Direct seeding as a recruitment alternative for the threatened tropical palm Syagrus coronata (Mart.) Beccari in Brazilian dry forest.

Habitat loss reduces biodiversity and threatens ecological services. The use of techniques for vegetation restoration such as direct seeding seems promising, mainly because it reduces costs and labor. The aim of this study was to investigate which are the main ecological filters that can inhibit the success of direct seeding, using Syagrus coronata (Mart.) Beccari (Arecaceae), a species that has great ecological and extractive importance for the Brazilian semi-arid region, and is found in habitats with different management intensities. The following hypotheses were tested: (1) managed habitat (pasture) and natural habitat (caatinga vegetation) show differences in seed fate; and (2) defleshed fruits will have greater seed germination success compared to not defleshed. Seed fate was evaluated for two consecutive years, year I (2016-2017) and year II (2017-2018). Within these years, 800 mature fruits were buried along 300 m transects, half with defleshing treatment, and monitored during 240 days. The highest seed survival occurred in year II, this result may be associated with higher rainfall recorded during the experiment, considering that there was no difference in seed germination between habitats. Defleshing facilitated germination and reduced insect predation, likely by removing invertebrate larvae before they have reached the seed. Desiccation was the major cause of mortality in the entire study and was higher in the managed habitat. Water insufficiency may have caused the deactivation of antioxidant mechanisms and affected the embryo. Although defleshing may favor germination, this procedure would not be indicated for pastures as it favors desiccation. The study showed how habitat management and fruit defleshing can affect seed fate. More studies on ecological relationships need to be carried out to increase understanding of how habitat modification affects the functioning of arid ecosystems.

Natural Vs Managed Habitat: Effect Over the Seed-Predator Pachymerus nucleorum and Its Natural Enemies.

The licuri palm, Syagrus coronata (Martius) Beccari (Arecaceae), is widely distributed throughout the Brazilian Caatinga and has high cultural, socioeconomical, and ecological importance. The palm tree logging is prohibited by the Brazilian law, and thus isolated individuals are a common sight on managed pastures in the Brazilian semi-arid region. We aimed to compare the insect seed-predator Pachymerus nucleorum (Fabricius) (Bruchinae) abundance and its predation levels on S. coronata seeds between managed (pasture) and natural (Caatinga vegetation) habitats. We also monitored the parasitoid Heterospilus prosopodis (Viereck) (Braconidae) abundance and other P. nucleorum potential natural enemies (generalist predators and microhymenopterans). We tested the hypothesis that more complex and heterogenous habitats (i.e., with higher plant diversity) support higher abundance of potential P. nucleorum natural enemies. For such, we collected 600 fruits from each habitat and evaluated the seed predation level by P. nucleorum, as well as the P. nucleorum parasitism by H. prosopodis. The P. nucleorum abundance and its potential natural enemies were estimated using 122 sticky traps placed on the S. coronata individuals' crown. Neither the P. nucleorum and generalist predators abundance differed between habitats, whereas the H. prosopodis and microhymenopterans abundance was higher in the natural habitat. Consequently, P. nucleorum parasitism levels by H. prosopodis were also higher in the natural habitat. Our study indicated that habitat with higher plant diversity supported more natural enemies, thus confirming that increased habitat homogenization leads to decreased parasitism levels by the less parasitoids number in managed habitats. Our results may subsidize conservationist management practices in the managed habitats aiming to improve fruit exploitation techniques sustainability and land-use practices, which would thereafter allow for the S. coronata population conservation in the Brazilian Caatinga.

Climate change effects on the geographic distribution of specialist tree species of the Brazilian tropical dry forests.

The aim of this study was to evaluate the ecological niche models (ENMs) for three specialist trees (Anadenanthera colubrina, Aspidosperma pyrifolium and Myracrodruon urundeuva) in seasonally dry tropical forests (SDTFs) in Brazil, considering present and future pessimist scenarios (2080) of climate change. These three species exhibit typical deciduousness and are widely distributed by SDTF in South America, being important in studies of the historical and evolutionary processes experienced by this ecosystem. The modeling of the potential geographic distribution of species was done by the method of maximum entropy (Maxent).We verified a general expansion of suitable areas for occurrence of the three species in future (c.a., 18%), although there was reduction of areas with high environmental suitability in Caatinga region. Precipitation of wettest quarter and temperature seasonality were the predictor variables that most contributed to our models. Climatic changes can provide more severe and longer dry season with increasing temperature and tree mortality in tropics. On this scenario, areas currently occupied by rainforest and savannas could become more suitable for occurrence of the SDTF specialist trees, whereas regions occupied by Caatinga could not support the future level of unsustainable (e.g., aridity). Long-term multidisciplinary studies are necessary to make reliable predictions of the plant's adaptation strategies and responses to climate changes in dry forest at community level. Based on the high deforestation rate, endemism and threat, public policies to minimize the effects of climate change on the biodiversity found within SDTFs must be undertaken rapidly.