Climatic signals in growth and its relation to ENSO events of two Prosopis species following a latitudinal gradient in South America

Semiarid environments throughout the world have lost a major part of their woody vegetation and biodiversity due to the effects of wood cutting, cattle grazing and subsistence agriculture. The resulting state is typically used for cattle production, but the productivity of these systems is often very low, and erosion of the unprotected soil is a common problem. Such dry‐land degradation is of great international concern, not only because the resulting state is hardly productive but also because it paves the way to desertification. The natural distribution of the genus Prosopis includes arid and semiarid zones of the Americas, Africa and Asia, but the majority of the Prosopis species are, however, native to the Americas. In order to assess a likely gradient in the response of tree species to precipitation, temperature and their connection to El Niño southern oscillation (ENSO) events, two Prosopis species were chosen along a latitudinal gradient in Latin America, from northern Peru to central Chile: Prosopis pallida from a semi‐arid land in northern and southern Peru and P. chilensis from a semiarid land in central Chile. Growth rings of each species were crossdated at each sampling site using classical dendrochronological techniques. Chronologies were related with instrumental climatic records in each site, as well as with SOI and N34 series. Cross‐correlation, spectral and wavelet analysis techniques were used to assess the relation of growth with precipitation and temperature. Despite the long distance among sites, the two Prosopis species presented similar responses. Thus, the two species' growth is positively correlated to precipitation, while with temperature it is not. In northern Peru, precipitation and growth of P. pallida present a similar cyclic pattern, with a period of around 3 years. On the other hand, P. pallida in southern Peru, and P. chilensis also present this cyclic pattern, but also another one with lower frequency, coinciding with the pattern of precipitation. Both cycles are within the range of the ENSO band.     

Short-term climatic trends affect the temporal variability of macroinvertebrates in California 'Mediterranean' streams

1. Long‐term studies in ecology are essential for understanding natural variability and in interpreting responses to disturbances and human perturbations. We assessed the long‐term variability, stability and persistence of macroinvertebrate communities by analysing data from three regions in northern California with a mediterranean‐climate. During the study period, precipitation either increased or decreased, and extreme drought events occurred in each region. 2. Temporal trends in precipitation resulted in shifts from ‘dry‐year’ communities, dominated by taxa adapted to no or low flow, to ‘wet‐year’ communities dominated by taxa adapted to high flows. The abundance of chironomid larvae was an important driver of community change. Directional change in community composition occurred at all sites and was correlated with precipitation patterns, with more dramatic change occurring in smaller streams. 3. All communities exhibited high to moderate persistence (defined by the presence/absence of a species) and moderate to low stability (defined by changes in abundance) over the study period. Stability and persistence were correlated with climatic variation (precipitation and El Niño Southern Oscillation) and stream size. Stability and persistence increased as a result of drought in small streams (first‐order) but decreased in larger streams (second‐ and third‐order). Communities from the dry season were less stable than those from the wet‐season. 4. This study demonstrates the importance of long‐term studies in capturing the effects of and recovery from rare events, such as the prolonged and extreme droughts considered here.     

Disappearance of glyceraldehyde 3-phosphate dehydrogenase from erythrocyte membrane by hemolysis with thermostable direct hemolysin of Vibrio parahaemolyticus or Vibrio cholerae El Tor hemolysin.

It is believed that the thermostable direct hemolysin (TDH) of Vibrio parahaemolyticus and El Tor hemolysin (ETH) of Vibrio cholerae damage erythrocytes and other cells by acting as pore-forming toxins. In this study, we found that a protein band with a molecular weight of 37,000 daltons specifically disappeared from erythrocyte membrane after hemolysis by TDH and ETH, but not after hypotonic hemolysis. The 37 kDa band was identified as glyceraldehyde 3-phosphate dehydrogenase (G3PD), a glycolytic enzyme, based on N-terminal 14 amino acid sequencing. The role of G3PD in hemolysis is discussed.     

