Limits...
Ecological partitioning and diversity in tropical planktonic foraminifera.

Seears HA, Darling KF, Wade CM - BMC Evol. Biol. (2012)

Bottom Line: Sampling was conducted in the tropical Arabian Sea, during the southwest (summer) monsoon, when pronounced environmental conditions result in a strong disparity in temperature, salinity and productivity between distinct northern and southern water masses.We propose sea-surface primary productivity as the main factor driving the geographical segregation of Arabian Sea planktonic foraminifera, during the SW monsoon, with variations in symbiotic associations possibly playing a role in the specific ecological adaptations observed.Our findings suggest that ecological partitioning could be contributing to the high levels of 'cryptic' genetic diversity observed within the planktonic foraminifera, and support the view that ecological processes may play a key role in the diversification of marine pelagic organisms.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Biology, University of Nottingham, Nottingham, UK.

ABSTRACT

Background: Ecological processes are increasingly being viewed as an important mode of diversification in the marine environment, where the high dispersal potential of pelagic organisms, and a lack of absolute barriers to gene flow may limit the occurrence of allopatric speciation through vicariance. Here we focus on the potential role of ecological partitioning in the diversification of a widely distributed group of marine protists, the planktonic foraminifera. Sampling was conducted in the tropical Arabian Sea, during the southwest (summer) monsoon, when pronounced environmental conditions result in a strong disparity in temperature, salinity and productivity between distinct northern and southern water masses.

Results: We uncovered extensive genetic diversity within the Arabian Sea planktonic foraminifera, identifying 13 morphospecies, represented by 20 distinct SSU rRNA genetic types. Several morphospecies/genetic types displayed non-random biogeographical distributions, partitioning between the northern and southern water masses, giving a strong indication of independent ecological adaptations.

Conclusions: We propose sea-surface primary productivity as the main factor driving the geographical segregation of Arabian Sea planktonic foraminifera, during the SW monsoon, with variations in symbiotic associations possibly playing a role in the specific ecological adaptations observed. Our findings suggest that ecological partitioning could be contributing to the high levels of 'cryptic' genetic diversity observed within the planktonic foraminifera, and support the view that ecological processes may play a key role in the diversification of marine pelagic organisms.

Show MeSH
Bayesian inference SSU rDNA phylogenetic tree showing the position of the Arabian Sea morphospecies and genotypes within the foraminifera. The phylogeny is based on 407 unambiguously aligned nucleotide sites and is rooted on the benthic foraminifer Allogromia sp. Bayesian posterior probabilities (from the last 1000 trees, obtained within MrBayes) and ML bootstraps (expressed as a percentage, 1000 replicates) are shown on the tree (BI posterior probabilities/ML bootstraps). The scale bar corresponds to a genetic distance of 2%. Benthic foraminiferal taxa are shown in grey text, and planktonic foraminifera are shown in black. Morphospecies and genotypes found in the Arabian Sea are shown on a grey background. A star indicates a novel sequence obtained from the Arabian Sea cruise (CD148). The sequence for S. globigerus is also presented in [72].
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3361484&req=5

Figure 2: Bayesian inference SSU rDNA phylogenetic tree showing the position of the Arabian Sea morphospecies and genotypes within the foraminifera. The phylogeny is based on 407 unambiguously aligned nucleotide sites and is rooted on the benthic foraminifer Allogromia sp. Bayesian posterior probabilities (from the last 1000 trees, obtained within MrBayes) and ML bootstraps (expressed as a percentage, 1000 replicates) are shown on the tree (BI posterior probabilities/ML bootstraps). The scale bar corresponds to a genetic distance of 2%. Benthic foraminiferal taxa are shown in grey text, and planktonic foraminifera are shown in black. Morphospecies and genotypes found in the Arabian Sea are shown on a grey background. A star indicates a novel sequence obtained from the Arabian Sea cruise (CD148). The sequence for S. globigerus is also presented in [72].

Mentions: A comprehensive foraminiferal phylogeny, based on 407 bp of the SSU rRNA gene (Figure 2) highlights the placement of the Arabian Sea taxa. All methods of phylogeny reconstruction utilised were largely consistent in their inferred trees, and the phylogeny is in general agreement with previous studies [4,5,7,10,22,35]. The planktonic foraminifera appear polyphyletic, falling in at least 4 separate areas of the tree (Figure 2), consistent with the morphological groupings of the spinose (Globigerinidae and Hastigerinidae), non-spinose macroperforate (Globorotaliidae & Pulleniatinidae), non-spinose microperforate (Candeinidae), and the non-spiral planktonic foraminifera (see [71]).


