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L Engqvist

Publications and source records attributed to L Engqvist.

7 recordsLinked to original sources
PubMed2006

Theoretical influence of female mating status and remating propensity on male sperm allocation patterns.

Theoretical models predict that males should allocate more sperm in matings where the immediate risk of sperm competition is high. It has therefore often been argued that males should invest less sperm in matings with virgin females compared with matings with already mated females. However, with relatively polyandrous females, high sperm competition risk will covary with high sperm competition intensity leading to more unpredictable conditions, as high competition intensity should favour smaller ejaculates. With the use of a genetic algorithm, we found that males should allocate more sperm in matings with virgin females when female mating frequency is relatively high, whereas low remating rates will select for higher effort in matings with nonvirgin females. At higher remating rates, first male sperm precedence favours larger ejaculates in matings with virgin females and second male precedence favours the reverse. These results shed some light on several findings that have been difficult to explain adaptively by the hitherto developed theory on sperm allocation.

Algorithms↗
PubMed2005

Pitfalls in experiments testing predictions from sperm competition theory.

As females of many species mate with more than one male, ejaculates often face competition from the sperm of other males. In recent years, numerous papers have been published on theoretical predictions of evolutionary, behavioural and physiological responses to variation in the strength of sperm competition (SC). These theoretical predictions have also been extensively tested. However, although predictions from SC theory are relatively straightforward, extra caution has to be paid in the design of experiments testing them. One difficulty is for example to disentangle immediate and mean SC risk and intensity. Without carefully designed experiments, it is also very easy to simultaneously increase SC risk and the probability of intense SC--a situation for which we currently have no clear predictions, as the theoretical models to date only assume variation in either SC risk or intensity. In this paper, we discuss these and some other pitfalls related to manipulations of SC risk and intensity and suggest how to avoid them.

Adaptation, Physiological↗
PubMed2003

Determinants of sperm transfer in the scorpionfly Panorpa cognate: male variation, female condition and copulation duration.

Recent studies suggest that sperm production and transfer may have significant costs to males. Male sperm investment into a current copulation may therefore influence resources available for future matings, which selects for male strategic mating investment. In addition, females may also benefit from actively or passively altering the number of sperm transferred by males. In the scorpionfly Panorpa cognata, the number of sperm transferred during copulation depended on copulation duration and males in good condition (residual weight) copulated longer and also transferred more sperm. Moreover, sperm transferred and stored per unit time was higher in copulations with females in good condition than in copulations with females in poor condition. Males varied greatly and consistently in their sperm transfer rate, indicative of costs associated with this trait. The duration of the pairing prelude also varied between males and correlated negatively with the male's sperm transfer rate, but no other male character correlated significantly with male sperm transfer rate. The results are consistent with strategic mating effort but sperm transfer could also be facilitated by the physical size of females and/or females in good condition may be more cooperative during sperm transfer.

Adaptation, Physiological↗
PubMed2001

Strategic male mating effort and cryptic male choice in a scorpionfly.

In animal species with high male mating effort, males often find themselves in a dilemma: by increasing their mating effort, the gain from each copulation increases but simultaneously reduces available resources and, thus, the opportunity for future copulations. Therefore, we expect males to spend less reproductive resources on matings that provide low reproductive potential, thereby saving resources for future copulations, possibly with high-quality females, a sort of cryptic male choice. However, the strength of the trade-off between investment in a current mating and resources available for future matings must not be the same for all males. Males with relatively high mating costs should allocate their limited resources more cautiously than males with more plentiful resources. Here, we examine this prediction in the scorpionfly Panorpa cognata. Prior to copulation, males produce a large salivary mass on which females feed during copulation. We show that the production of larger salivary masses leads to longer copulations. Moreover, the size of the salivary gland and salivary mass increases with increasing male condition. However, males in poor condition make a relatively higher mating investment than males in good condition. We therefore expect male condition to influence cryptic male choice. In accordance with our hypothesis, only males in poor condition choose cryptically, producing larger salivary masses in copulations with females of high fecundity.

Animals↗
PubMed1999

Meiotic drive and evolution of female choice.

As a special version of the good-genes hypothesis, it was recently proposed that females could benefit from choosing drive-resistant males in a meiotic drive system. Here, we examine with a three-locus, six-allele population genetic model whether female choice for drive resistance can evolve. An allele leading to female preference for drive-resistant males was introduced at low frequency into a population polymorphic for meiotic drive and drive resistance. Our simulations show that female choice of drive-resistant males is disadvantageous when resistance is Y-linked. This disadvantage occurs because, at equilibrium, drive-resistant males have lower reproductive success than drive-susceptible males. Thus, female choice of drive-susceptible males can evolve when resistance is Y-linked. When resistance is autosomal, selection on female choice for drive resistance is less strong and depends on the frequency of choice: female preference of resistant males is favoured when choice is rare and disadvantageous when choice is frequent, leading to a stable equilibrium at a low frequency of the choice allele. Independent of the location of drive resistance alleles, males with the non-driving allele always have above average reproductive success. Female choice is therefore beneficial when choosy females prefer males with the non-driving allele.

Animals↗
PubMed1999

Long-term effects of diltiazem and atenolol on blood glucose, serum lipids, and serum urate in hypertensive patients. Swedish-Finnish Study Group.

UNLABELLED: The purpose of this long-term treatment study was to evaluate health-related quality of life by comparing the effects of diltiazem and atenolol on some important metabolic parameters. SUBJECTS, MATERIAL AND METHODS: In a Swedish-Finnish long-term multicenter study 256 patients with mild to moderate hypertension were randomized to treatment with diltiazem retard (D) (n = 127) or atenolol (A) (n = 129). Doses could be increased and additional captopril medication be given to achieve adequate blood pressure (BP) reduction. The treatment in group D lasted for two years while group A was treated for 1 year and then was given D for another 2 years. RESULTS: After 1 year BP was significantly reduced in both groups and to a similar degree. The BP reduction was maintained during the rest of the study. After 1 and 2 years, HDL had increased significantly (p < 0.001) in group D. There was a corresponding significant reduction of the LDL/HDL ratio. In group A there were no changes after 1 year regarding lipoprotein levels. After the switch to D, group A showed similar improvements regarding HDL and the LDL/HDL ratio as the original D group. CONCLUSION: It is concluded that D and A are equally effective in lowering BP. However, long-term treatment with D, but not with A, has a favorable effect on HDL concentrations and the LDL/HDL ratio. According to these findings D affects the risk factor profile in hypertension.

Adult↗