Analysis of ancestry heterozygosity suggests that hybrid incompatibilities in threespine stickleback are environment dependent

Hybrid incompatibilities occur when interactions between opposite ancestry alleles at different loci reduce the fitness of hybrids. Most work on incompatibilities has focused on those that are “intrinsic,” meaning they affect viability and sterility in the laboratory. Theory predicts that ecological selection can also underlie hybrid incompatibilities, but tests of this hypothesis using sequence data are scarce. In this article, we compiled genetic data for F2 hybrid crosses between divergent populations of threespine stickleback fish (Gasterosteus aculeatus L.) that were born and raised in either the field (seminatural experimental ponds) or the laboratory (aquaria). Because selection against incompatibilities results in elevated ancestry heterozygosity, we tested the prediction that ancestry heterozygosity will be higher in pond-raised fish compared to those raised in aquaria. We found that ancestry heterozygosity was elevated by approximately 3% in crosses raised in ponds compared to those raised in aquaria. Additional analyses support a phenotypic basis for incompatibility and suggest that environment-specific single-locus heterozygote advantage is not the cause of selection on ancestry heterozygosity. Our study provides evidence that, in stickleback, a coarse—albeit indirect—signal of environment-dependent hybrid incompatibility is reliably detectable and suggests that extrinsic incompatibilities can evolve before intrinsic incompatibilities.

Genetic evidence for environment-dependent hybrid incompatibilities in threespine stickleback

Hybrid incompatibilities occur when interactions between opposite-ancestry alleles at different loci reduce the fitness of hybrids. Most work on incompatibilities has focused on those that are 'intrinsic', meaning they affect viability and sterility in the laboratory. Theory predicts that ecological selection can also underlie hybrid incompatibilities, but tests of this hypothesis are scarce. In this article, we compiled genetic data for F2 hybrid crosses between divergent populations of threespine stickleback fish (Gasterosteus aculeatus L.) that were born and raised in either the field (semi-natural experimental ponds) or the laboratory (aquaria). We tested for differences in excess heterozygosity between these two environments at ancestry informative loci—a genetic signature of selection against incompatibilities. We found that excess ancestry heterozygosity was elevated by approximately 3% in crosses raised in ponds compared to those raised in aquaria. Previous results from F1 hybrids in the field suggest that pond-specific (single-locus) heterosis is unlikely to explain this finding. Our study suggests that, in stickleback, a coarse signal of environment-dependent hybrid incompatibilities is reliably detectable and that extrinsic incompatibilities have evolved before intrinsic incompatibilities.

The influence of ecological conditions on the growing of fingerlings carp hybrids of different origin

The article presents an analysis of the ecological condition of reservoirs of the cultivation system of the State Enterprise «Lviv Research Station of the Institute of Fisheries NAAS» to create optimal conditions in ponds for growing carp hybrids of different genesis. It was found that the hydrochemical regime in the experimental ponds did not differ much because it mainly depended on the chemical composition of the water source of their water supply. In general, the main hydrochemical parameters that characterize the quality of pond water meet the standards for fishery reservoirs. According to OO Alokin’s classification, the water corresponded to a weakly alkaline or alkaline medium (7.0–9.1) and belonged to the hydrocarbonate class (HCO3 — 152.5–222.0 mg/dm3), with a predominance of SO42–, (69.2–72.8 mg/dm3), with an average mineralization in the range of 319.0–402.5 mg/dm3. Temperature indicators corresponded to seasonal dynamics and were in the range of 15–26°C, with the maximum value in July, while the content of dissolved oxygen in water did not fall below 2.43 mg·O/l. Phytoplankton of experimental ponds was represented by freshwater species (from 62 to 80) belonging to 7 systematic divisions. Chlorophyta 10450 dominated in number — 2836.79 thousand cells/dm3. Quantitative indicators of phytoplankton development were at the level of 2773.59–18496.62 thousand cells/dm3 by number and from 0.78 to 3.32 mg/dm3 by biomass. Zooplankton of experimental ponds was mainly represented by organisms of three systematic groups: Rotifera, Cladocera and Copepoda. At the time of the research, the quantitative indicators of zooplankton development in growing ponds ranged from 22.0 to 257.0 thousand specimens/m3 in number, and 0.36–19.1 g/m3 in biomass. The main role in the formation of zooplankton biomass was win back by young forms of branched crustaceans. The obtained indicators of the ecological condition of fish ponds will create optimal conditions for fish farming. Accordingly, they contribute to the positive physiological development of this year’s carp hybrids.

Nonlinear ecosystem responses to leaf litter subsidies in experimental ponds

Subsidies of matter between ecosystems can strongly affect trophic interactions in food webs, yet most experiments apply a binary (i.e., subsidy vs. no subsidy) approach. This emphasis on extremes implicitly assumes linear relationships and fails to capture potential nonlinear effects in ecosystem responses along gradients of subsidy amount seen in real systems. To examine the effects of such gradients, we manipulated leaf litter biomass across seven subsidy levels in 1000-L replicated experimental ponds. As our subsidy recipient, we used a simple food web that included southern leopard frog tadpoles (Rana sphenocephala) and spotted salamander larvae (Ambystoma maculatum) as the top vertebrates. We measured temperature, dissolved N and P; dissolved organic carbon (DOC); dissolved oxygen (DO); phytoplankton and periphyton biomass; and amphibian biomass export. Dissolved N, phytoplankton and periphyton biomass were linearly related to subsidy amount, but DOC, periphyton ash-free dry mass, and DO were nonlinearly related to subsidies. Frog biomass export increased as a function of subsidy amount, while salamander biomass export increased up to moderate subsidy levels before decreasing to very low levels at the highest subsidies, suggesting not only a nonlinear response, but a non-monotonic one. Our data suggest that under high subsidies, despite high nutrient levels, the basal resource supply may have switched from an algal to a detrital one. These data show that a dose-dependent approach is fundamental for understanding how subsidy amount affects ecosystems.

