Quesada Álvaro, Hernández Fernández Manuel, Menéndez Iris
Departamento de Geodinámica, Estratigrafía y Paleontología, Facultad de Ciencias Geológicas, Universidad Complutense de Madrid, C/ José Antonio Nováis 2, 28040, Madrid, Spain.
Departamento de Cambio Medioambiental, Instituto de Geociencias (UCM, CSIC), C/ Severo Ochoa 7, 28040, Madrid, Spain.
Front Zool. 2025 Mar 11;22(1):5. doi: 10.1186/s12983-025-00556-4.
Species richness increases gradually as latitude decreases, however, the explanation for this phenomenon remains unclear. Ecological hypotheses suggest that greater niche diversity in tropical biomes may facilitate the coexistence of a larger number of species. The close relationship between species morphology and ecology can lead to a greater morphological disparity in tropical biomes.
In this study, we used 2D geometric morphometric techniques on the ventral view of the cranium of flying squirrels (Pteromyini, Sciuridae) to determine the relationship between diet and cranial morphology and to evaluate if morphological disparity is higher in tropical biomes.
The results show that diet has a significant impact on cranial shape and size, with large, wide and robust crania in folivorous and generalist species, while frugivorous species tend towards smaller and narrower crania, and nucivorous have a wide variability. This suggests that biomes with more available dietary niches would show greater morphological disparity. However, we found no statistical differences in shape and size disparity among biomes or between observed and simulated disparity based on species richness.
Our results show that there are not disparity differences between tropical and temperate biomes, even when temperate biomes are less rich than tropical ones, suggesting that the quantity of available niches may not be the key factor in generating morphological disparity. Instead, it could be the presence of extreme niches that demand specialised adaptations for exploitation, which might be of greater significance. A greater importance of size-changing adaptations would decrease shape disparity in biomes with many niches.
物种丰富度随着纬度降低而逐渐增加，然而，这一现象的解释仍不明确。生态学假说认为，热带生物群落中更大的生态位多样性可能促进更多物种的共存。物种形态与生态之间的密切关系可能导致热带生物群落中更大的形态差异。
在本研究中，我们对松鼠科鼯鼠族（Pteromyini）颅骨的腹视图采用二维几何形态测量技术，以确定饮食与颅骨形态之间的关系，并评估热带生物群落中的形态差异是否更高。
结果表明，饮食对颅骨形状和大小有显著影响，食叶和杂食性物种的颅骨大、宽且粗壮，而食果性物种的颅骨往往较小且较窄，食坚果性物种的颅骨变异较大。这表明具有更多可用饮食生态位的生物群落将表现出更大的形态差异。然而，我们发现不同生物群落之间或基于物种丰富度的观察到的差异与模拟差异之间在形状和大小差异上没有统计学差异。
我们的结果表明，即使温带生物群落的物种丰富度低于热带生物群落，热带和温带生物群落之间也不存在差异，这表明可用生态位的数量可能不是产生形态差异的关键因素。相反，可能是极端生态位的存在需要专门的适应来进行利用，这可能具有更大的意义。在具有许多生态位的生物群落中，大小变化适应的重要性增加会降低形状差异。
