Limits...
Conservation genetics of a critically endangered limpet genus and rediscovery of an extinct species.

Ó Foighil D, Li J, Lee T, Johnson P, Evans R, Burch JB - PLoS ONE (2011)

Bottom Line: It persists in a Coosa River tributary and morphometric and phylogenetic analyses confirm its taxonomic validity.All three surviving populations of the genus Rhodacmea merit specific status.We recommend the establishment of a proactive targeted conservation program that may include their captive propagation and reintroduction.

View Article: PubMed Central - PubMed

Affiliation: Museum of Zoology and Department of Ecology and Evolutionary Biology, The University of Michigan, Ann Arbor, Michigan, United States of America. diarmaid@umich.edu

ABSTRACT

Background: A third of all known freshwater mollusk extinctions worldwide have occurred within a single medium-sized American drainage. The Mobile River Basin (MRB) of Alabama, a global hotspot of temperate freshwater biodiversity, was intensively industrialized during the 20(th) century, driving 47 of its 139 endemic mollusk species to extinction. These include the ancylinid limpet Rhodacmea filosa, currently classified as extinct (IUCN Red List), a member of a critically endangered southeastern North American genus reduced to a single known extant population (of R. elatior) in the MRB.

Methodology/principal findings: We document here the tripling of known extant populations of this North American limpet genus with the rediscovery of enduring Rhodacmea filosa in a MRB tributary and of R. elatior in its type locality: the Green River, Kentucky, an Ohio River Basin (ORB) tributary. Rhodacmea species are diagnosed using untested conchological traits and we reassessed their systematic and conservation status across both basins using morphometric and genetic characters. Our data corroborated the taxonomic validity of Rhodacmea filosa and we inferred a within-MRB cladogenic origin from a common ancestor bearing the R. elatior shell phenotype. The geographically-isolated MRB and ORB R. elatior populations formed a cryptic species complex: although overlapping morphometrically, they exhibited a pronounced phylogenetic disjunction that greatly exceeded that of within-MRB R. elatior and R. filosa sister species.

Conclusions/significance: Rhodacmea filosa, the type species of the genus, is not extinct. It persists in a Coosa River tributary and morphometric and phylogenetic analyses confirm its taxonomic validity. All three surviving populations of the genus Rhodacmea merit specific status. They collectively contain all known survivors of a phylogenetically highly distinctive North American endemic genus and therefore represent a concentrated fraction of continental freshwater gastropod biodiversity. We recommend the establishment of a proactive targeted conservation program that may include their captive propagation and reintroduction.

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Map of southeastern U.S.A. watersheds.The Ohio and Mobile River Basins are highlighted to show the locations of all known extant Rhodacmea elatior and R. filosa populations.
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pone-0020496-g001: Map of southeastern U.S.A. watersheds.The Ohio and Mobile River Basins are highlighted to show the locations of all known extant Rhodacmea elatior and R. filosa populations.

Mentions: North American drainages experienced a major wave of impoundment during the early-mid 20th century and <2% (<100,000 km) of high-quality, free-flowing rivers remain of an estimated original U.S. figure of 5,200,000 km [6]. Damming completely transforms dynamic lotic habitats, turning free-flowing rivers into chains of reservoirs with severe consequences for endemic biotas [7]. This is most starkly evident in the southeastern United States Mobile River Basin (MRB; Fig. 1), a global hotspot of temperate freshwater fish and mollusk diversity characterized by extraordinary levels of endemism, including 40 fish species [8] and 34 mussel and 105 snail species [9], [10] found nowhere else. The MRB was transformed by the construction of 36 major dams and locks that replaced endemic species-rich riverine shoal, riffle and pool habitats with lentic reservoirs along much of the mainstem MRB rivers and their tributary streams [11]. Its endemic malacofauna was especially hard hit and an estimated 10 mussel species and 37 snail species were driven to extinction ([11]–[13], PJ, unpubl.). This represents a third of all known freshwater molluscan extinctions worldwide [14] and has been referred to as “one of the greatest known extinction episodes of the first half of the twentieth century” [15].


