The potential for biological control of stoats (Mustela erminea)

Abstract

Accelerating the mortality of stoats (Mustela erminea) using biological agents, or reducing their fertility using chemosterilants or biological agents, are increasingly seen as more sustainable and more humane than trapping and poisoning. Obligate delayed implantation in fertilised female stoats of all ages allows 10–11 months for an applied biological agent or chemosterilant to interfere with gestation. Two chemosterilants (cabergoline and mifepristone) disrupt pregnancy in some species and may be effective on stoats, although they are not species‐specific and are probably more expensive than poisoning. For the longer term, more recent fertility control research has explored potentially more species‐specific options for other species based on inducing an immune response to an animal's own reproductive hormones, gametes, or products from embryos. Conception will be difficult to disrupt in stoats because females are sexually mature and are mated in the nest during a short period before they are weaned. A large research effort will be required to determine which of the immunosterilants being developed could be suitable candidates for stoat control. There are fewer options apparent for using biological agents to increase stoat mortality, although species‐specific strains of canine distemper virus may be effective against stoats.

The greatest impediment to controlling stoat fertility will be effective delivery of sterilants. For the foreseeable future, it will probably be necessary to rely on baits, but they are unlikely to put all target stoats at risk, and will be incapable of delivery over larger scales than at present.

Before undertaking expensive field trials and development of anti‐fertility and biological agents, the effects of putative compensatory changes in demographics that may be associated with changes in stoat density should be modelled to see if the sterilisation and mortality rates that are required to achieve a given level of population control are realistic targets. Also, population control should be defined in terms of accrued benefit for wildlife by establishing the relationships between stoat densities and the viability of prey populations.

Biological control of fertility or mortality may never be suitable as stand‐alone control options for stoats, particularly when some native fauna survive only if stoats are reduced to very low densities. Biological control may have greater potential when integrated with conventional control.     

Population structure of Placostylus hongii (Gastropoda: Paryphantidae) on the Poor Knights Islands

Abstract

Populations of the native land snail Placostylus hongii (Lesson, 1830) on the Poor Knights Islands were investigated during visits in 1976, 1977, and 1978. Marking and recapture of individual snails showed that linear growth of the shell ceased when a lip was formed around the outer margin of the aperture. Measurements of snails suggested that increase in outer lip width was a good indication of age, but that the rate of lip thickening varied between populations. Large Placostylus showed a restricted range of movement. Both tagging studies and random sampling revealed that mortality was size specific. Most small snails (<60 mm shell length) located were dead, whereas most larger snails were alive. Population densities of living snails averaged 2.2 individuals per 0.25 m² in the study area. The local distribution was patchy owing to the tendency of snails to be associated with specific features of the vegetation.     

The population ecology of Rattus exulans on Tiritiri Matangi Island,and a model of comparative population dynamics in New Zealand

Abstract

On Tiritiri, a small predator-free island in northern New Zealand, kiore (Rattus exulans) were live and snap trapped in grassland and forest. In both habitats, kiore abundance peaked in late summer/autumn. The increase followed a 3 month breeding season during which females produced two to three litters, each averaging 7 young. During the population decline in autumn and winter, animals lost weight. Few bred in the breeding season of their birth and none lived to breed in a second breeding season, so the population consisted of distinct age cohorts. These patterns may relate to a highly seasonal food supply.

Kiore elsewhere in New Zealand show seasonal breeding, but the length of breeding, sexual maturation, and litter size vary. Other studies of kiore in the Pacific show less marked seasonal fluctuations, longer breeding seasons, and smaller litters. We propose a model to explain the variation in rodent demography in New Zealand. The model is based on the seasonal availability of food, along with the modifying influences of predation and dispersal.     

A new genus of Aeolothripidae (Thysanoptera) from New Zealand and New Caledonia

Desmidothrips n.gen. is described from New Zealand, with walkerae n.sp. as type‐species. Aeolothrips inauditus Bianchi from New Caledonia is transferred to this new genus. Desmidothrips is related to the Australian genus Desmothrips, and is the only member of the Aeolothripidae native to New Zealand.     

Changing use of camera traps in mammalian field research: habitats,taxa and study types

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The hMLH1 promoter polymorphisms and cancer susceptibility in Asian populations: A meta-analysis

Background

A variety of studies have evaluated the associations between polymorphisms in the promoter regions of the hMLH1 and cancer risk. However, the results remain inconclusive. To better understand the roles of the hMLH1 polymorphisms and cancer risk, we conducted a comprehensive meta-analysis to investigate the association between the hMLH1 − 93G/A and 1151T/A (Val384Asp) polymorphisms and cancer risk in Asian population.

Methods

We performed a meta-analysis by conducting searches of the published studies in Pub Med, CNKI, CBM, ISI web of knowledge and Google scholar search databases. Finally, 12 studies were included into our meta-analysis. Overall and subgroup analyses were performed. Odds ratio (OR) and 95% confidence interval (CI) were used to evaluate the associations between hMLH1 polymorphisms and cancer risk. Statistical analysis was performed with Review Manager 5.0.

