii synthetic hexaploids (2n=6x=42, AABBDD) suggesting that T. tauschii accessions may be a rich source for enhancing the genetic variability of T. aestivum cultivars.     

Resistance to the cereal cyst nematode (Heterodera avenae Woll.) transferred from the wild grassAegilops ventricosa to hexaploid wheat by a “stepping-stone” procedure

Transfer of resistance toHeterodera avenae, the cereal cyst nematode (CCN), by a stepping-stone procedure from the wild grassAegilops ventricosa to hexaploid wheat has been demonstrated. The number of nematodes per plant was lower, and reached a plateau much earlier, in the resistant introgression line H93-8 (1–2 nematodes per plant) than in the recipient H10-15 wheat (14–16 nematodes per plant). Necrosis (hypersensitive reaction) near the nematode, little cell fusion, and few, often degraded syncytia were observed in infested H93-8 roots, while abundant, well-formed syncytia were present in the susceptible H10-15 wheat. Line H93-8 was highly resistant to the two Spanish populations tested, as well as the four French races (Fr1-Fr4), and the British pathotype Hall, but was susceptible to the Swedish pathotypes HgI and HgIII. Resistance was inherited as though determined by a single quasi-dominant factor in the F₂ generations resulting from crosses of H93-8 with H10-15 and with Loros, a resistant wheat carrying the geneCre1 (syn.Ccn1). The resistance gene in H93-8 (Cre2 orCcn2) is not allelic with respect to that in Loros. RFLPs and other markers, together with the cytogenetical evidence, indicate that theCre2 gene has been integrated into a wheat chromosome without affecting its meiotic pairing ability. Introduction ofCre2 by backcrossing into a commercial wheat backgroud increases grain yield when under challenge by the nematode and is not detrimental in the absence of infestation.     

Ecosystem-level effects of re-oligotrophication and N:P imbalances in rivers and estuaries on a global scale

Trends and ecological consequences of phosphorus (P) decline and increasing nitrogen (N) to phosphorus (N:P) ratios in rivers and estuaries are reviewed and discussed. Results suggest that re-oligotrophication is a dominant trend in rivers and estuaries of high-income countries in the last two–three decades, while in low-income countries widespread eutrophication occurs. The decline in P is well documented in hundreds of rivers of United States and the European Union, but the biotic response of rivers and estuaries besides phytoplankton decline such as trends in phytoplankton composition, changes in primary production, ecosystem shifts, cascading effects, changes in ecosystem metabolism, etc., have not been sufficiently monitored and investigated, neither the effects of N:P imbalance. N:P imbalance has significant ecological effects that need to be further investigated. There is a growing number of cases in which phytoplankton biomass have been shown to decrease due to re-oligotrophication, but the potential regime shift from phytoplankton to macrophyte dominance described in shallow lakes has been documented only in a few rivers and estuaries yet. The main reasons why regime shifts are rarely described in rivers and estuaries are, from one hand the scarcity of data on macrophyte cover trends, and from the other hand physical factors such as peak flows or high turbidity that could prevent a general spread of submerged macrophytes as observed in shallow lakes. Moreover, re-oligotrophication effects on rivers may be different compared to lakes (e.g., lower dominance of macrophytes) or estuaries (e.g., limitation of primary production by N instead of P) or may be dependent on river/estuary type. We conclude that river and estuary re-oligotrophication effects are complex, diverse and still little known, and in some cases are equivalent to those described in shallow lakes, but the regime shift is more likely to occur in mid to high-order rivers and shallow estuaries.     

Damage to living trees contributes to almost half of the biomass losses in tropical forests

Accurate estimates of forest biomass stocks and fluxes are needed to quantify global carbon budgets and assess the response of forests to climate change. However, most forest inventories consider tree mortality as the only aboveground biomass (AGB) loss without accounting for losses via damage to living trees: branchfall, trunk breakage, and wood decay. Here, we use ~151,000 annual records of tree survival and structural completeness to compare AGB loss via damage to living trees to total AGB loss (mortality + damage) in seven tropical forests widely distributed across environmental conditions. We find that 42% (3.62 Mg ha⁻¹ year⁻¹; 95% confidence interval [CI] 2.36–5.25) of total AGB loss (8.72 Mg ha⁻¹ year⁻¹; CI 5.57–12.86) is due to damage to living trees. Total AGB loss was highly variable among forests, but these differences were mainly caused by site variability in damage-related AGB losses rather than by mortality-related AGB losses. We show that conventional forest inventories overestimate stand-level AGB stocks by 4% (1%–17% range across forests) because assume structurally complete trees, underestimate total AGB loss by 29% (6%–57% range across forests) due to overlooked damage-related AGB losses, and overestimate AGB loss via mortality by 22% (7%–80% range across forests) because of the assumption that trees are undamaged before dying. Our results indicate that forest carbon fluxes are higher than previously thought. Damage on living trees is an underappreciated component of the forest carbon cycle that is likely to become even more important as the frequency and severity of forest disturbances increase.     

