A Chinese mitten crab has been recorded in Scotland for the first time, posing a potential threat to local biodiversity and habitats.

The invasive crab species is already known to have populated rivers in the UK as far north as the Tyne, but this sighting in Glasgow's River Clyde confirms its migration over the Scottish border.

The Chinese mitten crab, named for the furry mats covering its claws, is one of the top 100 worst alien species in the world, according to the International Union for Conservation of Nature. It threatens biodiversity by competing for food, preying on native species and causing severe structural damage to riverbanks through burrowing.

Crabs on tour

The specimen found in the River Clyde, the remains of a female mitten crab, is the first recorded sighting north of the border.

The Chinese mitten crab (Eriocheir sinensis), is native to East Asia but is now found across NE Europe and the USA. It was first recorded in the River Thames in 1935, probably introduced by shipping. In the late 1980s the mitten crab began to disperse westwards along the Thames, and there are now well-established populations of E. sinensis in a number of Welsh and English rivers, as well as a single sighting in Ireland in 2006.

The left claw of a male mitten crab (Eriocheir sinensis).

The International Maritime Organisation (IMO) has set out standards for the control and management of ships’ ballast water and sediments, in an effort to control the transport of species to non-native waters.

Potential threat to biodiversity

Mitten crabs may target the eggs of salmon and trout, according to recent research by Royal Holloway University of London (RHUL) student Jessica Webster and supervisors Dr Paul Clark (the Museum) and Dr David Morritt (RHUL).

Dr Clark sees the recent discovery as a major threat:

"An established River Clyde Chinese mitten crab population could pose an enormous environmental risk to the salmon and trout in this catchment (…) if this reported Clyde specimen came from a deliberate human release, the environmental authorities need to urgently consider what appropriate actions are required to prevent such introductions happening again in the future."

Dr Clark is studying the biology and behaviour of mitten crabs to better understand how we might control their migration and ultimately eradicate alien populations outside East Asia.

See live mitten crabs at Science Uncovered

As part of the Museum's annual festival of science on 26 September 2014, Dr Paul Clark and Dr David Morritt will be showcasing some live Chinese mitten crabs and talking about their work on the biology and behaviour of this problem species.

Come along to Science Uncovered to see these and a whole host of other specimens, take part in activities and meet Museum scientists.

A species of nightshade thought to be restricted to one area of Peru has been found in 17 other locations with the aid of habitat modelling.

Museum botanists Dr Tiina Särkinen (now at the Royal Botanic Garden Edinburgh) and Dr Sandra Knapp discovered the new species of nightshade, named this week as Solanum pseudoamericanum, in 2012 in the Andes. When they first found it, they thought this species only occurred in two river valleys in southern Peru. By using a method known as species distribution modelling, they predicted other regions of Peru where the plant might also be found, based on the environmental conditions at the original collection sites.

An example of the newly discovered Solanum pseudoamericanum, collected on 7 March 2012.

The flowers are on the left and the berries on the right.

A collecting field trip to northern Peru the following year uncovered the nightshade in 17 new locations predicted by the model. The success of the project proves the method of species distribution modelling can work in complex climatic regions such as the Andes, where there is an abundance of undiscovered species and data coverage is generally poor.

Mapping species

Species distribution modelling uses climatic data to help map the range of a new species, speeding up the process of cataloguing it worldwide and providing a way to accurately predict where that species might be found again.

The approach may be particularly useful when dealing with critically endangered species, where there is an urgent need to find and conserve remaining populations.

The work is part of a larger project to map the distribution patterns of all the endemic Solanaceae species in Peru, and to look for components of rarity; what sorts of things make plant species rare. With this information, researchers hope to be able to better describe, and then conserve, plant diversity in Peru.

Hidden diversity

Species distribution modelling has been used successfully for vertebrates before, but has not been widely tested in plants. Dr Knapp belives this may be because collecting plants is seen as reasonably straightforward, but this case study suggests that it is not always true.

Solanum pseudoamericanum was not originally collected because it looks a lot like a common weed. 'Collecting is extremely biased, and this raises the question of how we deal with absences,' Knapp said. The new species represents a category of 'hidden diversity', where new discoveries can be obscured by their physical similarity to known, common species.

Open data

The research, and all its associated geographical and specimen data, is published this week in the open-access journal PhytoKeys. By publishing the results and original specimens as open data, said Knapp, large specimen datasets can be combined by other researchers globally to produce more general analyses of diversity.

• To follow the adventures of the Solanaceae seekers, read the Museum blog Seeking nightshades in South America.
• For mroe infomration about nightshades and their global distribtuion, visit the Solanaceae Source scratchpad.