Ploidy composition in all-hybrid frog populations in relation to ecological conditions

Question: What explains the differences in ratios of diploid (LR) and two types of triploid frogs (LLR, LRR) among all-hybrid frog populations? Hypothesis: Ecological conditions favouring one (LL) or the other (RR) parental species also favour those triploids that carry two copies of the respective genome (dosage effect), whereas diploids dominate under intermediate conditions. Organism: European water frog (Pelophylax esculentus). Field site: Thirty-four natural ponds in the province of Skåne, southern Sweden. Methods: We caught more than 3000 frogs, determined their genotypes with microsatellites, and related the ploidy composition to several uncorrelated ecological parameters, including pond morphology, vegetation, and physical and chemical water parameters. Conclusions: We found a shift from predominantly LLR in small isolated ponds to more LRR in large wetland ponds. This parallels the preferences of the parental species LL and RR for small and large bodies of water, respectively. The effects that pond vegetation and physico-chemical water parameters exert on the parental species were not found in all-hybrid populations. This suggests that environmental parameters affect the genotype composition of all-hybrid populations less than populations containing the parental species. Pond-to-pond differences in LR, LLR, and LRR proportions seem to be better explained by differences in gamete production and thus inheritance patterns

The influence of food and temperature on population density of wild boar Sus scrofa in the Thurgau (Switzerland)

During the last two decades, populations of the wild boar Sus scrofa in Europe have increased considerably and the species has spread into new areas over the entire continent. Because of the animals' impact on agriculture, livestock and biodiversity, and the resulting necessity of realistic management practices, we were interested in the key environmental factors responsible for this remarkable development. The study was based on data from the canton Thurgau, a region in north-eastern Switzerland. We used data on damage and hunting success to calculate a population density index and related it to eight variables describing ecological conditions, demography and hunting pressure (measured by the number of hunters) over a 25-year period. The analysis shows that the population increase correlates with higher than average winter and spring temperatures and improved food supply through more mast years and an increase in the area of maize cultivation. While favourable temperature conditions mainly reduce juvenile mortality, enhanced food availability is likely to boost reproductive success through younger age at first reproduction, larger litter size and earlier onset of oestrus within a season. Given this link between food and reproduction, supplemental feeding, a management practice recommended and very common all over Europe, should be reconsidered

Relationships between food resources, foraging patterns, and reproductive success in the water pipit, Anthus sp. spinoletta

A basic but rarely tested assumption in optimal foraging theory is that positive relationships exist between the foraging pattern of an animal, its short-term benefits in feeding, and its long-term fitness. We present evidence for these relationships for a central place foraging situation. We studied the foraging behavior of adult water pipits (Anthus sp. spinoletta) feeding nestlings in an Alpine habitat near Davos, Switzerland, with the following results: (1) searching effort decreases with increasing distance from the nest, (2) the amount of prey and the proportion of large items brought to the nest increases with increasing foraging distance, (3) water pipits do not forage according to habitat availability, but prefer vegetation types with the highest food density (mainly grass and herbs) and avoid those with the lowest, and (4) this selectivity is only expressed when the birds forage more than 50 m from the nest, i.e., usually outside the territory. Among the several potential interpretations of these results, the most parsimonious is that foraging decisions are based on profitability, i.e., on the net energy gain per time unit. Additionally, we found that food conditions translate into fitness: the number of fledglings per nest is related positively to the average prey biomass at the foraging place and negatively to the average distance between the foraging place and the nest. Maximum economic distances, which were predicted from this food-fitness relationship, agreed well with the actual foraging distances observed. This suggests a dose connection between foraging decisions and fitness. In addition to the theoretical issues, some conservation issues are also briefly discusse

Thermal and energetic consequences of nest location and breeding times in Water Pipits (Anthus spinoletta).

The thermal environment has pronounced effects on the energy costs of thermoregulation and affects an animal's allocation of energy to self-maintenance and parental care. Consequently, the selection of reproductive periods, breeding habitats and nest-sites with a favourable microclimate can be advantageous, especially for birds breeding in harsh environments. In this study on Alpine Water Pipits (Anthus spinoletta), we evaluate the importance of spatial and temporal factors on thermoregulatory costs by combining laboratory measurements of metabolic rates under various temperatures with standard operative temperatures (Te~) recorded in the field in different microhabitats. Using these measurements we estimate the thermal and energetic consequences of nest locality and timing of reproduction. Our results show: (1) In the morning, Te~ values were much higher on the east-north-east (ENE) slope of a valley than on the west-south-west (WSW) slope; in the afternoon this pattern was reversed. As a consequence, energy costs (Ehour) for thermoregulation on the ENE slope were up to 0.6 RMR (resting metabolic rate at night) lower than on the WSW slope during morning hours and about 0.8 RMR higher during afternoon hours. (2) During the incubation and nestling phases of first and second broods, total energy expenditure for thermoregulation in the daytime (Edaytime) was 0.2-0.3 RMR higher on the ENE slope than on the WSW slope. (3) Within slopes, Edaytime was lower during second broods than during first broods, with differences of 0.06-0.07 RMR during incubation and of 0.32 RMR during nestling care. These differences correspond to the flying costs of females incubating eggs (0.09 RMR) and rearing nestlings (0.25 RMR). We conclude that nest placement in relation to microclimate can improve the female's energy budget, both in terms of the total daily expenditure and its diurnal pattern. From thermal considerations alone, delaying breeding into mid-summer would be advantageous, but this advantage is probably outweighed by the reduced chances for second and replacement clutches and by the necessity to complete moult before migration

