Limits...
Recurrent camouflaged invasions and dispersal of an Asian freshwater gastropod in tropical Africa.

Van Bocxlaer B, Clewing C, Mongindo Etimosundja JP, Kankonda A, Wembo Ndeo O, Albrecht C - BMC Evol. Biol. (2015)

Bottom Line: Assessing ecological and evolutionary consequences of invasions simultaneously may therefore be the most effective approach to study taxa with complex invasion histories.Finally, the results of geographic modeling indicate that cryptic M. tuberculata invasions occurred primarily in densely populated areas.We draw suggestions for more effective conservation strategies from our integrated approach.

View Article: PubMed Central - PubMed

Affiliation: Department of Animal Ecology and Systematics, Justus Liebig University Giessen, Heinrich-Buff-Ring 26-32 (IFZ), D-35392, Giessen, Germany. bert.vanbocxlaer@ugent.be.

ABSTRACT

Background: Non-indigenous taxa currently represent a large fraction of the species and biomass of freshwater ecosystems. The accumulation of invasive taxa in combination with other stressors in these ecosystems may alter the habitats to which native taxa are adapted, which could elicit evolutionary changes in native populations and their ecological interactions. Assessing ecological and evolutionary consequences of invasions simultaneously may therefore be the most effective approach to study taxa with complex invasion histories. Here we apply such an integrated approach to the cerithioid gastropod Melanoides tuberculata, a model system in invasion biology.

Results: Molecular phylogenetics and ancestral range reconstructions allowed us to identify several independent Asian invasions in Lakes Malawi and Tanganyika, the Congo River, Nigeria and Cameroon. Some invasive M. tuberculata populations display much variation in shell morphology, and overlap in morphospace with M. tuberculata populations native to Africa. Experiments confirmed great ecophenotyic plasticity in some invasive populations, which, in combination with the overlap in disparity with native populations, masks invaders and their dispersal through Africa. Finally, the results of geographic modeling indicate that cryptic M. tuberculata invasions occurred primarily in densely populated areas.

Conclusions: We reveal the continental nature of invasions of Asian M. tuberculata to Africa. Several of the affected ecosystems have high endemicity in Cerithioidea: Lake Tanganyika has an unparalleled diversity in freshwater cerithioids (>10 endemic genera) and the Congo Basin and Lake Malawi are home to the two largest endemic species clusters of Melanoides in Africa (~12 and ~8 species, respectively). Cerithioids perform ecologically important functions in the benthic ecosystems of African freshwaters, but invaders and ecosystem change pose risks to their native diversity. We draw suggestions for more effective conservation strategies from our integrated approach.

Show MeSH
Map of Africa with localities ofMelanoidespopulations included in our study. The genus occurs in a wide variety of water bodies throughout Africa (rivers, ponds, lakes), but is absent from substantial areas, e.g. in the Sahara it has scattered occurrences in oasis lakes. Solid symbols indicate invasive M. tuberculata populations, open ones native Melanoides populations. Two red symbols indicate approximate localities of GenBank material. A solid black line delimits sub-Saharan Africa as defined for modeling purposes following [28]. Map modified from Amante and Eakins [29].
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC4373078&req=5

Fig1: Map of Africa with localities ofMelanoidespopulations included in our study. The genus occurs in a wide variety of water bodies throughout Africa (rivers, ponds, lakes), but is absent from substantial areas, e.g. in the Sahara it has scattered occurrences in oasis lakes. Solid symbols indicate invasive M. tuberculata populations, open ones native Melanoides populations. Two red symbols indicate approximate localities of GenBank material. A solid black line delimits sub-Saharan Africa as defined for modeling purposes following [28]. Map modified from Amante and Eakins [29].

Mentions: We collected material from the Congo River, its tributaries and the Lake Edward region of the Democratic Republic of Congo (DRC), from Lake Tanganyika in Burundi, Lake Malawi and the Shire River in Malawi, Lake Kivu in Rwanda, and Lakes Kyoga and Edward, and the Victorian Nile River in Uganda (all between 2006 and 2012), and supplemented this material with previously published samples (Table 1; Figure 1). Material collected for phylogenetic studies was preserved in 80% EtOH. Specimens of one Melanoides population (n = 40; 09-032; CD05-CD06) from Kisangani (DRC) were maintained and bred in laboratory tanks after which the shell morphology of wild-caught parents, lab-bred F1 offspring, and other populations of M. tuberculata were compared. For the experiment we used a 100 l tank that had been set up before for common garden experiments with endemic gastropods from Lake Malawi (seeded with Malawi sand and water; see [27]). Water conditions reflected those of Lake Malawi (pH ~8.0; T = ~26°C), but with a higher amount of dissolved oxygen (~6.0 mL/L instead of 3.5-4.0 mL/L), and a higher electrical conductivity (increased bicarbonate hardness; ~1,800 μS/cm instead of ~260 μS/cm in the lake) to prevent shell corrosion. These values are somewhat dissimilar from those measured in waters in the Kisangani area (09-032; pH ~6.0-7.0; T = ~24°C, conductivity ~70 μS/cm).Table 1


Recurrent camouflaged invasions and dispersal of an Asian freshwater gastropod in tropical Africa.

