Morphological measurements of the Pheidole worker caste in tropical ant communities of Southern Vietnam
Description
Morphological differences and size variations among the worker castes of Pheidole ants are adaptive responses to the ecological niches they occupy in various tropical forest types in southern Vietnam. The use of different morphological traits for size differentiation between minor and major workers is driven by their specialized functions within the colony. This dataset contains detailed morphological data measured from different species of Pheidole ants, focusing on the worker caste within tropical communities of southern Vietnam. The dataset includes measurements of five key morphological traits aimed at evaluating morphological diversity and size differentiation between minor and major workers. The dataset presents the following information: species names, morphological measurements (HL - head length, HW - head width, WL - Weber's length, EL - eye length, HTL - hind tibia length), worker caste - minor/major.
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Principal Component Analysis (PCA) was employed to compare the morphological traits across different worker subcastes of Pheidole ants. Given that the data did not follow a normal distribution (with the exception of Weber’s length), standardized traits were utilized in the analysis: relative head length (HL/WL), relative head width (HW/WL), relative eye size (EL/HW), and relative length of the hind tibia (HTL/WL). PCA was conducted for each model plot and for the complete species set. The morphofunctional trait space was analyzed using a two-dimensional probability distribution density function, with the X and Y axes representing the first two principal component axes. This resulted in a two-dimensional space that included density contours and a set of density levels, indicating areas where density values exceeded or matched certain thresholds (Chen et al., 2015, 2017). Size Differentiation Analysis: This analysis was performed separately for different subcastes. The first step involved a correlation analysis using either Pearson’s or Kendall’s coefficients, based on the data distribution type. This analysis explored the relationship between Weber’s length and head size (indicators of overall body size) at the subcaste level, with head size calculated as the arithmetic mean of head length and width. Average trait values for each species were used to identify patterns between Weber’s length and head size across subcastes. In the second stage, a detailed size differentiation analysis was conducted utilizing a probability distribution density model (KDE) for continuous variables. The KDE function is effective for determining the width of an ecological niche (Blonder, 2017). The method involves fitting a model curve that corresponds to a Gaussian distribution, with the X-axis representing the studied trait and the Y-axis indicating the probability of an individual falling within the trait range. Steps equal to 1/10 of the trait range were initially used for detailed comparisons, followed by 1/20 and 1/40, enabling precise identification of size differences between species. Data analysis and visualization were performed using R software (R Core Team, 2024) with the vegan package (Oksanen, 2011, 2015).