Monoterpene ‘thermometer’ of tropical forest‐atmosphere response to climate warming

Tropical forests absorb large amounts of atmospheric CO₂ through photosynthesis but elevated temperatures suppress this absorption and promote monoterpene emissions. Using ¹³CO₂ labeling, here we show that monoterpene emissions from tropical leaves derive from recent photosynthesis and demonstrate distinct temperature optima for five groups (Groups 1–5), potentially corresponding to different enzymatic temperature‐dependent reaction mechanisms within β‐ocimene synthases. As diurnal and seasonal leaf temperatures increased during the Amazonian 2015 El Niño event, leaf and landscape monoterpene emissions showed strong linear enrichments of β‐ocimenes (+4.4% °C^?1) at the expense of other monoterpene isomers. The observed inverse temperature response of α‐pinene (?0.8% °C^?1), typically assumed to be the dominant monoterpene with moderate reactivity, was not accurately simulated by current global emission models. Given that β‐ocimenes are highly reactive with respect to both atmospheric and biological oxidants, the results suggest that highly reactive β‐ocimenes may play important roles in the thermotolerance of photosynthesis by functioning as effective antioxidants within plants and as efficient atmospheric precursors of secondary organic aerosols. Thus, monoterpene composition may represent a new sensitive ‘thermometer’ of leaf oxidative stress and atmospheric reactivity, and therefore a new tool in future studies of warming impacts on tropical biosphere‐atmosphere carbon‐cycle feedbacks.     

Anatomical differentiation of isolated scales of amiiform fishes (Amiiformes,Actinopterygii) from the Early Cretaceous of Las Hoyas (Cuenca,Spain)

The scales of amiiform fishes are more different from each other than previously stated. The anatomy of the scales of the three amiiform taxa from the Early Cretaceous (Barremian) of Las Hoyas (Cuenca, Spain) is described in detail. The differences between them has allowed the segregation of isolated scales form the fossil record of this site into the three taxa, providing relatively large population samples that can be studied from a palaeobiological and palaeoecological point of view.     

Potential effects of El Niño-South Oscillation (ENSO) on growth of the American crocodile, Crocodylus acutus (Crocodylia: Crocodilydae) in captivity

Temperature affects growth rate of crocodiles. However, no information exists about the effects of temperature by El Niño-South Oscillation (ENSO) on crocodiles. In this paper, we present information about the effect of ENSO on total length and body mass of Crocodylus acutus in captivity during 1997–2001. We did not observe differences in total length among years, but we did so in body mass. Furthermore, we observed that warm episodes of ENSO were associated with a higher average total length and cold episodes represented a higher average of body mass. Sea surface temperature (SST) was significantly related with total length; however, the relationship between SST and body mass was unclear. We suggest that ENSO effects on growth rates of crocodiles need to be considered as an important factor on the management of captive populations.     

When to worry about the weather: role of tidal cycle in determining patterns of risk in intertidal ecosystems

Species range boundaries are determined by a variety of factors of which climate is one of the most influential. As a result, climate change is expected to have a profound effect on organisms and ecosystems. However, the impacts of weather and climate are frequently modified by multiple nonclimatic factors. Therefore, the role of these nonclimatic factors needs to be examined in order to understand and predict future change. Marine intertidal ecosystems are exposed to heat extremes during warm, sunny, midday low tides. Thus, the timing of low tide, a nonclimatic factor, determines the potential contact intertidal invertebrates and algae have with heat extremes. We developed a method that quantifies the daily risk of high temperature extremes in the marine intertidal using solar elevations and spatially continuous tidal predictions. The frequency of 'risky days' is variable over time and space along the Pacific Coast of North America. Results show that at some sites the percentage of risky days in June can vary by 30% across years. In order to do a detailed analysis, we selected San Francisco as a study site. In San Francisco, May is the month with the greatest frequency of risky days, even though September is the month with the greatest frequency of high air temperature, ≥30 °C. These results indicate that marine intertidal organisms can be protected from high temperature extremes due to the timing of tides and local weather patterns. In addition, annual fluctuations in tides influence the frequency of intertidal zone exposures to high temperature extremes. Peaks in risk for heat extremes in the intertidal zone occur every 18 years, the length of the tidal epoch. These results suggest that nonclimatic variables can complicate predictions of shifts in species ranges due to climate change, but that mechanistic approaches can be used to produce predictions that include these factors.