# Supplementary Table S1. Ceroxyloideae WGS tBLASTn Hit Statistics

## A. Query Set

| Query type | Count | Source |
|:--------|-----:|:------|
| Palm PEPC queries | 65 | 13 palm species, all five subfamilies |
| C4-type PEPC1 (maize) | 1 | UniProt P04711 |
| C3-type PEPC2 (maize) | 1 | NP_001105438 |
| C3-type PEPC1 (rice) | 1 | Q6AVA8 |
| C3-type PEPC (Arabidopsis) | 2 | Q9MAH0, Q9SJG9 |
| **Total queries** | **70** | |

## B. Ravenea rivularis (SRR15672934, ~1.3× coverage)

| Metric | Value |
|:-------|:------|
| Total paired-end reads | 20,942,500 |
| Reads screened | 10,000,000 |
| Total tBLASTn hits (E < 10⁻⁵) | 28,537 |
| Unique PEPC-positive reads | 700 |
| Reads matching ≥1 reference query | 62 |
| Cross-reactive reads (match all 5 references) | 45 (72.6%) |
| Reads matching only maize PEPC1 | 5 |
| — Alignment length range | 23–33 aa |
| — E-value range | 1×10⁻⁶–5×10⁻⁶ |
| — Below PEPC domain threshold (≥100 aa, E < 10⁻¹⁰) | 5/5 |
| — Cover Ser774 motif (C4 determinant) | 0/5 |

## C. Pseudophoenix vinifera (ERR9229902, ~0.2× coverage)

| Metric | Value |
|:-------|:------|
| Total paired-end reads | 1,568,224 |
| Reads screened | 1,568,224 |
| PEPC-positive reads | Confirmed |
| C4-type PEPC1 detected | None |
| Pattern | Identical to R. rivularis |

## D. E-value Stratification (R. rivularis)

| E-value range | Hit count | Proportion |
|:------------|--------:|-------:|
| < 1×10⁻²⁰ | 21,830 | 76.5% |
| 1×10⁻²⁰–1×10⁻¹⁰ | 5,142 | 18.0% |
| 1×10⁻¹⁰–1×10⁻⁵ | 1,565 | 5.5% |
| **Total** | **28,537** | **100%** |

## E. Interpretation

The five maize-PEPC1-only reads (23–33 aa, E > 10⁻⁶) represent non-functional alignments
to the broadly conserved PEPC catalytic domain. They fail to:
- Meet the PEPC domain identification threshold (≥100 aa, E < 10⁻¹⁰)
- Cover the C4-specific Ser774 phosphorylation motif
- Show enrichment beyond background cross-reactivity (72.6% of PEPC-positive reads
  hit all five reference queries simultaneously)

Conclusion: Both Ceroxyloideae species harbor PEPC but lack C4-type PEPC1.