Tag Archives: invasive species

Achatina fulica east of Andes in Ecuador

Goldyn et al. have just published a paper of which the abstract reads “[w]e are reporting the first locality of invasive giant African snail, Achatina (Lissachatina) fulica (Férussac, 1821) in the Ecuadorian Amazon. It was found present in 32 out of 50 urban sites studied. The abundance where present was relatively high when compared to literature from other parts of the world. The snails were found in aggregations, usually foraging — most often on dogs’ feces. Statistical analysis suggests a preference toward this source of alimentation. This is the first report of such preference in this species, which is highly significant considering the possible implications. Besides the threat posed by an invasive species to the invaluable ecosystems of the Amazon, the pathogens transferred by A. fulica combined with a high abundance of the species in an urban environment and its food preferences may constitute an important health hazard for local human populations”.

This is, however, not the first published occurrence east of the Andes in Ecuador. The same authors have published this, and additional data, before in Folia Malacologica last year. If not an oversight by the reviewers and editor, this so-called “first locality” has to be blamed to the authors.

But the fact as such (if we exclude the many Brazilian occurrences), unfortunately, was waiting just to happen. Hopefully the Ecuadorian authorities nowadays know how they should eradicate this pest before it becomes wide-spread in this area which contain many endemic species.

Reference:
Goldyn, B., et al., 2017. Urban ecology of invasive giant African snail Achatina fulica (Férussac) (Gastropoda: Achatinidae) on its first recorded sites in the Ecuadorian Amazon. – American Malacological Bulletin, 35: 59-64.

Genetics of invasive Cornu

Another paper on invasive species, i.e. Cornu aspersum in Chile, is entirely devoted to genetics. It was recently published by Nespolo et al. (2014).

Nespolo2014_Fig2

The summary of this paper comprises seven items:
1. The distribution of additive vs. non-additive genetic variation in natural populations represents a central topic of research in evolutionary/organismal biology. For evolutionary physiologists, functional or whole-animal performance traits (‘physiological traits’) are frequently studied assuming they are heritable and variable in populations.
2. Physiological traits of evolutionary relevance are those functional capacities measured at the whole-organism level, with a potential impact on fitness. They can be classified as capacities (or performances) or costs, the former being directly correlated with fitness and the latter being inversely correlated with fitness (usually assumed as constraints).
3. In spite of their obvious adaptive significance, the additive genetic variation in physiological traits, and its relative contribution to phenotypic variance (or narrow-sense heritability) in comparison with maternal, dominance or epistatic variance, is known only for a few groups such as insects and mammals.
4. In this study, we assessed the additive and maternal/non-additive genetic variation in a suite of physiological and morphological traits in populations of the land snail Cornu aspersum.
5. Except for dehydration rate (h2 = 0.32 +/- 0.15), egg mass (h2 = 0.82 +/- 0.30) and hatchling mass (h2 = 1.01 +/- 0.31; population = fixed effect), we found very low additive genetic variation. Large non-additive/maternal effects were found in all traits. Cage effects did not change the results, indicating low contribution of common environmental variance to our results. No differences were found between the phenotypic and non-additive genetic variance/covariance matrices.
6. Even though we compared populations across 1300 km in a common garden set-up, our results suggest an absence of physiological as well as morphological differentiation in these populations.
7. These results contrast with previous analyses in the original distributional range of this species, which found high additive genetic variation in morphological traits. These are intriguing results demanding further quantitative genetic studies in the original distributional range of this species as well as the history of colonization of this invasive species.

Especially items 6 and 7 are interesting. Suppose we may see some time a follow-up by these authors.

Reference:

Nespolo, R.F., Bartheld, J.F., González, A., Bruning, A., Roff, D.A., Bacigalupe, L.D. & Gaitan-Espitia, J.D., 2014. The quantitative genetics of physiological and morphological traits in an invasive terrestrial snail: additive vs. non-additive genetic variation. – Functional Ecology 28 (3): 682-692.

