Phylogenetic structure of Brazilian savannas under different fire regimes

Abstract

Questions: Fire is a strong filter in fire-prone communities and is expected to assemble closely related species when functional traits are conserved in plant lineages. Do frequent fires assemble savannas with closely related species (phylogenetic clustering)? If so, what are the clades pruned by fire in the phylogenetic trees? Are species of semi-deciduous seasonal forests, where fires are not frequent, less related than expected by chance (phylogenetic overdispersion)? Are life forms conserved in the phylogeny of the species? Location: Central and SE Brazilian savannas (Emas National Park, 18118 0 S, 52154 0 W; Brası´lia, 15156 0 -15157 0 S, 47153 0 -47156 0 W and Corumbataı´-Itirapina, 22113 0 -22115 0 S, 47137 0 -47139 0 W); and close semi-deciduous seasonal forests (in Pireno´polis, 15145 0 S, 49104 0 W; Brası´lia, 15133 0 S, 47151 0 W; and Sa˜o Carlos, 21155 0 S, 47148 0 W).Methods: We recorded woody species in savannas under different fire regimes and in semi-deciduous seasonal forests. We obtained data from the literature and from field sampling. We compared mean phylogenetic distance of species of savanna and of nearby semi-deciduous seasonal forest sites. We obtained significance by randomizing the species among the tips of phylogenetic trees. We also assessed whether life forms were evolutionary conserved across phylogeny of the studied plants (phylogenetic signal) with tests based on the variance of phylogenetic independent contrasts. Results: Some sites of savanna under high fire frequency were characterized by phylogenetic overdispersion of woody species whereas, in contrast, some sites of semi-deciduous seasonal forest were characterized by phylogenetic clustering. We found phylogenetic signals in the traits across the phylogeny of the 801 species investigated. Conclusion:Fire may have different roles in assembling plant species in Brazilian savannas than in other fire-prone communities. We postulate that the absence of phylogenetic clustering in the cerrado is mainly due to the persistence of long-lived resprouting species from different plant lineages.

Phylogeny, traits, environment, and space in cerrado plant communities at Emas National Park (Brazil)

“…On the one hand, we found a phylogenetic signal for wood density and most leaf traits; on the other hand, we did not find a phylogenetic signal in fire-related traits, such as height, basal area, and thick bark. Contrary to other fire-prone vegetation types -for example, Mediterranean vegetation (Verdú and Pausas, 2007) -in the cerrado fire does not assemble phylogenetically related species, but only phenotypically similar species (Silva and Batalha, 2010). Whereas in Mediterranean vegetation, frequent fires appeared only in the Quaternary (Verdú and Pausas, 2007), in savannas, such as the cerrado, fire became frequent about 8 million years ago (Beerling and Osborne, 2006).…”

“…Whereas in Mediterranean vegetation, frequent fires appeared only in the Quaternary (Verdú and Pausas, 2007), in savannas, such as the cerrado, fire became frequent about 8 million years ago (Beerling and Osborne, 2006). Thus, there was enough time for multiple colonizations of the cerrado by phylogenetically distant lineages (Silva and Batalha, 2010). Indeed, fire-related traits in the cerrado are not exclusive to specific families or older clades (Simon et al, 2009).…”

“…Even if there are studies on environmental filtering (for example, Silva and Batalha, 2010), phylogenetic (for example, Silva and Batalha, 2011), and spatial signals (for example, Ferreira et al, 2007) in cerrado plant communities, an analysis combining all these aspects does, to the best of our knowledge, not yet exist. We used a new framework to analyze environmental filtering in the geographic and phylogenetic context (Pavoine et al, 2011), sampling woody species in one of the largest cerrado reserves.…”

Determinants of flammability in savanna grass species

“…). Different fire regimes can lead to the assembly of distinct populations and communities that are functionally clustered for diverse traits (Pausas & Bradstock ; Verdú & Pausas ; Silva & Batalha ; Forrestel, Donoghue & Smith ). For example, resprouting species are favoured in frequent, low‐intensity fire regimes, and obligate seeders that persist via seedling recruitment are favoured in infrequent, high‐intensity fire regimes (Pausas & Bradstock ; Pausas & Keeley ).…”

Effect of Fire on Ant Assemblages in Brazilian Cerrado in Areas containing Vereda Wetlands

“…The vegetation has several adaptations to fire, such as the possession of thick rhytidome, and xylopodium, tubers, bulbs, corms and underground rhizomes, which assist plants to survive the fire (Bond & Keeley, 2005;Silva & Batalha, 2010). The species of ants with colonies no deeper than 5 cm in the soil have lower chances of surviving fire, due to exposure to flames and associated high temperatures (Castanheira de Morais & Benson, 1988), which may range from 85°C to 840°C in the air, and 29°C to 55°C in the ground at 1 cm depth.…”