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Cryptic speciation or global spread? The case of a cosmopolitan marine invertebrate with limited dispersal capabilities.

R PP, V A, M R, X T - Sci Rep (2013)

Bottom Line: The existence of globally-distributed species with low dispersal capabilities is a paradox that has been explained as a result of human-mediated transport and by hidden diversity in the form of unrecognized cryptic species.In addition, we found a complex geographic structure and multiple clades occurred in sympatry.The present study shows the complexity of discerning the role of cryptic diversity from human-driven range shifts worldwide, as well as disentangling the effects of natural and artificial dispersal.

View Article: PubMed Central - PubMed

Affiliation: Center for Advanced Studies of Blanes (CEAB-CSIC), Accés Cala S Francesc 14, 17300 Blanes (Girona), Spain.

ABSTRACT
The existence of globally-distributed species with low dispersal capabilities is a paradox that has been explained as a result of human-mediated transport and by hidden diversity in the form of unrecognized cryptic species. Both factors are not mutually exclusive, but relatively few studies have demonstrated the presence of both. Here we analyse the genetic patterns of the colonial ascidian Diplosoma listerianum, a species nowadays distributed globally. The study of a fragment of a mitochondrial gene in localities worldwide revealed the existence of multiple cryptic species. In addition, we found a complex geographic structure and multiple clades occurred in sympatry. One of the species showed strong population structure irrespective of geographical distances, which is coherent with stochastic dispersal linked to human transport. The present study shows the complexity of discerning the role of cryptic diversity from human-driven range shifts worldwide, as well as disentangling the effects of natural and artificial dispersal.

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Haplotype network for Diplosoma listerianum from COI data.Areas of the circles are proportional to the number of sampled individuals. Partitions inside the circles represent the proportion of each population within each haplotype. Small white crossed dots without name represent missing, probably unsampled haplotypes or extinct sequences. Lines between circles represent one mutational step, and roman numerals are the number of mutations between haplotypes when more than one.
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f3: Haplotype network for Diplosoma listerianum from COI data.Areas of the circles are proportional to the number of sampled individuals. Partitions inside the circles represent the proportion of each population within each haplotype. Small white crossed dots without name represent missing, probably unsampled haplotypes or extinct sequences. Lines between circles represent one mutational step, and roman numerals are the number of mutations between haplotypes when more than one.

Mentions: An unrooted network constructed using the complete dataset of sequences also supported the existence of four markedly divergent clades lacking intermediate haplotypes (Fig. 3). Clade A, which appeared in all localities analysed, was the most diverse and widely distributed, including 34 haplotypes and a number of “missing” haplotypes that had to be inferred to fully connect the network. In addition, clade A was the most frequent in most localities, with the exception of Bastimentos Island (Panama), Hout Bay and Port Alfred (both from South Africa), and Kanagawa, the only locality from Japan. Within this clade, two distant haplotypes, haplotypes H_2 and H_4, were the most frequent and were present in most localities. Clade C grouped four haplotypes from only three sites of Panama and South Africa (Bastimentos Island, Hout Bay and Port Alfred) (see Table 1 and Fig. 3), and was the most frequent clade encountered in the South African localities with a 54% of the specimens belonging to this clade. This is despite the fact that H_10 found in Hout Bay was separated by more than 30 mutation steps from other haplotypes of the same clade. Clades B and D were the most geographically restricted clades. Clade B, which grouped three genetically distant haplotypes (H_30, H_31 and H_32), appeared only in Japan but it was the most important genetic clade in that particular locality (83.3% of individuals, see Table 1 and Fig. 1). Clade D, which grouped two closely related haplotypes, only appeared in Bastimentos (Panama) but it was the most frequent clade at this particular locality (54.5 % of individuals, see Table 1 and Fig. 1). Overall, the network did not reveal clear geographic structuring. Only a small group of haplotypes (H_18, H_19, H_20, H_21, H_22, H_23, H_24 and H_25), mostly from Panama, formed a cluster (subclade A.1) within clade A, separated by more than 40 mutation steps from the nearest haplotype. This same cluster was also observed in the phylogenetic trees (Fig. 2).