Effect of different amounts of feeds on growth and production of fishes in pond polyculture

An experiment was carried out to evaluate the effects of different amounts of supplementary feeds on growth and production of fishes in polyculture where four different species such as rui (Labeo rohita), mrigal (Cirrhinus mrigala), common carp (Cyprinus carpio) and tilapia (Oreochromis niloticus) were cultured in 6 ponds under three treatments, each with two replications. Eighty fish per decimal were stocked along with the stocking ratio of 1:1:1:1 in all the treatments. Supplementary feeds of rice bran and wheat bran (1:1), at the amount of 5% of body weight were applied in 2 ponds (treatment I) as well as at the amount of 3% of body weight were used in 2 ponds (treatment II) and 2 ponds (treatment III) were as control where no supplementary feed was used. Urea and T.S.P were applied fortnightly at the rate of 60 g decimal-1 and 90 g decimal-1, respectively under all treatments. Physico-chemical and biological factors such as air and water temperature, transparency, rainfall, pH, dissolved oxygen, free CO2, total alkalinity, PO4-P and NO3-N, phytoplankton and zooplankton were studied fortnightly and the limnological conditions were more or less similar in the experimental ponds under three treatments. The calculated gross and net fish productions of fishes under treatment I, treatment II and treatment III were 8.87 and 7.33 ton ha-1 yr-1, 7.12 and 5.58 ton ha-1 yr-1 and 4.69 and 3.16 ton ha-1 yr-1, respectively. Percent increased of net fish productions of treatment I and treatment II were 231.97% and 176.59% higher than that of treatment III (control). The present study reveals that supplementary feeding in fish culture should be done along with fertilization because supplementary feeds are very important to enhance growth of fishes significantly. Int. J. Agril. Res. Innov. Tech. 10(2): 128-136, December 2020

Forest edges and their effects on the arrival of dragonflies at north-temperate experimental ponds

The matrix, an environment in the landscape that individuals move through but do not reside in, can affect species dispersal and the arrival of individuals at habitat patches. Elements around this matrix that provide refuge or resources may shape the arrival of animals at habitat patches, even when those patches are equivalent in quality. Adult dragonflies (Odonata: Anisoptera) frequently use open terrestrial environments during movement and dispersal in north-temperate regions; however, they can also roost along forest edges. Because of the potential value of forest edges to adult dragonflies, we tested whether pond proximity (i.e., connectivity) to multiple forest edges was positively related to the abundance or diversity of arriving dragonflies. We observed dragonflies arriving at 9 experimental pond sites located within an open field landscape in Ontario, Canada. Experimental ponds differed in their distance to source ponds and to forest edges, a potential refuge for dragonflies. We found no effect of connectivity to forest edges or distance to source ponds on the abundance or diversity of dragonflies arriving at a site. Dragonfly dispersal was therefore not limited at the spatial scale of our study (<305 m to source ponds). In addition, dragonflies did not seem to discriminate among sites based on the amount of nearby forest edge, although all sites within the generally open landscape had at least some forest edge in close proximity (10–79 m). Our results provide greater insight regarding the decisions that dragonflies make in response to landscape elements while dispersing to reproductive habitats.

Intensive pond culture of Pangasius hypophthalmus in the Mekong Delta, Vietnam.

Silver striped catfish (Pangasius hypophthalmus), 'ca tra' in Vietnamese, has been cultured intensively in cages in the Mekong Delta, Vietnam, for at least 30 years, but pond culture of this species is traditionally semi-intensive. Recently, intensive pond culture of the species has been developed. A study of P. hypophthalmus intensive pond culture was conducted in Thotnot and Omon Districts, Cantho City. The stocking density is 10-20 fingerlings m-2. Fish are fed with both artificial and farm-made feed. After 6 months of culture, fish yields ranged from 189 to 212 t ha-1 in experimental ponds. With good water quality management, meat is white and suitable for export. Intensive pond culture of this catfish has high potential to increase aquacultural production and improve farmers' income in the Mekong Delta of Vietnam. Production from farmers' ponds range from 50 to 300 t ha-1 at stocking densities of 8-40 fingerlings m-2.

Integrated poultry-fish farming in Bangladesh.

The integration of fish culture with poultry raising holds great promise and potential for augmenting production of animal protein, betterment of the economy, and generation of employment in rural Bangladesh. In integrated poultry-fish farming, droppings of birds and feed wastes are recycled in ponds for production of fish. By raising 500 chickens in a poultry shed over a 1 hectare pond, a production of 4,000 kg-1 ha-1 yr-1 of fish was obtained. In addition, up to 240 eggs were obtained per bird per year. Broiler-fish is more profitable than layer-fish farming, as the broilers grow fast and are more marketable within 6-8 weeks, thus ensuring a quick cash return for the farmers. A significantly higher production of 4,290 kg-1 ha-1 yr-1 was observed from experimental ponds receiving poultry droppings directly compared to ponds fertilized with manure obtained from a separate source with a production of 3,365 kg-1 ha-1 yr-1.