The detection and attribution of extreme reductions in vegetation growth across the global land surface

Negative extreme anomalies in vegetation growth (NEGs) usually indicate severely impaired ecosystem services. These NEGs can result from diverse natural and anthropogenic causes, especially climate extremes (CEs). However, the relationship between NEGs and many types of CEs remains largely unknown at regional and global scales. Here, with satellite-derived vegetation index data and supporting tree-ring chronologies, we identify periods of NEGs from 1981 to 2015 across the global land surface. We find 70% of these NEGs are attributable to five types of CEs and their combinations, with compound CEs generally more detrimental than individual ones. More importantly, we find that dominant CEs for NEGs vary by biome and region. Specifically, cold and/or wet extremes dominate NEGs in temperate mountains and high latitudes, whereas soil drought and related compound extremes are primarily responsible for NEGs in wet tropical, arid and semi-arid regions. Key characteristics (e.g., the frequency, intensity and duration of CEs, and the vulnerability of vegetation) that determine the dominance of CEs are also region- and biome-dependent. For example, in the wet tropics, dominant individual CEs have both higher intensity and longer duration than non-dominant ones. However, in the dry tropics and some temperate regions, a longer CE duration is more important than higher intensity. Our work provides the first global accounting of the attribution of NEGs to diverse climatic extremes. Our analysis has important implications for developing climate-specific disaster prevention and mitigation plans among different regions of the globe in a changing climate.     

Short-term effects of a large dam decommissioning on biofilm structure and functioning

Aging dams and the rising efforts to restore stream ecosystems are increasing the number of dam decommissioning programs. Although dam decommissioning aims at improving in-stream habitat, biodiversity, and ecosystem functioning in the long term, it might also cause ecological impacts in the short term due to the mobilization of the sediment accumulated in the reservoir. Benthic biofilm in particular can be impaired by episodes of high turbidity and scouring. We conducted a multiple before-after/control-impact experiment to assess the effects of the drawdown of a large dam (42 m tall), a first step to its decommissioning, on biofilm structure (biomass and chlorophyll-a) and functioning (metabolism, nutrient uptake, and organic matter breakdown). Our results show that the reservoir drawdown reduced the autotrophic biofilm biomass (chlorophyll-a) downstream from the dam, which in turn lowered metabolism. However, nitrogen and phosphorus uptake by the biofilm was not affected. Organic matter breakdown was slower below the dam than in nearby undammed reaches before and during drawdown. All drawdown effects quickly disappeared and reaches downstream from the dam approached values found in nearby undammed reaches. Thus, our results indicate that the effects of reservoir drawdown on stream biofilms exist but may be small and disappear rapidly.     

Biological traits and living conditions of Maya Indian and non Maya girls from Merida,Mexico

A total of 522 girls and their families from low and middle social strate were examined in the northern part of Merida (Yucatan) during 1988 and 1989. Marital radius in the parental generation was relatively long (146 km), and it was six times longer for non-Maya and mixed couples than Maya. Living and housing conditions were similar for both Maya and non-Maya (mixed couples typically had an intermediate condition), except for sewage system (sanitation). The Maya income was 64% lower. Maya men and women were short. The girls from Merida were short, hyper-brachycephalic (short headed), and europrosopic (broad face). Among them, Maya girls were even shorter, more round-headed, and more broad-faced than non-Maya girls. Menarche occurred on the average at an age of 12.6 years in mothers and 12.1 years in daughters. As the generation time was about 25 years, there was a slow acceleration of maturation (0.2 years per decade). Presumably, also stature has increased in recent years.     

