## 3 Results
### Ontogenetic Allometric Trajectories  
We found a positive correlation between RW1 and log centroid size in the regression analysis for both morphs in the two systems (Table 2, Figure 4A,B). This indicates that specimens with a longer premaxilla also had a sharper angle and narrower ascending processes. For RW2, only the regression analysis for the deep-body morph from the San Juan River system showed a positive association with log centroid size (Table 2, Figure 4C,D). In this case, as the log centroid size increases, fish showed narrower premaxilla and longer ascending processes (Figure 4D).  
Figure 3: Differences in the consensus shape of premaxilla between morphs for (**A**) Lake Catemaco and (**B**) San Juan River systems. Gray dots in the shapes in (**A**,**B**) represent the deep-body morph used for reference; change vectors in black show the deformations toward the sympatric elongate-body morph. Examples of premaxilla of the elongate-body morph for (**C**) Lake Catemaco and (**D**) San Juan River systems.  
In the late ontogenetic allometric trajectories analysis of the shape of premaxilla for RW1, we found differences between morphs in both systems as revealed by the ANCOVAs (morph term, Table 3). We found differences in the slopes (indicating different direction of allometric trajectories) between morphs in the San Juan system, while in Lake Catemaco, the slopes did not differ statistically, suggesting parallel allometric trajectories (interaction term morph*log Centroid, Table 3). The elongate-body morph showed a parallel pattern of an extended ontogenetic trajectory when compared with its sympatric deep-body morph in both systems (Figure 4A,B). However, in the San Juan River system, the elongate-body morph showed a steeper slope (Figure 4B, Table 2). For the RW2, allometric trajectories of the shape of premaxilla showed contrasting patterns between systems. In the ANCOVA for the Lake Catemaco system, no factor showed a significant effect (Table 3), and there was no difference between morphs and premaxilla shape in relation to size (Figure 4C). Morphs  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**System/Morph**} & \multicolumn{3}{c}{**RW1**} & \multicolumn{3}{c}{**RW2**} \\ \cline{2-7}  & **Slope** & **R2** & **_p_ & **Slope** & **R2** & **_p_ \\ \hline Lake Catemaco & & & & & & \\ Deep-body & 0.19 & 0.13 & **0.02** & 0.03 & 0.004 & 0.69 \\ Elongate-body & 0.33 & 0.26 & **0.001** & 0.00001 & \textless{}0.001 & 0.99 \\ \hline San Juan River & & & & & & \\ Deep-body & 0.17 & 0.09 & **0.002** & 0.21 & 0.09 & **0.003** \\ Elongate-body & 0.42 & 0.52 & **\textless{}0.001** & 0.004 & \textless{}0.001 & 0.94 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Regression analysis for RW1 and RW2 on log centroid size for Lake Catemaco and San Juan River systems. Bold \(p\) values indicate statistically significant results.  
Figure 4: Late allometric ontogenetic trajectories of the shape of premaxilla. RW1 and RW2 on log centroid size for (**A**,**C**) Lake Catemaco system and (**B**,**D**) San Juan River system by morph. Deformation grids on the left show shape variation along RW1 (_Y_ axis) in (**A**,**B**), and RW2 (_Y_ axis) in (**C**,**D**).  
from the San Juan River system showed convergent allometric trajectories for RW2. In the ANCOVA, we found differences in the shape of premaxilla (RW2) between morphs and found differences in slopes (interaction Morpho*log Centroid size was significant, Table 3). As the centroid size increased, the shapes of the premaxilla of both morphs became more similar (Figure 4D).