Conservation genetics of a critically endangered limpet genus and rediscovery of an extinct species.

Ó Foighil D, Li J, Lee T, Johnson P, Evans R, Burch JB - PLoS ONE (2011)

Map of southeastern U.S.A. watersheds.The Ohio and Mobile River Basins are highlighted to show the locations of all known extant Rhodacmea elatior and R. filosa populations.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3105076&req=5

pone-0020496-g001: Map of southeastern U.S.A. watersheds.The Ohio and Mobile River Basins are highlighted to show the locations of all known extant Rhodacmea elatior and R. filosa populations.
Mentions: North American drainages experienced a major wave of impoundment during the early-mid 20th century and <2% (<100,000 km) of high-quality, free-flowing rivers remain of an estimated original U.S. figure of 5,200,000 km [6]. Damming completely transforms dynamic lotic habitats, turning free-flowing rivers into chains of reservoirs with severe consequences for endemic biotas [7]. This is most starkly evident in the southeastern United States Mobile River Basin (MRB; Fig. 1), a global hotspot of temperate freshwater fish and mollusk diversity characterized by extraordinary levels of endemism, including 40 fish species [8] and 34 mussel and 105 snail species [9], [10] found nowhere else. The MRB was transformed by the construction of 36 major dams and locks that replaced endemic species-rich riverine shoal, riffle and pool habitats with lentic reservoirs along much of the mainstem MRB rivers and their tributary streams [11]. Its endemic malacofauna was especially hard hit and an estimated 10 mussel species and 37 snail species were driven to extinction ([11]–[13], PJ, unpubl.). This represents a third of all known freshwater molluscan extinctions worldwide [14] and has been referred to as “one of the greatest known extinction episodes of the first half of the twentieth century” [15].

Bottom Line: It persists in a Coosa River tributary and morphometric and phylogenetic analyses confirm its taxonomic validity.All three surviving populations of the genus Rhodacmea merit specific status.We recommend the establishment of a proactive targeted conservation program that may include their captive propagation and reintroduction.

View Article: PubMed Central - PubMed

Affiliation: Museum of Zoology and Department of Ecology and Evolutionary Biology, The University of Michigan, Ann Arbor, Michigan, United States of America. diarmaid@umich.edu

ABSTRACT

Background: A third of all known freshwater mollusk extinctions worldwide have occurred within a single medium-sized American drainage. The Mobile River Basin (MRB) of Alabama, a global hotspot of temperate freshwater biodiversity, was intensively industrialized during the 20(th) century, driving 47 of its 139 endemic mollusk species to extinction. These include the ancylinid limpet Rhodacmea filosa, currently classified as extinct (IUCN Red List), a member of a critically endangered southeastern North American genus reduced to a single known extant population (of R. elatior) in the MRB.

Methodology/principal findings: We document here the tripling of known extant populations of this North American limpet genus with the rediscovery of enduring Rhodacmea filosa in a MRB tributary and of R. elatior in its type locality: the Green River, Kentucky, an Ohio River Basin (ORB) tributary. Rhodacmea species are diagnosed using untested conchological traits and we reassessed their systematic and conservation status across both basins using morphometric and genetic characters. Our data corroborated the taxonomic validity of Rhodacmea filosa and we inferred a within-MRB cladogenic origin from a common ancestor bearing the R. elatior shell phenotype. The geographically-isolated MRB and ORB R. elatior populations formed a cryptic species complex: although overlapping morphometrically, they exhibited a pronounced phylogenetic disjunction that greatly exceeded that of within-MRB R. elatior and R. filosa sister species.

Conclusions/significance: Rhodacmea filosa, the type species of the genus, is not extinct. It persists in a Coosa River tributary and morphometric and phylogenetic analyses confirm its taxonomic validity. All three surviving populations of the genus Rhodacmea merit specific status. They collectively contain all known survivors of a phylogenetically highly distinctive North American endemic genus and therefore represent a concentrated fraction of continental freshwater gastropod biodiversity. We recommend the establishment of a proactive targeted conservation program that may include their captive propagation and reintroduction.

Show MeSH
Related in: MedlinePlus