Cryptic speciation or global spread? The case of a cosmopolitan marine invertebrate with limited dispersal capabilities.

R PP, V A, M R, X T - Sci Rep (2013)

Haplotype network for Diplosoma listerianum from COI data.Areas of the circles are proportional to the number of sampled individuals. Partitions inside the circles represent the proportion of each population within each haplotype. Small white crossed dots without name represent missing, probably unsampled haplotypes or extinct sequences. Lines between circles represent one mutational step, and roman numerals are the number of mutations between haplotypes when more than one.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3824166&req=5

f3: Haplotype network for Diplosoma listerianum from COI data.Areas of the circles are proportional to the number of sampled individuals. Partitions inside the circles represent the proportion of each population within each haplotype. Small white crossed dots without name represent missing, probably unsampled haplotypes or extinct sequences. Lines between circles represent one mutational step, and roman numerals are the number of mutations between haplotypes when more than one.
Mentions: An unrooted network constructed using the complete dataset of sequences also supported the existence of four markedly divergent clades lacking intermediate haplotypes (Fig. 3). Clade A, which appeared in all localities analysed, was the most diverse and widely distributed, including 34 haplotypes and a number of “missing” haplotypes that had to be inferred to fully connect the network. In addition, clade A was the most frequent in most localities, with the exception of Bastimentos Island (Panama), Hout Bay and Port Alfred (both from South Africa), and Kanagawa, the only locality from Japan. Within this clade, two distant haplotypes, haplotypes H_2 and H_4, were the most frequent and were present in most localities. Clade C grouped four haplotypes from only three sites of Panama and South Africa (Bastimentos Island, Hout Bay and Port Alfred) (see Table 1 and Fig. 3), and was the most frequent clade encountered in the South African localities with a 54% of the specimens belonging to this clade. This is despite the fact that H_10 found in Hout Bay was separated by more than 30 mutation steps from other haplotypes of the same clade. Clades B and D were the most geographically restricted clades. Clade B, which grouped three genetically distant haplotypes (H_30, H_31 and H_32), appeared only in Japan but it was the most important genetic clade in that particular locality (83.3% of individuals, see Table 1 and Fig. 1). Clade D, which grouped two closely related haplotypes, only appeared in Bastimentos (Panama) but it was the most frequent clade at this particular locality (54.5 % of individuals, see Table 1 and Fig. 1). Overall, the network did not reveal clear geographic structuring. Only a small group of haplotypes (H_18, H_19, H_20, H_21, H_22, H_23, H_24 and H_25), mostly from Panama, formed a cluster (subclade A.1) within clade A, separated by more than 40 mutation steps from the nearest haplotype. This same cluster was also observed in the phylogenetic trees (Fig. 2).

Bottom Line: The existence of globally-distributed species with low dispersal capabilities is a paradox that has been explained as a result of human-mediated transport and by hidden diversity in the form of unrecognized cryptic species.In addition, we found a complex geographic structure and multiple clades occurred in sympatry.The present study shows the complexity of discerning the role of cryptic diversity from human-driven range shifts worldwide, as well as disentangling the effects of natural and artificial dispersal.

View Article: PubMed Central - PubMed

Affiliation: Center for Advanced Studies of Blanes (CEAB-CSIC), Accés Cala S Francesc 14, 17300 Blanes (Girona), Spain.

ABSTRACT
The existence of globally-distributed species with low dispersal capabilities is a paradox that has been explained as a result of human-mediated transport and by hidden diversity in the form of unrecognized cryptic species. Both factors are not mutually exclusive, but relatively few studies have demonstrated the presence of both. Here we analyse the genetic patterns of the colonial ascidian Diplosoma listerianum, a species nowadays distributed globally. The study of a fragment of a mitochondrial gene in localities worldwide revealed the existence of multiple cryptic species. In addition, we found a complex geographic structure and multiple clades occurred in sympatry. One of the species showed strong population structure irrespective of geographical distances, which is coherent with stochastic dispersal linked to human transport. The present study shows the complexity of discerning the role of cryptic diversity from human-driven range shifts worldwide, as well as disentangling the effects of natural and artificial dispersal.

Show MeSH