Fig 1.
Sampling site at Felda Gunung Besout Perak.
(A) The habitat of the study site is within oil palm blocks. (B) Brood nest collected from a palm frond in an elevated position. (C) A large brood nest was sampled and captured from a Calamansi tree orchard within a palm block.
Fig 2.
Comparison between specimens. A major worker specimen from Thailand was taken as a reference model (CASENT0173647, April Nobile) and matched with sampled individuals collected in Felda Gunung Besout plantations during this research. The measurements follow the three views shown: a frontal view (HW, red line – A), a side view (TL, yellow line, AL, red line, and BL, black line – B), and a dorsal view (C). (HL, red line – BL, black line – C). As for other measured body parts, the head section was dissected to minimize margin error occurrences (thorax and abdomen – D). Images are accessible at www.antweb.org. AntWeb. Version 8.64.2. California Academy of Science, online at https://www.antweb.org. Accessed 22 September 2021.
Fig 3.
O. smaragdina yellowish eggs clusters. (A) Separated and tallied eggs from brood nests with a glossy appearance. (B) Compact egg clusters with a micron-sized standard. Examining using Nikon SMZ800N stereomicroscope. Photo credit: Exelis Moïse Pierre.
Table 1.
Worker morphological measurements – abbreviations.
Fig 4.
Immature stage of O. smaragdina individuals.
O. smaragdina distinguished yellow eggs in black circles (A). Major (black arrow) and subordinate worker larvae (red arrow) (B). Big queen larvae (C). Male drone larva (black circle) and female queen larva (red arrow) (D). Queen (red circle) and male larvae (black circle). Major worker, intermediate 3, intermediate 2, and minor worker (yellow circle), from right to left, (E). Workers’ pupae with their distinctive sizes, from right to left: a major worker (black circle), an intermediate worker (red circle), and a minor worker (yellow circle). (F). Queen pupae (G). Identifies the distinction between eggs (black arrow) and larvae (red circle). (H). All figures scales are 1 mm—examination via Nikon SMZ800N stereomicroscope (Photo credit: Exelis Moïse Pierre).
Fig 5.
Various castes of O. smaragdina.
(A) Gravid dealate founding queen with large gaster surrounded by major workers; (B) Drone male (red circle) among major workers; (C) Winged green virgin queens & yellow callow; (D) Dealate gravid queen (red circle) & another wingless queen surrounded by major workers (yellow circle); Multiple winged queens (black circles), major workers-minor workers & larvae-pupae exhibiting a sharp white color; (E) Large major worker IV (Black circle); intermediate worker III (red circle); intermediate worker II (yellow circle) and minor worker I (blue circle). Photo Credit (Moïse Pierre Exélis).
Fig 6.
(A) Major big worker. (B) Major intermediate worker. (C) Intermediate worker 3. (D) Intermediate worker 2. (E) Minor worker. Examination by stereomicroscope Nikon SMZ800N (A-B) and ZEISS Stereo Discovery V20 microscope (C-E). The lines indicate the sizes of variables HW, HL, TL, AL, and BL. Photo Credit (Exélis Moïse Pierre).
Fig 7.
O. smaragdina worker Antennal segments.
Examination by stereomicroscope Nikon SMZ800N. Photo Credit (Exélis Moïse Pierre).
Table 2.
One-way ANOVA post-hoc Tukey HSD.
Table 3.
PCA Eigenvector proportion – variables contribution.
Table 4.
Generalized estimating equation.
Fig 8.
Box plot: Comparison of body dimensions (HW, HL, TL, BL, AL) by worker sub-caste.
Fig 9.
Kruskal-Wallis median plot. The median line plots are generated from the Kruskal-Wallis test. These plots illustrate that each sub-caste of ant workers has significantly different medians for body dimensions (HW, HL, TL, AL, BL), showing how the median of each morphological trait varies across different ant sub-castes.
Fig 10.
Correlation plot (Pearson correlation – histogram). The correlation plot illustrates the relationships between body dimensions. The corresponding correlation values quantify the strength of each relationship. The closer a value is to one, the stronger the positive relationship between the variables, namely HW, HL, TL, AL, and BL. The red spots represent the mean values.
Fig 11.
A) From the scree plot, PC1 explains the most variance (95.5%), meaning it captures most of the variation in the dataset.
PC2 explains around 2.1%, adding important but less dominant variation. PC3, PC4, and PC5 contribute much less (0.3%−1.2%), suggesting they can be ignored. B) PCA variable plots. Based on the arrows, all variables contribute almost equally to the principal components. HL, BL, and AL (in red) have high cos2 (cosine squared) values, meaning they are well-represented. HW and TL contribute less to the selected principal components. HW and TL are closely aligned, so they are highly positively correlated. The arrows are pointed to the left, which indicates that all variables (HW, HL, TL, AL, BL) have negative loadings on Principal Component 1 (PC1). Higher PC1 scores correspond to lower values of these original features (B – left). HL, BL, and AL (in red) have high contribution values influencing the components. HW and TL contribute less to the selected principal components (B – right). HW and TL are closely aligned, so they are highly positively correlated. HL, BL, and AL are positively correlated (B – left and right). C-D) Analysis plots: Biplot – PCA projection plot. Biplot: MW tends to cluster separately. MBW and MIW overlap slightly but still form distinguishable groups. Hence, PC1 and PC2 can differentiate all the ant sub-castes well. The plots (Biplot & PCA projection plot) show that the ant sub-castes are clustered and well-defined.
Fig 12.
Major and intermediate workers’ collective daily foraging activity.
Various workers are in daily activity on a palm frond: Major intermediate worker (black circle); intermediate 3 (yellow circle); intermediate 2 (red circle). Photo Credit (Exélis Moïse Pierre).
Fig 13.
Leadership and supervision activity of bigger size major workers.
Removal of intermediate workers 2 and 3 during the higher AT (°C) periods (1150 hour to 1600 hours – A - left) by the major workers. Pearson correlation significant coefficient (B - right).
Fig 14.
Correlation plot (Pearson correlation – histogram).
The correlation plot shows the relationship between the number of emerging queens, rainfall intensity (mm/h), and relative humidity (RH%). There is a strong positive correlation between the total number of queens, rainfall intensity, and humidity. As rainfall intensity and humidity increase, so does the number of queens. The red points represent the mean values.
Fig 15.
Correlation plot (Pearson correlation) of young colony (left) and old colony (right).
From Panel A–B, there is a strong positive correlation between the number of queens and males in the young colony compared to the old colony, respectively. In the young colony, as the number of queens increases, so does the number of males.
Fig 16.
Box plot of queens and males in the young colony (left) and old colony (right) A-B compares the queens and males distribution in the young and old colonies, respectively.
In the young colony, the median number of males is higher than that of queens. However, in the old colony, the median number of queens is approximately 2.5 times higher than in the young colony, while the number of males has decreased significantly.