Sex determination and optimal development in the Moorish gecko,Tarentola mauritanica

Under temperature sex determination (TSD), sex is determined by temperature during embryonic development. Depending on ecological and physiological traits and plasticity, TSD species may face demographic collapse due to climate change. In this context, asymmetry in bilateral organisms can be used as a proxy for developmental instability and, therefore, deviations from optimal incubation conditions. Using Tarentola mauritanica gecko as a model, this study aimed first to confirm TSD, its pattern and pivotal temperature, and second to assess the local adaptation of TSD and variation of asymmetry patterns across four populations under different thermal regimes. Eggs were incubated at different temperatures, and hatchlings were sexed and measured. The number of lamellae was counted in adults and hatchlings. Results were compatible with a TSD pattern with males generated at low and females at high incubation temperatures. Estimated pivotal temperature coincided with the temperature producing lower embryonic mortality, evidencing selection towards balanced sex ratios. The temperature of oviposition was conservatively selected by gravid females. Asymmetry patterns found were likely related to nest temperature fluctuations. Overall, the rigidity of TSD may compromise reproductive success, and demographic stability in this species in case thermal nest choice becomes constrained by climate change.     

Exploring the legacy of African and Indigenous Caribbean admixture in Puerto Rico

Objectives

From an anthropological genetic perspective, little is known about the ethnogenesis of African descendants in Puerto Rico. Furthermore, historical interactions between Indigenous Caribbean and African descendant peoples that may be reflected in the ancestry of contemporary populations are understudied. Given this dearth of genetic research and the precedence for Afro-Indigenous interactions documented by historical, archeological, and other lines of evidence, we sought to assess the biogeographic origins of African descendant Puerto Ricans and to query the potential for Indigenous ancestry within this community.

Materials and Methods

Saliva samples were collected from 58 self-identified African descendant Puerto Ricans residing in Puerto Rico. We sequenced whole mitochondrial genomes and genotyped Y chromosome haplogroups for each male individual (n = 25). Summary statistics, comparative analyses, and network analysis were used to assess diversity and variation in haplogroup distribution between the sample and comparative populations.

Results

As indicated by mitochondrial haplogroups, 66% had African, 5% had European, and 29% had Indigenous American matrilines. Along the Y chromosome, 52% had African, 28% had Western European, 16% had Eurasian, and, notably, 4% had Indigenous American patrilines. Both mitochondrial and Y chromosome haplogroup frequencies were significantly different from several comparative populations.

Discussion

Biogeographic origins are consistent with historical accounts of African, Indigenous American, and European ancestry. However, this first report of Indigenous American paternal ancestry in Puerto Rico suggests distinctive features within African descendant communities on the island. Future studies expanding sampling and incorporating higher resolution genetic markers are necessary to more fully understand African descendant history in Puerto Rico.     

Two centuries of spatial and temporal dynamics of freshwater fish introductions

Aim

Investigating major freshwater fish flows (translocations) between biogeographic regions and their temporal dynamics and also quantifying spatial patterns and temporal changes in the array of introduced species, and the emergence and distance between major donor and recipient regions.

Location

Global.

Time Period

1800–2020.

Major Taxa Studied

Freshwater fishes.

Methods

We analysed a global dataset on freshwater fish introductions (4241 events of 688 species). Freshwater fish flows were investigated with flow diagrams and χ² tests, while PERMANOVA (permutational multivariate analysis of variance) was used to test the association between species and regions and temporal shifts. Cluster analysis revealed major recipient areas and composition of the introduced species. Finally, changes in distances between donor and recipient sites were tested with PERMANOVA.

Results

The number of introductions between biogeographic regions mirrored the European and North American dominance before World War II (WWII) and the trends in recreational fishing, biocontrol programmes and food production, especially in the Sino-Oriental region, which has a long tradition of aquaculture and fishkeeping. Over the years, the origins and composition of introduced species changed uniquely in each biogeographic region, although the most introduced species are common to every region. Salmonids and other cold-water species were frequently introduced before the 1950s, whereas tropical ornamental and aquaculture species currently prevail. Distances between donor and recipient sites did not vary over the time. After WWII, the Sino-Oriental region consolidated its dominance and the Ethiopian and Neotropical regions emerged as new global donor and recipient regions.

Main Conclusions

Global policy should focus on tropical ornamental and aquaculture species, which could benefit from global warming, especially in the Sino-Oriental region, because it currently dominates freshwater fish species flows, and the Ethiopian and Neotropical regions, because they recently emerged as important global donor and recipient regions of freshwater fish introductions.