The use of olfactory and visual cues in host choice by the capsid bugs Lygus rugulipennis Poppius and Liocoris tripustulatus fabricius.

Lygus rugulipennis Poppius and Liocoris tripustulatus Fabricius (Heteroptera: Miridae) are pests of glasshouse cucumber and sweet pepper crops respectively. L. rugulipennis has a wide range of foodplants, but L. tripustulatus is specialised with very few food plants. We report behavioural assessments to investigate whether either species exhibits a preference for salad over wild hosts, and whether the role of olfaction and vision in response to cues from host plants can be distinguished. Olfactory responses to leaves were tested in choice chambers. L. rugulipennis was presented nettle (wild host) and a salad leaf of cucumber or sweet pepper, where the salad leaves had higher nitrogen content. L. tripustulatus was tested with nettle and sweet pepper of two different nitrogen contents. Female L. rugulipennis spent more time on the cucumber salad host, and chose it first most often, but males showed no preference. Neither sex discriminated between sweet pepper or nettle leaves, but males made more first contacts with sweet pepper. Neither sex of L. tripustulatus discriminated between sweet pepper and nettle leaves when the sweet pepper had higher nitrogen. When the plant species contained equivalent nitrogen both sexes spent more time on nettle. There was no difference in first choice made by either sex. When visual stimuli were available, and leaves had equivalent nitrogen, L. rugulipennis showed no preference and L. tripustulatus preferred nettle leaves. We conclude that the generalist L. rugulipennis has the ability to use remote olfactory cues for host choice whereas the specialist L. tripustulatus relies mainly on contact chemosensory and gustatory cues

Total percentage nitrogen in experimental leaves offered to <i>Liocoris tripustulatus.</i>

<p><i>Post hoc</i> comparisons (Fisher's pairwise comparisons) showed that the nettle leaves had significantly lower total percentage nitrogen than ‘high nitrogen’ pepper. There was no significant difference in total percentage nitrogen between nettle and ‘low nitrogen’ pepper leaves.</p

<i>Liocoris tripustulatus</i> offered a choice of sweet pepper (salad host) and nettle (wild host) leaves with the same % nitrogen content in a darkened choice chamber – summary of results.

1<p>n = 30 for each sex. Mann-Whitney test used to compare median time on leaf; Chi square test used to compare number of first contacts; ns = not significant.</p><p>When there was no difference in nitrogen content of the nettle and sweet pepper leaves both sexes spent significantly more time in contact with nettle leaves. There was no difference in the first leaf chosen in any of the trials with <i>L. tripustulatus</i>.</p

<i>Liocoris tripustulatus</i> offered a choice of sweet pepper (salad host) and nettle (wild host) leaves when the salad host had higher % nitrogen content in a darkened choice chamber – summary of results.

1<p>n = 30 for each sex. Mann-Whitney test used to compare median time on leaf; Chi square test used to compare number of first contacts; ns = not significant.</p><p>When offered a choice of nettle and sweet pepper when the pepper leaves had higher nitrogen content than nettle leaves, there were no preferences exhibited (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0046448#pone-0046448-t003" target="_blank">Table 3</a>).</p

<i>Lygus rugulipennis</i> offered a choice of cucumber (salad host) and nettle (wild host) leaves in a darkened choice chamber – summary of results.

1<p>n = 30 for each sex. Mann-Whitney test used to compare median time on leaf; Chi square test used to compare number of first contacts; ns = not significant.</p><p>Females showed a significant preference for cucumber (salad host) over nettle (wild host). They chose cucumber leaves first in significantly more trials than nettle leaves. Males did not exhibit any preference between cucumber and nettle leaves.</p

<i>Lygus rugulipennis</i> offered a choice of sweet pepper (salad host) and nettle (wild host) leaves in a darkened choice chamber – summary of results.

