Step-wise drops in modularity and the fragmentation of exploited marine metapopulations

Context

Many nearshore species are distributed in habitat patches connected only through larval dispersal. Genetic research has shown some spatial structure of such metapopulations and modeling studies have shed light onto possible patterns of connectivity and barriers. However, little is known about human impact on their spatial structure and patterns of connectivity.

Objectives

We examine the effects of fishing on the spatial and temporal dynamics of metapopulations of sedentary marine species (red sea urchin and red abalone) interconnected by larval dispersal.

Methods

We constructed a metapopulation model to simulate abalone and sea urchin metapopulations experiencing increasing levels of fishing mortality. We performed the modularity analysis on the yearly larval connectivity matrices produced by these simulations, and analyzed the changes of modularity and the formation of modules over time as indicators of spatial structure.

Results

The analysis revealed a strong modular spatial structure for abalone and a weak spatial signature for sea urchin. In abalone, under exploitation, modularity takes step-wise drops on the path to extinction, and modules breakdown into smaller fragments followed by module and later metapopulation collapse. In contrast, sea urchin showed high modularity variation, indicating high- and low-mixing years, but an abrupt collapse of the metapopulation under strong exploitation.

Conclusions

The results identify a disruption in larval connectivity and a pattern of collapse in highly modular nearshore metapopulations. These results highlight the ability of modularity to detect spatial structure in marine metapopulations, which varies among species, and to show early changes in the spatial structure of exploited metapopulations.

     

Identification of S-haplotypes of European cultivars of sour cherry

The sour cherry is known to exhibit the phenomenon of gametophytic self-incompatibility which prevents self-fertilization. In sour cherry, besides self-incompatible cultivars, there often occur self-compatible cultivars. This is due to the occurrence of natural mutations of the S-RNase or SFB genes and, consequently, loss of functionality of S-alleles. Here we present the results of the identification of S-haplotypes of 21 cultivars of sour cherry from various regions of Europe. The analyses were performed using methods based on the amplification of intron I and intron II of the S-RNase gene and fragments specific to the individual alleles of the S-RNase or SFB genes. The tested cultivars were found to contain 15 S-haplotypes: S₁, S_1?, S₄, S₆, S_6m, S_6m2, S₉, S₁₂, S₁₃, S_13?, S₂₆, S₃₅, S_36a, S_36b, and S_36b2. The most frequently occurring S-haplotypes were S_13? (61.9%), S_36a (57.1%), and S₂₆ (47.6%). On the basis of the results, 17 of the 21 cultivars were deduced to be self-compatible. The results will be of use in the production of sour cherry fruit by facilitating the selection of suitable pollinating cultivars. The results are also expected to be useful in the breeding of new cultivars of sour cherry when selecting genotypes for crosses.     

Effects of Pre-Stratification Storage Conditions on Black Walnut Seed Post-Stratification Germination Capacity

The objective of this work was to quantify changes in the germination capacity of Juglans nigra seeds following storage and then artificial stratification. Seeds were stored at 5 and –20 °C under 5% and 14% internal moisture content (IMC) for 0, 8, 10, and 12 months under conditions with oxygen or under vacuum. Germination percentage (GP) was affected by storage temperature, IMC, and storage period. Seeds stored with 5% IMC succeeded in germinating regardless of the temperature. Seeds stored with 14% IMC did not germinate (–20 °C) or germinated during storage (5 °C). The GP was reduced with the time of storage in seeds at –20 °C and 5% IMC and this effect was avoided in storage under vacuum. In conclusion, the germination capacity of black walnut seeds did not change for up to 12 months at low above-zero temperature and low IMC (5 °C, 5% IMC), being the most cost-effective alternative for long-term storage of black walnut seeds in commercial nurseries. Vacuum storage avoided the decrease of around 50% in average germination capacity of seeds stored for a year at –20 °C.     

Antioxidant Capacity of Beetroot: Traditional vs Novel Approaches

Red beetroot has been ranked among the 10 most potent antioxidant vegetables, although only extraction-based methods have been used to evaluate its total antioxidant capacity. Therefore, the present study aims at comparing the traditional extraction-based method with two more recent approaches (QUENCHER -QUick, Easy, New, CHEap and Reproducible- and GAR -global antioxidant response method), in order to establish their suitability in the case of beetroot. Our results indicate that the total antioxidant capacity of beetroot would be underestimated when using extraction-based procedures, since both QUENCHER and GAR methods resulted in a higher total antioxidant capacity. The effect of a thermal treatment on the total antioxidant capacity of beetroot varies among the methods evaluated and our findings suggest different compounds responsible for the total antioxidant capacity detected in each pre-processing method. Remarkably, the present study demonstrates that the traditional extraction-based method seems useful to screen for (changes in) the “bioavailable” antioxidant potential of the root.     

Analysis of genetic diversity among Macrophomina phaseolina (Tassi) Goid. isolates from Euro-Asian countries

Journal of Plant Diseases and Protection - The study assessed the genetic variability among Macrophomina phaseolina (Tassi) Goid. isolates originating from six different countries (Turkey,...     

Variance in leaf spot susceptibility in chestnut trees of different species and hybrids

Journal of Plant Diseases and Protection - Prior to the first occurrence of chestnut blight in 1976, leaf spot caused by Cylindrosporium castaneae was one of the most important diseases of European...     

Historical changes in land use influence current habitat preferences of large herbivores

Landscape Ecology - Predicting habitat use patterns is a key issue in the management of large herbivore populations. Particularly, indicators providing a model of the spatial distribution of a...     

Correction to: Individual based modelling of fish migration in a 2-D river system: model description and case study

Landscape Ecology - In the original publication of the article, the third author name has been misspelt. The correct name is given in this Correction. The original version of this article was revised.     

精准喷雾控制装置的设计与制作

为了实现精准喷雾,设计并制作了一套基于51单片机的精准喷雾自动/手动两种模式切换的控制装置。在自动模式下,单片机根据现场信号输入模块提供的作物病虫害情况分别打开或关闭对应的电磁阀;手动模式下,由面板手动开关分别控制各个电磁阀打开或关闭。经田间试验测定,该喷雾控制装置能够在自动或手动模式下实现精准喷雾作业控制。