Ecological partitioning and diversity in tropical planktonic foraminifera.

Seears HA, Darling KF, Wade CM - BMC Evol. Biol. (2012)

Bayesian inference SSU rDNA phylogenetic tree showing the position of the Arabian Sea morphospecies and genotypes within the foraminifera. The phylogeny is based on 407 unambiguously aligned nucleotide sites and is rooted on the benthic foraminifer Allogromia sp. Bayesian posterior probabilities (from the last 1000 trees, obtained within MrBayes) and ML bootstraps (expressed as a percentage, 1000 replicates) are shown on the tree (BI posterior probabilities/ML bootstraps). The scale bar corresponds to a genetic distance of 2%. Benthic foraminiferal taxa are shown in grey text, and planktonic foraminifera are shown in black. Morphospecies and genotypes found in the Arabian Sea are shown on a grey background. A star indicates a novel sequence obtained from the Arabian Sea cruise (CD148). The sequence for S. globigerus is also presented in [72].
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3361484&req=5

Figure 2: Bayesian inference SSU rDNA phylogenetic tree showing the position of the Arabian Sea morphospecies and genotypes within the foraminifera. The phylogeny is based on 407 unambiguously aligned nucleotide sites and is rooted on the benthic foraminifer Allogromia sp. Bayesian posterior probabilities (from the last 1000 trees, obtained within MrBayes) and ML bootstraps (expressed as a percentage, 1000 replicates) are shown on the tree (BI posterior probabilities/ML bootstraps). The scale bar corresponds to a genetic distance of 2%. Benthic foraminiferal taxa are shown in grey text, and planktonic foraminifera are shown in black. Morphospecies and genotypes found in the Arabian Sea are shown on a grey background. A star indicates a novel sequence obtained from the Arabian Sea cruise (CD148). The sequence for S. globigerus is also presented in [72].
Mentions: A comprehensive foraminiferal phylogeny, based on 407 bp of the SSU rRNA gene (Figure 2) highlights the placement of the Arabian Sea taxa. All methods of phylogeny reconstruction utilised were largely consistent in their inferred trees, and the phylogeny is in general agreement with previous studies [4,5,7,10,22,35]. The planktonic foraminifera appear polyphyletic, falling in at least 4 separate areas of the tree (Figure 2), consistent with the morphological groupings of the spinose (Globigerinidae and Hastigerinidae), non-spinose macroperforate (Globorotaliidae & Pulleniatinidae), non-spinose microperforate (Candeinidae), and the non-spiral planktonic foraminifera (see [71]).

Bottom Line: Sampling was conducted in the tropical Arabian Sea, during the southwest (summer) monsoon, when pronounced environmental conditions result in a strong disparity in temperature, salinity and productivity between distinct northern and southern water masses.We propose sea-surface primary productivity as the main factor driving the geographical segregation of Arabian Sea planktonic foraminifera, during the SW monsoon, with variations in symbiotic associations possibly playing a role in the specific ecological adaptations observed.Our findings suggest that ecological partitioning could be contributing to the high levels of 'cryptic' genetic diversity observed within the planktonic foraminifera, and support the view that ecological processes may play a key role in the diversification of marine pelagic organisms.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Biology, University of Nottingham, Nottingham, UK.

ABSTRACT

Background: Ecological processes are increasingly being viewed as an important mode of diversification in the marine environment, where the high dispersal potential of pelagic organisms, and a lack of absolute barriers to gene flow may limit the occurrence of allopatric speciation through vicariance. Here we focus on the potential role of ecological partitioning in the diversification of a widely distributed group of marine protists, the planktonic foraminifera. Sampling was conducted in the tropical Arabian Sea, during the southwest (summer) monsoon, when pronounced environmental conditions result in a strong disparity in temperature, salinity and productivity between distinct northern and southern water masses.

Results: We uncovered extensive genetic diversity within the Arabian Sea planktonic foraminifera, identifying 13 morphospecies, represented by 20 distinct SSU rRNA genetic types. Several morphospecies/genetic types displayed non-random biogeographical distributions, partitioning between the northern and southern water masses, giving a strong indication of independent ecological adaptations.

Conclusions: We propose sea-surface primary productivity as the main factor driving the geographical segregation of Arabian Sea planktonic foraminifera, during the SW monsoon, with variations in symbiotic associations possibly playing a role in the specific ecological adaptations observed. Our findings suggest that ecological partitioning could be contributing to the high levels of 'cryptic' genetic diversity observed within the planktonic foraminifera, and support the view that ecological processes may play a key role in the diversification of marine pelagic organisms.

Show MeSH