Biotic and Abiotic Interactions Shape Seed Germination of a Fire-Prone Species

Abstract

Both biotic and abiotic environmental filters drive the occurrence, distribution, and persistence of plant species. Amongst drivers that influence the distribution of plants in harsh environments, seed predation and temperature are particularly important in habitats that are prone to fire. In this study, we highlight the combined effects of predation and high temperature simulating fire to understand its effects on the germination percentage and germination speed of the fire prone species Copaifera oblongifolia. Groups of seeds attacked by the beetles Rhinochenus brevicollis and Apion sp., seeds manipulated by the ant Atta laevigata, and seeds left intact were put to germinate in controlled environments. To evaluate the effects of abiotic filters, seeds with intact elaiosomes and seeds with elaiosomes removed by the ant Atta laevigata were exposed to temperatures of 27, 60, 100, and 200 °C. The results showed that only 2.8% of the seeds attacked by R. brevicollis germinated. Seeds attacked by Apion sp. germinated faster, followed by seeds with their elaiosomes removed and seeds with intact elaiosomes. Seeds attacked by Apion sp. had the lowest germination percentage. The temperature of 200 °C killed seed embryos, whereas seeds exposed to 100 °C took longer to germinate than seeds exposed to other temperatures. Our results reveal that fire intensity and seed damage are important drivers of seed germination of C. oblongifolia.

Seed germination of a myrmecochorous plant endemic to the Brazilian semiarid region: the wolf is not so bad

“…Fruit dehiscence occurs from January to March, when they expose a shiny black and rigid seed coat partially covered by an orange elaiosome. The elaiosome is rich in lipids, carbohydrates and proteins and serves as a direct or indirect food resource for various animals, including mammals, birds and ants Fagundes et al 2021). Ants of the genera Atta and Acromyrmex are mainly characterized by the habit of collecting and transporting plant material through trails into their nests to cultivate fungi that constitute their basic food resource (Holldobler & Wilson, 1990).…”

“…For example, some myrmecochorous plants produce seeds with an elaiosome, an appendage rich in lipids, proteins, sugars and minerals that can be used directly or indirectly by different ant species as a food resource (Giladi 2006;Fernandes et al 2018). In return, many ant species transport seeds with elaiosome to their nests, thus acting as important seed dispersing vectors Fagundes et al 2021) with positive effects on the organization of plant communities in different environments (Nathan & Muller-Landau 2000;Levine & Murrell 2003;Lengyel et al 2009;Snell et al 2019). Myrmecochory is traditionally seen as a diffuse mutualism in which several ant species can participate in seed dispersal of the same plant species (Ness et al 2004;.…”

“…In fact, the presence of an elaiosome can affect seed germinability because these appendages have germinationinhibiting substances, or simply because they negatively affect seed imbibition (Fernandes et al 2018). Thus, the simple removal of these appendages by dispersers could break seed dormancy and accelerate germination (Souza et al 2015b;Fagundes et al 2021). Seed manipulation by ants can also cause grooves in the seed coat, which favors water absorption and germination (Prior et al 2014).…”

“…These ants collect the seeds of plants and transport them to inside their nests, where they remove the elaiosomes and use them to grow fungi, which is their main food resource. After the elaiosomes are removed, the ants discard these seeds close to the loose soil of the anthill Fagundes et al 2021). Several other animals, such as birds and mammals, also use the elaiosome of Copaifera seeds as a food resource (Rabello et al 2010;Souza et al 2015a;).…”

“…Here we evaluate the role of two potential dispersers (Atta laevigata: Formicidae and Chrysocyon brachyurus: Carnivora: Canidae) on the germinability of C. arenicola seeds. We work with these two seed vectors of C. arenicola seeds as they occur naturally in our study area, have overlapping and widespread distribution in others regions of the Brazilian semi-arid as Cerrado and Caatinga, and seed vectors have distinct behavior that can impact differently seed distribution patterns in the landscape (Bueno et al 2002;Melo et al 2007;Fagundes et al 2021). Specifically, we tested the hypothesis that seeds ant-manipulated and seeds ingested by maned wolf present greater germinability than seeds hand-manipulated and intact seeds (i.e.…”