Van Bocxlaer B, Clewing C, Mongindo Etimosundja JP, Kankonda A, Wembo Ndeo O, Albrecht C - BMC Evol. Biol. (2015)

Map of Africa with localities ofMelanoidespopulations included in our study. The genus occurs in a wide variety of water bodies throughout Africa (rivers, ponds, lakes), but is absent from substantial areas, e.g. in the Sahara it has scattered occurrences in oasis lakes. Solid symbols indicate invasive M. tuberculata populations, open ones native Melanoides populations. Two red symbols indicate approximate localities of GenBank material. A solid black line delimits sub-Saharan Africa as defined for modeling purposes following [28]. Map modified from Amante and Eakins [29].
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4373078&req=5

Fig1: Map of Africa with localities ofMelanoidespopulations included in our study. The genus occurs in a wide variety of water bodies throughout Africa (rivers, ponds, lakes), but is absent from substantial areas, e.g. in the Sahara it has scattered occurrences in oasis lakes. Solid symbols indicate invasive M. tuberculata populations, open ones native Melanoides populations. Two red symbols indicate approximate localities of GenBank material. A solid black line delimits sub-Saharan Africa as defined for modeling purposes following [28]. Map modified from Amante and Eakins [29].
Mentions: We collected material from the Congo River, its tributaries and the Lake Edward region of the Democratic Republic of Congo (DRC), from Lake Tanganyika in Burundi, Lake Malawi and the Shire River in Malawi, Lake Kivu in Rwanda, and Lakes Kyoga and Edward, and the Victorian Nile River in Uganda (all between 2006 and 2012), and supplemented this material with previously published samples (Table 1; Figure 1). Material collected for phylogenetic studies was preserved in 80% EtOH. Specimens of one Melanoides population (n = 40; 09-032; CD05-CD06) from Kisangani (DRC) were maintained and bred in laboratory tanks after which the shell morphology of wild-caught parents, lab-bred F1 offspring, and other populations of M. tuberculata were compared. For the experiment we used a 100 l tank that had been set up before for common garden experiments with endemic gastropods from Lake Malawi (seeded with Malawi sand and water; see [27]). Water conditions reflected those of Lake Malawi (pH ~8.0; T = ~26°C), but with a higher amount of dissolved oxygen (~6.0 mL/L instead of 3.5-4.0 mL/L), and a higher electrical conductivity (increased bicarbonate hardness; ~1,800 μS/cm instead of ~260 μS/cm in the lake) to prevent shell corrosion. These values are somewhat dissimilar from those measured in waters in the Kisangani area (09-032; pH ~6.0-7.0; T = ~24°C, conductivity ~70 μS/cm).Table 1

Bottom Line: Assessing ecological and evolutionary consequences of invasions simultaneously may therefore be the most effective approach to study taxa with complex invasion histories.Finally, the results of geographic modeling indicate that cryptic M. tuberculata invasions occurred primarily in densely populated areas.We draw suggestions for more effective conservation strategies from our integrated approach.

View Article: PubMed Central - PubMed

Affiliation: Department of Animal Ecology and Systematics, Justus Liebig University Giessen, Heinrich-Buff-Ring 26-32 (IFZ), D-35392, Giessen, Germany. bert.vanbocxlaer@ugent.be.

ABSTRACT

Background: Non-indigenous taxa currently represent a large fraction of the species and biomass of freshwater ecosystems. The accumulation of invasive taxa in combination with other stressors in these ecosystems may alter the habitats to which native taxa are adapted, which could elicit evolutionary changes in native populations and their ecological interactions. Assessing ecological and evolutionary consequences of invasions simultaneously may therefore be the most effective approach to study taxa with complex invasion histories. Here we apply such an integrated approach to the cerithioid gastropod Melanoides tuberculata, a model system in invasion biology.

Results: Molecular phylogenetics and ancestral range reconstructions allowed us to identify several independent Asian invasions in Lakes Malawi and Tanganyika, the Congo River, Nigeria and Cameroon. Some invasive M. tuberculata populations display much variation in shell morphology, and overlap in morphospace with M. tuberculata populations native to Africa. Experiments confirmed great ecophenotyic plasticity in some invasive populations, which, in combination with the overlap in disparity with native populations, masks invaders and their dispersal through Africa. Finally, the results of geographic modeling indicate that cryptic M. tuberculata invasions occurred primarily in densely populated areas.

Conclusions: We reveal the continental nature of invasions of Asian M. tuberculata to Africa. Several of the affected ecosystems have high endemicity in Cerithioidea: Lake Tanganyika has an unparalleled diversity in freshwater cerithioids (>10 endemic genera) and the Congo Basin and Lake Malawi are home to the two largest endemic species clusters of Melanoides in Africa (~12 and ~8 species, respectively). Cerithioids perform ecologically important functions in the benthic ecosystems of African freshwaters, but invaders and ecosystem change pose risks to their native diversity. We draw suggestions for more effective conservation strategies from our integrated approach.

Show MeSH