Invasive Deroceras slugs

Just published: a paper by Hutchinson et al. (2014) on invasive Deroceras slugs. The abstract reads:

The article reviews distribution records of Deroceras invadens (previously called D. panormitanum and D. caruanae), adding significant unpublished records from the authors’ own collecting, museum samples, and interceptions on goods arriving in the U.S.A. By 1940 D. invadens had already arrived in Britain, Denmark, California, Australia and probably New Zealand; it has turned up in many further places since, including remote oceanic islands, but scarcely around the eastern Mediterranean (Egypt and Crete are the exceptions), nor in Asia. Throughout much of the Americas its presence seems to have been previously overlooked, probably often being mistaken for D. laeve. New national records include Mexico, Costa Rica, and Ecuador, with evidence from interceptions of its presence in Panama, Peru, and Kenya. The range appears limited by cold winters and dry summers; this would explain why its intrusion into eastern Europe and southern Spain has been rather slow and incomplete. At a finer geographic scale, the occurrence of the congener D. reticulatum provides a convenient comparison to control for sampling effort; D. invadens is often about half as frequently encountered and sometimes predominates. Deroceras invadens is most commonly found in synanthropic habitats, particularly gardens and under rubbish, but also in greenhouses, and sometimes arable land and pasture. It may spread into natural habitats, as in Britain, South Africa, Australia and Tenerife. Many identifications have been checked in the light of recent taxonomic revision, revealing that the sibling species D. panormitanum s.s. has spread much less extensively. A number of published or online records, especially in Australia, have turned out to be misidentifications of D. laeve.

HutchingtonFig4

Reference:

Hutchinson, J., Reise, H. & Robinson, D., 2014. A biography of an invasive terrestrial slug: the spread, distribution and habitat of Deroceras invadens. NeoBiota 23: 17–64. Available at http://neobiota.pensoft.net/articles.php?id=4006.

An elegant U-loop?

Invasive species are a well-documented when they are discovered in countries with good monitoring systems. However, in some instances these ‘hidden secrets’ of economic liberalisation and globalisation stay under the radar of authorities and scientists.

David Robinson kindly sent an example of this when showing me these pictures.

Bulimulidae-2-lateralBulimulidae-lateral-1Bul-4-apex

This is a Bulimulus species, possibly B. sporadicus (d’Orbigny, 1835); the specimen is not fully grown.

At first I couldn’t believe my eyes when I read where it originated from. Guinea? Perhaps an error for Guiana? No, it’s the West African country!! A Bulimulus species in Africa?!?

These specimens (not the first instance!) were intercepted when they were brought into a U.S.A. port. David said it is likely that they first were exported from the Houston area with oil-drilling equipment. “Most of the oil-drilling equipment goes to West African countries from Houston where the containers get contaminated. The port areas must be crawling with invasive snails there. Then when the containers come back to different ports in the US, they are crawling with Texan snails.”

This implies that in several countries lots of American and European species must be present (we know the reports, don’t we?), but this is the first time I hear that an alien species in one country becomes an exotic in a second one and then gets re-imported in the first country at different places. My ‘U-loop’ hypothesis, perhaps logical that it should happen one day, is here reported for the first bulimulid species criss-crossing the ocean.

Oxychilus in Chile

While the European species Oxychilus alliarius (Miller, 1822) has been mentioned here as an invasive species in Chile, Cádiz et al. has just published a study which confirms this on morphological and molecular grounds.

In the present study we report the first record of the western European terrestrial snail Oxychilus alliarius (Miller, 1822) for continental Chile. Oxychilus alliarius is known for its highly predatory and invasive behavior, being directly associated with the decline of native snail populations in places where it has been introduced. Continental Chile has, on the other hand, the highest generic and specific endemism known for Punctoidea in the American continent, most of them potential prey for O. alliarius. The different species of Oxychilus are easily misidentified because of their conchological similarity. To overcome misidentification, we analyzed both morphological and molecular data which should enable the unambiguous identification of O. alliarius. In order to engage and facilitate further studies we describe and illustrate characters of the radula, shell, and present molecular data of O. alliarius, which are useful and necessary for distinguishing O. alliarius from its sister species.

Reference:
Cádiz, F.J., Cádiz, D.G. & Grau, J.H. (2013). An invasive predatory snail Oxychilus alliarius (Miller, 1822) (Stylommatophora: Zonitidae) threatens the native malacofauna of continental Chile: a morphological and molecular confirmation. — Studies on Neotropical Fauna and Environment 48: 119–124.