Ecological and Genetic Determinants of the Expansion of Grey Squirrel Populations in Italy and Britain

入侵物种是对全球生物多样性的主要威胁，与人类的引入有着广泛的联系。美国灰松鼠在多次被引入欧洲后，对英国、意大利和爱尔兰的本地红松鼠数量产生了巨大影响，导致红松鼠的活动范围发生了重大变化。此外，英国的灰松鼠通过将种植园中的树木剥离，对农业工业产生了重要影响。该物种被认为可能会从意大利广泛扩散，取代红松鼠，并损害整个欧洲的农业工业。在最坏的情况下，模型预测意大利灰松鼠将在20-30年内扩张到法国和瑞士。假设。然而，灰松鼠的扩张模型已经被近似地参数化，意大利、英国和爱尔兰的灰松鼠种群由于未知的原因以显著不同的速度扩张。这些种群来自非常不同数量的引进个体(因此具有不同的遗传多样性)，并受到不同的生态环境的影响。红松鼠的体重减少和招募与灰鼠的存在有关。由于与灰猩猩的竞争，与之相关的红种种群数量的下降被一种对红猩猩致命的痘病毒病加剧，但这种疾病是由灰猩猩携带的，并且对灰猩猩无害。痘病毒在英国存在，在意大利没有，这表明英国的扩张速度快于意大利的假设，因为痘病毒杀死了当地的红军，消除了一个否则会减缓灰军前进的竞争对手。然而，竞争很可能是不对称的；还没有证明与红色的竞争会降低灰色的关键比率。另一种假说是，与英国种群相比，低遗传变异和近亲交配衰退减缓了意大利灰松鼠种群的增长。在一项关于入侵物种的大型研究中，创始人种群规模被确定为入侵成功的关键因素；英国灰松鼠的创始人种群规模比意大利要大得多。这项研究的主要目的是验证这些假设，这里重申：1)意大利和英国灰松鼠的不同扩张速度主要是由于灰松鼠面临的不同竞争环境，部分原因是来自红松鼠的竞争在英国被痘病毒消除或减少。2)不同的扩张率主要是由于意大利和英国灰松鼠种群的遗传多样性水平不同所致。将评估这两个因素对增长率的相对贡献。结果可能会对管理产生重大影响。方法：研究方法。方法将包括对意大利和英国松鼠的DNA样本进行微卫星分析，以及在两个意大利和两个英国松鼠地点进行诱捕计划和其他实地工作，两个国家分别有一个只有灰色松鼠，一个有灰色和红色松鼠。管理方面的影响。如果意大利灰松鼠的扩张率受到低遗传多样性的强烈限制，那么重要的是防止三个独立的意大利种群合并，从而增加多样性和加快扩张速度。这可以通过根除这两个人口来实现，这两个人口仍然足够小，可以根除。防止所有进一步的引入也是至关重要的，即使是几只松鼠也是如此。如果扩张速度受到来自红松鼠的竞争的限制，那么防止痘病毒传入意大利将是至关重要的。基于模型的扩张模式估计是保护政策的重要工具。建议的研究可能有助于更精确地将模型参数化，并增加未来保护行动的有效性。

Invasive species are a major threat to global biodiversity and are widely associated with human introductions. The American Grey squirrel, following multiple introductions into Europe, has had a massive impact on native red squirrel populations in the UK, Italy and Ireland, causing major shifts in the red squirrel's range. In addition, grey squirrels in the UK have had an important impact on agroindustry by debarking trees in plantations. The species is seen as likely to disperse widely from Italy, displacing red squirrels and harming agroindustry across Europe. Under a worst-case scenario, models predict the expansion of Italian grey squirrels into France and Switzerland within 20-30 years. Hypotheses. However, models of grey squirrel expansion have been parameterized approximately, and Italian, British and Irish populations of grey squirrels have expanded at substantially different rates for unknown reasons. These populations originated from very different numbers of introduced individuals (and hence have different genetic diversity), and are subject to different ecologies. Reduced red squirrel body mass and recruitment has been linked to the presence of greys. Associated declines in red populations due to competition with greys are accentuated by a poxvirus disease lethal to reds, but carried by and not harmful to greys. The poxvirus is present in the UK and absent from Italy, suggesting the hypothesis that UK expansion is faster than in Italy because poxvirus kills local reds, eliminating a competitor that otherwise would slow the greys' advance. However, competition could well be asymmetrical; it has not been demonstrated that competition with reds reduces the vital rates of greys. An alternative hypothesis is that low genetic variation and inbreeding depression slows the growth of the Italian grey squirrel population, relative to British populations. In a large study of invasive species, founder population size was identified as a key factor in invasive success; the founder population sizes of grey squirrels in the UK were much larger than those in Italy. The main goal of the research is to test these hypotheses, restated here: 1) Different expansion rates of grey squirrels in Italy and Britain are due primarily to different competitive environments faced by the greys, partly because competition from reds is eliminated or reduced by pox virus in the UK. 2) Different expansion rates are due primarily to different levels of genetic diversity in the grey squirrel populations in Italy and the UK. The relative contributions of both factors to expansion rates will be assessed. Results may have major management implications. Methods. Methods will include microsatellite analysis of DNA samples from Italian and British squirrels, and trapping programs and other field work at two Italian and two British sites, one in each country with greys only, and one with greys and reds. Management implications. If expansion rate of grey squirrels in Italy is strongly limited by low genetic diversity, it will be important to prevent the three separate Italian populations from merging and thereby increasing diversity and speeding expansion rate. This could be accomplished by eradicating the two populations which are still small enough for eradication. It would also be essential to prevent all further introductions, even of a few squirrels. If expansion rate is limited by competition from red squirrels, it will be essential to prevent the introduction of poxvirus into Italy. Model-based estimates of expansion patterns are an important tool for conservation policy. The proposed research may help to parameterize models more precisely and increase effectiveness of future conservation actions.