Native ants help to spread an invasive African grass in the Cerrado

Abstract

Invasive plants often change fire regimes, nutrient cycles, and replace native species (D' Antonio & Vitousek, 1992, Mack et al. 2000, Vilá et al., 2011. Invasive success usually relies on a better performance of the invader compared with natives due to, for example, release from natural enemies and competitors (Levine et al., 2004), and fluctuations in resources that follows disturbances and that coincides with availability of propagules from invasive species (Davis et al., 2000). Establishment of mutualisms with native animals, such as pollination and seed dispersal, is also a key to invasive success (Richardson et al., 2000). As seed dispersal is important for patch colonization of plants, knowledge about dispersal of propagules is crucial to manage and control invasive species (Puth & Post, 2005).Signalgrass Urochloa decumbens (Stapf) R.D. Webster (syn.Brachiaria decumbens Stapf) is a perennial C4 African grass introduced in Brazil for cattle ranching in the 50s (Miles et al., 1996). This grass became popular and now ~45% of the Cerrado (~500,000 km²) is occupied by pastures planted with U. decumbens and other African grasses (Klink & Machado, 2005). Urochloa spp. (hereafter Urochloa) are aggressive invaders in tropical savannas and grasslands, including most of the protected areas of Cerrado (Durigan et al., 2007;

Seed ecology of post-fire flowering species from the Cerrado

“…Seeds produced after early-dry season fires will remain exposed on the soil for 3–4 months before a germination window, and the entire reproductive output could be lost if seed viability fades before the wet season. Seeds on the soil are also subjected to post-dispersal predation and removal by ants, which may reduce viability but carry seeds to further germination sites (Christianini et al, 2007; Rebolo et al, 2022). Also, the ash of early-dry season fires can be removed by wind before rains start germination (Coutinho, 1990; Castro-Neves and Miranda, 1996), suggesting that other germination stimuli may be important in these conditions.…”