Fig 1.
(A) Locations of the samples analyzed in the study. Each symbol corresponds to a scientific cruise or near shore collection site. Cruise names are indicated in the legend. The background color represent the annual sea surface temperature extracted from the World Ocean Atlas [105]. (B) Sampling coverage of the five species of the genus Globigerinoides. The colors in the background represent the relative abundance in sediments extracted from the FORCENS database [106]. Note that G. ruber albus n.subsp. and G. elongatus have the same map because they usually were not be discriminated in micropaleontological studies. The maps were generated using Ocean Data View [107].
Fig 2.
Molecular taxonomy of the genus Globigerinoides.
Each branch represents a unique basetype, the symbol next to the branch represent the individual basegroup and the colors represent unique morphospecies. The first set of rectangles represent the three automated delimitation proposed by ABGD and PTP. The coarsest partition is retained as Lineage (MOTUs level-1) and encircled with a solid line, the finest partition is retained as Genotype (MOTUs level-2) and encircled in dotted line. The resulting 3-rank molecular taxonomy is showed in the second set of rectangles.
Fig 3.
Development and consistency across the nomenclatural scheme proposed for the genus Globigerinoides.
The Sankey diagram indicates the change in the names, addition of new taxa, lumping and splitting of existing units across the successive studies. The change of colors indicates when formal taxonomic revisions were made.
Fig 4.
Biogeographic distribution of constitutive genotypes (MOTUs lvl-2) and basegroups (MOTUs lvl-3) of the genus Globigerinoides in the sample set.
(A) The circles indicate where the genotypes have been collected and are filled when the basegroup has been identified in the sample. Note that the coverage for G. conglobatus and G. tenellus is insufficient for robust interpretation. The maps were generated using Ocean Data View [107]. (B) Windrose diagram showing the month of collection of each genotype and basegroup. The month of collection have been normalized in regard to hemisphere.
Fig 5.
Assessment of species richness.
Rarefaction curves for the different basins and the entire dataset at the genotype (MOTUs lvl-2) and basegroup (MOTUs lvl-3) levels, and for all morphospecies together and for the better sampled G. ruber and G. elongatus only.
Table 1.
Results of the Jackknifing analyses that provide the comparison between the observed diversity (So) and the estimated basegroup diversity (Se) for G. ruber and G. elongatus basegroup at global and basins scales.
Note that the entire diversity of G. ruber and G. elongatus may not have been entirely captured in the Atlantic Ocean and the Indian Ocean respectively because So does not fall into the 95% confidence interval (CI95).
Fig 6.
Distribution of the monthly values of Sea Surface Temperature (SST), Mixed Layer Salinity (MLS), Chlorophyll (CHL), Particulate Organic Carbon (POC) and Productivity (Prod), observed for the morphospecies, genotypes and basegroups of G. elongatus, G. ruber albus n.subsp. and G. ruber ruber. The statistical tests to compare the distribution are provided in Table 2. The box plot were generated with R [108] using the ggplot2 package [109].
Table 2.
Results of Mann-Whitney tests for environmental parameters comparisons.
The significant values are shown in bold.
Fig 7.
Molecular clock estimates of the diversification of the Globigerinoides genus rooted on Globoturborotalita rubescens.
The grey bars indicate the uncertainties in the dating of the node and the stars indicate the nodes used for calibration (See text for details).
Fig 8.
CT- scans of external morphology of representative specimens of the five species in four standard views for (1) G. conglobatus, (2) G. ruber, (3) G. elongatus, (4) G. tenellus and (5) G. rubescens. The scaling of the species respects the difference in sizes.
Fig 9.
Ontogenetic development of the five selected morphospecies.
(A) The addition of individual chambers is shown with segmentation of the inner volume from the proloculus to the final chamber. To accommodate the difference in size during the ontogeny and between the species, we have decreased the relative size of the successive stage by 10% and provide scale bars at the beginning, middle and end of their ontogeny for reference. (B) Relative proportions of the total inner volume occupied by each chamber. Color coding of the chamber is the same as in (A) with indication of the transition between the successive ontogenetic stages marked colored lines (See main text for details). The dotted lines indicate when the exact transition between stages is uncertain.
Fig 10.
The scheme on the left represents the position of the centroids of the chambers in G. conglobatus in 3D space. The z-axis is given by the coiling axis of the specimen. The radius r (distance between the coiling axis and the centroid of a given chamber), the height z (distance between the centroids of the proloculus and a given chamber along the coiling axis) and the angle α (measured between the radii of two successive chambers) are illustrated on the scheme. The segmentation of the inner volume of the last chamber is given in the right bottom corner of the scheme together with the biometric measures H (Height of the chamber) and L (Length of the chamber). The equations of the parameters of the Raup model are provided next to the graph (See explanation in the main text). The six panels on the right show the results for the Raup parameters for each chamber of each specimen together with the cumulative volume and the whorl number. The results of the measurements and calculation of the Raup parameters are provided in the S3 Table.
Fig 11.
Cladogram representing the morphological evolution of the Genus Globigerinoides.
The cladogram (A) represents the retained scenario and the cladograms (B) and (C) possible but rejected alternatives. (A) The presence of supplementary apertures and compressed last chambers are synapomorphies of the genus. The last compressed chamber is lost in G. ruber and G. tenellus through neoteny and progenesis respectively. The pink coloration in G. rubescens and G. ruber ruber is a homoplasic character that appear independently during the evolution of the two species. (B) Alternative scenario where the pink coloration is a synapormophic character of the Globoturborotalita and Globigerinoides genus but lost in G. ruber albus n.subsp. and by the common ancestor of G. conglobatus, G. elongatus and G. tenellus. Although we cannot with certainty choose between the scenario (A) and (B) regarding the pink coloration because the character is not preserved in sediments before 750 ka [6], we prefer the scenario (A) due to its higher parsimony. (C) Alternative scenario where the last compressed chamber is not a synapomorphic character but acquired only in the monophylum G. conglobatus, G. elongatus and G. tenellus and lost by G. tenellus. We do not retain this scenario because Globigerinoides obliquus, the likely common ancestor of the modern species shows high compression in its last chamber [27].