Jaume, D. Pelliza, Y.I., Tadey, M. y Souto C. P. 2021. Livestock can affect the evolutionary potential of native plant species in the Monte Desert. SBE meeting: The Research of Biodiversity and the Diversity of Researchers".

DAIANA JAUME; IVÓN Y. PELLIZA; TADEY, M.; SOUTO C.P.

Congreso; SBE meeting: The Research of Biodiversity and the Diversity of Researchers". I; 2021

Understanding the dynamics across genetic, ecological and evolutionary processes that result from anthropogenic disturbances will allow management and conservation strategies to be developed to maintain biodiversity, especially in drylands susceptible to desertification. The long-term exotic livestock introduction into arid and semi-arid systems may have unpredictable evolutionary consequences on the dynamics, functioning and stability of plant communities and their future generations. Our hypothesis establishes that the introduction of exotic livestock will decrease the genetic diversity of native vegetation by removing individuals or reproductive parts of them, either by consumption or browsing. We expect to find lower genetic variability in rangeland with high stocking level in comparison to a low one. In addition, we expect that damage by livestock will also negatively affect the genetic variability of the progeny. Moreover, a decrease in genetic diversity will have consequences on the fitness and reproductive success of the plants. We expected that a decrease in genetic diversity would be related to a decrease in cover¸ fitness parameters and associated reproductive traits, such as viable seed weight . For this, leaves and seeds of A. lampa were collected from two desert rangelands of the Patagonian Monte Desert with different stocking levels (high and low). In addition, in each rangeland, fitness parameters such as parental size and reproduction were recorded and under common greenhouse conditions, offspring vigor parameters were estimated. Genetic parameters were estimated using microsatellite markers. We found significantly higher average individual heterozygosity and allelic diversity at low stocking level than at high stocking level (all < P = 0.05). For parental plants, marginally higher average viable seed weight were found at low stocking level than at high stocking level (P = 0.062), while viable seed values were found to be higher at high stocking level than at low stocking level (P = 0.017). Offspring height rate was significantly higher in rangelands with low stocking level than in high stocking level (P = 0.021). Furthermore, the increase in allelic diversity led to a marginal increase in parental viable seed weight and offspring number of branches (all ~ P = 0.06). A significant decrease in parental height and diameter was observed in response to increased browsing (all P < 0.05); at the same time, this increase stocking caused in the offspring generation, a significant decrease in the average number of leaves, branches and their volume rate (all P < 0.05). In addition, as plant cover increased, parental individual heterozygosity increased (P = 0.01) and offspring branches number and volume rate also increased (all P < 0.05). Finally, parental generation at the high stocking level was found to exhibit a significant excess of heterozygosity, indicating a recent bottleneck in this rangeland. Thus, the importance of genetic diversity for the maintenance of the species evolutionary potential across generations is highlighted. The recent bottleneck, the decrease in the genetic diversity as well as the decrease in the land cover, evidences a decrease in the population size, not only of the study species, but also in the associated plant community of the Monte Desert, principally as a consequence of the livestock activity developed in the area.