1<p>n = 30 for each sex. Mann-Whitney test used to compare median time on leaf; Chi square test used to compare number of first contacts; ns = not significant.</p><p>In the choice tests with nettle and sweet pepper males of <i>L. rugulipennis</i> made first contact with sweet pepper on significantly more occasions than nettle This was the only preference exhibited by male or female <i>L. rugulipennis</i> in this set of experiments.</p

Total percentage nitrogen in experimental leaves offered to <i>Lygus rugulipennis.</i>

<p><i>Post hoc</i> comparisons (Fisher's pairwise comparisons) showed that the level of nitrogen in the salad leaves differed significantly to the nettle leaves but not to each other.</p

State of nature

For the first time ever, the UK’s wildlife organisations have joined forces to undertake a health check of nature in the UK and its Overseas Territories. 60% of the 3,148 UK species we assessed have declined over the last 50 years and 31% have declined strongly. Half of the species assessed have shown strong changes in their numbers or range, indicating that recent environmental changes are having a dramatic impact on nature in the UK. Species with specific habitat requirements seem to be faring worse than generalist species. A new Watchlist Indicator, developed to measure how conservation priority species are faring, shows that their overall numbers have declined by 77% in the last 40 years, with little sign of recovery. Of more than 6,000 species that have been assessed using modern Red List criteria, more than one in 10 are thought to be under threat of extinction in the UK. Our assessment looks back over 50 years at most, yet there were large declines in the UK’s wildlife prior to this, linked to habitat loss. The UK’s Overseas Territories hold a wealth of wildlife of huge international importance and over 90 of these species are at high risk of global extinction. There is a lack of knowledge on the trends of most of the UK’s species. As a result, we can report quantitative trends for only 5% of the 59,000 or so terrestrial and freshwater species in the UK, and for very few of the 8,500 marine species. Much needs to be done to improve our knowledge. What we do know about the state of the UK’s nature is often based upon the efforts of thousands of dedicated volunteer enthusiasts who contribute their time and expertise to monitoring schemes and species recording. The threats to the UK’s wildlife are many and varied, the most severe acting either to destroy valuable habitat or degrade the quality and value of what remains. Climate change is having an increasing impact on nature in the UK. Rising average temperatures are known to be driving range expansion in some species, but evidence for harmful impacts is also mounting. The full report is online: www.rspb.org.uk/stateofnature We should act to save nature both for its intrinsic value and for the benefits it brings to us that are essential to our wellbeing and prosperity. Targeted conservation has produced inspiring success stories and, with sufficient determination, resources and public support, we can turn the fortunes of our wildlife around. The State of Nature report serves to illustrate that with shared resolve and commitment we can save nature

A prioritised list of invasive alien species to assist the effective implementation of EU legislation

1. Effective prevention and control of invasive species generally relies on a compre-hensive, coherent and representative list of species that enables resources to be used optimally. European Union (EU) Regulation 1143/2014 on invasive alien spe-cies (IAS) aims to control or eradicate priority species, and to manage pathways to prevent the introduction and establishment of new IAS; it applies to species consid-ered of Union concern and subject to formal risk assessment. So far, 49 species have been listed but the criteria for selecting species for risk assessment have not been disclosed and were probably unsystematic. 2. We developed a simple method to systematically rank IAS according to their maxi-mum potential threat to biodiversity in the EU. We identified 1,323 species as po-tential candidates for listing, and evaluated them against their invasion stages and reported impacts, using information from databases and scientific literature. 3. 900 species fitted the criteria for listing according to IAS Regulation. We prioritised 207 species for urgent risk assessment, 59 by 2018 and 148 by 2020, based on their potential to permanently damage native species or ecosystems; another 336 species were identified for a second phase (by 2025), to prevent or reverse their profound impacts on biodiversity; and a further 357 species for assessment by 2030. 4. Policy implications. We propose a systematic, proactive approach to selecting and prioritising IAS for risk assessment to assist European Union policy implementation. We assess an unprecedented number of species with potential to harm EU biodiversity using a simple methodology and recommend which species should be considered for risk assessment in a ranked order of priority along the timeline 2018–2030, based on their maximum reported impact and their invasion history in Europe