Reproductive ecology of Bombina variegata: aspects of life history

Individual reproductive behaviour and survival of Bombina variegata was studied in a dynamic habitat with a variety of rain-filled ponds from 1990 to 1992. Most animals reached sexual maturity at the age of two years. Annual adult survival was at least 62%. Individual females, on average, laid between 40 and 70 eggs per "clutch". While about 12% of the breeding females spawned a second time within the season, a similar proportion did not seem to spawn every possible year, probably depending on climatic conditions. The results are consistent with ultimate predictions from life history theory, but the proximate mechanisms of ovulation and spawning in response to environmental conditions remain to be investigated

Variation in fertilisation abilities between hemiclonal hybrid and sexual parental males of sympatric water frogs (Rana lessonae, R. esculenta, R. ridibunda)

In many species, males and females mate with multiple partners, which gives rise to sperm competition and multiple paternity. The experiments on water frogs presented here demonstrate that such sperm competition can affect the structure and dynamics of mixed species communities. The hybrid frog Rana esculenta (LR) mates with one of its parental species, usually Rana lessonae (LL) although in some areas R. ridibunda (RR), to regain the premeiotically eliminated parental genome ("hybridogenesis"). Mixed LL/LR-populations are stable although hybrid numbers should continuously increase at the expense of parental animals, because of differences in female fecundity and other factors. This would finally lead to the extinction of the sexual host, followed by that of the sexual parasite, unless the reproductive superiority of R. esculenta is reduced by other factors, such as lower hybrid male fertility. Eggs from LL- and LR-females were fertilised in vitro by single- and multi-male sperm suspensions of LL-, LR- and RR-males. In all experiments, the proportion of offspring sired by R. esculenta sperm was significantly lower than that sired by R. lessonae or R. ridibunda sperm. Gonad mass, sperm morphology, sperm swimming velocity, and sperm survival did not explain these differences in fertilisation success, nor did gamete recognition and compatibility. Sperm density was the only trait that paralleled fertilisation success; but it offers no explanation either, because densities were equalised for the in vitro fertilisations. In natural LL/LR populations, the significantly smaller amount, poorer competitive ability and lower long-term survival of R. esculenta compared to R. lessonae sperm will reduce the initial reproductive superiority of hybrids and contribute to the stabilisation of mixed water frog populations. Differences in fertilisation ability are also likely to be relevant for the structure and dynamics of several other systems with encounters between eggs and sperm from different genotypes, ecotypes, ploidy levels and/or species

Genome-wide landscape of runs of homozygosity and differentiation across Egyptian goat breeds

: Understanding the genomic features of livestock is essential for successful breeding programs and conservation. This information is scarce for local goat breeds in Egypt. In the current study, genomic regions with selection signatures were identified as well as runs of homozygosity (ROH), genomic inbreeding coefficients (FROH) and fixation index (FST) were detected in Egyptian Nubian, Damascus, Barki and Boer goat breeds. A total of 46,268 SNP markers and 337 animals were available for the genomic analyses. On average, 145.44, 42.02, 87.90 and 126.95 ROHs were detected per individual in the autosomal genome of the respective breeds. The mean accumulative ROH lengths ranged from 46.5 Mb in Damascus to 360 Mb in Egyptian Nubian. The short ROH segments (< 2 Mb) were most frequent in all breeds, while the longest ROH segments (> 16 Mb) were exclusively found in the Egyptian Nubian. The highest average FROH was observed in Egyptian Nubian (~ 0.12) followed by Boer (~ 0.11), while the lowest FROH was found in Damascus (~ 0.05) and Barki breed (~ 0.03). The estimated mean FST was 0.14 (Egyptian Nubian and Boer), 0.077 (Egyptian Nubian and Barki), 0.075 (Egyptian Nubian and Damascus), 0.071 (Barki and Boer), 0.064 (Damascus and Boer), and 0.015 (Damascus and Barki), for each pair of breeds. Interestingly, multiple SNPs that accounted for high FST values were observed on chromosome 6 in regions harboring ALPK1 and KCNIP4. Genomic regions overlapping both FST and ROH harbor genes related to immunity (IL4R, PHF23, GABARAP, GPS2, and CD68), reproduction (SPATA2L, TNFSF12, TMEM95, and RNF17), embryonic development (TCF25 and SOX15) and adaptation (MC1R, KDR, and KIT), suggesting potential genetic adaptations to local environmental conditions. Our results contribute to the understanding of the genetic architecture of different goat breeds and may provide valuable information for effective preservation and breeding programs of local goat breeds in Egypt