Search

The article discusses the effects of social environments and life history traits on sex allocation in a haplodiploid spider mite. Topics include previous studies reveal that in haplodiploid species (i.e., whose fertilized eggs give rise to diploid female offspring and unfertilized eggs to haploid male offspring), life history traits such as the maternal age can also directly affect sex allocation due to the age-specific fertilization.

Tetranychus ludeni Zacher is a European spider mite species and an important invasive pest in horticulture. We investigated the effects of hot air on its survival and reproduction, providing knowledge for development of disinfestation programs using heat. We tested how each life stage responded to heat treatments of five air temperatures (45 to 57°C) and five exposure durations (three to 15 hours). We showed that no eggs hatched after exposed to 45°C for ≥ 15 hours, 48°C for ≥ 12 hours, or 51°C for three hours; no adults survived 51°C or 54°C for ≥12 hours or 57°C for ≥ six hours, and heat tolerance of other life stages fell in between. Higher temperature and longer exposure time also reduced developmental success and fecundity. These findings suggest that we may be able to eradicate the mites of all stages using one hot air treatment at 57°C for six hours or two treatments at 51°C for three hours at a 10-day interval to kill all eggs in the first treatment and those laid by survived adults in the second. The eradication strategy using hot air of 51–57°C may be more suitable for treating plant residues on exported/imported machinery, farm equipment and containers because it may have negative impact on fresh postharvest products. With the knowledge that exposure to 45°C substantially reduced the mites' fecundity, particularly when the younger stages were treated, we suggest that heat treatment of fresh postharvest products with 45°C could still greatly reduce the quarantine risk of this pest. [ABSTRACT FROM AUTHOR]

Animals can adjust reproductive strategies in favour of corporation or competition in response to local population size and density, the two key factors of social environments. However, previous studies usually focus on either population size or density but ignore their interactions. Using a haplodiploid spider mite, Tetranychus ludeni Zacher, we carried out a factorial experiment in the laboratory to examine how ovipositing females adjust their fecundity and offspring sex ratio during their early reproductive life under various population size and density. We reveal that females laid significantly more eggs with increasing population size and significantly fewer eggs with increasing population density. This suggests that large populations favour cooperation between individuals and dense populations increase competition. We demonstrate a significant negative interaction of population size and density that resulted in significantly fewer eggs laid in the large and dense populations. Furthermore, we show that females significantly skewed the offspring sex ratio towards female-biased in small populations to reduce the local mate competition among their sons. However, population density incurred no significant impact on offspring sex ratio, while the significant positive interaction of population size and density significantly increased the proportion of female offspring in the large and dense populations, which will minimise food or space competition as females usually disperse after mating at crowded conditions. These results also suggest that population density affecting sex allocation in T. ludeni is intercorrelated with population size. This study provides evidence that animals can manipulate their reproductive output and adjust offspring sex ratio in response to various social environments, and the interactions of different socio-environmental factors may play significant roles. [ABSTRACT FROM AUTHOR]

Life history strategies of a species may affect its invasion success. Here, we used a haplodiploid pest, Tetranychus ludeni Zacher (Acari: Tetranychidae), which is native to Europe but now cosmopolitan, to investigate its life history strategies in relation to its dispersal tendency and distance. We tested whether and how dispersal influenced survival, lifetime fecundity, age-specific reproduction, and life table parameters of mated females. We show that mated females did not trade off their survival and lifetime reproductive output with dispersal but adjusted their resource allocations during different reproductive stages depending on whether and how far they dispersed. Long-distance dispersers invested more in dispersal in their early life while resident mites and short-distance dispersers invested more in reproduction during their early life. These resource allocation strategies may allow long-distance dispersers to explore the novel environment more effectively without compromising lifetime reproductive fitness, contributing to the invasion success of T. ludeni. [ABSTRACT FROM AUTHOR]

Tetranychus ludeni Zacher is a spider mite that has invaded all continents except Antarctica and become an economically important pest around the world. Understanding the plasticity of its life history traits as a response to temperatures provides critical information for its risk analysis and management. Here we tested its response to temperatures ranging from 15 to 30°C over two generations. We found that there was no difference in the egg hatch rate and immature survival rate across temperatures in the first generation. However, the egg hatch rate was lower and immature survival rate was higher at 30°C in the second generation. The sex ratio (proportion of females) of resultant adults was consistent under all test temperatures in both generations except for 30°C in the second generation which was lower. Higher temperature accelerated development in both generations but the development at the lower temperatures was faster in the second generation. Adult body size in both generations generally decreased with the increase of temperature, with females being more likely than males to adjust body size in response to temperature changes they first experienced. Temperature-dependent body size was not translated into fecundity, but larger adults lived longer. The thermal threshold was lower and degree days (DD) were greater in the second generation than in the first generation. Our findings indicate that life history traits of T. ludeni are highly flexible and adaptive to dynamic thermal environment in successive generations. Furthermore, increasing temperature elevated the intrinsic rate of increase (rm) but shortened the generation time (T) and the time to double the population size (Dt). The net population growth rate (R0) was higher at 20 and 25°C as compared to lower and higher temperatures. [ABSTRACT FROM AUTHOR]

Tetranychus ludeni Zacher (Acari: Tetranychidae) is an invasive polyphagous haplodiploid pest mite of many vegetable crops in many parts of the world. This study investigated the effects of simultaneous variations in the local foundress population density and size on the reproduction and population growth of T. ludeni. We show that negative population-density and -size dependency limited the reproduction of foundresses, where the effects of population size on population growth overweighed that of population density. We further demonstrate that ovipositing females could accelerate population growth rate (intrinsic rate of increase, rm) at higher population sizes by producing more daughters early during their lifespan, which can be an adaptive strategy to allow more daughters to complete development and disperse to reduce future food competition intensity. This study provided knowledge on population dynamics in response to foundress population density and size in general and T. ludeni population forecast and precise timing of pest management in particular. [ABSTRACT FROM AUTHOR]

The article presents a study which analyzed the aspects of inbreeding in haplodiploid animals by using the spider mite Tetranychus ludeni (Zacher). Also cited are the possible effects of mating between relatives (inbreeding) like increased homozygosity, inbreeding depression, and inbreeding avoidance behavior, as well as the expected effects of inbreeding like changes in female-specific traits like fecundity and offspring sex allocation.

The article highlights the dynamics of life history traits in Tetranychus ludeni Zacher in response to fluctuating temperatures. It mentions Tetranychus ludeni Zacher as an invasive spider mite that currently occurs in Europe, Asia, Africa and also mentions the effects of constant temperatures on several spider mite species.