Results

Twelve studies addressing two hMLH1 polymorphisms were analyzed among a total of 4128 cancer cases and 4678 controls. For hMLH1 − 93G/A, there was no evidence that the hMLH1 − 93G/A polymorphism was significantly associated with an increased cancer risk (P > 0.05) in Asian populations (heterozygote comparison: OR = 0.89 [95% CI (0.75, 1.060)] P = 0.20; dominant model comparison: OR = 0.98 [95% CI (0.83, 1.15)] P = 0.79). In subgroup analysis based on cancer types and the sources of control, no associations were found in colorectal cancer, gastric cancer and “other cancers” under the any gene model except for lung cancer (recessive model comparison: OR = 1.69 [95% CI (1.30, 2.19)] P < 0.0001). For hMLH1 1151T/A, the polymorphism significantly associated with an increased cancer risk in Asians: OR = 1.88 [95% CI (1.49, 2.25)], P < 0.0001, and OR = 1.87 [95% CI (1.49, 2.25)], P < 0.0001.

Conclusions

Our investigations demonstrated that the hMLH1 − 93G/A polymorphism is not a candidate for susceptibility to overall cancers, and that the hMLH1 1151T/A polymorphism is significantly associated with higher cancer risk in Asian populations. Further studies with large sample size for hMLH1 should be conducted.     

Evaluation of glutathione S-transferase genetic variants affecting type 2 diabetes susceptibility: A meta-analysis

Genetic polymorphisms of glutathione S-transferases (GSTs) and type 2 diabetes mellitus (T2DM) risk have been widely studied, however, the results were somewhat conflicting. To evaluate the association of GSTs (GSTM1, GSTT1 and GSTP1) gene polymorphisms with T2DM, a meta-analysis was performed before October, 2012. ORs were pooled according to random-effects model. There were a total of 1354/1666 (n = 9) cases/controls (studies) for GSTM1, 1271/1470 (n = 8) for GSTT1, and 1205/1250 (n = 7) for GSTM1. There were significant associations between GSTM1 polymorphism, GSTT1 polymorphism and T2DM in the contrast of present genotype vs. null genotype, with pooled OR = 1.99 (95%CI = 1.46–2.71) and OR = 1.61 (95%CI = 1.19–2.17), respectively. Yet no significant association of GSTP1 polymorphism and T2DM was showed. When stratified by ethnicity, the significant associations were also existed in Asians for GSTM1 and GSTT1, but not GSTP1. No publication bias but some extent of heterogeneity was observed. Finally, the accumulated evidence proved the obvious associations of GSTM1 and GSTT1 polymorphisms with an increased risk of T2DM.     

Short-lived corpora lutea syndrome in anoestrous ewes following 17β-oestradiol or MAP treatments applied before an allogenic sexual stimulation with rams and oestrous ewes

When induced to ovulate during anoestrus, ewes, does and cows frequently develop a short-lived corpora lutea (SLCL) syndrome associated to lack of previous progesterone. Exogenous progesterone precludes SLCL by blocking oxytocin endometrial receptors, thus inducing normal life-span CL (NLCL). Paradoxically, circa 50% of unprimed ewes do not develop SLCL. We report results from 3 trials assessing follicular, oestrous, ovulatory, and luteal end-points after 17β-oestradiol or MAP treatments. Oestradiol benzoate (50 μg) induced follicular turnover, provoked ovulation in 40% (24/60) of ewes treated (93% of which developed SLCL), but did not affect the incidence of SLCL (26/53) after an allogenic sexual stimulation (ASS) by rams and oestrous ewes. By the onset of the ASS, most NLCL ewes (26/27) had already experienced turnover of their largest follicle, had smaller largest and second largest follicles, and ovulated their largest follicle more frequently than SLCL ewes did. Most SLCL ewes (19/25) did not ovulate their largest follicles, ovulating instead smaller follicles of identical size to those of NLCL ewes. Priming (40 mg of MAP for 12 days) was partially effective at preventing SLCL even when terminated 14 days in advance of an ASS, but failed at completely preventing SLCL when terminated 6 or more days in advance. The coupling of a timed acquisition of full steroidogenic capability before ovulation with a system of endometrial oestradiol–progesterone–oxytocin receptors linked in an unstable equilibrium controlling the amplification of the luteolytic feed-forward loop of oxytocin and prostaglandin F₂α explains occurrence and relative incidences of both NLCL and SLCL, and links proximate and ultimate causes of the SLCL syndrome.     

Genes alternations with exposure time of environmental factors

A theoretical model discussing the environmental factors (EFs) effect of exposure time on genes, which leads to human diseases, is presented using multi-logistic model. The advantages and limitations of this model are discussed in terms of its usefulness for simulating genetic samples. It has been shown that EFs affect genes with the same degree both at high exposure level, low exposure time and at low exposure level, high exposure time.     

丛枝菌根真菌在外来植物入侵演替中的作用与机制

外来植物入侵不仅是环境、经济和社会问题,也是一个生理学和生态学问题,尤其是入侵植物与本地植物、入侵植物和本地土壤生物之间的相互作用决定外来植物入侵程度。丛枝菌根真菌（AMF）作为土壤中一类极为重要的功能生物,在外来植物入侵演替过程中发挥多种不同作用。文章系统总结了AMF对入侵植物个体和群体的影响,入侵植物与本地植物竞争中AMF发挥的促进和抑制作用;探讨了AMF与入侵植物的相互作用关系,以及环境因子对AMF一入侵植物关系的影响：对AMF在外来植物入侵演替中的作用机制进行了讨论。旨在为探索控制生物入侵的新途径、为我国开展外来植物入侵研究与防控实践提供新思路。