Small-scale variations in leaf shape under anthropogenic disturbance in dioecious forest forb mercurialis perennis: A geometric morphometric examination

Abstract

Plants are exposed to increasing levels of diverse human activities that have profound effects on their overall morphology and, specifically, on leaf morphology. Anthropogenic disturbances in urban and suburban forest recreational sites are attracting growing research interest. To explore the persisting recreational impact on leaf shape and size, we conducted a field study on the dioecious forb Mercurialis perennis L. (Euphorbiaceae), typical for undisturbed understory communities. We selected adjacent sites in a suburban forest, which experience contrasting regimes of disturbance by human trampling under otherwise concordant natural conditions. Patterns of leaf shape and size variation and putative sex-specific response to disturbance were analyzed using a geometric morphometric approach. In addition to leaf-level data, plant height, internode and leaf number were analyzed to explore the same response at the whole-plant level. The results show significant variations associated with disturbance at both levels: plants growing under a heavy disturbance regime had shorter stems with a greater number of wider and shorter leaves. Significant differences between sites were also found for leaf size, with larger leaves observed in an undisturbed site. The effects of sex and sex x site interaction on leaf size and shape were nonsignificant, pointing to the absence of sexual dimorphism and sex-specific response to disturbance. Contrary to leaf shape and size, all three analyzed shoot traits showed highly significant sexual dimorphism, with male plants being higher and having higher leaf and internode count.

Light and sex interplay: Differential herbivore damage in sun and shade in dioecious Mercurialis perennis

“…In species where males exhibit greater total aboveground biomass, longer shoots and bigger leaves, these traits can make them more apparent, conferring greater susceptibility to herbivores, especially to folivores [21]. Previous research found prominent male-biased SSD in height in M. perennis populations at lower altitudes [34,52]; however, this difference tended to decrease with increasing altitude [34]. In the present study, at the upper limit of altitudinal distribution, no significant effect of sex on plant height or total leaf area was found.…”

The Effect of Informal Tourist Trails on the Abiotic Conditions and Floristic Composition of Deciduous Forest Undergrowth in an Urban Area

“…In the case of clonal plants occurring in the undergrowth, human trampling can trigger mechanical stress and reduction of sexual reproduction through damage to flowering stems and/or impact on the number and dimensions of leaves. This was observed in populations of Anemone nemorosa L. [62] and Mercurialis perennis L. [63]. Moreover, human trampling and soil digging by dogs accompanying humans can contribute to genet fragmentation and vegetative propagation of species creating thin and delicate connections between ramets such as Fragaria vesca L. [64], Maianthemum bifolium (L.) F.W.…”

Morphometrical methods as tools for identifying field maple (Acer campestre L.) trees

“…The double fan method is employed by Vujic et al. () based on two locked landmarks. Thus, the fan is adjusted in size to the leaf and a second axis is not needed.…”

“…A single fan with just one axis would not keep the same proportions and thus the semilandmarks would slide around. The double fan method is employed by Vujic et al (2016) based on two locked landmarks. Thus, the fan is adjusted in size to the leaf and a second axis is not needed.…”

“…In that sense it resembles the method of how points are distributed in Fourier analysis of shape contours. Vujic et al (2016) placed two discrete and homologous landmarks at the apex and at the petiole/blade junction of leaves of Mercurialis L. and with the double fan method eight semilandmarks were defined. In Nothofagus Blume, Premoli (1996) defined seven landmarks and semilandmarks on one side of each leaf of using the fan method.…”