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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Morphometric analyses of Rhodacmea populations.3A. Scatter plot showing shell shape principal component analyses of individual limpets from three groups: 1) Green River Rhodacmea elatior (n = 12); 2) Cahaba River R. elatior (n = 7); 3) a combined sample of apically-intact R. filosa from an extant Choccolocco Creek population (n = 2, arrowed) and museum specimens from an extirpated Tallaseehatchee Creek population (n = 8). The mean shapes of each group are shown at the top of the plot. 3B. A composite outline showing PCA deformation vectors on individual landmarks for PC1 representing changes between a consensus shape for all limpets analysed (PC1 = 0) and that of a hypothetical limpet positioned mid-range (PC1 = 0.1) for Rhodacmea filosa.
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pone-0020496-g003: Morphometric analyses of Rhodacmea populations.3A. Scatter plot showing shell shape principal component analyses of individual limpets from three groups: 1) Green River Rhodacmea elatior (n = 12); 2) Cahaba River R. elatior (n = 7); 3) a combined sample of apically-intact R. filosa from an extant Choccolocco Creek population (n = 2, arrowed) and museum specimens from an extirpated Tallaseehatchee Creek population (n = 8). The mean shapes of each group are shown at the top of the plot. 3B. A composite outline showing PCA deformation vectors on individual landmarks for PC1 representing changes between a consensus shape for all limpets analysed (PC1 = 0) and that of a hypothetical limpet positioned mid-range (PC1 = 0.1) for Rhodacmea filosa.

Mentions: In all but two of the Choccolocco Creek Rhodacmea filosa specimens sampled, the shell apex had broken cleanly off leaving an abruptly truncated apical profile (Fig. 2). Availability of only two apically-intact exemplars complicated our morphometric analyses and we compensated for this by including intact museum Tallaseehatchee Creek reference specimens of R. filosa (UMMZ 69215) (Fig. 2). Figure 3 depicts a principal component analysis plot for limpet lateral profiles sampled from all three extant populations (Fig. 1) as well as from the R. filosa museum sample. The first principal component (PC1) explained 80% of variation in shell shape among all of the limpets. Green River and Cahaba River R. elatior populations overlapped for both PC1 and PC2, as did the extant Choccolocco and extirpated Tallaseehatchee R. filosa populations. However, R. elatior specimens were well separated from R. filosa specimens along PC1. As shown by the PCA deformation graph (Fig. 3B), the most pronounced morphometric difference between the two species occurred in the apical region where intact R. filosa specimens possessed a posteriorally-projecting apex (a feature mentioned in the original species description [36], [37]) absent in R. elatior (Figs. 2, 3B).


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)

Morphometric analyses of Rhodacmea populations.3A. Scatter plot showing shell shape principal component analyses of individual limpets from three groups: 1) Green River Rhodacmea elatior (n = 12); 2) Cahaba River R. elatior (n = 7); 3) a combined sample of apically-intact R. filosa from an extant Choccolocco Creek population (n = 2, arrowed) and museum specimens from an extirpated Tallaseehatchee Creek population (n = 8). The mean shapes of each group are shown at the top of the plot. 3B. A composite outline showing PCA deformation vectors on individual landmarks for PC1 representing changes between a consensus shape for all limpets analysed (PC1 = 0) and that of a hypothetical limpet positioned mid-range (PC1 = 0.1) for Rhodacmea filosa.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0020496-g003: Morphometric analyses of Rhodacmea populations.3A. Scatter plot showing shell shape principal component analyses of individual limpets from three groups: 1) Green River Rhodacmea elatior (n = 12); 2) Cahaba River R. elatior (n = 7); 3) a combined sample of apically-intact R. filosa from an extant Choccolocco Creek population (n = 2, arrowed) and museum specimens from an extirpated Tallaseehatchee Creek population (n = 8). The mean shapes of each group are shown at the top of the plot. 3B. A composite outline showing PCA deformation vectors on individual landmarks for PC1 representing changes between a consensus shape for all limpets analysed (PC1 = 0) and that of a hypothetical limpet positioned mid-range (PC1 = 0.1) for Rhodacmea filosa.
Mentions: In all but two of the Choccolocco Creek Rhodacmea filosa specimens sampled, the shell apex had broken cleanly off leaving an abruptly truncated apical profile (Fig. 2). Availability of only two apically-intact exemplars complicated our morphometric analyses and we compensated for this by including intact museum Tallaseehatchee Creek reference specimens of R. filosa (UMMZ 69215) (Fig. 2). Figure 3 depicts a principal component analysis plot for limpet lateral profiles sampled from all three extant populations (Fig. 1) as well as from the R. filosa museum sample. The first principal component (PC1) explained 80% of variation in shell shape among all of the limpets. Green River and Cahaba River R. elatior populations overlapped for both PC1 and PC2, as did the extant Choccolocco and extirpated Tallaseehatchee R. filosa populations. However, R. elatior specimens were well separated from R. filosa specimens along PC1. As shown by the PCA deformation graph (Fig. 3B), the most pronounced morphometric difference between the two species occurred in the apical region where intact R. filosa specimens possessed a posteriorally-projecting apex (a feature mentioned in the original species description [36], [37]) absent in R. elatior (Figs. 2, 3B).

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