Founder effects persist despite adaptive differentiation: a field experiment with lizards

The extent to which random processes such as founder events contribute to evolutionary divergence is a long-standing controversy in evolutionary biology. To determine the respective contributions of founder effects and natural selection, we conducted an experiment in which brown anole (Anolis sagrei) lizard populations were established on seven small islands in the Bahamas, from male-female pairs randomly drawn from the same large-island source. These founding events generated significant among-island genetic and morphological differences that persisted throughout the course of the experiment despite all populations adapting in the predicted direction-shorter hindlimbs-in response to the narrower vegetation on the small islands. Thus, using a replicated experiment in nature, we showed that both founder effects and natural selection jointly determine trait values in these populations.     

Evaluation of the Karras Spermdensimeter in Relation to the Neubauer Counting Chamber for Sperm Concentration Measurement in Boar Semen

The correct measurement of spermatic concentration in boar semen is one of the basic tasks routinely performed at the Swine Artificial Insemination Center (CIAS). This article explains two experiments whose objectives were: Experiment 1: This trial had two objectives: (1) to evaluate the precision of the spermdensimeter (SPM) with relation to the Neubauer count chamber (CN) which is considered the standard technique in the field and (2) to correct the scale on the SPM table. Experiment 2: This trial also had two objectives: (1) to evaluate the time and repetitions required in the SPM and (2) to compare the SPM adjusted table produced in Expt 1 with the SPM standard table. The methods in Expt 1 were used to measure total spermatic concentration in 141 boar ejaculates. The average spermatic concentrations (10(6) spermatozoids/ml) and average dose number were 229.1 and 22.6 for CN, and 283.6 and 28.0 for SPM. These results indicate that the SPM has a tendency to overestimate spermatic concentration with relation to the CN. The SPM produced a smaller coefficient of variation and needed lesser examination time than the CN (p < 0.05). The SPM adjusted table created in Expt 1 produced similar results as the SPM and CN standard tables (2.96 billion live spermatozoids/dose vs 2.36 billion live spermatozoids/dose). Incorporation and evaluation of supplemental data from other CIAS regarding the use of the SPM adjusted table in the field entitled 'Adjusted Table for Karras Spermdensimeter LPS-FMVZ-USP' would be valuable to prove its efficiency.     

Marker-assisted increase of genetic diversity in a double-low seed quality winter oilseed rape genetic background

Generation of novel genetic diversity for maximization of heterosis in hybrid production is a significant goal in winter oilseed rape breeding. Here, we demonstrate that doubled haploid (DH) production using microspore cultivation can simultaneously introgress favourable alleles for double‐low seed quality (low erucic acid and low‐glucosinolate content) into a genetically diverse Brassica napus genetic background. The DH lines were derived from a cross between a double‐low quality winter rapeseed variety and a genetically diverse semisynthetic B. napus line with high erucic acid and high glucosinolates (++ quality). Twenty‐three low‐glucosinolate lines were identified with a genome component of 50–67% derived from the ++ parent. Four of these lines, with a genome component of 50–55% derived from the ++ parent, also contained low erucic acid. Heterosis for seed yield was confirmed in test‐crosses using these genetically diverse lines as pollinator. The results demonstrate the potential of marker‐assisted identification of novel genetic pools for breeding of double‐low quality winter oilseed rape hybrids.     

Integration Between Different Hypothalamic Nuclei Involved in Stress and GnRH Secretion in the Ewe

This study investigated possible integrated links in the neuroanatomical pathways through which the activity of neurones in the paraventricular nucleus and arcuate nucleus may modulate suppression of gonadotrophin‐releasing hormone (GnRH) secretion during stressful situations. Double‐label immunofluorescence and laser scanning confocal microscopy were used to examine the hypothalamic sections from the follicular phase ewes. Noradrenergic terminals were in close contact with 65.7 ± 6.1% corticotrophin‐releasing hormone (CRH) and 84.6 ± 3.2% arginine vasopressin (AVP) cell bodies in the paraventricular nucleus but not with β‐endorphin cell bodies in the arcuate nucleus. Furthermore, γ‐amino butyric acid (GABA) terminals were close to 80.9 ± 3.5% CRH but no AVP cell bodies in the paraventricular nucleus, as well as 60.8 ± 4.1%β‐endorphin cell bodies in the arcuate nucleus. Although CRH, AVP and β‐endorphin cell terminals were identified in the medial pre‐optic area, no direct contacts with GnRH cell bodies were observed. Within the median eminence, abundant CRH but not AVP terminals were close to GnRH cell terminals in the external zone; whereas, β‐endorphin cells and terminals were in the internal zone. In conclusion, neuroanatomical evidence is provided for the ewe supporting the hypothesis that brainstem noradrenergic and hypothalamic GABA neurones are important in modulating the activity of CRH and AVP neurones in the paraventricular nucleus, as well as β‐endorphin neurones in the arcuate nucleus. These paraventricular and arcuate neurones may also involve interneurones to influence GnRH cell bodies in medial pre‐optic area, whereas the median eminence may provide a major site for direct modulation of GnRH release by CRH terminals.     

Immunisation against ovine caseous lymphadenitis: correlation between Corynebacterium pseudotuberculosis toxoid content and protective efficacy in combined clostridial-corynebacterial vaccines

Groups of sheep were dosed with vaccines containing Corynebacterium pseudotuberculosis toxoid combined in varying amounts with 5 clostridial antigens. Resistance of the sheep to infection with C pseudotuberculosis was tested at 1, 6 and 12 months after vaccination by infection with pus from ovine lymph glands actively infected with C pseudotuberculosis. The outcome was assessed 3 months after challenge by slaughter and inspection of the sheep for caseous lymphadenitis lesions. Protection was demonstrated by a significant reduction in the proportion of immunised sheep exhibiting lesions compared with control sheep, and by fewer abscesses in affected immunised sheep than in affected control sheep. A positive correlation was found between amount of C pseudotuberculosis toxoid administered and degree of protection obtained. Chromatographically-purified toxoid induced essentially the same protection, suggesting that anti-toxic immunity is the major factor in protection.     

Insecticide Resistance: Effects of WARF Antiresistant on Toxicity of DDT to Adult Houseflies

Addition of N, N-dibutyl-p-chlorobenzene sulphonamide (Antiresistant/DDT) in amounts equal to one fifth the dose of DDT increased the toxicity of DDT to the DDT-resistant portion of a housefly population. Full susceptibility was not regained. There was no increase in toxicity to the DDT-susceptible portion.